Reduced vital capacity after methacholine challenge in early childhood--is it due to trapped air or loss of motivation

Comparison of slow and forced vital capacities on ability to predict survival in ALS

INTRODUCTION

Slow (SVC) and forced (FVC) vital capacities are the most used pulmonary function tests in amyotrophic lateral sclerosis (ALS). It is unknown if they equally predict survival in ALS. The aim of the present study was to compare both measures in predicting survival in this disease.

METHODS

Consecutive definite/probable ALS patients (2000-2014) in whom respiratory tests were performed at baseline and four months later were included. All patients were evaluated with the revised ALS functional rating scale (ALSFRS-R), respiratory (RofALSFRS-R), bulbar (ALSFRSb), upper and lower limb subscores, SVC, FVC, maximal inspiratory (MIP) and expiratory (MEP) pressures. King's functional staging system was applied retrospectively. Survival analysis was carried out by univariate Kaplan-Meier log-rank test. Multivariate Cox proportional hazards model determined significant independent variables.

RESULTS

We included 469 patients (270 males; mean onset age 61.0 ± 11.5 years; mean disease duration from first symptoms to first visit: 15.8 ± 16.1months; 329 spinal and 140 bulbar onset). FVC and SVC were strongly correlated (r² = 0.981, p < 0.001). Significant survival prognostic variables (Kaplan-Meier analyses) were onset region, age, disease duration, ALSFRS-R, ALSFRSb, RofALSFRS-R, ALSFRS-R decay, SVC, FVC, MIP, MEP and King's staging (p ≤ 0.01). Final Cox model including the significant variables showed similar results for FVC and SVC (p < 0.001). Moreover, 1% decrease in either predicted values increased death probability by 1.02.

CONCLUSION

FVC and SVC are inter-changeable in predicting survival in ALS.

Maximal flow at functional residual capacity in asthmatic preschool children

BACKGROUND

Many preschool children will perform correct peak-flow but will not exhale to residual volume, thus limiting the determination of airways obstruction. The maximal flow measured at function residual capacity (V'maxFRC) is independent of lung empting and could potentially serve as a parameter for describing flow at low lung volumes. The study determines the detection of airway obstruction/dilation in asthmatic preschool children by V'maxFRC, compared to FEV1 and FEF25-75.

METHODS

Children performed bronchial provocation test (BPT; n = 26) or received bronchodilators (Post-BD; n = 31). V'maxFRC was extracted at inspiratory capacity point of flow/volume maneuvers. The %change of V'maxFRC from baseline was compared with changes in various spirometry indices and to values obtained from our previously studied healthy control children.

RESULTS

FEV1, FEF25-75, and V'maxFRC decreased by 30.9 ± 12.2%, 46.2 ± 10.9%, and 36.6 ± 8.0%, respectively, while FRC increased by 37.0 ± 24.9% at end of the BPT. Post-BD spirometry values increased by 17.1 ± 16.1%, 47.0 ± 42.2, and 45 ± 24%, respectively (p < 0.0001). A positive response to bronchodilators was observed in 15/31 (48%) children by FEV1, in 22/31 (71%) children by V'maxFRC, and in 21/31 children by FEF25-75.

CONCLUSION

V'maxFRC detects airway obstruction/dilation in young asthmatic children similar to FEF25-75 and FEV1. V'maxFRC may be a valuable index in preschool children who cease exhalation prematurely. Digitally measured V'maxFRC should confirm the actual values in a wider age range in healthy and disease states.

Forced expiratory decay in asthmatic preschool children--is it adult type?

BACKGROUND

The forced expiratory decay in healthy preschool children portrays a convex shape that differs from the linear decay in the older healthy population. The "adult-type" expiratory decay during airway obstruction is concave. The study objective was to determine if the expiratory decay in young asthmatic children is "adult-type".

METHODS

Among 245 children (age 3-7 yrs), 178 had asthma (asthmatics) and 67 were non-asthmatic (controls). The expiratory flow decay was inspected by FEF25-75/FVC ratio (=1.0 when linear). Values were compared to those of our formerly studied (n = 108) healthy children. A meaningful obstruction in FEF25-75/FVC ratio was defined as 2-zScores from healthy. A meaningful response to bronchodilators was related to non-asthmatics.

RESULTS

In healthy subjects FEF25-75/FVC ratio declined with age from 1.73 ± 0.17 to 1.28 ± 0.11. Non-asthmatics portrayed ratio values similar to those of healthy subjects. In asthmatics, 118/178 displayed a convex to linear expiratory decay (FEF25-75/FVC = 1.33 ± 0.22). Sixty/178 asthmatics portrayed concavity (FEF25-75/FVC-0.79 ± 0.16) that appeared when FEF50 was 43.4 ± 12%healthy. Concavity appearance was also age-dependent (30.4% of 3-4 y old and 59.1% of 6-7 y). Vital-Capacity decreased in either decays, forming a visually petit curve. Most asthmatic children respond to bronchodilators by a meaningful elevation in FEF25-75/FVC values and by a visual change in the shape of the curve. Other common spirometry indices also increased meaningfully.

CONCLUSION

Most asthmatic preschool children portray convex to linear expiratory decay with diminished vital-capacity, resulting in a visually smaller than healthy curve, with seemingly normal expiratory decay. These curves may be misinterpreted as "normal" or as "no-cooperation" and may lead to misinterpretation. In response to bronchodilators, FEF25-75/FVC value increases in asthmatics and the curve changes from concave to linear or from linear to convex contour.

FRC measurements using body plethysmography in young children

BACKGROUND

Measurement of FRC in whole body plethysmography (FRCpleth) is not performed in young children (aged 3-5 years) because it involves sitting alone in a closed box and breathing attempts against occlusion.

OBJECTIVE

To assess the feasibility of measuring FRCpleth in young children.

METHODS AND RESULTS

Seventy-one of 102 children (age range 3.3-6.9 years) performed spirometry and FRCpleth measurements. Twenty-six children had controlled asthma (Group-A); 26 children were tested during asthma exacerbation had uncontrolled asthma (Group-UA), and 19 children were tested after receiving chemotherapy treatment (Group-C). Tests according to adult recommendations were first taught outside the plethysmograph and then performed with minor technical adaptations. Each test included two consecutive FRC measurements obtained during 2-3 sec of occlusion. Total lung capacity (TLC) and residual volume (RV) were calculated. Values were compared to FRC measured by Helium-dilution (FRC-He) in healthy preschool children and to extrapolated FRCpleth values of school children, and between the groups.

RESULTS

Group-A showed normal spirometry and normal TLC values, with mildly elevated FRCpleth and RV values (125 +/- 20 and 153 +/- 33 %predicted, respectively; P < 0.0001 for both values). Group-UA showed obstructed flows combined with high FRCpleth and RV (146 +/- 26 and 189 +/- 38 %predicted; P < 0.0001) and normal TLC. Group-C showed a restrictive spirometry pattern combined with lower than normal TLC (86 +/- 15 %predicted; P < 0.0251).

CONCLUSIONS

Measuring absolute lung volumes by plethysmography in young children is feasible and can detect abnormal lung volumes. It is essential to study a larger group of healthy children for reference values and to allow for standardization of the procedure.