On-line computer estimation of carbon dioxide response curves |
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Authors: | Duane L Sherrill MS Dr George D Swanson PhD |
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Institution: | (1) Department of Biometrics, University of Colorado School of Medicine, Denver, CO;(2) Department of Mathematics, University of Colorado, Denver, CO;(3) Dept of Anesthesiology, University of Colorado School of Medicine, Denver, CO;(4) Dept of Anesthesiology, University of Colorado School of Medicine, 4200 E Ninth Ave, Box B-113, 80262 Denver, CO |
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Abstract: | Anesthesiologists are concerned with the effect of various anesthetics on a patient's central nervous ventilatory control. The most widely accepted method of determining the effect of a drug is to compare carbon dioxide response curves (
e/PetCO2, where
e = minute ventilation in L/min] andPetCO2 = end-tidal carbon dioxide in mm Hg]) measured before and after administration of the drug. Additional information concerning neuromechanical control can be obtained by also including a measure of the airway occlusion pressure (generally measured 100 ms after occlusion, i.e., P100).To facilitate these measurements we have developed a portable, computer-controlled data acquisition system. It includes an Apple II+ computer and measures
e,PetCO2, and P100. Each subject rebreathes exhaled carbon dioxide through a two-way breathing valve attached to a 9-liter reservoir, which is initially filled with 5% carbon dioxide and balance oxygen. Exhaled carbon dioxide concentrations are measured with an infrared medical gas analyzer on samples taken through a catheter connected at the mouthpiece. The exhaled flow is measured with a pneumotachograph in conjunction with a differential pressure transducer, and P100 is determined with a Validyne MP45 pressure transducer. |
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Keywords: | Measurement techniques Equipment computer data acquisition Statistics linear regression Carbon dioxide hypercapnic response ventilatory response Ventilation carbon dioxide response curves central nervous ventilatory control |
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