<prompt> Difference in trajectory between inspiratory loop and the expiratory loop in the curve is due toDifference in alveolar pressure during inspiration and expirationDifference in conc, of surfactant during inspiration and expirationDifference in airway resistance during inspiration and expirationInspiration is active and expiration is passive  <response>: Ans. b Difference in conc, of surfactant during inspiration and expirationRef - Boron, Medical physiology, 2nd ed p.634Important 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 DVDPThe lung volume at any given pressure is greater during expiration than during inspirationCompliance is greatest at mid pressure range 