CICM FOT Theories and Reports interpretation slides (1) (1).pptx 5112023.pptx

OSCILLOMETRY
THE PHYSIOLOGY & INTERPRETATION
AND ILLUSTRATIVE CASES
BY
DR . ANIMESH ARYA
SENIOR CONSULTANT CHEST PHYSICIAN
SHRI BALAJI MEDICAL INSTITUTE PASCHIM VIHAR NEW DELHI
&
ASRA CENTRE FOR CHEST DISEASES, ALLERGY AND SLEEP DISORDERS
NEW DELHI

WHY WE DO LUNG FUNCTION TEST ?
We get to know about Lung Mechanics , volumes ,flows etc .
Helps establishing a correct diagnosis besides monitoring patient lung-
health over time
It should accurately assess the respiratory system, be reproducible with
minimum variation between measures, and be sensitive enough to detect
lung status changes over time and predict relevant therapy outcomes.
Should be effortless & quick.
The technique should be easy to use on a wide range of patients, including
young children, older people, and people with disabilities.
The measurements should also provide the clinician with a clear
understanding of what part of the respiratory system is affected.

SO HOW TODAY’S STANDARD - SPIROMETRY, LIVES UP TO THESE
PREREQUISITES…???
Spirometry is difficult to perform IN individuals such as preschool children, handicaps and also
many elderly and dyspnoeic patients.
Requires cooperation having to perform a forced exhalation from total lung capacity down to
residual volume
The test is effort dependent and the patient needs to be coached by an experienced technician to
guarantee an acceptable maneuver; however, up to 20% of patients cannot perform an acceptable
measurement. 40% measurements are not acceptable.
Spirometry takes a relatively long time to perform - up to 20minutes
Spirometry is not sensitive to alterations in the small airways
There are at least 29 contraindications to spirometry due to the high pressures that result when
forcibly exhaling, potentially causing injury, the risk of spreading infection from contagious patients,
and inability to participate for some patient populations like dementia where COPD can be common.
Aerosol Generating Procedure - contraindicated in CoVid Pandemic.

SMALL AIRWAYS
The small airways are frequently
involved early in the course of [lung]
diseases, with significant pathologies
often demonstrable before the onset of
symptoms or changes in spirometry or
imaging.
McNulty & Usmani, ECRJ 2014
Unlocking
“Silent
Zone”
Oscillometry
. In COPD, we call those small airways ‘quiet’ or ‘silent’ – not because they actually are, but
because our listening tools haven’t been that sensitive to pick up the noisy disease of COPD

Lipworth et al Lancet RM 2014 ;2:497-506
Small airways in asthma: “the quiet zone”

SMALL AIRWAYS DISEASE
The diagnosis of lung diseases such as Asthma and COPD has traditionally relied
on a combination of symptoms and conventional lung function tests using
spirometry that primarily identify the large airways and leave problems in the
small airways undetected.
Surface area of the larger airways approximately equals size of a beach towel,
whereas the area of the small airways approaches the size of a standard tennis
court.
Peripheral airway impairment may be more clinically relevant at all levels of
asthma severity and control

Assessment of small airways
Lipworth et al Lancet RM 2014 ;2:497-506

SMALL AIRWAY FUNCTION : IMPORTANCE OF ASSESSMENT
Monitoring small airway function can be useful in identifying patients who are at
risk for losing asthma control, and in assisting with clinical decisions and treatmen
In their 2009 study, Yamaguchi et al. demonstrated that an ultrafine particle
formulation improved small airway function in ASTHMA AND COPD patients
whereas the same active substance offered in a conventional inhaler failed to
produce any effect.
Moreover, the benefits of the novel finer particulate inhalers were picked up
only with Oscillometry and missed by Spirometry.

AIRWAY OSCILLOMETRY
 Oscillometry (also known as the forced oscillation technique)
 Measures the mechanical properties of the respiratory system (upper and
intrathoracic airways, lung tissue and chest wall) during quiet tidal breathing,
by the application of an oscillating pressure signal (input or forcing signal),
most commonly at the mouth.
King, Gregory G., et al. "Technical standards for respiratory oscillometry." European Respiratory Journal 55.2 (2020).

