Effect of Narcotics on Respiratory Physiology
Narcotics, and in particular opioids, have several effects on respiratory physiology, which are more pronounced during sleep. They decrease central respiratory patterns, respiratory rate, and tidal volume. They also increase airway resistance and decrease the patency of the upper airways. This may lead to ineffective ventilation and upper airway obstruction in susceptible individuals.
These agents can produce irregularities in normal breathing patterns. Irregular respiratory pauses and gasping may lead to erratic breathing and significant variability in respiratory rate and effort. This ataxic, or Biot breathing, is observed in the majority of patient with long-term opiate use.
Narcotic Use and Sleep-Disordered Breathing
The incidence of sleep-disordered breathing after both short- and long-term opioid use is well established, but also somewhat controversial. Several studies have shown a marked increase in sleep-disordered breathing with both acute and chronic use of narcotics, regardless of the agent used, dose, duration of therapy, or individual risk factors for OSA. In contrast, other reports have failed to observe increased rates of sleep-disordered breathing in patients using opioids.
For example, whereas no significant increase in OSA was seen in a study of 50 consecutive patients receiving long-term methadone therapy compared with controls, another study of 71 patients with long-term methadone use diagnosed OSA in 35% of patients. Of note, these individuals were evaluated because of sleep complaints. Given the variability in the published literature, it is likely that the emergence of OSA does result from narcotic use, but it is significantly more probable in susceptible individuals.
The form of sleep-disordered breathing associated with chronic opioid use is equally controversial. Although central sleep apnea (CSA) is classically associated with opioid use, it appears that OSA is more commonly encountered.[10,12] Earlier reports found a predominance of CSA, whereas more recent studies have shown OSA is significantly more common among patients receiving long-term opioid therapy.
This transition is not due to any identifiable changes in the demographic characteristics of the included participants. It may reflect an evolution in the practice of pain management, with newer agents, different delivery systems, and higher doses being used. Or, it may be that obstruction has always been the predominant respiratory event and this transition merely reflects the advancement of the field of sleep medicine and sophistication of polysomnographic equipment, which allow a more accurate assessment of sleep and sleep disorders. Regardless, both breathing patterns are commonly observed, and it is important to differentiate the 2 because this may alter treatment and treatment strategies.
Among patients receiving acute oral narcotics, OSA is observed in 35.2% and CSA in only 14.1%. In a study assessing methadone maintenance patients with subjective sleep complaints, OSA was significantly more common than CSA. Similarly, OSA was diagnosed in 35%-57% of patients managed in long-term pain clinics. In an observational controlled trial of nonobese long-term opioid users, the majority of patients were found to have sleep-disordered breathing, with a mean apnea/hypopnea index of 43.9 ± 1.2. Most apneas were obstructive and not central events.
Farney and colleagues explored the occurrence of sleep disordered breathing in a population of young, non-obese, long-term opioid users. The demographic characteristics of this cohort were not typical for a high prevalence of OSA. The mean age was 31.8 ± 12.3 years, the mean body mass index was 24.9 ± 5.9 kg/m2, and 60% were women. Nonetheless, at least mild OSA was present in 63%. Furthermore, moderate OSA was observed in 16%, and 17% had severe sleep apnea. Nocturnal hypoxia was also common was more significant than would be expected for the degree of sleep apnea noted. An oxygen saturation below 90% for 10% or more of the total sleep time was noted in 38.6% of the cohort.
Medscape Pulmonary Medicine © 2013 WebMD, LLC
Cite this: The Association of Obstructive Sleep Apnea and Chronic Pain - Medscape - May 24, 2013.