Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Continuous positive airway pressure reduced the need for mechanical ventilation for cardiogenic pulmonary edema

ACP J Club. 1992 May-June;116:66. doi:10.7326/ACPJC-1992-116-3-066


Source Citation

Bersten AD, Holt AW, Vedig AE, Skowronski GA, Baggoley CJ. Treatment of severe cardiogenic pulmonary edema with continuous positive airway pressure delivered by face mask. N Engl J Med. 1991 Dec 26;325:1825-30.


Abstract

Objective

To determine whether continuous positive airway pressure (CPAP) reduces the need for mechanical ventilation in patients with respiratory failure caused by severe cardiogenic pulmonary edema.

Design

Randomized controlled trial.

Setting

A hospital in Australia.

Patients

Inclusion criteria were cardiogenic pulmonary edema with respiratory distress and either arterial oxygen tension (PaO2) < 70 mm Hg or carbon dioxide tension (PaO2) > 45 mm Hg while receiving oxygen, 8 L/min, by face mask. Exclusion criteria were a diagnosis of myocardial infarction with shock, systolic blood pressure < 90 mm Hg, severe stenotic valvular disease, and previous chronic airflow obstruction with known CO2 retention. Patients in the 2 groups were similar for demographic characteristics, blood gases, vital signs, and APACHE II scores.

Intervention

Patients received O2 either alone(n = 20) or with CPAP (n = 19). The minimal inspired O2 concentration was 60% and was increased to maintain O2 saturation above 95%. Before study entry, patients were managed using pre-established guidelines; after entry, supplemental therapy was unrestricted.

Main outcome measures

Intubation and mechanical ventilation were done either at the discretion of the attending physician or for clinical or gas exchange deterioration (either a decrease in PaO2 to < 70 mm Hg with 100% PaO2 provided by mask or an increase in PaO2 to > 55 mm Hg). Blood gases, vital signs, and arterial lactate level were measured at study entry and 0.5, 1, 3, and 24 hours after.

Main results

No patients receiving O2 with CPAP and 7 patients (35%) receiving O2 alone were intubated and ventilated (P < 0.005). {This absolute risk reduction of 35% means that 3 patients would need to receive CPAP (rather than O2) to prevent 1 additional patient from being ventilated; the relative risk reduction was 100%.}* Mean duration of CPAP was 9.3 (SD 4.9) hours. The length of stay in the intensive care unit was shorter for patients receiving O2 with CPAP (1.2 [SD 0.4] d vs 2.7 [SD 2.0] d; P = 0.006). After 30 minutes patients receiving O2 with CPAP had greater decreases in respiratory rate and PaO2, and greater increases in arterial pH and in the ratio of PaO2 to the fraction of inspired O2 (FIO2) (all P ≤ 0.01).

Conclusion

Continuous positive airway pressure with O2 in patients with respiratory failure caused by severe cardiogenic pulmonary edema reduced the need for mechanical ventilation compared with O2 alone.

Source of funding: Not stated.

Address for article reprint: Dr. A.D. Bersten, Intensive Care Unit, Flinders Medical Centre, Bedford Park, South Australia 5042, Australia.

*Numbers calculated from data in article.


Commentary

CPAP has become a widely accepted treatment in respiratory medicine for obstructive sleep apnea (OSA). With this study, Bersten and colleagues add evidence for the emerging role of CPAP in the treatment of acute pulmonary edema. Earlier work by Vaisanen and Rasanen showed a reduction of respiratory rate with CPAP, but no effect on PaO2 or PaCO2 (1). In the current study, however, significant improvement was seen in the respiratory rate as well as PaCO2, pH, and the PaO2 to FIO2 ratio within the critical first hour of treatment.

This study shows that early implementation of CPAP can decrease both the need for intubation as well as length of stay in the intensive care unit (ICU) for a patient who develops acute pulmonary edema. Future studies should examine whether nasal CPAP affords the same benefit as mask CPAP in the treatment of acute pulmonary edema. The benefits of long-term nasal CPAP on left ventricular function in patients with OSA and congestive heart failure have been shown (2). Nasal CPAP reduces the risk of aspiration, is usually more acceptable to patients than mask CPAP (less claustrophobia, greater comfort), and allows immediate access to the airway should emergent intubation be necessary.

I hope that CPAP will prove to be useful in managing patients with other mechanisms of acute respiratory failure. Perhaps immunocompromised patients, who represent a growing segment of ICU admissions, could then avoid the excess morbidity and mortality (largely from nosocomial infections) associated with intubation and ventilation.

David Daniel, MD
Stanford University Medical CenterStanford, California, USA

David Daniel, MD
Stanford University Medical Center
Stanford, California, USA


References

1. Vaisanen IT, Rasanen J. Continuous positive airway pressure and supplemental oxygen in the treatment of cardiogenic pulmonary edema. Chest. 1987;92:481-5.

2. Bradley TD, Takasaki Y, Orr D, et al. Sleep apnea in patients with left ventricular dysfunction: beneficial effects of nasal CPAP. Prog Clin Biol Res. 1990;345:363-8.