ISSN:
1741-0444
Keywords:
Automatic measurement
;
Carbon dioxide sensitivity
;
Occlusion pressure
;
Respiration
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract An index of the output of the respiratory centre may be obtained by measuring the subatmospheric pressure developed in the airway 0·1 s after the start of an inspiration against an occluded airway (P0.1). This index of respiratory drive is independent of the effects of impaired pulmonary mechanics and a pure measure of central sensitivity to carbon dioxide may be obtained by plotting the P0.1 response while breathing an increasing concentration of carbon dioxide. In the method described here the airway was occluded for a short time (0·12 s) from the start of inspiration using an electronically operated solenoid valve. The valve produced silent occlusions which were of short duration and did not perturb ventilation. The subatmospheric pressure (P0·1) and end-tidal carbon dioxide tension (Pe'CO2) were automatically sampled and plotted on an xy-recorder. The slope of the linear plot of P0·1 against PE'CO2 was then derived (P0·1/PE'CO2). There was good correlation between P0·1/PE'CO2 and the slope of the ventilatory response to carbon dioxide in normal subjects (r=0·91). Morphine produced significant depression (P〈0·05) of P0·1/PE'CO2 in a group of eight normal healthy volunteers, indicating central depression of carbon dioxide sensitivity. The automatic sampling and plotting of P0·1 and PE'Co2 enabled rapid and simple measurements to be made with high precision and no observer bias. This technique has significant advantages over conventional manual methods of deriving P0·1/PE'CO2 and is suitable for routine clinical use.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02442545
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