Tidal breathing analysis

Reliability and Clinical Relevance of Tidal Breathing Analysis

H.J. SmithProduct Manager Pneumonology

Respiratory Care

Turkish Thoracic Society 2014

Workshop tidal breathing analysis

Forced spirometry Education and training in all levels on all issues

European spirometry driving licence

Everlasting problems Quality of spirometry and test results will ever depend on efforts of

patients and medical stuff Interpretation of flow limitation needs expertise of physician

Tidal breathing analysis Little offers for specific training or education

Knowledge and skills are very often out-of-date Misunderstanding in methodological potential, quality issues,

relevance of test results Promoted mostly by paediatricians

Why not in combination with spirometry?

Introduction “Pro” tidal breathing analysis

Tidal breathing lung function testing Physiologic Usual way of breathing Effort independent (all subjects can be measured – from

infants to elderly and severe diseased) Maximal manoeuvres are limited in describing tidal

breathing conditions

Of interest in diagnostics of the lung Differentiated, informative, sensitive Direct measurements of specific characteristics of the

respiratory system

Spirometry tidal breathing analysis

Mostly in infant lung function testing Flow-volume pattern Flow-time pattern Rather often adaptation of interpretation strategies from

adults

V.P. Seppä et al. Tidal breathing flow measurements in awake young children by using impedance pneumotachography. J ApplPhysiol. 2013; 115: 1725-1731

Tidal breathing analysis in practice (adults)

Adult subject (a)Normal / obstructive ?

Adult subject (b)Normal / obstructive ?

Tidal breathing in spirometry

Subject (a)Emphysema

Subject (b)Healthy

“Contra” tidal breathing analysis

Variability Freedom of the subject to breath slower, faster, deeper or

more shallow

No standards for achieving reproducibility In the past: Metronome; BF=constant

Sensitivity and specificity of flow pattern Nearly all respiratory problems lead to flow limitation

Only severe degrees of disability become visible

Usually more complex technology needed

Specific quality, best selection and classification concepts

Specific methods for (clinical) evaluation

Problems: Standardisation of breathing Intra-breath variability Limitations not yet visible at

tidal breathing Flow-volume pattern ambiguous

Solutions: Statistical methods for

evaluation Long term recording Individual trend analysis Pre-post assessment

Intra-breath variability of 2 flow-volume-parameters: Tpef%Tex Vpef%Vex

Still the flow-volume recording of tidal breathing lacks information!

Survay of methods (applications)

Flow (volume) in combination with one ore more additional signals (simultaneous recording)

Rint, Rocc Occlusion pressure - Pint/Pocc sRaw, Bodyplethysmography - Vshift R5, X5, Oscillometry - Pmouth (ext. generator) P0.1 Breathing pump - Pint/Pocc FRCHe, FRC-Rebreathing - %He Cdyn, Compliance - Poes CO2/O2, Capnography/Oxymetry - %CO2/O2

RAAR, Rhinomanometry - Pchoanae Wheezing, Lung sound analysis - Sound Zimp, Impedance tomography - Impedance

FRC-stability (EEL)

Common long term stability of flow channel > 5 min Offset of flow transducer stays within “dead zone” New, high stable and temperature compensated pressure transducers

Volume drift upwards

Volume drift downwards

Physiologic criteria for FRC-stability Regularity of breathing BF constant VT constant

FRC-stability line

Sources of drift

Drift of volume is an technical issue – ATP-BTPS correction It is not possible to eliminate this drift In future statistical methods

Volume drift

Sources of drift Approximation of ATP-BTPS correction Correction depends / varies with:

Changes in ATP Use of filters Breathing pattern (flow profile) Ratio of dead space / alveolar

ventilation Adaptation of Patient Calibration

SolutionPost processing Depending on

measurement application Applied on specific

breaths or entire recording Excludes physiological

changes of EEL

Visual inspection of adaptation

Offset correction

Repeatability (within trial / between tests)

Standardisation ? Patient has all degrees of freedom to increase, lower VT, BF What is the standard?

In the past Standardization of BF – Metronome Need of corrective action of patient Shift of FRC

Nowadays Non-restricted spontaneous breathing is requested

Confirmation of normal resting breathing The point of lowest WOB is highly reproducible

Respiratory system always tries to minimise WOB Regulation / optimisation of BF and VT

Obstruction BF i, VT h Restriction BF h, VT i

Decreasing variability of measurement

Edit capabilities Selection, deselection Manual corrections

Result c Subjective influence increases variability of results

Reliable concepts to improve quality

Adaptation phase until regular tidal breathing Familiarisation with mouth breathing through instrument

Instruction/confirmation of spontaneous breathing

(at individual lowest WOB)

In case of insufficient cooperation Increase of number of breathing cycles Increase of number of trials Repeated recording after optimised instruction Rejection of artefact affected trials

Editing artefact effected trials is not recommended !

