By Betty Tran, MD, MSc
Associate Professor of Medicine, Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago
SYNOPSIS: In this post hoc analysis, the use of noninvasive ventilation alternating with high-flow nasal cannula post-extubation decreased the risk of reintubation and death in obese and overweight patients at high risk for reintubation.
SOURCE: Thille AW, Coudroy R, Nay MA, et al. Beneficial effects of noninvasive ventilation after extubation in obese or overweight patients: A post hoc analysis of a randomized clinical trial. Am J Respir Crit Care Med 2022;205:440-449.
Thille and colleagues performed a post hoc analysis of a multicenter randomized controlled trial conducted in 30 intensive care units (ICUs) in France that aimed to evaluate the effects of post-extubation noninvasive ventilation (NIV) on patients grouped according to body mass index (BMI).1 The original trial that formed the basis for the current analysis compared the use of high-flow nasal oxygen (HFNO) with NIV vs. HFNO alone immediately post-extubation in patients at high risk for extubation failure.1 It enrolled adult patients intubated more than 24 hours who were ready for extubation after completing a successful spontaneous breathing trial and who were at high risk for extubation failure, as defined by age > 65 years, chronic cardiac disease, or chronic lung disease.
The HFNO group was treated with continuous high-flow oxygen at 50 L/min, with fractional inspired oxygen (FiO2) adjusted to keep pulse oximetry (SpO2) ≥ 92%. The NIV group was immediately started on pressure support (PS) mode after extubation with a minimum pressure support of 5 cm H2O adjusted to target a tidal volume (Vt) of 6 mL/kg to 8 mL/kg of predicted body weight, a positive end-expiratory pressure (PEEP) of 5 cm H2O to 10 cm H2O, and enough FiO2 to maintain SpO2 > 92%. NIV was kept on for at least four hours initially, with a goal of 12 hours per day for the first 48 hours, including continuously at night, with HFNO delivered in between NIV sessions.
For statistical analyses, BMI was expressed as a continuous variable and classified into three subgroups: normal or underweight (BMI < 25 kg/m2), overweight (BMI 25 kg/m2 to 29.9 kg/m2), and obese (BMI ≥ 30 kg/m2). The primary outcome was the proportion of patients requiring reintubation within seven days of extubation according to BMI. Secondary outcomes included: reintubation rates at 48 hours, 72 hours, and up until ICU discharge; postextubation respiratory failure defined by set criteria within seven days of extubation; ICU and hospital length of stay (LOS); and ICU, hospital, and 90-day mortality, all according to BMI.
Overall, 623 patients were included in the analysis; 206 (33%) were obese, 204 (33%) were overweight, 189 (30%) had normal BMI, and 24 (4%) were underweight. Obese patients were more likely to be female, have chronic lung disease (16% had obesity hypoventilation syndrome), have a longer duration of mechanical ventilation, have more difficulty weaning, and exhibit more hypoxia and hypercapnia at the time of extubation.
A significant interaction between prophylactic NIV and risk of reintubation at day 7 by patient BMI as a continuous variable was noted (P interaction = 0.0015). Among obese or overweight patients, the seven-day rate of reintubation was 7% in the NIV group vs. 20% in the HFNO alone group (difference -13%; 95% confidence interval [CI], -19 to -6; P < 0.001). In terms of secondary outcomes, overweight and obese patients in the NIV group had a significantly lower rate of postextubation respiratory failure at seven days and reintubation rate at 48 hours, 72 hours, and until ICU discharge. Furthermore, in the overweight/obese subgroup, ICU mortality in the NIV group was 2% vs. 9% with HFNO alone (difference -6%; 95% CI, -11 to -2; P = 0.006). Mortality remained significantly lower in the NIV group up to 90 days after extubation. These findings remained significant after adjustment for unbalance variables (e.g., age, chronic lung disease, BMI) between groups.
Commentary
Obesity is associated with a reduction in lung volume, atelectasis (which can result in hypoxemia and a decrease in respiratory compliance, the latter of which is associated with increased work of breathing to generate adequate tidal volumes), and obstructive sleep apnea.2-4 Positive pressure ventilation may reduce the work of breathing by preventing airway closure, preventing atelectasis, and reducing the muscle workload needed to generate inspiratory flow, all of which could lead to a reduction in muscle fatigue and thereby decrease weaning failure.5
Although the physiologic rationale for the benefits of NIV in this patient population is sound, the systematic application of NIV “prophylactically” to all obese patients ready for extubation is not supported by sufficient data at this time. This was a post hoc analysis; results should be considered hypothesis-generating rather than conclusive. In addition, only select obese patients were included, namely, those considered at high risk for extubation failure, defined by age or chronic cardiac or lung conditions.
A randomized clinical trial of unselected obese and overweight patients is needed to confirm these results and evaluate for risks, if any, of NIV in this patient population during the postextubation period. However, results from this post hoc analysis are promising and may represent initial steps toward broadening the application of NIV to even more scenarios.
REFERENCES
- Thille AW, Muller G, Gacouin A, et al. Effect of postextubation high-flow nasal oxygen with noninvasive ventilation vs high-flow nasal oxygen alone on reintubation among patients at high risk of extubation failure. A randomized clinical trial. JAMA 2019;322:1465-1475.
- De Jong A, Wrigge H, Hedenstierna G, et al. How to ventilate obese patients in the ICU. Intensive Care Med 2020;46:2423-2435.
- Droghi MT, De Santis Santiago RR, Pinciroli R, et al. High positive end-expiratory pressure allows extubation of an obese patient. Am J Respir Crit Care Med 2018;198:524-525.
- Pépin JL, Timsit JF, Tamisier R, et al. Prevention and care of respiratory failure in obese patients. Lancet Respir Med 2016;4:407-418.
- Grieco DL, Jaber S. Preemptive noninvasive ventilation to facilitate weaning from mechanical ventilation in obese patients at high risk of reintubation. Am J Respir Crit Care Med 2022;205:382-383.
In this post hoc analysis, the use of noninvasive ventilation alternating with high-flow nasal cannula post-extubation decreased the risk of reintubation and death in obese and overweight patients at high risk for reintubation.
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