NIV during Sleep

Question 1

Obstructive sleep apnea

Answer 1

Complete obstruction of the airway - “event” - causes no airflow. >5/hr
Causes oxygen saturation swings and hypoxia
Increase respiratory effort (sympathetic NS) which also increases BP and HR
Disrupted sleep

More common in men, high BMI, age, ethnic groups
Causes headaches, fatigue, depression, hypertension, stroke

Question 2

Central sleep apnea

Answer 2

Pattern of increasing then decreasing work by respiratory muscles and then a period of no effort

Seen in congestive HF, stroke, opioid use and idiopathic

Rx - oxygen therapy (doesn’t fix problem), CPAP (pressure to heart to improve ejection fracture but takes weeks), BiLevel therapy (provides assistance when their respiration reduced

Question 3

Nocturnal hypo ventilation syndrome

Answer 3

Hypoventilation sustained fall in SpO2 >8mmHg, reduced central drive
Reduced chest wall mvmt and airflow
Postural mm hypotonia (upper airway resistance, dependence on diaphragm)
Reduced chemo responsiveness to CO2 and O2
Common is obesity, lung disease, chest wall restriction, neuromuscular disorders

Question 4

Describe how nocturnal respiratory failure can progress to daytime hypercapnia

Answer 4

Sleep fragmentation from abnormal breathing events alters central respiratory control and depresses arousal. Sensitivity of the ventilatory control system changes, allowing higher levels of PaCO2 to be tolerated without respiratory changes, even during wakefulness.

Question 5

Outline Mx strategies for sleep disordered breathing

Answer 5

NIV!!!! - BiLevel ventilation
CPAP (if upper airway obstruction is the primary factor)
Mechanically assisted cough
oxygen therapy is not appropriate (CO2 build up)

Question 6

Discuss the effects of sleep on respiration in the normal subject

Answer 6

Inspiratory drive decreases
Hypoventilation
PaO2 drops to 96-97%
PaCO2 increases 6-8mmHg
Hypotonia - increased airway resistance
Chemoreceptors less sensitive

All of these particularly during REM phase of sleep