Positive pressure ventilation: what is the real cost?

Abstract

Positive pressure ventilation is a radical departure from the physiology of breathing spontaneously. The immediate physiological consequences of positive pressure ventilation such as haemodynamic changes are recognized, studied, and understood. There are other significant physiological interactions which are less obvious, more insidious, and may only produce complications if ventilation is prolonged. The interaction of positive pressure with airway resistance and alveolar compliance affects distribution of gas flow within the lung. The result is a wide range of ventilation efficacy throughout different areas of the lung, but the pressure differentials between alveolus and interstitium also influence capillary perfusion. The hydrostatic forces across the capillaries associated with the effects of raised venous pressures compound these changes resulting in interstitial fluid sequestration. This is increased by impaired lymphatic drainage which is secondary to raised intrathoracic pressure but also influenced by raised central venous pressure. Ventilation and PEEP promulgate further physiological derangement. In theory, avoiding these physiological disturbances in a rested lung may be better for the lung and other organs. An alternative to positive pressure ventilation might be to investigate oxygen supplementation of a physiologically neutral and rested lung. Abandoning heroic ventilation would be a massive departure from current practice but might be a more rationale approach to future practice.

The quality of the surgical field during functional endoscopic sinus surgery—The effect of the mode of ventilation—A randomized, prospective, double‐blind study

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A Model for Educational Simulation of Hemodynamic Transitions at Birth

“…To reproduce these conditions, a few adaptations in scripted parameters were needed: 1) matching to reported timeline; 2) representation of artificial ventilation with a positive average intrathoracic pressure of ϩ2 mm Hg (instead of Ϫ3 mm Hg). Intrathoracic pressure is positive throughout inspiration and remains slightly positive, whenever positive end-expiratory pressure is applied (15,37); and 3) delayed rise in DA resistance, corresponding to the initiation of ventilation with 100% oxygen. In these conditions, simulation results match the target data.…”