Because nearly one out of three adults in the United States are classified as obese (body mass index, ≥30 kg/m2) (1), the need for allied health professionals to work with the morbidly obese population has increased dramatically. However, with the conservative estimate that 280,000 deaths annually are attributed to obesity (2,3), more drastic interventions, aside from diet and exercise, are often needed. Bariatric surgery has become an increasingly used therapeutic treatment option to reduce obesity (4), with nearly an 800% increase in bariatric surgical procedures occurring between 1998 and 2004 (5). This has created an unprecedented opportunity for allied health professionals to become involved clinically in the evaluation and treatment of morbidly obese individuals.
BENEFITS ASSOCIATED WITH BARIATRIC SURGERY
Although diet and exercise have been the traditional focus for weight reduction programs, the efficacy of bariatric surgery as a treatment modality is well established (6,7). On average, patients can expect weight loss ranging between 50% and 75% of excess body weight in the first year, and weight loss is maintained much longer than that observed after conventional weight reduction programs (6,8). In addition, significant metabolic and cardiovascular benefits can be obtained from this surgical intervention, which further improves the quality of life beyond weight loss (see Table). These benefits significantly outweigh those obtained from conventional weight loss programs in this patient population (9), and are generally more sustainable.
ROLE OF CARDIOPULMONARY EXERCISE TESTING IN PRESURGICAL SCREENING
Currently, no uniform standards exist for medical preoperative evaluations in patients undergoing bariatric surgery. The American Heart Association/American College of Cardiology guidelines state that an assessment of functional capacity should be completed as part of an evaluation before noncardiac surgery (10,11); however, these guidelines do not specifically address bariatric surgery.
Functional status is widely expressed as the aerobic capacity or maximal oxygen consumption (V˙O2max), and largely reflects the heart's ability to pump blood (i.e., cardiac output). The V˙O2max is the highest rate of oxygen transport and utilization that can be achieved at peak effort and is considered the single best indicator of physical work capacity or cardiorespiratory fitness (12). The V˙O2max is typically estimated or measured directly via cardiopulmonary exercise testing on a treadmill or cycle ergometer. Because health status may correlate more closely with the V˙O2max than any resting parameter (10), exercise testing may provide significant information regarding a patient's suitability for surgery.
Because major surgery requires increased tissue oxygenation because of the generation of a strong inflammatory response (13), the use of presurgical cardiopulmonary exercise testing may help to determine a patient's ability to withstand the added stress placed on the body during the procedure. During surgery, increased oxygen demands are generally met through enhanced cardiac output and tissue oxygen extraction. In those patients with a reduced functional capacity and limited physiological reserve, the inability to increase cardiac output may make them more likely to experience complications (14). Thus, cardiopulmonary exercise testing allows for the evaluation of integrated cardiovascular and skeletal muscle function in response to these oxygen demands (15), potentially identifying those at increased risk for surgical complications.
IMPACT OF REDUCED AEROBIC FITNESS ON SURGICAL OUTCOMES
As an allied health professional, it is important to recognize the potential impact of low functional capacity on surgical outcomes. In the nonobese population, functional capacity has been found to be a reliable indicator of perioperative and long-term cardiovascular events (16-18). Patients with a significantly reduced functional capacity during exercise testing before surgery often demonstrate an increased surgical risk (19,20). In addition, morbidly obese individuals have been found to have aerobic capacities that are comparable to patients with congestive heart failure (21). Although the use of V˙O2max as a predictor of cardiovascular and all-cause mortality in patients with chronic heart failure is well established (22,23), similar data are not yet available for the morbidly obese patient population. Preliminary studies, however, suggest that V˙O2max also may provide important prognostic information in this population to risk stratify individuals before bariatric surgery and reduce the need for extensive preliminary cardiac testing (24). In fact, the composite of death, unstable angina, myocardial infarction, deep venous thrombosis, pulmonary embolism, renal failure, or stroke was found to be more frequent in morbidly obese patients demonstrating the lowest fitness during presurgical exercise testing (24). In addition, the most common surgical complications were associated with an increased hospital stay and 30-day readmission rates (24). Such information would be especially helpful during presurgical evaluations or before initiating exercise as part of a weight reduction program.
It seems that bariatric surgery will continue to serve as a viable treatment option for weight reduction in the morbidly obese population. Technological advances continue to make the procedure safer and more effective, whereas third-party (insurance) payors have now made it more accessible. Although additional research to predict surgical outcomes is needed, it has become increasingly apparent that a multidisciplinary team of allied health professionals can perform a comprehensive prescreening and identify obese patients who would benefit from additional services before or after bariatric surgery (25). In particular, the role of the allied health professional in presurgical testing, exercise training, and rehabilitation of the morbidly obese patient may contribute significantly to the eventual outcomes achieved. Given the potential benefits of bariatric surgery (e.g., cardiovascular risk reduction, improved functional capacity) (26), priority should be given to identify best practices for evaluating presurgical risk and enhancing postsurgical recovery in this escalating patient population.
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