Non-infectious Disorders Flashcards
5 pulmonary complications of trauma
- Rib fractures and flail chest
- Traumatic pneumothorax
- Hemothorax
- Tracheobronchial trauma
- Pulmonary compression injury
- Post traumatic atelectasis
What is one of the most common consequences of thoracic trauma?
Pneumothorax
How much blood is too much blood from a chest tube?
> 1mL/kg/min
Treatment for post traumatic atelectasis
- Frequent postural changes
- Insistence on coughing
- Humidified oxygen
- Antibiotics
- Mechanical Ventilation
- Diuretics
- Cautious hydration
Most common finding of drowning (with water in the lung)
Reactive edema with hyperinflation and increased lung weight (emphysema acquosum)
With drowning, where does most of the pulmonary injury come from?
Pulmonary — Fluid aspiration results in varying degrees of hypoxemia. Both salt water and fresh water wash out surfactant, often producing noncardiogenic pulmonary edema and the acute respiratory distress syndrome (ARDS). Pulmonary insufficiency can develop insidiously or rapidly; signs and symptoms include shortness of breath, crackles, and wheezing. The chest radiograph or computed tomography at presentation can vary from normal to localized, perihilar, or diffuse pulmonary edema.
Postobstructive pulmonary edema following laryngospasm and hypoxic neuronal injury with resultant neurogenic pulmonary edema may also occur. ARDS from altered surfactant effect and neurogenic pulmonary edema often complicate management.
Inflammatory reactions secondary to brain asphyxia (as opposed to actual water aspiration)–old answer
Consequences of water aspiration
- Infection
- Surfactant depletion
- Aspiration of debris
- Fluid shifts
Why is compliance reduced in ARDS?
- Reduced surfactant
- Pulmonary edema
- Atelectasis
Mechanism of ARDS
Endothelial and epithelial disruption leading to increased alveolar-capillary permeability and flooding of the alveoli with protein-rich edema
- *disrupted surfactant
- *triggered by direct or indirect lung injury
Differences between direct and indirect ARDS
Direct (Indirect)
- Consolidation (atelectasis)
- Epithelial injury and alveolar edema ( endothelial injury and interstitial edema)
- reduced lung compliance (reduced chest wall complaince)
Duchenne muscular dystrophy: Indications for cough assist?
- Resp infection present and baseline peak cough flow <270 lpm
- Baseline peak cough flow <160 lpm or max expiratory pressure <40
- Baseline FEV1 <40% OR 1.25L
(Normal MEP is 80-120 cm H2O)
Duchenne muscular dystrophy: Indications for nocturnal ventilation?
- Signs and symptoms of hypoventilation
- Baseline SpO2 <95% or blood/end-tidal CO2 >45 while awake
- AHI >10 on PSG or >4 SpO2 <92% or drops in SpO2 of at least 4%/hr during sleep
Complications of NIV
- Eye irritation
- Conjunctivitis
- Skin ulceration
- Gastric distension
- Emesis and aspiration with full face mask
- Vent dyssynchrony
Duchenne muscular dystrophy: criteria for daytime ventilation?
(in patients already on nocturnal ventilation)
- Self extension of nocturnal ventilation into waking hours
- Abnormal swallowing due to dyspnea relieved with ventilator assistance
- Inability to speak a full sentence without breathlessness
- Symptoms of hypoventilation <95% or end tidal CO2 >45 while awake
Duchenne muscular dystrophy: Indications for trach?
- Patient/family preference
- Cannot tolerate NIV
- Medical infrastructure can’t support NIV
- 3 failures to achieve extubation despite NIV and cough assist
- Failure of non-invasive cough assist to prevent aspiration of secretions
How does high frequency oscillation work?
- Uses low tidal volumes and constant mean airway pressure with high respiratory rates
- Avoid cyclical application of high distending pressure and associated cyclical delivery of large tidal volumes to keep alveoli open and recruited with minimal lung damage
When is high frequency oscillation generally considered?
Inadequate oxygenation and/or significant hypercarbia despite plateau pressure 30-32 and FiO2 >0.6
Contraindications and hazards with high frequency oscillation
- Increased intrathoracic pressure
- Pneumothorax
- Bronchospasm
- Airway Obstruction
- Pneumomediastinum
- Subcutaneous emphysema
- Multiple organ failure
- IVH
- Refractory acidosis
Increased CO2 on high frequency oscillation, what settings to change?
1) Decrease Frequency
2) Increase Amplitude
3) Increase I:E ratio
Consequences of pectus excavatum
- Restrictive symptoms and exercise limitation
- Severe = compression and displacement of the heart with restriction of RV filling during diastole
Surgical procedures for pectus excavatum
Ravitch (costochondral osteotomy)
Nuss (retrosternal placement of metal bar)
How do you measure severity of pectus excavatum?
Pectus severity index (Haller index)
Ratio of lateral diameter of chest to the sternum-to-spine distance at point of max decompression
Normal = <2.5
Surgery candidate ≥3.25
How does flail chest affect respiration?
The unsupported area of the chest moves inward with inspiration and outward with expiration
Cause of recurrent respiratory papillomatosis
HPV 6 and 11
Most common location of recurrent respiratory papillomatosis
Larynx
High risk factors for spread of recurrent respiratory papillomatosis below upper airway (4)
1) HPV 11
2) Age <3
3) Trach
4) previous invasive procedure
Clinical triad of recurrent respiratory papillomatosis
1) Progressive hoarseness
2) Stridor
3) Breathing difficulty
Recurrent respiratory papillomatosis: most reliable test for diagnosis and typical appearance
Bronchoscopy
white polypoid lesions with clean, smooth surface
Recurrent respiratory papillomatosis: mainstay of treatment and adjuncts
Mainstay = surgical excision Adjuncts = interferon, antivirals, retinoids, inhibitors of oxygenase-2 cycle
Recurrent respiratory papillomatosis: Criteria for Adjuvant therapy
1) >4 surgical procedures per year
2) rapid recurrence with airway compromise
3) distal multisite spread
What is methemoglobin?
Altered state of hemoglobin where ferrous irons of heme are oxidized to ferric state and are unable to reversibly bind oxygen
** left shift of the curve
Why is sat monitoring inaccurate for methemoglobin?
Methemoglobin absords light at 2 wavelengths - the high concentration of methemoglobin causes O2 sat to display 85% regardless of true saturations
*blood gas will give falsely high level of O2 sat
Minimum peak cough flow for healthy person and minimum cough flow for an effective cough
Peak cough >360-400 l/min for healthy person
Minimum = >270 l/min
3 ways to increase peak cough flow
1) Air stacking/volume recruitment
2) Chest compression
3) Mechanical insufflation/exsufflation
Criteria for pediatrics ARDS
1) Exclude patients with perinatal lung disease
2) Within 7 days of known insult
3) Respiratory failure not explained by cardiac failure or fluid overload
4) Imaging findings of new infiltrates
5) classified as mild, moderate, severe using OI and OSI
4 stages of ARDS
1) Exudative
2) Fibroproliferative
3) Fibrosis
4) Recovery
What are the protective ventilator strategies for ARDS?
- lower tidal volumes
- lower plateau pressure
- higher PEEP
- lower delta P
- lower FiO2
- lower PaO2, lower pH, higher PaCO2 goals
Disease mechanism in hydrocarbon ingestion/aspiration
- Low surface tension, low viscosity, high volatility
- Allows it to spread easily and more readily into distal airspaces
- Increased surface tension by inhibiting surfactant
- Volatility allows it to spread rapidly to alveoli and interfere with gas exchange
**worry about severe pneumonitis
Pathologic findings of hydrocarbon aspiration
- Necrosis of bronchial, bronchiolar, and alveolar tissue
- Atelectasis
- Interstitial inflammation
- Hemorrhagic pulmonary edema
- Vascular thrombosis
- Necrotizing bronchopneumonia
- Hyaline membrane formation
- Alveolitis
Define hysteresis
- Different pressure/volume curves for inflation and deflation
- Less compliant with inflation (same pressure, lower volume)
- Less expected pressure for deflation
- Inflation -> with expansion of the alveoli, surfactant concentration decreases so more unopposed surface tension
Most important factor for hysteresis
Changes in surfactant activity (greater surface tension during inspiration)
Others: Stress relaxation, redistribution of gas, recruitment of alveoli
Abnormalities in scoliosis causing low volumes + low MIP/MEP on PFT
- Stiff, less compliant chest wall
- Decreased lung growth
- Decreased respiratory muscle strength (because of how they’re connected)
PFT abnormalities with scoliosis
- Severe: restrictive with low TLC (low FVC proportional to low TLC)
- *Important to compare volumes pre and post op
- Greater angle of curve = greater decrease in FVC
- Decrease MIP (correlates with decreased FVC) *check pre-op
- Decreased expiratory flow
- Normal FEV1/FVC ratio
- Lower airway obstruction may be seen
Effect of scoliosis surgery on lung function
- Improved lung volume
- no change in lung function
- no change in vital capacity
- increased residual volume
Management of adolescent idiopathic scoliosis
- <25 + low risk of progression = monitor
- <25 + progression = bracing; if progression with bracing = surgery
- > 50 = surgery
Scoliosis: why increased RV/TLC?
Normal residual volumes + FRC so increased because TLC is decreased
What is paradoxical breathing?
