Week 3: Respiratory physiology Flashcards
- Breathing efforts (respiratory rhythm) begin in _______.
- _________ lung development.
- Surfactants are produced after ____-____ weeks gestation by ________ _________.
- Utero
- Embryonic
- 26 to 28; type II pneumocytes
- As the neonate passes through the birth canal during vaginal delivery, much of the fluid is expelled via upper airways.
- Residual drains through _______ and ________ channels in the first day of life.
lymphatic and pulmonary
- The abrupt transition to extratuterine gas exchange at birth involves rapid ___________ of the lungs, increased ___________, and initiation of a ____________.
- This change results in: a functional closure of the _________.
- expansion; pulmonary blood flow, regular respiratory rhythm.
- foramen ovale
- Breathing is regulated by a complex system of ________ and _________ receptors.
- The infant has a very _________ chest wall which results in a tendency to ____________ with general anesthesia.
- peripheral; central
- compliant; atelectasis
- _________ stabilizes the alveoli and prevents their collapse on expiration. Reducing the surface tension also makes it easier to “________” the alveoli.
- _________ is a critical component of surfactant in the lung, and is produced by type II pneumocytes, beginning around _____ weeks gestation and continuing until ____-___weeks gestation.
- Surfactant; re-recruit
-Lecithin; 22; - 35 to 36
- Lecithin production is measured by determining the ____________ ratio in amniotic fluid.
- The L/S ratio measures lung maturity and predicts __________.
- Lecithin/sphingomyelin (L/S)
- ## Respiratory distress syndrome (RDS).
The L/S ration is generally
- <1 until ______ weeks gestation;
- 2 at ________ weeks gestation; and,
- _____ to _____ by full-term.
- 32
- 35
- 4 to 6
- Preterm infants with a lack of surfactant suffer from ______.
- Typically, the parturient receives ___________ in an effort to accelerate the biochemical processes in the lung responsible for maturation.
- Additionally, exogenous surfactant therapy is administered at delivery via an _______ at birth and repeated in ________ hours in the NICU.
- Respiratory distress syndrome
- corticosteroids
- ETT; 12
Periop assessment
Risk factors associated with increase risk of perioperative events
The small size of the peripheral airways may predispose the child to obstructive lung diseases such as ____________.
- History- Uri in previous 2 weeks,
- Wheezing,
- Cough,
- Eczema,
- Family history,
- Smoke exposure,
- Gestational age,
- Chronic disease (is the asthmatic child controlled with therapy, etc).
premie at higher risk up to 2y/o
bronchiolitis
Pulmonary function testing
- Highly dependent upon patient cooperation.
- __________ studies are often conducted on children to determine efficacy of treatment (i.e., asthma).
- Maximum expiratory and inspiratory flow-volume curves are useful for determining the site and nature of airway obstruction (i.e., fixed vs variable; extra vs intrathoracic).
- Spirometric
Perioperative triggers:
Children with a recent or current URI have an increased incidence of:
- Perioperative laryngospasm,
- Bronchospasm,
- Arterial hemoglobin desaturation,
- Severe coughing, and
- Breath holding,
- Atelectasis,
- Respiratory failure compared with uninfected children.
Upper respiratory tract infection
Elective surgery is usually postponed for children with more severe symptoms that include at least one of the following: (4)
- Mucopurulent secretions
- Lower respiratory tract signs (e.g., wheezing) that do not clear with a deep cough
- Pyrexia >100.4°F (38°C)
- Change in sensorium (e.g., not behaving or playing normally, not been eating properly)
Upper respiratory tract infection
- The optimal time when an anesthetic can be given to a child after a **URI ** without increasing the risk of adverse respiratory events remains contentious, but most clinicians wait _____ to _____ weeks after resolution of the URI before proceeding.
- A child with an _________ URI who is afebrile with ______ secretions and is otherwise healthy may proceed with surgery as planned.
- The decision becomes more complicated when the uri is between mild and severe in terms of severity.
- 2-4
- uncomplicated; clear
Lower airway disease
- In infants and children up to 18 months of age, ____________ is a very serious and common viral infection that infects the lower respiratory tract
- Other viruses include:
- respiratory syncytial virus (RSV)
- Parainfluenza virus,
- Adenovirus, and
- Human metapneumovirus
Croup or laryngotracheobronchitis, defined as acute inflammation of the airway (below the vocal cords), has been attributed primarily to ___________ as well as to _________.
