Obstructive Sleep Apnoea

OVERVIEW

Obstructive sleep apnea (OSA) syndrome is defined by the following features:

• cessation of airflow from nose/mouth for >10s
• resulting in intermittent respiratory arrests with hypoxaemia
• interruption of REM sleep
• >5 episodes/h

PATHOPHYSIOLOGY

• patency of the oropharyngeal airway is due to activity of paired sets of upper airway muscles
• during normal respiratory activity muscles (e.g. soft palate, pharyngeal walls, tongue) prevent otherwise floppy structures from being sucked into the airway
• obstruction during sleep may be due to a combination of factors:

1. reduced airway size
   • enlarged tonsils/adenoids, macroglossia, myxoedema, acromegaly, malignancy, structurally small airway
2. decreased neuromuscular tone
   • reduced tone occurs in REM sleep, particularly in postural muscles of the pharynx and palate
3. neuromuscular incoordination
   • the normal coordination of increased upper airway tone with inspiration is lost

RISK FACTORS

Children

• tonsillar hypertrophy
• congenital syndromes
• hypotonia

Adults

• smoking
• ETOH
• CORD
• airway pathology
• CVA
• acromegaly
• DM
• CHF
• cushings
• polio

HISTORY (STOPBANG)

• Snoring (ask the patient’s partner!)
• Tired
• Obstruction (apnoea)
• Pressure (HTN)
• BMI (increased)
• Age (middle aged)
• Neck circumference
• Gender (males > females)

Symptoms of pulmonary hypertension and right heart failure

• e.g SOBOE, ankle swelling, chest pain, tightness

PMH

OSA is a multi-system disease

• CNS: decreased cognition, decreased mood, CVA, accidents, headaches, somnolence, glaucoma
• CVS: HT, IHD, PHT, right heart failure, AF
• RESP: hypoxaemia, hypercapnia, cor pulmonale, decreased FRC
• ENDO: DM, impotence
• HAEM: polycythaemia

Meds:

• inhalers, medications for above problems

SH:

• occupation – sedentary occupation
• diet – high energy consumption
• exercise – regular exercise

EXAMINATION

BMI >30

Airway

• large tongue
• full pharyngeal, palate, and tonsillar fat pads
• stridor on breathing while conscious and upright (collapsing of pharyngeal tissue)
• Mallampati 3-4
• neck circumference >40cm
• limited atlanto-occipital movement
• large amount of breast tissue

Breathing

• decreased SpO2 on RA
• increased RR
• cyanosis

Circulation

• hypertension, tachycardia
• signs of heart failure: elevated JVP, right ventricular heave, apex displaced, murmurs, ankle swelling, enlarged liver

INVESTIGATIONS

• FBC: polycythaemia
• U+E: renal impairment
• ECG: right heart strain
• ABG: PO2 on RA
• ECHO: PHT, right heart function
• Sleep study/Polysomnograph
  — SpO2, nasal airflow, EEG, EMG, respiratory and abdominal muscle movement, ECG
  — apnoea index = <5/hr mild, >30/hr severe

MANAGEMENT

• CPAP (bring in from home while an inpatient)
• continue normal respiratory medications
• RHF treatment
• life style modification (weight loss, stop smoking, decrease ET-OH)
• surgical options
  — weight reduction
  — adenoidectomy, ect
• avoid premedication (sedation)
• plan for difficult mask ventilation +/- intubation

References and Links

• Park JG, Ramar K, Olson EJ. Updates on definition, consequences, andmanagement of obstructive sleep apnea. Mayo Clin Proc. 2011 Jun;86(6):549-54;quiz 554-5. PMC3104914.
• Patil SP, Schneider H, Schwartz AR, Smith PL. Adult obstructive sleep apnea:pathophysiology and diagnosis. Chest. 2007 Jul;132(1):325-37. PMC2813513.