How we ventilate our standard patient in the OR

摘要

Anesthesiology is a highly complex medical speciality. The specialist must understand the physiology and physiopathology of the organ systems, must be familiar with the pharmacology of multiple drugs, must be competent in the skills of locoregional anesthesia and pain treatment, be au fait with current monitors and monitoring as well as a myriad of other aspects of practice in the operating room. Of all these, mechanical ventilation and ventilatory management of patients is clearly one of the most important issues. Despite this there are almost no recent statistics on how we ventilate our patients during general anesthesia and it is unlikely that there will be major differences around the world. Anesthesia machines are usually used with a circle breathing system or circuit, using volume controlled ventilation with tidal volume s(VT) between 8 and 12 ml/Kg of weight, a respiratory frequency from 10 to 15 breaths per minute and aiming at an EtCO_2 around 35 mmHg or 4.5-5 kPa with a I/E ratio of 1/2 and usually without PEEP. Today, we know that these settings are not appropriate for the majority of patients, in whom such a pattern will produce atelectasis, alter respiratory mechanics and gas exchange and may induce lung inflammation. A detailed review of pulmonary consequences of mechanical ventilation during general anesthesia have been recently published by Hans et al. These effects may contribute to postoperative respiratory complications and may affect morbimortality.