Reliability of the Acetylene Single-Breath Method For Measuring Cardiac Output
Holm, Christopher David
MetadataShow full item record
Abstract Reproducibility of the Acetylene Single-Breath Technique For Measuring Cardiac Output During Ramping Exercise Testing Christopher Holm Committee Chair: William G. Herbert, Ph.D. Advances in technology have now made it possible to analyze cardiac output (Q) with only a single-breath, making measurements during exercise quicker and less invasive for the subject. Certain non-invasive techniques allow for measurement of the disappearance of a soluble inert gas as it diffuses across the blood-gas barrier in the lungs. The rate of disappearance of the gas is directly proportional to the flow of blood past the lungs and subsequently provides an estimate of pulmonary capillary blood flow (Qc), or Q. The SensorMedicsÂ® Corporation (Yorba Linda, CA) has developed a single-breath acetylene (C2H2) technique (SensorMedics Vmax 229TM), which includes a simple device to linearize expiratory flow rate by increasing the time by which the sensors can measure the disappearance of the marker gas and improve quantification. The purpose of this investigation was to determine the reproducibility of the C2H2 single-breath technique during ramping exercise testing with the addition of a starling resistor in 11 apparently healthy, sedentary volunteers (7 male and 4 female). Subjects performed three maximal ramping exercise test sessions over a 6-week period and Qc was measured at rest and at three time points during the exercise test. The reproducibility of the C2H2 single-breath method of determining Qc during exercise was assessed using intraclass correlation coefficient (r) found through repeated measures ANOVA. The C2H2 single-breath Qc measurement technique was shown to be repeatable as exercise intensity increased in an apparently healthy, sedentary population. This method was able to capture Qc measurements at intensities greater than 75% VO2pk in all subjects with the use of the Starling resistor. The single-breath technique was also shown to be consistent over three trials when compared with VO2 measurements (r2=0.72-.74, p<0.001), but much lower than previously reported. This device is showed limited reproducibility (r= -0.11-.40) of the sensors to accurately analyze Qc with the subjects who are unfamiliar and have difficulty with the single-breath maneuver. Such instances make it difficult for objective, accurate determinations to be made by the clinician. More evidence needs to be evaluated before use of this device can be applied to a clinical setting.
- Masters Theses