Occurs with neuromuscular weakness - chest wall and abdomen move in opposite directions
DMD: diaphragm weak compared to intercostals = outward chest and inward abdomen with inspiration, FVC and MIPS more affected than MEPS
SMA: Intercostal weakness with diaphragm sparing = inward chest and outward abdomen (chest sucked in due to diaphragm)
Long term effects on the lung from hydrocarbon aspiration
1) Residual injury to the peripheral airways
2) Small airway obstruction and gas trapping = decreased FEV1 and increased RV/TLC
BiPAP and not tolerating it - what are the causes?
Blowing into the eyes Poor mask and headgear fit High leak Inappropriate settings Not desensitized to mask Poor sensing - dyssynchony Lack of humidification
5 criteria for pediatric ARDS
1) Exclude patients with perinatal lung disease
2) Within 7 days of known clinical insult
3) Respiratory failure not fully explained by cardiac failure or fluid overload
4) Chest imaging findings of new infiltrates consistent with acute pulmonary parenchymal disease
5) Oxygenation (severity): CPAP >5, OI ≥ 4
Pneumothorax - when can you fly after radiographic resolution?
(BTS): complete resolution and then minimum 7 days prior to flying Underlying conditions (ie. CF) and pneumomediastinum = 2 weeks
4 chemical biomarkers of Chylothorax
Triglycerides >1.1 mmol/dl
Total count >1000 cells;>80% lymphocytes
Chylomicrons + –not usually tested for though
Sudan 3 + staining for fat globules
Exudate- Pleural fluid LDH > 2/3rd of upper limit of normal or > 0.6 of serum LDH, Pleural fluid Protein > 0.5 of serum protein (2-6 g/dl) (Light’s)
Electrolytes and glucose same as plasma
IPHT 3 clinical finding in exam apart HR and RR
Loud P2
Pan systolic murmur in right sternal border ( TR murmur) and ejection murmur in pulmonic area
HEPATOMEGALY/raised JVP
Left parasternal heave
Mechanism of action with salt and freshwater drowning
Both types of nonfatal drowning result in:
- decreased lung compliance
- ventilation-perfusion mismatching
- intrapulmonary shunting, leading to hypoxemia that causes diffuse organ dysfunction.
Previously:
Salt water: caused plasma to be drawn into the pulmonary interstitium and alveoli, leading to massive pulmonary edema and hypertonic serum.
Fresh water: aspirated hypotonic fluid rapidly passing through the lungs and into the intravascular compartment, leading to volume overload and dilutional effects on serum electrolytes.
Foreign body in the right lung (will use left lung as an example), what do you see in each lung on both right and left lateral decubitus positions
Left lung dependent: Relative lucency (L), Normal (R)
Right lung dependent: Normal (L), Decreased volume (R)
Affected dependent lung will be hyperlucent. Normal lung will compress and partially collapse and appear denser (Normal).
Non-pulmonary Sequelae of Drowning
Hypothermia
Electrolyte imbalance
Trauma
Hypoxic-ischemic damage
Management of Pulmonary Injury of Drowing
1) Supportive care – oxygen, ventilator support and diuretics; if sick and features of ARDS, treat as ARDS
2) Broad spec Abx
3) Surfactant
4) Steroids
5) Multi-organ supportive care
Predictors of good outcomes from drowning
NSR
Reactive pupils
Neurologic responsiveness at the scene
Observed event
Ways to prevent drowning
1) Pool fencing
2) Public education campaigns
3) Swimming programs for infants and toddlers less than four years of age should not be promoted as being an effective drowning prevention strategy.
4) Children less than four years of age do not have the developmental ability to master water survival skills and swim independently.
5) Swimming instruction should be carried out by trained instructors in pools that comply with current standards for design, maintenance, operation, and infection control
6) Residential pools should be fenced on all four sides, and must include a self- closing, self-latching gate.
7) Constant arms-length adult supervision is recommended for toddlers and infants near water
8) Government-approved personal flotation devices (PFDs) should be used for all young children and those who cannot swim.
9) Parents and pool owners should be encouraged to receive first aid and cardiopulmonary resuscitation (CPR) training, and to maintain an emergency action plan
When to expect space-occupying lesions
Suspected when respiratory symptoms don’t disappear promptly when treated with usual treatment (expectorants, bronchodilators, antibiotics)
Signs of obstructive lesion
Ipsilateral compression of normal aerated lung Widening of intercostal spaces Flattening/descent of diaphragm Mediastinal shift away from lesion Wheeze
Imaging modalities for thoracic tumours
CXR
U/S: can locate and help with needle aspiration of pleural effusions
CT: Best able to provide detail for Mediastinal pulmonary and diaphragmatic densities
MRI: Distinguishes between vascular and mediastinal structures and more sensitivity than CT in detecting intraspinal extension
Echo
Aortograms: Useful for identification of bronchial arteries, Can rule out vascular lesions, rings, sequestrations and other malformations
Bronchoscopy: Allows evaluation of tracheobronchial tree, vocal cords, laryngx,
trachea, and major bronchi/segmental bronchi
Which lymph nodes drain the pulmonary parenchyma
Disease in right lung drains into the right scalene lymph node
Disease in left lung drains into either right or left scalene lymph nodes
Where are the scalene lymph nodes?
Lymph nodes are within triangular fat pad
Bound by internal jugular vein (medial), subclavian vein
inferior), posterior belly of the omohyoid muscle (superior
Characteristics of Pulmonary Hamartoma
Benign tumour
Consist of cartilage, with epithelium, fat and muscle
Typically located in periphery (can be seen with intermediate/primary bronchi)
“Popcorn like” calcification is pathognomonic
2 types of bronchial adenoma
Carcinoid (90%)
Cylindromatous (10%)
Characteristics of Papilloma of Trachea and Bronchi
Typically multiple lesions
HPV plays a role in pathophysiology (serotypes 6 and 11 implicated in recurrent papillomatosis)
Juvenile forms do not undergo malignant transformation
Laser CO2 ablation most commonly used as treatment
Symptoms of Papilloma of Trachea and Bronchi
Depends on location and size
Dyspnea, hoarseness, stridor are most common (2/3 of cases)
Cough (initially dry, then productive)
Lesions may be attached by pedicle à oscillate in and out of orifices during inspiration/expiration
May be asymptomatic if slow growing and high within the airway
Wheeze is earliest sign of tracheal papilloma
Eventually develops into stridor, with associated slowly developing dyspnea
May see obstructive emphysema, atelectasis, pneumonia, abscess, empyema and bronchiectasis
Characteristics of Hemangioma of the Trachea
Congenital hemangiomas are one of the most common tumors of the airway in children
Usually located below vocal cords
Typically flat, sessile
90% of patients have development of symptoms @ 6 months
o Suggests proliferative phase at this age
Dx: Best done with bronchoscopy DO NOT biopsy Tx: - Tracheostomy necessary for severe obstruction - Steroids - Beta blockers
Symptoms of Hemangioma of the Trachea
Insidious onset
Stridor, retractions, dyspnea, wheeze, +/- cyanosis and cough o Intermittent symptoms and labile
Absence of leukocytosis and fever
What are the mediastinal borders?
Anterior: Sternum
Posterior: Vertebrae
Superior: Suprasternal notch
Inferior: Diaphragm
Encapsulated by parietal pleura
What is the superior mediastinal compartment?
From angle of sternum, to the intervertebral disk between T4/5
What is the anterior mediastinal compartment?
Portion of mediastinum anterior to the anterior plane of trachea
What is the middle mediastinal compartment?
Portion containing the heart and pericardium, ascending aorta, lower segment of the SVC, bifurcation of the pulmonary artery, trachea, main bronchi, and bronchial lymph nodes
What is the posterior mediastinal compartment?
Portion that lies posterior to the anterior plane of the trachea
Characteristics of bronchogenic cysts
AKA: foregut duplication cysts
- Classified as tracheal, hilar, carinal esophageal, and miscellaneous
- Usually located in middle of mediastinum, but can be anywhere in mediastinum
- May contain any or all of the normally present tissues in trachea and bronchi
Symptoms of bronchogenic cysts
Typically asymptomatic
May be frequent URTI, sternal discomfort, respiratory difficulty (cough, noisy
breathing, dyspnea, cyanosis)
If located below carina, can cause severe respiratory distress, due to mainstem bronchi compression
Need to identify early
Radiographic features of bronchogenic cysts
Single, smooth bordered, spherical mass
o Similar density to cardiac shadow
o Unusual to have calcification
o Can show air fluid levels due to communication with tracheobronchial tree
§ Can see connection with bronchoscopy if communication exists
o Moves with respiration (seen on fluoroscopy)
o Occasionally seen on prenatal U/S
Characteristics of Esophageal cysts (duplication)
Located in posterior mediastinum
o Most typically on the right, intimately associated with the wall of the esophagus
Characteristic type: Resembles adult esophagus with cyst lined by noncornified stratified squamous epithelium, Well defined muscularis mucosa and striated muscle in the wall
May be associated with dyspnea and regurgitation
Barium swallow shows smooth indentation of esophagus
Esophagoscopy shows indentation of normal mucosa by soft, pliable movable extramucosal mass
Characteristics of Gastroenteric cysts
Arises from foregut, typically lies in posterior mediastinum against vertebrae
- Typically posterior and lateral from the esophagus
- Male > Female
- Lining is generally ciliated if arises from embryonic esophagus
- Can be relatively certain that a posterior mediastinal cyst is enteric if microscopic exam shows gastric or intestinal type of epithelium
Typically symptomatic due to pressure on thoracic structures, or rupture into the bronchi
This can lead to massive hemoptysis and death
Most common thymic lesion
Thymic hyperplasia
Normal age range to see thymic shadow on CXR
Normally, see thymic shadow during first months of life, typically disappearing by 1 year
Common to see cervical extension
Characteristics of Benign Cystic Teratoma
Results from faulty embryogenesis of thymus, or local disclocation during embryogenesis
- AKA mediastinal dermal cyst
- Contains ectodermal tissue (hair, sweat glands, sebaceous cysts, teeth), mesodermal and endodermal tissue
Most common tumors in the posterior mediastinum
Neurogenic Mediastinal Tumors
Neurogenic Tumors of Sympathetic origin
Neuroblastoma
Ganglioneuroma/ Ganglioneuroblastoma
Pheochromocytoma
Chemodectoma
Causes of Lymph node enlargement in the hilum or mediastinum
TB, fungal, bacterial or inflammatory lung disease (sarcoid)
Masses of Anterior Mediastinum
Teratoma
Thymoma
Terrible Lymphoma (or T cell Lymphoma)
Thyroid
Masses of Middle Mediastinum
Esophageal Parathyroid Adenoma Bronchogenic cysts Foregut duplication cyst Tracheal tumours
Masses of Posterior Mediastinum
Neurogenic Tumours
Neuroendocrine Tumours
Are most pulmonary tumours in children malignant?
