Measurement of tissue oxygen tension: Comparison between two subcutaneous oxygen tonometers

Abstract

We compared the 95% response time (95% RT) of two tissue oxygen tonometers under two sets of circumstances. We first evaluated the devices during normoxia, hyperoxia, and anoxia in vitro, using a transcutaneous PO2 electrode (PtcO2) as the reference. The responses to normoxia and to different grades of hyperoxia were examined in vivo in 8 healthy volunteers to assess the relationship between changes in subcutaneous PO2 and PtcO2, an estimate of arterial PO2 (PaO2). One subcutaneous method (ScA) used a technique based on a polarographic needle electrode in situ connected to an ammeter; the second method (ScB) was based on a blood gas analyzer system first described by Hunt (Lancet 164;2:1370). ScA and PtcO2 both responded to stepwise changes in ambient oxygen concentration (21-100%) in vitro within 10 seconds; the 95% RT of ScA was 1.39 +/- 0.5 to 2.39 +/- 0.8 minutes and that of PtcO2 was 0.32 +/- 0.1 to 0.49 +/- 0.1 minutes. ScB had a lag of 3 minutes, and the 95% RT was 6.75 +/- 0.5 to 8.2 +/- 0.8 minutes. In contrast to the results in vitro, the response of ScA to changes in FiO2 in vivo was delayed compared with the rapid response of PtcO2, reflecting the physiologic delay of tissue PO2 in response to increased PaO2. The time lag and the long 95% RT of ScB were even more evident in vivo. ScA reacted three to four times faster than ScB, both in vitro and in vivo, to changes in the oxygen environment. The in vitro 95% RT of ScA to changes in ambient oxygen varied from 2 to 3.5 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous amperometric monitoring of subcutaneous oxygen in rabbit by telemetry

“…Reports of subcutaneous oxygen tension in air-breathing animals have been somewhat variable, but generally have ranged from 35 [21]. Ertefai and Gough obtained 26 -37 Torr in the anesthetized rat [12], results similar to those of Kerger et al who studies the hamster [4].…”

A novel macroencapsulating immunoisolatory device: the preparation and properties of nanomat-reinforced amphiphilic co-networks deposited on perforated metal scaffold

“…Pancreatic islets, particularly porcine islets, are very dependent on oxygen (Ohta et al 1980;Dionne 1989;Hyder et al 1998;Guyton 1991;Soini and Takala 1991;Ward et al 2002;Klossner et al 1974) with an oxygen consumption rate in vitro of 2.5-3 nmol/min per 100 islets and increasing in response to elevated glucose levels (Dionne 1989;Hyder et al 1998;Guyton 1991). Insulin secretion decreases significantly when pO 2 falls below 60 mmHg (Soini and Takala 1991;Ward et al 2002;Klossner et al 1974). The process of islet isolation, culture, and subsequent transplantation results in hypoxia and an immediate loss of islet tissue (Ohta et al 1980;Davalli et al 1996).…”

“…The amount of oxygen would depend upon passive diffusion within the implantation site with the partial pressure of oxygen (pO 2 )~95 mmHg in arterial blood,~40 mmHg in venous blood, and ranges from 35 to 60 mmHg in the peritoneum and subcutaneous tissues (Carlsson et al 1998;Zacharovova et al 2005;Sweet and Gilbert 2006;Hellerstrom 1967). Pancreatic islets, particularly porcine islets, are very dependent on oxygen (Ohta et al 1980;Dionne 1989;Hyder et al 1998;Guyton 1991;Soini and Takala 1991;Ward et al 2002;Klossner et al 1974) with an oxygen consumption rate in vitro of 2.5-3 nmol/min per 100 islets and increasing in response to elevated glucose levels (Dionne 1989;Hyder et al 1998;Guyton 1991). Insulin secretion decreases significantly when pO 2 falls below 60 mmHg (Soini and Takala 1991;Ward et al 2002;Klossner et al 1974).…”