The measurement of airways resistance using the interrupter technique (Rint)

doi:10.1016/j.prrv.2005.09.011

Paediatric Respiratory Reviews

Volume 6, Issue 4, December 2005, Pages 273-277

https://doi.org/10.1016/j.prrv.2005.09.011 Get rights and content

Summary

The interrupter technique (Rint) is a quick, easy and effort-independent way to obtain indirect measurements of airways resistance in the preschool child. Results may be obtained using a portable Rint machine or a whole-body plethysmograph. Normative data are available and recent studies have improved standardisation of the methodology. Despite this, between-occasion results can be variable, particularly in children with wheeze. This limits the usefulness of the test in the assessment of long-term interventions such as the administration of inhaled steroids. The most useful role for Rint, therefore, appears to be in the assessment of bronchodilator responsiveness where it is as sensitive as spirometry in separating children with reversible airways disease from healthy controls. This paper describes the physiology of the interrupter technique and the methodology needed to obtain reliable results. Normal ranges are provided. The clinical applicability, repeatability, strengths and limitations of the technique are also discussed.

Section snippets

BACKGROUND

Although the measurement of airways resistance using the interrupter technique (Rint) was first described by Von Neergaard in 1927,¹ it is only in the last 10 years that portable, affordable equipment has facilitated its wider use as a research and clinical tool. As Rint is effort-independent, non-invasive and requires minimal subject co-operation, it is ideally placed for use in preschool children where traditional measurements of lung function may be unreliable or unachievable. Unfortunately,

WHAT DOES RINT MEASURE?

Direct measurements of airways resistance (Raw) are traditionally obtained using whole-body plethysmography. Here, changes in alveolar pressure, caused by breathing, are recorded as pressure changes within the sealed plethysmograph (P_alv) and Raw is calculated from the ratio between the change in P_alv and the airflow at the mouth. In contrast, rather than measuring alveolar pressure itself, the interrupter technique is based on the assumption that during transient occlusion of the airway at the

HOW IS RINT MEASURED?

Rint measurements may be obtained using plethysmography or portable equipment such as the MicroRint machine (Micro Medical Ltd, Rochester, Kent, UK; Fig. 2). As with traditional Raw measurements, plethysmographic methods require expiration against a transiently closed valve in a body box and may be difficult or impossible for some young children. Portable devices also require valve closure, but have the advantage that children need not sit in a body box, nor be separated from their parents.

EFFECT OF AGE AND SIZE ON SUCCESS RATES AND RINT MEASUREMENTS

Although Rint measurements from younger children tend to have a slightly higher coefficient of variation, repeatable results can be obtained from over 95% of Rint-naïve children aged 4 years or more and from a smaller percentage aged 2–3 years.4, 6, 12 These success rates may be improved with practice. Inter-observer variability is low and is influenced only marginally by the experience of the investigator.4, 5, 13

The patient characteristic most consistently correlated with Rint is height,

CLINICAL APPLICABILITY

As with any lung function test, Rint can be used both to obtain baseline data and to measure the effect of specific interventions. Not surprisingly, most of the paediatric literature has concentrated on its use in the assessment of children with cough, wheeze and asthma, with a smaller number of studies including children with cystic fibrosis. Although each centre should ideally produce its own normal ranges, a number of similar, but subtly different, reference equations are now available in

SUMMARY

Portable Rint machines provide a quick, simple and cost-effective alternative to plethysmographic measurements of airways resistance in children as young as 2 years. Normative data are available and recent studies have improved standardisation of the methodology. Unfortunately, due to the variability of the data obtained, single Rint measurements cannot reliably be used to separate children with normal and increased bronchial tone, nor is Rint helpful in the assessment of long-term

PRACTICE POINTS

•
Easy, cheap, non-invasive, effort-independent
•
Reproducible in children as young as 2–3 years
•
Helpful in assessing bronchodilator responsiveness
•
Limited applicability in assessing longer-term interventions