Yes Carcinoid tumors (40%), Bronchogenic carcinoma (17%), and Pleuropulmonary Blastoma (15%)
Causes of benign pulmonary tumours
Plasma cell granuloma (most common)
Hamartoma
Causes of malignant pulmonary tumours
Bronchial adenoma (most common) Bronchial carcinoid Cylindroma Mucoepidermoid tumour Mucous-gland adenoma Primary carcinoma of the lung Undifferentiated carcinoma Adenocarcinoma Squamous cell carcinoma Pleuropulmonary blastoma
Causes of metastatic pulmonary tumours
Wilm’s tumour Osteosarcoma Ewing’s sarcoma Rhabdomyosarcoma Hepatocellular carcinoma Hepatoblastoma Neuroblastoma Germ cell Tumours
Characteristics of Plasma cell granuloma
Slow growing, locally invasive
Represent an inflammatory response to previous infectious or traumatic insult
Only 20% of patients have a clear documented pulmonary insult prior
Presentation varies:
o 30% are asymptomatic
o Fever (22%) and cough (20%) are common
o Hemoptysis, pain and pneumonitis
Characteristics of Pleuropulmonary Blastoma
Occurs only in children (Distinct from pulmonary blastoma of adults)
- Embyonic neoplasm from thoracopulmonary mesenchyme
- Aggressive with poor prognosis
Classification:
o Type 1: Cystic
o Type 2: Cystic and Solid
o Type 3: Purely solid
- Microscopically seen areas of high mitotic activity with areas of undifferentiated loose medsenchymal spindle cells
o Type 1 has rhabdomyoblastic differentiation
o Type 2 and 3 have cartilaginous differentiation
- History of childhood neoplasms or congenital dysplasia (lung, kidney, thyroid) in 25% of cases
Presentation of Pleuropulmonary Blastoma
Cough, breathlessness
o May have fever
o Often discovered after failed treatment with antibiotics for “chest infection”
o Type 1 tends to present earlier
Assessment of chest wall function
Chest wall configuration (scoliosis, overdistension etc.)
Pattern of spontaneous breathing
- Thoracic and/or abdominal breathing
- Paradoxical thoracoabdominal movements: inspiratory rib cage retraction, paradoxical inspiratory abdominal retraction (unilateral or bilateral)
Specific Maneuvers
- Maximum variation in thoracic circumference
- Maximal excursion or diaphragm (inspection and percussion)
- Cough strength
Assessment of Resp Fxn in Chest Wall Dysfxn
- Spirometry (esp FVC) - annual
- MIP (mouth or sniff), MEP
- Peak Cough - annual (<160-200 L/m = ineffective) -DLCO
- Pulse Ox and End-tidal CO2
- Overnight assessments: Oximetry + CO2, or PSG
- FVC 40-60% = low risk noctural hypovent
- FVC <40% or diaphragm weakness= ↑ risk
- Annual assessment is FVC <60%, or symps
Peak cough <160-200 L/min = ineffective (teens/adults)
-↑risk of resp infection, failure
Mgmt of Children w/ Chest Wall Dysfxn
-Optimize: nutrition, oxygenation, electrolytes
-Treat non-related resp d/o: asthma, allergy, T&As, etc.
-Prevent lung infections: Avoid smoke-exposure, large daycares. Flu shot. 23-valent vaccine.
-Respiratory muscle training useful in some d/o
-Assisted cough and lung-recruitment - either manual or mechanical - esp. If recurrent infctns -Ventilatory support: Nocturnal BiPAP recommended in NMD w/ alveolar hypoventilation
Consider if FTT or recurrent infection (>3/yr)
-Consideration for tracheostomy
Causes of chest wall dysfunction
1) Central drive of breathing
2) Upper motor neuron
3) Lower motor neuron
4) NM junction
5) Respiratory muscles
6) Nonmuscular, chest wall structures
Despite differences in pathogenesis, the various entities involved in chest wall dysfunction share which clinical and physiologic features
-Leads to Restrictive pulmonary disease: ↓ FVC & FEV1, Normal V1/VC ratio
-↓ Strength of resp muscles (high variability)
-↓ Ventilatory response w/ exercise
-RV Normal or Increased (if weak exp ms)
-When resp muscle strength <50% predicted, the
decr in VC is greater than expected due to ↓ed
compliance of both the lungs (atelectasis) and chest
wall (constovertebral/costosternal jt anyklosis)
-Daytime hypercapnia usually present when resp muscle strength <25% (can occur sooner)
-Less severe weakness may still have noctural ↑CO2 or hypercapnia with illness, anesthesia, etc
Diseases of Motor Neurons
SCI CP SMA SMA with Resp distress type 1 Phrenic nerve injury Guillan Barre
Key features of SMA
AR disorder of the SMN1 gene (survival motor neuron) - essential to motor neurons
-Mutation leads to primary degeneration of anterior horn cells +/- bulbar nuclei
Types of SMA
SMA-1
SMA-2
SMA-3
Characteristics of SMA-1
symptoms manifest by 6-months, can manifest in-utero (↓ fetal mvmt)
○ Incidence 1:10,000; 2nd most common severe childhood NMD (behind DMD)
○ Impaired head control, weak cry, cough
○ Paradoxical breathing due to intercostal muscle weakness
○ Diaphragm relatively spared
○ Chest radiograph: bell-shaped, small volumes
○ At risk for swallowing dysfxn, aspiration, recurrent resp failure w/ illness/virus
○ Poor prognosis - 95% mortality by 18mo (respiratory failure) w/o intervention
Respiratory mgmt = highly controversial - palliative vs. life-prolonging
■ Chronic non-invasive used increasingly oftern 16+ hrs/day
■ Non-invasive recommended over tracheostomy
○ Mechanical in-exsufflation, minimum BID
■ Used as often as necessary to maintain SaO2 >95% w/ illness
■ Used to maintain sats >95% during illness
Characteristics of SMA-2
Type 2 = intermediate form, largest group of SMA pts
○ Present btw 6mo-1year
○ Able to sit, cannot walk
○ At risk of respiratory failure due to:
■ Aspiration, reflux, recurrent atelectasis, resp infctn, weak cough, scoliosis
○ Recurrent infections usu precede nocturnal hypox/hypovent
○ With resp support (non-invasive, cough-assist, prevention) good QOL and lifespan into early adulthood expected
Characteristics of SMA-3
Onset after 18 months, able to walk, resp involvement usu minimal
Characteristics of SMA with Respiratory Distress Type 1 (SMARD1)
- Presents in first weeks of life w/ acute life-threatening resp distress & diaphragmatic paralysis
- Autosomal recessive, of gene encoding immunglobulin μ binding protein 2
- Peripheral muscle weakness initially just in lower limbs, and not generally a presenting feat
- Prenatal testing/diagnosis possible
Classification of Diaphragmatic Disorders
1) Disorders of Innervation
2) NM Junction
3) Muscle disorders
4) Disorders of Anatomy
5) Idiopathic
Most common cause of phrenic nerve injury
Injury due to thoracic/neck surgery
Most occur on right side; bilateral = 10%
Manifests as elevation of the hemidiaphragm
In neonates - freq causes resp failure
Older patients, often asymptomatic
How can fluoroscopy or U/S diagnose phrenic nerve injury/diaphragmatic palsy?
Sniff test or spont breathing shows paradoxical diaphragm movement
Treatment for phrenic nerve injury
Asymptomatic pts = no therapy
Symptomatic = ventilatory support, +/- plication
Characteristics of Guillain Barre syndrome
Acute, inflammatory demyelinating disease of peripheral nerves Autoimmune dz (likely) triggered by infection- CMV, EBV, Varicella, Mycoplasma, campylobacter flu vaccine
Diagnosis clinical: tingling paresthesia of distal extremities, proximal muscle weakness, pain
Respiratory failure may develop: aspiration, impaired cough, Resp muscle weakness
Early Rx w/ IVIG, Plasma exchange may hasten resolution. Steroids = no effect.
