Sleep Flashcards
- Contrast the reparatory changes that occur during NREM with those that occur in REM sleep in healthy subjects.
decrease in muscle activity as a result of withdrawal of the “wakefulness stimulus” is more prominent in REM sleep than non-REM sleep and most prominent during phasic REM sleep
respiratory chemoreceptors become less sensitive to their stimuli, especially during REM sleep (higher CO2 level needed to stimulate ventilation)
increased circulatory time is seen in CHF, causing overshot of response to stimulus
- Understand the concepts of loop gain and apneic threshold as they contribute to Cheyne-Stokes breathing.
(most common in patients with CHF, renal or neurological disease or periodic breathing of altitude)
loop gain is the amount of response of a system in proportion to the disturbance in the system, high loop gain experienced with C-S breathing
apneic threshold is the level of pCO2 that stimulates breathing, the role of CO2 in maintaining rhythmic breathing during sleep is indicated by a very sensitive apnea threshold for PCO2; ventilatory responsiveness to pCO is decreased in sleep
C-S breathing requires manifestation of elevated apneic threshold for CO2 and a high loop gain
high loop gain produces higher than normal ventilation to end the apnea and drive CO2 below apneic threshold which can lead to another apnea and perpetuate a cycle
- Describe the factors implicate in obstructive sleep apnea.
absence of airflow in the presence of progressively increasing inspiratory efforts against an occluded airway, obstruction can be at the level of the palate or the base of the tongue
reduction in UAW size is related to obesity, bulky upper airway structures and small facial bone structure (short mandible)
occlusion occurs when the force of suction int eh UAW produces sufficient sub-atmospheric pressure in the supraglotic space to overcome the dilating force of the UAW muscles; airway potency is associated with arousal and re-instatement of wakefulness stimulus
- Differentiate the mechanisms of central apnea and obstructive apnea.
central apnea occurs when absent air flow is associated with no inspiratory effort
obstructive apnea occurs when absent flow is associated with inspiratory effort
note the physiologic impact of hypopnea is essentially the same as apnea
- Describe the treatments for sleep apnea.
nasal continuous positive airway pressure (CPAP)
weight loss (fat deposits in the larynx
avoiding supine position
respiratory stimulates and oxygen for central apneas
tracheotomy as a last resort in patients with sever obstructive apnea and cardiopulmonary sequelae
- Explain the sensation of dyspnea as it relates to disease states.
discomfort during breathing that occurs at levels of activity that are unexpected; dyspnea is a sensation, resulting form the stimulation of sensory receptors activated by the act of breathing
inappropriateness between motor output, tension and volume displacement is detected in the sensory integration center in the CNS; can lead to changes in breathing pattern and “central respiratory muscle fatigue
Describe how sleep state affects ventilation and breathing patterns in healthy subjects.
changes in central control:: firing pattern form inspiration to expiration, desynchronization of firing during respiration and reduction in activity of some neurons to upper airway dilators
most significant changes: reduction in inputs of respiratory motoneurons and respiratory muscle activity as a result of withdrawal of wakefulness stimulus (UAW muscles activity most reduced)
When are apneas most likely to occur?
during the transition between wake and sleep as well as the more likely during REM sleep where body is most insensitive to stimuli and inspiratory skeletal muscles are inactive
- What are some of the consequences of obstructive sleep apnea?
consequences include oxygen desaturations and sleep fragmentation, increased sympathetic activity, vascular oxidative stress, altered endothelial function, increased coagulation, inflammation, and metabolic dysregulation; can result in in worsening CV disease ie. HTN, CHF, arrhythmias, ischemia and stroke, day time sleepiness, fatigue (increased accidents and decreased quality of life)
