Therapy Continuous Positive Airway Pressure for Treatment of Postoperative Hypoxemia: A Randomized Controlled Trial
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Summary
Posted By:	Stuart Green
E-Mail:	Stuart_green@health.qld.gov.au
Posted Date:	18 feb 2005
Title:	Continuous Positive Airway Pressure for Treatment of Postoperative Hypoxemia: A Randomized Controlled Trial
Authors:	Vincenzo Squadrone; Massimiliano Coha; Elisabetta Cerutti; Maria Maddalena Schellino; Piera Biolino; Paolo Occella; Giuseppe Belloni; Giuseppe Vilianis; Gilberto Fiore; Franco Cavallo; V. Marco Ranieri; for the Piedmont Intensive Care Units Network
Reference:	JAMA. 2005;293:581-588.
Link:	Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract:	Context: Hypoxemia complicates the recovery of 30% to 50% of patients after abdominal surgery; endotracheal intubation and mechanical ventilation may be required in 8% to 10% of cases, increasing morbidity and mortality and prolonging intensive care unit and hospital stay. Objective To determine the effectiveness of continuous positive airway pressure compared with standard treatment in preventing the need for intubation and mechanical ventilation in patients who develop acute hypoxemia after elective major abdominal surgery. Design and Setting Randomized, controlled, unblinded study with concealed allocation conducted between June 2002 and November 2003 at 15 intensive care units of the Piedmont Intensive Care Units Network in Italy. Patients Consecutive patients who developed severe hypoxemia after major elective abdominal surgery. The trial was stopped for efficacy after 209 patients had been enrolled. Interventions Patients were randomly assigned to receive oxygen (n = 104) or oxygen plus continuous positive airway pressure (n = 105). Main Outcome Measures The primary end point was incidence of endotracheal intubation; secondary end points were intensive care unit and hospital lengths of stay, incidence of pneumonia, infection and sepsis, and hospital mortality. Results Patients who received oxygen plus continuous positive airway pressure had a lower intubation rate (1% vs 10%; P = .005; relative risk [RR], 0.099; 95% confidence interval [CI], 0.01-0.76) and had a lower occurrence rate of pneumonia (2% vs 10%, RR, 0.19; 95% CI, 0.04-0.88; P = .02), infection (3% vs 10%, RR, 0.27; 95% CI, 0.07-0.94; P = .03), and sepsis (2% vs 9%; RR, 0.22; 95% CI, 0.04-0.99; P = .03) than did patients treated with oxygen alone. Patients who received oxygen plus continuous positive airway pressure also spent fewer mean (SD) days in the intensive care unit (1.4 [1.6] vs 2.6 [4.2], P = .09) than patients treated with oxygen alone. The treatments did not affect the mean (SD) days that patients spent in the hospital (15 [13] vs 17 [15], respectively; P = .10). None of those treated with oxygen plus continuous positive airway pressure died in the hospital while 3 deaths occurred among those treated with oxygen alone (P = .12). Conclusion Continuous positive airway pressure may decrease the incidence of endotracheal intubation and other severe complications in patients who develop hypoxemia after elective major abdominal surgery.
Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
	Yes. "Concealed randomisation was conducted centrally through a dedicated web site using a computer generated block randomisation schedule." Unfortunately it was not stated whether a uniform block size was employed (Ex. blocks of 4) or if blocks of different sizes were used. If a uniform block size was employed, recent research suggests it may have been possible to predict the upcoming allocation group for every fourth patient. To address this issue, variable block sizes are strongly recommended.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
	Yes. 1,322 patients were screened with 1,080 not meeting eligibility criteria and 11 patients refusing consent. 209 truly eligible patients were randomised and analysed.
2b. Were patients analyzed in the groups to which they were randomized?
	Yes. 6 patients did not tolerate treatment but were analysed in the group they were rendomised in.
3. Were patients, health workers, and study personnel blind to treatment?
	No, this trial was not blinded.
4. Were the groups similar at the start of the trial?
	Yes. Table 1 demonstrates that groups were similar at baseline.
5. Aside from the experimental intervention, were the groups treated equally?
	Where possible treatment was standardised but actual treatment rates were not explicitly reported. There was an attempt to objectively define end points.
What are the Results?
1. How large was the treatment effect?
	Primary outcome: Intubation rate 1 patient out of 105 in CPAP group required intubation vs 10 of 104 in control group (p=0.005 from Fisher's Exact test). Secondary outcomes: Improvements in favour of CPAP: pneumonia reduction(2% vs 10%, RR, 0.19; 95% CI, 0.04-0.88; P = .02), infection reduction (3% vs 10%, RR, 0.27; 95% CI, 0.07-0.94; P = .03) sepsis reduction(2% vs 9%; RR, 0.22; 95% CI, 0.04-0.99; P = .03)
2. How precise was the estimate of the treatment effect?
	95% CI for the relative risk [RR] reduction for need of intubation: 0.099; 95% confidence interval [CI], 0.01-0.76)
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
	Considering the extensive exclusion these results are difficult to directly apply to allpatients commonly see in my ICU. However this article does lend support to the care of patients who would have qualified for entry into the trial.
2. Were all clinically important outcomes considered?
	Intubation as a primary outcome could be considered a poor choice, however the improvement in clinically relevant secondary outcomes such as icu length of stay, pneumonia, sepsis were significent statistically.
3. Are the likely treatment benefits worth the potential harms and costs?
	Low cost, low risk treatment for potential benefit.
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