Characteristics of DMD
X-linked AR mutation to dystophin gene = most common severe muscular dystrophy
(DMD = lack of dystophin, Becker MD = expression of mutant dystorphin )
Restrictive lung dz 2° to muscle weakness, scoliosis, chest wall ankylosis, obesity
Maximal FVC typically occurs at age 10-12
Recommended pulmonary assessment for DMD
FVC, MIP/MEP, peak cough, Blood Gases / CO2s, and O/N pulse oximetry to monitor progression
Long-Term Management of Respiratory Disability in DMD
First decade: Prevent infxns (Flu, 23-valent vax), exercise, Rx other resp problem (asthma, T&A)
Second decade: Volume recruitment, mechanical ventilation will be reqd
Scoliosis can impact FVC, muscle strength - therefore aggressive management recommended
-Early surgery = Rx of choice: when Cobb angle >20degrees, FVC >40%
Management of acute respiratory deteriorations in DMD
1) During infection: Assisted cough PRN and NIMV to maintain SaO2 > 95% (R/A)
2) Oxygen used with caution, can mask hypoventilation
3) Early antibiotics
4) Inability to maintain SaO2 >95% in R/A = indication of admission
5) If intubation reqd, protocols for extubation = highly successful (extubate to NIV and cough assist)
6) Written action plan for all DMD pts
Role of steroid therapy in DMD
1) Early Rx w/ long-term steroid: Slows decline in muscle strength/fxn → slows loss of ambulation
2) prevents scoliosis and retards respiratory decline
3) May improve cardiac fxn
4) Recommended once child reaches plateau phase in motor skills (age 4-8yrs)
5) Recommended to continue daily steroid Rx even after loss of ambulation
Deflazacort (0.9 mg/day) recommended over Prednisone (0.75mg/day)
-Deflazacort = less wt gain, ↓ behavioral effects
Characteristics of Congenital Myotonic Dystrophy
Severe neonatal form affects 10-15% w/ Myotonic Dystrophy
Presents: generalized hypotonia (w/o myotonia), respiratory & feeding difficulties
CXR = thin ribs, right hemidiaphragm elevation
-Significant diaphragmatic weakness at birth
Associations: Polyhydramnios, prematurity, hydrops w/ effusion and pulmonary hypoplasia may contribute to pulmonary morbidity
Characteristics of Juvenile Myasthenia Gravis
Autoimmune d/o vs neuromuscular junction
Characterized by autoantibodies vs. acetylcholine receptor (AchR) or sometimes MuSK protein
Abn muscle fatigability
Myasthenic crises → respiratory failure; triggers include: infection, fever, stress, meds
Diagnosis: Response to Acetylcholinesterase inhibitor, eclectorphysio studies, ciculating Abs
Long-term mgmt: Acetylchoinesterase meds (pyridostigmine) and immune-suppressants
The effect of scoliosis on pulmonary function
Distorts thoracic cage → cardiopulmonary dysfxn may impact QOL, lifespan
“Thoracic Insufficiency Syndrome” = spine or chest wall d/o which impact pulm fxn or growth
Cobbs angle >50-60 = restrictive dz (rare before this)
↓FVC>↓RV → mild ↑RV/TLC (Minority show obstruction → mainstem distortion)
Cobbs > 60 = ↑ risk Nocturnal hypoventilation
Most common form of scoliosis = idiopathic (85%)
Impact of scoliosis on lung growth
Controversial
Congenital/infantile scoliosis: decreased alveolar multiplication
Juvenile/Adolescent: decreased Alveolar size
Potential assoc btw early scoliosis & pulmonary hypoplasia
Congenital & Infantile = serious condition → progression to deformed/rigid chest affects lung dev
Pulmonary complications post scoliosis surgery
Most common immediate post-op morbidity & mortality
Include: atelectasis, hemo/pneumothorax, pulm edema, UA obstructn, fat emboli
NIMV and mechanical in/exsuff = valuable to decrease duration of intubation (in congenital scoliosis)
Improvement in lung volume, arterial oxygenation occurs late after surgery
-May take >2-yrs for measureable improvement postop, can sometimes worsen pulm fxn
Characteristics of Asphyxiating Thoracic Dystrophy (Jeune Syndrome)
Most common form of Hypoplastic Thorax Syndromes
Autosomal recessive d/o - narrow hypoplastic ribcage, short-limb dwarfism
Assoc: pelvic & pharyngeal abn, polydactyly, liver & kidney abn, ↓plt, Shwachman synd
Diagnosed clinically at birth: thorax circumference <75% of head, tachypnea
CXR: narrow rib cage, high clavicles, short horizontal ribs, flaring costochondral jxns
CT: “Four-leaf clover” caused by foreshortened ribs
Most die shortly after birth from resp failure; highly variable in survivors
Improvement may occur w/ age → justifying life support (long-term vent) early
Characteristics of Jarco Levin Syndrome
Includes 2 d/o =Spondylocostal dysostosis & spondylothoracic dysplasia
Broadening, bifurcation & fusion of ribs,
congenital scoliosis & short vertebral ht
Manifests as shortened thoracic height, fanlike
rib configuration, fusion costovertebral junctions
Both AD & AR inheritance
The Chest Wall in Obstructive Pulmonary Disease
Overinflation → mech.l disadvantage: flattens diaphragm, ribs more horizontal = ↓power
The Chest Wall in Obesity
↓FRC due to mass load of adipose tissue on rib cage / abdomen
With morbid obesity FRC can reach RV → therefore marked ↓ERV, ↑IRV
Decreased pulmonary compliance - due to dependent atelectasis, increased pulm blood flow, ↓FRC
↓ Physical performance = ↑ metabolic cost of exercise, ↑ fatigue, +/- ↑ exercise induced bronchospasm
Association with OSA
Characteristics of the Chest Wall of the Newborn
1) Diaphragm insertion into ribcage more perpendicular → inward displacement of lower ribs
2) ↑ compliance of ribcage → inward displacement w/ deep inspiration
3) If intercostal muscles relax (ie REM sleep) → even normal resp leads to inward displacement
4) Inward displacement = ↓ Tidal Volume, Paradoxical breathing
5) Rapid breathing, w/ limited diaphragmatic excursion - to overcome increased tendency to fatigue (During dz states RR ↑s - limits contraction strength - reduces diaphragm fatigue)
6) Newborns prevent resp failure by increasing resting alveolar gas stores (ie End Expiratory Volume)
- Done via: - ↑ RR - limits time for expiration
- Braking the expiratory flow by breathing vs. closed glottis
- Progressive post-inspiratory decontraction of the diaphragm
Definition of Childhood Pulmonary Arterial HTN
Mean PAP ≥ 25 mmHg (new guideline = 20)
Normal pulmonary artery wedge pressure (≤ 15mmHg)
Elevated PVR
PAH (by definition) occurs in the pre-capillary vessels and thus requires normal PA wedge pressure and excludes causes of pulmonary venous HTN
5 clinical classes of pulmonary HTN
1) Pulmonary Arterial HTN (includes PPHN, PVOD)
2) Pulmonary HTN caused by left heart disease
3) Pulmonary HTN caused by lung diseases and/or hypoxia
4) Chronic Thromboembolic Pulmonary HTN
5) Pulmonary HTN with unclear multifactorial mechanisms
Characteristics of PPHN
Unique form of PAH – often resolves completely with proper intervention/support, vs most other PAH requiring lifelong Tx
▪ Almost always transient
Characterized by elevated PVR, R-L shunt, severe hypoxemia
Often associated with pulmonary parenchymal abnormalities (ie. Mec asp, sepsis, pneumonia, difficult transition), or with hypoplasia, perinatal stress etc
Suspect ACD/MPV if:
1) PPHN that’s refractory to Tx or brief response to iNO/IV epoprostenol
2) Late onset presentation (12- 24 hours after birth)
3) Other non-lethal congenital malformations (Ie. Cardiac (HLH), GI (malrotation/atresia), Renal)
Characteristics of Idiopathic PAH
Characterized by progressive PA vascular obliteration and RV overload
Meet criteria for IPAH if you have PAH, and other causes are ruled out
Pathobiology features of PAH
1) Vasoconstriction
Abnormalities include: prostacyclin pathway, endothelin system and NO production/availability
Vasoconstriction -> medial hypertrophy of vascular bed -> intimal fibrosis (adolescents/adults) -> plexiform vascular lesions and other non-reversible changes (adults)
As you progress, your vasculature is less responsive to vasodilator therapy
2) Endothelial dysfunction
Key factor in mediating the structural changes in the pulmonary vasculature seen in PAH
Leads to the release of: vasoconstrictive agents, vasoproliferative substances, chemotactic substances attracting SM cells into vascular walls, thrombogenic substances
Common genes associated with hereditable PAH
BMPR2
ALK-1
Endoglin
Pathophysiology of PAH
Normal PVR decreases after birth and within 4 – 6 weeks of life reaches normal adult levels
- Normal pulmonary vascular bed is low pressure, low resistance
- Highly distensible and can accommodate large increases in pulmonary blood flow
PAH -> unable to accommodate increase pulmonary blood flow -> increase PAP at rest and more-so on exertion -> RV hypertrophy (compensatory and initially help deal with increased RV afterload) -> septum flat, then bow into left heart (RVH now becomes detrimental)-> left sided diastolic dysfunction which in severe cases may cause worsening of PH and RV failure
With exercise, patients unable to increase CO to meet O2 demands and thus feel exertional dyspnea and may have exertional/post-exertional syncope
