PurposeThe present study compared the effects of mandibular advancement therapy (MAD) with continuous positive airway pressure therapy (CPAP) on daytime cardiac autonomic modulation in a wide range of obstructive sleep apnea (OSA) patients under controlled conditions in a randomized, two-period crossover trial.MethodsForty OSA patients underwent treatment with MAD and with CPAP for 12 weeks each. At baseline and after each treatment period, patients were assessed by polysomnography as well as by a daytime cardiac autonomic function test that measured heart rate variability (HRV), continuous blood pressure (BP), and baroreceptor sensitivity (BRS) under conditions of spontaneous breathing, with breathing at 6, 12, and 15/min.ResultsBoth CPAP and MAD therapy substantially eliminated apneas and hypopneas. CPAP had a greater effect. During daytime with all four conditions of controlled breathing, three-minute mean values of continuous diastolic BP were significantly reduced for both MAD and CPAP therapy. At the same time, selective increases due to therapy with MAD were found for HRV high frequency (HF) values. No changes were observed for BRS in either therapy mode.ConclusionsThese findings indicate that both MAD and CPAP result in similar beneficial changes in cardiac autonomic function during daytime, especially in blood pressure. CPAP is more effective than MAD in eliminating respiratory events.
Cold passover and heated humidifiers are employed for the prevention of side-effects associated with continuous positive airway pressure (CPAP) treatment. However, to date, it has not been possible to separately measure the humidity of inspired and expired air. The aim of this study was to compare the relative humidity of the inspired air and the water loss during respiration between cold passover and heated humidifiers under CPAP.Humidity and temperature were determined separately for the respiratory phases, without humidification, with cold passover and heated humidifiers in 10 healthy subjects. Humidity was measured with a capacitive hygrometer, temperature with a "Type K" thermosensor, and impedance of the total respiratory system with impulse oscillometry.The The use of humidifiers is recommended for the treatment of local side-effects associated with nasal continuous positive airway pressure (nCPAP) therapy to increase the humidity and temperature of the respired air [1][2][3][4]. To date, however, only humidity data averaged over a lengthy period of time have been reported [5,6]. Humidifiers are thought to exert an effect by changing the inspired air. Separate measurement of humidity during inspiration and expiration appears to be particularly useful as, owing to the high expiratory humidity, averaging of humidity figures over lengthy periods cannot completely reveal the effect of humidification on inspired air. Therefore, the present authors studied the influence of humidification under continuous positive airway pressure (CPAP) using sensors with a small dead time, making it possible to determine the rapid changes in humidity in the alternation of inspiration and expiration. The authors aimed to compare the relative humidity (Hrel) of the inspired air between cold passover and heated humidifiers, and to measure the water loss of respiration under CPAP treatment. A secondary aim was to evaluate the impedance (Z) of the total respiratory system under the various humidification systems. Methods SubjectsThe study included 10 healthy subjects (six males and four females, mean¡SD age 28.8¡10 yrs, body mass index (BMI) 23.4¡2.9 kg?m -2 , no airway disease, rhinitis, nasal surgery, upper airways infections over the previous 4 weeks). Before the experiments, lung function (forced vital capacity (FVC) 109.9¡25.8% predicted, forced expiratory volume in one second (FEV1) 117.9¡30.9% pred, total lung capacity (TLC) 108.2¡17.4% pred) and nasal Z were determined (body plethysmography was performed using Master Lab1 and impulse oscillometry using IOS Rhino1, both from Jaeger, Hö chberg, Germany). The total Z of the nose was calculated from separate measurements in both nares (Z 5 Hz 4.7¡2.4 cmH 2 O?L?s -1 , resistance (R) 4.0¡2.0, reactance (X) -2.0¡2.0) [7]. DesignThe subjects were examined in randomised order in the supine position, at a CPAP pressure of 10 cmH 2 O
In both healthy volunteers and anaesthetized patients, HV resulted in comparable and reversible changes of established HRV parameters. These changes might be relevant enough to bias HRV-based analgesia and anaesthesia monitoring and could result in a clinically relevant misinterpretation of HRV parameters as indicators of anaesthetic depth during HV.
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