Baroreflex sensitivity during rest and pressor challenges in obstructive sleep apnea patients with and without CPAP

Fig. 1.. Protocol timeline. Protocol timeline showing procedure (top), duration in minutes (middle) and participant position (bottom). Colored areas show data used for analysis, with green indicating rest or baseline and recovery, and red indicating tasks. BP = blood pressure; CNAP = continuous non-invasive arterial pressure; ECG = electrocardiogram; HG= Handgrip; Val= Valsalva..

Fig. 2.. Sample traces illustrating baroreflex sensitivity (BRS) calculation. Illustration of the BRS sequence analysis method in Acqknowledge 5.0. Ascending and descending sequences are defined as at least three cycles showing changes in blood pressure of at least 0.5 mmHg and changes in RR interval of at least 1 ms. For each systolic blood pressure (SBP)-to-SBP change (dSBP), the corresponding change in RR interval (t) is extracted, and the BRS is calculated as the absolute value of the regression coefficient of the change in t over dSBP over the sequence.

Fig. 3.. Sample traces in control and OSA participants illustrating baroreflex sensitivity (BRS) in different task periods. Examples illustrating blood pressure (BP) and heart rate (HR) patterns associated with a range of BRS values during rest (top row), handgrip (HG; middle row) and Valsalva (Val; bottom row), in control (left column) and untreated OSA (right column) participants. The x- and y-axes were similarly scaled in all graphs. Shaded areas show when a task (handgrip or Valsalva) was performed.

Fig. 4.. BRS changes during tasks. BRS mean ± SEM values during rest, handgrip (HG) and Valsalva (Val) are shown in untreated OSA (unOSA), CPAP treated OSA (cpOSA), and control (CON) in combined (A), female (B), and male (C) groups. p–values from independent two sample t-tests are shown (*≤0.05).

Fig. 5.. BRS correlations between rest and task. Scatterplots of BRS (ms/mmHg) of (A) Valsalva vs rest, and (B) handgrip vs rest in untreated OSA (unOSA), CPAP treated OSA (cpOSA), and control (CON).

Fig. 6.. BPV changes during tasks. BPV mean ± SEM values during rest, handgrip (HG) and Valsalva (Val) are shown in untreated OSA (unOSA), CPAP treated OSA (cpOSA) and control (CON) in the combined sample (A), females (B) and males (C). p–values from independent two sample t-tests are shown (* <0.05, ** <0.01, *** <0.001).

Fig. 7.. BRS and BPV correlations. Scatterplots of BPV (mmHg) vs BRS (ms/mmHg) in untreated OSA (unOSA), CPAP treated OSA (cpOSA), and control (CON) during (A) rest, (B) handgrip (HG) and (C) Valsalva (Val).