Tidal breathing analysis Reliability and Clinical Relevance of Tidal Breathing Analysis
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Transcript of Tidal breathing analysis Reliability and Clinical Relevance of Tidal Breathing Analysis
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Knowledge and skills are very often out-of-date Misunderstanding in methodological potential, quality issues,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 ?