Fourier analysis of infantile stridor: preliminary data.

Preliminary data from 3 patients suggest that computerized (Fourier) analysis of infantile stridor can be instructive. Several recordings are quickly collected with a microphone and digital oscilloscope at the patient's bedside. The data are later sent to a computer for spectral analysis. Averaging of several spectra from each patient depicts only those sounds that are consistent from sample to sample. Subtraction of background noise from the averaged stridor removes all but those sounds that are produced by the patient. The results show that the spectra are relatively consistent from sample to sample within the same patient, and that different patients with different pathologies have distinct patterns in their spectra. It thus appears that further acoustical studies of infantile stridor will be productive. We are optimistic that data from a larger series of patients will indicate those spectral patterns which are characteristic of a specific laryngotracheal pathology, and perhaps facilitate rapid diagnosis without invasive procedures. An additional potential of this analysis is that pre- and post-operative spectra can be subtracted to show those sounds that improved or worsened. Such serial comparisons during the management of airway problems could be useful in evaluating treatment.