TRANSTRACHEAL DELIVERY OF GAS DECREASES THE OXYGEN COST OF BREATHING

Transtracheally administered gases decrease inspired minute ventilatio n in both dogs and humans. To test if this is associated with a decrea se in the oxygen cost of breathing and to evaluate subsequent changes in the breathing pattern, we studied five patients with chronic respir atory diseases while they spontaneously breathed air and different flo ws of tracheally administered gases. In a blinded crossover design, th e gas consisted of either oxygen or air at 2, 4, and 6 L/min. Oxygen c ost of breathing was estimated by the calculation of pleural pressure- time index (PPTI). The pattern of breathing was evaluated utilizing th e tension time index for the diaphragm (TTdi). There were significant decreases in PPTI when the patients received 2, 4, and 6 L/min of tran stracheal oxygen or air TTdi also decreased as gas flow increased. Thi s drop was significant at 6 L/min flow for both gases. We conclude tha t transtracheally administered gas reduces the oxygen cost of breathin g. It also changes the respiratory pattern of the diaphragm to a less demanding pattern. This may offer an alternative form of treatment to rest overworked respiratory muscles.