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The relationship between tPTEF:tE and specific airway conductance in infancy
C A Dezateux1, J Stocks, I Dundas
1Unit of Epidemiology and Biostatistics, Institute of Child Health, London, England.
Insights
Infant lung function, measured by expiratory flow timing and airway conductance, differs based on age and history of lower respiratory illness. These measures showed a weak association in older infants but not in younger healthy ones.
Area of Science:
- Pediatric Pulmonology
- Infant Respiratory Physiology
- Respiratory Mechanics
Background:
- Assessing infant lung function is crucial for early diagnosis of respiratory conditions.
- Tidal expiratory flow patterns and specific airway conductance (SGaw) are key indicators of airway health in infants.
- Previous research suggests potential differences in these parameters in infants with a history of lower respiratory illness (LRI).
Purpose of the Study:
- To investigate the association between the time to peak tidal expiratory flow (tPTEF:tE) and specific airways conductance (SGaw) in healthy infants and those with a history of wheezing-associated LRI.
- To compare these respiratory parameters in infants across different age groups and health statuses.
- To explore the relationship between tPTEF:tE, SGaw, and thoracic gas volume (FRCpleth) in infancy.
Main Methods:
- A study involving 168 infants (94 males) was conducted, with measurements taken on 220 occasions.
- The study compared tPTEF:tE and SGaw (measured at inspiration and end-expiration) in healthy infants and those with prior LRI.
- Infants were categorized into age groups: <3 months and >3 months, with comparisons made between healthy and LRI groups within these age strata.
Main Results:
- Mean tPTEF:tE was 0.321 in healthy infants <3 months old (n=73).
- Infants >3 months with prior LRI (n=79) exhibited significantly lower tPTEF:tE and end-expiratory SGaw compared to healthy infants of similar age (n=68).
- A significant but weak association between tPTEF:tE and end-expiratory SGaw was observed in infants >3 months, but not in healthy infants <3 months, who showed a weak association with FRCpleth.
Conclusions:
- The time to peak expiratory flow and specific airway conductance are significantly lower in older infants with a history of LRI compared to healthy peers.
- A weak association exists between expiratory flow timing and airway conductance in older infants, irrespective of wheezing history.
- Further research is required to fully understand the factors influencing tidal expiratory flow patterns in infants, particularly in relation to lung development and disease.
Abstract:
This study examines the association between the time taken to achieve peak tidal expiratory flow as a proportion of total expiratory time (tPTEF:tE) and specific airways conductance (SGaw) in healthy infants and those with prior physician diagnosed, associated, lower respiratory illness with wheezing (prior LRI) during the first year of life. We compared tPTEF:tE and SGaw, the latter estimated during both initial inspiration (ll) and end-expiration (EE), in 168 infants (94 males), measured on 220 occasions. Mean (range) tPTEF:tE was 0.321 (0.150-0.522) in 73 healthy infants aged less than 3 months (mean, 7.8 weeks), in whom mean (range) EE SGaw and plethysmographic thoracic gas volume at functional residual capacity (FRCpleth) were 2.47 s-1 kPa-1 (0.6-5.8) and 141 mL (87-204), respectively. Both tPTEF:tE and EE SGaw were significantly lower in older infants with prior LRI (n = 79; mean age, 50.0 weeks) compared to a similarly aged group of healthy infants (n = 68; mean age, 48.5 weeks), the mean difference [95% confidence intervals (CI)] being -0.039 (-0.013, -0.064) and -0.48 s-1 kPa-1 (-0.24, -0.72), respectively. A significant but weak association between tPTEF:tE and EE SGaw was found among infants above 3 months of age, irrespective of prior wheezing status. However, this relationship was not significant in healthy younger infants, in whom a significant but weak association with FRCpleth was found. Further work is needed to elucidate the factors influencing tidal expiratory flow patterns in infancy.