Glottic-modulated lung ventilation during continuous transtracheal gas insufflation: an experimental study.

We investigated a new method of pulmonary ventilation that included a minitracheostomy, a reverse thrust catheter to deliver continuous flow of gas to the carina, and a threshold valve to avoid lung overinflation. In six lightly sedated healthy sheep, at a continuous flow of 5, 10, or 15 L/min and a threshold valve of 5, 10, 15, or 20 cm H(2)O, we observed a novel respiratory pattern that was characterized either by active lung inflation followed by passive and prolonged inspiratory hold (mixed pattern) or by an absence of all active inspiratory effort and only passive inflation of the lungs (passive pattern). We correlated airway pressure changes with direct visualization of the glottic opening through a fiberoptic bronchoscope. We measured airway pressures at the level of the carina, the subglottic level, and in the pleural space, and respiratory events were monitored through inductive plethysmography. An increase in continuous flow, threshold valve, or both resulted in 1) an increase in glottic breathing; 2) a decrease in respiratory rate, with a decrease in inspiratory pleural pressure excursion; or 3) an increased inspiratory/expiratory ratio and mean airway pressure. During transtracheal gas insufflation, as in this study, a novel respiratory pattern evolved that was modulated by the glottis, accompanied by a decreased effort of breathing; coughing and swallowing remained, and vocalization remained unimpaired.