Tidal breathing analysis as indicator of expiratory airway obstruction in

infants

ר אביגדור חברוני"ד

Methods used for evaluation of various lung

functions in Infants (Partial list)

Adult type infant pulmonary function tests Lung volumes, Flows, Resistance, Compliance

Airway occlusion techniques Resistance, Compliance

Multiple-breath helium dilution Lung volumes (FRC)

Multiple-breath inert gas washout Inhomogeneity of ventilation (LCI), FRC

Forced oscillation technique and impulse oscillometry Impedance, Resistance

Tidal Breathing analysis advantages

Easy and quick

Cheap

Portable

May not necessitate sedation

Can be used during normal sleep

Can be used in severe patients

Tidal Breathing analysis

Number of studies

Indicates airway obstruction (Morris 97, Seddon 96, Cornelis 96 )

Can demonstrate improvement after bronchodilators (Cornelis 96).

Can assess reaction to histamine provocation test (Cutrera ,

Cornelis 96).

Can be useful first tool in suggesting the site of the pathology in noisy breathing infants (Fillipone 2000)

Predictor of wheeze later in life (Håland 2005, Yuksel 96)

Conflicting results in assessing cystic fibrosis Pts (Ranganathan

2003, Williams 2000 )

Up to date, it is not routinely used in clinical practice

Tidal Breathing analysis

Limitation of some of the previous studies

Small series

Comparison of VT to resistance and other less direct. measurements (other than forced expiration).

Studies have been conducted in adults and children. (vs infants in the current study)

Awake state (less accurate)

Infants- dynamic FRC

The current study

Aim:

To evaluate the ability of tidal breathing loops to predict

expiratory airway obstruction in infants less than 2 years of

age.

Methods:

Retrospective analysis.

Comparison between parameters derived from tidal

breathing flow-volume & flow-time loops and V’maxFRC

(maximal flow at the functional residual capacity point).

Traditional Infant pulmonary function testing:

Flows measurements:

Tidal (Partial) Forced Expiratory Flow volume loop

• V’maxFRC

Non obstructed

curves

Flow- volume curves Flow -Time curves PEFVL

Moderate obstruction

Severe obstruction

Tidal Breathing – Loops patterns

Tidal Breathing – Expiratory phase

Three parts

Flow

TimeMorris & Lane 1981

II

Passive” "

III

abrupt

cessation

I

Peak flow

Tidal Breathing

Parameters suspected to indicate expiratory airway obstruction

tPTEF/tE

time to peak tidal expiratory flow (tPTEF)

divided by expiratory time (tE)

TEF50/PTEF, TEF75/PTEF

expiratory flow when 50% and 25% of tidal

volume remains in the lung divided by the

peak tidal flow

Tidal Breathing

tPTEF/tE is lower

TEF50/PTEF, TEF75/PTEF should be lower

• Obstruction -> Slower flows

• tE is longer

• Control of breathing

• reduced laryngeal braking

• earlier inspiratory muscles

relaxation

Definition: Severely obstructed infants

What is “ severely obstructed”?

• V’maxFRC<40% pred

• Tidal breathing limitation

No better discrimination

• According to V’maxFRC

• No clear definition

Study population

Infants aged 3 to 24 months who underwent iPFTbetween 2009-2012 because of recurrent or chronic wheezing or cough