2 most frequent mechanisms of death in PAH
- Progressive RV failure – progressive dyspnea and decrease in CO
- Sudden death – from dysrhythmia, likely secondary to hypoxemia
May also have PE, pulmonary arterial aneurysm rupture, pulmonary hemorrhage, RV ischemia
Illnesses (Ie pneumonia) can be fatal, as alveolar hypoxia causes hypoxic pulmonary vasoconstriction, leading to inability to maintain adequate cardiac output → cardiac shock and death
Symptoms of PAH
Symptoms: highly variable (Most common, dyspnea, fatigue, +/- chest pain)
Infants: low CO (tachypnea, tachycardia, poor appetite, FT, lethargy, diaphoresis, irritability)
Cyanosis with exertion (R→L shunt via PFO or other shunt)
Dyspnea/syncope on exertion
Chest pain (crying spells in infants)
Peripheral edema
Physical exam findings of PAH
Loud single P2 – from high RVSP
Murmur from tricuspid insufficiency (pan-systolic) – from
high RVSP
Murmur from pulmonary insufficiency (high pitched diastolic) – from high pulmonary pressures
RV gallop
May be S3 or S4
RV failure – elevated JVP (rare), hepatomegaly, peripheral edema
Clubbing
Signs/symptoms of systemic disease
Tests for PAH
EKG, CXR
Echo (look for left heart disease, septal bowing)
PFTs (should be normal except for low DLCO)
V/Q scan
BW
PSG
Cardiac Cath (should be done prior to initiation of PH-specific drug therapy)
Gold standard for assessing severity, prognosis and reactivity of PH
Cardiac Catheterization
Gold standard for assessing severity and prognosis
Do vasodilator therapy during cath (iNO, IV epoprostenol)
Positive response = reduction in mean pulm art. pressure by at least 20%
Brisk acute vasodilator response predicts response to CCB
Duration of symptoms prior to Dx not appear to correlate with likelihood of acute response or lack thereof
Marked variability in biology
Treatment for PAH
No cure, no single therapeutic approach that works for all patients
Pulmonary vasodilator must be balanced with potential effects on systemic circulation
Huge effect of hypoxic vasoconstriction with illness
Vaccines for influenzae and pneumococus
Antipyretics for fever (minimized metabolic demands on compromised Cardio/Resp system)
Low threshold for vasodilators (iNO) in face of acute illness with hypertensive crisis
May need antitussive medication to reduce pulm arterial pressures
Avoid decongestants with pseudoephedrine
Prevent constipation
General treatment measures for PAH
Ensure fully vaccinated, peds patients have much more reactive vascular bed, thus simple resp infection can cause V/Q mismatch, hypoxemia and subsequent catastrophic PH crisis
Anti-pyretics to be given aggressively
iNO for acute PH crisis
Avoid decongestents with pseudoephedrine
Anticoagulant recommendations for PAH
Indication comes from observational data in adults – IPAH and APAH lungs often have thrombotic lesions, some patients have underlying coagulopathy, poor RV function can lead to stasis and thrombus formation
data limited, but supportive for chronic anti-coagulation
Some people favour warfarin in patients with R-sided failure to achieve INR of 1.5, care with toddlers and trauma (adults target 1.5 – 2)
Contraindication to warfarin – can use LMWH
What is considered a “response” to CCB during a cardiac Cath?
‘responder’ = decrease in mean PAP ≥ 20% from baseline with no clinically significant decrease in CO and decrease or no change in ratio of PVR to SVR
Mechanism of Nitric Oxide for PAH
L-arginine → NO (by NO synthase)
Selectively relaxes pulmonary vessels (versus the other vasodilators mentioned)
When inhaled, it’s inactivated by Hgb thus no systemic response
May help as antiproliferative agent
Tx for PPH, exacerbation of IPAH, peri/post-operative PH and other forms of PAH
Mechanism of Phosphodiesterase in treatment of PAH
Phosphodiesterase 5 inhibitors prevent breakdown of cGMP, thus increasing cGMP which potentiates vasodilation with NO
- Sildenafil (PO, TID)
Components of WHO functional status
- PH, no physical activity limitation; ordinary physical activity does not cause undue dyspnea, fatigue, chest pain or near syncope
- Slight limitation of physical activity. Comfortable at rest, but ordinary activity causes undue dyspnea, fatigue, chest pain or near syncope
- Marked limitation physical activity; comfortable at rest, but less than ordinary activity causes undue dyspnea or fatigue, chest pain or near syncope
- Inability to carry out any physical activity w/o symptoms; signs of R-sided failure; dyspnea, fatigue may be present at rest; discomfort increased by any physical activity
What is cor pulmonale?
= Pulmonary Heart Disease
clinically useful definition: involvement of the RV (hypertrophy, dilatation or failure) as detected by clinical signs, CXR, ECG, echo, cardiac cath or autopsy, which is caused by altered pulmonary structure and function and not due to diseases primarily involving the left or right side of heart
Key points of Fetal circulation
- 16th week of gestation → all bronchial airway generations have formed along with accompanying pulmonary arteries
- 3rd trimester → pulmonary vascular surface area increases 10 fold with concomitant development of distal airway, alveolar ducts and saccules
- Larger arteries develop muscle coat earlier whereas small arteries have minimal smooth muscle and develop muscular coat with normal postnatal growth
- Fetal pulmonary circulation receives < 8% of ventricular output due to high PVR (most RV output crosses the dutus arteriosus to the aorta)
- During late gestation, pulmonary blood flow increases in proportion to lung weight and increased vascular cross-sectional area but mean PAP increases as well → PVR increases with GA
Mechanisms for high fetal PVR
Lack of gas-liquid interface and rhythmic distension of the lung
Low oxygen tension (fetal PaO2 is 20-25 mmHg)
Low basal production of endogenous dilators (prostacyclin and NO)
Increased production of vasoconstrictors (endothelin-1 and leukotrienes)
Key points about the transition circulation of the baby
At birth pulmonary blood flow increases 8-10 fold and PAP decreases to levels about 50% of systemic → stimulation of NO production contributes substantially to fall in PVR
Components of the Pulmonary circulation
Pulmonary circulation: RV outflow tract, main PA, major branches to left and right lung, lobar branches, intrapulmonary arteries, arterioles, capillaries, venules, veins
-3 types of pulmonary arteries
● Elastic PAs (> 1000 um external diameter) – central and extralobular
● Muscular PAs (100-1000 um) – accompany bronchioles within lobules
● Pulmonary arterioles ( <100 um) – terminal branches of the PA tree and supply alveolar ducts and alveoli
2 types of small pulmonary artery branches
● Conventional branches – travel alone and usually smaller, branch from main arterial channels and extend to the periphery at the end of the respiratory bronchioles (numbers fixed after 18 months)
● Supernumerary branches – more numerous, present at birth and can participate in gas exchange (increase with septation and formation of new alveoli up to 3 years)
Components of the Bronchial circulation
- Receives 1-2% of total cardiac output
- Supplies airways, pulmonary nerves and ganglia, walls of elastic and some muscular pulmonary arteries and veins, lymph nodes and connective tissue septa and pleura
- Flow may increase substantially with pathology causing chronic inflammation and injury (e.g. CF, BPD, bronchiectasis) and acute increases may contribute to lung edema
- Marked variability of branching patterns → 40% have one bronchial artery to each lung -Bronchial veins empty into azygos, hemiazygos or intercostals veins → right atrium
- 1/4-1/3 of blood goes from bronchial veins to RA and remainder flows from pulmonary veins to LA
Regional variations in blood flow in the lung
Zone 1: alveolar pressure > pulmonary artery pressure and pulmonary venous pressure = pulmonary capillaries are collapsed (thus no perfusion)
Zone 2: pulmonary artery pressure > alveolar pressure > pulmonary venous pressure = flow determined by difference between pulmonary artery and alveolar pressures (flow begins at top of zone 2)
Zone 3: pulmonary artery and venous pressures > alveolar pressure = flow determined by difference between pulmonary artery and venous pressures (most of the lung is zone 3)
o Largest contribution to resistance is in the capillaries of the alveolar septum > arterioles
With high flow during exercise, how is low PVR maintained?
Passive vascular distention
Recruitment of small pulmonary arteries
Vasodilation
When do the earliest clinical signs of PH generally appear?
During exercise
Increased CO increases PAP because of high flow through restricted vascular bed and inability to dilate -With severe PHTN, CO is unable to increase → fatigue, dyspnea on exertion, syncope or sudden death
How does the RV adapt in PH? Effect on LV?
