CPAP or BIPAP for Hypoxic CHF Exacerbation
Search Strategy: While attending the January 2007 Best Evidence in Emergency Medicine course at the Silver Star Mountain Resort in British Columbia, you’d heard about one or two meta-analyses addressing this specific question. Digging out your BEEM manual, you quickly locate both articles and find two randomized controlled trials by quickly scanning the references of the two meta-analyses.
A 70-year old female presents with 2-days of increasing dyspnea, orthopnea, and lower extremity edema. Her past medical history includes ischemic cardiomyopathy (EF 15% on her last Echo in 2006 without any significant valvular disease), hypertension, and irritable bowel syndrome. She notes no history of asthma, COPD, or tobacco abuse. In short, incomplete sentences she insists that she has been compliant with all of her medications.
On physical exam you note, hypertension (200/110), sinus rhythm with an S3 gallop, scant rales without wheezing, and symmetric pitting edema extending to the mid-thigh. The chest radiograph displays pulmonary venous congestion.
While obtaining the initial work-up over the patient’s first hour in the ED and despite the initiation of diuretics, afterload reduction, and supplemental oxygen, she develops progressively increased resting dyspnea with oxygenation deteriorating from 90% to 80%. While preparing to intubate you contemplate the use of non-invasive positive pressure ventilation (BIPAP or CPAP) and formulate the following question in your mind to answer after your clinical shift.
Population: ED patients presenting with acute decompensated congestive heart failure with hypoxia
Intervention: Non-invasive positive pressure ventilation
Comparison: Supplemental oxygen and routine medical care alone
Outcome: CHF-related morbidity and mortality, NIPPV complications and failure rates (need to intubate)
First years: Non-invasive Ventilation in Acute Cardiogenic Pulmonary Edema: Systematic Review and Meta-analysis? JAMA 2005; 294: 3124-3130.
Second years: Effect of Non-invasive Positive Pressure Ventilation (NIPPV) on Mortality in Patients with Acute Cardiogenic Pulmonary Oedema: A Meta-Analysis. Lancet 2006; 367: 1155-1163.
Third years: Noninvasive Ventilation in Cardiogenic Pulmonary Edema: A Multicenter Randomized Trial. Am J Respir Crit Care Med 2003; 168: 1432-1437.
Fourth years: Randomised Controlled Comparison of Continuous Positive Airways Pressure, Bilevel Non-invasive Ventilation, and Standard Treatment in Emergency Department Patients with Acute Cardiogenic Pulmonary Oedema. Emerg Med J 2004; 21: 155-161.
Article 1: Noninvasive Ventilation in Acute Cardiogenic Pulmonary Edema. Systematic Review and Meta-analysis, JAMA 2005; 294; 24: 3124-3130
Article 2: Effect of non-invasive positive pressure ventilation (NIPPV) on mortality in patients with ACPE: A Meta-Analysis, Lancet 2006; 367,1155-1163
Article 3: Non-invasive Ventilation in Cardiogenic Pulmonary Edema: A Multicenter Randomized Trial, Am J Respir Crit Care Med 2003; 168:1432-1437
Article 4: Randomized controlled comparison of CPAP, BIPAP and standard treatment in ED patients with ACPE, Emerg Med J 2004; 21:155-161
CPAP and BIPAP appear to be equivalent, although CPAP has been studied more. Based upon meta-analyses of similar high quality RCT’s, the NNT to prevent one death with non-invasive ventilation is about 10 and the NNT to prevent one intubation is about 6. Most of the individual RCT’s only enrolled a fraction of the eligible subjects (11-31% range) so external validity of these findings to the general ED population presenting with hypoxic, acidotic acute cardiogenic pulmonary edema is questionable at best. BIPAP has displayed a trend towards increased MI rates, although the data is equivocal and based on a questionable pathophysiological mechanism. Unless intubation is absolutely indicated (intractable vomiting or high aspiration risk, unconscious patient), sufficient evidence exists to label non-invasive ventilation as standard of care in hypoxic, acidotic CHF patients presenting to the ED.