Control of breathing in children with interstitial lung disease

Pulmonary function testing in children's interstitial lung disease

The use of pulmonary function tests (PFTs) has been widely described in airway diseases like asthma and cystic fibrosis, but for children's interstitial lung disease (chILD), which encompasses a broad spectrum of pathologies, the usefulness of PFTs is still undetermined, despite widespread use in adult interstitial lung disease. A literature review was initiated by the COST/Enter chILD working group aiming to describe published studies, to identify gaps in knowledge and to propose future research goals in regard to spirometry, whole-body plethysmography, infant and pre-school PFTs, measurement of diffusing capacity, multiple breath washout and cardiopulmonary exercise tests in chILD. The search revealed a limited number of papers published in the past three decades, of which the majority were descriptive and did not report pulmonary function as the main outcome.PFTs may be useful in different stages of management of children with suspected or confirmed chILD, but the chILD spectrum is diverse and includes a heterogeneous patient group in all ages. Research studies in well-defined patient cohorts are needed to establish which PFT and outcomes are most relevant for diagnosis, evaluation of disease severity and course, and monitoring individual conditions both for improvement in clinical care and as end-points in future randomised controlled trials.

[Rebreathing method for measuring CO transfer factor in children]

INTRODUCTION

The reference technique to measure the diffusing capacity of the lung for carbon monoxide (DLco) is the single-breath method (sb). For patients unable to perform this method, the rebreathing method (rb) can be used. However, the clinical relevance of DLCOrb has not been evaluated. The aim of this study was to assess the feasibility of the rb method in children seen in a clinical setting and its relationships with sb method.

SUBJECTS AND METHOD

We prospectively included children referred for 1) a suspected or confirmed interstitial lung disease (ILD group) (DLCOsb and DLCOrb measurements) ; 2) controlled asthma with normal lung function (DLCOrb measurements to derive DLCOrb/KCOrb expected values). DLCOrb was computed from the decrease in CO and Helium concentrations during tidal breathing in a rebreathing bag.

RESULTS

Data on DLCOrb measurements were available for 53 (91%) children in the ILD group and 48 (91%) control children (mean (range) 11.5 (4.3-18.2) and 9.5 (4-17) years ; respectively). In the ILD group, high or moderate correlations were found between raw DLCOrb and DLCOsb values (rhô=0.82 ; P<0.0001) and between KCOrb and KCOsb (rhô=0.62 ; P<0.0001), respectively. Results expressed as percentage predicted were moderately correlated (rhô=0.55 ; P=0.0003 for DLCO ; rhô=0.51 ; P=0.001 for KCO).

CONCLUSION

DLCOrb is easy to perform in children and gives values that are highly correlated to DCLOsb. Our preliminary results are in favour of a possible clinical use after further validation.

Pulmonary outcome in extremely low birth weight infants

OBJECTIVE

To determine whether infants with hyaline membrane disease (HMD) superimposed on immature lung disease (ILD) have more abnormal lung function and respiratory drive during the evolution of chronic neonatal lung disease (CNLD) in extremely low birth weight infants (ELBW; <1000 g).

METHODS

We measured lung mechanics (respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, and work of breathing per minute) and respiratory drive (airway opening pressure 100 milliseconds after initiation of breath [P(0.1)] and maximal inspiratory pressure generated during airway occlusion) on 3 occasions before term in 24 ELBW infants.

RESULTS

Ten infants with ILD (mean [95% CI] gestation: 24.3 weeks [23.1,25.4]; birth weight: 675 g [553,798]) were studied at 27, 31, and 35 weeks of postconceptional age and 14 infants with HMD superimposed on ILD (gestation: 25.1 weeks [24.4,25.9]; birth weight: 687 g [601,773]) were studied at 28, 32, and 35 weeks of postconceptional age. There were no statistically significant differences between the groups for respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, work of breathing per minute, P(0.1), and maximal inspiratory pressure generated during airway occlusion. With increasing age, both groups demonstrated increased respiratory drive as measured by P(0.1) without significant changes in respiratory frequency or CO(2). Work of breathing per minute increased in the HMD group with age and was higher in extubated subjects. A similar trend with age was demonstrated in ILD infants. Regardless of whether the initial lung disease was ILD alone or HMD + ILD, ELBW infants developed a mildly reduced lung compliance/kg (.8-1.1 mL/cm.H(2)O/kg) and high lung resistance (75-125 cm.H(2)O/L/second) pattern of CNLD, which changed little after 3 weeks of age. Survival to 6 months was 23/24 (96%). Oxygen dependency was 16/24 (67%) at 35 weeks, yet only 5/23 (22%) survivors required oxygen at discharge from the neonatal unit (43 weeks).

CONCLUSIONS

The visco-elastic and flow-resistive properties of the lungs in ELBW infants with CNLD remain only mildly abnormal, suggesting a more favorable prognosis for lung function in later years than previously reported.