Nasal ventilation for acute ventilatory failure
ACP J Club. 1994 Jan-Feb;120:16. doi:10.7326/ACPJC-1994-120-1-016
Bott J, Carroll MP, Conway JH, et al. Randomised controlled trial of nasal ventilation in acute ventilatory failure due to chronic obstructive airways disease. Lancet. 1993 Jun 19;341:1555-7.
To determine whether nasal intermittent positive pressure ventilation (NIPPV) decreases mortality and improves outcomes in patients with chronic obstructive airways disease (COAD) who were hospitalized for ventilatory failure.
Randomized controlled trial with a minimum follow-up of 30 days.
3 hospitals in the United Kingdom.
60 patients ≤ 80 years of age, with an arterial PaO2 < 56 mm Hg and an arterial PaCO2 > 45 mm Hg, hospitalized with an acute exacerbation of COAD. Exclusion criteria were severe disease not attributable to chronic respiratory disease, severe psychiatric disease, or NIPPV home use.
30 patients were allocated to receive conventional therapy and 30 patients to receive conventional therapy plus NIPPV (volume-cycled in assist-control mode). NIPPV was given for ≤ 16 h/d and interrupted for eating, drinking, and ambulation. Patients could receive controlled oxygen, bronchodilators, antibiotics, diuretics, respiratory stimulants, and corticosteroids.
Main Outcome Measures
Mortality; blood gas measurements; shortness of breath, well-being, and quality of sleep using visual analog scales; and need for nursing care.
4 patients allocated to NIPPV did not receive it (2 patients were too confused, 1 was unable to breathe nasally, and 1 requested withdrawal). Physicians chose to give NIPPV to 3 patients who were allocated to receive conventional therapy only, and 2 were intubated. Mean NIPPV was 7.3 h/d for 6 days. Using intention-to-treat analysis, the groups did not differ for mortality (3 of 30 in the NIPPV group vs 9 of 30 in the conventional therapy group relative risk, 0.33; 95% CI, 0.10 to 1.11). Compared with patients who received conventional therapy, patients who received NIPPV had a lower score for breathlessness during the first 3 days (P < 0.025), had increased blood pH after 1 hour of therapy (mean difference in change, 0.046; CI, 0.06 to 0.02), and decreased PaCO2 (mean difference in change, 9 mm Hg; CI, 3 to 15 mm Hg). The groups did not differ for other arterial blood gas measurements, quality of sleep, general well-being, or need for nursing care.
Patients who received nasal intermittent positive pressure ventilation for acute ventilatory failure caused by chronic obstructive airways disease had reduced breathlessness for the first 3 days and improved arterial blood gas values at 1 hour.
Source of funding: British Lung Foundation.
For article reprint: Prof. J. Moxham, Department of Thoracic Medicine, King's College School of Medicine and Dentistry, Bessemer Road, London SE5 9JP, United Kingdom. FAX 71-3246-3445.
In patients with COAD, several factors predispose to respiratory failure. Abnormal lung mechanics impose an increased load against which respiratory muscles must contract. Hyperinflation shortens inspiratory muscle length and decreases the force with which the muscles can contract. Lastly, poor nutrition, hypoxemia, and hypercarbia all adversely affect respiratory muscle function. As work requirements increase and respiratory muscle strength decreases, respiratory failure is likely. Clinicians have used noninvasive intermittent positive and negative pressure ventilation in various chronic respiratory conditions to "unload" the respiratory muscles and to avoid the need for intubation and mechanical ventilation. In stable but severe COAD, the results with negative pressure ventilation have been disappointing (1). A recent report in the setting of an acute COAD exacerbation, however, suggested that inspiratory positive pressure delivered with a face mask could reduce the need for intubation and mechanical ventilation (2). This is the first randomized trial using NIPPV for this patient population and confirms earlier uncontrolled studies that NIPPV is well tolerated by patients and can reverse dyspnea and arterial blood gas abnormalities. The trend toward improved 30-day survival in the efficacy analysis but not in the intention-to-treat analysis is intriguing; however, the mortality rate among the conventional therapy group was unusually high. Further, it is not clear that the patients died of respiratory failure. NIPPV may become an attractive alternative to intubation and mechanical ventilation in acute exacerbations of COAD, but more evidence is needed to define clearly when and how it should be used.
Randolph Lipchik, MD
Medical College of Wisconsin Milwaukee, Wisconsin