Effects of anaesthesia on respiratory mechanics
Anaesthesia has effects on both the mechanics of the respiratory system and pulmonary gas exchange. Thus, the respiratory system appears to be stiffer, i.e. the compliance is reduced, than in the awake state and the resistance to breathing is increased. The effects on gas exchange result in impairment of blood oxygenation and sometimes also in less efficient elimination of CO2. Several of the pioneering studies in this field were published in the 1950s [1–3]. During the forty years that have elapsed after these initial reports, there is increasing evidence that the changes in respiratory mechanics are the cause of gas exchange impairment. Thus, understanding respiratory mechanics during anaesthesia may guide in the understanding impaired gas exchange as well as in promoting techniques that counter the deterioration in gas exchange. This review will analyse the effects of anaesthesia on respiratory mechanics and the corresponding morphological correlates, and then relate gas exchange impairment to the anaesthesia-induced mechanical and morphological changes.
KeywordsLung Volume Functional Residual Capacity Respiratory Mechanic Recruitment Manoeuvre Muscle Paralysis
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