Jc. Stein et al., RELATIONSHIP BETWEEN CAPILLARY AND SYSTEMIC VENOUS PO2 DURING NONHYPOXIC AND HYPOXIC VENTILATION, The American journal of physiology, 265(2), 1993, pp. 80000537-80000542
We evaluated the relationship between end-capillary and systemic venou
s PO2 values in the retractor muscle of 14 anesthetized hamsters durin
g both nonhypoxic and hypoxic ventilation to ascertain whether the lev
el of tissue oxygenation could be reliably estimated from the systemic
parameter. End-capillary PO2 was estimated from measurements of oxyge
n saturation in capillaries at the venular end of the network obtained
using in vivo video microscopy and computer-aided image-analysis tech
niques at three different levels of inspired oxygen (0.3, 0.21, and 0.
1). Measurements of systemic arterial and venous blood gases were made
in conjunction with these capillary determinations. In addition, in a
portion of the study we utilized an oxygen microelectrode to determin
e the PO2 in the first-order venule draining the portion of the muscle
containing the capillaries under study. We found that only when the a
nimals were made acutely hypoxic was there any correspondence between
the systemic venous and end-capillary PO2 values. In addition, these d
ata provide support for the presence of arteriovenous shunting of oxyg
en during nonhypoxic ventilation.