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Synopsis: The early use of noninvasive ventilation (NIV) for patients with mild to moderate acidosis from chronic obstructive pulmonary disease (COPD) is both feasible and effective at reducing the need for mechanical ventilation and improving mortality.
Source: Plant PK, et al. Lancet 2000;355:1931-1935.
Noninvasive ventilation (niv) in an intensive care unit (ICU) reduces rates of intubation and mortality when used in acute respiratory failure, especially for chronic obstructive pulmonary disease (COPD) exacerbations. Results in the emergency department (ED) and on general wards have been mixed. NIV improves physiologic parameters such as pH, respiratory rate, and PaCO2. NIV has been used on patients with respiratory failure of various causes. The purpose of this study was to determine whether NIV was feasible on general medicine wards and whether outcome in COPD was improved when compared to standard treatment.
Plant and colleagues conducted a prospective, multicenter, randomized, controlled trial recruiting adults who were hospitalized for COPD exacerbations from 14 hospitals in the United Kingdom. Patients were included if they were admitted as an emergency based on history, physical exam, and chest x-ray, had a respiratory rate (RR) more than 23, pH 7.25-7.35, and a PaCO2 more than 6 kPa upon arrival to the general ward after treatment in the ED and within 12 hours of admission. Exclusion criteria included pneumothorax, Glasgow coma scale less than 8, or inappropriate active treatment. Standard therapy consisted of oxygen to maintain saturation between 85-90%, nebulized salbutamol or terbutaline, nebulized ipatropium bromide, corticosteroids, and an antibiotic. The NIV group added bilevel positive airway pressure with an expiratory pressure of 4 cm H2O and an inspiratory pressure of 10 cm H2O being adjusted as needed over one hour. Aminophylline and doxapram was used as clinically indicated.
The 236 patients recruited over 22 months were equally divided (n = 118) into the two groups. In the standard group, 32 (27%) were intubated as compared to 18 (15%) in the NIV group. In-hospital mortality was 20.3% (n = 24) and 10.2% (n = 13), respectively. Those with a pH of less than 7.3 had a worse outcome. There was no difference in the time to intubation between the groups. NIV more rapidly corrected acidosis at one hour, had a greater fall in RR at four hours, and had a trend to a more rapid correction in PaCO2 at one hour. The pH, RR, and PaCO2 improved in both groups at four hours. NIV improved the sense of breathlessness (4 days compared to 7 days) though there was no difference in mobility and nutritional intake. NIV required 26 minutes of greater nursing in the first eight hours; however, workload after eight hours was no different between the two groups. Further, there was no difference in the length of stay or discharge data (pH, PaCO2, PaO2, and FEV1).
Plant et al conclude that NIV is both feasible on general respiratory wards and clinically effective. It reduces the rates of intubation and in-hospital mortality in mild- to-moderate acidosis from a COPD exacerbation provided that the nursing staff can assure compliance and invasive ventilation is accessible should the need arise. The use of NIV on the general ward will depend on the availability of ICU beds in the particular institution.
COMMENT By David Ost, MD, & Dheeraj Khanna, MD
Patients with acute respiratory failure often require mechanical ventilation for life support. The benefits of NIV are well documented but its role is still evolving. It has been used for both obstructive and restrictive disease. A meta-analysis by Keenan and associates concluded that the addition of NIV to standard therapy improves survival and decreases the rate of intubation for those in acute respiratory failure, particularly in COPD.1 A prospective case series by Hilbert and associates demonstrated that NIV decreased the need for intubation, the duration of ventilatory assistance, and duration of ICU stay.2 The present study revealed that these benefits could be realized on a general medical ward as well. With the growing support for NIV in improving morbidity and mortality in acute and chronic respiratory failure, a consensus conference report advocates the use of NIV in chronic respiratory failure due to restrictive disease, COPD, and nocturnal hypoventilation given the proper clinical setting.3 Despite the promising effects of NIV, it is often underused even when available.4
NIV has important implications in the practice recommendations of COPD with its demonstrated improvement in morbidity and mortality. It is an effective temporizing measure in acute respiratory failure. By improving physiologic parameters, NIV improves survival and decreases the intubation rates in both the ICU and general medicine wards. It is particularly useful in patients with hypercapnic respiratory failure from COPD, restrictive lung disease, and nocturnal hypoventilation.
1. Keenan SP, et al. Crit Care Med 1997;25:1685-1692.
2. Hilbert G, et al. Intensive Care Med 1997;23:955-961.
3. Chest 1999;116:521-534.
4. Doherty MJ, Greenstone MA. Thorax 1998;53:863-866.