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Validation of a new spectrometer for noninvasive measurement of cardiac output

Baum, Marc M. and Kumar, Sasi and Moss, John A. and Wagner, Peter D. (2004) Validation of a new spectrometer for noninvasive measurement of cardiac output. Review of Scientific Instruments, 75 (7). pp. 2290-2299. ISSN 0034-6748. doi:10.1063/1.1764606.

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Acetylene is a blood-soluble gas and for many years its uptake rate during rebreathing tests has been used to calculate the flow rate of blood through the lungs (normally equal to cardiac output) as well as the volume of lung tissue. A new, portable, noninvasive instrument for cardiac output determination using the acetylene uptake method is described. The analyzer relies on nondispersive IR absorption spectroscopy as its principle of operation and is configured for extractive (side-stream) sampling. The instrument affords exceptionally fast (30 ms, 10%–90%, 90%–10%, at 500 mL min–1 flow rates), interference-free, simultaneous measurement of acetylene, sulfur hexafluoride (an insoluble reference gas used in the cardiac output calculation), and carbon dioxide (to determine alveolar ventilation), with good (typically ±2% full-scale) signal-to-noise ratios. Comparison tests with a mass spectrometer using serially diluted calibration gas samples gave excellent (R2>0.99) correlation for all three gases, validating the IR system's linearity and accuracy. A similar level of agreement between the devices also was observed during human subject C2H2 uptake tests (at rest and under incremental levels of exercise), with the instruments sampling a common extracted gas stream. Cardiac output measurements by both instruments were statistically equivalent from rest to 90% of maximal oxygen consumption; the physiological validity of the measurements was confirmed by the expected linear relationship between cardiac output and oxygen consumption, with both the slope and intercept in the published range. These results indicate that the portable, low-cost, rugged prototype analyzer discussed here is suitable for measuring cardiac output noninvasively in a point-of-care setting.

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Additional Information:©2004 American Institute of Physics. (Received 16 December 2003; accepted 4 April 2004; published online 21 June 2004) This research was carried out under the sponsorship of the National Medical Technology TestBed (NMTB) (Subagreement No. 2000-08-OCIofS-Baum). The authors gratefully acknowledge the valuable assistance provided by this program.
Subject Keywords:mass spectrometers; pneumodynamics; lung; blood flow measurement; infrared spectroscopy; cardiology; physiology; biomedical equipment
Issue or Number:7
Record Number:CaltechAUTHORS:BAUrsi04
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1991
Deposited By: Archive Administrator
Deposited On:28 Feb 2006
Last Modified:08 Nov 2021 19:44

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