The pre-operative assessment of candidates for bariatric procedures is based on the principle of identifying modifiable health concerns and implementing risk reducing treatments to reduce peri-operative morbidity and mortality. Most bariatric patients have known conditions, which are already being treated by a primary care physician (PCP), alleviating the need to perform additional probing tests. Patients with unlimited exercise tolerance have half the risk of serious post-operative complications compared to those with a low tolerance. Excessive weight infringes on the chest wall, rib cage, and diaphragm, directly affecting pulmonary function in morbidly obese (MO) patients. Although psychiatric evaluation for patients seeking bariatric surgery is considered important, at the present time there is a lack of consensus as to how to proceed. Nutritional evaluation should also be initiated prior to surgery. Appropriate evaluation of the bariatric patient seeks to identify modifiable risk factors and can exclude poor candidates prior to surgery.

This chapter discusses respiratory system mechanics and gas exchange during anesthesia of morbidly obese (MO) patients. It describes ventilatory strategies that can improve oxygenation while protecting the lungs from ventilator-induced mechanical stress. After induction of anesthesia, deterioration of partial pressure of arterial oxygen (PaO2) occurs in MO patients. For normal weight and obese patients, prolonged mechanical ventilation with high pressure can induce mechanical stress and acute ventilator-associated lung injury (VALI). PaCO2 is correlated with effective ventilation, and an acute decrease in PaCO2 after recruitment indicates improvement (decrease) of physiologic dead space. The chapter summarizes various peri-operative strategies that provide open-lung ventilation and protect against ventilator-induced lung injury. High tidal volume (VT) without positive end-expiratory pressure (PEEP) during mechanical ventilation may cause subclinical lung injury. For MO patients, a protective ventilatory strategy incorporates prevention of atelectasis and lung overexpansion while using lower end-inspiratory pressure (PEI).