Respiratory Pathophysiology Flashcards
What do pulmonary function tests measure?
Static Lung Volumes
Dynamic lung volumes
Diffusions Capacity
What is FEV1
Forced Expiratory Volume in 1 second
Volume of air that can be exhaled after maximal inhalation in 1 second
Normal = > 80% (this does decline in age)
What is FVC?
Forced Vital capacity
Volume of air that can be exhaled after a maximal inhalation
M: 4.8L
F: 3.7L
What is FVC1 to FVC ratio?
Compares the volume of air expired in 1 second and total volume of air expired
Normal= 75 - 80%
(Useful in determining obstructive vs. restrictive), < 70 suggests obstructive, but normal with restrictive dx.
What is Forced Expiratory Flow at 25-75% Vital Capacity?
Measures airflow in the middle of FEV (FEV 25-75%)
Normal= 100% +/- 25%
Most sensitive indicator of small airway dx, usually reduced with obstructive dx, but normal with restrictive.
What is maximum voluntary ventilation?
Maximum volume of air that can be inhaled and exhaled over the course of a minute
Normal:
M = 140-180 mL
F = 80-120 mL
Best test for endurance
What does the diffusing capacity (DLCO) measure?
Volume of carbon monoxide that can traverse the alveolocapillary membrane per given partial pressure of CO
Normal= 17-25 mL/min/mmHg
(Based on Ficks Law)
What type of patients are at risk for postoperative pulmonary complications?
Age >60
ASA >2
CHF
COPD
Cigarette smoking (> 40 pack years)
In what type of procedures are patients more at risk for postoperative complications?
Aortic > thoracic > upper abdominal > neuro > peripheral vascular > emergency
General anesthesia
Surgery > 2 hours
Which lab value may indicate a risk for postoperative complications?
Albumin < 3.5 (indicates poor nutritional status)
What are some short term effects of smoking cessation?
Carbon monoxide 1/2 =4-6 hrs
P50 returns to near normal in 12 hrs
Short term cessation does not reduce pulmonary complications though
What are some long-term effects of smoking cessation?
Return of pulmonary fx takes about 6 wks. This includes:
Airway function
Mucociliary clearance
Sputum production
Pulmonary immune fx
Hepatic enzyme induction also subsides after 6 wks
What is the best way to reduce anesthesia-related atelectasis?
Alveolar recruitment maneuvers
What are the dynamic volumes (tests) in obstructive dx?
Decreased FEV1
Decreased or increased FEV
Decreased FEV1/FVC ratio
Decreased FEF 25-75%
Normal-increased residual volume
Normal-increased function residual capacity
Normal to increased Total lung capacity
What are the dynamic volumes (tests) in restrictive dx?
Decreased FEV1
Decreased FVC
Normal FEV1 to FVC ratio
Normal FEF 25-75%
Decreased residual volume
Decreased function residual capacity
Decreased total lung capacity
What happens with an extra thoracic obstruction?
For EXTRATHORACIC ~ EXhalation is normal
Patient inhales and the airway collapses (the obstruction is being pulled towards the airway)
Patient exhales and the obstruction is being pushed away
(Inspiratory limb is flat)
What happens with an intrathoracic obstruction?
Remember for an INTRATHORACIC ~ INhalation is normal
The patient inhales and the obstruction is also pulled downwards and away like the rest of the thoracic cavity.
When the patient exhales, the obstruction is push upwards and close, this collapsing the airways
What is asthma?
Acute, REVERSIBLE airway obstruction characterized by chronic airway inflammation and bronchial hyperreactivity
What is the greatest risk factor for developing asthma?
Atopy “the condition of being hyper-allergic”
What is the most common finding in asthma?
Resp alkalosis with hypocarbia (they have tachypnea)
Tachypnea and hyperventilation are result of NEURAL reflexes, not hypoxemia
What does an elevated PaCO2 in asthma show?
Air trapping, resp muscle fatigue and impending resp failure.
What is the anesthetic management of asthma? ( Think airway and vent)
Suppression of airway reflexes!
Avoidance of intubation
Deep extubation should be considered
Vent ~ limit inspiratory time, prolong expiratory time (ok with permissive hypercapnia)
Use an HME filter ~ retains humidity
What is the anesthetic management of asthma (think drugs)
Volatile agents (dilation)
Ketamine (dilation)
Propofol (suppresses reflexes)
Lidocaine (suppresses reflexes)
Avoid histamine-releasing drugs (six, morphine, Demerol)
Iv hydration (reduces viscosity)
How does bronchospasm present?
