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In Vivo vs. In Vitro Response Time of Trancutaneous P o2 Electrodes A comparison of four devices in newborn infants
Author(s) -
Versmold H. T.,
Linderkamp O.,
Stuffer K. H.,
Holzmann M.,
Riegel K. P.
Publication year - 1978
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1978.tb01391.x
Subject(s) - medicine , in vivo , in vitro , genetics , biology
Four devices for transcutaneous P o2 (tcP o2 ) monitoring have been applied simultaneously in 16 infants. Both during a maximal change in Pa o2 and during physiological P o2 variations, the in vivo response time of the electrodes did not show the differences observed in vitro. We compared A, a prototype of the electrode by Huch, Lübbers and Huch (25 μm Teflon membrane); B, the commercial version of A by Hellige‐Draeger (25 μm Teflon); C, the Radiometer TCM I oxygen monitor (25 μm polypropylene); and D, the Roche macrocathode electrode (6 μm Mylar), at 44d̀C. In vitro the 50% response times were 2.9 ( A ), 4.4 ( B ), 3.7 ( C ), and 7.4 ( D ) sec. The rates of tcP o2 changes at the midpoint of the response curves were 3.8 ( A ), 2.0 ( B ), 3.0 ( C ), and 1.7 ( D ) kPa/sec. In vivo during a sudden change from hyperoxaemia (Fi o2 1.0) to normoxaemia the respective rates were 0.6 ( A ), 0.8 ( B ), 1.1 ( C ) and 1.0 ( D ) kPa/sec. The in vivo 50% response times were 53.3 ( A ), 51.1 ( B ), 46.2 ( C ), and 45.3 ( D ) sec. The lag time between Pa o2 and tcP o2 was about one third of this overall response time. The response to more physiological variations of Pa o2 (periodic breathing) was not different among the tested electrodes in terms of damping and of delay of the tcP o2 deflections. In a steady state the correlation of tcP o2 44d̀C vs Pa o2 was close ( r = 0.98) with all devices up to 6.1 kPa (456 torr).