Near-infrared spectroscopy muscle oximetry of patients with postural orthostatic tachycardia syndrome

Figures

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  Fig. 1.. (a) Custom-built NIRS Oximetry system consists of a control box and a probe connected to a laptop through a DAQ box. (b) The probe head geometry consists of a triple wavelength LED and two detectors, arranged in a line with a 2 cm source-detector separation.

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  Fig. 2.. (a) The photon propagation in Monte Carlo simulation for 2 cm source to detector separation. (b) The average effective photon path for the simulation.

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  Fig. 3.. The head-up tilt table (HUT) protocol; NIRS oximetry probe and Covidien probe are attached to the gastrocnemius muscle. The subjects were monitored at 0°, 70° and back to 0° angles of the tilt table for 10 mins at baseline, for 30 mins at a 70° tilt and for 10 mins at recovery.

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  Fig. 4.. Regional ΔOxy correlation graph between Covidien probe and NIRS oximetry probe results in POTS and healthy subjects during the tilt at 70°. R2 on the graphs closer to 1.0 show the better fit of the regression line.

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  Fig. 5.. Data comparison between healthy subjects and POTS patients depicts changes in average HbO2 and Hb concentrations on changing the position of the tilt table at 0°, 70° and 0° for 10 mins, 30 mins and 10 mins, respectively. POTS subjects displayed a significantly higher increase in Hb, while the change in HbO2 was statistically similar in both groups. The p-value (p < 0:01 significant difference) was determined between the rising and dropping slopes of both the groups for HbO2 and Hb.

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  Fig. 6.. Statistical analysis of healthy subjects and POTS patients. The two groups were compared in average HbO2, average Hb, ΔOxy and ΔBV during the 70° tilt. Referring p-value < 0:01 shows that there was a significant difference between healthy and POTS subjects (n = 6 per group).