We have elucidated the mechanism through which Spontaneous Airway Pressure Release Ventilation (S-APRV) is induced during high air/orygen flow through a small minitracheostomy tube into the trachea, without resorting to mechanical ventilation. By direct transtracheal fiberoptic visualization, we observed spontaneous closure of the glottic opening, followed by passive inflation of the lungs through flow of air/oxygen into the trachea. Expiration followed immediately upon opening of the glottis. Those observations have been confirmed by non-invasive ultrasonic imaging. It is important that both effort of breathing, and work of breathing are reduced by well over 90%, S-APRV does not require tracheal intubation, vocalization is preserved, oral feeding is not interfered with, and patient mobility is minimally impaired. Continuing studies explore factors that contribute to nosocomial pneumonia in patients on mechanical ventilation. All studies are conducted on anesthetized, paralyzed sheep, intubated, and on mechanical ventilation for 3 days. No antibiotics are used. Control sheep were intubated and the head held angled upward (as in the human), suctioned as needed. For study sheep, head and tracheal tube were maintained horizontal, and there was no suctioning. All sheep in the control group showed extensive bacterial colonization of the tracheo-bronchial tree and lungs, with abnormal chest X-rays, and autopsy findings of pneumonia. The water traps remained for the most part clear of mucus. All sheep in the study group remained healthy, with normal chest X-ray films, and autopsy findings. Mucus and tracheobronchial secretions accumulated spontaneously in the water trap. We conclude that orientation of tracheal tube (and head) during mechanical ventilation can avert pulmonary aspiration (invasion) of orotracheal or gastric contents, and lead to spontaneous clearance of tracheobronchial secretions, without need for periodic tracheal suctioning in this sheep model.
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