PERIPHERAL CHEMORESPONSES OF INFANTS MEASURED BY A MINIMALLY INVASIVEMETHOD UTILIZING 2-BREATH ALTERNATIONS IN FI,O-2

The aim of this study was to develop a minimally invasive and reliable method for measuring peripheral chemoresponsiveness to oxygen in infa nts, and to establish baseline data from normal infants at 12 weeks of age. Two-breath alternations in fractional inspired oxygen (FI,O-2), switching between 0.42 to 0.00 were given for 2 min periods via a face mask (held close to the face but without contact) to 18 healthy infan ts during quiet sleep. End-tidal oxygen concentrations alternated betw een 21 and 11%, Instantaneous minute ventilation (V'E) and its compone nts tidal volume (VT), respiratory frequency (fR) inspiratory and expi ratory times (tI and tE), inspiratory flow (VT/tI), and inspiratory du ty cycle (tI/t tot) were measured by respiratory inductance plethysmog raphy. Two-breath alternations in each of the ventilatory components w ere matched with the corresponding alternating end-tidal oxygen record and compared with contiguous pre- and post-test data obtained in cont rol periods of air breathing. Alternations in all ventilatory componen ts except fR changed significantly during FI,O-2 alternations; VT 26%, tE -8%, VT/tI 18%, tI/t tot 11% and V'E 28% of baseline values. Withi n and between infant variances are reported for the individual compone nts of ventilation. Differences among infants were best detected by al ternations in V'E; within infant variance 76, between infant variance 171. We conclude that the test described is a safe, reliable and relat ively easily applied method of measuring peripheral chemoresponsivenes s, which is suitable for clinical application in infancy.