Respiratory muscle function in healthy school children from Kolkata, India

Aims Children in Eastern India suffer from high respiratory morbidity, and poorer lung function compared to Caucasian children. However, respiratory muscle strength has not been studied in this population. Our aim was to perform a cross-sectional study in healthy children in Eastern India to establish reference values for maximal inspiratory pressure (PImax), maximal expiratory pressure (PEmax) and sniff nasal inspiratory pressure (SNIP) and compare with established Caucasian standards. Methods Demographic, anthropometric and clinical information were collected from 408 children (age 6-12 years) attending primary schools in Kolkata in 2004-2005. The participants were not suffering from any acute illnesses at the time of the measurement of pulmonary function. The hand held respiratory pressure meter was used to measure the PEmax (maximum expiratory pressure), PImax (maximum inspiratory pressure) and the sniff nasal inspiratory pressure (SNIP). The Quantum II bioelectrical body composition analyser was used to directly measure the resistance and capacitative reactance. Results In boys the mean values were PEmax 65.3 ± 19.4 cm H2O, PImax 65.6 ± 21.2 cm H2O and SNIP 69.2 ± 25.2 cm H2O. In girls the mean values obtained: PEmax 60.6 ± 22.8 cm H2O, PImax 66.0 ± 24.0 cm H2O, SNIP 63.7 ± 24.8 cm H2O. These values were substantially (around 40%) below those reported for Caucasian children. In girls, the indices of respiratory muscle function showed significant correlation with height, body-mass index, mid-upper arm circumference, skin fold thickness, chest circumference, percentage of total body water and fat free mass. However, in boys all indices of respiratory muscle function correlated with weight and height only. Conclusions We derived reference values for respiratory muscle pressures for the first time in healthy Eastern Indian children. However, the values were found to be substantially lower than the healthy Caucasian children with a particularly strong influence of measures of nutrition in girls. It is thus important to investigate the role of diminished respiratory muscle strength in respiratory morbidity and poor quality-of-life in this population, as prevention of childhood lower respiratory tract infections such as tuberculosis, pneumonia in countries like India represents a global health priority.