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Biomedical subjects

R Weiskopf

Publications and source records attributed to R Weiskopf.

8 recordsLinked to original sources
PubMed2000

Subcutaneous perfusion and oxygen during acute severe isovolemic hemodilution in healthy volunteers.

HYPOTHESIS: Acute severe isovolemic anemia (to a hemoglobin [Hb] concentration of 50 g/L) does not decrease subcutaneous wound tissue oxygen tension (PsqO(2)). SETTING: University hospital operating room and inpatient general clinical research center ward. SUBJECTS: Twenty-five healthy, paid volunteers. METHODS: Subcutaneous oxygen tension and subcutaneous temperature (Tsq) were measured continuously during isovolemic hemodilution to an Hb level of 50 g/L. In 14 volunteers (initially well-perfused), "normal" perfusion (Tsq >34.4 degrees C) was achieved by hydration and systemic warming prior to starting isovolemic hemodilution, while in 11 volunteers (perfusion not controlled [PNC]), no attempt was made to control perfusion prior to hemodilution. MAIN OUTCOME MEASURES: Measurements of PsqO(2), Tsq, and relative subcutaneous blood flow (flow index). RESULTS: While PsqO(2), Tsq, and flow index were significantly lower in PNC vs well-perfused subjects at baseline, there was no significant difference between them at the Hb of 50 g/L (nadir). Subcutaneous PO(2) did not decrease significantly in either group. Arterial PO(2) was not different between the groups, and did not change significantly over time; Tsq and flow index increased significantly from baseline to nadir Hb in both groups. CONCLUSIONS: The level of PsqO(2) was maintained at baseline levels during hemodilution to Hb 50 g/L in healthy volunteers, whether they were initially well-perfused or mildly underperfused peripherally. Given the significant increase in Tsq and flow index, this resulted from a compensatory increase in subcutaneous blood flow sufficient to maintain oxygen delivery. Wound healing depends to a large extent on tissue oxygen delivery, and these data suggest that even severe anemia by itself would not be sufficient to impair wound healing. Thus, transfusion of autologous packed red blood cells solely to improve healing in surgical patients with no other indication for transfusion is not supported by these results.

Acute Disease↗
PubMed1979

The nature of the perception of effort at sea level and high altitude.

The purpose of this study was to compare perceptual responses (RPE) and selected physiological measures during both short term and prolonged exercise of equal relative intensities at 4300 m to those at sea level. Specifically, we compared results obtained (n=20) for 6 min of exercise at 60, 80 and 95% VO2max and at 5 min intervals during exercise to exhaustion at 85% VO2max. At 4300 m, VO2max was reduced 19%, while VEmax and Rmax increased 17 and 8%, respectively. HRmax and RPEmax was unchanged. For any given relative exercise intensity, VO2 and absolute exercise intensity (kpm-min-1) were reduced, while VE was about 12% and R about 7% greater at 4300 m; HR was unchanged. At 4300 m, RPE at the lower intensities of submaximal exercise and early during prolonged exercise were significantly less than at sea level. These differences were reduced and finally eliminated as exercise intensity increased toward maximal or as prolonged exercise continued to exhaustion. Endurance time to exhaustion at 4300 m was not different from that at sea level. To account for the perceptual differences between exercise at 4300 m an sea level, we proposed that local factors (muscular strain) exert greater influence on the perception of effort at exercise intensities which do not greatly stress ventilation and circulation, while central factors exert greater influence on the perception of effort at exercise intensities at which tachypnea and tachycardia are of sufficient magnitude to be perceived as extremely stressful.

Adult↗