Respiratory Physiology Flashcards
Volume of air inspired or expired with each NORMAL breath
Tidal Volume
Volume that can be inspired above the tidal volume (used with exercise)
inspiratory reserve volume
volume that can be exhaled after expiration of tidal volume
expiratory reserve volume
volume in the lungs after maximal expiration
residual volume (not measured with spirometry)
Anatomic Dead Space
volume of conducting airways, ~150mL
Physiologic Dead Space
volume of lungs that doesn’t participate in gas exchange
Vd = Vt*[(PaCO2 - PeCO2)/PaCO2]
Vt is tidal volume
PaCO2 is pCO2 of alveolar gas or arterial blood
PeCO2 is pCO2 of expired air
Minute ventilation
tidal volume * breaths/min
Alveolar ventilation
(tidal vol - dead space) - breaths/min
volume remaining in lungs after tidal volume expiration
functional residual capacity (not measured by spirometry)
Volume of air that can be forcibly expired after a maximal inspiration
forced vital capacity
volume of air that can be expired in the 1st second of forced max expiration
FEV1, normal 80% of FVC
FEV1/FVC in obstructive lung disease
FEV1 is reduced more than FVC so it is DECREASED
ex. asthma
FEV1/FVC in restrictive lung disease
FEV1 and FVC are reduced so it is NORMAL or INCREASED
ex. fibrosis
external intercostals and accessory muscles
used during exercise and respiratory distress for inspiration
Abdominal muscle and internal intercostals
expiratory muscles in exercise or airway resistance like asthma
the distensibility of the lungs and chest wall, is inversely related to elastance
compliance of respiratory system
alveolar pressure - intrapleural pressure
transmural pressure of lung
hysteresis
inflation of a lung follows a different curve than deflation
At FRC, collapsing force of chest wall and expanding force of lung pressures are:
equal and opposite, thus the lung-chest wall system neither wants to collapse or expand
Pneumothorax
air is introduced into the intrapleural space, intrapleural pressure becomes equal with atmospheric pressure and lung collapses while chest wall expands
disease with increased lung compliance and lungs expand
emphysema, higher FRC
disease where lung compliance is decreased and tendency for lungs to collapse is increased
fibrosis, lower FRC
small alveoli
high colapsing pressures, need higher amounts of surfactant
LaPlace Law on Alveoli
P = (2T)/r
P is collapsing pressure (pressure to alveoli open)
T is surface tension
r is radius
dipalmitoyl phosphatidylcholine
main component of surfactant used to reduce surface tension, increases compliance, esp in small alveoli
starts being produced at week 24
Major site of airway resistance
medium-sized bronchi (not small airways because of parallel arrangement)
At rest before inspiration begins
- alveolar pressure
- intrapleural pressure
- Lung Volume
Alveolar pressure - atm pressure, said to be zero
intrapleural pressure is negative
lung volume is FRC
During Inspiration
- alveolar pressure
- intrapleural pressure
- Lung Volume
As lung lung increases, alveolar pressure will decrease to less than atm pressure (negative) allowing air to enter
intrapleural pressure becomes more negative
lung volume FRC + TV
During expiration
- alveolar pressure
- intrapleural pressure
- Lung Volume
alveolar pressure greater than atm pressure (more positive) so air flows out of lungs
intrapleural pressure is returns to normal (negative) unless it is forced expiration then it is (+) to squeeze out air
lung volume returns to FRC
pursed lips
COPD, to prevent airway collapse
decreased FEV1/FVC
COPD and asthma, also have increased FRC
pink puffers
emphysema, have mild hypoxemia and normocapnia
air trapping so barrel chested