Invasive mechanical ventilation may be complicated by ventilator-associated lung injury, ventilator-associated pneumonia, the need for sedation and muscle paralysis, and the possibility of airway-related problems. Noninvasive ventilation (NIV) is widely used by clinicians in community-acquired pneumonia (CAP), in the hope of avoiding intubation thereby improving clinical outcomes. Although the efficacy of NIV in patients with chronic obstructive airways disease (COPD) with pneumonia is reasonably well established, the evidence for its use in non-COPD patients is less clear. We are currently faced with an epidemic of viral pneumonia in many parts of India; would it be appropriate to offer a trial of NIV to some of these patients?
In an early observational study of patients with CAP and acute respiratory failure, a high intubation rate (66%) was observed, although there was an initial improvement in the PaO2/FiO2ratios.1 A large, registry-based cohort study was carried out during the 2009 H1N1 pandemic from 35 intensive care units in Argentina. NIV use carried a survival of 43/64 patients (67%) in this study, significantly higher than those who underwent invasive ventilation.2 The authors speculated that the improved survival observed with NIV may have been due to a lower severity of illness at baseline. In our series of 31 patients during the 2009 H1N1 pandemic, noninvasive ventilation was initially carried out in eight patients; four patients failed and subsequently underwent invasive ventilation.3 Several early studies suggest worse outcomes with NIV in acute hypoxemic respiratory failure, including CAP.4 More recent studies, some using a helmet device, suggest benefit with NIV use.5,6 Elderly, immunocompromised patients with CAP were shown to have a better 90-d survival with NIV use in a retrospective cohort study.7
Against the background of this fairly dodgy evidence, where do we stand in relation to NIV use in severe CAP with acute hypoxemic respiratory failure? Unfortunately, there are no robust, controlled studies that can guide us in deciding whether to resort to NIV as an initial line of therapy. Should we give a trial of NIV or just carry on with intubation and invasive ventilation in patients who present with CAP and acute hypoxemic respiratory failure? Are there reliable predictors of NIV failure that can help decision making?
In a prospective observational study of 64 patients with CAP, NIV was successful in 28 (44%). On multivariate analysis, a decrease in the oxygenation index (mean airway pressure × FIO2 × 100/PaO2) by 1.2 or more and an increase in the PaO2/FiO2ratio by 42.2 or more predicted NIV success. Furthermore, on ROC curve analysis, a pH of more than 7.38 and a respiratory rate of less than 27/min were also predictive of successful NIV use.8 In another prospective study of 184 patients with CAP, NIV failed more often in patients without previous cardiac or respiratory disease compared to those who had comorbidities. Radiological worsening and higher SOFA scores also predicted NIV failure. After an NIV trial of 1 h, an increase in heart rate, a fall in the PaO2/FiO2ratio, and lower bicarbonate levels were independent predictors of failure.9 In another retrospective cohort study of 209 patients, NIV failure occurred in 90 of 117 patients (77%); patients who failed NIV had a significantly higher mortality compared to those who succeeded. On multivariate analysis, higher APACHE scores and the requirement for vasopressors at 2 h were associated with NIV failure.10
I am sure you would agree that the situation is far from clear-cut. We have been mortified by lack of success with NIV in a handful of patients in our unit during this flu season. With the limited observational evidence we have, I would highlight the following points to ponder on before embarking upon an NIV trial in patients with CAP and acute hypoxemic respiratory failure.
- It is crucial to identify patients who are likely to benefit from NIV.
- Patients who have no significant comorbidities are more likely to failNIV (counterintuitive as it may seem).
- The higher the baseline severity of illness, the lower the likelihood of NIV success.
- Failure to improve physiological parameters, including the respiratory rate, P/F ratio, oxygenation index, and bicarbonate levels within the first few hours is likely to result in failure.
- Radiological worsening in the first 24 hours calls for invasive ventilation.
- It is important to recognize early signs of failure and resort to invasive ventilation expeditiously.
Please feel free to offer your valuable comments and input.
- Jolliet, P., Abajo, B., Pasquina, P. & Chevrolet, J. C. Non-invasive pressure support ventilation in severe community-acquired pneumonia. Intensive Care Med.27, 812–821 (2001).
- Estenssoro, E. et al.Pandemic 2009 influenza A in Argentina: a study of 337 patients on mechanical ventilation. Am. J. Respir. Crit. Care Med.182, 41–48 (2010).
- Chacko, J., Gagan, B., Ashok, E., Radha, M. & Hemanth, H. V. Critically ill patients with 2009 H1N1 infection in an Indian ICU. Indian J. Crit. Care Med. Peer-Rev. Off. Publ. Indian Soc. Crit. Care Med.14, 77–82 (2010).
- Honrubia, T. et al.Noninvasive vs conventional mechanical ventilation in acute respiratory failure: a multicenter, randomized controlled trial. Chest128, 3916–3924 (2005).
- Cosentini, R. et al.Helmet continuous positive airway pressure vs oxygen therapy to improve oxygenation in community-acquired pneumonia: a randomized, controlled trial. Chest138, 114–120 (2010).
- Brambilla, A. M. et al.Non-invasive positive pressure ventilation in pneumonia outside Intensive Care Unit: An Italian multicenter observational study. Eur. J. Intern. Med.(2018). doi:10.1016/j.ejim.2018.09.025
- Johnson, C. S., Frei, C. R., Metersky, M. L., Anzueto, A. R. & Mortensen, E. M. Non-invasive mechanical ventilation and mortality in elderly immunocompromised patients hospitalized with pneumonia: a retrospective cohort study. BMC Pulm. Med.14, (2014).
- Carron, M., Freo, U., Zorzi, M. & Ori, C. Predictors of failure of noninvasive ventilation in patients with severe community-acquired pneumonia. J. Crit. Care25, 540.e9–14 (2010).
- Carrillo, A. et al.Non-invasive ventilation in community-acquired pneumonia and severe acute respiratory failure. Intensive Care Med.38, 458–466 (2012).
- Murad, A., Li, P. Z., Dial, S. & Shahin, J. The role of noninvasive positive pressure ventilation in community-acquired pneumonia. J. Crit. Care30, 49–54 (2015).