Breathing pattern and arterial blood gases during Nd-YAG laser photoresection of endobronchial lesions under general anesthesia: Use of negative pressure ventilation. A preliminary study

Study objective: To evaluate the efficacy of negative pressure ventilation (NPV) in avoiding or reducing apneas and related hypoxemia and respiratory acidosis during laser therapy (LT) of endobronchial lesions. Design: A prospective, controlled, randomized study. Setting: An operating theater of a respiratory endoscopy and laser therapy unit. Population and intervention: Twenty-seven consecutive patients referred to LT were entered into the study. Fourteen patients were randomly assigned to LT under general anesthesia and spontaneous assisted ventilation (control group) whereas in 13 cases, NPV by a poncho-wrap ventilator (NPV group) was added to the procedure. Measurements and results: The prevalence and the duration of apnea/hypopnea periods assessed by respiratory inductive plethysmography during LT were significantly reduced under NPV, compared to the control group. As compared to baseline, during LT, all control patients developed mild to severe hypercapnia (PaCO₂ ranging from 55 to 76 mm Hg) and respiratory acidosis (pH from 7.33 to 7.19), whereas only three patients undergoing NPV (23%) developed hypercapnia (PaCO₂ from 52 to 68 mm Hg) and related acidosis (pH from 7.29 to 7.21). Optimal oxygenation was achieved in all of the patients; nevertheless, patients under NPV needed a lower mean oxygen supply; five of them (38%) could be treated at a fraction of inspired oxygen of 0.21 for the whole procedure. Conclusion: NPV may be useful in reducing apneas during laser therapy under general anesthesia, thus reducing hypercapnia, related acidosis, and need of oxygen supplementation.