Decreased breath sounds
Wheezing
Increased peak pressures
Increased alpha angle on EtCO2 (shark fin)
How do you treat bronchospasm
100% FiO2
Deepen the anesthetic
Beta 2 agonist
Inhaled ipratropium (anticholinergic)
Epi
Aminophylline
Helium-oxygen mixture
Hydrocortisone
What is COPD
Umbrella term for chronic bronchitis and emphysema ~ reduction in maximal expiratory flow and a slower forced emptying of the lungs
What are the origins of COPD
Cigarettes
Resp infection
Exposure to dust (coal mining, gold mining)
Alpha 1 antitrypsin deficiency
What are some of the main pathological symptoms of COPD
Loss of elastic components in lung ( decreased recoil —> air trapping)
Reduced airway rigidity ( collapse during exhalation —> air trapping)
Increased gas velocity through narrow airways (decreased pressure in airways —> airway collapse —> air trapping)
Secretions (airflow obstruction and bronchospasm)
What are some common findings with COPD
Flattened diaphragm
Increased AP diameter
Pulmonary bull ar
Increased work of breathing
what is another term for chronic bronchitis?
“ Blue bloaters”
What are some symptoms of chronic bronchitis and how is it defined?
Defined as presence of cough and sputum > 3 months for 2 years
Cigarette common cause
RBCS are over produced (increases blood viscosity)
Chronic hypoxemia and hypercapnia increases PVR —> cor pulmonale
Left heart fx is normal
Weak RV causes back pressure (ascites and liver congestion)
Oxygen therapy is most efficacious therapy
What is another name for emphysema?
“Pink puffers”
Associated with enlargement and destruction of the airways distal to the terminal bronchioles —> reduces surface area for gas exchange—> increase in dead space
What are some common traits associated with emphysema?
Pt has normal (or slightly reduced) PaO2. The PaCO2 is normal or decreased (as result of hyperventilation)
Hypoxemia and hypercarbia can increase PVR later —> RV failure
Alpha-1 antitrypsin deficiency can cause emphysema
What is alpha 1 Antitrypsin Deficiency?
It is a dx where an abnormal variant of the enzyme is produced. The hepatocyte is unable to secrete this enzyme into the blood so it accumulates inside the hepatocyte. This leads to cell death and cirrhosis.
What does alpha-1 antitrypsin Deficiency do to the Lungs?
So alveolar elastase (an enzyme that breaks down pulmonary connective tissue) is kept in check by alpha-1….lack of alpha -1 leads to overactivity of alveolar elastase —> destruction of pulmonary tissue and development of panlobular emphysema.
Where should we maintain a the SaO2 in a patient with severe COPD?
88-92%
Which gas is associated with rupture of pulmonary blebs?
Nitrous oxide
How should you set up your vent for a patient with severe COPD?
Tidal volumes 6-8 mL/kg IBW
Slow inspiratory flow
PEEP
Increase expiratory time to minimize air trapping and auto-PEEP
I.e reduce 1:E ration ~ 1:3, reduce resp rate, and reduce flow resistance by using a larger ETT or frequent suctioning.
What are some etiologies to dynamic hyperinflation with COPD?
High minute ventilation (not enough time to get air out)
Reduced expiratory flow
Increased airway resistance
What are contributing factors to a high minute ventilation?
Large tidal volume
Fast resp rate
What are some factors to reduced expiratory flow?
Bronchoconstriction
Airway collapse
Inflammation
What are some examples of increased airway resistance?
Secretions
Obstructed ETT
Fighting the vent
What are some pulmonary consequences of hyperinflation seen in COPD
Alveolar overdistension
Barotrauma
Pneumothorax
Increased PIP
Increased PP
Increased WOB
What are some cardiac consequences of hyperinflation seen in COPD?
Impaired venous return
Hypotension
Overestimation of CVP and PAOP
What is a restrictive lung dx?
It’s an umbrella term for a collection of disorders that impair normal lung expansion during inspiration
What are some main characteristics of a restrictive lung dx?
Decreased lung volumes and capacities
Decreased compliance
Intact pulmonary flow rates
What airway tests are diagnostic of restrictive lung disease?
FEV1 and FEV < 70%
The FEV1/FVC reaction will be normal
What are some examples of an acute intrinsic restrictive dx?
(Aka Pulmonary edema)
Upper airway obstruction
Aspiration
Cocaine overdose
Neurogenic
What are some examples of a chronic intrinsic restrictive dx?
