Espen Spro Johansen

• Mentzoni, Fredrik; Skaugen, Martin; Eythorsdottir, Ingrid Eir Thorp; Roterud, Stian; Johansen, Espen Spro & Losnegard, Thomas Johansen (2024). Precision and accuracy of four handheld blood lactate analyzers across low to high exercise intensities. European Journal of Applied Physiology. ISSN 1439-6319. 124(12), p. 3781–3788. doi: 10.1007/s00421-024-05572-6. Full text in Research Archive Show summary

  Purpose: To evaluate the precision and accuracy in measured blood lactate concentrations among four commonly used handheld lactate analyzers compared to two stationary analyzers. Methods: Venous blood samples were taken at exercise intensities ranging from low to high. The blood lactate concentration was measured simultaneously with four pairs of handheld lactate analyzers (two new units of each brand: Lactate Plus, Lactate Pro2, Lactate Scout 4, and TaiDoc TD-4289), and compared with two stationary analyzers (Biosen C-Line and YSI Sport 1500). Measurements were repeated for a range of blood lactate concentrations (measured with Biosen) from 0.88 to 4.89 mM with a median difference between measurements of 0.10 mM. Results: The mean relative differences to the Biosen analyzer were − 7% (Plus), 7% (Pro), −10% (Scout), 42% (Tai), and − 32% (Ysi). The residual standard errors after linear regression against Biosen were 0.18 mM (Plus), 0.20 mM (Pro), 0.22 mM (Scout), 0.15 mM (Tai), and 0.06 mM (Ysi). Accordingly, a blood lactate concentration of 3 mM measured with Biosen yielded 95% prediction intervals that were 0.72 mM (Plus), 0.80 mM (Pro), 0.87 mM (Scout), 0.60 mM (Tai), and 0.23 mM (Ysi) wide. Conclusion: Compared to our two stationary analyzers, the precision of the four handheld lactate analyzers evaluated in this study was poor. Among the four, Tai was the most precise; however, this analyzer had low accuracy with a substantial mean difference to the reference analyzer.

• Skattebo, Øyvind; Johansen, Espen Spro; Capelli, Carlo & Hallén, Jostein (2021). Effects of 150- And 450-mL Acute Blood Losses on Maximal Oxygen Uptake and Exercise Capacity. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 53(8), p. 1729–1738. doi: 10.1249/MSS.0000000000002618. Full text in Research Archive Show summary

  Purpose: This study investigated whether maximal oxygen uptake (V˙O2max) and exercise capacity are affected by small acute blood loss (150 mL) and elucidated compensatory mechanisms. Methods: Thirteen male subjects (V˙O2max, 63 ± 9 mL·kg−1·min−1; mean ± SD) performed incremental exercise to exhaustion on a cycle ergometer in three experimental conditions: in euvolemia (control; blood volume [BV], 6.0 ± 0.7 L) and immediately after acute BV reductions of 150 mL (BVR150mL) and 450 mL (BVR450mL). Changes in plasma volume (PV) and BV during exercise were calculated from hematocrit, hemoglobin concentration, and hemoglobin mass (carbon monoxide rebreathing). Results: The reduction in V˙O2max per milliliter of BVR was 2.5-fold larger after BVR450mL compared with BVR150mL (−0.7 ± 0.3 vs −0.3 ± 0.6 mL·min−1·mL−1, P = 0.029). V˙O2max was not significantly changed after BVR150mL (−1% ± 2%, P = 0.124) but reduced by 7% ± 3% after BVR450mL (P < 0.001) compared with control. Peak power output only decreased after BVR450mL (P < 0.001). At maximal exercise, BV was restored after BVR150mL compared with control (−50 ± 185 mL, P = 0.375) attributed to PV restoration, which was, however, insufficient in restoring BV after BVR450mL (−281 ± 184 mL, P < 0.001). The peak heart rate tended to increase (3 ± 5 bpm, P = 0.062), whereas the O2 pulse (−2 ± 1 mL per beat, P < 0.001) and vastus lateralis tissue oxygenation index (−4% ± 8% points, P = 0.080) were reduced after BVR450mL, suggesting decreased stroke volume and increased leg O2 extraction. Conclusion: The deteriorations of V˙O2max and of maximal exercise capacity accelerate with the magnitude of acute blood loss, likely because of a rapid PV restoration sufficient to establish euvolemia after a small but not after a moderate blood loss.

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