Excluded

Infants born before 34w of gestation

Infants with any known severe chronic disease

Infants diagnosed with central airway disease

Pulmonary function were not done during acute state of illness

Study populationn=178

Mean SD

Age (months) 10.27 4.26

Sex (male) 66%

Weight (kg) 8.67 1.71

Height (cm) 71.02 5.88

Week of birth 39 2

Normal vs severely obstructed infants

𝐕maxFRC>80% pred 𝐕maxFRC<40% pred

N 54 57

Mean SD Mean SD P value

Clinical data

Age (months) 10.1 3.6 10.3 4.5 0.82

Sex (male) 65% 70%

Weight (kg) 8.3 1.4 9.1 1.9 0.01

Height (cm) 70.4 4.9 72.1 6.3 0.10

Week of birth 39.1 1.9 38.7 2.2 0.28

Tidal breathing

RR (min-1) 34.97 9.51 34.04 9.40 0.60

tI/tE 0.77 0.17 0.68 0.20 0.01

tPTEF (sec) 0.25 0.08 0.20 0.09 0.04

tE/tPTEF 0.27 0.07 0.18 0.05 0.0001

TEF50/PTEF 0.89 0.05 0.79 0.08 0.0001

TEF25/PTEF 0.67 0.09 0.52 0.11 0.0001

PTEF (ml/sec) 119.05 29.26 133.64 29.37 0.01

PTIF (ml/sec) 146.02 43.13 170.35 32.74 0.02

Normal vs Severely obstructed infantspattern of tidal breathing

PTEF

tPTEF

tE

PTIF

tI

Flow

Time

R=0.64

P<0.001

R=0.63

P<0.001

R=0.60

P<0.001

Tidal Breathing Parameters vs V’maxFRC Correlations

Can we identify confidently the severely obstructed infants?

• The severely obstructed infants will, probably, be

identified more clearly by tidal breathing loops than

others

𝐕maxFRC>40% pred 𝐕maxFRC <40% pred

N 121 57

Mean SD Mean SD P value

Clinical data

Age (months) 10.3 4.2 10.3 4.5 0.99

Sex (male) 64% 70%

Weight (kg) 8.5 1.6 9.1 1.9 0.01

Height (cm) 70.5 5.6 72.1 6.3 0.08

Week of birth 38.9 1.9 38.7 2.2 0.47

Tidal breathing

RR (min-1) 34.4 10.4 34.0 9.4 0.82

tI/tE 0.74 0.18 0.68 0.20 0.04

tPTEF (sec) 0.26 0.11 0.20 0.09 0.0122

tE/tPTEF 0.25 0.07 0.18 0.05 0.0001

TEF50/PTEF 0.88 0.06 0.79 0.08 0.0001

TEF25/PTEF 0.65 0.11 0.52 0.11 0.0001

PTEF (ml/sec) 119.40 30.19 133.64 29.37 0.0035

PTIF (ml/sec) 149.78 39.08 170.35 32.74 0.0126

TEF50/PTEF

AUC=0.801

TEF50/PTEF

tE/tPTEF

For TEF50/PTEF - AUC=0.801

For tE/tPTEF - AUC=0.787

tE/tPTEFTEF50/PTEF

0.266(0.067)0.891(0.050)Normal Value (SD)*

0.2240.870Cut-off value

-0.621-0.433Cut-off value

Z-score

81.5%81.5%Sensitivity

59.2%60.8%Specificity

87.7%88%Negative Predictive

Value

47.348.5%Positive predictive

Value

* VmaxFRC between 90-110 %predicted n-30

Summary

• Tidal breathing analysis is appealing way to measure airway obstruction in infants.

• There is a correlation between V’maxFRC and some parameters derived from tidal breathing loops.

• The correlation is probably not strong enough to permit tidal breathing analysis replace forced expiration methods.

• However, TEF50/PTEF and tE/tPTEF derived from tidal breathing flow-volume and flow-time loops can confidently discriminate between the severely obstructed infants and the others, and therefore can be used for this purpose.

רבה-תודה

493 results of VmaxFRC%predicted

Normal vs Severely obstructed infantspattern of tidal breathing

Flow

Time

tPTEF

tEtI

PTEF

PTIF

Non- obstructed

V'maxFRC>40% pred V'maxFRC<40% pred

N 118 56

Mean SD Mean SD P value

Clinical

Age (mo) 11.3 5.8 10.5 4.9 0.37

Sex (male) 63% 71% 0.286

Weight (kg) 8.6 1.7 9.0 1.9 0.13

Height (cm) 71.3 6.7 72.1 6.1 0.48

Week of birth 38.9 1.9 39.0 2.1 0.85

LFT

RR 33.6 10.4 34.5 9.8 0.59

tI/tE 0.73 0.18 0.68 0.19 0.11

tE/tPTEF 0.248 0.071 0.185 0.061 0.0001

Tef50/PTEF 0.87 0.06 0.80 0.09 0.0001

Tef25/PTEF 0.64 0.11 0.53 0.12 0.0001

tPTEF 0.26 0.11 0.20 0.09 0.0059

PTEF 120.63 32.09 132.78 29.94 0.0173

PTIF 149.78 39.08 170.35 32.74 0.0126