Introduction 

Apnea - complete collapse of upper airway. 

Hypopnea - partial collapse of upper airway. 

Obstructive sleep apnea (OSA) is a sleep disorder characterized by repeated episodes of apnea or hypopnea causing oxygen desaturation or sleep arousal. This leads to fragmented and non restorative sleep. It includes loud snoring, sudden awakening from sleep, excessive daytime sleepiness.  OSA significantly affects cardiac health, behavioral conditions and quality of life.

Causes

OSA is a complex, multifactorial disorder. Sleep-related reductions in ventilatory drive, neuromuscular factors, and anatomical risk factors all contribute significantly to upper airway obstruction during sleep.

Anatomical factors:

An increase in pressure near the upper airway causes pharyngeal collapse (pharyngeal narrowing) leading to insufficient space for airflow in the upper airway during sleep. In addition, when the muscle tone in and around the neck is decreased, it may lead to partial or complete pharyngeal collapse.

• Mandibular hypoplasia - decreased growth of jaw

• Retrognathia - backward positioning of jaw

• Micrognathia - small jaw

• Adenoid or tonsillar hypertrophy

• Inferior positioning of hyoid bone

Non anatomical factors

• Male gender

• Central fat distribution

• Supine sleeping position

• Pregnancy

• Older age 

• Smoking

• Alcoholism

• Usage of sedative and hypnotic drugs

Associated medical conditions

• Endocrine disorders like DM, metabolic syndrome, acromegaly, hypothyroidism

• Neuro related disorders like stroke, myasthenia gravis, spinal cord injury

• Prader Willi syndrome

• Down’s syndrome

• Congenital heart disease

Clinical features

Symptoms 

Patients with OSA often experience excessive daytime sleepiness, loud disruptive snoring during sleep, gasping or choking during sleep (episodes of apnea), daytime fatigue.

Signs 

• Obesity is one of the commonest findings in patients with OSA. 

• A large neck circumference (17 inches or 43 cm in males and 16 inches or 40.5 cm in females)

• Crowded oropharynx 

• Retrognathia, micrognathia

• Tonsillar hypertrophy

• Low-lying palate

• Overjet

• Large tongue

Evaluation 

Epworth Sleepiness Scale

Epworth Sleepiness Score ranges from 0 to 24. A score above 9 suggests excessive daytime sleepiness.

STOP-BANG questionnaire

The STOP-BANG questionnaire can be used to assess the probability of moderate-to-severe OSA. A high risk is indicated if "YES" is selected for 5 or more items, while a low risk is indicated if "YES" is answered for fewer than 3 items.

Polysomnography

Night time laboratory level polysomnography is the gold standard test for evaluation of OSA. during the test, patients are monitored using electroencephalogram (EEG) leads, pulse oximetry, temperature and pressure sensors to detect nasal and oral airflow, respiratory impedance plethysmography belts around the chest and abdomen to monitor motion, an electrocardiogram (ECG) lead, and electromyogram sensors to detect muscle contractions in the chin, chest, and legs.

Scoring respiratory events in adults:

• Oronasal thermal sensor 

• Nasal air pressure transducer 

• Inductance plethysmography (with esophageal manometry or a pressure catheter may be used as alternatives) 

• Pulse oximetry 

Inference:

According to the American Academy of Sleep Medicine (AASM), 

Hypopnea is defined by:

• A reduction in airflow of at least 30% for more than 10 seconds, accompanied by at least 4% oxygen desaturation. (or)

• A reduction in airflow of at least 30% for more than 10 seconds, associated with either at least 3% oxygen desaturation or an arousal from sleep on EEG.

Apnea is defined by:

• A drop in the peak signal excursion by more than or equal to 90% of the pre-event baseline flow.

• A duration of the flow reduction of more than or equal to 10 seconds.

Obstructive sleep apnea: If an increased effort is present throughout the entire apnea.

Central sleep apnea: If no effort is detected throughout the entire apnea.

Mixed apnea: Absence of effort during the initial portion of the event, followed by the resumption of effort in the latter part of the apnea.

Apnea - hypopnea index

The total number of apneas and hypopneas is divided by the total sleep time(hours) to get the events per hour. 

• Mild: 5 to 15 events per hour

• Moderate: Greater than 15 to 30 events per hour

• Severe: Greater than 30 events per hour

Complications

• Hypertension

• Myocardial infarction

• Atrial fibrillation

• Congestive heart failure

• Cerebrovascular accident

• Depression

• Sleeplessness-related accidents

Management

Managing the OSA is a multidisciplinary approach. 

• Treating the underlying medical conditions

• Lifestyle modifications - obesity management -  weight loss, prioritizing 7 to 8 hours of night sleep, avoid alcohols, sedative - hypnotic drugs, smoking etc.

• Positioning therapy: side position sleeping is advised

Continuous positive airway pressure therapy cPAP

It is most effective for adults. It involves using a machine to deliver mild air pressure through a mask, keeping the airways open during sleep. This prevents airway collapse and ensures uninterrupted breathing.

Oral appliance

Mandibular advancement devices (MAD) can help alleviate airway obstruction by advancing the lower jaw. 

This approach is typically most effective for candidates with appropriate dentition and mild-to-moderate sleep apnea. 

The AASM and the American Academy of Dental Sleep Medicine (AADSM) have developed guidelines for using MAD in patients with OSA.

• Oral appliances can be considered as an alternative to no treatment for adult patients with snoring (without OSA) or those with OSA who do not tolerate CPAP therapy or prefer an alternative treatment.

• When a sleep physician prescribes oral appliance therapy for an adult patient with OSA, a qualified dentist should use a custom, titratable appliance.

• A follow-up with a qualified dentist is necessary to assess for dental-related adverse effects after initiating oral appliance therapy in adult patients with OSA.

• Follow-up sleep testing is required to confirm the efficacy of the treatment.

Surgical approaches

• Tonsillectomy or adenoidectomy for their hypertrophy

• Uvulopalatophrayngoplasty - surgical removal of the uvula and tissue from the soft palate to create more space in the oropharynx

• Maxillomandibular advancement surgeries

• Distraction osteogenesis for mandibular advancements in young patients

• Hypoglossal nerve stimulation

• In extreme cases, tracheostomy to bypass oropharyngeal obstruction

Conclusion 

Managing OSA is most effectively achieved through an interprofessional team that includes a sleep specialist, dentist, cardiologist, otolaryngologist, dietitian, pulmonologist, neurologist, etc. Several treatment options are available for OSA, with the primary treatment being CPAP.

Adherence to CPAP use should be strongly encouraged, along with proper cleaning and maintenance of the machine to ensure optimal function.

Patients should also be educated on the importance of proper sleep hygiene, ensuring sufficient sleep each night, and the risks of driving while drowsy. 

The short-term prognosis of OSA with treatment is generally favorable, but the long-term outlook remains uncertain. 

The primary challenge is poor adherence to CPAP therapy, with nearly 50% of patients discontinuing its use within the first month despite education.

Many individuals with OSA have comorbidities or are at an increased risk for adverse cardiac events and stroke. 

Consequently, individuals who do not adhere to CPAP are at a higher risk for cardiac and cerebral events, as well as increased annual healthcare-related costs.