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Acute oxygenation response to inhaled nitric oxide when combined with high-frequency oscillatory ventilation in adults with acute respiratory distress syndrome*

Mehta, Sangeeta MD, FRCPC; MacDonald, Rod RRCP; Hallett, David C. MSc; Lapinsky, Stephen E. MD, FRCPC; Aubin, Michael RRCP; Stewart, Thomas E. MD, FRCPC

doi: 10.1097/01.CCM.0000049953.86613.02
Clinical Investigations

Objective To prospectively evaluate the oxygenation effect of inhaled nitric oxide (INO) delivered during high-frequency oscillatory ventilation in adult patients with the acute respiratory distress syndrome and oxygenation failure.

Design Prospective, clinical study.

Setting Intensive care unit of a university teaching hospital.

Patients A total of 23 adults (14 women, 9 men, 44.9 ± 17.5 yrs, Acute Physiology and Chronic Health Evaluation II score of 28.6 ± 7.1) with acute respiratory distress syndrome (lung injury score, 3.5 ± 0.4) with Fio2 of ≥0.6 and mean airway pressure of ≥28 cm H2O.

Interventions INO was initiated at a dose of 5 ppm, and subsequently titrated according to a protocol, to determine the dose (5, 10, or 20 ppm) resulting in the greatest increase in Pao2/Fio2. Blood gas measurements were obtained 10–15 mins after initiation or any increase in INO dosage to assess the effect on Pao2/Fio2.

Measurements and Main Results Arterial blood gases and ventilator settings were recorded at four time points: during conventional ventilation just before initiating high-frequency oscillatory ventilation, during high-frequency oscillatory ventilation just before initiating INO, after 30 mins on the optimal dose of INO, and 8–12 hrs after starting INO. Oxygenation index ([Fio2 × mean airway pressure × 100]/Pao2) and Pao2/Fio2 ratios were calculated at the same time intervals. At 30 mins after INO initiation, 83% of patients had a significant increase in blood oxygen tension, defined as ≥20% increase in Pao2/Fio2. The mean change in Pao2/Fio2 at 30 mins was 38%. In these 19 patients, Pao2/Fio2 was highest at 20 ppm in four patients, at 10 ppm in eight patients, and at 5 ppm in seven patients. Compared with baseline measurements, Pao2/Fio2 improved significantly at both 30 mins (112 ± 59 vs. 75 ± 32, p = .01) and 8–12 hrs after INO initiation (146 ± 52 vs. 75 ± 32, p < .0001). In addition, oxygenation index was reduced at 8–12 hrs compared with baseline measurements (26 ± 13 vs. 40 ± 17, p = .08).

Conclusions INO delivered at doses of 5 to 20 ppm during high-frequency oscillatory ventilation increases Pao2/Fio2 and may be a safe and effective rescue therapy for patients with severe oxygenation failure.

From the Department of Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Canada.

Supported, in part, by the Ontario Thoracic Society; SensorMedics Critical Care Corporation (Yorba Linda, CA) provided the 3100B ventilators and technical assistance.

Combined use of high-frequency oscillatory ventilation and inhaled nitric oxide is an effective method of improving oxygenation and reducing oxygen requirements in the majority of adult patients with severe acute respiratory distress syndrome, and it may be a valuable adjunctive therapy.

* See also p. 637.

© 2003 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins