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Pulmonary function measures in healthy infants. Variability and size correction
J P Hanrahan1, I B Tager, R G Castile
1Channing Laboratory, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Insights
Pulmonary function (PF) in infants shows high variability, especially in early life. Sex differences in PF are not significant, but length is a reliable measure for size correction in healthy infants.
Area of Science:
- Pediatric Pulmonology
- Infant Physiology
- Respiratory Mechanics
Background:
- Pulmonary function (PF) assessment in infants is crucial for diagnosing respiratory conditions.
- Understanding normal PF development and variability in healthy infants is essential for accurate interpretation.
Purpose of the Study:
- To examine sex differences and variability in pulmonary function measures in healthy infants.
- To determine the relationship between somatic size and PF parameters in early life.
Main Methods:
- 151 pulmonary function tests were performed on 72 healthy infants (<2 years old) using partial expiratory flow volume (PEFV) maneuvers and helium dilution for FRC.
- Infants were stratified by postconception (PC) age, and PF measures were analyzed for variability and sex differences.
- Linear regression was used to assess the relationship between PF parameters and somatic size (length, weight, chest circumference).
Main Results:
- No significant sex differences in PF were observed, even after controlling for somatic size.
- Flow measures exhibited greater between-subject and within-subject variability than volume measures, particularly in younger infants (<50 PC weeks).
- All PF measures showed a linear relationship with somatic size; length provided the best size correction.
Conclusions:
- Infant pulmonary function measures are most variable in early infancy.
- Forced expiratory flow measures are more variable than volume measures.
- Length is linearly related to PF and offers reasonable size correction for healthy infants up to 18 months of age.
Abstract:
We conducted 151 tests of pulmonary function (PF) on 72 healthy infants younger than 2 yr of age using partial expiratory flow volume (PEFV) maneuvers and helium dilution determination of FRC. After tests were grouped into four strata based on postconception (PC) age, variability and sex differences in level of PF were examined. No significant sex differences were found for any PF measure in any age stratum, even when somatic size was controlled by length correction. Force expiratory flow measures, however, tended to be greater in girls than in boys in the youngest infants. Flow measures demonstrated greater between-subject variability than did volumes, and variability was greatest in the youngest infants. Within-subject variability also was more pronounced for flow measures, particularly in infants younger than 50 PC wk of age. Across the age range of infants studied, all PF measures were related linearly to somatic size as measured by either length, weight, or chest circumference. Length offered the best individual size correction of the three size parameters studied. Linear regression of PF parameters versus length demonstrated FRC to increase at 5.39 ml/cm over this age range, whereas flow at FRC increased by 9.67 ml/s/cm. We conclude that the variability of infant PF measures is greatest in early infancy, that measures of forced expiratory flow are more variable than volume measures, and that sex differences in infant PF do not appear significant. Length is related linearly to PF measures and offers reasonable size correction for healthy infants younger than 18 months of age.