(Interstitial lung dx)
Sarcoidosis
Drug induced pulmonary fibrosis
What are some dx of the chest wall, mediastinum, and Pluera in terms of restrictive dx processes?
Kyphoscoliosis
Ankylosing spondylitis
Flail chest
Pneumothorax
Pleaural effusion
Mediastinal mass
Neuromuscular disorders
What are some examples of some other restrictive ventilatory defects? (Think more basic)
Obesity
Pregnancy
Ascites
What are some vent strategies for patients with a restrictive dx process?
Smaller tidal volume (6 mL/kg IBW)
Faster resp rate
Keep peak inspiratory pressures below 30 cm H2O
Prolong inspiratory time ( I:E of 1:1)
When is aspiration most common?
During anesthetic induction/intubation
Or within 5 minutes of extubation
What are 3 potential problems of aspiration?
Gastric contents in airway —> obstruction
Gastric contents cause a chemical burn to lung parenchyma —> risk of laryngospasm and impaired gas exchange
Infectious material enters the airway —> bacterial infection
What is Mendelson’s syndrome?
Gastric pH < 2.5
Gastric volume > 25 mL
What are some risk factors to aspiration?
Trauma
Pregnancy
Emergency
GI obstruction
GERD
PUD
Head injury
Seizures
Ascites
Hiatal hernia
What is the hallmark symptom of aspiration?
Hypoxemia
What is the best method to prevent Ventilator associated pneumonia (VAP)?
Avoid intubation
What is the treatment if you have an aspiration?
Head down first!
Upper airway suction
Secure the airway
PEEP to reduce shunt
Bronchodilators
IV lidocaine
Abx if patient develops fever or increase in WBC
What are some other methods to reduce VAP?
Hand washing
HOB > 30 degrees
Daily spontaneous breathing trials
Limit sedation
Oropharyngeal decomination
Subglottic suctioning
What are the three types of pneumos?
Closed
Open
Tension
What does a closed pneumo mean?
There is no communication b/t pleural cavity and atomosphere
Defect is usually in the pulmonary tree or lung tissue, and air enters and exits the pleural space via the defect
What does an open pneumo mean?
The defect is in the chest wall. Air passes b/t the pleaural space and the atmosphere
Lung collapses on inspiration and re expands on expiration
What does a tension pneumo entail?
Can be a closed or open defect
Air is allowed to enter, but not exit the pleural space
This increase in intrathoracic pressure causes a mediastinal shift towards the contralateral side. This compresses the heart and vasculature and reduces venous return
What are the hallmark signs of a tension pneumo?
Hypoxemia, increased airway pressures, tachycardia, hypotension, and increased CVP.
What is the emergency tx of a tension pneumo?
Insertion of a 14g a hip cath in the 2nd intercostal space (mid clavicular) or the 4th/5th intercostal space (anterior axillary)
What is the definite treatment for a tension pneumo?
Chest tube insertion
What gas should be discontinued immediately followed by a pneumo?
Nitrous oxide
What is lymph in the chest called?
Chylothorax
What is blood in the chest called?
Hemothorax
What is an organized blood clot in the chest called?
Fibrothorax
What is pus called in the chest?
Pyothorax (empyema)
What is serous fluid in the chest called?
Pleural effusion.
What are indications for a thoracotomy?
Initial drainage > 1,000
Continued bleeding > 200 mL/h
White lung on X-ray
Large air leak
Where is injury to the thoracic duct most likely to occur?
Usually happens during CVL insertion and it is more likely to occur on the left side
What happens to a flail chest on inspiration? What happens on expiration?
Inspiration: injured ribs move inward
Expiration: injures ribs move outward
Consequences: alveolar collapse, Hypoventilation, hypercarbia, hypoxia
What is the treatment for a flail chest?
Reducing pain (epidural catheter) or block
May need mechanical vent/surgical fixation
In patients at risk for venous air embolism, what positions are the highest risk and what are the lowest? From high to low?
Sitting > supine > prone > lateral
What are the S&S of an air embolism?
Air observed on the TEE
Mill wheel murmur
Decreased EtCO2
Hypotension
Increased pulmonary artery pressures
Dysrhythmias
Hypoxia
Cyanosis
How can you detect an air embolism? From most sensitive to least sensitive.
TEE > precordial Doppler > EtCO2 > CVP > BP/HR/stethoscope
What is the tx for a venous air embolism?
100% FiO2
Flood surgical field with saline
Discontinue insufflation if used
Place patient in Durant’s position
Aspirate air with Central line
How do you determine pulmonary vascular resistance?
