A method for measuring and modeling the physiological traits causing obstructive sleep apnea

Abstract

There is not a clinically available technique for measuring the physiological traits causing obstructive sleep apnea (OSA). Therefore, it is often difficult to determine why an individual has OSA or to what extent the various traits contribute to the development of OSA. In this study, we present a noninvasive method for measuring four important physiological traits causing OSA: 1) pharyngeal anatomy/collapsibility, 2) ventilatory control system gain (loop gain), 3) the ability of the upper airway to dilate/stiffen in response to an increase in ventilatory drive, and 4) arousal threshold. These variables are measured using a single maneuver in which continuous positive airway pressure (CPAP) is dropped from an optimum to various suboptimum pressures for 3- to 5-min intervals during sleep. Each individual's set of traits is entered into a physiological model of OSA that graphically illustrates the relative importance of each trait in that individual. Results from 14 subjects (10 with OSA) are described. Repeatability measurements from separate nights are also presented for four subjects. The measurements and model illustrate the multifactorial nature of OSA pathogenesis and how, in some individuals, small adjustments of one or another trait (which might be achievable with non-CPAP agents) could potentially treat OSA. This technique could conceivably be used clinically to define a patient's physiology and guide therapy based on the traits.

Genetic Associations with Obstructive Sleep Apnea Traits in Hispanic/Latino Americans

“…Mean sleep Sp O 2 correlates with AHI while also providing information on a key physiologic stress associated with OSA. Second, the average respiratory disturbance (apnea or hypopnea) length, a measure reflecting the respiratory arousal threshold, which has been postulated to be a phenotype informative for targeted interventions addressing respiratory stability (10).…”

“…Wellman and colleagues have proposed that four physiologic traits affect OSA susceptibility, including the respiratory arousal threshold, defined as the intensity of respiratory stimuli (e.g., negative pharyngeal pressure and increase of carbon dioxide concentration) required to invoke awakening (10,48). As a surrogate for respiratory arousability, we analyzed average apnea and hypopnea event duration length, with shorter duration events indicating greater arousability (49).…”

Potential protective mechanism of arousal in obstructive sleep apnea

“…These traits include a low arousal threshold (wake easily from sleep), upper airway gain (how effectively activation of upper airway dilator muscles improves ventilation), loop gain (stability of the negative feedback chemoreflex control system) and upper airway collapsibility (anatomical predisposition to passive airway collapse) (1). While deficits in these traits and how they interact varies between individuals, generally mechanisms that increase activation of upper airway dilator muscles are considered to help protect the airway from collapse.…”

Clinical Use of Loop Gain Measures to Determine Continuous Positive Airway Pressure Efficacy in Patients with Complex Sleep Apnea. A Pilot Study

“…Obstructive sleep apnea (OSA), a disorder characterized by collapse of the upper airway during sleep, is caused by a combination of loss of upper airway muscle tone, collapsible pharyngeal anatomy, and increased loop gain of the ventilatory control system (more unstable) (1,2). By contrast, central sleep apnea (CSA) is characterized by a cessation of breathing that does not require upper airway collapse and is a driven primarily by increased respiratory system loop gain (3,4).…”