Does long-term home non-invasive ventilation, initiated as an outpatient, provide equivalent outcomes compared to non-invasive ventilation initiated as an in-patient in terms of physiological parameters and Health Related Quality of Life in a mixed cohort of patients over a 12-month period?

Cooper, Julie Karen (2022) Does long-term home non-invasive ventilation, initiated as an outpatient, provide equivalent outcomes compared to non-invasive ventilation initiated as an in-patient in terms of physiological parameters and Health Related Quality of Life in a mixed cohort of patients over a 12-month period? Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Introduction: Long-term nocturnal home non-invasive ventilation (NIV) has been demonstrated to improve survival, decrease admissions and reduce utilisation of healthcare resources in patients with chronic hypercapnic respiratory failure. Improvements in the management of patients with chronic respiratory disease has increased the number of patients requiring home NIV. In the UK, as in other health systems, initiation of home NIV has historically been via in-patient admission, including an overnight titration study in a specialist centre. However, if it could be demonstrated that initiation of long-term home NIV could be performed safely and effectively in an outpatient setting with outcomes that were not inferior to in-patient initiation, there is potential to reduce the burden on healthcare systems. This hypothesis formed the basis for this study. Methods: 113 patients (in-patient NIV initiation n=92) with a mix of conditions leading to chronic hypercapnic respiratory failure (predominantly COPD and OHVS), commenced on long-term home NIV as either an in-patient or an outpatient, were identified via an NIV database used as part of on-going NIV patient review. Retrospective data for demography, baseline spirometry, initial and subsequent blood gases, ventilator settings exacerbations, hospitalisations, and health-related quality of life (HRQoL) using the Serious Respiratory Insufficiency (SRI) questionnaire was reviewed. Primary outcomes compared were daytime arterial carbon dioxide pressure (PaCO2) reduction after 12 months of NIV, and change in HRQoL measured by the SRI. Secondary outcomes were the impact of home NIV on in-patient admissions, length of stay and mortality. An investigation of the potential cost savings of outpatient initiation of NIV was also undertaken. Results: The baseline arterial PaCO2 in the in-patient initiation group was higher (median 9.4kPa, IQR 8.6-11.3) than the outpatient initiation group (median 7.1kPa, IQR 6.8-8.3). Following 12-months of home NIV, there was neither a statistical (p=0.164) nor clinical difference in PaCO2 between the in-patient group (median 5.9kPa, IQR 5.3-6.4) and the outpatient group (median 6.2kPa, IQR 5.7-6.4). The pressure support required by the in-patient group (mean 13.2cmH2O, SD 3.1) at 12-months was slightly higher than the outpatient group (mean 11.7cmH2O, SD 3.6), however this difference was not statistically significant (p=0.113). Compliance, defined as total hours/total days of ‘mask on’ time measured in hours, was higher for the in-patient group (mean 7.5 hours, SD 2.4 vs. mean 6.1 hours, SD 2.5) but again, this difference was not statistically significant (p=0.059). The baseline SRI scores of the in-patient and outpatient initiation groups were not statistically different (p=0.502) and the difference between the groups (3.4 points) was less than the minimal clinically important difference (MCID), defined as 5 points. The absolute change in the mean SRI score at 12 months was greater than the MCID for both groups (in-patient mean 5.8 points, SD 24.6; outpatient mean 5.7 points, SD 14.1) but below the level of statistical significance (in-patient p=0.345; outpatient p=0.450). Compared to the outpatient initiation group, the in-patient initiation group had more admissions in the 12 months prior to NIV (p=0.016) as well as more bed days (p=<0.001). Following initiation of NIV, admissions (p=<0.001) and bed days (p=<0.001) were significantly reduced for the in-patient group; this improvement was observed for the outpatient group. Combined all-cause mortality at 1-year was 15% and there was no statistical difference in mortality between the in-patient and outpatient initiation groups (p=0.523). Based on standard NHS Tariff costs, outpatient initiation of NIV produces a potential cost saving of at least £476 per patient, but this could be as much as £1,018 per patient depending on how costs are calculated. Conclusions: Based on this single centre observational study, outpatient initiation of long-term home NIV in a mixed patient cohort produces outcomes in PaCO2 and HRQoL that are not inferior to in-patient initiation at 12-months; there appears to be no difference in mortality between the two groups. There is evidence to suggest that single centre studies may provide larger treatment effect estimates than multi-centre trials (Unverzagt, S., et al., 2013) and conclusions drawn from this data must be considered in this context. However, despite the relatively small number of outpatients included in the study, it is reassuring that comparable studies that have drawn similar conclusions do not have significantly larger numbers of patients in their study cohort. This study supports previous work that demonstrates that, in appropriately selected patients, outpatient initiation appears safe, effective and has the potential to deliver substantial cost benefits without significant reductions in HRQoL. This study provides important information about the “real world” initiation of outpatient NIV in a non-specialist centre. However, these findings can only be applied after careful consideration of the context of this study with an individual’s own situation.