AUSTIN, TEX. – Obstructive sleep apnea appeared to provide protection against in-hospital mortality and nonroutine discharge among mechanically ventilated patients with pneumonia who were included in the National Inpatient Sample from 2009 to 2011.
Patients included in the analysis were 20,652 adults with a mean age of 65 years who were hospitalized with a primary diagnosis of pneumonia requiring invasive mechanical ventilation, representing nearly 107,000 such discharges nationally. About 8% of the patients had obstructive sleep apnea (OSA), and 11% were obese. Overall mortality was 31%, and the overall rate of nonroutine discharge, defined as discharge to a skilled nursing facility or to home with home health care, was 84%, Dr. Charlisa Gibson reported at the annual meeting of the American College of Chest Physicians.
Though limited by its retrospective nature and possible underreporting of OSA, this study demonstrates that OSA in patients with pneumonia requiring invasive mechanical ventilation confers a survival benefit, she said.
Those with OSA had a significantly higher rate of tracheostomy (9.2% vs. 8.3%), a lower rate of in-hospital mortality (19% vs. 31%), and a lower rate of nonroutine discharge (77% vs. 84%), compared with non-OSA patients. Length of stay was about 14 days in both groups, said Dr. Gibson, of Mount Sinai St. Luke’s-Roosevelt Hospital, New York.
Those in the non-OSA group had higher rates of shock and septicemia.
After adjustment for age, sex, obesity, comorbidities, and disease severity, OSA was a significant predictor of decreased in-hospital mortality (odds ratio, 0.74) and nonroutine discharge (odds ratio, 0.73), Dr. Gibson said.
“In pretty much all of the conditions of interest we looked at, we consistently saw that mortality was lower in the OSA group, whether they were obese or not … and whether or not they were deemed to have a low, moderate, or severe [Charlson Comorbidity Index],” she said.
OSA is an important and likely underdiagnosed comorbidity in hospitalized patients, and pneumonia remains a significant infectious cause of morbidity and mortality in hospitalized patients, she said. OSA affects about 5%-24% of the general population, but the percentage of hospitalized patients with OSA is uncertain.
About 20% of hospitalized patients with pneumonia end up in the intensive care unit for supportive treatment with mechanical ventilation.
“Once they are vented, there are data to suggest that early tracheostomy may shorten time on mechanical ventilation and hospital length of stay, but whether or not there’s an actual impact on mortality is controversial,” she said.
While prospective randomized controlled studies are needed to better identify risk factors for mortality, Dr. Gibson said there are several possible explanations for the findings of a protective effect of OSA in hospitalized patients with acute respiratory failure due to pneumonia.
First, non-OSA patients had more septicemia and shock, which suggests they may have had multisystem organ failure and required treatments like renal replacement therapy that independently increased their risk of mortality.
Also, the increased incidence of tracheostomy in the OSA patients may indicate that clinicians were more aggressive in treating patients with OSA, and that those patients may have benefited from earlier tracheostomy, she said.
There is some evidence to suggest that OSA patients have additional coronary collateral circulation, which means that they may have less severe cardiac injury because of this adaptation, and thus may have a lower risk of experiencing a fatal heart attack, compared with non-OSA patients, she explained.
The “obesity paradox” might also work in OSA patients’ favor, she said. There is some evidence that obese patients have increased metabolic reserve that results in lower complication rates, compared with normal weight patients.
“However, we do recommend that regardless of what the reason is, when these patients do come to the unit we should be aggressive and treat them with invasive mechanical ventilation if needed,” she said.
Dr. Gibson reported having no disclosures.