Features  |   July 2017
Interrelationships Between Anesthesia, Sleep and Breathing
Article Information
Respiratory System / Features
Features   |   July 2017
Interrelationships Between Anesthesia, Sleep and Breathing
ASA Monitor 07 2017, Vol.81, 20-22.
ASA Monitor 07 2017, Vol.81, 20-22.
Anesthesia and sleep have much in common, particularly where breathing is concerned. This relationship is based on the similarities in physiological changes that occur with transition from consciousness to unconsciousness in each state. Wakefulness stimulates breathing through non-specific excitatory activity mediated through the ascending arousal system.1  Recent evidence suggests that the parabrachial complex, a component of this system, has key roles in both the generation of wakefulness and in the patterning of breathing during it.2  This activity diminishes with loss of consciousness, whether at induction of anesthesia or at sleep onset.
The neurophysiological pathways involved in transition from wakefulness to sleep are activated by anesthetic drugs and so are deeply implicated in the mechanisms of anesthesia.3  Given this, it is perhaps not surprising that similar physiological changes occur with loss of consciousness in both states. Volition is lost and there is a decrease in ventilatory drive,4,5  skeletal muscle activation,6 -8  reflex gain7,9  and end-expiratory lung volume.10,11  Both the upper-airway (UAW) and respiratory muscles are affected. Decreased activation of the UAW muscles results in narrowing and increased collapsibility of the pharynx. Decreased activation of the respiratory muscles results in reduced ventilatory effort. Furthermore, loss of activation of muscles of the chest wall is associated with a decrease in end-expiratory lung volume. This has its own destabilizing effect on the UAW, as it is associated with loss of longitudinal traction on it with a resulting increase in its collapsibility.12 
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