Difference in trajectory between inspiratory loop and the expiratory loop in the curve is due to

Ans. (b) Difference in conc, of surfactant during inspiration and expiration(Ref - Boron, Medical physiology, 2nd ed p.634)Important points to be noted in compliance curve are:The curve has inspiratory and expiratory componentsNote that the inspiratory and expiratory compliance curves do not coincide. This difference is called hysteresisThe difference between the inflation and the deflation paths--hysteresis--exists because a greater transpulmonary pressure is required to open a previously closed airway, owing to a deficit of surfactant at the air-water interface, than to keep an open airway from closing, reflecting abundant surfactantCompliance is the slope DV/DPThe lung volume at any given pressure is greater during expiration than during inspirationCompliance is greatest at mid pressure range