Principle of
Oscillometry
 In oscillometry testing, a stimulus is
applied to the respiratory system at
the mouth.
 The input signal is either the
pressure or flow oscillation, and the
response (in terms of flow or
pressure, respectively) is measured.
 The ratio of oscillatory pressure to
oscillatory flow generated from this
oscillatory stimulus is used to
calculate input impedance, and
represents the total mechanical
properties of the respiratory system.
Sound waves (green) are superimposed over the normal tidal breath (blue) during
respiration. Transducers measure the pressure and flow during exhalation for individual
frequency which is utilized to calculate impedance of the respiratory system

Oscillometry Principle (continued)…
The sound waves, being the mini pressure waves, cause subtle
pressure changes in the airway which leads to change in airflow.
 Smaller frequencies (2–4 Hz) can travel till the depth of lung
peripheries, whereas higher frequencies (>20 Hz) reach to proximal
conducting airways only.
 Middle range frequencies (5–20 Hz) are commonly used in clinical
practice to determine respiratory characteristics using fast Fourier
transform technique.
 Frequencies less than 5 Hz get easily altered by harmonics of the
normal breathing, whereas larger frequencies (>30 Hz) cause
subjective discomfort and are affected by shunting properties of
upper airways.
Gupta, et al.: Oscillometry – The future PFT. Karnataka Pediatric Journal • Volume 35 • Issue 2 • October-December 2020

INTERPRETATION
 Resistance (R) – Total, large/central, and small/ peripheral airway resistances are represented
as R5, R19/20, and R5–R19/20. R5 is always higher than R19/20.
This difference is practically negligible in adults, whereas it increases in younger children due to
significant contribution by peripheral airway resistance.
 In peripheral airway obstruction, R5 will increase with normal R19/20 (and higher R5–R19/20)
making frequency dependent airway resistance (R α 1/f).
In larger airway obstruction, both R5 and R19/20 will rise equally (with normal R5–R19/20),
which will be frequency independent. There will not be any change in restrictive lung diseases.
Karnataka Paediatric Journal • Volume 35 • Issue 2 • October-December 2020 |

Interpretation…
Spiky pattern in inspiration, demonstrated by >2 standard deviation variation in
subsequent efforts at 5 Hz, may suggest vocal cord dysfunction.[18] The finding
needs to be supported with further research
• Reactance (X) – It is usually measured at 5 Hz and becomes more negative in both
peripheral airway obstruction and lung parenchymal disease . It is not affected by
large airway obstruction
• Resonant frequency (Fres) – It increases (shift to right) in both restrictive and
peripheral airway obstructive diseases.[24] It is not affected by large airway
obstruction
• Reactance area (Ax) – It increases in both small airway obstruction and restrictive
diseases.It is not affected by central airway problems.

Respiratory characteristics in health and
disease.
Respiratory characteristics in health and disease.
R – Resistance (in cm H2O.L-1.s-1),
X – Reactance (in cm H2O.L-1.s-1).
During normal healthy conditions, the resistance
and reactance are at baseline (green).
Various combinations of changes in these
parameters will help in determining the nature
and location of pathology.

Changes in Oscillometry during pathological conditions
Respiratory characteristics in health and disease. R – Resistance (in cm H2O.L-1.s-1), X – Reactance (in cm H2O.L-1.s-1). During normal healthy conditions, the resistance and reactance are at baseline (green).
Various combinations of changes in these parameters will help in determining the nature and location of pathology

Limitations:
 A minimum amount of cooperation is still needed from patients even though
technique is tidal breath based.
 Standardization of the available machines with different manufactures is needed.
 Reference values for different populations are not available.
 Reference cutoff values for bronchodilator reversibility need to be validated with
more studies .
 Poor cheek support can reduce the resistance values.
 More research required in restrictive diseases, ventilated, and/ or sedated
patients and patients with vocal cord dysfunction.

COMPARISON WITH SPIROMETRY
 Oscillometry is more sensitive for the detection of peripheral airway obstruction and restrictive
diseases affecting lung parenchyma.
 Use of spirometry has been restricted in current COVID-19 pandemic due to reasons of enhanced risk
of disease transmission by potential aerosol generation.
◦ Forced breathing maneuver causes more aerosol generation due to “airway reopening phenomenon.”
◦ Breathing till residual volume will reopen the collapsed alveoli causing increased air turbulence, leading to
more production and release of smaller particles.
 A small volume tidal breath, as used in oscillometry, will not cause much disturbance in the internal
milieu and thus safeguarded in situations of active infections (such as influenza and corona).
◦ Recent study by Gupta et al. suggests oscillometry procedure being safer than spirometry in viral pandemic
situations

