Relationship between body mass index, age and hypoxemia in patients with extremely severe obesity undergoing...

Morbid obesity is frequently accompanied by serious co-morbidity, enclosed obstructive sleep apnea and hypoventilation syndrome, and thus many morbidly obese patients require surgical interventions. The aim of this study was to evaluate the relationship between arterial oxygen (pO₂) and carbon dioxide (pCO₂) partial pressure, age, loss of excess weight, and body mass index (BMI) in obese patients scheduled to undergo bariatric surgery.

A group of 11 patients (4 men, 7 women, median age 38 years, range 23-58 years) with extremely severe obesity (BMI>50 kg/m²) underwent laparoscopic Roux-en-Y gastric bypass. Preoperatively, BMI, pO₂, and pCO₂ were 52.7±2.4 kg/m², and 70.9±5.3 and 43.1±6.5 mmHg, respectively. Hypoxemia (pO₂<75 mmHg) was present in all patients, but no relationship between BMI and age (R=-0.24, p=0.44) or between BMI and pO₂ (R=0.09, p=0.77) was found.

As expected, there was a significant correlation between age and both pO₂ (R=-0.58, p=0.04) and pCO₂ (R=0.85, p=0.0004), while no relationship between BMI and age (R=-0.24, p=0.44), nor between BMI and pO₂ (R=0.09, p=0.77) was found. Finally, there was a significant correlation between pO₂ and loss of excess weight (R=-0.69, p=0.02). No intra- or postoperative complications were observed, and 12 months after surgery BMI decreased to 32.5±2.7 kg/m² (p<0.001) and pCO₂ to 37.9±5.3 mmHg (p=0.05), while pO₂ reached 85.8±6.8 (p<0.001) mmHg.

In obese patients, the severity of hypoxemia is mainly related to age. The amount of weight reduction, rather than lower baseline BMI values, may justify the significant postoperative pO₂ improvement.