Objectives: The ultrasonic cardiac output monitor is a noninvasive, quantitative method for measuring and monitoring cardiovascular hemodynamic parameters in patients. The aims of this study were first to establish reference ranges for cardiovascular indices measured by the ultrasonic cardiac output monitor in Chinese children aged 12–18 yr, second to assess the interobserver reliability of the method, and third to compare these ranges with a Caucasian group from Australia.
Design, Setting, and Subjects: This was a population-based cross-sectional cohort study of Chinese adolescents 12–18 years old, performed in secondary schools in Hong Kong.
Interventions: Ultrasonic cardiac output monitor scans were performed on each subject to measure stroke volume, cardiac output, and systemic vascular resistance together with standard oscillometric measurement of blood pressure and heart rate. Ultrasonic cardiac output monitor parameters were also standardized by deriving body surface area referenced indices. Normal ranges were defined as lying within two standard deviations on either side of the mean. To assess interobserver variability, a second, blinded operator repeated 17% of scans.
Measurements and Main Results: A total of 590 Chinese adolescents (49% boys) were scanned. Normal ranges for cardiac output, cardiac index, stroke volume, stroke volume index, stroke volume resistance, and systemic vascular resistance index are presented. Males had a significantly higher mean stroke volume, cardiac output, and systemic vascular resistance index compared with females (p < 0.05), but no significant differences were found for the indexed values. When compared with a group of 31 Australian Caucasian adolescents (71% boys), Chinese adolescents have a significantly lower cardiac output and stroke volume (p <0.05), but these differences disappeared when adjusted for body surface area (i.e., stroke volume index, cardiac index, and systemic vascular resistance index). Interobserver variability of ultrasonic cardiac output monitor–derived stroke volume showed a coefficient of variation of 10.2%, a correlation coefficient of 0.90 (95% confidence interval 0.85–0.93), while Bland-Altman analysis showed a mean bias of 1.5% (95% limits of agreement were –19.9% to 23.0%).
Conclusions: This study presents normal values for cardiovascular indices in Chinese adolescents using the ultrasonic cardiac output monitor. When referenced to body surface area, the differences between Caucasians and Chinese were insignificant.
1Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong, Hong Kong, China.
2Faculty of Medicine, University of Melbourne, Melbourne, Australia.
3Emergency Department, Princess Royal University Hospital, London, UK.
4School of Biomedical Science, Charles Sturt University, Bathurst, New South Wales, Australia.
5Intensive Care Unit, Bathurst Base Hospital, Bathurst, New South Wales, Australia.
This study was performed at Chinese University of Hong Kong.
Supported, in part, by an internal grant of HK$72,000 (approximately U.S.$9,000) from the Chinese University of Hong Kong to conduct the “Healthy Children’s Vital Signs and USCOM Study,” a grant of HK$100,000 (approximately U.S.$13,000) from the Hong Kong College of Emergency Medicine, and a grant of HK$466,652 (approximately U.S.$60,000) from the Health Services Research Fund of the Food and Health Bureau.
Drs. Chan, Graham, and Rainer received grant support from the Chinese University of Hong Kong, Hong Kong College of Emergency Medicine and the Health Services Research Fund of the Food and Health Bureau. Dr. Rainer is employed by, has received support for travel, and has patents with the Chinese University of Hong Kong (not related to this work); and has provided expert testimony for the government. Dr. Cattermole received support for travel and USCOM presentation from Pacific Medical. The remaining authors have not disclosed any potential conflicts of interest.
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