ABSTRACT
A useful finding on simple respiratory function testing is that many subjects with hyperventilation syndrome experience considerable difficulty in performing simple tests in a reproducible manner. An experienced clinical physiologist may suspect the aetiology simply from the forced expiratory spirogram, which may show the consequences of incomplete and inconsistent efforts during the forced manoeuvre or during the preceding full inspiration (Fig. 26.1). Individuals with ‘sighing breathing’ have been reported to have a smaller VC and consequently larger RV than those with a more normal breathing pattern,6 but overall the results of spirometry, lung volumes and carbon monoxide diffusing capacity (DLCO) are within normal limits,4 provided that the subject is able to perform the tests adequately. Arterial PO2 is characteristically higher than normal due to the alveolar hyperventilation.
