The Evaluation of Multiple Impedance Thresholds on Cardiac Output and Perceived Exertion
Loading...
Date
2009-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The Ohio State University
Abstract
OBJECTIVE: The purposes of this study were to determine if relationships existed between cracking pressures of -7, -11, -15, and -19 cm H2O vs. cardiopulmonary physiologic parameters and Borg scale scores for healthy adults and to determine the maximum cracking pressure which does not produce a Borg score greater than 6. DESIGN: The study was designed as single blinded, randomized, and quasi-experimental with repeated measurements. Subjects served as their own controls. SETTING: Laboratory. SUBJECTS: 21 healthy, normotensive, normovolemic volunteers. METHODS: Subjects were continuously observed and monitored using bioimpedance for non-invasive cardiac output and heart rate, respiratory frequency and pulse oximetry. Subjects breathed through an Impedance Threshold Device (ITD) alternating between two-minute intervals of zero resistance and resistances of -7, -11, -15, and -19 cm H2O pressure. For randomization, subjects selected pre-set ITDs from a set of 4. During each level of resistance, maximum changes from baseline of cardiac output (CO), heart rate (HR), blood pressure (BP), respiratory rate (RR) and arterial oxygen saturation (SpO2) were recorded and subjects indicated their subjective feeling of exertion based on a Borg scale score from 1 to 10. RESULTS: There was a statistically significant strong negative correlation between cracking pressures and Borg scale scores (r = -0.814, p < 0.01). The percentage of subjects indicating a score of 6 or greater increased as the cracking pressures became more negative (0% - 43%). There were no statistically significant correlations between the cracking pressures and any of the physiological variables measured. An ANOVA analysis indicated that there were no statistically significant differences between the means of any physiological variables while subjects were breathing on the 5 cracking pressures. CONCLUSIONS: While the ITD can make normovolemic, normotensive, spontaneously breathing individuals feel like they are exerting more effort as the magnitude of its cracking pressure becomes more negative, there is no evidence to support that it causes any physiological changes within a 2 minute time period.
Description
School of Allied Medical Professions Honors Research Scholarship
Keywords
ITD, Impedance Threshold Devices, Cardiac Output, Borg Scale, Inspiratory Threshold Devices, Physiology, cracking pressure