The influence of severe obesity on non-invasive ventilation (NIV) strategies and responses in patients with acute hypercapnic respiratory failure attacks in the ICU

Abstract

Background. Obesity rates are increasing in the general population and are also prevalent in intensive care units (ICUs). Patients are sometimes admitted to ICUs for hypercapnic respiratory failure or cor pulmonale, but more often, they are admitted for pneumonia, excessive daytime sleepiness, heart failure, chronic obstructive pulmonary disease (COPD), asthma attacks or pulmonary embolism, and hypercapnic respiratory failure is coincidentally noticed during this period. The optimal noninvasive mechanical ventilation strategy is often not used during ICU treatment. The aim of this study was to assess the differences between non-invasive ventilation (NIV) strategies and the outcomes of obese and non-obese patients with acute hypercapnic respiratory failure. Methods. In this retrospective cohort study, 73 patients who were ventilated with a face mask were studied. Patients were divided into two groups: obese (BMI>35 kg/m2) and non-obese (BMI<35 kg/m2), and the differences between these two groups in necessary pressure, volume, mode, ventilator and time to reduce PaCO2 <50 mmHg were investigated. Results. The mean age of the patients was 66±14 years, and the mean admission APACHE II score was 18±4. Forty-one (56%) of the patients were female. For the obese patients, the reason for ICU admission was more frequently pulmonary edema and less frequently pulmonary infections, which was significantly different (P=0.003 and 0.043, respectively) than the rates for the non-obese patients. While there was no significant difference across the groups between the ventilators, modes and inspiratory pressure levels, obese patients required higher end-expiratory pressure levels and more time to reduce their PaCO2 levels below 50 mmHg than non-obese patients. The lengths of NIV and ICU stay and intubation and the mortality rates were similar in both groups. Conclusion. These results suggest that improvement in hypercapnia in obese patients may require higher PEEP levels and longer times than that of non-obese patients during acute hypercapnic respiratory failure attack. (Minerva Anestesiol 2011;77:17-25).