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A Journal on Anesthesiology, Resuscitation, Analgesia and Intensive Care

Official Journal of the Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care
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Minerva Anestesiologica 2001 April;67(4):161-4

language: English

End tidal carbon dioxide monitoring in spontaneously breathing, nonintubated patients. A clinical comparison between conventional sidestream and microstream capnometers

Casati A., Gallioli G., Passaretta R., Scandroglio M., Bignami E., Torri G.

From the Depart­ment of Anes­the­sio­lo­gy (­Chief: ­Prof. G. Tor­ri) IRCCS H San Raf­faele Uni­ver­sity of ­Milan, ­Milan


Back­ground. To eval­u­ate the end ­tidal car­bon diox­ide esti­ma­tion in non­in­tu­bat­ed, spon­ta­ne­ous­ly breath­ing ­patients ­using ­either con­ven­tion­al side­stream or micro­stream cap­nom­e­ters.
Meth­ods. ­Patients ­received a region­al anes­the­sia tech­nique, ­while the end ­tidal car­bon diox­ide par­tial pres­sure (­EtCO2) was sam­pled ­through a ­nasal can­nu­la (­Nasal Fil­ter­Line, Nell­cor, Ple­san­ton, CA, USA) and meas­ured ­using ­either a con­ven­tion­al side­stream cap­nom­e­ter ­with a 200 ml·min-1 aspi­ra­tion ­flow ­rate, or a micro­stream cap­nom­e­ter (NBP-75®, Nell­cor Puri­tan Ben­nett, Ple­san­ton, CA, USA) ­with an aspi­ra­tion ­flow ­rate of 30 ml·min-1. ­After a 20 min peri­od ­with ­stable hemo­dy­nam­ic var­i­ables (sys­tol­ic arte­ri­al ­blood pres­sure with­in±20% ­from base­line val­ues), the ­EtCO2 was ran­dom­ly record­ed ­using one of the two cap­nom­e­ter ­while arte­ri­al ­blood was simul­ta­ne­ous­ly ­drawn ­from the radi­al ­artery and ana­lyzed for meas­ure­ment of arte­ri­al CO2 par­tial pres­sure. After­wards the ­nasal can­nu­la was con­nect­ed to the oth­er cap­nom­e­ter and the pro­ce­dure repeat­ed. ­Both the cap­nom­e­ter and arte­ri­al ­blood gas ana­lyz­er ­were cal­i­brat­ed ­before ­each stud­ied ­patient accord­ing to the man­u­fac­tur­er instruc­tions. The ­same pro­ce­dure was repeat­ed at ­least two ­times in ­each ­patient.
­Results. A ­total of 120 ­pairs of ­EtCO2 and ­PaCO2 meas­ure­ments ­were ­drawn ­from 30 ­adults (age: 69±5 ­years; ­weight: 70±10 kg; ­height: 160±10 cm): 60 ­using the con­ven­tion­al side­stream cap­nom­e­ter and 60 ­with the micro­stream one. The ­median arte­ri­al to end ­tidal CO2 ten­sion dif­fer­ence was 4.4 ­mmHg (range: 0.28 ­mmHg) ­with the micro­stream cap­nom­e­ter and 7 mm Hg (­range: 0-22 ­mmHg) ­with the con­ven­tion­al cap­nom­e­ter (p=0.02).
Con­clu­sion. The micro­stream cap­nom­e­ter pro­vides a ­more accu­rate end ­tidal CO2 par­tial pres­sure meas­ure­ment in non­in­tu­bat­ed, spon­ta­ne­ous­ly breath­ing ­patients ­than con­ven­tion­al side­stream cap­nom­e­ters, allow­ing for ade­quate mon­i­tor­ing of the res­pir­a­to­ry func­tion in non­in­tu­bat­ed ­patients.

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