ANALYSIS OF TIDAL BREATHING PARAMETERS IN INFANCY - HOW VARIABLE IS TPTEF-TE

During recent years there has been increasing interest in the measurem ent of tidal breathing parameters, such as the time to reach peak tida l expiratory flow as a proportion of total expiratory time (TPTEF:TE), and their application to population-based studies of the determinants of early respiratory morbidity. However, little is known about factor s influencing the within and between-subject variability of these para meters. This study examines the influence of sedation of TPTEF:TE, est imates the optimal number of breaths and breath epochs required to mea sure TPTEF:TE, and assesses short-term repeatability of this parameter during the first year of life, taking account of age-related differen ces. Measurements were made in 266 healthy infants and young children (1 d to 19 mo old). Mean (SD) TPTEF:TE fell from 0.49 (0.11) in the fi rst 2 wk of life to 0.34 (0.09) by 5 to 8 wk, remaining similar therea fter. Sedation with triclofos sodium (75 mg/kg) had no significant eff ect on TPTEF:TE, which was 0.33 (0.10) in 23 unsedated 6-wk-old infant s and 0.32 (0.08) in 49 sedated infants of similar age and weight (95% Cl for the difference: -0.05, 0.04). At least 10 breaths in each of t wo separate epochs from each infant were required to provide a represe ntative estimate of TPTEF:TE. The mean (SD) difference between repeat measurements made 5 to 108 min apart was 0.02 (0.08) in 34 infants you nger than 6 wk of age (95% limits of agreement: -0.15, 0.18) and -0.01 (0.04) (95% limits of agreement -0.09, 0.08) in 30 infants 6 wk and o lder. The wider within-subject variability observed shortly after birt h may limit the clinical and epidemiologic applications of TPTEF:TE wh en measured during the first weeks of life.