1. Respiratory Cycle and Mechanics Flashcards
How does residual volume (RV) change when moving from supine to seated?
RV stays the same
How does total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV) change with age?
TLC stays the same.
FRC and RV increases.
What is the barometric pressure of the air?
760 mm Hg
What is the intrapleural pressure P(PL) at rest?
-5 cm H2O
What is the intrapleural pressure P(PL) during inspiration?
-8 cm H2O
What happens to alveolar pressure P(AVL) as the thoracic cavity increases?
Alveolar pressure decreases due to increase in alveolar size.
What is the transpulmonary pressure P(TP) and what is the normal value at rest?
P(TP) = P(ALV) - P(PL) P(TP) = 0 - (-5) = 5 cm H2O
What is alveolar pressure P(AVL) at rest?
0 cm H2O
How does one calculate minute ventilation V(E)? What is the normal value?
Tidal volume multiplied by frequency
Normal is 7,000 ml/min or 7 L/min
What is the difference between anatomic dead space, alveolar dead space, and physiological dead space?
Anatomic: space in respiratory system other than alveoli
Alveolar: alveoli that receive air, but not blood
Physiological: air that functionally doesn’t participate in gas exchange (important in disorders)
How does one calculate minute alveolar ventilation?
Subtracting dead space from tidal volume, then multiplying by frequency
What accounts for the difference pressure/volume curves for inhalation and exhalation (hysteresis)?
Surfactant reduces tension in smallest alveoli more than larger alveoli
How does fibrosis and emphysema effect compliance?
Fibrosis lowers compliance while emphysema increases it
What is the formula for airway resistance?
R = (8ηL) / (r^4)
How does the FEV1/FVC ratio change with obstruction and restriction?
Obstruction: ratio is decreased
Restrictive: ratio is increased, or stays the same
