Subject(s)
Child Behavior/psychology , Deception , Motivation , Perception , Attitude , Child , Female , Humans , MaleABSTRACT
To test the hypothesis that regulation of tissue oxygen (O2) extraction is disturbed in adult respiratory distress syndrome (ARDS), the relationship between O2 availability and O2 extraction ratio (O2ER) was studied in 36 patients with pulmonary edema who met the criteria for either ARDS (n = 21) or acute congestive heart failure (CHF) (n = 15). We found that in response to changes in the levels of O2 availability there was a significantly (p = 0.01) greater negative correlation of change in O2ER for the CHF (r = -0.67) than for the ARDS group (r = -0.41). Whereas patients with CHF eventually died of pump failure and low O2 delivery, the ARDS group developed multiorgan failure, especially renal failure, despite significantly higher ratios of O2 availability to O2 consumption. These findings suggest that patients with ARDS have lost their ability to regulate their tissue O2 extraction to compensate for changes in the availability of O2 in order to meet demand. Pulmonary capillary endothelial injury, through its role on whole-body metabolism, may be responsible for this observation.
Subject(s)
Oxygen/metabolism , Respiratory Distress Syndrome/metabolism , Adult , Aged , Cardiac Output , Female , Heart Failure/complications , Heart Failure/metabolism , Heart Failure/physiopathology , Hemodynamics , Humans , Male , Middle Aged , Oxygen/blood , Pulmonary Edema/etiology , Pulmonary Edema/metabolism , Pulmonary Edema/physiopathology , Respiratory Distress Syndrome/complications , Respiratory Distress Syndrome/physiopathologyABSTRACT
To assess the adequacy of oxygen availability and utilization within the cerebral cortex in vivo, we have measured the partial pressure of oxygen in tissue (PtO2), as well as the reduction oxidation state of cytochrome c oxidase (cyt aa3) during shock induced by slow or rapid hemorrhage in anesthetized cats. PtO2 was measured with pyrenebutyric acid-generated fluorescence in cerebral cortical cells. Cyt aa3 redox state was measured by the absorption of monochromatic light at 605 nm absorption peak of the enzyme reflected from the same cortical field. The PtO2 remained within the normal range until either 30 +/- 1.5 ml blood/kg was removed or the mean arterial pressure fell by 70 +/- 5% of base line. Beyond either point, the PtO2 fell rapidly to a low value approximating zero. By contrast, the reduction of cyt aa3 began early when as little as 5 ml blood/kg was removed. Thereafter, the shift toward reduction was progressive and continuous with a slow rate at first and a rapid rate later. This accelerated rate of cyt aa3 reduction preceded the rapid fall of PtO2. We concluded that, under these experimental conditions, cyt aa3 reduction is a much earlier and more sensitive indicator of perturbed intracellular aerobic metabolism due to hemorrhage that is PtO2.