- parainfluenza virus,
- adenovirus
- Asthma is one of the most common chronic diseases of childhood, affecting an estimated more than 6 million children in the United States
- Working definition of asthma is a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, _________, _________, and __________ of the airways
- airway obstruction, inflammation, and hyperresponsiveness
Clinical expressions of asthma include:(4)
Severe respiratory distress can occur during acute exacerbations and may be characterized by: (7)
- Wheezing
- Chest tightness or discomfort
- Persistent dry cough (chronic cough is most common manifestation)
- Dyspnea on exertion
- Chronic inflammation
- Chest wall retraction
- Accessory muscles use
- Respiratory failure and death
- Prolonged expiration
- Pneumothorax
- Airway remodeling
Asthma
- Children should continue their regular medications before anesthesia
- ________ has been reported to be a safe premedication for asthmatics
- ________ is the traditional choice of intravenous (IV) induction agent in children with severe asthma
- _________ before or after induction are helpful.
- _________ is associated with an increased risk of bronchospasm compared with sevoflurane or isoflurane, and because it can increase airway resistance in children, should be avoided in asthmatics
- Midazolam
- Ketamine
- Inhaled b-agonists
- Desflurane
Bronchospasm
First-line treatment for bronchospasm involves removing the triggering stimulus (if possible)
Interventions:
All children who experience anything more than minor bronchospasm should also receive ____________.
- Deepening anesthesia,
- Increasing the fraction of inspired oxygen (FIO2) if appropriate,
- Decreasing the positive end-expiratory pressure (PEEP),
- Increasing the expiratory time to minimize alveolar air trapping.
- Inhaled b-agonists
Corticosteroids
Intraoperative Bronchospasm S/S: (7)
- Polyphonic expiratory wheeze
- Prolonged expiration
- Active expiration with increased respiratory effort
- Increased airway pressures
- Slow upslope of end-tidal CO2 monitor waveform
- Increased end-tidal CO2
- Hypoxemia
In severe status asthmaticus, ventilation strategy focuses primarily on achieving adequate __________, rather than attempting to normalize ________ at the potential cost of inducing pulmonary barotrauma.
oxygenation; PaCO2
Cystic fibrosis
- is an autosomal _________ disorderinvolving a dysregulation of __________ and other ion fluxes.
- Multisystem presentation: a disruption of electrolyte transport in the epithelial cells of the: (7)
The clinical outcomes are variable.
- recessive, chloride
- of the:
- Biliary tree
- Intestine
- Pancreatic ducts
- Airways
- Sweat ducts
- Vas deferens
Cystic Fibrosis
S/S (7)
causes:
- Increased sweat chloride concentrations,
- Viscous mucus production,
- Lung disease,
- Intestinal obstruction,
- Pancreatic insufficiency,
- Biliary cirrhosis,
- Congenital absence of the vas deferens.
Cystic Fibrosis
Recurrent exacerbations are associated with: (10)
- Airway obstruction,
- Bronchiectasis,
- Emphysema,
- v/q mismatch,
- Hypoxemia,
- Hemoptysis
- Pneumothorax secondary to bullae formation.
- End stage cor pulmonale.
- Malnutrition (pancreatic insufficiency)
- Hepatic dysfunction
- Hyperventilation is compensatory.
- Obstructive pattern
Cystic fibrosis
- _______ and ________ are good predictors of survival.
- Inquire about frequency of infections, hospitalizations, effectiveness of bronchodilators.
- Exercise tolerance and physical fitness
Sickle cell disease
- SCD is an inherited ________
- Point mutation on chromosome ________ which codes for production of hemoglobin _____ instead of hemoglobin ______.
- hemoglobinopathy
- 11
- s; a
Sickle cell disease
Clinical features of the disease include:
Mean life expectancy just over ______ decades.
- Splenic infarction
- Acute episodes of pain
- Renal insufficiency
- Acute and chronic pulmonary disease
- Hemorrhagic and occlusive stroke
3
Sickle Cell Disease
- Acute chest syndrome (ACS) is an _____________ caused by SCD.
- ACS is a risk factor for _______.
- Precipitated by:
- acute lung injury
- SCLD
- Infection,
- Fat embolism,
- Pulmonary infarction,
- Surgery.
Sickle Cell Disease
Diagnostic criteria include of acute chest syndrome (ACS):
- A new ___________ involving at least one lung segment on the radiograph (excluding atelectasis)
- combined with one or more symptoms or signs of: (5)
- pulmonary infiltrate;
- Chest pain
- Pyrexia greater than 101.3°F (38.5°C)
- Tachypnea
- Wheezing, or
- Cough.
Sickle cell disease
- Children with scd who have experienced a _______ are at a high risk for perioperative complications.
