Respiratory impedance and response to salbutamol in asthmatic Vietnamese children

Abstract

There is a high incidence of pediatric asthma in Vietnam, but little lung function data are available. The aim of the study was to compare respiratory resistance (Rrs), reactance (Xrs), and responses to salbutamol between asthmatic and healthy primary school children in Hanoi. Because respiratory mechanics vary along the breathing cycle, measurements were assessed separately in inspiration (Rrsi, Xrsi) and expiration (Rrse, Xrse).Inpatients with doctor-diagnosed asthma were measured 2-3 days following admission using the forced oscillation technique (FOT) at a single frequency (8 Hz). Z-scores and responses to salbutamol were compared between 102 asthmatics and 98 controls, and accuracy of group classification by FOT parameters was assessed by Youden index, an indicator to the proportion of subjects correctly classified in each group.In asthmatics versus controls, Rrsi-but not Rrse-was significantly larger and both Xrsi and Xrse were significantly more negative (P < 0.01). Both Rrs and Xrs responses to salbutamol were significantly larger in asthmatics than controls (P < 0.001). Youden indexes indicated response to salbutamol generally had better diagnostic values than Z-scores and was best discriminative first with Rrsi, then with Xrse.It is concluded that different FOT characteristics may be described in asthmatic and healthy Vietnamese children. The diagnostic value of each parameter depends upon the breathing cycle. Most useful in practice probably is the response to salbutamol measured by Rrsi.

Respiratory impedance and bronchodilator response in healthy Italian preschool children

“…Knowing the reference equation it is possible to detect abnormal lung function and, as previously mentioned, FOT can then be used in the follow-up of children with lung diseases such as asthma, neonatal chronic lung disease, or cystic fibrosis or asthma. 5,[7][8][9][13][14] The reference equations calculated from the healthy Italian children in the present study are very similar to those published by Hall et al 18 from Australian children Pediatric Pulmonology 18 to calculate Z-scores for Italian children and comparing them with Z-scores calculated using the Italian equations from the present study, no Pediatric Pulmonology Fig. 2.…”

“…The similarities in BDR despite the substantial difference in salbutamol dose show that 200 mg is sufficient for healthy children and likely reflects a relatively flat dose-response curve in such children. Other studies have reported similar changes in lung function following bronchodilatation measured with FOT in asthmatic children 13 or with different wheezing phenotypes. 14 In conclusion, the data from the present study give the reference equation for R rs and X rs for Italian children between 2 and 6 years of age.…”

“…[7][8][9] FOT has also been shown to be a valid tool in the assessment of bronchodilator response (BDR) in different populations of patients, especially asthmatic or wheezing children. 4,[10][11][12][13][14] Before FOT can be introduced into clinical practice as a routine test, appropriate reference values from healthy populations are needed. Although, a number of data sets from children have been published these are likely to be specific to the equipment used and to the study population.…”

Diagnostic accuracy of the bronchodilator response in children

“…5 This 12% criterion, which was recently reaffirmed in a large international study, 6 approximates the 95th percentile for percentage change in FEV 1 after bronchodilator administration in general population studies, which mainly consist of adults. 7 The forced oscillation technique, which provides information on airway resistance and reactance, has also been used to measure response to bronchodilators and to differentiate between asthmatic and nonasthmatic patients, 8,9 especially in younger children who are unable to cooperate during spirometric testing. However, this technique is not widely used because standardized guidelines are lacking.…”

Application of the Forced Oscillation Technique in Diagnosing and Monitoring of Asthma in Preschool Children

“…FOT makes it possible to distinguish children with asthma from healthy children by assessing the initial parameters of the FOT as well as the results of the assessment of reversibility of the airway obstruction test [7,[21][22][23][24].…”