Question 12
- How can a decrease or an increase in resting lung volume affect bronchial responsiveness?
An increase in lung volume leads to greater lung recoil pressure and hence to greater distending pressures on intrapulmonary airways; conversely diminishing lung volume leads to a smaller distending force applied to the airway circumference. If the external airway surface area increases in proportion to lung volume (hence Fel/A = constant), the afterload to the contracting muscles is independent of lung volume. In man and dog maximal airway narrowing has been shown to increase as the lung is deflated.