Spirometry and Oscillometry:
Comparative analysis

Spirometry AO
Outputs FEV1,FVC ,FEF25-75 R5, R20, X5, AX
Signal to noise ratio + +
Patient friendly - +
Breathing pattern Forced expiratory Tidal
Large/small airways +/- +
Cost + -
Portability + +
FDA approved + +
Comparison of Spirometry and AO
Lipworth et al, Resp Med 2018; 139 :106–109

AOS in a Nutshell – Tickboxes all characterstics of ideal lung function evaluation
Airwave Oscillometry (AOS) is a quick, easy
pulmonary assessment,effortlessly obtained
during regular tidal breathing,that provides
unique insights into small airway function.
Classic
PFT
tremoflo
AOS
Portable / 
Effortless (Tidal
Breathing)  
Suitable for
Preschoolers  
Easy for the
Elderly  
Captures Small
Airways  

Approach to a patient with Oscillomatric Assessment

TAKE HOME MESSAGE
 Oscillometry, being a tidal breath-based technique, can be a real privilege to
physicians and their patients for monitoring lung functions.
 It is more sensitive in detecting small airway pathologies than conventional
spirometry.
 Limited aerosol generation could be another reason for its use in viral
pandemics for monitoring lung functions.
 More research is required for identifying regional reference values and
standardization of machines.

SUMMARY TAKE HOME MESSAGE
AO IS AN EFFORT INDEPENDENT RAPID TEST TO MEASURE RESISTANCE (R) AND
COMPLIANCE (X)
AO (TREMOFLO) IS A MODERN PORTABLE USER FRIENDLY DEVICE TO MEASURE
LUNG RESISTANCE AND COMPLIANCE
AO IS USEFUL AND SENSITIVE TO DETECT SMALL AIRWAYS DYSFUNCTION (AX AND
R5-20) IN ASTHMA PATIENTS WITH PRESERVED FEV1 THAN CONVENTIONAL
SPIROMETRY
AX AND R5-20 ARE CLOSELY RELATED TO ASTHMA CONTROL AND T2 INFLAMMATION
LUNG COMPLIANCE (AX) IS MORE SENSITIVE THAN RESISTANCE (R5) IN COPD
OSCILLOMETRY, BEING A TIDAL BREATH-BASED TECHNIQUE, CAN BE A REAL
PRIVILEGE TO PHYSICIANS AND THEIR PATIENTS FOR MONITORING LUNG FUNCTIONS.
AO SHOULD BE USED IN CONJUNCTION WITH SPIROMETRY TO FULLY CHARACTERIZE
THE PHYSIOLOGY OF YOUR PATIENTS WITH ASTHMA AND COPD

Airway Oscillometry
 Oscillometry (also known as the forced oscillation technique)
 Measures the mechanical properties of the respiratory system (upper and intrathoracic
airways, lung tissue and chest wall) during quiet tidal breathing, by the application of an
oscillating pressure signal (input or forcing signal), most commonly at the mouth.
King, Gregory G., et al. "Technical standards for respiratory oscillometry." European Respiratory Journal 55.2 (2020).

Oscillometry : Origins & Evolution
Dubois et al.,
JAP 1956
1990 2000 2010 2020
Deskt
op
Handheld

Patient’s Quiet Breathing
tremoFlo Oscillation
Measured Waveform
Breathing
Pattern
Respiratory
Impedance:
Resistance and
Compliance
+
=
Airway Oscillometry:
Measurement Sequence

Nomenclature: FOT / IOS / AOS /OSC…..?
Confusion Cleared
FOT - “forced oscillation technique”
IOS or iOS - “impulse oscillometry,” often used interchangeably.
Both are oscillation mechanics methodologies
They use different stimulations to achieve sound viberation akin to vehicle can
be driven by Diesel,Petrol,CNG & now electric.
The “forced” of FOT refers the forcing properties of sine waves upon the
respiratory system. Unlike the FEV1, the term “forced” has nothing to do with
the maneuver performed by the subject
It is preferred to the use of the term “oscillometry” or “OSC,” or Airway
Oscillometry ( AOS ) which is the only term that correctly applies to all devices
and modes of stimulation and avoids the term “forced” that may be confusing
to some.

