Effects of reduced O2 delivery with anemia, hypoxia, or ischemia on peak VO2 and force in skeletal muscle

Abstract

This investigation was designed to describe alterations in O2 uptake (VO2) and tension development in a contracting in situ gastrocnemious-plantaris muscle preparation during three conditions of reduced O2 delivery [arterial O2 concentration X blood flow (Q)]. The three conditions, hypoxemia (H), ischemia (I), and anemia (A), were matched for O2 delivery. A normoxic normal flow condition was also utilized for comparison. H was produced by respiring the animals with 9% O2 in N2; I was produced by lowering Q, and A was produced by hemodilution with 6% dextran. The stimulation pattern for the isometric tetanic contractions used was 1 train/s, and each train was 200 ms, 70 Hz, and 6 V. The muscle was maximally contracted during each of the experimental conditions, and the conditions were administered in random order. In each bout the contractions continued for 5 min with 30 min of rest between bouts. Samples of arterial and muscle venous blood were obtained during the last 30 s of each bout. VO2 during I (125 ml.kg-1.min-1) was less than during N (145 ml.kg-1.min-1; P < 0.05) and greater than during H or A (104 and 101 ml.kg-1.min-1, respectively; P < 0.05). Venous PO2 (PVO2) was significantly lower during H (17.1 Torr) compared with the other conditions; no differences existed between N, I, and A (26.8, 26.0, and 28.1 Torr, respectively). Tension development was reduced by the reduction of O2 delivery during I, H, and A compared with N. Tension developed among the reduced O2 delivery groups was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioenergetics of contracting skeletal muscle after partial reduction of blood flow

“…As has been demonstrated previously (2,6,9,13,26), as blood flow was reduced in the present study the muscle was able to extract a higher percentage of the O 2 delivered by convective blood flow. A greater diffusion of O 2 to the mitochondria (for a higher extraction) was likely accomplished by reductions in intracellular PO 2 .…”

“…The present study demonstrated that when O 2 availability was reduced after normal steadystate conditions had been reached (fully aerobic contractions), the tight coupling of force production to respiration was maintained (see Fig. 3), as has been shown before in this highly oxidative muscle for moderate ischemia conditions (2,6,8,9,26). Muscle [ATP], [PCr], and lactate efflux during the I condition were not significantly different from the values seen at the same stimulation intensity with normal blood flow.…”

Myocardial metabolism and function in acutely ischemic and hypoxemic isolated rat hearts

“…PvO2 was less in H than I hearts, even at the same QO2, according to observations obtained by others in skeletal muscle (Hogan et al, 1992;Dodd et aL, 1993). It is difficult to assess whether this phenomenon is due to non-uniform perfusion secondary to low CPP in I hearts or to lactate-driven downregulation.…”

Anemia and cognitive performance in hospitalized older patients: results from the GIFA study

“…Low hemoglobin levels may influence oxygen delivery to skeletal muscle, and Figure 1. Adjusted* AMT mean scores (and 95% confidence intervals) for different hemoglobin levels, above and below the WHO anemia cut-points n ¼ Number of participants *Adjusted for age, gender, smoking, education, BMI, COPD, cerebrovascular disease, congestive heart failure, peptic ulcer, dementia, depression, hypertension, Charlson's Index, creatinine, ACE-inhibitors, antibiotics, corticosteroids, NSAIDs consequently negatively impact on muscular strength (Dodd et al, 1993) possibly as reported in respiratory disorders patients (Mador and Bozkanat, 2001;Sauleda et al, 2003). Chronic hypoxia is also responsible for pathophysiological changes leading to the onset or worsening of disabling processes (Silverberg et al, 2001).…”