Reproducibility of Ultrasound Blood Flow Measurement of the Superior Mesenteric Artery Before and After Exercise

This study examines the reproducibility of gastro-intestinal blood flow measurements in the superior mesenteric artery (SMA) both before and immediately after exercise with Doppler ultrasound measurements. Twelve well-trained males (mean ± SD: age 25.9 ± 3.8 yr; VšO₂max 4.8 ± 0.9 l×min^--1) were measured twice (trial 1 and 2) with a 1 week interval before and immediately after 1hr cycling at 70 % VšO₂max. Duplex scanning was performed with the athletes in supine position immediately after transition from a chair (before exercise) or bicycle (after exercise). The variability of three measurements before exercise was studied within both trials (short-term reproducibility) and the mean pre-exercise values were compared between the trials (long-term reproducibility). In addition, post-exercise measurements were compared in the same way. Reproducibility was tested using the coefficient of variation and Cronbach’s α. Mean pre-exercise blood flow was 424 ± 66 ml/min (n = 12) in trial 1 and 375 ± 38 ml/min (n = 11) in trial 2. Immediately after exercise blood flow had decreased by 49 % to 214 ± 36 ml/min (p < 0.01) in trial 1 and by 38 % to 234 ± 36 ml/min (p < 0.01) in trial 2. Blood flow before and after exercise was not significantly different between trials (paired t-test) and therefore reproducible at the group level. Before exercise a good to fair reproducibility was observed both at the short-term (Cronbach's α: 0.88 in trial 1, 0.73 in trial 2, n = 11), and at the long-term (α = 0.80, n = 11). In contrast, long-term reproducibility immediately after exercise was poor (α = -0.99, n = 8 and α = 0.36, n = 7 after the first and second cycling period, respectively). In conclusion, duplex scanning of SMA after a sitting-supine transition in well-trained subjects is not a reproducible method at the individual level for intestinal blood flow measurements immediately after exercise.

Duplex scanning, intestinal blood flow, exercise, reproducibility.

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