Assessment of lung volumes in children and adolescents: comparison of two plethysmographic techniques

Development of lung diffusion to adulthood following extremely preterm birth

Background

Gas exchange in extremely preterm (EP) infants must take place in fetal lungs. Childhood lung diffusing capacity of the lung for carbon monoxide (D_LCO) is reduced; however, longitudinal development has not been investigated. We describe the growth of D_LCO and its subcomponents to adulthood in EP compared with term-born subjects.

Methods

Two area-based cohorts born at gestational age ≤28 weeks or birthweight ≤1000 g in 1982–1985 (n=48) and 1991–1992 (n=35) were examined twice, at ages 18 and 25 years and 10 and 18 years, respectively, and compared with matched term-born controls. Single-breath D_LCO was measured at two oxygen pressures, with subcomponents (membrane diffusion (D_M) and pulmonary capillary blood volume (V_C)) calculated using the Roughton–Forster equation.

Results

Age-, sex- and height-standardised transfer coefficients for carbon monoxide (K_CO) and D_LCO were reduced in EP compared with term-born subjects, and remained so during puberty and early adulthood (p-values for all time-points and both cohorts ≤0.04), whereas alveolar volume (V_A) was similar. Development occurred in parallel to term-born controls, with no signs of pubertal catch-up growth nor decline at age 25 years (p-values for lack of parallelism within cohorts 0.99, 0.65, 0.71, 0.94 and 0.44 for z-D_LCO, z-V_A, z-K_CO, D_M and V_C, respectively). Split by membrane and blood volume components, findings were less clear; however, membrane diffusion seemed most affected.

Conclusions

Pulmonary diffusing capacity was reduced in EP compared with term-born subjects, and development from childhood to adulthood tracked in parallel to term-born subjects, with no signs of catch-up growth nor decline at age 25 years.

Pulmonary diffusing capacity following extremely preterm (EP) birth was reduced compared with term-born subjects. From mid-childhood to adulthood, development tracked in parallel in the EP and term-born groups, with preterms following lower trajectories.https://bit.ly/3ARPD7D

A new non-invasive method of infant spirometry demonstrates a level of repeatability that is comparable to traditional methods

AIM

The FloRight system provides novel non-invasive infant spirometry based on electromagnetic inductance plethysmography. We investigated the consistency of repeated measurements carried out in a Norwegian neonatal intensive care unit (NICU) using the system and how well these were tolerated.

METHODS

Tidal flow-volume loops were obtained from 10 preterm infants at discharge, 10 stable growing preterm infants weighing about 1500 g and 10 term-born infants. A nurse experienced with the system measured all patients before and after meals, and these measurements were repeated by nurses new to the system.

RESULTS

The measurements were well tolerated by the infants. The repeatability for the two parameters 'tidal volume' (Vt) and 'time to peak tidal expiratory flow to total expiratory time' (Tptef/Te) were relatively poor, similar to previous methods. However, the repeatability was good for the new 'flow-volume gravity mid-point' (FVg) parameter. Repeatability was better for term than preterm infants, when measurements were obtained by the experienced nurse and for measurements carried out before meals.

CONCLUSION

The FloRight system proved feasible in a NICU setting. The repeatability of the lung function measurements was similar to those reported for traditional infant spirometry. The nurse's experience and the relationship to meals appeared to be important.

[The role of lung volume measurements by plethysmography in the follow-up of asthma in children]

In asthmatic children, control of the disease is perfect when no symptoms occur and lung function is normal. The aim of this study is to analyse the role of plethysmography in the follow-up of asthmatic children. We present the results of a retrospective study of lung function (plethysmography and forced expiratory flow) in about 100 asthmatic children aged five to 16years. FEV1/FVC less than 80% predicted was considered as pathological (airflow obstruction). The ratio RV/TLC was considered pathological if greater than 30% and RV was considered pathological if greater than 120% (lung hyperinflation). Bronchodilator reversibility was performed in all patients. All patients were studied in a stable condition. None had developed any asthmatic exacerbations during the past month. We found a significant correlation between the residual volume/total lung capacity (RV/TLC) ratio and, on one hand: FEV1 (p<0.0001, R=-0.374), and on the other hand FEV1/FVC (p=0.07, R=-0.182) or forced expiratory flow 25-75 (p=0.03, R=-0.216). When comparing children with (n=40) and without (n=60) lung hyperinflation, we noticed more diurnal symptoms (30/40 vs 10/60, p=0.05), lower weight (33.9kg vs 41.8kg, p<0.05) and lower body mass index (16.9kg/m(2) vs 18.4kg/m(2), p<0.01). Among the children with defined airway obstruction, 49% also had lung hyperinflation. Twenty-three children had normal forced expiratory ratios but an increase of the ratio RV/TLC or of RV. When compared with children without lung hyperinflation, the age at diagnosis was significantly lower (3.9+/-1.9years vs 6.2+/-3.1years, p<0.01) and weight slightly lower (31+/-10kg vs 40+/-11kg, p=0.04). In conclusion, the use of plethysmography and thus the evaluation of pulmonary hyperinflation contributed to a better appreciation of the asthmatic phenotype in children.