Attenuated peripheral oxygen extraction and greater cardiac output in women with posttraumatic stress disorder during exercise

Abstract

Posttraumatic stress disorder (PTSD) is associated with an increased risk of developing cardiovascular disease, especially in women. Evidence indicates that men with PTSD exhibit lower maximal oxygen uptake (V̇o_2max) relative to controls; however, whether V̇o_2max is blunted in women with PTSD remains unknown. Furthermore, it is unclear what determinants (i.e., central and/or peripheral) of V̇o_2max are impacted by PTSD. Therefore, we evaluated the central (i.e., cardiac output; Q̇_c) and peripheral (i.e., arteriovenous oxygen difference) determinants of V̇o_2max in women with PTSD; hypothesizing that V̇o_2max would be lower in women with PTSD compared with women without PTSD (controls), primarily due to smaller increases in stroke volume (SV), and therefore Q̇_c. Oxygen uptake (V̇o₂), heart rate (HR), Q̇_c, SV, and arteriovenous oxygen difference were measured in women with PTSD (n = 14; mean [SD]: 43 [11] yr,) and controls (n = 17; 45 [11] yr) at rest, and during an incremental maximal treadmill exercise test, and the Q̇_c/V̇o₂ slope was calculated. V̇o_2max was not different between women with and without PTSD (24.3 [5.6] vs. 26.4 [5.0] mL/kg/min; P = 0.265). However, women with PTSD had higher Q̇_c [P = 0.002; primarily due to greater SV (P = 0.069), not HR (P = 0.285)], and lower arteriovenous oxygen difference (P = 0.002) throughout exercise compared with controls. Furthermore, the Q̇_c/V̇o₂ slope was steeper in women with PTSD relative to controls (6.6 [1.4] vs. 5.7 [1.0] AU; P = 0.033). Following maximal exercise, women with PTSD exhibited slower HR recovery than controls (P = 0.046). Thus, despite attenuated peripheral oxygen extraction, V̇o_2max is not reduced in women with PTSD, likely due to larger increases in Q̇_c.NEW & NOTEWORTHY The current study indicates that V̇o_2max is not different between women with and without PTSD; however, women with PTSD exhibit blunted peripheral extraction of oxygen, thus requiring an increase in Q̇_c to meet metabolic demand during exercise. Furthermore, following exercise, women with PTSD demonstrate impaired autonomic cardiovascular control relative to sedentary controls. We interpret these data to indicate that women with PTSD demonstrate aberrant cardiovascular responses during and immediately following fatiguing exercise.

Keywords: PTSD; V̇o2max; arteriovenous oxygen difference; heart rate recovery; physical activity.