Negative pressure ventilation vs external high-frequency oscillation during rigid bronchoscopy - A controlled randomized trial

Study objectives: To compare the effectiveness of two modalities of externa l ventilation during rigid bronchoscopy: intermittent negative pressure ven tilation (INPV) and external high-frequency oscillation (EHFO). Design: Prospective, controlled, randomized, nonblinded study, Setting: University-affiliated hospital. Patients: Seventy patients undergoing interventional rigid bronchoscopy for tracheobronchial lesions were enrolled into the study. Interventions: Mechanical ventilation was performed by INPV or EHFO. When p ulse oximetry was < 90%, manually assisted ventilation was delivered, Measurements and results: Arterial blood gases were sampled preoperatively and intraoperatively. Most patients in both groups had normal intraoperativ e Paco(2) (mean, 43.6 +/- 11.8 min Hg under EHFO and 37.4 +/- 8.2 mm Hg und er INPV; p = 0.012), and acidemia occurred in 9 of 35 patients of EHFO grou p and in 2 of 35 patients of INPV group (p = 0.049), Hypercapnia (Paco(2) > 50 mm Hg) was observed in 10 patients under EHFO and in 2 with INPV (p = 0 .026). Intraoperative mean Pao(2) was similar (101.4 +/- 52.9 mm tig with E HFO and 124.2 +/- 50.3 min Hg with INPV; p = 0.07), but O-2 supply was diff erent (3.5 +/- 2/3 L/min during INPV and 8.5 +/- 6.2 L/min during EHFO; p < 0.001). Intraoperative hypoxemia (Pao(2) < 60 mm Hg) occurred in five pati ents with EHFO and two with INPV (p = 0.426). Three EHFO patients required manually assisted ventilation (mean, 0.2 +/- 0.9), but no INPV patient did (p = 0.142). Conclusions: External negative pressure ventilation appears to be a suitabl e choice during rigid bronchoscopy: both EHFO and INPV ensure effective ven tilation and comfortable operating conditions in the majority of patients, Some patients may receive inadequate ventilation with EHFO, developing resp iratory acidosis and requiring manually assisted ventilation. In comparison with INPV, EHFO requires a higher fraction of inspired oxygen.