PVR = (mean PAP - PAOP) / CO x 80
What are some things that increase PVR?
Hypoxemia
Hypercarbia
Acidosis
SNS stimulation
Pain
Hypothermia
Mechanical vent
PEEP
Atelectasis
Drugs (nitrous oxide, ketamine, desflurane)
What are some things that decrease PVR?
Increased PaO2
Hypocarbia
Alkalosis
Spontaneous vent
Prevention of coughing or straining
Drugs: nitric oxide, nitroglycerin, sidenafil, prostaglandins PGE1/PGE2, calcium channel blockers, ACE inhibitors
What is the tx for carboxyhemoglobin?
Oxygen therapy ~ it’s continued until CoHgb is < 5% or for 6 hours
Hyperbaric oxygen is indicated if CoHgb exceeds 25% or if the pt is symptomatic
What is the risk of CO formation with volatile anesthetic? From greatest to least
Des > Iso»_space;> Sevo
What drugs can you administer via ETT?
NAVEL
Narcan, atropine, vasopressin, epi, lidocaine
What are indications for mechanical ventilation?
Vital capacity < 15 ml/kg
Inspiratory force < 25
PaO2 < 55 @ room air
A-a gradient > 55 @ room air
PaO2 < 200 on 100% FiO2
A-a gradient > 450 on 100% FiO2
PaCO2 > 60
Resp rate > 40 or < 6
What are absolute indications for OLV?
Infection
Hemorrhage
Bronchopleural fistual
Surgical opening of major airway
Large unilateral cyst or bulla
Life threatening hypoxia d/t lung dx
Pulmonary alveolar proteinosis
What size double lumen ETT should you use with a child?
8-9 ~ 26
10 years + ~ 28 or 32
Kids younger than 8 will require a blocker or single lumen ETT advanced into main stem bronchus
What is the most realizable method for identifying the correct double lumen tube placement?
Fiberoptic
How should you set your ventilator for one lung ventilation?
80-100% FiO2
6 mL/kg tidal volume
Inspiratory pressure < 20 cm H2O
Resp rate 12-15
PEEP 5-10
What procedures (right or left) have a higher incidence of hypoxemia?
Procedures that rely on the LEFT lung have a higher incidence. The right lung is larger.
What is the stepwise approach to hypoxemia during OLV?
100% FiO2
Check position of tube/bronchial blocker via fiberoptic
R/o other causes of hypoxemia
Apply CPAP to non-dependent lung
Apply PEEP
Unlike the DLT, a bronchial blocker cannot?
Prevent contamination from contralateral lung,
provide ventilation
Suction secretions from isolated lung
What are the most serious side effects of a mediastinoscopy?
1 hemorrhage
#2 pneumothorax
What is an absolute contraindication to mediastinoscopy?
Previous mediastinoscopy (d/t scarring)
The compression of what artery can lead to cerebra vascular effects during mediastinoscopy?
Innominate artery
Where do you place the SpO2 (or Aline) and where do you place the non-invasive blood pressure cuff during a mediastinoscopy?
SpO2/arterial line on the right( will dampen if innominate artery is compressed)
BP cuff on left (can still take BP if innominate artery is compressed)
What are the degrees of severity for ARDS?
Mild: PaO2/FiO2 ratio < 200-300
Moderate: PaO2/FiO2 ratio < 101-200
Severe: PaO2/FiO2 ratio < 100
What are some vent tactics for ARDs?
Pressure control if avaible
Low tidal volumes 4-6 mL/kg
Plateau pressure of < 30 cm
Resp rate of 6-35 (aim to keep pH 7.3-7.45)
PEEP (whatever is best for oxygenation)
Target SpO2 88-95%
Permissive hypercapnia may be required
What is a class 1 mallampati?
Remember PUSH
Pillars, uvula, soft palate, hard palate
What is a class 2 mallampati
Remember PUSH
Uvula, soft palate, hard palate
What is a class 3 mallampati
Remember PUSH
Soft and hard palate
What is a class 4 mallampati
Hard palate only
What is a normal incisor gap?
2-3 finger breadths or 4 cm
Laryngoscopy may be more difficult if the thryomental distance is what?
< 6 cm or > 9 cm
What is class 1 of the mandibular protrusion test?
Patient can move lower incisors past upper incisors and bite the upper lip
What is class 2 of the mandibular protrusion test?
Patient can move lower incisors in line with upper incisors
What is class 3 mandibular protrusion test?
Pt cannot move lower incisors past upper incisors
