obstructive-sleep-apnea-pathogenesis-and-clinical-findings

obstructive-sleep-apnea-pathogenesis-and-clinical-findings

Obstructive Sleep Apnea: Pathogenesis and clinical findings
Authors: Ciara Hanly Austin Laing Alexander Arnold Reviewers: Steven Liu Amogh Agrawal Naushad Hirani* Yan Yu* *MD at time of publication
Neuromuscular Factors: Loss of wakefulness drive to breathe associated with sleep onset
↓ Upper airway neuromuscular activityà↓ upper airway caliber, ↑ upper airway resistance, ↑ upper airway collapsibility during sleep
Structural Factors: Obesity, tonsillar or adenoid hypertrophy, macroglossia, ↑ neck circumference, craniofacial abnormalities
Excess pressure on upper airway, or deformity to that area, ↑ risk of upper airway collapse
Vascular Factors: Rostral fluid shift with recumbent sleep
Upper airway obstruction due to increased volume and pressure of surrounding tissues
Polysomnography
Absence of airflow but persistent ventilatory effort
Hypopnea or Apnea
Paradoxical breathing Chest wall draws in and abdomen expands during inspiration
Ventilatory effort persists against closed airway
No air entry due to collapsed upper airway
↑ Negative intrathoracic pressure
↑ Venous return to right atrium
Stretching of right atrial myocardium à secretion of atrial natriuretic peptide (ANP)
ANP inhibits epithelial Na+ channels (ENaC) in the collecting ducts of the kidney from reabsorbing Na+ à Na+ excretion
↑ Na+ excretionà↑ water excretion
Nocturia
Complete or partial upper
airway obstruction during sleep
↑ PCO2 & ̄ PO2
in the lungsà ̄ diffusion gradient of CO2 & O2 between lungs & arteries
↑ PaCO2,, ̄ PaO2
Respiratory acidosis (↑ [H+] in blood)àactivation of vascular endothelial voltage gated K+ channels
Cerebral blood vessel dilation to provide adequate O2 to brain
Morning Headaches
Activation of central (medulla oblongata) & peripheral (carotid body) chemoreceptors
↑ Respiratory drive à ↑ activation of respiratory muscles (ventilatory effort )
Transient arousal from sleep
↑ sympathetic nervous system activityà arterial vasoconstriction
↑ systemic vascular resistance
Systemic Hypertension
↑ intraluminal pressure within blood vesselsàadaptive vascular endothelial and smooth muscle changes
Artery walls thicken, harden and lose elasticityà ̄ perfusion to end organs (such as the brain)
Ischemic stroke
Hypoxia during the day and night
↑ pulmonary vascular resistance
Pulmonary Hypertension
Right heart pumps against higher pulmonary pressure àcardiomyocytes undergo concentric hypertrophy over time
Cor Pulmonale
(Right heart failure due to pulmonary hypertension, separate from left heart failure)
Respiratory muscles overcome upper airway obstructionà airway patency restored
Sleep fragmentation
̄ Daytime cognitive performance and attentiveness
↑ Risk of motor vehicle accidents
Daytime Sleepiness
Eg. Epworth Sleepiness Scale >10
Abbreviations:
PCO2: partial pressure of carbon dioxide PO2: partial pressure of oxygen PaCO2: partial pressure of carbon dioxide in arteries PaO2: partial pressure of oxygen in arteries
Ventilatory response overcompensatesà breathe out more CO2 than is required for homeostasisà ̄ PaCO2
̄ respiratory driveà ̄ ventilatory effort
Resuscitative Gasping
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published August 19, 2013, updated Jan 31, 2022 on www.thecalgaryguide.com