Suitability of a new turbine spirometer for epidemiological surveys in children.

The performance of a new turbine spirometer, which has several advantages over equipment previously used to measure lung function, was compared with that of a conventional spirometer (Vitalograph) in a cross-over trial on 368 children six to 11 years old. On average, slightly higher values of forced expiratory volume at 0.75 s and forced vital capacity were recorded on the turbine spirometer. These differences occurred mainly in children aged less than eight years. Assuming the Vitalograph remained accurate, there appeared to be a slight tendency for readings on the turbine spirometer to drift downwards at a rate of 0.04 1 per 100 children measured but this was not statistically significant (p greater than 0.10). In conclusion, the machines differed mainly in the youngest age group. Until a recording of the complete expiration curve can be made using the turbine spirometer, it is not possible to assess whether this effect of age arose because of errors in the breath manoeuvre by younger children undetectable in the turbine spirometer or because the simpler design of the spirometer makes it easier than the Vitalograph for young children to use it correctly.