Nevertheless, Arozullah and colleagues' study is a significant step forward in preoperative pulmonary risk assessment and helps us to establish priorities for future research. One of the most important contributions of the study is its size; a major limitation of previous studies is small samples that limited our ability to examine a broad spectrum of plausible risk factors. Arozullah and colleagues' findings add to a recent thorough review of previous studies (8). The following are consistent sentinel risk factors across different definitions of complications in different surgical populations: smoking status, chronic obstructive lung disease (defined by history or clinical examination; preoperative spirometry has not proven prognostically useful), measures of general health status (such as comorbid condition measures, functional status, and recent weight loss), cognitive impairment, previous stroke, and type of surgery. Age was also found to be a risk factor in this and previous studies, depending on how well the researchers controlled for comorbid conditions. Additional risks identified with this large study include long-term steroid use, recent moderate to heavy alcohol intake, impaired renal function, and large transfusions, all suggestive of depressed immune competence as a risk factor for pneumonia. Lack of data precluded analysis of several other potentially important variables, such as albumin level, spirometry, use of prophylactic antibiotics, and body mass index or obesity. However, previous studies have consistently suggested that spirometry, although diagnostically accurate, does not provide useful prognostic information and that obesity is not a significant risk factor for postoperative pulmonary complications (8).