RESEARCH DIRECTIONS

•
Standardised methodology and reporting of results
•
Clinical studies of the role of Rint in the management of the preschool child with respiratory disease

References (26)

K. Von Neergaard et al.
Die messung des stromungswiderstandes in den atemwegen des menschen, inbesondere bei asthma and emphysema
Z Klein Med
(1927)
P.J. Chowienczyk et al.
A flow interruption device for measurement of airway resistance
Eur Respir J
(1991)
E.R. Carter et al.
Evaluation of the interrupter technique for the use of assessing airway obstruction in children
Pediatr Pulmonol
(1994)
P.D. Bridge et al.
Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting
Eur Respir J
(1999)
S.B. Phagoo et al.
Evaluation of a new interrupter device for measuring bronchial responsiveness and the response to bronchodilator in 3 year old children
Eur Respir J
(1996)
F. Child et al.
How should airways resistance be measured in young children: mask or mouthpiece?
Eur Respir J
(2001)
S.B. Phagoo et al.
Evaluation of the interrupter technique for measuring change in airway resistance in 5 year old asthmatic children
Pediatr Pulmonol
(1995)
S.B. Phagoo et al.
Comparison of four methods of assessing airflow resistance before and after induced airway narrowing in normal subjects
J Appl Physiol
(1995)
E. Lombardi et al.
Reference values of interrupter respiratory resistance in healthy preschool white children
Thorax
(2001)
P.D. Bridge et al.
Airway resistance measured by the interrupter technique: expiration or inspiration, mean or median?
Eur Respir J
(2001)

P.D. Sly et al.

Measurement of lung function in preschool children using the interrupter technique

Thorax

(2003)

B. Klug et al.

Specific airway resistance, interrupter resistance and respiratory impedance in healthy children aged 2-7 years

Pediatr Pulmonol

(1998)

S. Kannisto et al.

Interrupter technique for evaluation of exercise-induced bronchospasm in children

Pediatr Pulmonol

(1999)

Cited by (23)

