Case Studies

Dr. Zarir Udwadia MD, MRCP, FCCP
Consultant Chest Physician

P. D. Hinduja National Hospital.

History / Patient Profile

Mr XYZ is a successful businessman but is not exactly enjoying his work these days. That’s because he feels extremely drowsy during the day and very often goes off to sleep in important business meetings and is quite embarrassed about it. He finds it very difficult to stay awake specially in the afternoons and once also dozed off while driving and almost met with an accident. His wife complains that he snores VERY loudly which disturbs her sleep and has also noticed that he stops breathing intermittently during sleep….. Does this sound familiar???

Yes, this is not an uncommon condition but is often not reported to doctors as very few people are aware of it being a pathological condition. It is called OBSTRUCTIVE SLEEP APNEA SYNDROME (OSAS) and epidemiological studies have established a prevalence of clinically significant apneas of at least 2% in middle-aged women and 4% in middle aged men.

Definition and Classification:

Sleep apnea is defined as complete cessation of airflow at the nose and mouth during sleep for at least 10 seconds. Hypopnea refers to reduction of airflow by more than 50% of normal again lasting for 10 seconds and associated either with arousal or accompanied by a fall in saturation by 4%. Sleep apneas have been classified into 3 types: central, obstructive 0 and mixed. In central sleep apnea, the neural drive to all the respiratory muscles is transiently abolished. In contrast, in obstructive sleep apnea (OSA) airflow ceases despite continuing respiratory drive because of occlusion of oropharyngeal airway. Mixed apneas which consist of a central apnea followed by an obstructive component, are a variant of OSA. The number of apnea-hypopnea in an hour is called apnea-hypopnea index (AHI). AHI of >5/hour along with symptoms of excessive daytime sleepiness constitutes the syndrome of OSA.

Pathophysiology:

The definitive event in OSA is occlusion of the upper airway usually at the level of oropharynx. The resulting apnea leads to progressive asphyxia until there is brief arousal from sleep whereupon airflow patency is restored and airflow resumes. The patient then returns to sleep and the sequence of events is repeated, often up to 400 to 500 times per night, resulting in marked fragmentation of sleep.

The immediate factor leading to collapse of upper airway in OSA is the generation of a critical sub-atmospheric pressure during inspiration that exceeds the ability of the airway dilator and abductor muscles to maintain airway stability. Sleep plays a permissive but crucial role by reducing the activity of the muscles of the upper airways and the protective reflex response of the muscles to sub-atmospheric airway pressures. Alcohol is frequently an important cofactor because of its selective depressant influence on the upper airway muscles and on the arousal response that terminates each apnea. In most patients the patency of the airways is also compromised structurally and therefore predisposed to occlusion. In a minority of patients the structural compromise is due to obvious anatomic disturbances like adenotonsillar hypertrophy, retrognathia and macroglossia.

Obesity frequently contributes to the reduction in the size of upper airways either by increasing fat deposition in the soft tissues of the pharynx or by compressing the pharynx by superficial fat masses in the neck. Apneic events are associated with a number of acute physiologic changes including hypoxemia and hypercapnia. Large swings in intrathoracic pressures occur before the occluded airway opens. Heart rate, systemic arterial pressures and pulmonary arterial pressures increase markedly at the termination of apneas. Sleep architecture is disturbed markedly with apneic events often ending in arousals.

Clinical Features:

• Snoring - Almost always present, frequently very loud, invariably disturbs the partner and sometimes can also be heard through a closed door. Particularly loud snoring, snorting, choking or explosive sounds often occur at the termination of an observed apnea. A history of apneas observed by a bed partner is a strong indicator that sleep apnea is present.
• Excessive daytime sleepiness (EDS) - Can be presenting complaint but is sometimes absent or poorly perceived by the patients. Sleepiness may be longstanding and may be considered normal by the patient and hence specific questions should be directed to both the patient and the family members regarding sleepiness in sedentary situations such as driving long distances, reading or watching television.
• Fatigue or tiredness -This could be the only complaint specially in women.
  Insomnia - Patients may complain of difficulty in getting sleep or of numerous brief awakenings, restless sleep and may even have heavy nocturnal sweating.
• Nocturia - It is common and is as a result of excessive levels of atrial natriuretic factor with some patients waking up 4-7 times to pass urine.
• Others - Dry mouth on awakening, frequent morning headaches, erectile dysfunction or decreased libido, complaints consistent with nocturnal gastroeosophageal reflux, memory deficits or distractibility and changes in personality and mood.

On Examination:

Important features to consider are

• Obesity
• Body mass index >30
• Neck circumference >16 inches
• Rule out presence of low extending soft palate, large uvula, large tonsils or adenoids, retrognathia, prognathia, micrognathia, macroglossia or other disproportionate facial anomaly.

Diagnosis:

The typical patient is a male aged 30-60 years who presents with a history of snoring, excessive daytime sleepiness, nocturnal choking or gasping witnessed apneas during sleep, moderate obesity and often mild to moderate hypertension.

The definitive investigation is polysomnography, a detailed overnight sleep study that includes recording of

• Electrographic variables (EEG, ECG and submental EMG) that permit identification of sleep and its various stages
• Ventilatory variables with the help of thermistors at the nose and mouth that detect airflow and abdominal and thoracic belts which detect respiratory excursions and permit identification of apneas and hypopneas and their classification as central or obstructive
• Arterial oxygen saturation by ear or finger oximetry.

The key specific finding in OSAS is episodes of airflow cessation at the nose and mouth despite evidence of continuous respiratory effort. Microphones can also be used to record snoring and a video system can also be used for visual record of movements or behaviour during the night.

On the basis of polysomnography results, OSAS can be graded as mild, moderate or severe.

Patients with mild OSAS can be advised weight reduction, avoidance of alcohol and avoidance of sleeping in supine position. Intraoral appliances, designed to keep the mandible and tongue forward may also be effective.

The most effective treatment for patients with moderate to severe degrees of OSAS is the use of continuous positive airway pressure (CPAP). Nasal CPAP which prevents upper airway occlusion by splinting the pharyngeal airway with a positive pressure delivered through a nose mask is currently the most successive long term approach to treatment. Alternatively BIPAP which allows higher pressure during inspiration and a lower but still positive pressure during expiration is also equally effective and is also better tolerated by the patient. Uvulopalatopharyngoplasty (UVPP) is a surgical procedure designed to increase the pharyngeal lumen by resecting reductant soft tissue, however when applied to unselected patients of OSAS, it produces long term benefits in only 50% patients. Very few patients of OSAS now require tracheostomy which used to be the procedure of choice earlier before the advent of CPAP.

Complications of moderate-severe OSAS if untreated:

• Intelectual deterioration, personality changes, behavioral disorders
• Systemic hypertension
• Myocardial ischaemia and infarction
• Stroke
• Left heart failure
• Pulmonary hypertension and right heart failure
• Unexplained nocturnal death

Patient's Course

Mr. XYZ underwent polysomnography at the sleep laboratory of Hinduja Hospital. This confirmed a severe degree of OSA with marked desaturation through the night.
He was commenced on CPAP therapy and after regular use every night his life has been transformed. There is no snoring or daytime drowsiness and his work is more productive.