Adult Obstructive Sleep Apnea
- Adult obstructive sleep apnea (AOSA) is a sleep disorder
- Characterised by repeated episodes of partial or complete obstruction of the upper airway during sleep which results in pauses in breathing and/or reduced airflow.
- Most common in Male 85%
Pathophysiology (6)
1. Pharyngeal collapse
- Soft tissues at back of the throat (uvula, tonsils, soft palate) relax & collapse during sleep obstructing the air flow.
- Exacerbated by factors like Obesity which increases amount of soft tissue in upper airway, Alcohol consumption further relax the muscles of the upper airway
2. Decresaed airway patency
- Airway obstruction → negative pressure builds up in the chest
- This causes diaphragm & other muscles involved in breathing to work harder to draw in air
- → decreased airway patency making it even more difficult for air to flow through upper airway.
3. Increase in negative pressure
- Increased resistance to airflow during inhalation causes drop in air pressure in lungs→ respiratory centre in brain sense this increasing the effort of respiratory muscles to draw in more air → Negative pressure builds up within chest creating a vacuum effect leading to further collapse of soft tissues in upp airway.
4. Vicious cycle created
- Each episode leads to decrease in O₂ & Increse in CO₂ → signals brain to wake up body briefly to resume breathing often the person is unaware.
5. Anatomic narrowing; requires inspiratory pressures.
6. Abnormal neuromuscular control: Reflex activation of dilators in response to airway obstruction often falls.
CONCLUSION: Repeated episode of partial/ complete obstruction of upper airway → Cause decrease in O2 (hypoxemia) and increase in CO2 (hypercapnia) → Leads to state of asphyxia.
This vicious cycle leads to altered blood gas causing damage to cardiopulmonary system.