Effects of different inspiratory gas flow patterns on thoracic compliance during respirator treatment

Nine patients under general anaesthesia and 26 intensive care patients undergoing respirator treatment were investigated with special reference to changes in compliance under the influence of different inspiratory gas flow patterns during intermittent positive pressure ventilation (IPPV). Pressure recordings were performed in the respirator tubings, in the trachea and in the oesophagus. Flow rate was measured with pneumotachography. Total compliance showed an increase with a decelerating flow compared to an accelerating flow in the anaesthetized group as well as in patients with low compliance and high resistance, and also in patients with chronic respiratory disease. These findings were explained by an inproved evenness in the distribution of gas in the greater airways during the inspiratory phase. A separation of total compliance into lung and chest wall compliance did not reveal any significant variation correlated to flow pattern. The change in compliance occurred within minutes and remained during a 30-minute setting period.