Conference Coverage
SAN DIEGO – Obstructive sleep apnea mechanisms may be quantified by polysomnography to select patients who are likely to respond to supplemental oxygen therapy if they can’t tolerate continuous positive airway pressure therapy, a study of 19 patients suggested.
"When [continuous positive airway pressure] isn’t enough, we’ve turned to supplemental oxygen," which can greatly reduce the severity of obstructive sleep apnea [OSA] in some patients but is ineffective in others, Scott A. Sands, Ph.D., said at an international conference of the American Thoracic Society.
Dr. Scott Sands
He and his associates applied their recently validated technique to quantify "loop gain" or breathing control from routine polysomnography in an attempt to identify patients with increased peripheral chemosensitivity, thinking they might be more responsive to oxygen therapy. An elevated loop gain represents an exaggerated ventilatory effort – a sensitive and fast ventilatory drive – in response to apnea or hypopnea, he explained.
The investigators randomized patients with OSA and an apnea-hypopnea index of at least 20 events per hour in a single-blind, sham-controlled crossover study. Patients underwent full polysomnography with either supplemental oxygen or air (the sham treatment), which was repeated with the other treatment 1 week later.
The results showed that OSA improved substantially in patients with high loop gain but not in those with low loop gain, reported Dr. Sands of Brigham and Women’s Hospital, Boston.
The apnea-hypopnea index improved significantly in patients with high loop gain when they got oxygen but not in patients with low loop gain. Apnea-hypopnea events ranged from approximately 20 to 90 per hour in patients with high loop gain while on air and from approximately 0 to 45 per hour on oxygen. In patients with low loop gain, apnea-hypopnea events ranged from approximately 25 to 110 per hour while on air and from 10 to 80 per hour on oxygen.
The percentage of sleep with stable breathing improved significantly from less than 20% while on air to approximately 35% on oxygen in patients with high loop gain but hovered just under 15% with either treatment in patients with low loop gain.
The arousal index improved significantly from nearly 50 events per hour while on air to 20 events per hour on oxygen in patients with high loop gain but hovered around 50 events per hour on either treatment in patients with low loop gain. The percentage of sleep spent in stage 1 sleep improved significantly from approximately 16% while on air to approximately 6% on oxygen in patients with high loop gain and increased in patients with low loop gain from approximately 15% on air to nearly 20% on oxygen, an increase that was not statistically significant, he said.
"These are promising findings so far," Dr. Sands said. He and his associates are working to fully automate the method of assessing loop gain and to measure additional traits from polysomnography.
Dr. Sands reported having no financial disclosures.
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