Total specific airway resistance vs spirometry in asthma evaluation in children in a large real-life population
2015, Annals of Allergy, Asthma and Immunology
Citation Excerpt :
One study found that Rtot was more sensitive than FEV1, forced oscillation technique, and resistance by the interrupter technique in detecting bronchoconstriction in normal subjects.10 As described by Child,11 sRtot is an easy, cheap, noninvasive, and effort-independent measurement that is reproducible in children as young as 2 to 3 years old and is helpful in assessing bronchodilator responsiveness. Most recently, Beydon et al12 found that interrupter resistance had poor sensitivity to detect baseline obstruction but fairly good sensitivity and specificity to detect reversibility in schoolchildren with asthma.
Total specific airway resistance (sRtot) has been introduced as an alternative technique to assess lung function with a particular application to younger children with asthma.
To establish a diagnostic value of the body plethysmographic parameter (sRtot) in asthma diagnosis in young children.
This was a prospective, noninterventional study. Children 4 to 18 year old with symptoms suggestive of asthma were included (n = 885). Subjects underwent body plethysmography and spirometry (when capable) with reversibility tests. Of 788 subjects who could perform spirometry in addition to body plethysmography, 578 were diagnosed with asthma. Subjects with asthma were treated for minimum of 6 months and then their asthma was confirmed or refuted.
In 471 patients, asthma diagnosis was confirmed after 6 months of antiasthmatic treatment; 142 patients were 4 to 6 years old and 329 were 7 to 18 years old. Change in response to bronchodilator in children with asthma was significant for sRtot (P = .02) but not for forced expiration volume in 1 second (P = .21); sRtot was more sensitive and specific in identifying children with reversible obstruction than spirometry. There was a significant association between sRtot and asthma diagnosis in patients 4 to 6 years old (odds ratio 1.02, 95% confidence interval 1.01–1.03, P = .001); to differentiate subjects with asthma from those without asthma, the optimal cutoff point for sRtot was 174.5%. A sRtot value higher than 174.5% was associated with a positive prediction of an asthma diagnosis in patients 4 to 6 years old. A ratio of forced expiration volume in 1 second to forced vital capacity below 80% was not significantly associated with asthma.
These data support the recommendation of performing sRtot rather than spirometry in young children as a fairly sensitive marker of asthma.
www.ClinicalTrials.gov (NCT01805635).
Lung function testing in pre-school children
2010, Allergologia et Immunopathologia
Applied physiology: Lung function tests in children
2006, Current Paediatrics
Recent developments in the techniques available to measure lung function in children have greatly improved our understanding of lung development in both health and disease. In everyday clinical practice, lung function tests can provide objective information about the severity and progression of disease and the response to treatment. Although spirometry remains the most useful and widely used test, newer techniques, such as specific airways resistance and resistance measured by the interrupter technique, allow children who are too young to co-operate with spirometry to be tested. This is of great importance as it is increasingly recognized that many chronic respiratory illnesses in older children and adults have their origins in early life. This paper will describe the basic physiology of some standard tests and some of the newer tests that are increasing our understanding of lung disease in children.
Lung function in preschool children: Aplications in clinical and epidemiological research
2006, Paediatric Respiratory Reviews
During recent years there has been significant development of pulmonary function tests for use in preschool children. A range of tests including multiple inert gas washout, plethysmography, spirometry, interrupter resistance and impulse oscillometry have been shown to be feasible and to be able to identify diminished lung function in children with lung disease such as asthma or cystic fibrosis. An overview of these applications in clinical and epidemiological research is given. Future applications to investigate the longer term effect of preterm delivery, intra-uterine growth retardation, smoking and assessing the response to therapeutic intervention would strengthen the scientific basis for the prevention and treatment of respiratory disease in early life.
Introduction and overview of preschool lung function testing
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MINI-SYMPOSIUM: LUNG FUNCTION IN PRESCHOOL CHILDRENThe measurement of airways resistance using the interrupter technique (Rint)

Summary

Section snippets

BACKGROUND

WHAT DOES RINT MEASURE?

HOW IS RINT MEASURED?

EFFECT OF AGE AND SIZE ON SUCCESS RATES AND RINT MEASUREMENTS

CLINICAL APPLICABILITY

SUMMARY

PRACTICE POINTS

RESEARCH DIRECTIONS

Die messung des stromungswiderstandes in den atemwegen des menschen, inbesondere bei asthma and emphysema

Z Klein Med

A flow interruption device for measurement of airway resistance

Eur Respir J

Evaluation of the interrupter technique for the use of assessing airway obstruction in children

Pediatr Pulmonol

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

Eur Respir J

Evaluation of a new interrupter device for measuring bronchial responsiveness and the response to bronchodilator in 3 year old children

Eur Respir J

How should airways resistance be measured in young children: mask or mouthpiece?

Eur Respir J

Evaluation of the interrupter technique for measuring change in airway resistance in 5 year old asthmatic children

Pediatr Pulmonol

Comparison of four methods of assessing airflow resistance before and after induced airway narrowing in normal subjects

J Appl Physiol

Reference values of interrupter respiratory resistance in healthy preschool white children

Thorax

Airway resistance measured by the interrupter technique: expiration or inspiration, mean or median?

Eur Respir J

Measurement of lung function in preschool children using the interrupter technique

Thorax

Specific airway resistance, interrupter resistance and respiratory impedance in healthy children aged 2-7 years

Pediatr Pulmonol

Interrupter technique for evaluation of exercise-induced bronchospasm in children

Pediatr Pulmonol

MINI-SYMPOSIUM: LUNG FUNCTION IN PRESCHOOL CHILDREN
The measurement of airways resistance using the interrupter technique (Rint)