BackgroundThe six-minute walk test (6MWT) is a simple, low tech, safe and well established, self-paced assessment tool to quantify functional exercise capacity in adults. The definition of normal 6MWT in children is especially demanding since not only parameters like height, weight and ethnical background influence the measurement, but may be as crucial as age and the developmental stage. The aim of this study is establishing reference values for the 6MWT in healthy children and adolescents in Switzerland and to investigate the influence of age, anthropometrics, heart rate, blood pressure and physical activity on the distance walked.MethodsChildren and adolescents between 5–17 years performed a 6MWT. Short questionnaire assessments about their health state and physical activities. anthropometrics and vitals were measured before and after a 6-minute walk test and were previously defined as secondary outcomes.ResultsAge, height, weight and the heart rate after the 6MWT all predicted the distance walked according to different regression models: age was the best single predictor and mostly influenced walk distance in younger age, anthropometrics were more important in adolescents and females. Heart rate after the 6MWT was an important distance predictor in addition to age and outreached anthropometrics in the majority of subgroups assessed.ConclusionsThe 6MWT in children and adolescents is feasible and practical. The 6MWT distance depends mainly on age; however, heart rate after the 6MWT, height and weight significantly add information and should be taken into account mainly in adolescents. Reference equations allow predicting 6-minute walk test distance and may help to better assess and compare outcomes in young patients with cardiovascular and respiratory diseases and are highly warranted for different populations.
Background: Nocturnal hypoxemia is important in precapillary pulmonary hypertension (pPH) as it worsens pulmonary hemodynamics. Whether daytime oxygen saturation (Spo2) predicts nocturnal hypoxemia in pPH patients has not been conclusively studied. Objectives: To investigate the prevalence of nocturnal hypoxemia in comparison to daytime Spo2 and disease severity in ambulatory patients with pulmonary hypertension. Methods: Consecutive patients diagnosed with pPH classified as either pulmonary arterial (PAH) or chronic thromboembolic pPH (CTEPH) had daytime resting and exercise Spo2 (at the end of a 6-min walk test); thereafter, they underwent overnight pulse oximetry at home. Functional class, pro-brain natriuretic peptide (pro-BNP) and the tricuspid pressure gradient were assessed. Results: Sixty-three patients [median (quartiles) age 62 (53; 71), 43 females] with PAH (n = 44) and CTEPH (n = 19) were included. The resting Spo2, exercise Spo2, and mean nocturnal Spo2 were 95% (92; 96), 88% (81; 95), and 89% (85; 92), respectively. Forty-nine patients (77%) spent >10% of the night with Spo2 <90% (desaturators), and 33 (52%) spent >50% of the night with Spo2 <90% (sustained desaturators). The positive predictive values of daytime Spo2 >90% for being a nocturnal nondesaturator or sustained nondesaturator were 25 and 53%, respectively. Nocturnal Spo2 was negatively correlated with the tricuspid pressure gradient, but not with functional class, 6-min walk test, or pro-BNP. Conclusions: Nocturnal hypoxemia is very common in PAH and CTEPH despite often normal daytime Spo2 and reflects disease severity. Nocturnal pulse oximetry should be considered in the routine evaluation of pPH patients and research should be directed toward the treatment of nocturnal desaturation in pPH.
In PH-patients but not in controls CTO decreased during exercise. Since CTO was an independent predictor of the work load achieved and the 6MWD cerebral hypoxia may contribute to exercise limitation in PH. Clinicaltrials.gov: NCT01463514.
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