Haemodynamic responses to head‐up tilt versus lower‐body negative pressure in type 1 diabetes

Figures

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  FIGURE 1. Schematic representation of the experimental protocol. Participants underwent head‐up tilt (HUT) and lower‐body negative pressure (LBNP) in a randomized order, refered as condition 1 and condition 2 (red and blue blocks indicate the two conditions, while the grey blocks represent supine periods). Intensities were 22°, 42°, 58° and 80° for HUT, and −10, −20, −35 and −50 mmHg for LBNP.

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  FIGURE 2. The partial gravitational load or the hydrostatic gradient from head to foot (Gz) is equal to the sine of the head‐up tilt angle (sinθ) multiplied by the gravitational acceleration (g). Five angles were selected for the protocol: 0°, 22°, 42°, 58° and 80° (Negishi et al., 2017).

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  FIGURE 3. Examples of randomized sequences for the order of experimental conditions. Abbreviations: HUT, head‐up tilt; LBNP, lower‐body negative pressure.

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  FIGURE 4. Schematic representation of the blood shift (in millilitres) relative to the supine position measured through segmental bioimpedance during four angles of head‐up tilt (HUT) and four intensities of lower‐body negative pressure (LBNP): (A) thoracic fluid shift; (B) abdominal fluid shift; (C) pelvic fluid shift; and (D) leg fluid shift. Error bars indicate the SD. φSignificant differences between HUT and LBNP. ψSignificant effect of the orthostatic stress intensity. *Significant difference between modalities at a specific intensity. On the right is presented a schematic representation of the high‐resolution impedance meter using 10 electrodes to measure the fluid shift in the four areas.

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  FIGURE 5. Graphical representation of haemodynamic parameters during HUT and LBNP at equivalent modification of thoracic blood shift. The first row represents MAP responses, the second row SV and the third row HR. The left column represents the overall analysis, the middle column the analysis differentiating the participants according to their group, and the right column represents the analysis differentiating the participants according to their sex. Error bars indicate the SD. φSignificant effect of the LBNP. ψSignificant effect of the orthostatic stress intensity. *Significant difference between modalities at a specific intensity. θSignificant difference between Ctrl and T1D participants. ψSignificant difference between males and females. The bottom row represents effect sizes of haemodynamic parameters. Haemodynamic parameters are ordered from the largest positive effect size to the largest negative effect size. Grey dots represent a non‐significant difference. Black dots represent a significant effect of the main variable (LBNP, sex or diabetes). The colour gradient represents the interpretation of the effect size (0 < d < 0.2, trivial difference; 0.2 < d < 0.4, very low difference;…