The present study aims to document and assess changes in single parameters of pulse wave analysis (ASI single parameters) as well as to evaluate ASI cardiovascular risk assessment before initiation of CPAP therapy and after 6 months of CPAP therapy in patients with obstructive sleep apnea.
Obstructive sleep apnea (OSA) is characterized by repeated occurrence of apneas or reduced inspiratory air flow due to obstructions of the upper airways (hypopneas). These recurring events are accompanied by intermittent hypoxemia and sympathetic activation, leading to hemodynamic oscillations including relevant variations of pulse wave and blood pressure. Thus, OSA is associated with cardiovascular diseases and was identified as an independent risk factor for hypertension. Direct effects of obstructive respiratory events (obstructive apneas and hypopneas) include changes of the peripheral pulse wave. The latter can easily be measured by finger plethysmography, e.g. by using established pulse oximeters. Certain pulse wave characteristics and their reaction towards obstructive respiratory events may provide information on cardiovascular function and thereby help in individual cardiovascular risk assessment. Recently, Grote et al. published a concept for cardiovascular risk assessment based on pulse oximetry and pulse wave analysis ("ASI" - Grote et al. 2011, CHEST). The algorithm described herein is able to differentiate between high and low risk patients according to ESH/ESC risk classification (high risk = 4 and 5, low risk 1-3). To that end, oxygen saturation as measured by pulse oximetry, reductions in pulse wave amplitude, pulse rate accelerations, pulse propagation time and cardiorespiratory coupling are taken into account to calculate a quantitative total risk. A successful OSA therapy applying positive airway pressure (e.g. CPAP) normalizes sleep-related breathing disturbances and thus counterbalances hemodynamic oscillations. This presumably results in reduced cardiovascular risk and should be detectable by measurable changes in pulse wave. This study aims to evaluate these effects by analyzing the single pulse wave parameters, which are part of the ASI algorithm. At the same time, established risk factors as well as the objective therapy outcome will be documented from the established sleep medicine viewpoint.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
314
Bethanien Hospital
Solingen, Germany
Change in pulse wave attenuation index
The pulse wave attenuation index represents the number of decreases of the pulse wave amplitude \>10% and \<30% compared with baseline (a moving median value of 20 samples surrounding the observed sample). This number is given as attenuations per hour. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
Time frame: 6 months
Change in mean pulse propagation time
The pulse propagation time represents the time interval between the systolic and dicrotic notch of the pulse wave form. The mean pulse propagation time of a complete recording is documented. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
Time frame: 6 months
Change in mean respiration-related pulse oscillation
The respiration-related pulse oscillation is calculated by measuring the breathing-associated oscillation (respiratory sinus arrhythmia in the frequency band between 0.15 and 0.4 Hz) from the pulse rate signal in the time domain. The mean respiration-related pulse oscillation value of a complete recording is documented. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
Time frame: 6 months
Change in pulse rate acceleration index
The pulse rate acceleration index represents the number of pulse rate increases ≥10% from baseline (a moving median value of 20 samples surrounding the observed sample). This number is given as increases per hour. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
Time frame: 6 months
Change in hypoxia index
The hypoxia index represents the number of oxygen desaturation events per hour. A desaturation event is defined as a ≥2% drop of saturation of each sample compared with a 90 seconds time window of the upcoming SpO2 signal. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
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Time frame: 6 months
Change in ASI cardiovascular risk score
The ASI algorithm described by Grote et al. (2011) combines several single parameters from pulse wave analysis to calculate an overall cardiovascular risk score. The difference from baseline (without therapy) to 6 months (on CPAP therapy) is calculated.
Time frame: 6 months