LONDON- Oxygen should be the initial therapy for acute severe asthma in all health care settings, British researchers suggest.[1] Their rationale: Giving oxygen first may stave off profound hypoxemia, which is often an important factor in many asthma-related deaths. Their recommendation contrasts with current British and American guidelines. “The guidelines advise oxygen initially for patients with acute severe asthma who are in the hospital, but not for those in primary care or other settings,” lead author David Inwald, MB, MRCP, told RESPIRATORY REVIEWS.

A CHILD’S DEATH PROMPTED REVIEW

Dr. Inwald and his colleagues began to investigate this issue after they looked after a child who eventually died following treatment for acute severe asthma in a primary care setting. The child had received albuterol nebulized with compressed air, which made the authors question whether oxygen should have been used instead. They were unable to perform a systemic review because—perhaps surprisingly—there are no randomized controlled trials of oxygen for acute severe asthma. Thus, they substituted a traditional literature review, which included 24 papers.

According to the authors, the primary argument supporting the use of oxygen is that B2-agonists can cause or worsen hypoxemia in patients with acute severe asthma when nebulized with compressed air. B2-Agonists can cause pulmonary vasodilation, increased perfusion to poorly ventilated lung units, and ventilation–perfusion mismatch. This effect was first seen more than 30 years ago with isoprenaline.[2] Similar problems have been observed with albuterol.

ACUTE SEVERE ASTHMA ONLY

The authors do not suggest that oxygen be used in the management of mild or moderate asthma; in these settings, a B2-agonist can be administered through an air-driven nebulizer or metered-dose inhaler with a spacer, said Dr. Inwald, who is a clinical research fellow at the Institute of Child Health in London. “However, the best treatment for patients with severe or life-threatening asthma is oxygen, followed by a B2-agonist through an oxygen-driven nebulizer and then more oxygen,” he added.

He and his colleagues urge national pulmonary societies to review this issue when updating asthma guidelines. Moreover, they suggest that primary care providers have oxygen available in the office; it may also be appropriate to consider home oxygen tanks for patients with difficult-to-control asthma.

--Timothy Begany