From the University Sleep Disorders Center (Dr BaHammam), College of Medicine, and National Plan for Science and Technology, King Saud University; and the Intensive Care Unit (Dr Esquinas Rodriguez), Hospital Morales Meseguer.
CORRESPONDENCE TO: Ahmed S. BaHammam, MD, FCCP, University Sleep Disorders Center, College of Medicine and National Plan for Science and Technology, King Saud University, Box 225503, Riyadh 11324, Saudi Arabia; e-mail: firstname.lastname@example.org
FINANCIAL/NONFINANCIAL DISCLOSURES: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
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We read with interest the article by Lindenauer et al1 in CHEST (May 2014), who retrospectively reported the outcome of patients hospitalized with pneumonia who had coexisting OSA. The study showed higher initial rates of mechanical ventilation, with a modestly lower risk for inpatient mortality among patients with pneumonia who had OSA. However, a few points need clarification before associating OSA with increased rate of mechanical ventilation and lower risk for inpatient mortality in patients with pneumonia.
The authors reported that obesity was more prevalent among patients with OSA (37.8% vs 6.2%); however, they did not report the BMI. It is difficult to attribute the findings to OSA alone.1 We think that the higher initial rates of mechanical ventilation and the lower mortality rates could be explained by obesity. It is known that obese patients in the ICU require mechanical ventilation more often than normal-weight patients and for longer periods.2 Morbidly obese patients devote a good proportion of total body oxygen consumption to maintain the high demand of the respiratory work, even during quiet breathing, which results in a decreased ventilatory reserve and a predisposition to respiratory failure even during mild pulmonary or systemic insults.3 Moreover, studies have shown no increase in mortality of obese patients who were in the ICU and mechanically ventilated compared with normal-weight patients.4 Current evidence suggests that adipocyte-secreted hormones such as leptin and IL-10 have immunomodulatory properties that might suppress the inflammatory response and improve host survival in obese patients with severe illness.5
Therefore, it is possible that the reported differences in hospital course and outcome between patients hospitalized with pneumonia with and without OSA are due to obesity. Future studies should assess the effect of OSA on hospital course and outcome of patients with pneumonia while controlling for BMI.
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