Alveolar falls (with SDs) in oxygen tension (expressed in percent) and in total lung compliance as the difference between first and last measurements during constant ventilation. Three successive inflations restore previous levels of compliance (with the first inflation) and oxygen tension (in steps). Reprinted with permission from Bendixen HH, Hedley-Whyte J, Laver MB: Impaired oxygenation in surgical patients during general anesthesia with controlled ventilation: A concept of atelectasis. New Engl J Med 1963; 269:991–6. Copyright © 1963 Massachusetts Medical Society.

John Hedley-Whyte, M.D., F.A.C.P., F.R.C.A., M.R.C.S.