Mechanics of Sleep Apnea
Upper airway collapse is worsened during the perioperative and periprocedural care of a patient, especially if they receive premedication, general anesthesia, anxiolytics, antiemetics, and opioid analgesia.1,2,4,5 The result of decreased pharyngeal tone is reduced ventilation and oxygenation, causing hypoxia and hypercapnia, which inhibits the arousal response associated with each apnea incident of apnea. Airway obstructions also strain heart and lung function.
Premedication with drugs such as benzodiazepines has muscle relaxing effects on the upper airway musculature, causing a reduction of the posterior pharyngeal airway. The result is increased risk for hypoventilation, hypercapnia, and hypoxemia necessitating monitoring of oxygenation and ventilation.
There is considerable risk associated with premedications for procedures done outside the operating room, because we often underestimate the need for monitoring cardiovascular changes in these patients. Capnography is a non-invasive alternative to ABGs and detects real time changes in carbon dioxide. Additionally, patients receive outpatient procedures and are sent home to recover shortly after procedure.
Determining readiness for discharge requires defining risk factors for sleep apnea or sleep deprivation. Routinely assessing discharge criteria will reduce the risk for problems at home.
On an intra-operative basis, these patients frequently have more difficult intubations and extubations. They have a greater chance for adverse events due to hypoxemia, high or low blood pressure, cardiac arrythmias and aspiration pneumonias, as seen in the post anesthesia recovery unit (PACU). Discharge delays in the PACU are more likely due to an inability to maintain oxygenation at desirable levels for discharge, resulting in increased clinical care for nurses, anesthesiologists, and respiratory therapists.
Due to the risk for cardiopulmonary arrest, patients often require a discharge from PACU to a higher level of care for more exhaustive monitoring of their ventilation and increased sedation that can include telemetry, observation care for 7 hours or overnight, and even intensive care.1,2,5
Sleep patterns are changed significantly in patients recovering in a critical care unit. They have frequent interruptions that will worsen the effects of sleep deprivation, increasing the impact on sleep-disordered breathing. Treatment with positive air pressure will improve the outcome of patients with cardiac and respiratory co-morbidities, and the implications of this are significant, because sleep-disordered breathing is such a common (frequently untreated and undiagnosed) chronic disease of middle-aged adults.5
No Time to Relax
Anesthetics, analgesic, and sedative drugs produce increased muscle relaxation of the throat and tongue, and in someone at risk for sleep apnea, may create an airway blockage. When administering anesthetics, the surgeon anesthesiologist may need to alter the type and dosages of medications received to protect the breathing responses. Post surgical pain management may also require adjustment to prevent diminished breathing. As a result, narcotic pain medication or sedation will be balanced to prevent respiratory depression.
Surgery of the upper abdomen, breast, chest, or upper airway can complicate matters for patients at risk for sleep apnea by causing increased respiratory discomfort. Respiration is shallow with these surgical procedures, and increased pain adds to this discomfort when trying to breath.
When being cared for in a supine position, added risk occurs from the relaxation of the muscles in the posterior airway. Unless contraindicated, the head of the bed should be elevated 20-30 degrees to lessen some of the force placed on the posterior airway.
Positive air pressure may be required to support breathing after surgery or after a procedure requiring sedation or pain medication, especially if depressed respiration due to decreased ventilation becomes a concern.
Deep Sleep Suffers
Patients at risk for sleep apnea experience less time in the deep levels of sleep, reducing the body’s natural capacity for healing and pain control. As a consequence, these processes work less effectively.
The states of NREM (non-rapid eye movement) and REM (rapid eye movement) each perform a different function, and both are crucial to overall daytime effectiveness. Going to sleep is like descending a stairway. As brain activity slows, we transition into NREM sleep until we reach deep sleep. When in deep sleep, pulse and respiratory slows, blood pressure drops, muscles relax, and growth hormone is released to facilitate physical healing, enhanced pain control, and physical rejuvenation.
About every hour and a half we come out of deep sleep into REM sleep, an active state of sleep.
REM sleep is crucial since our breathing, blood pressure, pulse rate, and blood flow to the brain all increase during this phase. During REM sleep, our peripheral muscles are atonic.
REM presents a challenge to sustain breathing, oxygenation, and cardiac stability in patients at risk for sleep apnea. Clinical functions all become more difficult to sustain because apneic events are longer during REM, oxygen desaturation is lower, and more cardiac arrhythmias are noted during REM sleep. Since the longest REM period occurs in the early morning hours between 4:00 – 6:00 AM, we need to closely monitor our patients during this time.
Every stage of the health care continuum that provides sedation should implement sedation-related apnea management guidelines. This program will reduce patient risk, reduce medical liabilities, and create additional sleep apnea patient disease management revenue streams for related health professionals. 7
Christopher VuSleep Advoacate
The author is a staff writer for
Sleep Diagnosis and Therapy
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4. Morgenthaler TI, Practice parameters for the use of autotitrating continuous positive airway pressure devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome: an update for 2007. An American Academy of Sleep Medicine report. Sleep. 2008 Jan 1; 31 (1): 141-7.
5. Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea. A report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep Apnea. Anesthesiology 2006; 104:1081-93.
6. Preventing and managing the impact of anesthesia awareness. Sentinel Event Alert Joint Commission on Accreditation of Healthcare Organizations October 6, 2004; Issue 32.