Sleep-disordered breathing is common in patients with neuromuscular disease and is increasingly addressed with noninvasive ventilation, but its patterns go beyond obstructive sleep apnea (OSA) and include hypoventilation, hypoxemia, central sleep apnea, pseudocentrals, periodic breathing, and Cheyne-Stokes respiration, Gaurav Singh, MD, MPH said at the virtual annual meeting of the Associated Professional Sleep Societies.
The prevalence of sleep-related disordered breathing surpasses 40% in patients diagnosed with neuromuscular disease, but “sleep disordered breathing [in these patients] does not equal obstructive sleep apnea,” said Dr. Singh, staff physician at the Veteran Affairs Palo Alto (Calif.) Health Care System in the section of pulmonary, critical care and sleep medicine, and an affiliated clinical assistant professor at Stanford (Calif.) University.
“The most common sleep-related breathing disorder in neuromuscular disease is probably hypopnea and hypoventilation with the sawtooth pattern of dips in oxygen saturation that occur during REM sleep,” he said. As neuromuscular diseases progress, hypoventilation may occur during non-REM sleep as well.
Evaluation is usually performed with polysomnography and pulmonary function testing, he said, but supplementary testing including serum bicarbonate levels, arterial blood gases, and echocardiography to assess for left ventricular ejection fraction and cardiomyopathy may be useful as well.
While a sleep study is not required per Centers for Medicare & Medicaid coverage criteria for the use of respiratory assist devices in patients with neuromuscular disease, polysomnography is valuable for identifying early nocturnal respiratory impairment before the appearance of symptoms and daytime abnormalities in gas exchange, and is better than home testing for distinguishing different types of events (including pseudocentrals). It also is helpful for determining the appropriate pressures needed for ventilatory support and for assessing the need for a backup rate, Dr. Singh said.
Commonly used types of noninvasive ventilation include bilevel positive airway pressure on the spontaneous/timed or pressure control modes, with or without volume-assured pressure support, he said.
Expiratory positive airway pressure (EPAP) is usually set low initially to help decrease the work of breathing and improve triggering, then titrated up to ensure that upper airway obstructive events are treated. Pressure support (the difference between the inspiratory positive airway pressure and EPAP) is set to achieve target tidal volume and to rest the respiratory muscles. And inspiratory time is set “on the longer end” to achieve maximal target volume and ensure appropriate gas exchange, Dr. Singh said.
Data from randomized controlled trials evaluating the effectiveness of NIV are limited, he said. A study published 15 years ago showed a survival benefit and improvement in quality of life measures in patients with amyotrophic lateral sclerosis (ALS) with normal or moderately impaired bulbar function but not in those with severe bulbar weakness.
Regarding the timing of initiating NIV, a retrospective study published several years ago looked at almost 200 ALS patients and evaluated differences in survival amongst those started earlier with NIV (forced vital capacity ≥80%) and those started later (FVC <80%). At 36 months from diagnosis, mortality was 35% for the early group and 53% for the later group. “Improved survival was driven by benefit in patients with non–bulbar-onset ALS, compared with bulbar-onset disease,” Dr. Singh said.
“This study and several other similar studies seem to indicate that the earlier NIV [noninvasive ventilation] is started in patients with neuromuscular disease, the better in terms of improving survival and other relevant measures such as quality of life,” he said.
Asked about Dr. Singh’s presentation, Michelle Cao, DO, clinical associate professor at Stanford University, said that NIV is an “invaluable tool in the treatment of conditions leading to chronic respiratory failure,” such as neuromuscular disease, and that it’s important to incorporate NIV training for future pulmonary, critical care and sleep physicians. Dr. Cao directs the adult NIV program for the neuromuscular medical program at Stanford Health Care.
Saiprakash B. Venkateshiah, MD, of Emory University, Atlanta, also said in introducing Dr. Singh at the meeting that earlier diagnosis and appropriate NIV therapy “may improve quality of life and possibly even lower survival in certain disorders.”
In addition, he noted that sleep disturbances “may be the earliest sign of muscle weakness in [patients with neuromuscular disease], sometimes being detected before their underlying neuromuscular disease is diagnosed.”
Dr. Singh, Dr. Cao, and Dr. Venkateshiah each reported that they had no potential conflicts of interest.