As sleep related breathing disorders remain a major public health concern a greater understanding of the pathogenesis is required to develop and improve therapeutic options in the late 1970s it became known that ventilation during non rem sleep was critically dependent upon p co 2 levels in the early 1980s loop gain an engineering term used to define the sensitivity of a variable. High loop gain promote s recurrent apnea as the response to.
The presence of sleep reduces controller gain relative to wakefulness and more importantly upper airway tone particularly in rapid eye movement sleep rem see fig.
What is loop gain sleep apnea. Unstable ventilatory chemoreflex control quantified as loop gain is recognized as one of four key pathophysiological traits that contribute to cause obstructive sleep apnea osa. Loop gain in sleep apnea what is loop gain. Loop gain measured noninvasively from polysomnography can be influenced by respiratory event scoring in obstructive sleep apnea osa according to study results published in the annals of the american thoracic society.
The factor by which the existing loop gain must be increased to produce instability is known in control parlance as the gain margin. Novel treatments aimed at reducing loop gain are being investigated with the intention that future osa treatment may be tailored to the individual s specific cause of apnea. Arguably the strongest determinant of osa is a hypersensitive ventilatory control system or elevated loop gain during sleep.
1 this condition is in contrast to obstructive sleep apnea osa in which ongoing respiratory effort is present during respiratory events. Loop gain and sleep disordered breathing. The init ial disturba nce is ove rcompensated while a low loop.
Ventilatory instability is the mechanism behind csb csa high altitude periodic breathing and probably primary central sleep apnea ref3 as with any system that is regulated by feedback loops. Methods for quantifying loop gain in osa using polysomnography have been developed that predict favorable responses to upper airway surgery. Lg is a measure of ventilatory control stability.
2 5 although these definitions are quite distinct in reality considerable overlap is present between osa and csa from the standpoint of. Central sleep apnea csa is defined by the cessation of air flow without respiratory effort. Linear control theory states that the loop gain must be increased to a value of unity before instability can occur 4 6.
The higher the loop gain the potentially more unstable the respiratory control system becomes. We compared the effect of oxygen on the apnea hypopnea index ahi in six obstructive sleep apnea patients with a relatively high loop gain lg and six with a low lg. However these methods are.
