Individual perspective
Randomized clinical trials that explore the usefulness of non-invasive ventilation for patients with COPD and chronic hypercapnic respiratory failure have been conducted and published since the early 90s. More recently, two meta-analyses,26 27 that used different methods for aggregation of data, arrived at similar conclusions regarding clinical benefits.
The first meta-analysis identified 21 randomized controlled trials and 12 observational studies that enrolled 51 085 patients with COPD and hypercapnia who used domiciliary non-invasive ventilation for more than a month.26 That study distinguished between bi-level positive airway pressure machines, with and without a backup rate, which typically deliver pressure targeted ventilation, and non-invasive home mechanical ventilators, which have pressure and volume targeting in addition to greater monitoring, alarm, and backup features. When the data for the two types of devices were aggregated and compared with no respiratory support, non-invasive ventilation was associated with lower risk of mortality (risk difference −5.53% (95% confidence interval −10.29% to −0.76%), reduced all cause hospital admissions (−35.26% (−49.39% to −21.12%) and lower need for intubation risk difference −8.02% (−14.77% to −1.28%). Of note, when the analysis was done with randomized controlled trials only, no difference was reported in clinical outcomes. This disconcordance might be caused by insufficient power or little heterogeneity of the populations studied in the individual randomized controlled trials. Only two observational studies compared non-invasive home mechanical ventilators with no device. Use of home mechanical ventilators was associated with fewer all cause hospital admissions compared with no respiratory support, but no difference in mortality. In the 19 studies that enrolled patients with stable COPD, non-invasive ventilation was associated with a lower risk of mortality regardless of the device used (odds ratio 0.62 (95% confidence interval 0.42 to 0.92); P=0.02). No significant difference was reported for all cause hospital admissions, intubations, or quality of life. By contrast, when non-invasive ventilation was initiated in patients who had experienced a recent (within one month) COPD exacerbation, no mortality benefit or improvement in quality of life was reported compared with no device use, though a lower need for intubation and fewer all cause hospital admissions were noted.
In the second meta-analysis, 21 randomised controlled trials, encompassing 1142 patients, that investigated non-invasive ventilation for at least 5 h per night for three consecutive weeks or more were included and compared with standard care.27 The investigators obtained individual patient data from most of the clinical trials and conducted linear and cox regression mixed effect modeling as well as meta-analysis on aggregated clinical trial data. Among patients with stable COPD, non-invasive ventilation reduced PaCO2 concentrations at three months and 12 months. Non-invasive ventilation was associated with low risk for all-cause mortality (adjusted hazard ratio 0.75 (95% confidence interval 0.58 to 0.97)). Among patients who received non-invasive ventilation in the setting of a recent (within 3 months) exacerbation, similar reductions in PaCO2 concentrations were noted without any improvement in all-cause mortality. However, survival without admission to the hospital seemed to improve with non-invasive ventilation (adjusted hazard ratio 0.71 (95% confidence interval 0.54 to 0.94)).
The findings of these two meta-analyses should be interpreted with some caution. Most of the studies were unblinded. Implementation of non-invasive ventilation varied from study to study by different modes and intensity of ventilation, PaCO2 thresholds for inclusion, duration of follow-up, relation to exacerbated disease state, and timing of initiation of non-invasive ventilation (in hospital v ambulatory).
From an individual patient’s perspective, non-invasive ventilation is well tolerated and adherence is high. In the three randomized controlled trials with one year follow-up, patients used the non-invasive ventilation device on the average 5.9,28 6.3,29 and 7.6 h/night.30 In a large observational cohort study of patients with chronic respiratory failure on non-invasive ventilation, researchers reported an average use of 6.5 h/night use among 334 patients with obstructive lung disease.31 Adherence >4 h/night was associated with a lower mortality. Perhaps counterintuitively, adherence might be better when higher versus lower pressure settings are used.32 This could, in part, owe to patient perception of superior clinical benefits with higher pressure settings. Severe complications from domiciliary non-invasive ventilation have not been reported in clinical trials28–30 33 or real world studies.34–36 Non-invasive ventilation side effects included aerophagia, mask related pressure ulcers, mask intolerance, dry mouth, and shortness of breath on discontinuation of non-invasive ventilation. Overall, the side effects led to discontinuation in a minority of patients (<15%) in clinical trials. Various mask interfaces have been used to facilitate non-invasive ventilation in patients with COPD chronic hypercapnic respiratory failure. Although oronasal masks are more commonly used,37 one randomized crossover trial showed successful non-invasive ventilation delivery with both oronasal and nasal masks and heterogeneity of individual responses to mask type.38
While the meta-analyses concluded no effect of non-invasive ventilation on quality of life measures in the context of chronic hypercapnic respiratory failure and COPD, this conclusion could stem from the use of tools that have not been specifically validated for use in this particular patient population.39 Using the Severe Respiratory Insufficiency questionnaire, a tool validated for this patient group receiving non-invasive ventilation, significant28 30 or a strong trend29 toward improvements in quality of life have been shown in randomized controlled trials with one year follow-up.
Economic and societal perspective
Chronic hypercapnic respiratory failure and COPD carries a poor prognosis. In a query of electronic medical records, among 491 patients with compensated hypercapnia of various causes, with 170 (35%) having COPD, each 5 mm Hg increase in PaCO2 was associated with an increased all cause mortality (hazard ratio 1.09; 95% confidence interval 1.03 to 1.16).40 Over the course of a year, these patients accounted for 1030 hospital admissions and 218 (44.4%) had ≥two hospital admissions. Therefore, implementing non-invasive ventilation in this context could reduce healthcare use and costs. In a retrospective study of the Medicare Limited Data Set (2012–18), patients with COPD and chronic hypercapnic respiratory failure who received non-invasive ventilation treatment experienced reduced risk of mortality (relative risk reduction 39%) and reduced hospital admissions (17%) compared with a matched cohort who did not have reductions.41 Furthermore, a cost effectiveness analysis, based on the results of a randomized controlled trial,30 showed a favorable incremental cost per quality adjusted life year of $50 856 (£42 406, €49 818) in the USA.42
Clearly, the burden of the evidence suggests a salutary effect for non-invasive ventilation in the setting of chronic hypercapnic respiratory failure and COPD. In the following sections, we provide the reader with general recommendations for some of the unresolved issues that surround non-invasive ventilation implementation.