ATS 2014, SAN DIEGO ─ Clinically important sleep apnea is common among survivors of acute respiratory failure, according to a new study presented at the 2014 American Thoracic Society International Conference.
"Insomnia is a frequent complaint among survivors of critical illness," said Dr. Elizabeth Parsons, MD, MSc, of the Division of Pulmonary & Critical Care Medicine at the University of Washington in Seattle. "We examined a small cohort of survivors of acute respiratory failure to understand modifiable contributors to insomnia, including sleep apnea."
The study involved 21 patients with acute respiratory failure, defined as an acute need for at least 48 hours of mechanical ventilation. Assessment included the Insomnia Severity Index and in-home level II overnight polysomnography three months after hospital discharge. Sleep-disordered breathing was assessed with the Apnea Hypopnea Index (AHI) and the Respiratory Distress Index (RDI). The AHI measures the average number of apneas (breathing cessations) and hypopneas (partial obstructions) per hour. The Respiratory Distress Index (RDI) measures the average number of respiratory disturbances per hour (apneas, hypopneas, and milder events called respiratory effort-related arousals). An RDI of 15 or greater was considered clinically relevant to sleep quality and daytime function. An AHI of 15 or greater may be a risk factor for cardiovascular morbidity.
Among the 14 patients who underwent polysomnography, the majority met criteria for clinically-relevant sleep apnea, with 13 having an RDI of 15 or greater and 10 having an AHI of 15 or greater. Mean RDI was 38 and mean AHI was 29. Oxygen desaturations were generally mild, with an average 3% oxygen desaturation index of 8 (number of times per hour that oxygen level drops by 3 percent or more). Insomnia severity did not significantly correlate with the presence of sleep-disordered breathing.
"The incidence and severity of sleep apnea we observed among survivors of acute respiratory failure, if replicated in larger studies, are cause for concern," said Dr. Parsons. "Some patients had clinically significant sleep apnea despite lack of sleep complaints. Evaluating and treating sleep apnea may significantly impact the health and well-being of these patients."
"It is important to note that trauma was the inciting event for acute respiratory failure in 57% of our tested subjects. By subject report, 29% were actively taking an opiate pain medication at the time of testing. Opiates can worsen sleep apnea by reducing upper airway tone and central respiratory drive. Our results suggest that sleep apnea is common after acute respiratory failure, with central-acting medications serving as one potential contributor."
* Please note that numbers in this release may differ slightly from those in the abstract. Many of these investigations are ongoing; the release represents the most up-to-date data available at press time.
Sleep Disordered Breathing In Survivors Of Acute Respiratory Failure
Type: Scientific Abstract
Category: 04.07 - ICU Management/Outcome (CC)
Authors: E.C. Parsons1, V.K. Kapur1, E. Caldwell1, C. Johnston1, K. Bell2, M.V. Vitiello1, C.L. Hough1; 1University of Washington - Seattle, WA/US, 2UW Medicine Sleep Center, Harborview Medical Center - Seattle, WA/US
RATIONALEInsomnia is a common complaint after critical illness. Sleep disordered breathing (SDB) may be an important contributor to post-ICU insomnia, related to sequelae of airway trauma or central-acting medications. Data is lacking to establish the prevalence of SDB in this population and its relationship to insomnia symptoms.
METHODSWe studied a prospective cohort of 21 patients with acute respiratory failure (defined by ≥ 48 hours of mechanical ventilation) admitted to intensive care at Harborview Medical Center between October 2012 and February 2013. Subjects completed in-hospital surveys evaluating pre-hospital sleep disorders and insomnia symptoms (Insomnia Severity Index, ISI). At 3 months post-discharge, subjects repeated symptom surveys and completed a level II in-home overnight polysomnography. We created 2x2 tables and used Fisher's exact test to examine the unadjusted association between 3-month insomnia symptom severity (ISI) and SDB by the Respiratory Distress Index, RDI ≥ 15, or Apnea Hypopnea Index, AHI ≥ 15.
RESULTSOf 21 subjects enrolled in the hospital, 18 subjects (86% enrolled) completed surveys and 14 subjects (67%) completed a level II home polysomnography at 3-month follow-up. Two of the tested subjects (14%) had a pre-existing diagnosis of sleep disordered breathing. One subject had discontinued CPAP and was tested without it; the other was tested using pre-hospital CPAP settings. Nine subjects (64% tested) reported regular use of pain medications at 3-month follow-up and 4 (29% tested) took opiate medications on the evening of polysomnography. Among tested subjects, the mean RDI was 38 (IQR 25 - 50) events/hr. Most patients met criteria for SDB: 13 subjects (93%) had an RDI>=15 and 10 subjects (71%) had an AHI>=15. The average 3% oxygen desaturation index was 8 (IQR 4-7) events/hr with a mean 8% (IQR 0.1%-10%) total sleep time spent at a saturation below 90%. As shown in Table 1, there was not a significant association between insomnia symptom severity and the presence of SDB, by either RDI (P=0.57) or AHI (P=0.71).
Table 1. Insomnia symptoms versus sleep disordered breathing among 14 survivors of acute respiratory failure undergoing in-home overnight polysomnography
RDI ≥ 15
N (%) AHI ≥ 15
ISI 0-7 (not important) 3 (23%) 2 (20%)
ISI 8-14 (subthreshold) 6 (46%) 4 (40%)
ISI 15-21 (moderate) 3 (23%) 3 (30%)
ISI 22-28 (severe) 1 (8%) 1 (10%)
Total subjects 13 10
CONCLUSIONSClinically important SDB was present in most 3-month survivors of acute respiratory failure in this small cohort study. SDB of this severity may impact health risk and quality of life. Future studies are needed to identify ways to evaluate and treat SDB in this high-risk population.