Lung function and ventilatory response during high-intensity treadmill walking in adults with cerebral palsy: a cross-sectional study.
Eivind Lundgaard, Hanna Kraggerud, Charlotta Hamre and 1 others
Adults with CP who walk have largely normal resting lung function, yet 40% report breathlessness as their main exercise limiter and 70% show reduced breathing reserve at maximal effort.
This is not a pulmonary pathology, and breathing reserve does not predict who feels breathless.
Key findings
1Resting lung function was largely within normal limits across all GMFCS levels, with about 90% of participants above the lower limit of normal for FVC, FEV1, and FEV%, and no statistically significant difference in these values between GMFCS groups.
2Seventy percent of participants had a breathing reserve below 20% at maximal exercise and 40% reported breathlessness as their main exercise limiter, yet the group reached predicted maximal heart rates, which the authors take to indicate no pathological exercise limitation.
3Breathing reserve did not discriminate between participants who experienced breathlessness and those who did not, and the correlation between breathing reserve and VO2 max was low and negative (r = –0.445), suggesting fitness level does not explain the degree of ventilatory limitation.
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What it does not show
Only 7 participants were in the GMFCS III group, so any group-level finding for that level is very uncertain and the authors themselves caution that the skewed distribution reduced statistical power. The sample was not random; participants who volunteer for fitness studies tend to be healthier and fitter than the broader CP population, so the findings may overestimate fitness and underestimate ventilatory limitation. No sample size calculation was performed for this sub-study. No arterial blood gas measurements (PaO2, PCO2) were taken, so exercise-induced hypoxaemia or hyperventilation could not be assessed. No lung diffusion capacity (DLCO) measurements were made, limiting the ability to evaluate gas-exchange impairment. The 10-minute rest between the submaximal and maximal tests may not have allowed full lactate clearance, particularly in the GMFCS III group, potentially inflating maximal lactate values. Cross-sectional design: all measurements were taken at one time point, so no causal or temporal conclusions can be drawn.
Declared interests
The authors declare no conflicts of interest. No funding source is named in the text provided.
The easy way to misread this
Do not read the 70% with a breathing reserve below 20% or the 40% who reported breathlessness as evidence of a pulmonary or cardiac pathology in cerebral palsy. The group reached predicted maximal heart rates (median 99%), the breathlessness rate is close to the 38% seen in a large sample of healthy Norwegian adults, and the authors explicitly state that no pathological exercise limitation was indicated. The wide range of breathing reserve values is also seen in healthy individuals, and the GMFCS III subgroup had only 7 participants, so group-level comparisons for that level are unreliable.
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