Critical Closing volume is
Ans is 'd' i.e. Close to Residual Volume [Ref: Physiologic Basis of Respiratory> Disease by Qutayba Hamid, Joanne Shannon, James Martin pi37; Surgical Critical Care and Emergency Surgery: Clinical Questions and Answers By Forrest O. Moorep7; http://www.ccmtutorials.com/rs/peep/page4.htmCritical closing volume is the minimum volume and pressure of gas necessary to prevent small airway collapse. It is somewhat near Residual volume.Under pathological conditions when CCV exceeds Functional Residual Capacity (FRC), alveolar collapse occurs.FRC is = Residual volume + Expiratory reserve volume
Volume at the end of forceful expiration
Volume at the end of forceful inspiration
Volume remaining after Functional Residual Capacity is measured
Close to Residual Volume
Mechanics of Respiration