Pulmonary Considerations in Obesity and the Bariatric Surgical Patient

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Severe obesity can be associated with significant alterations in normal cardiopulmonary physiology. The pathophysiologic effects of obesity on a patient's pulmonary function are multiple and complex. The impact of obesity on morbidity and mortality are often underestimated. Bariatric surgery has been shown to be the most effective modality of reliable and durable treatment for severe obesity. Surgical weight loss improves and, in most cases, completely resolves the pulmonary health problems associated with obesity.

Section snippets

Pathophysiology of pulmonary dysfunction due to obesity

Obese patients sustain a combination of mechanical and inflammatory mediated insults that result in pulmonary disability. The excess fat externally and internally compresses the thoracic cavity. Evidence suggests that fatty infiltration of the accessory muscles of breathing can decrease compliance of the chest wall. Central adiposity can increase intra-abdominal pressure causing cephalad displacement of the diaphragm. This displacement results in a chronic abdominal compartment syndrome

Asthma

Asthma currently affects 5% of the population, and the percentage is increasing yearly [13]. Likewise, we are seeing a worldwide epidemic of obesity with numbers that are increasing at a notable rate. This increase has led some people to postulate that the rise in asthma is secondary to the rise in obesity. An increasing body of literature demonstrates a relationship between obesity and asthma, and these two entities may be causally related [14], [15], [16], [17], [18]. In a multivariate

Obstructive sleep apnea

OSA is the intermittent cessation of breathing during sleep due to the collapse of the pharyngeal airway, resulting in multiple apneic or hypopneic events. During the apneic events, the arterial oxygen pressure (PaO2) decreases and the partial pressure of carbon dioxide (PaCO2) increases, which causes an increase in ventilatory effort and subsequently triggers arousal. This effect is often accompanied by dysrhythmias, bradycardia, and heart block. Sympathetic tone is likewise increased and

The obesity hypoventilation syndrome

OHS, also known as pickwickian syndrome, is defined as having a BMI greater than 30 kg/m2 and an awake PaCO2 greater than 45 mm Hg in the absence of a known cause for hypoventilation. It is frequently accompanied by OSA. Like OSA, OHS is underdiagnosed. Studies have shown that as many as 30% of hospitalized obese patients have OHS [31].

OHS shares much of its pathogenesis with OSA; however, there appears to be an element of decreased ventilatory drive in the presence of an elevated PCO2 in

Perioperative considerations

Candidates for bariatric surgery should be evaluated for pulmonary health problems related to their obesity. Screening studies such as sleep studies and pulmonary function tests are an important part of the preoperative work-up to avoid perioperative complications. OSA is undiagnosed, and unrecognized OSA may greatly influence perioperative morbidity and mortality. There should be a low threshold for OSA screening with PSG in the obese population before weight-loss surgery [29], [30]. Once OSA

Venous thromboembolism and bariatric surgery

The risk for venous thromboembolism is increased in patients undergoing laparoscopic bariatric procedures, in part, due to increased femoral and iliac vein stasis caused by pneumoperitoneum and the reverse Trendelenburg position. The incidence of postoperative deep vein thrombosis detected by duplex ultrasound in select recent reports is 0% to 2.65% [43], [44], [45], [46], [47]. Nguyen and colleagues [48] quantified the hemodynamic effect on femoral vein flow during laparoscopic gastric bypass

Outcome on pulmonary function following bariatric surgery

Weight loss has been shown to greatly improve or, in some instances, eradicate obesity-related pulmonary dysfunction. These improvements have also been shown following weight-loss surgery [2], [34], [54], [55], [56], [57], [58], [59], [60], [61], [62], [63], [64], [65], [66], [67], [68], [69], [70], [71], [72], [73]. According to the National Institutes Consensus Development Conference Statement on the surgical treatment of obesity, patients with a BMI of 40 kg/m2 or greater are candidates for

Summary

Evaluation of the bariatric surgery patient should include a thorough history and physical examination to detect previously undiagnosed obesity-related comorbidities. Pulmonary comorbidities are often underdiagnosed, and there is strong evidence for the screening of patients with PSG. Knowledge of these preoperative conditions can allow the practitioner to safeguard against the common pitfalls that can occur in the perioperative setting. A multidisciplinary approach is optimal in these patients

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