Abstract â–¡ 106

In preparation for investigations into maturation of respiratory control in infants by longitudinal measurements in the home, we performed a pilot study with the specific aim of demonstrating feasibility, by showing that (i) parents could be recruited to such a study, (ii) measurements could be made successfully in the home environment, and (iii) a sufficient number of successful repeat measurements could be made for meaningful analysis of data.

Methods: Parents were recruited by letter, followed by home visit for those who were interested. Five healthy term infants had serial measurements of respiratory control made in the home during sleep using the alternating breath test (ABT)(Thomas et al 1996 Eur.Resp.J.9:1261) Respiration was monitored by Respiratory Inductance Plethysmography and oxygen saturation by pulse oximetry, including beat-to-beat monitoring on the earlobe. After a 2-min baseline period of breathing room air delivered to a facemask held over the face, infants breathed alternately two breaths of 42% oxygen followed by two breaths 100% nitrogen. This was continued until at least 22 breaths had been recorded, after which the infant was returned to breathing air. The alternating breath test was analysed according to previously established methods.

Results: Forty-five letters were sent and 26 recruitment visits made. Eight families were ineligible and 10 more declined to participate. Eight infants were enrolled: 3 were later excluded because of illness or failure to sleep. Fifty recording sessions were attempted, and data were collected on 35 occasions. The median (range) number of tests per infant was 7 (3-10), and the age range was 37-128 days. All the indices relating to tidal volume (inspiratory, expiratory and mean tidal volume, inspiratory and expiratory drive, and instantaneous minute ventilation) showed an increase with age in response to the alternating breath test. There was strong evidence of a linear trend (p=0.03 for expiratory drive, p<0.001 for other indices). The indices relating to timing (inspiratory and expiratory time, duty cycle, and respiratory frequency) did not show overall changes with age, although there were marked differences between infants.

Conclusions: The feasibility of making longitudinal measurements of respiratory control in the home has been confirmed. Parents can be recruited to studies of this nature and sufficient data obtained for meaningful analysis. Respiratory indices relating to tidal volume show evidence of maturation over the age range studied.