Effect of intermittent hypoxia on breathing stability in individuals with sleep apnea

Abstract

There is much speculation that respiratory motor long-term facilitation may have a significant impact on apnea severity in individuals with sleep apnea because this disorder is characterized by exposure to intermittent hypoxia, one stimulus known to initiate long-term facilitation. It has been suggested that activation of long-term facilitation may serve to mitigate apnea by facilitating minute ventilation and, perhaps more importantly, upper airway muscle activity. The less discussed but equally plausible situation is that exposure to intermittent hypoxia might ultimately lead to the promotion of apnea. There are at least two scenarios in which apnea might be promoted following exposure to intermittent hypoxia. In both scenarios, long-term facilitation of upper airway muscle activity is initiated but ultimately rendered ineffective because of muscle fatigue or the initiation of other forms of respiratory plasticity, more specifically progressive augmentation of the hypoxic ventilatory response. The primary goal of this chapter is to discuss whether the complex interactions of various forms of respiratory motor neuronal plasticity have a beneficial or a detrimental impact on breathing stability in individuals with sleep apnea. The overall conclusion is that exposure to intermittent hypoxia should not be considered exclusively beneficial or detrimental to breathing stability in individuals with sleep apnea. Rather, the beneficial or detrimental outcomes of exposure to intermittent hypoxia are likely dependent on a variety of circumstances and the complex interactions between various forms of respiratory motor plasticity.