Comparison of air tonometry with gastric tonometry using saline and other equilibrating fluids: an in vivo and in vitro study

Abstract

There are clinically significant differences in values for gastric mucosal PCO2 measured by air tonometry and saline tonometry both in vivo and in vitro.

Regional carbon dioxide monitoring to assess the adequacy of tissue perfusion

“…While air tonometry has simplified the measurement process (over saline tonometry) and eliminated the possible errors associated with the use of non-buffered saline this technology has a number of limitations [44][45][46]85,86]. Gastric tonometry is logistically and practically difficult and this may be the main factor that has prevented the widespread use of this technology.…”

“…Air tonometry, particularly in conjunction with an automated system has a number of advantages when compared with conventional saline tonometry. Unlike saline tonometry, in-vitro studies have demonstrated that air tonometry has a very low bias with excellent precision [44][45][46]. Furthermore, automated air tonometry has an equilibration time of less than 20 minutes and being fully automated may eliminate potential sources of error associated with saline tonometry.…”

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“…It has been recognized, however, that saline may yield erroneous PCO 2 values, and that the bias may depend on the solution and the type of blood gas machine used to measure PCO 2 [1,3,4,5]. Indeed, the bias may be buffer- and pH-dependent [1,3,5].…”

“…Some of these problems may be avoided with air tonometry, in which surrounding intraluminal gastric carbon dioxide is allowed to rapidly equilibrate with the air-filled tonometer balloon PCO 2 [4,6]. Various types have been proposed, depending on the mode of recirculation of air in the catheter between measurement intervals, and one is commercially available (Tonocap; Datex, Helsinki, Finland) [1,5,6].…”

Effect of temperature on gastric intramucosal P CO 2 measurement by saline and air tonometry

“…However, the tonometric measurements of Pi CO 2 needed to calculate these parameters may be influenced by various factors, including temperature [1,2].…”