Non-invasive mechanical ventilation (NIV) at home not only keeps people out of hospital, it also extends life and reduces COPD exacerbations.
Re-analysis of results from a trial adding home NIV to oxygen therapy for patients with persistent hypercapnia after a COPD exacerbation confirmed that it improved admission-free survival, increasing median time to readmission or death from 1.1 months to 3.7 months
Mechanical ventilation is used to stabilise patients with hypercapnia. Results published in JAMA earlier this year showed home NIV reduced the chances of readmission or death by 50 percent.
But the researchers, from the Guys and St Thomas’ NHS Trust’s Lane Fox Respiratory Service, were concerned that their intention-to-treat analysis masked some of the physiological effects of the treatment.
This was partly because the protocol allowed crossover to NIV for patients randomised to oxygen therapy alone if they developed acidosis.
“If you treat someone for respiratory failure, do you improve their respiratory failure?” asked Dr Patrick Murphy, consultant physician.
He said the team wanted to know whether those who actually used NIV had better physiological outcomes than those who never used it.
The researchers reanalysed on a per-protocol basis, comparing outcomes for patients who were compliant with NIV (an average four hours a day of use during the study period) with patients who used home oxygen therapy only.
In addition to the positive findings on admission-free survival, the researchers found some secondary outcomes gained significance. NIV improved all-cause mortality by 64% and reduced exacerbations from 5.3 to 3 per patient per year.
Importantly, 12-month PaCO2 demonstrated that the treatment had lowered arterial pressure of carbon dioxide – and kept it low.
“This confirms the biological plausibility,” said Dr Murphy, who presented the data at the session on hot topics in home-based mechanical ventilation.
“The machines are being used to change the physiology – it’s not just a placebo effect.”
He says the study will allow doctors to better target the intervention, and that the data will help inform shared decision making with patients.
His results suggested that PaCO2 six weeks after exacerbation is a good prognostic factor. “If [patients] are still hypercapnic at six weeks, we need to tell them their outcomes are much worse if we don’t use this treatment,” he told delegates.
The study did not find improved quality of life, possibly because the treatment interferes with sleep and patients don’t like using it, Dr Murphy speculated.
However, he said it could be challenging to identify significant improvements in quality of life with usual measurement tools in such a frail group of patients.