Splenic contraction associated with sudden, transient hypotension and sympathoexcitation in humans

Figures

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  FIGURE 1. Cardiovascular responses before and after the head‐up tilt. (a–e) The mean absolute heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and systolic, mean arterial and diastolic blood pressures (SBP, MAP, DBP) for all participants (n = 18) before (0–60 s) and after (60–120 s) the transition from the head‐down to the head‐up position. The vertical dashed line indicates the time of transition. (f) The relative change from baseline during the period 30–60 s after the head‐up tilt (90–120 s) for all participants. Data are presented as means with SD and individual values (n = 18). Absolute baseline and trial data were compared using either two‐tailed, paired t‐test (HR, SV, CO, SBP, MAP, DBP) or related‐samples Wilcoxon's signed rank test (TPR). P‐values for each dataset are shown to the left of each bar, with asterisks above bars indicating significance. ** P < 0.01, *** P < 0.001.

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  FIGURE 2. Cardiovascular responses before, during and after the cold‐pressor test. (a–e) The mean absolute heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and systolic, mean arterial and diastolic blood pressures (SBP, MAP, DBP) for all participants (n = 18) before (0–60 s), during (60–120 s) and after (120–180 s) the cold pressure test. The vertical dashed lines indicate the start and end of the immersion period. (f) The relative change from baseline during the period 30–60 s into the immersion (90–120 s) for all participants. Data are presented as means with SD and individual values (n = 18). Absolute baseline and trial data were compared using either two‐tailed, paired t‐test (HR, SV, CO, SBP, MAP, DBP) or related‐samples Wilcoxon's signed rank test (TPR). P‐values for each dataset are shown to the left of each bar, with asterisks above bars indicating significance. ** P < 0.01, *** P < 0.001.

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  FIGURE 3. Cardiovascular responses during the thigh‐cuff manoeuvre. (a–e) The mean absolute heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and systolic, mean arterial and diastolic blood pressures (SBP, MAP, DBP) for all participants (n = 18) before (0–60 s) and after (60–120 s) the release of the thigh‐cuff pressure. The vertical dashed line indicates the time of deflation. (f) The relative change from baseline during the period 30–60 s after the thigh‐cuff deflation (90–120 s) for all participants. Data are presented as means with SD and individual values (n = 18). Absolute baseline and trial data were compared using either two‐tailed, paired t‐test (HR, SV, CO, SBP, MAP, DBP) or related‐samples Wilcoxon's signed rank test (TPR). P‐values for each dataset are shown to the left of each bar, with asterisks above bars indicating significance. ** P < 0.01, *** P < 0.001.

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  FIGURE 4. Cardiovascular responses before, during and after the apnoea test. (a–e) The mean absolute heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and systolic, mean arterial and diastolic blood pressures (SBP, MAP, DBP) for all participants (n = 18) before (0–60 s), during (60–181 s) and after (181–211 s) the apnoea. The vertical dashed lines indicate the start and end of the apnoea. Breaks in the lines reflect the fact that apnoea durations varied among the participants, and the position of the end of apnoeas in the graphs has been adjusted for each participant to match the mean duration of the apnoeas (121 s). (f) The relative change from baseline during the last 30 s of apnoea for all participants. Data are presented as means with SD and individual values (n = 18). Absolute baseline and trial data were compared using either two‐tailed, paired t‐test (HR, SV, CO, SBP, MAP, DBP) or related‐samples Wilcoxon's signed rank test (TPR). P‐values for each dataset are shown to the left of each bar, with asterisks above bars indicating significance. ** P < 0.01, *** P < 0.001.

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  FIGURE 5. Changes in splenic volume. All trials—head‐up tilt (HUT), cold‐pressor test (CPT), thigh‐cuff manoeuvre (TCM), and apnoea test (APN)—resulted in a reduction from baseline in splenic volume. Data are presented as means with SD and individual values (n = 18). Absolute baseline and trial data were compared using related‐samples Wilcoxon's signed rank test. P‐values for each dataset are shown above each bar, with asterisks above bars indicating significance. The relative changes in splenic volumes did not differ between trials (one‐way repeated measures ANOVA). * P < 0.05, ** P < 0.01, *** P < 0.001.