This site is intended for healthcare professionals
Sleep Apnea Learning Zone

Obstructive & Positional Obstructive Sleep Apnea

Read time: 40 mins
Last updated:12th Mar 2020

Obstructive sleep apnea (OSA)

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder. OSA is characterised by recurrent obstruction of the pharyngeal airway during sleep, resulting in reduced (hypopnea) or complete cessation (apnea) of airflow despite ongoing breathing efforts. These disruptions to breathing lead to intermittent oxygen desaturation, sleep disturbance, and sympathetic activation (Strollo et al., 1996). Consequences of OSA include excessive daytime sleepiness, fatigue, reduced quality of life, increased risk of traffic and occupational accidents and increased risk of developing cardiovascular disease. When patients experience most of their apneic events in the supine sleep position, the term of positional obstructive sleep apnea (POSA) is used.

Visit different sections within the Obstructive Sleep Apnea Learning Zone to find out more about the epidemiology, pathophysiology, symptoms and diagnosis and current treatment options.

Obstructive sleep apnea epidemiology

Before we discuss the epidemiology, let us consider what obstructive sleep apnea (OSA) actually looks like.

Figure 1 shows evidence of snoring on the flow tracing preceding the apneic event during which oxygen saturation progressively falls.


In this example, despite a lowered arousal threshold and progressive increases in EMGgg activity throughout the obstructive event, airflow was not able to be restored without an arousal (awakening) (Eckert & Malhotra, 2008). Learn more about the events that lead to OSA in the pathophysiology section.


Register free for full access to

Obstructive sleep apnea pathophysiology

An obstructive sleep apnea (OSA) episode occurs when the soft tissues of the upper airway and tongue relax during sleep and block the flow of air into the lungs. These disruptions to breathing lead to intermittent blood gas disturbances (hypercapnia and hypoxemia) and are associated with increasing respiratory efforts and a brief awakening from sleep (arousal).

Finally, pharyngeal activity is restored, the airway opens and hyperventilation occur in an attempt to recover oxygen and carbon dioxide levels and the patient fall back to sleep (figure 4). This does not happen during wakefulness as there is a protective mechanism which maintain the airway patency (Jyothi et al., 2019).



Register free for full access to

Positional sleep apnea pathophysiology

POSA is associated with increased waist-to-hip ratio in men (Heinzer et al., 2018). This suggests that abdominal obesity in men may induce POSA by pulling up the diaphragm in the supine position, which in turn decreases the tension exerted on the pharyngeal walls through the mediastinum, favouring pharyngeal collapse (Heinzer et al., 2018).

In addition, lung volume also plays a role in POSA as a higher positive airway pressure is required to keep the airway open when lung volume is reduced (Heinzer et al., 2005).

Register free for full access to

Obstructive sleep apnea symptoms and diagnosis

Obstructive sleep apnea symptoms


Sleep apnea is insidious, and patients are often unaware of their associated symptoms. As a result, it often goes undiagnosed or is first noticed by others due to habitual loud snoring combined with daytime sleepiness.


Register free for full access to

Current obstructive sleep apnea treatment options

Treatment is recommended for all patients with an AHI or respiratory-event index of ≥15 events per hour or 5–14 events per hour with symptoms of sleepiness, impaired cognition, mood disturbance or insomnia or with pre-existing conditions such as hypertension, ischaemic heart disease or a history of stroke (Veasey & Rosen, 2019).


Studies have shown evidence for body weight as an important factor in determining the evolution of sleep apnea. In the Sleep Heart Health Study, compared with a stable weight over treatment follow-up, men with a weight gain more than 10 kg had a 5.2-fold increase in AHI. For a comparable gain in weight, women had a 2.5-fold risk of AHI increase (Punjabi et al., 2008). Although weight loss is recommended (ELF, 2019) and known to decrease severity of OSA, it is commonly difficult to achieve and sustain.


Register free for full access to

Obstructive sleep apnea disease awareness references

AASM. AASM clarifies hypopnea scoring criteria 2013. Available at: (accessed May 2019).

AASM. Economic burden of undiagnosed sleep apnea in U.S. is nearly $150B per year. 2016. Available at: (accessed May 2019).

