Obstructive Sleep Apnoea Syndrome Flashcards
What is Obstructive Sleep Apnoea Syndrome (OSAS)?
A clinical condition in which there is intermittent and repeated upper airway collapse during sleep
How is complete apnoea defined?
10-second pause in breathing activity
How is partial apnoea defined?
10-second period where ventilation is reduced by at least 50%
What is partial apnoea also known as?
Hypoapnoea
What is the normal sleep/wake cycle in adults divided into?
- REM
- Non-REM
- Consciousness
In what state are the muscles of the throat and neck in REM sleep?
Completely attenuated
What does attenuation of the throat and neck muscles in REM sleep allow?
Relaxation of the tongue, soft palate and oropharynx
What does relaxation of the throat structures cause in sleep apnoea?
Impedance of the flow of air to a degree ranging from light snoring to complete collapse
What happens if sleep apnoea causes blood oxygen levels to fall or exertion of breathing to become too great?
Neurological mechanisms trigger a sudden interruption of sleep
What is the sudden interruption of sleep that can occur in sleep apnoea called?
Neurological arousal
What does neurological arousal normally result in?
Negative effect on the restorative quality of sleep (rarely complete awakening)
What are most cases of OSAS believed to best caused by?
- Old age
- Brain injury
- Decreased muscle tone
- Increased soft tissue around airway
- Structural features that give rise to a narrowed airway
What can cause decreased muscle tone leading to OSAS?
- Drugs or alcohol
- Neurological problems
What can cause increased soft tissue around airway?
Obesity
What are the risk factors for OSAS?
- Obesity
- Male gender
- Aged 55-59 in men
- Aged 60-64 in women
- Smoking
- Sedative drugs
- Excessive alcohol consumption
- Family history
What other conditions are associated with OSAS?
- Hypertension
- Cardiovascular disease
- Obesity
- Metabolic syndrome
- Diabetes
- Asthma
How can sleep apnoea present?
- Snoring
- Witnessed apnoea
- Symptoms of sleep fragmentation
What are some symptoms of sleep fragmentation that can occur in OSAS?
- Excessive daytime sleepiness
- Impaired concentration
- Unrefreshing sleep
- Irritability/personality change
How is OSAS clinically defined?
As 5 or more respiratory events per hour in association with sleep disordered breathing
What is meant by respiratory events in the clinical definition of OSAS?
- Apnoea
- Hypoapnoea
- Arousals
What are some potentially noteworthy findings on examination for OSAS?
- Obesity
- Fat deposition anterolateral to the airway
- Large neck circumference
- Certain craniofacial or pharyngeal abnormalities associated with OSAS
What craniofacial and pharyngeal abnormalities are associated with OSAS?
- Micrognathia
- Enlarged tonsils
- Macroglossia
How is OSAS diagnosed?
Through varying levels of nocturnal monitoring of respiratory, sleep and cardiac parameters
What is the aim of the varying monitoring methods in diagnosing OSAS?
To detect obstructive events and the following changes in blood oxygen saturation
What is the traditional gold standard in diagnosing OSAS?
Polysomnography (PSG)
What physiological readings may be taken during PSG testing?
- EEG
- EOG
- Electromyogram
What is an EOG?
Electro-oculogram
What does an electromyogram monitor?
Muscle movements
How is a PSG interpreted?
Apnoea and hypoapnoea events are quoted as an apnoea//hypoapnoea index (AHI)
What is an AHI used for in assessing OSAS?
Measuring the severity of apnoea
How is AHI calculated?
Sum of apnoeas and hypoapnoeas divided by hours of sleep
What is considered mild OSAS based on AHI?
AHI = 5-14/hour
What is considered moderate OSAS based on AHI?
AHI = 15-30/hour
What is considered severe OSAS based on AHI?
AHI >30/hour
What are some other investigations that can be useful in diagnosing OSAS?
- Domiciliary diagnostic systems
- Thoracic and abdominal binders
- Nasolaryngoscopy
- Blood pressure
What is an example of a domiciliary diagnostic system used in OSAS?
Respiratory multi-channel recording
What can respiratory multi-channel recording measure?
- Snoring
- Nasal airflow
- Oximetry
- Pulse rate
What do thoracic abdominal binders measure?
Reductions in chest movements
What can nasolaryngoscopy help identify in OSAS?
Level of any obstruction
What are the differentials of OSAS?
- Fragmented sleep
- Sleep deprivation
- Depression
- Narcolepsy
- Hypothyroidism
- Drugs
- Neurological conditions
What drugs could causes OSAS like presentation?
- Sedatives
- Stimulants
- Beta blockers
- SSRI’s
What neurological conditions may present like OSAS?
- Previous encephalitis
- Previous head injury
- Parkinsonism
What is the goal of OSAS treatment?
To restore optimal breathing during the night and to relieve associated symptoms
What are the 4 main management options in OSAS?
- Behavioural interventions
- CPAP
- Pharmacological treatments
- Surgery
What behavioural/lifestyle interventions should be discussed with a patient with OSAS?
- Weight loss
- Smoking cessation
- Avoidance of alcohol, sedative and hypnotic medication in the evening
What is the gold standard of treatment for OSAS?
CPAP
What are the advantages of CPAP for OSAS?
- Highly effective symptom control
- Improve QoL
- Reduce sequelae
What are the disadvantages of CPAP?
- Can lead to claustrophobia
- Can cause rhinitis and nasal irritation
- Can disturb partner’s sleep
How does CPAP work to treat OSAS?
It acts as a pneumatic splint to maintain airway patency
How long each night should CPAP be worn?
Minimum of 4 hours
What does the efficacy of CPAP to treat OSAS depend on?
Continuous use
How good are pharmacological agents at treating OSAS?
Limited
What drug may have benefit in treating daytime sleepiness in patients with OSAS?
Modafinil
When is surgery considered for OSAS?
People in whom CPAP or oral appliances have failed or are contraindicated
What are 3 surgical options for treating OSAS?
- Suspension of hyoid bone
- Uvulopalatopharyngoplasty
- Radio-frequency ablation of tongue base
What are the potential complications of OSAS?
- Accidents due to daytime sleepiness
- Irritability
- Depression
- Cardiovascular complications
- Stroke
What should patients with excessive daytime sleepiness do to avoid serious accidents?
Stop driving until OSAS is controlled
What cardiovascular complications can occur as a result of OSAS?
- Hypertension
- Coronary artery disease
- Congestive heart failure
