Objective: For years researchers have been attempting to understand the relationship between central hemodynamics and the resulting peripheral waveforms. This study is designed to further understanding of the relationship between ear pulse oximeter waveforms, finger pulse oximeter waveforms and cardiac output (CO). It is hoped that with appropriate analysis of the peripheral waveforms, clues can be gained to help to optimize cardiac performance.
Methods: Part 1: Studying the effect of cold immersion test on plethysmographic waveforms. Part 2: Studying the correlation between ear and finger plethysmographic waveforms and (CO) during CABG surgery. The ear and finger plethysmographic waveforms were analyzed to determine amplitude, width, area, upstroke and downslope. The CO was measured using continuous PA catheter. Using multi-linear regression, ear plethysmographic waveforms, together with heart rate (HR), were used to determine the CO Agreement between the two methods of CO determination was assessed.
Results: Part 1: On contralateral hand immersion, all finger plethysmographic waveforms were reduced, there was no significant change seen in ear plethysmographic waveforms, except an increase in ear plethysmographic width. Part 2: Phase 1: Significant correlation detected between the ear plethysmographic width and other ear and finger plethysmographic waveforms. Phase 2: The ear plethysmographic width had a significant correlation with the HR and CO. The correlation of the other ear plethysmographic waveforms with CO and HR are summarized (Table 5). Multi-linear regression analysis was done and the best fit equation was found to be: CO=8.084 - 14.248 x Ear width + 0.03 x HR+ 92.322 x Ear down slope+0.027 x Ear Area Using Bland & Altman, the bias was (0.05 L) but the precision (2.46) is large to be clinically accepted.
Conclusion: The ear is relatively immune to vasoconstrictive challenges which make ear plethysmographic waveforms a suitable monitor for central hemodynamic changes. The ear plethysmographic width has a good correlation with CO.