American Sleep Apnea Association. Children’s Sleep Apnea. 2017. Available at: (accessed May 2019).

Bonsignore MR, Randerath W, Riha R, Smyth D, Gratziou C, Marta G et al. New rules on driver licensing for patients with obstructive sleep apnoea: EU Directive 2014/85/EU. European Respiratory Journal 2016;47:39-41.

Caples SM, Rowley JA, Prinsell JR, Pallanch JF, Elamin MB, Katz SG, et al. Surgical modifications of the upper airway for obstructive sleep apnea in adults: a systematic review and meta-analysis. Sleep. 2010;33(10):1396–407.

Carberry JC, Amatoury J, Eckert DJ. Personalized Management Approach for OSA. Chest. 2018;153(3):744-755.

Cartwright RD. Effect of sleep position on sleep apnea severity. Sleep. 1984;7(2):110­4.

Cartwright R, Ristanovic R, Diaz F, Caldarelli D, Alder G. A comparative study of treatments for positional sleep apnea. Sleep. 1991;14(6):546–52.

de Ruiter MHT, Benoist LBL, de Vries N, de Lange J. Durability of treatment effects of the Sleep Position Trainer versus oral appliance therapy in positional OSA: 12-month follow-up of a randomized controlled trial. Sleep and Breathing. 2018;22(2):441–450.

Doff MH, Veldhuis SK, Hoekema A, Slater JJ, Wijkstra PJ, de Bont LG et al. Long-term oral appliance therapy in obstructive sleep apnea syndrome: a controlled study on temporomandibular side effects. Clin Oral Investig. 2012;16(3):689–97.

Doff MH, Finnema KJ, Hoekema A, Wijkstra PJ, de Bont LG, Stegenga B. Long-term oral appliance therapy in obstructive sleep apnea syndrome: a controlled study on dental side effects. Clin Oral Investig. 2013;17(2):475–82.

Eckert DJ, Malhotra A. Pathophysiology of adult obstructive sleep apnea. Proc Am Thorac Soc. 2008;5(2):144—53.

ELF. Sleep apnoea. 2019. Available at: (accessed May 2019).

ELF/ERS. Sleep-disordered breathing. 2013 Available at: (accessed May 2019).

Faccenda JF, Mackay TW, Boon NA, Douglas NJ. Randomized placebo-controlled trial of continuous positive airway pressure on blood pressure in the sleep apnea-hypopnea syndrome. Am J Respir Crit Care Med. 2001;163(2):344–8.

Fogel RB, Malhotra A, White DP. Sleep 2: Pathophysiology of obstructive sleep apnoea/hypopnoea syndrome. Thorax. 2004;59:159–163.

George CF. Reduction in motor vehicle collisions following treatment of sleep apnoea with nasal CPAP. Thorax. 2001;56(7):508–12.

Heinzer RC, Stanchina ML, Malhotra A, Fogel RB, Patel SR, Jordan AS et al. Lung volume and continuous positive airway pressure requirements in obstructive sleep apnea. Am J Respir Crit Care Med. 2005;172(1):114­7.

Heinzer R, Petitpierre NJ, Marti-Soler H, Haba-Rubio J. Prevalence and characteristics of positional sleep apnea in the HypnoLaus population-based cohort. Sleep Medicine. 2018;48,157–162.

Ibáñez V, Silva J, Cauli O. A survey on sleep assessment methods. Peer J. 2018;6:e4849.

Jehan S, Auguste E, Zizi F, Pandi-Perumal SR, Gupta R, Attarian H et al. Obstructive sleep apnea: Women’s perspective. J Sleep Med Disord. 2016;3(6):1064–1082.

Jyothi I, Renuka Prasad K, Rajalakshmi R, Satish Kumar RC, Ramphanindra T, Vijayakumar TM et al. Chapter 2. Obstructive sleep apnea: A pathophysiology and pharmacotherapy approach. In Noninvasive Ventilation in Medicine - Recent Updates. 2019. Available at: (accessed April 2019).

Mador MJ, Kufel TJ, Magalang UJ, Rajesh SK, Watwe V, Grant BJ. Prevalence of positional sleep apnea in patients undergoing polysomnography. Chest 2005;128:2130–7.

