The pathophysiology of obstructive sleep apnoea relates to respiratory effort to overcome the critical pressure in the nasopharynx, caused by airway obstruction during sleep resulting in arousal and/ or a drop in blood oxygen levels.(1)
OSA is associated with the development of chronic diseases such as hypertension and ischemic heart disease, stroke, diabetes mellitus and depression. (2) A seven-fold increased risk of road traffic accidents (10) and an increased risk of occupational accidents (2) has been reported. OSA is associated with reduced in work performance. (3)
There is an estimated 8 million cases of OSA in the UK and close to 1 billion cases worldwide. The prevalence increases with increasing age and obesity. (4) A population-based study using diagnostic polysomnography (PSG), the gold standard for diagnosis, demonstrated a high confirmed prevalence of OSA in men (49.7%), and in women (23.4%) of middle age. (5)
Legislation requires screening of drivers for OSA, which could also be applicable to other safety critical workers: A position paper by the British Thoracic Society and DVLA provides guidance on OSA and driving in the UK. (6) The EU produced a directive mandating drivers to have OSA screening. (7) US legislation states that the driver must have “no established medical history or clinical diagnosis of respiratory dysfunction likely to interfere with the ability to control and drive a commercial motor vehicle safely’ and recommends OSA screening following sleep related incidents and BMI parameters in combination with chronic disease. (8)
Polysomnography is the gold standard in diagnosis, but needs to be done in hospital and is costly. Home based sleep testing (HBST) could be used to diagnose moderate to severe OSA but cases that test negative with symptoms would still be referred for PSG studies. Moderate to severe OSA, once diagnosed, is generally treated with CPAP (continuous positive airway pressure) and mandibular devices. (2) Other measures such as surgery and implantable pacemakers are less often used. Mild OSA could be managed with conservative measures including weight loss, reduced alcohol intake and smoking cessation. Body positioning during sleep is a factor in airway collapse with increased body fat playing a part. Minimal weight loss of a few kg can improve OSA severity and reduce morbidity associated with the condition.
The severity of OSA is expressed as the Apnoea Hypopnoea Index, or AHI, which is used in diagnostic reports (mild, an AHI of 5 to <14.9; moderate, an AHI of 15 to 29.9 and severe, an AHI of 30 and over). The AHI is measured with an airflow probe at the nose. A key parameter in oximetry to describe oxygen desaturation events in OSA is the oxygen desaturation index, or ODI, which is defined as a 3% – 4% reduction in blood oxygen saturation (SpO2) from baseline, lasting for 10 seconds or more per hour. An ODI of 5 or more is considered abnormal. The ODI alone is not accepted to make a diagnosis but it could be used to screen for OSA.
Using screening questionnaires only has been shown to be inadequate to screen for OSA. (9) The sensitivity and specificity percentages for questionnaires to identify OSA are 77 (73-81) and 44 (38-51) for the Berlin questionnaire; 90 (86-93); 36 (29-44) for the STOP-BANG questionnaire and 47 (35-59); 62 (56-68) for the Epworth sleepiness scale. (10)
The usefulness of combining oximetry with clinical scoring in screening for OSA has already been demonstrated by Williams in 1991, with the cyclical desaturation pattern of oximetry recordings being highly specific for OSA. (11)
Smartphone apps (with an external probe) or devices not medically certified should not be used in assessment of oxygen parameters. Only medically certified oximetry devices should be used; these devices are subjected to rigorous testing against blood gas analysis over an SpO2 range of 70%-100% before FDA and CE certification.
A two-step approach, combining a sleep apnea questionnaire response with oximetry that is able to identify mild cases of OSA, has been suggested (12,13,14) A negative oximetry result of less than five 3% desaturation events per hour (a 3% ODI<5) together with a negative questionnaire response in a two-step approach, has been shown to reduce the referral rate to sleep centers for PSG, while no cases of OSA were missed if oximetry is combined with a questionnaire response. (15) Other causes of symptoms of sleepiness, such as insufficient sleep, restless legs syndrome, shift work, sedating drugs and psychological conditions should be excluded in the patient history. A negative oximetry response alone is not sufficient to exclude a diagnosis of OSA, and patients with a positive history still require investigation. A negative oximetry result is more prevalent with a lower body mass index (a BMI< 25) and younger patients, and these cases should especially be assessed for other causes of upper airway obstruction.
Cases with significant underlying cardiorespiratory disease, hypoventilation or respiratory muscle weakness, severe insomnia or chronic opioid medication use should not be included in OSA screening programs using oximetry, and such cases need to be referred directly to sleep centers for further assessment.(16)
Employees do not always report symptoms at employment related medical assessments because of their concerns of potential impact on their job; it is therefore necessary to encourage self-reporting of symptoms, raise awareness of the impact on safety and to use objective measures in OSA screening programmes., for example body mass index,, neck circumference, witnessed episodes of apnoea and SpO2 parameters.
A suggested screening programme is outlined in Figure 1.
