pulmonary disorders
Obstructive Sleep Apnea (OSA)
Pathophysiology of Obstructive Sleep Apnea (OSA)
Obstructive sleep apnea involves a compromise in upper airway anatomy during sleep. Sleep destabilizes patency of the upper airway, leading to partial or complete obstruction of the nasopharynx, oropharynx, or both. Airway patency tends to oscillate causing recurrent periods of apnea and recovery. Obstruction causes multiple episodes of apnea or hypopnea, which lead to hypoxia and hypercapnia, all of which disrupt normal sleep, with partial or complete arousals from nonrapid eye movement (NREM) and rapid eye movement (REM) sleep ( Pathophysiology references ). Inspiratory efforts against a closed upper airway cause swings in intrathoracic pressure that affect cardiac performance. Endothelial and neurotransmitter dysfunction occur. All factors interact to produce significant morbidity and mortality. Less severe forms may not produce oxygen desaturation, but they interrupt sleep. Obstructive sleep hypopneais a condition in which inspiratory flow is diminished, but not absent, in a high resistance airway. Upper airway resistance syndromeis crescendo snoring terminated by snorts and respiratory effort-related arousals (RERAs). Breathing reductions do not meet strict criteria for obstructive apneas and hypopneas. Patients with upper airway resistance syndrome are typically younger and have less obesity than those with OSA. Patients are more often female, report fatigue, and complain of insomnia. Snoring and upper airway airflow resistance cause noisy inspiration but without arousals from sleep lasting > 2 seconds. Symptoms, diagnostic evaluation, and treatment of snoring and upper airway resistance syndrome are similar to those of OSA. Obstructive sleep apnea is the leading medical cause of excessive daytime sleepiness. A more correct term is wake-time excessive sleepiness, because people who work during the night may be excessively sleepy during night hours. The excessive sleepiness actively increases risk of automobile crashes, difficulties at work, and sexual dysfunction. There is often some degree of cognitive impairment and also increased risk of injury (eg, when operating heavy machinery or engaging in other activities during which unintentional sleep episodes would be hazardous). Relationships with bed partners, roommates, and/or housemates may also be adversely affected because such people may have difficulty sleeping because of the patient's noisy, restless sleep. Severe OSA (apnea-hypopnea index > 30 per hour) increases the risk of death in middle-aged men. OSA also has medical risks unrelated to excessive sleepiness. Hypertension is strongly associated with OSA ( Pathophysiology references ). Normotensive patients with untreated OSA are more likely to develop hypertension within 5 years of diagnosis. Repetitive nocturnal hypoxia and sleep disruption are associated with increased risk of medical disorders, including In addition, perioperative complications, including cardiac arrest, occur with unrecognized OSA, because moderate and general anesthesia is a risk for airway obstruction. Patients should inform an anesthesiologist of the diagnosis before undergoing any surgery and should receive continuous positive airway pressure (CPAP) when they receive preoperative drugs and during recovery. 1.Zinchuk AV, Gentry M , Concato J, et al: Phenotypes in obstructive sleep apnea: A definition, examples and evolution of approaches.Sleep Med Rev35:113-123, 2017. doi: 10.1016/j.smrv.2016.10.002 2.Van Ryswyk E, Mukherjee S, Chai-Coetzer CL, et al: Sleep disorders, including sleep apnea and hypertension.Am J Hypertens31(8):857-864, 2018. doi: 10.1093/ajh/hpy082 3.Zinchuk AV, Jeon S, Koo BB, et al: Polysomnographic phenotypes and their cardiovascular implications in obstructive sleep apnoea.Thorax73(5):472–480, 2018. doi: 10.1136/thoraxjnl-2017-210431 4.Yaggi HK, Concato J, Kernan WN, et al: Obstructive sleep apnea as a risk factor for stroke and death.N Engl J Med353(19):2034-2041, 2005. doi:10.1056/NEJMoa043104 5.Borsoi L, Armeni P, Donin G, et al: The invisible costs of obstructive sleep apnea (OSA): Systematic review and cost-of-illness analysis.PLoS One17(5):e0268677, 2022. doi: 10.1371/journal.pone.0268677 