Patient’s Quiet Breathing
tremoflo Oscillation
Measured Waveform
Breathing
Pattern
Respiratory
Mechanics
Resistance (R)
Reactance (X)
+
=
Clic
k!
Measurement Sequence

OSC Asthma : Bronchodlation & Provocation Test > Spirometry
• Oscillometry parameters are more sensitive to identify
patients with asthma and to exclude those without
asthma than the parameters of spirometry.
• OSC is useful in the follow-up of asthma patients and may
detect airway obstruction earlier than spirometry
• Several studies have shown that a BDR based on
oscillometric parameters is better than one based on
forced expiratory volume in 1 s (FEV1) at differentiating
asthmatic from healthy children
• Several studies found that OSC may be more sensitive
than spirometry in detecting bronchoconstriction induced
by methacholine or allergens, as the increase in
resistance values preceded the fall in FEV1.

So why not Oscillometry……?
Reflects lung mechanics that provides a more “real-world” assessment of respiratory function.
Lung Function assessment done in normal breathing.
Humans do not use forced maneuvers in daily activity- hence obviates the need of patient’s
cooperation.
Reproducible over time,quick,more sensitive & correctly assesses small airway function
Can be done in pre school children,elderly,cognitive dysfuction & even physically challanged
patients.
Anyone who can breath can do ….!

Oscillometry : Challenges
Normograms are Specific to individual make of devices
Few Indian Normograms , more in children than adults
No uniform standardization ( Spirometry took 26 yr from 1979-2005 )
Cost : Oscillometry Devices > Spirometry , Portable > Fixed
Need for structured teaching module for learning oscillometry/interpretations .

AGENDA
Overview of small airways physiology
Airway oscillometry (AO) outcomes
Asthma:
Asthma severity and AO
AO in relation to asthma control, exacerbations and type 2
inflammation
COPD:
Discordance between resistance and reactance GOLD 1-4
Bronchoconstriction/dilatation and lung compliance
Summary

Airway oscillometry outcomes
Shi et al. JACI 2012;129(3):671-678.
Figure.

Reversibility:
• R5 = 48%
• R20=23%
• R5-20 =75%
• AX=79%
• X5=58%
• FEV1=16%
• FEF25-75=15%
R/X [Kpa/L.s]
AO reversibility to salbutamol in severe asthma
Galant et al Ann Allergy Immunol 2017;118:664-71

% Reversibility to salbutamol 400ug:
• FEV1:
Asthma 8% vs COPD 8%
• AX :
Asthma 40% vs COPD 24%
Reversibility in asthma and COPD
Kuo et al ,Lung 2019 ;197:473–481

AO and asthma severity
Except for central resistance, all AO parameters showed increased
abnormality with increased asthma severity and airflow obstruction
Williamson PA, et al. Lung 2011;189(2):121-129.
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Healthy volunteers (n = 24)
Mild-moderate asthma (n = 15)
Severe asthma (n = 21)
Total
resistance
(R5)
Central
resistance
(R20)
Peripheral
resistance
(R5–R20)
Peripheral
Reactance
(X5)
Median
kPa
lˉ
1
sˉ
1

Peripheral airway resistance R5-R20 (n=378) across BTS steps 2,3 and 4
• Abnormal values (>0.03kPa/L/s) are those above upper 95%CI for healthy controls
• Steps 2, 3 & 4 : 64.6%, 63.5% and 69.9% were abnormal
FEV1=84%
FEV1=90%
FEV1=86%
Anderson et al, Ann Allergy Asthma Immunol 2012; 109(3):185-189

Relationship of R5 to height in children
Galant Ann Allergy Asthma Immunol 2017;118:664-71

Using AO to predict subsequent loss of control in asthmatic children
AX >0.7kPa/L = 91% correctly classified
R5-R20 >0.1kPa/L/s = 83% correctly classified
Shi et al JACI 2013 ;131:718-23..

