Effects of posture on lung function in obese children

Forced expiratory manoeuvres are recommended performed in sitting posture; however, standing posture has been reported to be usually more advantageous since any diaphragmatic restriction associated with obesity is reduced. Information on the effect of posture on forced expiratory manoeuvres in obese children is lacking.

To determine whether lung function measured in standing compared with sitting posture is increased in overweight and obese children.

One hundred fifteen overweight (n = 23) and obese (n = 92) children (7-17 years old) performed forced expiratory flow-volume manoeuvres in sitting and standing posture in random order.

Forced expiratory volume in 1 s (FEV(1) ), forced vital capacity (FVC) and forced expiratory flow after 50% of FVC (FEF(50) ) was significantly higher in sitting compared with standing posture [0.8, 1.1 and 2.2 percentage change in absolute values (all with P < 0.05)]. FEV(1) /FVC and peak expiratory flow were not significantly different measured in sitting and standing posture; 95%-99% of the variance were explained by differences among individuals (all with P < 0.0001).

In conclusion, FEV(1) , FVC and FEF(50) were all significantly higher when measured in sitting compared with standing posture; however, the improvements were of little clinical significance. These findings confirm that sitting posture is appropriate in obese children when performing forced expiratory flow-volume manoeuvres.