BEST selection in tidal breathing analysi

Maximum / Minimum Not applicable in tidal breathing analysis

Median (usually) Arranging all the observations from lowest value to highest value

and picking the middle one Advantage: Robust against artefacts Disadvantage: BEST as good as single trial

Average Sum of a list of numbers divided by the size of the list Advantage: Improves with number of trials

BEST is better than a single trial Disadvantage: Strongly effected by artefacts Use requires prior artefact rejection

Comparison of median – mean calculation

Low variability of sReff (Reff, TGV) and FRCMedian = mean

Full body plethysmography

Characteristic and clinical usefulness / interpretation of breathing (resistance) loops.

DVthorax = DVmouth

No compression / decompression of air in lungs. Movement of thorax is NOT detected by box!

Breathing loop without Raw

2

1

0

-1

-2

-40 -20 0 20 40

Flow

Shift volumeShift volume [mL]

TGVDVth

DVm

0

Flow [L.s-1]

No Shift volume!

sReff

0

Shift volume = proportional to Raw

Breathing loop with Raw >>

DVm

DVth

+PA+

Raw>>

Compression /decompression

Alveolar pressure >>

Flow

Shift volume

0

0

sReffsReffFraction

Raw

Flow [L.s-1]

Sift volume [mL]

Breathing loop with Raw >> & TGV

TGVDVth

DVm

+PA+

Raw>>

Compress. /decompress.

Alveolar pressure >>

Flow

Shift volume

0

0

sReff

FractionsRaw TGV

Flow [L.s-1]

Sift volume [mL]

Shift volume = further increased by TGVAlveolar pressure = constant!

Summary - breathing loop

Specific resistance (sRaw) incorporates (Raw, TGV)

-4 0 -2 0 0 2 0 4 0

2

1

0

-1

-2 Shift volume [mL]

Flow [L.s-1]

sRtot

sReff

Parameters

sRaw breathing loop Specific Resistance Related to WOB, efforts for breathing

Without shutter measurement! Proportional to Raw and TGV Not a resistance loop!

(Alveolar pressure ~ Raw only)

Pecularities of the sRaw breathing loop Low variability as primary measure High clinical relevance / significance Answer on relevant clinical questions: abnormality, local distribution,

reversibility, hyperresponsiveness

Centralairways

R ~ 80%

Peripheral airways

R < 20%

TGV > 60 %

Larynx

Trachea

Bronchi

Bronchioles

Alveolar Ducts

Alveoli

Cross sectional area [cm²]

2.5

2.0

5.0

1.8 x 10²

9.4 x 10²

5.8 x 10³

56 000 000

Resistance[kPa/(L/s)]

0.05

0.05

0.02

Genera-tion

8-10

17

24

Weibel, Morphometry of the Human Lung, Springer 1963

Weibel: Morphometry of the human lung

Raw-TGV dependency

Raw high & TGV low Raw low & TGV high

Raw >

TGV <

Raw <

TGV >

Specific Resistance (sRaw) Normalises airways resistance to lung volume Low dependence on biometrical data Reference values are constant

= sRaw =

Clinical information based on sRaw

Threshold to abnormal lung function Adults sRaw > 1.2 kPa.s (Raw & TGV) Children sRaw > 1.0 kPa.s (Raw & TGV)

Reversibility No…………No significant change of sRaw Partial…….Significant decrease of sRaw Complete….sRaw becomes normal

Hyperresponsiveness PD/C+100sRaw & > 2.0 kPa.s PD/C-40sGaw & < 0.5 kPa-1.s-1

Important clinical questions are answered based on tidal breathing! Incorporating the entire respiratory tract.

Shift volume [mL]

Flow V‘ [L.s-1]

sReffApproximation

ReffTGV

Clockwise turn

Differential diagnsotics via sRaw- loop

Degree of opening, separately for in- and expirationK1 closed, steep c Normal lung functionK2 little opened, clockwise turned c Central obstructionK3 Golf club c Peripheral end-expiratory inhomogeneityK4 V-shape c Elevated diaphragm and/or end-expiratory „closing“K5 Markable S-shape c Extra thoracic stenosis

Impulse Oscillometry

New multiple trial concept.

Tidal breathing analysis

Spontaneous breathing pattern Physiologic, effortless, patient friendly

No age limitation Highly reproducible (Point of lowest WOB) Variety of different methods available

Global information (sReff) Highly differentiated (Raw, FRC; R5, X5)

New concepts for artefact elimination Median >> automated artefact rejection

and mean calculation

Tidal breathing analysis Questions ?