RV is has a thinner wall and greater volume and surface area than LV → highly compliant chamber that better accommodates increases in filling pressure but poorly designed to handle rapid increases in high systolic ejection pressure → abrupt rise in RV afterload markedly increases RV end-diastolic pressure, decreasing ejection fraction and RV output
Sudden rise in PVR rapidly dilates RV → right heart failure → hepatomegaly, peripheral edema, venous distention
Attempt to compensate by muscle hypertrophy → reduces compliance and increases RV end- diastolic and right atrial pressure
LV function is generally preserved in most with chronic lung dx but high PVR can impair CO (RV dilation distorts LV and impedes filling)
High PVR causes LV dysfunction by decreasing preload and causing paradoxical interventricular septal motion (ventricular interdependence)
Signs of Echo for PH
Increased RV wall thickness, chamber size, flattening or paradoxical motion of IVS,
Delayed opening and early closure of pulmonic valve, incomplete tricuspid valve closure
Tricuspid insufficiency jet reflects the pressure difference between the RV and the RA and using Bernoulli principle (pressure = 4V2 where V is the peak systolic
velocity), is a good estimate of RVsp
What is the only treatment shown to improve clinical course of patients with PH and CLD
Oxygen
Hypoxia is the most common cause of progressive PHTN in CLD → O2 is the mainstay of therapy
BTS recommends targeting O2 sat > 93%
Key points re: PPHN diagnosis and management
Dx requires echo confirming R-L shunting at ductus or PFO in the absence of anatomic heart disease
Clinical features highly suggestive:
1) marked or labile hypoxemia
2) differences in preductal and postductal paO2 at least 5-10 mmHg (not present if shunting primary at PFO)
3) clinical improvement with hyperventilation
Treatment: high FiO2, hyperventilation, sodium bicarb (for alkalosis), inotropes (CVS support), prostaglandins (side effects are hypotneison, worsening R-L shunting and V/Q mismatch), iNO, HFO, ECMO
Poor responders may have lung hypoplasia (think ACD), surfactant def, or other lung disorders
Key points re: BPD/CLD and PH diagnosis and management
BPD with PHTN are prone to recurrent pulmonary edema, frequent chest exacerbations, congestive heart failure and morbidity from viral infections or sudden death
Cardiac complications include LVH, systemic hypertension
Pulmonary circulation characterized by pulmonary vasoreactivity, hypertensive vascular remodeling (increased muscularization with adventitial thickening), decreased arterial number, decreased septation (simple alveoli)
Treatment: Maintain O2 sat > 94-95% → according to BTS guidelines this appears to reduce pulmonary hypertension
Also in CLD:
O2 sat < 90% is associated with incr risk of ALTE while O2 sat of ≥ 93% was not
O2 sat < 92% associated with suboptimal growth
O2 sat ≤ 90% impairs sleep quality while > 93% does not
Mechanisms in CF that cause PH
- Chronic hypoxia (secondary to severe V/Q mismatch from lung disease)
- Chronic hypercarbia with acidosis may cause intermittent spikes in PAP leading to vascular remodeling
- Severe bronchiectasis with progressive interstitial disease decreases alveolar-capillary surface area
- Chronic infection/inflammation can alter pulmonary vascular reactivity and structure
Clinical signs of cor pulmonale in CF
PaO2 < 50, PCO2 > 45, FVC < 60%, RAD on ECG
Mechanism of High Altitude Pulmonary Edema
Occurs when ascending to altitudes usually > 2400 m → alveolar hypoxia disrupts alveolo-capillary barrier → lung inflammation → vasoconstriction → worsening VQ mismatch → overperfusion of some nonconstricted capillaries causes stress failure → vascular injury and increased interstitial and alveolar edema
Sx are severe dyspnea, fatigue, weakness, dry cough, anxiety, hemoptysis
On exam are tachypneic, tachycardic, cyanotic, and have diffuse crackles
CXR shows fluffly densities, PA enlargement
ECG shows tachy, peaked p waves, RAD, ST-T changes, RV hypertrophy
BAL shows high concentration of albumin → permeability edema
How can chronic upper airway obstruction lead to PH?
Caused by repeated episodes of hypoxia
What is Hepatopulmonary Syndrome?
Severe dyspnea on exertion, SOB, clubbing, cyanosis, orthodeoxia (hypoxia aggravated in upright position) spider nevi
Diagnostic criteria:
▪ Liver disease
▪ Oxygenation defect where PaO2 80 or A-a O2 gradient ≥ 15
▪ Pulmonary vascular dilatation seen on lung perfusion scan or bubble echo
o CXR may be normal or show increased markings more prominent at bases
o PFTs may demonstrate restrictive or mixed abn but low DLCO
o Chest CT shows increased central and peripheral vascularity
Dx confirmed by lung perfusion scans (labelled albumin) that show increased activity in extrapulmonary sites or bubble echo
Main cause of refractory hypoxia is intrapulmonary shunting through dilated vessels in the microcirculation = arterioles and capillaries (also have some VQ mismatch)
Severity of liver disease does not correlate
Treatment: liver transplant
Mechanism of ARDS and PH
Injury to pulmonary circulation → increased permeability → pulmonary edema and surfactant inactivation + decreased lung compliance + decreased gas exchange
Also get PHTN → worsens V/Q mismatch and accelerates pulmonary edema formation
Tx: iNO has been shown to lower PAP and improve oxygenation but not to improve mortality or ventilator free days!
3 causes of respiratory complications from cardiac disease
1) Obstruction of Large Airways
2) High Pulmonary Blood Flow from L to R shunts
3) High Pulmonary venous pressure
Characteristics of Plastic Bronchitis
Associated with CHD (usually cyanotic heart disease after fontan), lymphangiectasia, asthma, ABPA, sickle cell anemia, collagen vascular disease
Formation of large airway casts that plug and obstruct medium-sized or small airways
Present with dyspnea, wheeze, pleuritic chest pain, +/- fever
CXR shows focal collapse with compensatory hyperinflation
Dx usually made with bronch
Treatment empirical with bronchodilators, ICS, DNase/NAC
General Considerations for Respiratory Trauma
Uncommon
- Usually blunt trauma
- Penetrating injury – gunshot, stabbing are rare
- > 75% are MVC and rest largely sports injury, physical abuse and fall from height
- B/C high chest wall compliance in peds, you can get significant thoracic trauma without associated fracture
- Follow ATLS guidelines
- If hemodynamically stable, child may be sent to CT for assessment of potentially missed injuries
Important Features of the Pediatric Thorax
High chest wall compliance in peds
More rounded chest with less muscles
More flexible
Elastic rib cage
With this, pediatric patients can have anterior and posterior curvatures of ribs contact each other w/o fracture
Thus blunt injury may cause significant damage to visceral structures without characteristic external findings
Peds mediastinum is much more mobile than adults, so more resistant to injury
Lack of pre-existing vascular disease protects great vessels from injury
Conditions such as tension pneumothorax or hemothorax are very poorly tolerated and must be recognized and addressed
Massive gastric distension can compromise pulmonary reserve
Characteristics of Sternal Fracture
Require high compression crush injury
Exam: local tenderness, ecchymosis, peculiar concavity or paradoxical respiratory movement;
dyspnea, cyanosis, tachycardia and hypotension may be evidence of underlying heart contusion
o Require ICU, monitoring, r/o cardiac injury and tamponade
o Markedly displaced fragments should be reduced under GA
o If significant paradox respiration – mech vent
Characteristics of Rib # and flail chest
Very rare in kids, b/c so flexible
o Multiple rib # with destruction of thoracic skeleton can give you ‘flail chest’ motion
o Unsupported area of chest moves in w/inspiration and out w/expiration result → paradox
o This leads to dyspnea; coughing has little result in this situation
o Clinically: local pain, tenderness, edema, ecchymosis
o CXR–see fracture
Tx: uncomplicated fracture - pain control to allow normal resps
o Physiotherapy to augment cough & mucus clearance
o Severe fracture - analgesia, intermittent PPV and if PTX/hemoTX → chest tube immediately
o Flail chest → consider mech vent (to avoid ARDS – as have airway obstruction, atelectasis and pneumonia)
o Immediate fixation rarely required
Advantages of Tracheostomy in the Trauma situation
▪ Control secretions
▪ Decrease dead space
▪ Control obstructed airway
▪ Mech vent can be applied
5 Direct pulmonary injuries secondary to trauma
- Pneumothorax
- Hemothorax
- Tracheobronchial trauma
- Pulmonary compression injury
- Posttraumatic atelectasis
What is the concern with an open pneumothorax?
Atmospheric air enters and exits unimpeded – huge problem, b/c get severe paradox, mediastinal flutter and if large, more air exchanged at this site then trachea; mediastinum moves like pendulum, compressing contralateral lung on inspiration and ipsilateral on expiration → completely ineffective ventilation w/increase dead space, low Tidal V
Management of traumatic pneumothorax
- A, B, C, D, E
- Monitors, IV access, bloods
- tension – insertion of needle (biggest you can find to fit) in the 2nd ICS, MCL
- Traumatic valvular leak need → occlude (ie. stabbing)
- Persistent leak – insert chest tube
- Persistent air leak may need surgical repair versus resection of affected segment
*OPEN PTX – immediate occlusion of open wound with sterile occlusive dressing, CT insertion connected to underwater seal (prevent conversion of open to tension) → when stable, to OR to debride and surgically close
Most common sequel of thoracic trauma
Hemothorax
Management of Hemothorax
- A, B, C, D, E
- IV access, monitors, bloods
- large chest tube to drain air/blood
- persistent bleed > 1 ml/kg/min w/hemodynamic instability despite resuscitation → take to OR (or at surgeons discretion)
- may get clotting, loculation or infexn w/retained hemothorax
- Fibrothorax (unevacuated pleural blood organized into fibrous tissue) is infection risk and cause chronic cardiorespiratory changes as lung incarcerated and CW immobilized → may require thoracotomy and decortication
Characteristics of Tracheo- Bronchial Trauma
Ruptured trachea/bronchus = rare – secondary to severe compression injury
Big leak distal cause bilateral PTX; proximal more pneumomediastinum, S/Q emphysema
Symptoms and Imaging findings in Tracheo- Bronchial Trauma
- Resp distress, hemoptysis, hemodynamic compromise depending on location (ie. bilat tension PTX)
- CXR – see air leak, tracheobronchogram suggestive;
CT better delineate anatomy, bronch gold standard
Management of Tracheo- Bronchial Trauma
- A, B, C, D, E, monitors, IV access, BW etc
- Maintain airway, chest tubes as needed
- Emergency bronch and immediate repair (thoracotomay and primary repair of defect);
if small tracheal injury – temp trach may be very useful
Characteristics of Pulmonary compression injury (traumatic asphyxia)
- Pulmonary contusion
- Alveolar disruption → interstitial emphysema, PTX may follow
- Damage to vessels → venous distension → extravasation of blood into head/neck → purplish edema here +/- increase ICP due to venous return obstruction
Management of Pulmonary compression injury (traumatic asphyxia)
- A, B, C, D, E, IV access, monitors, BW
- treat supportively and other comorbidities accordingly
Characteristics of Post-trauma Atelectasis
Chest trauma → PTX or HTX or contusion etc gives increased secretion production with decreased clearance secondary to pain or airway obstruction or ineffective cough → atelectasis with risk of infection (syndrome called ‘wet lung’)
Management of Post-trauma Atelectasis
- A, B, C, D, E, IV access, monitors and BW
- Frequent position change
- Encourage airway clearance
- Abx
- Mech vent if needed
- Cautious hydration
5 groups of injuries you can get with thoracic trauma
- CW fractures – sternal and rib
- Pulmonary pathology – traumatic PTX and hemothorax, tracheobronchial trauma, pulmonary compression injury, post-traumatic atelectasis,
- Cardiac/great vessel injury
- Esophageal injury
- Diaphragmatic injury and thoracoabdominal injuries
When to suspect cardiac trauma?