Small airways dysfunction (SAD) in pts with preserved FEV1 in
mild to mod asthma
n= 302/442 (68%) of mild to mod asthma pts in BTS steps
2-4 had preserved FEV1>80% (mean FEV1 97%)
In such pts with preserved FEV1 ,n=135/302 (45%) had
impaired AO as R5-20 >0.07 kPa/L/s
Pts with impaired R5-20 45% more likely to require OCS
(p=0.02) and and 47% more likely to require SABA (p=0.01)
Manoharan et al ERJ 2014 ;44:1353-5

Kuo et al Ann Allergy 2018;121:631-2
AO in relation to type 2 inflammation in mild to mod
asthma

AO in relation to asthma control in mild-mod asthma
Kuo et al ,Annals Allergy 2020 ; 124: 288-290

Relationship of AO and Spiro to disease control in mod-sev asthma
Jabbal et al JACI 2016 ;138:601-3

Impaired resistance and compliance are associated
with bronchial wall thickening in persistent asthma
Chan et al JACI IP 2022

Summary: AO in asthma
Resistance (R) and compliance (X) are concordant in asthma
Small airways dysfunction is common across all asthma severities
SAD is related to poor asthma control and T2 inflammation
Combining AO and Spiro provides the best predictor of poor control and exacerbations

Relationship of Resistance (R) and Compliance (X) to COPD severity
Crim et al Respir Med 2011;105:1069-78
% Difference GOLD 4 vs 2
• AX = 136%
• R5-20= 60%

Discordance between compliance (X) and resistance (R) after
methacholine challenge at PC20 in COPD
Walker Respir Med 2009 ;103:535-41

Relative discordance between resistance and compliance after carvedilol challenge
and LABA withdrawal in severe COPD
Jabbal & Lipworth ,Lung 2018;196:15-18
ICS/LABA

Summary : AO in COPD
Compliance (X) and resistance (R) are relatively
discordant in COPD
Lung compliance is more sensitive than resistance
in COPD

NORMAL VALUES
Impedance – Several studies have provided reference values for respiratory characteristics till date. The references
might vary as per the ethnicity and the oscillation technique used in different machines. The commonly used
regression equations, by the machine, for calculating R and X based on height (H) in meters, weight (W) in
kilograms, and age (A) in years are as follows:
for men –
Rmen = –0.2454. H+0.001564. W–0.00055. A+0.5919
Xmen = 0.1479. H–0.000402. W–0.00022. A–0.1721
and for women –
Rwomen = –0.4300. H+0.00165. W–0.00070. A+0.9312
Xwomen = 0.2487. H–0.001700. W–0.00053. A–0.2158

Normal Values
Normative values from Indian populations need to be devised.
Gupta et al. have recently demonstrated a negative correlation between oscillometry
parameters with height followed by body mass index in Indian children, while evaluating airway
reversibility in asthmatic patients.[16] There was no gender influence observed on any of the
parameter.
• Resonant frequency – The normal values of Fres varies in between 6 and 12 Hz in healthy
adults and it tends to be more in children
• Reversibility – The recommended cutoffs for significant bronchodilator response in both adults
and children are –40% in R5, +50% in X5, and –80% in Ax. These values might vary with severity
of disease and more studies are required before considering them as benchmark
• Degree of bronchoconstriction – Cutoffs for X5 have varied from 50 to 80% and more studies
are needed to provide reference values for specific populations.

Respiratory characteristics in health and disease.
Respiratory characteristics in health and
disease. R – Resistance (in cm H2O.L-1.s-1),
X – Reactance (in cm H2O.L-1.s-1).
During normal healthy conditions, the
resistance and reactance are at baseline
(green).
Various combinations of changes in these
parameters will help in determining the nature
and location of pathology.

INTERPRETATION
 Resistance (R) – Total, large/central, and small/ peripheral airway resistances are represented as
R5, R19/20, and R5–R19/20. R5 is always higher than R19/20.
This difference is practically negligible in adults, whereas it increases in younger children due to
significant contribution by peripheral airway resistance.
 In peripheral airway obstruction, R5 will increase with normal R19/20 (and higher R5–R19/20)
making frequency dependent airway resistance (R α 1/f).
In larger airway obstruction, both R5 and R19/20 will rise equally (with normal R5–R19/20), which
will be frequency independent. There will not be any change in restrictive lung diseases.

INTERPRETATION…
Spiky pattern in inspiration, demonstrated by >2 standard deviation variation in subsequent
efforts at 5 Hz, may suggest vocal cord dysfunction.[18] The finding needs to be supported
with further research
• Reactance (X) – It is usually measured at 5 Hz and becomes more negative in both
peripheral airway obstruction and lung parenchymal disease . It is not affected by large airway
obstruction
• Resonant frequency (Fres) – It increases (shift to right) in both restrictive and peripheral
airway obstructive diseases.[24] It is not affected by large airway obstruction
• Reactance area (Ax) – It increases in both small airway obstruction and restrictive
diseases.It is not affected by central airway problems.