Mayo Clinic. Sleep apnea. 2019. Available at: (accessed May 2019).

Oksenberg A, Silverberg DS, Arons E, Radwan H. Positional vs nonpositional obstructive sleep apnea patients: anthropomorphic, nocturnal polysomnographic, and multiple sleep latency test data. Chest. 1997;112(3):629–39.

Osman AM, Carter SG, Carberry JC, Eckert DJ. Obstructive sleep apnea: current perspectives. Nature and Science of Sleep. 2018;10:21–34.

Patil SP, Ayappa IA, Caples SM, Kimoff RJ, Patel SR, Harrod CG. Treatment of adult obstructive sleep apnea with positive airway pressure: An American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2019 Feb 15;15(2):335–343.

Phillips CL, Grunstein RR, Darendeliler MA, Mihailidou AS, Srinivasan VK, Yee BJ, et al. Health outcomes of continuous positive airway pressure versus oral appliance treatment for obstructive sleep apnea: a randomized controlled trial. Am J Respir Crit Care Med. 2013 Apr 15;187(8):879–87.

Peppard PE, Young T, Barnet JH, Palta M, Hagen EW, Hla KM. Increased prevalence of sleep-disordered breathing in adults. Am J Epidemiol. 2013;177(9):1006–14.

Punjabi NM. The epidemiology of adult obstructive sleep apnea. Proc Am Thorac Soc. 2008;5(2):136–43.

Shah N, Roux F. The relationship of obesity and obstructive sleep apnea. Clin Chest Med. 2009;30(3):455–65.

Siccoli MM, Pepperell JCT, Kohler M, Craig SE, Davies RJO, Stradling JR. Effects of continuous positive airway pressure on quality of life in patients with moderate to severe obstructive sleep apnea: Data from a randomized controlled trial. Sleep. 2008;31(11):1551–1558.

Slowik JM, Collen JF. Obstructive Sleep Apnea [Updated 2019 Mar 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: (accessed April 2019).

Strollo PJ Jr, Rogers RM. Obstructive sleep apnea. N Engl J Med. 1996;334(2):99–104.

Tomfohr LM, Ancoli-Israel S, Loredo JS, Dimsdale JE. Effects of continuous positive airway pressure on fatigue and sleepiness in patients with obstructive sleep apnea: data from a randomized controlled trial. Sleep. 2011;34(1):121–6.

van Maanen JP, Meester KA, Dun LN, Koutsourelakis I, Witte BI, Laman DM et al. The sleep position trainer: a new treatment for positional obstructive sleep apnoea. Sleep Breath. 2013;17(2):771–9.

Veasey SC, Rosen IM. Obstructive sleep apnea in adults. N Engl J Med. 2019;380(15):1442–1449.

Vecchierini MF, Attali V, Collet JM, d'Ortho MP, El Chater P, Kerbrat JB et al. A custom-made mandibular repositioning device for obstructive sleep apnoea-hypopnoea syndrome: the ORCADES study. Sleep Med. 2016;19:131–40.

White DP. Advanced Concepts in the Pathophysiology of Obstructive Sleep Apnea. Adv Otorhinolaryngol. 2017;80:7–16.

Woodson BT, Strohl KP, Soose RJ, Gillespie MB, Maurer JT, de Vries N et al. Upper airway stimulation for obstructive sleep apnea: 5-Year outcomes. Otolaryngol Head Neck Surg. 2018;159(1):194–202.

Young T, Peppard PE, Gottlieb DJ. Epidemiology of obstructive sleep apnea: a population health perspective. Am J Respir Crit Care Med. 2002;165(9):1217–39.

Young T, Palta M, Dempsey J, Peppard PE, Nieto FJ, Hla KM. Burden of sleep apnea: rationale, design, and major findings of the Wisconsin Sleep Cohort study. WMJ. 2009;108(5):246–9.

Zaghi S, Holty JE, Certal V, Abdullatif J, Guilleminault C, Powell NB et al. Maxillomandibular advancement for treatment of obstructive sleep apnea: A meta-analysis. JAMA Otolaryngol Head Neck Surg. 2016;142(1):58–66.