Influence of severe obesity on non-invasive ventilation strategies and responses in patients with acute hypercapnic respiratory failure in ICU

Introduction

Obesity rates are increasing in the general population and it is also prevalent in ICUs. Patients are sometimes admitted to ICUs for hypercapnic respiratory failure or cor pulmonale but in general they are admitted for pneumonia, excessive daytime sleepiness, heart failure, COPD or asthma attacks or pulmonary embolism; and hypercapnic respiratory failure is noticed during this period. On the other hand, optimal non-invasive mechanical ventilation strategy is not known during their ICU treatment. The aim of this study is to assess the differences between NIV strategies and outcomes between obese and nonobese patients with acute hypercapnic respiratory failure.

Methods

In this retrospective cohort study, 73 patients were studied and all of them were ventilated with a face mask. Patients divided into two groups as obese (BMI >35 kg/m²) and nonobese (BMI <35 kg/m²), and whether necessary pressure, volume, mode, ventilator and time to reduce PaCO₂ below 50 mmHg were significantly different in obese and nonobese patients was investigated.

Results

Mean age of the patients was 66 ± 14 years and mean admission APACHE II score was 18 ± 4; 41 (56%) of them were female. ICU admission reasons for the obese patients were significantly more frequently pulmonary edema and less frequently pulmonary infections (P = 0.003 and 0.043, respectively) than the nonobese patients. While there were no significant differences across the groups between the ventilators, modes, and inspiratory pressure levels, obese patients required higher end-expiratory pressure levels and more time to reduce the PaCO₂ level below 50 mmHg than the nonobese group. Length of NIV and ICU stay, intubation and the mortality rate were similar across the groups.

Conclusions

These results suggest that improvement of hypercapnia in obese patients may require higher PEEP levels and longer times than the non-obese ones during acute hypercapnic respiratory failure attack.