- Risk factors of SCD:
- stroke
Therapy is still evolving
- Male gender,
- Low hemoglobin,
- Hypertension and
- Genetic polymorphisms.
Sickle Cell Disease
- Children with SCD frequently develop postoperative ________.
- ______ management can be difficult in these children.
- Large doses of opioids can depress ventilation and cause atelectasis.
- Incentive spirometry can prevent the development of atelectasis and pulmonary infiltrates
- Atelectasis
- Pain
Regional analgesia, supplemental nonopioid analgesics, prophylactic incentive spirometry, early mobilization, and good pulmonary toilet may decrease the incidence of atelectasis and ACS
Sickle Cell Disease
- Treatment of ACS is focused on supporting gas exchange.
- Supplemental oxygen, noninvasive ventilatory support such as ________, or intubation and mechanical ventilation are indicated by the degree of dysfunction.
- _________, incentive spirometry, and chest physiotherapy may be useful in preventing disease progression
- Perioperative transfusion goal is hematocrit of _______%
- CPAP
- Bronchodilators
- 30
Respiratory Physiology
Neonates are historically considered “obligate _______ breathers”.
The ability to breathe through the _______ when the nares are obstructed is age dependent.
- nose
- mouth
This may present a challenge when attempting to mask ventilate infants.
Respiratory Physiology
Functionally, the airway is most narrow at the level of the ________, just below the vocal cords.
The cricoid is the only ________ ring of cartilage In the laryngotracheobronchial tree.
cricoid cartilage;
complete
Respiratory Physiology
- Proximity of the tongue base to the more ____________ makes visualization of laryngeal structures more difficult.
- Use a _______ laryngoscope blade
- superior larynx;
- straight
Respiratory Physiology
- Neonates born via cesarean section do not experience the same thoracic squeeze and, therefore, retain more fluid in the lungs.
- They may experience:
transient respiratory distress (transient tachypnea of the neonate).
- __________ occur more commonly during the neonatal period due to the lack of surfactant, which stabilizes the alveolar matrix.
Pneumothorax
Respiratory Physiology
Periodic breathing ( rapid ventilation alternating with periods of apnea lasting ____ to ___ seconds) usually ceases by ____-____ weeks postconceptual age.
5 - 10;
44 - 46
Brief apneic spells (< _____ seconds) in the preterm infant may be accompanied by _________ (______ beats/min) and generally responds to tactile stimulation or bag-mask ventilation.
______, _______ or ________ may also be used.
- 20;
- bradycardia <80
- CPAP, caffeine, aminophylline
Larynx is adjacent to
C3 in _________,
C4 in ________, and
C5 in ________.
The high cervical level of the larynx means the “___________” will not help you visualize the glottis as it does in the adult.
Consider a “________” to help align your view during direct laryngoscopy.
- premature neonates
- infants
- adults.
- sniffing position
- shoulder roll
- The epiglottis in the infant is ______, _______ shaped, and ________ from the axis of the trachea,
- which contrasts with that in the adult, which is ______ and ______, and its axis is _________ to the trachea.
The shape of epiglottis makes it more difficult to directly lift in the _____ and _______ with the tip of a laryngoscope blade.
- narrow, omega, angled away
- flat and broad; parallel
- neonate and infant
Review
Respiratory Physiology
- Closing volumes are _________ in infants and young children. (This is when the alveoli collapse, thus impairing gas exchange.)
- As FRC __________ under anesthesia, the alveolar-arterial oxygen tension gradient, ___________.
- This intraoperative (and postoperative) decrease in FRC may be attenuated by using ________.
- greater
- decreases , increases
- CPAP
Respiratory Physiology
Work of breathing is controlled by the muscles of respiration, which generate the force necessary to overcome the _________, and the __________ of the lungs and chest wall.
resistance to airflow; elastic recoil
Sensory and motor innervation
Two branches of the vagus nerve:
________ - ________, supply both sensory and motor innervation to the larynx.
The recurrent laryngeal and the superior laryngeal nerves
The superior laryngeal nerve has two branches:
The internal branch, which provides:
and
The external branch, which supplies:
- sensory innervation to the supraglottic region.
- motor innervation to the cricothyroid muscle.
The recurrent laryngeal nerve provides sensory innervation to the _______________ and motor innervation to ______________.
- subglottic larynx
- all other laryngeal muscles
Airway obstruction during anesthesia
- Frequently related to:
- Primarily at the level of the:
- Loss of muscle tone of the pharyngeal and laryngeal structures rather than apposition of the tongue to the pharyngeal wall.
- Soft palate and epiglottis.
Sniffing position, CPAP, chin lift, jaw thrust, recovery position.
