Pathophysiological Changes in the Lungs During Extracorporeal Circulation

Abstract

An attempt has been made to determine the optimal method of managing the lungs during cardiopulmonary bypass. The chemical behavior (oxygen saturation, acid-base balance) of the pulmonary venous blood indicates (a) that static inflation of the lungs with either a gas mixture of high oxygen content or ambient air is sufficient to maintain a proper internal milieu for the pulmonary vasculature when the bronchial collateral flow is the sole pulmonary perfusate, and (b) that in adult human beings artificial respiration up to 2 L./min. is necessary when the pulmonary perfusate consists of the coronary venous blood in addition to the bronchial collateral flow. The effective application of the heart-lung bypass procedure in physiological investigation is depicted by the studies on metabolic rate of the lung tissues and the measurement of bronchial flow. It is estimated that the bronchial collateral flow amounts to 8.8 ml./ min. or 0.7 per cent of the total systemic flow, and that the oxygen consumption of the lungs averages 1.6 ml./min. or 1 to 2 per cent of the total metabolic rate in the open-chest dogs. The pulmonary compliance did not change following either passive deflation or static inflation, but is transiently reduced after artificial respiration.

Lung Management During Cardiopulmonary Bypass: Is Continuous Positive Airways Pressure Beneficial?

“…However, the ideal management for the non-functioning lungs during CPB remains controversial and in studies on animal preparations and in humans various methods have been used to assess pulmonary function. These include pulmonary artery pressure, static and dynamic lung compliance, intrapulmonary shunting, arterial oxygen tension and extravascular lung water [1][2][3][4][5][6][7][8][9][10][11][12][13]. The clinical significance and relative importance of these indices remains in doubt, and are confounded by anaesthetic, surgical and perfusion techniques (e.g.…”

Cardiopulmonary bypass—organ blood flow and metabolism in the pediatric patient

“…Weedn et al 103 in comparing standard intermittent ventilation, static inflation and deflation, saw no clinical differences in the three groups they studied, but found that the group with static inflation of the lungs had the least amount of histolologic damage. Cartwright et al, 104 in contrast, showed that assisted ventilation was superior in achieving appropriate acid-base balance of the lung tissue. Alternatively, others 95 ' 105 have determined that entry to the pleural space will result in decreased compliance and an increased alveolar-arterial oxygen gradient, but that this can be overcome with static hyperinflation.…”