The value of blood lactate concentration (BLC) measured during incremental load tests in predicting maximal lactate-steady-state (MLSS) workload has rarely been investigated in children. In 17 children and 18 adults MLSS was 4.1 ± 0.9mmol 1.1. Workload at BLC of 3.0mmol 1.1 determined during an incremental load test explained about 80% of the variance (p < .001) and best predicted MLSS workload independent of age. This was despite the increase in power per time related to maximum incremental load test power being higher (p < .001) in children than in adults. The BLC response to given exercise intensities is faster in children without affecting MLSS.
Ralph Beneke, Hermann Heck, Helge Hebestreit and Renate M Leithäuser
Bernd E. Winkler, Kay Tetzlaff, Claus-Martin Muth, Klaus Paulat and Helge Hebestreit
The purpose of this study was to monitor heart rate (HR) and rhythm during open water SCUBA dives. Nine children performed 25-min open water SCUBA dives to 8 m depth. Before, during and after these dives, ECG was recorded. Compared with predive heart rate, heart rate declined by -24 ± 8% (range -36%; -15%) during the dive. In some children a further decline in HR was observed within the last minutes of the dive. Older and taller subjects and those with a high initial HR showed a more pronounced decline in HR. Furthermore singular supraventricular and ventricular extrasystoles were observed in some children. Immersion as well as facial and skin cooling presumably account for the initial decline in heart rate. A further drop in HR within the last minutes of the dive might be related to mild hypothermia. Single supraventricular and ventricular extrasystoles might occur in healthy children during dives.
Florian J. Segerer, Johannes Biko, Christoph Reiners, Clemens Wirth and Helge Hebestreit
Exercise-induced arterial hypoxemia (EIAH) has been reported in patients with juvenile thyroid cancer treated with radioiodine for lung metastases. This retrospective study tested the hypothesis that EIAH is due to ventilation-perfusion-mismatch in this rare pulmonary condition.
50 patients (age 13–23 years) treated for juvenile thyroid carcinoma and lung metastasis with 131I and 24 controls with thyroid cancer but without lung metastases and prior 131I-treatment were assessed in a state of acute hypothyroidism by com-puted tomography of the lungs, pulmonary function testing, cardiopulmonary exercise test with measurements of gas exchange, oxygen saturation, alveolar-arterial difference in pO2 (p(A-a)O2) and pCO2 (p(ET-a)CO2).
10 of the 50 patients with lung metastases showed EIAH. They had more pronounced pulmonary fibrosis on computed tomography, a widened p(A-a)O2, and p(ET-a)CO2, a lower DVE/DVCO2-slope, a lower respiratory rate and no increased dead space ventilation. A more pronounced EIAH was associated with male gender, younger age, lower diffusion capacity, higher p(ET-a)CO2 during exercise and a higher peak exercise tidal volume over vital capacity ratio.
EIAH in patients with thyroid carcinoma and pulmonary metastases is not related to ventilation-perfusion mismatch but to alveolar hypoventilation, possibly related to an increased work of breathing with pulmonary fibrosis.