Describe the respiratory and cardiovascular effects of applying 10 cm of PEEP (positive end-expiratory pressure) to a healthy mechanically ventilated adult.
This topic has been asked previously. It was expected candidates could detail the impact of PEEP on a variety of respiratory parameters such as lung volume, dead space, arterial pO2 and intrapleural pressure. The cardiovascular consequences are well described including the effect on cardiac output, blood pressure and oxygen delivery.
The physiological impact of lower levels PEEP in a young healthy person is different to that often seen in the critically ill and this was not appreciated by most candidates.
The college did ask about the effects on a "healthy mechanically ventilated adult", which basically means you can't spend half a page discussing how PEEP is beneficial in the setting of left heart failure, or how it reduces inspiratory effort in a patient with bronchospasm and gas trapping.
Respiratory effects of positive pressure ventilation:
Cardiovascular effects of positive pressure ventilation:
Other organ system effects of positive pressure ventilation:
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.