rare – but suspect in any penetration or blunt trauma of chest/neck/upper abdo
Myocardial contusion to vessel rupture
o clinically contusion: arrhythmia, hypotension, severe cases – aneurysm with myocardial wall weakness
o monitor w/serial EKG
o Tx – supportive – tx dysrhythmia, defib, CPR – if persistent dysrhythmia do echo
Perforation – blood loss varies from minimal to exsanguination with or w/o tamponade
o Acute tamponade: distended neck veins, distant HS, low systolic BP with narrow pulse
pressure and elevated venous pressure and pulsus paradoxus
o Dx: echo
o Tx – needle aspiration (sub-xyphoid approach), resuscitation
What do you suspect when you see mediastinal widening on CXR in someone with thoracic trauma who is ++ unwell
Rupture of thoracic aorta
Symptoms and Management of Esophageal Injuries
See w/penetrating injury, forceful retching/blunt trauma, iatrogenic (instrumenting esophagus), ingestion of caustic agents, in delivery room from PPV, spontaneous has been described
Clinically – fever, hypotension, chest and neck pain, pneumomed/PTX/SC emphysema and hematemesis
Tx: A, B, C, D,E as above, CT’s as needed, NPO, Abx, nutrition and operative repair (open and
endoscopic options depend on location, severity, clinical practice at center etc)
Characteristics of Traumatic Blunt rupture of diaphragm:
Penetrating trauma or severe blunt trauma can cause rupture
- L > R (90% on L) - ? secondary to strength on right, liver on right and weak points of embryonic fusion on left
- Most small w/very non-specific presentation of cardio-resp Sx/Sx
- CXR: abn diaphragm contour; contrast swallow to confirm stomach in thorax; CT helpful
- Tx: Surgery (reduce organs into abdomen and closure of defect) and most do via abdomen to assess for intra-abdo injuries
Characteristics of Thoraco-abdominal injuries
Combined injuries seen in MVC, violent sudden/jolting impact
- splenic/hepatic laceration common
- Clinically: RUQ/LUQ pain/tenderness, rigid abdo, peritoneal signs
with elevated lab values
- Tx: A, B, C, D, E, IV access, BW, NG-tube drainage, Abx,
hemorrhage or perforation in abdo → surgical exploration as soon as stable
Definition of an ALTE
“an episode that is frightening to the observer” and has ≥1 of following:
(1) apnea, usually central (less commonly obstructive);
(2) colour change, usually to blue or pale (less often to red and plethoric)
(3) sudden limpness;
(4) choking or gagging
What is Apnea of Infancy?
Apnea of infancy (by definition idiopathic) is a type of ALTE because it frightens parents.
Infants are beyond term postconceptional age when apnea is first noted.
The components of an ALTE are usually present, except perhaps choking or gagging.
Recommendations from AAP guidelines use of home monitors (2003)
(1) It “may be warranted” in selected prems until “43 wks postmenstrual age,” or until “extreme episodes” of apnea, bradycardia, and hypoxemia resolve;
(2) infants who are usually supported at home by mechanical ventilation through a tracheotomy should be monitored.
AAP doesn’t recommend monitoring for kids who have ALTE or who had siblings w/SIDS
Monitoring doesn’t prevent SIDS
Epidemiological risk factors for SIDS
Preterm birth <37 weeks Male sex African-American race Maternal parity more than 2 Late or no prenatal care Mother < 20 Smoking during pregnancy Never breastfed Upper respiratory infection Winter peak Age at death (89% >2 weeks but less than 23 weeks)
Newer risk factors for SIDS identified after interventions to promote back sleeping
Side sleeping Soft bedding Not using a pacifier Bed sharing Being inexperienced sleeping prone Head covered during sleep Out of home child care
DDx of ALTE
RSV, pertussis Sepsis with apnea Syndrome compromising the upper airway Breath-holding spells Seizures Intracranial hemorrhage Exaggerated laryngeal chemoreflex +/- GERD Drugs Tachyarrhythmias Inborn errors of metabolism Hypoventilation during bed sharing or because nose and mouth become covered with bedding
Relevant history points for an ALTE
Duration of the event
Time of day
Adequacy of lighting
Infant’s position within his or her surroundings, and whether the episode began while awake or asleep.
The infant’s color, tone, and the need for and type of resuscitation must be noted.
Was blood or pink froth coming from the infant’s mouth or nose?
Family history of seizures, sudden death, or serious illness with coma among young people must be ascertained.
Was the infant in the early stages of a respiratory illness, or was he or she having coughing paroxysms?
Physical exam findings that should be rule out during an ALTE assessment
muscle tone, alertness, bruising or scalp swelling or disuse of extremities, and fundoscopic evidence of retinal hemorrhages. Evidence of stridor, stertor, chest wall retractions, poor skin perfusion, and cardiac murmurs or dysrhythmias.
Infants younger than 2 months of age should be considered at risk for bacteremic sepsis when they present with apnea or hypotonia and should be treated accordingly.
Labs included in ALTE work-up
baseline: glucose, lytes, bicarb, hemoglobin and WBC,diff, cultures blood/urine; NP swab (RSV) and pertussis; CXR, blood gas (high bicarb may suggest resolved acidosis)
If the infant continues to be limp or if apnea recurs, one should measure ABG, lactate, ammonia, as well as screening the urine for abnormal levels of amino and organic acids and drugs.
Appears ill or w/ altered mental status w/o other cause, video-EEG & imaging CNS (MRI > CT)
Proposed mechanism for ALTE after GERD/RSV
laryngeal chemoreflex apnea (LCRA)
Reflex apnea may be elicited during GER in susceptible infants, particularly when reflux reaches the pharynx, and this apnea may put these infants at risk for an ALTE if not sudden death.
Reflexes (LCRA) elicited only if reflux passes the supraesophageal sphincter
Milk, water, and non-acid secretions/reflux are capable of eliciting profound apnea/LCRA.
Components of Laryngeal Chemoreflex Apnea
Infants attempt to clear fluid that elicits LCRA by laryngeal closure and swallowing during a central apnea.
After the central apnea, any breaths attempted are obstructed so long as upper airway closure persists. When swallowing presumably clears the fluid, the upper airway is opened with a return to eupneic breathing.
The LCR sequence in more mature infants and experimental animals does not involve prolonged apnea, and is as follows: cough, swallowing, arousal if asleep.
The cough-swallow-arousal sequence is much less common when elicited during sleep in immature subjects. In infants, should swallowing be delayed or fail to occur, the apneic phase of the laryngeal chemoreflex can be prolonged, extending over 20 seconds and causing hypoxemia.
Duration of the apneic phase of the LCR seems to be inversely proportional to postnatal age.
These findings suggest that in immature subjects airway protection from aspiration takes precedence over ventilation in some circumstances when even small quantities of fluids (~0.1 mL) come in contact with the larynx
Risk factors for SIDS/Apneas explained by Laryngeal Chemoreflex Apnea
- LCRA and nicotine: pre and postnatal cigarette smoke exposure significantly ↑s risk of sudden unexpected infant death
- Acute infection with RSV has been associated with apnea, esp prone infants. Evidence of a recent RSV inf also markedly ↑the risk for SIDS among prone infants.
- Thought is ↑ secretions in RSV trigger LCRA, & IL’s produced that ↑the LCRA duration.
Characteristics of Apnea of Prematurity
Most apnea among prem infants is “idiopathic” - attributed to immaturity of ventilatory control
Important episodes of apnea:
- Cessation of airflow for 10-20 seconds or longer, OR
- Shorter pauses assoc. w/decreases in Spo2% <90% or in HR<100 beats/m
(if apnea<10 sec, we don’t know what SpO2 decrease is worrisome).
Differential of Apnea of Prematurity besides immature ventilatory control
- ICH
- Sedation crossing the placenta
- Sepsis +/- meningitis
- Heat/cold stress
- PDA
- Hypoglycemia
- Lyte abnormalities (esp. hyponatremia)
- Anemia
- NEC
- Feeding-related apnea
- Heart block or failure lowering cerebral perfusion
- Excessive sedating meds
Most common type of apnea in premature infants
Mixed
- Upper airway obstruction, for which the infant has shorter and weaker “load compensation,” is preceded by brief central apnea, or leads to longer central apnea.
