Abstract
The aim of the study was to assess cardiac and respiratory blood pressure (BP) and subarachnoid space (SAS) width oscillations during the resting state for slow and fast breathing and breathing against inspiratory resistance. Experiments were performed on a group of 20 healthy volunteers (8 males and 12 females; age 25.3 ± 7.9 years; BMI = 22.1 ± 3.2 kg/m2). BP and heart rate (HR) were measured using continuous finger-pulse photoplethysmography. SAS signals were recorded using an SAS monitor. Oxyhaemoglobin saturation (SaO2) and end-tidal CO2 (EtCO2) were measured using a medical monitoring system. Procedure 1 consisted of breathing spontaneously and at controlled rates of 6 breaths/minute and 6 breaths/minute with inspiratory resistance for 10 minutes. Procedure 2 consisted of breathing spontaneously and at controlled rates of 6, 12 and 18 breaths/minute for 5 minutes. Wavelet analysis with the Morlet mother wavelet was applied for delineation of BP and SAS signals cardiac and respiratory components. Slow breathing diminishes amplitude of cardiac BP and SAS oscillations. The overall increase in BP and SAS oscillations during slow breathing is driven by the respiratory component. Drop in cardiac component of BP amplitude evoked by slow-breathing may be perceived as a cardiovascular protective mechanism to avoid target organ damage. Further studies are warranted to assess long-term effects of slow breathing.
Highlights
Slow breathing practices have been practiced for thousands of years amongst Eastern cultures due to their perceived health benefits[1]
Our study has demonstrated that the overall increases in blood pressure (BP) and subarachnoid space (SAS) oscillations observed during slow breathing are strictly dependent on the respiratory component, and this phenomenon is evident when inspiratory resistance is applied (Fig. 4b)
Using integrated non-invasive techniques, we have demonstrated for the first time that slow breathing diminishes cardiac-dependent BP and cerebrospinal fluid (CSF) pulsatility
Summary
Slow breathing practices have been practiced for thousands of years amongst Eastern cultures due to their perceived health benefits[1]. Controlled slow breathing, at 6 breaths per minute, is associated with augmented BP fluctuations of respiratory origin, as compared to the BP oscillations observed during spontaneous breathing[4,8,10]. The main assumption for NIR-T/BSS technique is that translucent CSF in SAS acts as a propagation duct for infrared radiation (a technique resembling optical fibers engineering)[14,15]. This allows for measurement of the SAS width to estimate changes in CSF volume[14,15,16,17,18].
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