Some Patients With Severe COPD Will Improve on Ventilation

Ingrid Hein

October 24, 2019

Noninvasive ventilation is a well-known life-sparing option during acute exacerbations of chronic obstructive pulmonary disease (COPD), but its effectiveness for severe, but stable disease has been difficult to establish.

"European data are showing that we need to do things differently," said Lisa Wolfe, MD, from Northwestern University in Chicago.

"The new thrust is to do two things," she told Medscape Medical News.

The first is to "use higher amounts of pressure support; add backup rates to it," and the second is to "do it specifically in patients with hypercapnia and high hospital admissions," she explained at CHEST 2019 in New Orleans.

Recent European studies have shown that in the right patients, a reduction in chronically elevated carbon dioxide and the delivery of high-pressure support that allows the diaphragm to rest contribute to the effectiveness of ventilation.

In a recent review published in Annals of the American Thoracic Society, Wolfe and her colleagues looked at studies of noninvasive ventilation in COPD to better understand why some showed benefit and others did not.

In part, the research did not evaluate the right treatment in the right patients, Wolfe reported. "They were looking at relatively low-level pressure support; we see that levels between 8 mL/kg and 12 mL/kg did not really show a benefit."

Ridding Carbon Dioxide

We now understand that low inspiratory pressure support does not "get rid of carbon dioxide," she explained. "And without successfully doing this, we can't get these people better."

In European studies, increased pressure and wider support significantly increased tidal volume; improved alveolar ventilation, gas exchange, and carbon dioxide levels; and ultimately rested the diaphragm.

"This is important," Wolfe emphasized. "Increased carbon dioxide allows for the diaphragm to rest. This is where we see a significant improvement."

"Effective ventilation appears to improve survival and quality of life only when the chronically elevated carbon dioxide is effectively reduced, not in the setting of acute COPD exacerbation," the researchers write in their review.

The European studies also show the benefit of ventilation at home for patients with COPD.

Home Care

In new guidelines on the long-term use of noninvasive ventilation for COPD, the European Respiratory Society Task Force recommends treatment for patients with stable hypercapnic COPD and patients who require acute ventilation after a COPD exacerbation.

The guidelines state that ventilation settings should target a reduction in carbon dioxide and fixed-pressure support should be the first ventilator mode used.

A Dutch study published last month in Thorax showed that ventilation at home is as safe as that administered in the hospital.

But to bring ventilation to severe COPD patients at home, an overhaul of the system is needed, Wolfe pointed out.

These are "European trials," she explained. "It's not just a machine patients take home; they get wraparound care." A respiratory therapist follows patients in their homes to ensure that they use the equipment correctly and that it is working.

If we want good outcomes, we can't just hand out the machine and hope.

There is no current mechanism to write a "prescription" for a respiratory therapist, although there is for occupational therapists and physiotherapists. "We need to give patients the same wraparound care we see in Europe for this to work," Wolfe said.

"All the studies showing benefit and cost-effectiveness have been done outside the United States," said Gerard Criner, MD, from the Lewis Katz School of Medicine at Temple University in Philadelphia.

He is frustrated, he told Medscape Medical News, because he has been trying to get funding for a trial looking at the benefits of ventilation at home in the United States for years.

Noninvasive ventilation for COPD is mired in contradictory outcomes because studies are not comparable, he explained during his presentation at the meeting.

"Few studies have looked at how to acclimate patients to therapy," Criner said, and none used the same method.

For example, in one study of noninvasive positive-pressure ventilation published in Lancet Respiratory Medicine, patients were hospitalized for 5 days so they could acclimate to the treatment, in a study published in JAMA, patients were hospitalized for 1 or 2 days, and in a study published in Thorax, they were hospitalized for 1 day.

In the JAMA study, only 5% of screened patients were enrolled, only 5% completed the trial, and 30% switched from another treatment to positive-pressure ventilation. And patients in the Thorax study had transient hypercapnia, whereas in the other two studies, patients had chronic hypercapnia.

"We need to understand what we are studying and choose the right patients," Criner said. "These studies have looked at small numbers and there has been significant dropout," he pointed out. "With restricted numbers, it's hard to see how broad this therapy can be."

Lack of Information

Criner was involved in a 2014 retrospective study that looked at 166 patients with acute exacerbations of COPD and hypercapnia who were treated with positive-pressure ventilation during hospitalization.

Event-free survival was significantly better in the half of that cohort discharged with home ventilation than in the half discharged with no positive-pressure ventilation (P < .0001). In addition, the rate of hospital readmission in the 180 days after first admission was lower with home care (40% vs 75%; P < .0001).

In a small pilot study Criner was involved in, when patients with severe COPD and hypercapnia used high-intensity positive-pressure ventilation at home for 3 months, partial pressure of carbon dioxide (P = .01)  and dyspnea (P = .03)  increased. In addition, 6-minute walk distance improved, as did scores on the Epworth Sleepiness Scale, Chronic Respiratory Disease Questionnaire (P = .054), the daily functioning domain of the Calgary Sleep Apnea Quality of Life Index (P = .007), and the Severe Respiratory Insufficiency Questionnaire (P = .05).

"Outcomes are being limited because of a lack of information," Criner told Medscape Medical News.

A subgroup of patients — those who are obese, have limited gas exchange, have acute on chronic severe respiratory failure — could benefit from at-home ventilation, but current restrictions on positive-pressure ventilation limit availability. "Doctors are prescribing a workaround," he explained.

We still need to know the optimal subject characteristics and outpatient noninvasive ventilation treatment technique to maximize benefits, he added. But for that, we need funding.

CHEST 2019: American College of Chest Physicians Annual Meeting. Presented October 21, 2019.

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