Avoid dynamic airway collapse seen during vigorous crying.
Use caution with sedatives and opioids.
Laryngospasm
Contraction of intrinsic laryngeal muscles alters the position and configuration of tissue folds. Influencing respiration, Valsalva, laryngospasm, swallowing and phonation.
?
Laryngospasm is accompanied by an inspiratory effort which separates the vocal from the ___________ (false vocal cords).
In contrast to forced glottic closure, the ________ and the _________ muscle don’t contract.
This allows the upper portion of the larynx to be left partially open during mild laryngospasm resulting in ____________.
- vestibular folds
- thyroarytenoid and the thyrohyoid
- high pitched inspiratory stridor
Airway management
Proper sizing of OPA
Airway management
Nasopharyngeal airways (sized by measuring distance from _______ to _________)
Tracheal intubation (straight blade is used traditionally)
Optimal positioning
nare; angle of the mandible
Miller/ Wis-hipple/Macintosh
Preterm
Neonate
Neonate - 2 yrs
2 - 6 years
6 - 10 years
> 10 years
ETT size ID uncuffed
1000g
1000 - 2500g
Neonate - 6 months
6 months - 1 year
1-2 years
>2 years
Uncuffed ETT formula
2.5 = 1000g
3.0 - 1000 = 2500g
3.0 - 3.5 = Neonate - 6 months
3.5 - 4.0 = 6 months - 1 year
4.0 - 5.0 = 1-2 years
(age (yrs) + 16)/4 = >2 years
ETT size ID cuffed
1000g
1000 - 2500g
Neonate - 6 months
6 months - 1 year
1-2 years
>2 years
1000g
1000 - 2500g
3.0 - 3.5 = Neonate - 6 months
3.0 - 4.0 = 6 months - 1 year
3.5 - 4.5 = 1-2 years
(age (yrs)/4)+3 = >2 years
Down syndrome = Smaller ET
Cardiac disease = Larger ET
Three axes for intubation:
- pharynx (P)
- mouth or oral (O)
- trachea (T)
Airway management
Air leak (20cm H2o)
Insertion distance (______ x _____)
RAE tubes can be problematic
ID of ett X 3
Complications of intubation
Postextubation croup from :
- ETT is too large,
- Repeated intubation attempts - Traumatic intubation,
- History of croup,
- Coughing on ett,
- Age ____-___ yrs,
- Surgery >1 hr,
- Position other than supine.
Treatment:
1-4 yrs
Treatment:
- nebulized epinephrine,
- dexamethasone.
Subglottic stenosis results from (7)
Prolonged intubation,
Large ett,
Traumatic intubation,
Trauma,
Gastric reflux,
Hypotension,
Sepsis;
It involves ischemic injury secondary to the lateral wall pressure from ETT
Respiratory Principles
- Infants require ________ controlled ventilation when intubated.
- They also require a _______ respiratory rate and __________ during mask ventilation.
- Transpulmonary pressures are similar in healthy infants, children and adults.
- pressure
- rapid; positive end expiratory pressure
Respiratory alterations under anesthesia
- Decreased spontaneous ventilation.
- FRC is reduced during GA with or without neuromuscular block.
- Utilize PEEP.
- During controlled ventilation, V/Q mismatching is greatly increased.
- Deadspace assumes considerable significance.
Ventilatory guidelines
For infants, start with a
- Rate of ______ per minute
Peak inspiratory pressure (PIP) - determined by adequate chest wall movement. This will vary with clinical circumstance.
- An infant weighing less than 1500 grams: ___ -____ cm H2O.
An infant weighing greater than 1500 grams: ____-_____cm H2O. - Positive end expiratory pressure (PEEP): start with 4 cm of H2O; may increase to 5-6 cm, if FiO2 > 0.90.
- FiO2: 0.4 to 1.0, depending on the clinical situation.
Inspiratory time: ___-_____ seconds
- 30
- 16-28; 20-30
- 0.3-0.5
Lung volumes in the infant tend to be similar to adult lung volumes.
TLC =
FRC = _____ ml
Tidal volume = ____- ___ ml/kg
Dead space is about _____% of tidal volume
TLC = 160ml
FRC= 80ml
Tidal Volume= 6-7 ml/kg
Dead space= 30%
Respiratory considerations postoperatively
-Preterm and former preterm infants up to ________ weeks postconceptual age, particularly those with anemia, are at risk for postoperative apnea, even if they are apnea-free at the time of anesthesia.
These patients should:
- 60
- stay overnight following surgery for observation; i.e., a “23-hr OBS.”