Take home points for the Occupational Health setting:
- Obstructive sleep apnoea (OSA) is a highly prevalent condition, almost 1 billion worldwide and an estimated 8 million having the condition in the UK, obesity, age over 50 years, male gender and obesity is associated with increased prevalence.
- OSA reduces quality of life, causes fatigue and sleepiness, cognitive impairment, insomnia, OSA is associated with depression, heart disease, stroke and diabetes
- OSA is treatable with CPAP, mandibular devices and surgery in selective cases, mild sleep apnoea could respond to conservative measures such as smoking cessation, limited alcohol use, weight loss and exercise.
- OSA causes disturbed sleep at night affecting daytime functioning significantly in some cases, the condition affects job performance and safety, one study showed an almost seven fold increased risk in accidents. DVLA guidance is based on self-reports of sleepiness.
- Occupational health nurse (OHN) is in a key position to screen for OSA and improve the health of their workforce, screening questionnaires are insufficient.
- Two-night oximetry based screening has been shown to screen adequately in populations with a high prevalence of obstructive sleep apnoea and low comorbidities, in combination with a screening questionnaire
- The less complicated the screening process the better, a wrist sensor device improves patient compliance and comfort over fingertip and nasal probes
- The OHN could provide wellbeing education such as weight loss, smoking and drinking habits and follow cases up over time
- Dempsey JA, Veasey SC, Morgan BJ, O’Donnell CP. Pathophysiology of Sleep Apnea. Physiological Reviews. 2010 Jan;90(1).
- NICE. Obstructive sleep apnoea syndrome. 2021. Available at: https://cks.nice.org.uk/topics/obstructive-sleep-apnoea-syndrome/ Date accessed: Nov 2021
- Ulfberg J, Carter N, Talbäck M, Edling C. Excessive Daytime Sleepiness at Work and Subjective Work Performance in the General Population and Among Heavy Snorers and Patients With Obstructive Sleep Apnea. Chest. 1996 Sep;110(3).
- Benjafield A v, Ayas NT, Eastwood PR, Heinzer R, Ip MSM, Morrell MJ, et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. The Lancet Respiratory Medicine. 2019 Aug;7(8).
- Heinzer R, Vat S, Marques-Vidal P, Marti-Soler H, Andries D, Tobback N, et al. Prevalence of sleep-disordered breathing in the general population: the HypnoLaus study. The Lancet Respiratory Medicine. 2015 Apr;3(4).
- British Thoracic Society. Position statement driving and obstructive sleep apnoea (OSA) 2018. https://www.brit-thoracic.org.uk/quality-improvement/clinical-resources/sleep/. 2018.
- Commission Directive 2014/85/EU. https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014L0085&from=EN Jul 1, 2014.
- Hartenbaum N, Collop N, Rosen IM, Phillips B, George CFP, Rowley JA, et al. Sleep Apnea and Commercial Motor Vehicle Operators. Chest. 2006 Sep;130(3).
- Behar JA, Palmius N, Li Q, Garbuio S, Rizzatti FPG, Bittencourt L, et al. Feasibility of Single Channel Oximetry for Mass Screening of Obstructive Sleep Apnea. EClinicalMedicine. 2019 May;11.
- Gottlieb DJ, Punjabi NM. Diagnosis and Management of Obstructive Sleep Apnea. JAMA. 2020 Apr 14;323(14).
- Williams AJ, Yu G, Santiago S, Stein M. Screening for Sleep Apnea Using Pulse Oximetry and A Clinical Score. Chest. 1991 Sep;100(3).
- Eijsvogel MM, Wiegersma S, Randerath W, Verbraecken J, Wegter-Hilbers E, van der Palen J. Obstructive Sleep Apnea Syndrome in Company Workers: Development of a Two-Step Screening Strategy with a New Questionnaire. Journal of Clinical Sleep Medicine. 2016 Apr 15;12(04).
- Chai-Coetzer CL, Antic NA, Rowland LS, Catcheside PG, Esterman A, Reed RL, et al. A simplified model of screening questionnaire and home monitoring for obstructive sleep apnoea in primary care. Thorax. 2011 Mar 1;66(3).
- Gurubhagavatula I, Maislin G, Nkwuo JE, Pack AI. Occupational Screening for Obstructive Sleep Apnea in Commercial Drivers. American Journal of Respiratory and Critical Care Medicine. 2004 Aug 15;170(4).
- Fabius TM, Benistant JR, Pleijhuis RG, van der Palen J, Eijsvogel MMM. The use of oximetry and a questionnaire in primary care enables exclusion of a subsequent obstructive sleep apnea diagnosis. Sleep and Breathing. 2020 Mar 6;24(1).
- Kapur VK, Auckley DH, Chowdhuri S, Kuhlmann DC, Mehra R, Ramar K, et al. Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline. Journal of Clinical Sleep Medicine. 2017 Mar 15;13(03).
Dr Stipp is a full time consultant occupational physician practicing in the UK private sector with an interest in sleep conditions. He is the co-founder of Divity Health, a UK company aiming to do digital transformation in occupational health