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Figure 2 | BMC Physiology

Figure 2

From: Heart rate variability and short duration spaceflight: relationship to post-flight orthostatic intolerance

Figure 2

Data from an astronaut who could complete the landing day ten-minute stand test (finisher). Pre-flight (top figure), landing day (middle figure) and post-flight (bottom figure) RR-interval time series are presented with the onset of standing marked as time 0-minutes. Supine data are on the left (negative times) and stand data on the right (positive times). The gap between -9 and -2 minutes represents the 7-minute carbon-monoxide test for blood volume measurements [11]. Subjects maintained a fixed breathing rate of 15 breaths per minute (0.25 Hz) during the five minutes prior to the carbon monoxide test and during the first five minutes of the stand test. The harmonic spectral power (PHARM) generated from coarse graining spectral analysis of RR-interval in each of the data segments are presented below the supine and above the stand RR-interval data. For comparison over test conditions and with the example non-finisher astronaut (Figure 1), at each frequency harmonic spectral power was normalized with the pre-flight supine total power (PTOT) and are presented in normalized units (n.u.: PHARM / PTOT).

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