"Reactance inversion" at low frequencies in a child undergoing treatment of a cystic fibrosis exacerbation

Respiratory function in children with nephrotic syndrome: Comparative evaluation of impulse oscillometry and spirometry

AIM

To evaluate the respiratory functions of children with nephrotic syndrome (NS) by impulse oscillometry (IOS) and its correlation with spirometry.

METHODS

Fifty-five NS patients aged 3-18 years were included as the study group and 40 healthy children of the same age formed the control group. Patients were divided into nephrotic phase (first attack and relapse) and remission. Demographic, anthropometric, and laboratory data of the children were recorded. Respiratory functions were evaluated by IOS and spirometry. Children over 6-years old performed both IOS and spirometry while children under 6 years performed only IOS.

RESULTS

The R (R5%, R10%, R5-20), AX and Z5% values of IOS in patients with nephrotic phase were higher than remission patients and control group while spirometry indices of PEF% and MEF25-75% were lower. Z scores of MEF25-75 were significantly negatively correlated with z scores of R5, R10, Z5, and Fres while they were significantly positively correlated with z scores of X values (5, 10, 15, and 20 Hz). Z scores of forced expiratory volume in 1 /forced vital capacity significantly negatively correlated with z scores of R values (R5, R10), Z5 and AX and positively correlated with z scores of X values (X5, X10, X15 Hz).

CONCLUSION

Our study demonstrated that respiratory functions measured by IOS and spirometry were affected at the time of nephrotic phase in NS patients. IOS, a novel method easily applicable even in small children, is a potentially valuable tool to detect this condition; given its good correlation with spirometry.

"Reactance inversion" at low frequencies during lung function measurement by impulse oscillometry in children with persistent asthma. J Asthma 2021;59:1597-1603. [PMID: 34255601 DOI: 10.1080/02770903.2021.1955376]

BACKGROUND

Small airway dysfunction (SAD) in asthma can be measured by impulse oscillometry (IOS). Usually, the reactance should decrease with decreases in frequency oscillation. Sometimes an upward shift of the curve at low frequencies can be observed together with lower than expected reactance values. The actual value of the reactance at 5 Hz (X5) is calculated by the Sentry Suite application of the Jaeger Master screen iOS system™, providing the corrected X5 parameter (CX5). Our hypothesis is that correction of X5 is common in persistent asthma and it correlates better than X5 with the IOS parameters for evaluating SAD.

METHODS

In this transversal study, we evaluated 507 children (3-18 years old) using IOS-spirometry (Sentry Suite, Vyntus®). Resistance of all airways (R5), reactance area (AX), resonant frequency (Fres), X5, CX5, difference between R5 and R20 (D5-20), and spirometry parameters were analyzed. Reactance inversion and CX5 prevalence by age range was determined. The mean IOS-Spyrometry values in children with and without CX5 were compared, and correlations with each IOS-spirometry parameter in the age groups were performed.

RESULTS

CX5 was found in 83.5% of preschool children, 66.2% of schoolchildren, and 43.3% of adolescents (p < 0.001). The means of R5, AX, and D5-20 were significantly higher and FEV1 was significantly lower in children with CX5 (p < 0.05). In all ages, CX5 correlated better than X5 with IOS-spirometry parameters.

CONCLUSION

Reactance inversion and CX5 are frequent in asthmatic children, decrease with age, and correlate more closely than X5 with other IOS-spirometry parameters for evaluating SAD.