[Bronchospasmolysis without adrenaline effect].

Six mainstream and twelve sidestream infrared carbon dioxide (CO2) analysers were tested for accuracy of the CO2 display value, alarm activation and the effects of nitrous oxide (N2O), oxygen (O2) and water vapour according to the ISO Draft International Standard (DIS)#9918. Mainstream analysers (M-type): Novametrix Capnogard 1265; Hewlett Packard HP M1166A (CO2-module HP M1016A); Datascope Passport; Marquette Tramscope 12; Nellcor Ultra Cap N-6000; Hellige Vicom-sm SMU 611/612 ETC. Sidestream analysers: Brüel & Kjaer Type 1304; Datex Capnomac II; Marquette MGA-AS; Datascope Multinex; Ohmeda 4700 OxiCap (all type S1: respiratory cycles not demanded); Biochem BCI 9000; Bruker BCI 9100; Dräger Capnodig and PM 8020; Criticare Poet II; Hellige Vicom-sm SMU 611/612 A-GAS (all type S2: respiratory cycles demanded). The investigations were performed with premixed test gases (2.5, 5, 10 vol%, error < or = 1% rel.). Humidification (37 degrees C) of gases were generated by a Dräger Aquapor. Respiratory cycles were simulated by manually activated valves. All monitors complied with the tolerated accuracy bias in CO2 reading (< or = 12% or 4 mmHg of actual test gas value) for wet and dry test gases at all concentrations, except that the Marquette MGA-AS exceeded this accuracy limit with wet gases at 5 and 10 vol% CO2. Water condensed in the metal airway adapter of the HP M1166A at 37 degrees C gas temperature but not at 30 degrees C. The Servomex 2500 (nonclinical reference monitor), Passport (M-type), Multinex (S1-type) and Poet II (S2-type) showed the least bias for dry and wet gases. Nitrous oxide and O2 had practically no effect on the Capnodig and the errors in the others were max. 3.4 mmHg, still within the tolerated bias in the DIS (same as above). The difference between the display reading at alarm activation and the set point was in all monitors (except in the Capnodig: bias 1.75 mmHg at 5 vol% CO2) below the tolerated limit of the DIS (difference < or = 0.2 vol%). The authors conclude that the tested monitors are safe for clinical used (except those failing the DIS limits). The accuracy of the CO2-reading (average of mean absolute bias) is better in the M-type than in the S1- or S2-type analysers although no statistical (nor clinical) significant differences could be detected. Most manufacturers work with stricter limits than those proposed by the DIS.

Blood Gas Analysis↗

PubMed1995

Cerebral metabolic management.

Knowledge of cerebral metabolic variables increases the information available for managing the head-injured patient. This article reviews normal cerebral metabolism and describes the derangement of metabolism observed in patients with head trauma. Cerebral metabolism is globally decreased by one third to one half in the severely head-injured patient, usually because of the lower metabolic expenditure associated with coma, but sometimes because of superimposed hypoxia/ischemia, primarily due to secondary insults. Measurement of jugular venous oxygen saturation has become the most useful method for monitoring cerebral metabolism in the ICU. Although jugular venous oxygen saturation does not provide quantitative information about either cerebral blood flow or cerebral metabolism, it reflects the ratio between these two variables. To maintain a sufficient level of available oxygen and energy production at the cellular level, there are two therapeutic strategies: a) hemodynamic and b) metabolic. Treatments can be directed at both increasing oxygen delivery and integrating hemodynamic handling, and at various pharmacologic or physical methods intended to reduce the cerebral metabolic demand. The latter strategy is designed to depress either the basal or activation components of cerebral metabolism. This strategy includes manipulations of brain temperature and the use of central nervous system-depressant, barbiturate, and similar drugs.

Blood Gas Analysis↗