Describe the physiological consequences of positive end expiratory pressure.
Points required included a definition of PEEP, both intrinsic and extrinsic.
The important physiological consequences that need to be discussed are respiratory including
increased FRC, increased compliance and decreased work of breathing.
Cardiovascular consequences include decreased venous return and subsequently decreased
cardiac output and an increased pulmonary vascular resistance.
Renal consequences include decreased renal blood flow and increased ADH
Effects on intra-abdominal pressure, hepatic blood flow and the beneficial effects in cardiac
failure earned marks.
Reference: Nunn 6th edition p. 431.
The question did not specifically ask for a definition, let alone a definition of intrinsic PEEP, and so the trainees would have been quite surprised to find this among the essential points expected of a passing answer. In spite of these hidden gems, 40% seem to have passed.
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.