- Infants with a lower minute volume response to increasing CO2 become progressively more hypercarbic and hypoxemic.
- The development of hypoxemia further blunts CO2 response, and the increasing CO2 makes the activities of the diaphragm and genioglossus asynchronous, perpetuating the cycle of obstructive and central (i.e. mixed apneas).
Is there a role of Laryngeal Chemoreflex Apnea in Apnea of Prematurity?
Yes
- Swallowing interrupts LCRA.
- Prem infants swallow more frequently during apnea than during eupneic breathing
- Suggests exaggerated LCRA, possibly caused by pooling of saliva, may explain some apneic episodes.
- LCRA = mixed apnea, similar to the most frequent type of AOP.
What is considered pathognomonic for “central immaturity” of resp control?
Excessive periodic breathing
After onset of periodic breathing, transient upper airway obstruction at pharynx common during the first inspiratory effort after the apneic pause.
Periodic breathing has both central & obstructive apneic components (i.e., mixed).
Natural history of Apnea of Prematurity
Apnea of prematurity does eventually resolve, later prems generally resolves by term, may last longer in earlier prems
Late prems (33-37wks) can have ventilatory / autonomic instability, + incr risk of apneas/brady; are frequently admitted after PMA 40 wks for excessive apneas, periodic breathing or hypoxemia.
Treatment of Apnea of Prematurity
1st line: methylxanthine (caffeine), w/75% prems responsive.
Caffeine recommended for premature infants 500-1250 grams, even before onset of apnea
Not clear how caffeine given prophylactically might reduce the incidence of CLD.
If failed caffeine → often respond to nasal CPAP or nasal intermittent PP ventilation.
Enthusiasm for using high flow nasal cannula instead of CPAP or caffeine
Prems at incr risk of serious apneas post-anesthesia, even at 46+ wks, esp if ventilation/CLD hx
Monitoring prems at home: AAP says monitoring for prems who have apneas until 43 wks PMA.
Definition of Sudden Infant Death Syndrome (SIDS)
“The sudden death of an infant <1 yr age which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.”
What is the triple step model for SIDS?
- Infant @ risk
- Exogenous factors
- Vulnerable period (developmentally).
5 steps in the Respiratory pathway associated w/SIDS
- Baby’s face in the bedding/pillow while sleeping prone (asphyxia & brain hypoperfusion)
- Failure of arousal
- Hypoxic coma
- Brady&gasping
- Failure for autoresuscitation/death
Death results from one or more failures in protective mechanisms against a life-threatening event during sleep in the vulnerable infant during a critical period
Physiology factors related to sleep position that may make the infant more vulnerable to SIDS
- Infants at increased risk for SIDS have been shown to have abnormal arousal, hypoxic drive, and airway protective reflexes, among other physiologic aberrations.
- Infants at greater statistical risk for SIDS compared with controls may have diminished arousal to breathing hypoxic and hypercarbic gases & longer obstructive apnea before arousal and resumption of eupneic breathing.
- Infants at risk for SIDS may have blunted ventilatory responses.
- The ventilatory responses of normal infants may be less when prone than when supine
How is thermal stress a mechanism for SIDS?
Higher ambient temp (28 deg vs 24 deg) increases the arousal threshold to sound in infants about 3 m of age
Arousal response to sound stimuli and air jets applied to the face, is decreased among sleep-deprived infants, prone-sleeping term & prem infants, & prone infants w obstructive apnea.
Thermal stress: (exp animals) increasing core temperature prolongs LCRA;
- Interactive effect of hyperthermia and cigarette smoking in further prolonging the apneic phase
of the LCR.
Risks of SIDS associated with bed sharing
When baby sleeps w/parent = ↑risk of death;, and esp if mom smoker!
Sharing beds = increased risk of suffocation; thermal stress.
Lung pathology from fatal hydrocarbon inhalation
necrosis of bron- chial, bronchiolar, and alveolar tissue, atelectasis, intersti- tial inflammation, hemorrhagic pulmonary edema, vascular thromboses, necrotizing bronchopneumonia, and hyaline membrane formation
Timeline for hydrocardon inhalation
acute alveolitis that is most severe at 3 days, subsides at 10 days, and is fol- lowed by a chronic proliferative phase that may take weeks to resolve.9 Rats develop hyperemia and vascular engorge- ment of both large and small blood vessels within 1 hour of aspiration.10 At 24 hours, there is a focal bronchopneumo- nia with microabscess formation. By 2 weeks, the process largely resolves
Pulmonary lesions are believed to be caused by direct aspiration into the airways
Characteristics of hydrocarbons that make it easier to inhale
Low surface tension
Low viscosity - allows it to spread more readily and deeper
Low surface tension - allows it to spread throughout the TB tree
High volatility - increases the likelihood of CNS involvement
How do hydrocarbons increase surface tension
Inhibit surfactant - predisposes to alveolar instability and atelectasis
Clinical findings or hydrocarbon ingestion
- Cough may appear within 30 min or may be delayed for hours
- normal or decreased breath sounds
- severe injury - hemoptysis and pulmonary edema develop rapidly and resp failure can happen within 24 hours
- can get features of chemical pneumonitis
Imaging findings of hydrocarbon inhalation
Can vary from punctate, mottled densities to pneumonitis or atelectasis and tend to predominate in dependent areas
Can also get air trapping, pneumoatoceles, pleural effusions
Peak within 72 hours and usually clear within days
Gas findings of hydrocarbon inhalation
Hypoxemia without hypercapnia - V/Q mismatch or diffusion block
Destruction of the epithelium of the airways together with bronchospasm adds to teh ventilation-perfusion abN and displacement of alveolar gas by the hydrocarbon vapours adds to the hypoxemia
DDx of hydrocarbon inhalation
Bronchopneumonia
Atelectasis
Salicylate overdose
Other toxic inhalation
Management of hydrocarbon inhalation
Important to avoid emetics of gastric lavage
If no sx and normal CXR - observe for 6 hours
Blood gas if abN exam or CXR noted
Repeat CXR in 24 hours
Oxygen if needed
Maintain hydration but be careful of too much
Examples of hydrocarbons
petroleum solvents, dry-cleaning fluids, lighter fluids, kerosene, gasoline, and liquid polishes and waxes (mineral seal oil)
Most common mechanisms of death in hydrocarbon sniffers
Medullary depression and respiratory paralysis
Why can you see acute hypoxemia at the time of inhalation from hydrocarbon sniffing
Displacement of alveolar gas by the inhaled substance
Pathogenesis of lung injury from smoke inhalation
Thermal and chemical
Thermal - primarily affects supraglottic airways
Generation of noxious and irritant gases
Production of high levels of CO and CO2
Soot particles can cause acute bronchospasm
Causes of CO poisoning
Smoke inhalation - Most common
Poorly functional home heating systems
INadequate ventilation for fuel burning systems
Motor vehicles idling
Pathogenesis of CO poisoning
Results from the combination of CO with Hgb to form COHb leading to severely impaired tissues oxygenation
CO displaces oxygen from Hgb reducing the delivery of O2 to the tissues and shifts the curve to the left
**Although oxygen content of art blood is low, partial pressure of oxygen is not reduced - ventilation may not be stimulated until acidosis develops
***If suspicion of CO poisoning - NEED to do art gas along wth COHb levels
CO also binds to myoglobin - anoxia of muscle cells
In which scenarios can the toxicity of CO poisoning be worse?
Higher altitude
Anemia
Pathologic changes with smoke inhalation
Tracheobronchitis (severity related to tidal volume of smoke)
Acute pulmonary edema (causes by increased pulmonary vascular permeability)
Atelectasis
Pathophysiology of smoke inhalation
Severe damage to upper airway = stridor and increase extrathoracic resistance (usually within 24 hours)
Alveolar hypoventilation
INflammatory changes in the ariways - V/Q mismatch
Altered surfactant function
Pulmonary edema
Oxidants directly from the products of combustion also contribute to airway damage, closure and atelectasis
CLinical findings related to smoke inhalation
Focus on Hypoxemia
May have facial burns, singed nasal hairs, carbonaceous sputum, soot in airway
Blistering, edema of OP, hoarseness, stridor, mucosal lesions of upper A/W
Give oxygen
Resp failure can happen as the result of A/W obstruction - NEED To assess upper airway!
Management of smoke inhalation
Focus on reversing CO poisoning
CO levels may be reduced by half in about an hour when the patient breathes 100% oxygen.
If alveolar hypoventilation, mechani- cal ventilation is necessary
Controversy exists regarding the importance of, and need for, hyperbaric oxygen in the management of CO poisoning - The potential risks of the hyperbaric chamber include oxygen toxicity to the lung,
Scenarios that require ETT in smoke inhalation
1) Severe burns of the nose, face, mouth (as high risk for nasopharyngeal edema and obstruction)
2) Edema of the vocal cords with laryngeal obstruction
3) Difficulty handling secretions
4) Progressive respiratory insufficiency
5) Altered mental status that decreases minute ventilation and diminishes the protective reflexes of he airway
Respiratory manifestations associated with Dermatomyositis
Hypoventilation secondary to muscle weakness
Chronic ILD
Aspiration pneumonia
Pulmonary HTN
