A94-10 Peak Expiratory Flow Characteristics and Regional Reference Standards in Children and Adolescents at High Altitudes Areas

Rationale Existing peak expiratory flow (PEF) prediction equations, primarily derived from low-altitude Chinese populations, may not be applicable to children and adolescents living at high altitudes areas due to chronic hypoxia and adaptive physiological changes. This study aimed to evaluate the validity of these equations and develop altitude-specific PEF reference standards. Methods A cross-sectional study was conducted among healthy students aged 7-17 years from 17 schools (altitude 3200-4500 m) between September and October 2024. PEF was measured using the COSMED Micro Quark spirometer. Measured values were compared with plain-region predictions. Age- and sex-specific percentile references were constructed using Generalized Additive Models for Location, Scale, and Shape (GAMLSS) with the Box-Cox Power Exponential (BCPE) distribution. Determinants were identified through sex-stratified BCPE models. Results Among the 4710 screened participants, 3443 (1574 males, 1869 females) met quality-control criteria. Plain-region equations systematically overestimated PEF, with a mean bias of + 1.0 L/s (95% limits of agreement: ±2.5 L/s). Overestimation was most pronounced in younger children (Fig 1). PEF increased with age in both sexes (p < 0.001), with males showing consistently higher values. Sex differences were modest before puberty (Cohen’s d = 0.21-0.61) and large thereafter (d ≥ 0.98). The BCPE distribution provided the best GAMLSS fit (Fig 2). Median PEF (P50) at age 12 was 4.24 L/s for males and 3.71 L/s for females; complete percentile tables (P1-P99) were established. In males, height (β = 0.033, p < 0.001) and weight (β = 0.024, p < 0.001) were positive determinants, whereas altitude was negatively associated (−0.20 L/s per 1000 m; β = −0.057, p < 0.001). In females, height and weight remained positive determinants, while age was inversely associated (β = −0.021, p = 0.004); altitude was not retained as a determinant(Table 1). Conclusions Plain-region PEF equations substantially overestimate the expiratory performance of children and adolescents in high-altitude areas. The newly established GAMLSS-based, altitude-specific reference standards provide robust normative data for respiratory assessment and public health applications in high-altitude populations. Authors’ Contributions: The first and second authors contributed equally to this work. The last author is the corresponding author.