Preschool Lung Function: An Overview

1
Preschool Lung Function An Overview
UPDATE IN PAEDIATRIC RESPIRATORY MEDICINE 2006

• Janet Stocks
• UCL, Institute of Child Health, London

2

Prior experience?
3
Why use lung function tests at any age?

• To detect or exclude disorders
• To monitor clinical course
• To guide management
• To assess prognosis

4
Major conditions where LFTs may be helpful in
early life

• Asthma/wheezing
• Chronic lung disease of infancy (BPD)
• Cystic Fibrosis
• Investigating fetal origins of COPD
• Preterm delivery, IUGR, Maternal smoking in
  pregnancy etc

5
Why do we particularly need to assess airway
function in very young children?

• Insults to developing lung may have life long
  impact
• Critical time span when diseases such as CF may
  progress unnoticed
• Appropriate early intervention required before
  irreversible lung damage occurs
• Objective outcome measures required to monitor
  disease progression and efficacy of interventions

6
Evidence of loss of lung function by the time
conventional tests usually commence
Schaedel et al, Ped Pulm 200233483-491
7
Fetal origins of adult respiratory
disease? Identification of early insults
100 FEV1
Normal decline
Normal growth
Impaired growth
Symptoms
Death
0
Age (years)
8
Do pre-school wheezers have asthma?

• 40 of children wheezing during first 3 years
  of life are still
• wheezing at 6 years of life1

Prevalence of wheezing according to phenotype in
childhood
9
Is airway function assessed in very young
children?

• Despite this
• we hardly ever test lung function of young
  children
• we rarely use lung function tests in intervention
  studies in young children lt6y

10
Standardised measurements of lung function now
possible in infants
Stocks et al. Standards for infant respiratory
function testing ERJ 2000 - 2001 J Stocks in
Kendig's Disorders of the Respiratory Tract in
Children, 2006
11
The Real Challenge Preschool Children (2-6y)

• Too old to sedate
• Too young to co-operate
• Rapid lung growth
• Frequent respiratory symptoms

12
ATS /ERS Task ForceLung Function Testing in
Preschool Children

• Guidelines to be published in AJRCCM during 2006
  -2007

13
Height is an important determinant of airway
function
Collated data ICH, London, 2004
14
Accurate anthropometry essential

• Standardised Technique
• Regular calibration of stadiometer and scales

15
Gaining confidence and co-ordination
16
Suitable equipment/software?

• Generally similar to that for older subjects BUT
• need to check factors such as
• Linearity and Calibration range
• Apparatus deadspace
• Prediction equations
• Software and Quality Control issues different
  criteria for younger subjects
• Aurora et al AJRCCM 2004

17
Essential Background Information

• Age, weight and height at test (to at least 1
  d.p.)
• Sex and ethnic group
• Relevant current and past medical history and
  medication (inc prematurity, IUGR)
• Family history of asthma and atopy
• Cigarette smoke exposure (pre and postnatal)
• Allergen exposure (including pets)

18
Which tests are feasible in preschool children ?
Airway Function Spirometry
19
Respiratory Resistance
Interrupter Technique
Forced Oscillation
Specific Airway Resistance but not lung volumes
Plethysmography
20
Resting Lung Volume (FRC) and Ventilation
Inhomogeneity Multiple Breath inert gas Washout
(MBW)
21
How feasible are these tests?

• 40 children with CF (2-5y) and 37 healthy, age
  matched controls, mean age 4.3 (0.7) y
• Aurora et al AJRRCM 2005
• Multiple breath washout, plethysmography
  spirometry
• 30 in each group successfully completed ALL tests
  on 1st visit
• i.e. 75 CF 80 healthy
• May be lower success if tested under routine
  clinical /field conditions. Success rate rises
  with age of child and expertise of operator

22
Interpretation of results

• What is (ab)normal?
• Asthma UK lung growth charts
• What constitutes a significant change (including
  bronchial responsiveness)?
• Repeatability
• Clinical usefulness in individual vs research
  applications?

23
Can these tests discriminate between health and
disease during the preschool years?
24
Lung Clearance Index vs age in children with CF
and healthy controls Aurora et al Thorax 2004,
AJRCCM 2005, Resp Physiol Neuro 2005
? CF ? Healthy
25
Longitudinal measurements 0-6 years
CF Healthy Control
Kozlowska et al, ICH 2005
26
How repeatable are these tests?
27
MMEF z-scores after 6-12 month interval
Mean -1.30
Mean -1.93
Mean -0.45
Mean -0.23
Visits
1
1
2
2
CF
Healthy Controls
Kozlowska et al ICH
28
Repeated measures of LCI after 6-12 m interval in
PS children with and without CF
Mean 9.1
Mean 9.0
Mean 6.7
Mean 6.7
Visits
1
1
2
2
Healthy Controls
CF
Kozlowska et al ICH
29
Can they be used to assist prognosis?
Not been used for long enough tho some
promising preliminary results. Follow up of
London Collaborative CF study to school age will
address these issues
30
Summary

• Measurements of lung function in preschool-aged
  children are becoming increasingly feasible
• Potential to provide more scientific basis for
  detection, treatment and monitoring of lung
  disease in early life, and hence to decrease
  morbidity and improve lung health throughout life

31
Further work required to

• Standardise tests and equipment
• Determine between-occasion repeatability
• Establish appropriate reference values
• Understand the clinical utility of these tests
• in different diseases (asthma vs CF vs CLD)
• at different stages of disease
• at different ages
• in both cross sectional and longitudinal studies

32
Any Questions???