A comparison of Q̇t and a-vO₂ in individuals with HIV taking and not taking HAART

Purpose: The aim of this study was to determine whether highly active antiretroviral therapy (HAART), rather than the direct effect of HIV infection, limits peripheral muscle oxygen extraction-utilization (a-vO₂) in individuals infected with the human immunodeficiency virus (HIV). Methods: Fifteen subjects (6 female and 9 male) with HIV taking HAART, 15 subjects infected with HIV not taking HAART, and 15 healthy gender and activity level matched non-HIV infected controls (N = 45) performed an maximal treadmill exercise test to exhaustion, Noninvasive cardiac output (Q̇t) was measured at each stage and at peak exercise using the indirect Fick method based on the exponential rise carbon dioxide rebreathing method. Intergroup comparisons were adjusted for interactions of peak oxygen consumption (VO₂), body surface area, and Q̇t using ANCOVA. Results: Peak a-vO₂ was significantly lower (P < 0.05) in subjects with HIV taking HAART (10.0 ± 0.5 vol%) compared with subjects with HIV not taking HAART (11.7 ± 0.5 vol%) and noninfected controls (12.7 ± 0.5 vol%). In subjects with HIV taking HAART, peak heart rate (HR) (170.5 ± 3.9 bpm) was lower than (P < 0.05) and stroke volume (Vs) (123.0 ± 3.9 mL.beat-1) at peak exercise was higher (P < 0.05) than subjects with HIV not taking HAART (179.9 ± 3.5 bpm) (106.6 ± 3.9 mL·beat^-1) and noninfected controls (185.4 ± 3.8 bpm) (100.6 ± 4.0 mL.beat-1) upon ANCOVA. There were no significant differences in peak Q̇t between groups. Conclusion: Peak a-vO₂ was diminished in subjects infected with HIV taking HAART compared with HIV-infected subjects not taking HAART and noninfected controls matched for age, gender, and physical activity level. Findings of the current study implicated HAART as a primary contributor to decreased muscle oxygen extraction-utilization in individuals infected with HIV.