Mechanics of breathing II Flashcards
What is the speed of the air through the airways proportional to?
→ pressure gradient between atmosphere and lungs
What is the equation for compliance?
→ compliance = Δ volume/ Δpressure
What is compliance?
→How easy it is to get the lungs to expand
What is transpulmonary pressure?
→The force required to expand the lungs
What is the transpulmonary pressure equation?
→Transpulmonary pressure (Ptp) = Alveolar pressure (Palv) - Intrapleural pressure (Pip).
What is the equation for airflow?
→ Pressure / Resistance
What happens as the airway radius decreases?
→The resistance increases and airflow decreases dramatically
What is the Hagen-Poiseuille equation?
→R = 8nl / πr^4
What happens when the lumen diameter increases?
→Increase in luminal area
→Decrease in resistance
→Increase in flow
What happens when the lumen diameter decreases?
→Decrease in luminal area
→Increase in resistance
→Decrease in flow
How does pattern of airflow affect resistance?
→Laminar flow - no resistance
→Turbulent flow - resistance and produces noise (wheezing)
What is FEV 1?
→Forced expiratory volume in 1 second
What is FVC?
→Forced vital capacity
How do you take into account different lung capacities?
→100 x FEV1/FVC = % of total lung capacity an individual can exhale in the first second
→Ratio of volume in 1 second to total capacity.
What happens to FVC and FEV1 in obstructive airway disease?
→The FVC is the same but FEV1 decreases
→Lung capacity is normal