Efficacy of Marker-Based Motion Capture for Respiratory Cycle Measurement: A Comparison with Spirometry.

Respiratory rate monitoring is fundamental in clinical settings, and the accuracy of measurement methods is critical. This study aimed to develop and validate methods for assessing respiratory rate and the duration leof respiratory cycle phases in different body positions using optoelectronic plethysmography (OEP) based on a motion capture video system. Two analysis methods, the summation method and the triangle method were developed. The study focused on determining the optimal number of markers while achieving accuracy in respiratory parameter measurements. The results showed that most analysis methods showed a difference of ≤0.5 breaths per minute, with R2 ≥ 0.94 (p < 0.001) compared to spirometry. The best OEP methods for respiratory rate were the abdominal triangles and the sum of abdominal markers in all body positions. The study explored inspiratory and expiratory durations. The research found that 5-9 markers were sufficient to accurately determine respiratory time components in all body positions, reducing the marker requirements compared to previous studies. This interchangeability of OEP methods with standard spirometry demonstrates the potential of non-invasive methods for the simultaneous assessment of body segment movements, center of pressure dynamics, and respiratory movements. Future research is required to improve the clinical applicability of these methods.

Transcutaneous Spinal Cord Stimulation Attenuates Blood Pressure Drops in Orthostasis.

Orthostatic hypotension is a complex medical problem with various underlying pathogenic mechanisms and limited modalities for its correction. Since transcutaneous spinal cord stimulation (t-SCS) leads to immediate blood pressure (BP) elevation in a supine position, we suggested that t-SCS may attenuate blood pressure drops in orthostasis. We aimed to evaluate the hemodynamic effects of t-SCS during tilt testing in a feasibility study in three patients with documented orthostatic hypotension. Four sessions on two different days of tilt testing on and off t-SCS were performed on each patient. While tilting with t-SCS off showed typical significant BP drops in every patient, active t-SCS resulted in systemic vascular resistance (SVR) elevation in all patients and significantly higher values of systolic and diastolic BP in two patients. T-SCS requires further investigation on a larger patient population. However, our preliminary results demonstrate its ability for SVR and BP elevation in subjects with severe orthostatic hypotension.

Acute Cardiovascular Effects of Non-Invasive Electrical Spinal Cord Stimulation: Results from a Pilot Study in Humans.

We aimed to determine if non-invasive electrical spinal cord stimulation (NIE-SCS) is associated with acute changes in systemic and pulmonary hemodynamics and cardiac electrophysiology at rest. Nine subjects without structural heart disease referred for catheter ablation of cardiac arrhythmia were included. NIE-SCS was performed in each patient at vertebral levels T1, T7, and T11. Higher systolic BP (BPs) was detected during T1 NIE-SCS as compared with baseline (147.9 ± 22.5 vs 135.4 ± 17.4 mmHg; P = 0.02). Atrioventricular nodal effective refractory period (AVN ERP) was shorter during stimulation at T1 and T7, when compared with baseline values (baseline 303.3 ± 15.0 vs 272.0 ± 19.2 for T1 vs 278.0 ± 8.3 ms for T7; P < 0.05). NIE-SCS at the T1 level is associated with an elevation of BPs. NIE-SCS at the T1 and T7 levels shortens AVN ERP. Further studies are needed for the evaluation of chronic effects.

Effects of paired transcutaneous electrical stimulation delivered at single and dual sites over lumbosacral spinal cord.

It was demonstrated previously that transcutaneous electrical stimulation of multiple sites over the spinal cord is more effective in inducing robust locomotor behavior as compared to the stimulation of single sites alone in both animal and human models. To explore the effects and mechanisms of interactions during multi-site spinal cord stimulation we delivered transcutaneous electrical stimulation to the single or dual locations over the spinal cord corresponding to approximately L2 and S1 segments. Spinally evoked motor potentials in the leg muscles were investigated using single and paired pulses of 1ms duration with conditioning-test intervals (CTIs) of 5 and 50ms. We observed considerable post-stimulation modulatory effects which depended on CTIs, as well as on whether the paired stimuli were delivered at a single or dual locations, the rostro-caudal relation between the conditioning and test stimuli, and on the muscle studied. At CTI-5, the paired stimulation delivered at single locations (L2 or S1) provided strong inhibitory effects, evidenced by the attenuation of the compound responses as compared with responses from either single site. In contrast, during L2-S1 paradigm, the compound responses were potentiated. At CTI-50, the magnitude of inhibition did not differ among paired stimulation paradigms. Our results suggest that electrical stimuli delivered to dual sites over the lumbosacral enlargement in rostral-to-caudal order, may recruit different populations of motor neurons initially through projecting sensory and intraspinal connections and then directly, resulting in potentiation of the compound spinally evoked motor potentials. The interactive and synergistic effects indicate multi-segmental convergence of descending and ascending influences on the neuronal circuitries during electrical spinal cord stimulation.