Describe the physiological consequences of Positive End-Expiratory Pressure
Most answers were quite brief and superficial. They simply did not cover enough of the required
knowledge base to gain a pass mark. A definition of PEEP is a useful way to start this answer and
this was missing in more than half the answers. Deficiencies in knowledge included even the
primary respiratory and cardiovascular effects of PEEP. Many candidates incorrectly concluded
that PEEP would increase afterload and decrease pulmonary vascular resistance. Some
candidates provided description of the cardiovascular effects of Valsalva, which was not part of
the question. It was expected candidates would also mention physiological effects on other
organ systems such as potential cerebral and renal effects.
This topic (Level 1) requires a detailed knowledge and candidates should read widely to gain the
depth of understanding required. The core material is covered in texts such as Nunn’s’ Applied
Respiratory Physiology and additional applied information can be found in a variety of texts such
as Textbook of Critical Care by Fink et al, Irwin and Rippe’s Intensive Care Medicine or Miller’s
Definition of PEEP:
Respiratory effects of positive pressure ventilation:
Cardiovascular effects of positive pressure ventilation:
Other organ system effects of positive pressure ventilation:
American College of Chest Physicians. "Society of Thoracic Surgeons. Pulmonary terms and symbols: a report of the ACCP-STS Joint Committee on Pulmonary Nomenclature." Chest 67 (1975): 583-93.
Oakes, Dennis L. Physiological Effects of Positive Pressure Ventilation. AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH, 1992. -this is somebody's Masters of Science thesis! They received their degree in 1992, but one expects that the fundamentals of physiology have remained the same since then.
Kumar, Anil, et al. "Continuous positive-pressure ventilation in acute respiratory failure: effects on hemodynamics and lung function." New England Journal of Medicine 283.26 (1970): 1430-1436.
Luce, John M. "The cardiovascular effects of mechanical ventilation and positive end-expiratory pressure." Jama 252.6 (1984): 807-811.
Morgan, Beverly C., et al. "Hemodynamic effects of intermittent positive pressure respiration." Anesthesiology 27.5 (1966): 584-590.