Table 13.1
Pulmonary Function Test Uses in Children
- Establish pulmonary mechanical abnormality in children with respiratory symptoms
- Quantify the degree of dysfunction
- Define the nature of pulmonary dysfunction (obstructive, restrictive, or mixed obstructive and restrictive)
- Aid in defining the site of airway obstruction as central or peripheral
- Differentiate fixed from variable and intrathoracic from extrathoracic central airway obstruction
- Follow course of pulmonary disease processes
- Assess effect of therapeutic interventions and guide changes in therapy
- Detect increased airway reactivity
- Evaluate the risk of diagnostic and therapeutic procedures
- Monitor for pulmonary side effects of chemotherapy or radiation therapy
- Aid in predicting the prognosis and quantitating pulmonary disability
- Investigate the effect of acute and chronic disease processes on lung growth
Syndromes
Pierre Robin Sequence
- Micrognathia
- Glossoptosis
- Cleft palate
As it advances w/ age it gets better.
“micrognathia” = mandibular hypoplasia (lower jaw smaller than usual
Syndromes
Goldenhar syndrome
- Micrognathia (unilateral)
- Cervical dysfunction
Treacher Collins Syndrome
- Micrognathia
- Small oral opening
- Zygomatic Hypoplasia
Apert syndrome
- Micrognathia
- Macroglossia
- Limited cervical motion
- Midface hypoplasia
Hunter and hurler syndromes
- Cervical dysfunction
- Macroglossia
Beckwith-Wiedemann syndrome
- Macroglossia
Regresses with age
Freeman- Sheldon syndrome
AKA
- Circumoral fibrosis
- Microsotomia
- Limit cervical motion
“Whistling face”
Down syndrome
- Atlantooccipital abnormalities
- Small oral cavity
- Macroglossia
Klippel-Feil Syndrome
- Cervical fusion
Hallermann-Streiff syndrome
Microstomia
- Micrognathia
- Displacement of TMJ
Arthrogryposis
Cervical dysfunction
- Torticollis
- Hypoplastic mandible
Edwards syndrome
- Micrognathia
Fibrodysplassia ossificans progressiva
- Cervical motion limited
Cri-du-chat syndrome
- Micrognathia
- Laryngomalacia
Oral airway size No. and color
Neonatal
Infant
Child
Small adult
Adult
Neonatal= 00 (Pink)
Infant= 0 (Light blue)
Child= 1 (Black)
Small adult = 2 (White)
Adult = 3 (Green)
LMA sizes
● <____ kg →
● ______ kg →
● ______ kg →
● ______ kg →
● _______ kg →
● ______ →
● ______ kg →
● >______ kg →
● <5 kg → 1
● 5-10 kg → 1.5
● 10-20 kg → 2
● 20-30 kg → 2.5
● 30-50 kg → 3
● 50-70 kg → 4
● 70-100 kg → 5
● >100 kg → 6
- Age-based formula to determine the correct uncuffed ETT size:
- Cuffed ETT formula
- Example: 4 year old + 16= 20/4 = _____ uncuffed ett
- To determine the appropriate cuffed ETT size, subtract ________
- ([age in years + 16]) divided by 4 = uncuffed ETT
- ([age in years] divided by 4) + 3 = cuffed ett
- 5
- 0.5
Pediatric Leak Test for ETT
- A leak around the ETT is necessary to reduce the risk of edema and obstruction.
- The leak should be documented on anesthesia record (Example: write “+ leak at 22 cm H20”)
Two types:
- Minimal Leak Test (MLT)
- Minimal Occluding Volume (MOV), which requires a manometer.
Unexpected difficult Peds intubation
Difficult airway
- Formulate a plan with several contingencies.
- Consider ___________
- Ketamine, midazolam, atropine or glycopyrrolate, dexmedetomidine are reasonable options for sedation.
- ____________ is less desirable
- Document
- Prepare for extubation shortly after the airway is secured
- Cricothyroidotomy vs surgical airway vs anterior commissure scope
- Become comfortable with videolaryngoscope, fiberoptic bronchoscope and other equipment available at facility with a normal airway first!
YOU DO NOT DO A CRICOTHYROIDOTOMY ON A CHILD UNDER THE AGE OF _______ RISK OF DAMAGE TO NERVES, ARTERIES AND VEINS
- Spontaneous ventilation
- Topicalization
5
LMA
Various insertion techniques varying amongst brands and practitioners.
Should still see outward movement with inflation after placement. If not, reconsider positioning of LMA
Lma can still damage upper airway structures, recurrent laryngeal nerve, hypoglossal nerves.
Use caution with lma placement in infants.
