Changes in pulse wave transit time variability after interscalene brachial plexus block placement

Figures

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  Fig. 1.. Calculation of the PWTT. The second-derivative PPG waveform was generated by differentiating the first-derivative PPG waveform. The cursor placed on the peak of the second-derivative PPG waveform intersects the ECG waveform. By subtracting the time corresponding to the R peak of the ECG waveform from the peak of the second-derivative PPG waveform, the PWTT was calculated to be 160 ms. ECG: electrocardiography, ms: milliseconds, PPG: photoplethysmography, PWTT: pulse wave transit time.

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  Fig. 2.. Longitudinal changes in the PWTT, LF and HF, blood pressure, and heart rate in one patient receiving an ISBPB. The upper panel displays the patient’s spectrogram that shows the power at each Hz during the study period using a rainbow color spectrum. The X, Y, and Z axes represent the study time in seconds, frequency in Hz, and natural log-transformed power in ln(ms2/Hz), respectively. The natural log-transformed power is displayed with rainbow color shading, with redder colors corresponding to higher powers and bluer colors corresponding to lower powers. The middle panel shows visually significant changes in the LF and HF extracted from the spectrogram and the PWTT. The lower panel shows clinically unremarkable changes in blood pressure and heart rate during the study period. PWTT: pulse wave transit time, LF: low-frequency power, HF: high-frequency power, ISBPB: interscalene brachial plexus block.

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  Fig. 3.. Longitudinal changes in the PWTT, lnHF and lnLF after block needle introduction for ISBPB placement. The data are presented as estimated marginal means and their 95% CIs. The P values of the within-subject effect are < 0.001 for the PWTT, 0.13 for the lnHF, and < 0.01 for the lnLF. *P < 0.001 compared with baseline, †P < 0.01 compared with baseline, ‡P < 0.05 compared with baseline; 5–10 min post-needle insertion: between 5 and 10 min after block needle introduction; 15–20 min post-needle insertion: between 15 and 20 min after block needle introduction; baseline: during 5 min before the end of acclimatization; lnHF: natural log-transformed high-frequency power of PWTTV; lnLF: natural log-transformed low-frequency power of PWTTV; PWTT: pulse wave transit time; PWTTV: pulse wave transit time variability.

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  Fig. 4.. Relationships of baseline-adjusted changes in pupil diameter with changes in the PWTT (A), lnHF (B), and lnLF (C) from baseline to 15–20 min post-needle insertion. The solid line represents the linear regression model, whereas the two dotted lines represent the 95% CIs of the values predicted from the regression model. PWTT: pulse wave transit time, lnHF: natural log-transformed high-frequency power of PWTT variability, lnLF: natural log-transformed low-frequency power of PWTT variability, 15–20 min post-needle insertion: between 15 and 20 min after introduction of the block needle, baseline: during the 5 min before the end of acclimatization.