RESP 207 OSA Flashcards
What is the definition of obstructive sleep apnoea?
Intermittent and repeated upper airway collapse during sleep resulting in irregular breathing at night and excessive sleepiness during the day
How do you define complete apnoea?
10 seconds + of paused breathing
How do you define hypopnoea?
10 seconds where ventilation decreased by 50%
Name some risk factors for OSA?
Obesity Middle aged Male Smoking Sedatives / Alcohol Jaw morphology Hypothyroidism
What are the clinical features of OSA?
Excessive daytime sleepiness Decreased concentration Snoring unrefreshing sleep Withness apnoea
What is the pathophysiology behind OSA?
Oropharynx colla[ses due to decreased pharyngeal muscle tone so the tongue/posterior palate drop back onto the posterior pharyngeal wall occluding the airway
What stimulates arousal during sleep in OSA?
The rising PaCO2
What is the main treatment for OSA?
CPAP
Where are the respiratory centres in the central control of ventilation?
medulla oblongata
What are the 2 groups of UMN’s that control respiration? What is their function?
Dorsal respiratory group - Initiates respiration
Ventral respiratory group - mostly expiration
What do the UMN groups that control respiration respond to?
Input from the pons and the cortex
afferents from chemoreceptors peripherally and centrally that detect changes in blood and CSF pCO2 and pO2
Which of pCO2 or pO2 will make the most difference to ventilation rate?
pCO2 but after ~100mmHg pO2 becomes a driving factor
A change in either will make the ventilatory rate more sensitive to the other
What does the pontine respiratory group do?
Fine tune the respiratory rhythm
What is the pathway for voluntary control of breathing?
Cerebral cortex –> pyramidal tracts –> corticospinal tracts
What are the 3 different airway reflexes for modifying the respiratory rhythm?
Irritant receptors
Pulmonary stretch receptors
J-receptors
What do irritant receptors in the airway respond to and what do they result in?
Noxious gases detected in airway –> vagus nerve = bronchoconstriction
Irritants detected in nose and upper airway –> vagus = cough/sneeze
What is the Hering-Bruer reflex?
A reflex to prevent over-inflation of the lungs by detecting excessive inhalation by pulmonary stretch receptors and sending signals via the vagus nerve to stimulate expiration
What are J receptors?
Receptors that detect increased fluid in the lung - engorged capilliaries which triggers receptors – vagus to cause dyspnoea (in heart failure)
Describe Type 1 respiratory failure?
Acute hypoxaemic respiratory failure
Low PaO2 and N/Low PaCO2 due to V/Q mismatch
Occurs due to under-ventilated alveoli (pulmonary oedema, pneumonia or acute asthma) or R-L shunt
What are the common causes of type 1 respiratory failure?
Cardiogenic pulmonary oedema
Pneumonia
Acute lung injury
Lung fibrosis
Describe type 2 respiratory failure?
Occurs when alveolar ventilation is insufficient to excrete the volume of carbon dioxide being produced by tissue metabolism
Due to: Reduced ventilatory effort/ inability to overcome a resistance to ventilation and failure to compensate for increased dead space or CO2 production
Low PaO2 and Normal/High PaCO2?
What the common causes of type 2 respiratory failure?
COPD
Chest wall deformities
Respiratory muscle weakness (GBS)
Depression of respiratory centre (overdose)
What is the likely blood gas in type 1 respiratory failure?
decreased pO2
Normal/low pCO2
normal/high pH (alkalosis)
normal/low bicarb
= respiratory alkalosis
What is the likely blood gas in type 2 respiratory failure?
decreased pO2
increased pCO2
low/normal pH
high/normal bicarb
respiratory acidosis
