Respiratory Flashcards
Developmental stages of lung development
Embyronic, pseudoglandular, canalicular, terminal sac (saccular), aveolar and vasculature
Embyronic stage: GA development, structural devo, developmental abnormalities
0-5 weeks
ventral lung bud forms, asymmetric bronchi, 5 lobes, pulm vascular devo
problems: laryngeal cleft, tracheal stenosis, TEF, bronchogenic cysts
Pseudoglandular stage: GA development, structural devo, developmental abnormalities
5-16 weeks
branching up to terminal bronchi, broncho-pulm epithelium produces fluid, vasculature of aa & vv, separation of thorax & peritoneal cavity
problems: branching abn, CDH, congenital lobar emphysema, CPAM, pulm lymphangiectasia
Canalicular stage: GA development, structural devo, developmental abnormalities
16-25 weeks
respiratory bronchioles, prelim gas exchange unites, T2 pneumocytes -> T1
problems: pulm hypoplasia, surf deficiency, alveolar capillary dysplasia
Saccular stage: GA development, structural devo, developmental abnormalities
25-36 weeks
alveolar ducts, gas exchange via alveolar capillary membrane
problems: pulm hypoplasia, surf deficiency
Alveolar & vasculature stage: GA development, structural devo, developmental abnormalities
36+ weeks
alveoli increase in diameter, microvascular growth & vessel maturation
problems: surf deficiency, congenital lobar emphysema, pulm HTN
O2 content =
O2 content = O2 bound + O2 unbound
= [(1.34 x Hb) x O2 sat] + [(0.003) x paO2]
A-a gradient =
A-a gradient = pAO2 - paO2
= [FiO2 x (pB - H2O)] - paCO2/R - paO2
O2 delivery =
O2 delivery = CO x O2 content
O2 consumption =
O2 consumption = (blood flow x O2 content in arterial blood) - (blood flow x O2 content in venous blood)
= CO x (1.34 x Hb) x (arterial O2 sat - venous O2 sat)
SP A
Expressed early 3rd trimester
Tubular myelin and host defense
Sp B
Expressed at end of 1st trimester
Surfactant function
Tubular myelin
Surface adsorption of phospholipids
Surfactant administration in the setting of Sp B deficiency is ineffective
Sp C
Expressed at end of 1st trimester
Surfactant function
Surface adsorption of phospholipids
Sp D
Expressed last, after early 3rd trimester
Host defense
Anti oxidant
Surfactant lipid homeostasis
Laplace’s law
P = 2T / r
P is distending pressure or pressure needed to resist alveolar collapse
Boyle’s Law
P1V1 = P2V2
Hering Breuer inflationary reflex
Lung overdistention -> inspiration arrest
Hering Breuer deflation reflex
^RR with abrupt deflation of lungs
Chemoreceptors that sense CO2 changes
In the medulla, and actually more sensitive to H changes
Chemoreceptors sensitive to O2 changes
Carotid and aortic bodies (peripheral)
These are less sensitive in preterm infants and so they, instead of having initial hyperpnea and then decreased ventilation in term infants, preterm infants respond to hypoxemia with respiratory depression
Alveolar ventilation equation
VA = (TV - dead space) x RR
Bohr equation of physiologic dead space
Dead space V = TV x ((alveolar CO2 - expires CO2) / alveolar CO2)
In patients without significant venous-to-arterial shunts then arterial pCO2 represents the pCO2 of perfused alveoli
Physiologic dead space = TV x ((arterial CO2 - expires CO2) / arterial CO2)
Resistance equation
R = change in P (cm H2O) / change in flow (L/sec)
Normal is 40-55
Due to chest wall (1/4), airway (1/2), lung tissue (1/4)
Resistance relationships in laminar flow
Increased radius decreases resistance
Increased length increase resistance
Laminar flow unaffected my density of gas
R = (length x viscosity) / radius^4
