Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting

Abstract

Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting. P.D. Bridge, S. Ranganathan, S.A. McKenzie. #ERS Journals Ltd 1999. ABSTRACT: This study describes the feasibility, repeatability, and interrater reliability of the measurement of airway resistance by the interrupter technique (Rint) in children 2±5 yrs of age, and examines whether reversibility to bronchodilator can be demonstrated in wheezy children.The mean of six Rint values was taken as a measurement. If subjects could complete one measurement and then a second 15 min after bronchodilator, baseline testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy children was measured after bronchodilator.Fifty-six per cent of 2±3-yr-olds (n=79), 81% of 3±4-yr-olds (n=104) and 95% of 4± 5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% completed reversibility testing. Baseline measurements were 0.47±2.56 kPa . Asthma is considered to reflect reversible airways disease. A precise definition his yet to be agreed. It is one of the few organic diseases where diagnosis and treatment are often made only on the parental reporting of symptoms [1], one of which is wheeze. Although there is an assumption that parents know what wheeze is, the history is sometimes vague and often there are no physical signs. In schoolchildren, reversibility of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) to bronchodilator treatment can be measured [2] so that, in cases where the history is not clear, objective measurements can be made. Changes in expiratory flow in infants in response to bronchodilator can be measured [3]. There are no readily available lung function tests suitable for children aged between 18 months and 5 yrs.The measurement of respiratory resistance in young and uncooperative subjects using the forced oscillation technique (FOT) and the interrupter technique (Rint) has been evaluated by several laboratories since the 1980s [4±7]. The simplicity of use for the patient and smaller size of the Rint device make it attractive for use in children aged 2±5 yrs in the ambulatory setting. Respiratory resistance is measured during quiet tidal breathing and requires minimal cooperation on the part of the subject.The theoretical background has been well described [5,6] along with the technical aspects in older children [7]. Although the technique has been tried in a small group of selected preschool children [6], very little has been published on the practicalities of using Rint in an ambulatory setting. In contrast to spirometry, only minimal comprehension and co-ordination are needed for Rint. This means that even acutely ill or tired children, of all ages, should be able to undertake the test successfully. There is no evidence that either bronchoco...

Airway resistance and atopy in preschool children with wheeze and cough

“…Baseline airways resistance by the interrupter technique and bronchodilator response testing Rint measurements were made as previously described [13] using a single commercial device (Microlab 4000; Micromedical Ltd, Gillingham, Kent, UK) throughout the study. Before each patient was tested, volume and flow were calibrated using a precision 1 L syringe (Vitalograph, Buckinghamshire, UK).…”

“…Until recently there has been no suitable lung function test for preschool children for ambulatory use [13]. Supposing bronchodilator response (BDR) to be one of the defining features of asthma, then if BDR could be demonstrated in children with a history of isolated cough or wheeze, then the prescribing of asthma treatment to such children could be better defended [14].…”

“…The theoretical background for measuring airways resistance using the interrupter technique (Rint) has been well described [17±20]. Using the technique, BDR testing has been undertaken in a small group of wheezy children [13]. Decrease in Rint following bronchodilator treatment could be demonstrated in most who were not wheezy at the time of the test.…”

Lung function measurement in prematurely born preschool children with and without chronic lung disease

“…10 Briefly, the MicroRint is a palmtop device with a software option to download data to a computer for further validation and analysis. Rint is derived from the ratio of the driving pressure (that is the alveolar-mouth pressure gradient) to the airflow at the mouth.…”

“…Resistance and conductance measurements obtained with interrupter technique in inspiration and expiration correlate with plethysmographic airway measurements. 9 Rint has been used to assess airways obstruction in preschool children with asthma 10,11 and cystic fibrosis. 12 The aim of this study was to investigate lung function using Rint, its feasibility by a clinician in the ambulatory setup and respiratory health in prematurely born children aged 2 to 4 years with and without CLD.…”