Normative Data of Infant Pulmonary Function Testing: A Prospective Birth Cohort Study from India.

Objective: To develop a normal reference range of Infant pulmonary function test (IPFT) indices for Indian children.

Study Design: Prospective birth cohort study.

Setting: Division of Pediatric Pulmonology of a tertiary-care institute in India from August 2012 to March 2017.

Participants: All neonates born at the institute during the study period were screened for eligibility.

Measurement: IPFT at baseline and every 6-month until 36-months of age.

Main Outcome Measure(s): Tidal breathing flow-volume loop (TBFVL), Rapid thoracoabdominal compression (RTC), and Raised volume RTC (RVRTC) indices at baseline and follow-up.

Results: 310 newborns were enrolled in the cohort; 281 of them (169 male) had completed 36-months of follow-up at the end of the study period. There was no influence of gender on the baseline IPFT indices. Tidal volume per unit body weight (VT/kg) significantly increased from baseline to 36 months of age (P<0.001) while the peak ratio (tPTEF/tE) initially decreased in first 18-months of age (P<0.001), after that returned to the baseline value by 36 months of age. RTC indices did not change significantly from baseline values. In RVRTC, the ratio of forced expiratory volume in 0.5s to forced vital capacity (FEV0.5/FVC) was significantly decreased from baseline to 36 months of age (P=0.002).

Conclusions: Normal values for various IPFT indices for TBFVL, RTC, and RVRTC from neonates to the age of 36-month are provided. These data may be used as normative data for healthy neonates and children of Indian origin.