Postoperative respiratory failure is associated with increased in-hospital mortality and ICU length of stay (1). Poor outcome has been linked to complications during the reintubation period and healthcare-associated infections (2). Measures to reduce reintubation rates in this cohort of patients may lead to improved outcome.
Respiratory modifications can be induced due to the effect of surgery, postoperative pain and anaesthesia, namely: hypoxemia, decreased lung volume, atelectasis and diaphragmatic dysfunction (3). These changes are more often transient, but can lead to respiratory failure.
In multiple randomised controlled trials, non-invasive ventilation (NIV) has shown benefits in chronic obstructive pulmonary disease and other disease processes causing respiratory failure in non-surgical patients (4). However, no randomised clinical trials have evaluated whether NIV could reduce the need for invasive mechanical ventilation and its effect on the incidence of healthcare-associated infections in patients who develop hypoxemic acute respiratory failure after abdominal surgery.
The NIV in Abdominal Postoperative Period (NIVAS) study group examined the hypothesis that early application of NIV may prevent reintubation and invasive mechanical ventilation and may decrease the rate of healthcare-associated infections (2). The investigators conducted a multicentre randomised clinical trial of NIV in surgical patients who developed hypoxemic acute respiratory failure after abdominal surgery, comparing NIV (inspiratory pressure support level, 5-15 cm H2O; positive end-expiratory pressure, 5-10 cm H2O; fraction of inspired oxygen titrated to maintain SpO2≥94%) against standard oxygen therapy (up to 15 L/min to maintain SpO2 of 94% or higher).
In this trial, NIV via face mask reduced the need for reintubation and for invasive mechanical ventilation and was associated with fewer episodes of healthcare-associated infections compared to standard oxygen therapy. The investigators could show that NIV significantly reduced overall health care associated infections and halved the rate of pneumonia. These findings could be explained by NIV's effect on reducing atelectasis which in turn could decrease bacterial growth and mitigate bacterial translocation from the lung into the bloodstream. Furthermore, avoidance of endotracheal intubation is probably the major reason for the pneumonia reduction observed in the NIV group.
"…NIV via face mask reduced the need for reintubation and for invasive mechanical ventilation and was associated with fewer episodes of healthcare-associated infections…. and halved the rate of pneumonia."
Previous studies have reported complications with NIV use, including gastric distention and pulmonary aspiration. In this study, no adverse events were reported in either group and the NIV group did not show higher morbidity. In fact, there was a trend toward lower mortality in the NIV group.
Strengths and limitations
The main the strengths of this study are: a) the large sample size, b) the selected population base, c) multicentre design, d) the explicit criteria for reintubation, and e) a complete postoperative follow-up. In addition, the baseline characteristics in the 2 groups were well matched, and the criteria for healthcare-associated infection diagnosis are both validated and robust.
This study, however, does have limitations. Firstly, the observed rate of reintubation in this study was lower than predicted in the standard oxygen therapy group. Secondly, the study design was not powered to show decrease in mortality in the NIV group. Thirdly, although predefined criteria for reintubation was applied, bias cannot be completely ruled out due to unfeasibility of blinding NIV.
The findings of this study support the use of NIV in treating patients with hypoxemic respiratory failure following abdominal surgery. The use of NIV compared with standard oxygen therapy reduced the risk of tracheal reintubation within 7 days. Future studies comparing use of high-flow oxygen cannula vs standard oxygen therapy and NIV for patients after abdominal surgery as preventive or curative application are needed.
Article review was submitted by ESICM Journal Review Club member Omar Bani-Saad.
1. Serpa Neto, A., et al., Incidence of mortality and morbidity related to postoperative lung injury in patients who have undergone abdominal or thoracic surgery: a systematic review and meta-analysis. Lancet Respir Med, 2014. 2(12): p. 1007-15.
2. Jaber, S., et al., Effect of Noninvasive Ventilation on Tracheal Reintubation Among Patients With Hypoxemic Respiratory Failure Following Abdominal Surgery: A Randomised Clinical Trial. JAMA, 2016. 315(13): p. 1345-53.
3. Jaber, S., G. Chanques, and B. Jung, Postoperative noninvasive ventilation. Anesthesiology, 2010. 112(2): p. 453-61.
4. Kelly, C.R., A.R. Higgins, and S. Chandra, Noninvasive Positive-Pressure Ventilation. New England Journal of Medicine, 2015. 372(23): p. e30.