SUMMARYThe supplying of oxygen to tissues, and the removal of gaseous wastes are quickly compromised once the chest has been surgically invaded. Of necessity the expansion of the lungs becomes one of a positive rather than a negative pressure process. Abnormal positioning of lobes of the lungs to facilitate exposure for surgery, reduced rate of respiration, atelectasis due to underinflation as well as diseased areas aggrevate the situation.Return of vascular flow to the heart is impaired by loss of negative pressure in the chest cavity. Blood flow through the pulmonary vasculature is impaired by anything that adds resistence. Life itself is very dependent on the delicate balance between hydrostatic and osmotic pressures within the pulmonary capillaries in order for there to be adequate oxygenization.Retention of CO2or undersupply of oxygen to tissues contribute to an acidotic state. This acidosis can accelerate a viscious shock cycle if not controlled.Body temperature must not be allowed to drop excessively without careful monitoring of all vital parameters. Motility of cillia along the respiratory tree is slowed by drop in temperature. Phagacytosis within the alveoli undoubtedly diminishes as the temperature drops or the tissues become dehydrated.The heart and respiratory rates are controlled by many autonomic mechanisms which, if interrupted, may need to be compensated for and which must be returned to body control at the end of surgery.The chest is not an area which should be entered with fear but with much respect for its contents and their functions. The surgeon should keep this well in mind and should thus enter the chest as though it were his own.