SAN ANTONIO – Opioids do not mix well with sleep, interfering with breathing and increasing the risk of central sleep apnea, explained Anita Rajagopal, MD, a pulmonologist in private practice in Indianapolis.
“The chronic respiratory suppressant effects of opioids are well described,” Dr. Rajagopal told attendees at the annual meeting of the American College of Chest Physicians. “The most characteristic signs of chronic opioid effects are irregular central apneas, ataxic breathing, Biot’s respiration and hypoxemia, mainly during NREM sleep.”
Dr. Rajagopal reviewed the research on the effects of opioid use, primarily for therapeutic use, during sleep, especially highlighting the adverse respiratory effects.
In one small study of 24 patients, ages 18-75, who were taking long-term opioids for chronic pain, 46% had severe sleep-disordered breathing, defined as an apnea-hypopnea index greater than 30/hour ().
When compared to sleep clinic patients referred for sleep disordered breathing, the participants taking opioids had a higher frequency of central apneas and a lower arousal index. Further, the researchers found that “morphine equivalent doses correlated with the severity of sleep-disordered breathing.”
In another study, a systematic review from 2015, researchers sought to characterize the clinical features of sleep-disordered breathing associated with chronic opioid therapy (). They identified eight studies with 560 patients, about a quarter of whom (24%) had central sleep apnea.
Once again, “The morphine equivalent daily dose was strongly associated with the severity of the sleep disordered breathing, predominantly central sleep apnea, with a morphine equivalent daily dose of more than 200 mg being a threshold of particular concern,” the researchers reported.
Patients receiving methadone therapy for heroin addiction are not spared the respiratory risks of opioids during sleep. Dr. Rajagopal shared research revealing that patients receiving methadone treatment for at least two months had a blunted hypercapnic respiratory response and increased hypoxemic ventilatory response, changes related to respiratory rate but not tidal volume.
“All mu-opioid receptor agonists can cause complex and potentially lethal effects on respiration during sleep,” Dr. Rajagopal said as she shared evidence from a 2007 study that compared breathing patterns during sleep between 60 patients taking chronic opioids and 60 matched patients not taking opioids ().
That study found chronic opioid use to be associated with increased central apneas and reduced arterial oxygen saturation during wakefulness and NREM sleep. Again, a dose-response relationship emerged between morphine dose equivalent and the apnea-hypopnea, obstructive apnea, hypopnea and central apnea indices (P less than .001).
Patients who took opioids long-term were also more likely to have ataxic or irregular breathing during NREM sleep, compared with patients not taking opioids.
In yet another meta-analysis and systematic review she related, researchers found across 803 patients in seven studies that long-term opioids users had a modestly increased risk for central sleep apnea but no similar increased risk for obstructive sleep apnea ().
“REM and slow-wave sleep are decreased across all categories of opioid use — intravenous morphine, oral morphine, or methadone and heroin,” she said.
Since some patients are still going to need opioids, such as methadone therapy for those recovering from opioid use disorder, it’s important to understand appropriate effective treatments for central sleep apnea.
“CPAP [continuous positive airway pressure] is generally ineffective for opioid-induced sleep apnea and may augment central events,” Dr. Rajagopal explained, but adaptive servo ventilation (ASV) is effective for opioid-induced central apneas.
In one study of 20 patients receiving opioid therapy and referred for obstructive apnea, for example, the participants were diagnosed instead with central sleep apnea (). The 16 patients who received CPAP continued to show central sleep apnea, with an AHI of 34 events/hour and central-apnea index (CAI) of 20 events/hour. Even after a four-week break before restarting CPAP, patients’ apnea did not resolve.
After receiving ASV, however, the average AHI dropped to 11 events/hour and CAI dropped to 0 events/hour. Those changes were accompanied by improvements in oxygen saturation, with the oxyhemoglobin saturation nadir increasing from 83% to 90%.
Similarly, a prospective multi-center observational trial assessed 27 patients with central apnea after they used ASV at home for three months (). The participants began with an average AHI of 55 and CAI of 23 at baseline. CPAP dropped these values only to an AHI of 33 and CAI of 10, but treatment with ASV dropped them to an AHI of 4 and CAI of 0 (P less than .001).