Obstructive Sleep Apnoea (OSA)

Obstructive Sleep Apnoea (OSA) is a sleep related breathing disorder caused by repetitive upper respiratory obstruction to normal breathing pattern. It usually affects the obese individuals although it may also occur in myriad of diseases of the nose and oral cavity. With increasing westernization and adoption of sedentary lifestyle, obesity is no more a public health issue merely limited to the developed countries. Rapid urbanization and adoption of junk food culture, has caused further increase in number of cases with morbid obesity not only among the middle aged and elderly patient, but also the youth in developing country like ours.  Obesity leads to deposition of fat in the upper respiratory tract, which in turn causes these muscles to be weak and collapse during sleep and cause obstruction.

How is OSA caused?

OSA occurs due to narrowing of the upper respiratory tract during sleep. The narrowing may have various reasons including obesity, nasal diseases like deviated nasal septum, large tongue, enlarged adenoids and tonsils etc. However, obesity remains the most common and the most important cause in adults. A normal individual is able to maintain the patency of his respiratory passage during sleep to have an unobstructed breathing. On the other hand, when obesity causes excessive fat deposition in the pharyngeal muscle, the patency is maintained during wakefulness but due to loss of tone of the muscles of the pharynx during sleep, there is repetitive obstruction of the upper respiratory passage. Due to repetitive obstruction to breathing during sleep, the sleep pattern of these individuals is fragmented. They do not have a restorative sleep and manifest with various symptoms of sleep deprivation.

What are the risk factors of OSA?

Obesity is the most important in adults. OSA is also more common in short-necked individuals. Although smoking per se does not cause OSA, it causes chronic obstructive pulmonary disease which has a fatal combination with OSA and may cause rapid deterioration of repiratory failure in susceptible individuals. Alcohol, by causing further decrease in muscle tone can precipitate respiratory obstruction during sleep. In addition, those with OSA have a higher incidence of concomitant diabetes, hypertension and heart disease which are all related to obesity.

What are the symptoms of OSA?

OSA manifests principally as excessive tendency to fall asleep during the daytime at home or work. These episodes of sleepiness are involuntary and unplanned and can lead to decreased performance during work. Road crashes and other work related accidents due to sleepiness are one of the major concerns among drivers and workers who have obstructive sleep apnoea. Other symptoms include generallised fatigue and lack of energy during work.

Obstructive events during sleep may manifest as excessive snoring during sleep usually complained by sleep partners or family members. However, mere presence of snoring does not mean you have obstructive sleep apnea. Loud snorers, however must be evaluated for the presence of OSA as they have higher chances of having the disease as compared to non-snorers. Presence of witnessed choking episodes during sleep is highly suggestive of apnoeic episode during the sleep.

How is OSA diagnosed?

Although the suspicion of OSA is made based on clinical history, the presence of it must be confirmed by an overnight sleep study, also called polysomnography. Polysomnography is done by monitoring the sleep activity and breathing pattern in a lab and the number of obstructions to respiration is counted and reported in terms of Apnoea – Hypopnea Index (AHI). Normal AHI is less than 5 per hour. Those with AHI of 5-15 per hour have mild OSA, those with 15-30 per hour have moderate OSA and those with more than 30 per hour have severe OSA. Most of the times, the polysomnography is followed by a titration study, where a patient with significant AHI is given CPAP (Continuous Positive Airway Pressure) and sleep and respiratory pattern monitored in order to confirm that it improves. This study also helps to determine the exact pressure required in an individual if a CPAP machine is prescribed.

What is the treatment of OSA?

OSA is treated with a positive airway pressure device. The devices are usually connected by a nasal mask and worn during sleep. Various devices which deliver positive pressure to the patients are available in the market. All devices are equally efficacious if used correctly and for the prescribed duration of time. CPAP device remains the preferred treatment for symptomatic patients with OSA. For those with mild OSA and not willing to use CPAP machine, weight reduction remains a good modality to reduce symptoms. Weight reduction is advised in all patients irrespective of whether they use PAP device or not. In addition maintenance of sleep hygiene, sleeping in lateral position also improves OSA.  Dental appliances and position altering devices have also been recommended in select few cases. On the other hand, if OSA is caused due to diseases/deformities in the nasal or oral passage, surgical correction is recommended. Those with morbid obesity benefit from weight reduction surgeries.

Are there any side effects of PAP device?

PAP devices have a very few side effects if weighed against the benefit they provide to OSA patients. However, some patients find PAP therapy to be intolerable. Some patients also complain of dryness of mouth. This can however be avoided by using a humidifier with the PAP device. Ill fitting masks can lead to pressure sores on nose. However, different mask types are available for use and if a patient finds a given mask to be intolerant, they can always switch to another mask system.

About the Author:

Dr. Ashesh Dhungana
MD (Medicine), PGIMER, Chandigarh
DM (Pulmonary, Critical Care and Sleep Medicine), AIIMS, New Delhi