COMPARISON WITH SPIROMETRY
 Oscillometry is more sensitive for the detection of peripheral airway obstruction and
restrictive diseases affecting lung parenchyma.
 Use of spirometry has been restricted in current COVID-19 pandemic due to reasons of
enhanced risk of disease transmission by potential aerosol generation.
◦ Forced breathing maneuver causes more aerosol generation due to “airway reopening
phenomenon.”
◦ Breathing till residual volume will reopen the collapsed alveoli causing increased air turbulence,
leading to more production and release of smaller particles.
 A small volume tidal breath, as used in oscillometry, will not cause much disturbance in
the internal milieu and thus safeguarded in situations of active infections (such as
influenza and corona).
◦ Recent study by Gupta et al. suggests oscillometry procedure being safer than spirometry in viral
pandemic situations

OSCILLOMETRY :
CLINICAL APPLICATIONS
 Provides practically useful information regarding the subtle changes in airways
with greater sensitivity, in both children and adults, when compared to
spirometry
 Useful to assess abnormal distal airway function, in case of clinical suspicion
with normal spirometry
 Bronchodilator reversibility can be demonstrated with short-acting β-2 agonists
and ipratropium
 Good potential in diagnosis and monitoring of restrictive lung diseases such as
bronchopulmonary dysplasia, cystic fibrosis, and interstitial lung disease
 Feasible option in children, the elderly, and those with neuromuscular diseases
and impaired intellect
 Potentially useful in patients on mechanical ventilation and during sleep.
 Safer than spirometry during viral pandemic situations (e.g., influenza and

Approach to a patient with Oscillomatric Assessment
FOT: Forced oscillation technique, IOS: Impulse oscillometry, SABA: Short-acting β2 agonist, LABA: Long-acting β2 agonist, R: Resistance (in cm H2O.L-1.s-1),
X: Reactance (in cm H2O.L-1.s-1), Fres: Resonant frequency (in Hz), Ax: Reactance area

APPROACH TO A PATIENT WITH OSCILLOMATRIC ASSESSMENT

Cho et al. ARJCCM 2020
Lung Transplants Monitoring : Oscillometry > Spirometry
AOS in Acute Cell Rejection
SAD in all 16 episodes 100%
success
Spirometry unaltered in 15/16
episodes
Acute cell rejection picked up
in all case earlier than
spirometry obviating need of
biopsy.
OSCILLOMETRY HAS REPLACED
SPIROMETRY HERE.

Technique
 He/she is asked to hold the mouth piece with his/her teeth and to make a tight seal around it with
lips to prevent any air leak during the FOT maneuver.
 A nose clip is applied to occlude both the nostrils and he/she is asked to breathe through mouth
piece.
 Height of sitting stool/chair and/or mouth piece is adjusted to achieve a comfortable position for the
patient with slight neck extension. As FOT is based on small pressure oscillations and a little change in
resistance or air leak can affect the interpretations significantly, it is important to ensure adequate seal
around nose and mouth piece.
 The cheeks, most compliant part of respiratory system in children, should be supported firmly either
by patient him/herself or attendant to minimize wobbling.
 After appropriate positioning, patient is asked to perform normal tidal breathing in a relaxed manner.

Technique
 Calibration of the machine, at least once a day, is desired with the external resistor
or as per the manufacturer’s specifications.
 Bronchodilator medications (short-acting β-2 agonist for 4 h and long-acting β-2
agonist for 24 h) should be stopped before the procedure.
 After explaining the procedure (preferably by recorded video demonstration) to
patient and attendants, anthropometric measurements (weight, height, and body
mass index) are documented.
 Demographic (name, age, gender, area of residence, and identification number)
and anthropometric parameters are entered in the machine after calibration.
 Patient is asked to sit on an examination stool/chair, with uncrossed legs to reduce
the influence of extrathoracic pressure with straight back . Image taken from Karnataka Paediatric Journal •
Volume 35 • Issue 2 • October-December 2020

 An average of 10 respiratory efforts or 1 min, whichever is earlier, is
required to assess the respiratory characteristics during any maneuver.
 Acquisitions of minimum 30 s for adults and 16 s for children (<12
years of age) with at least three acceptable breaths are recommended.
Respiratory efforts meeting acceptability criteria are considered valid,
whereas maneuvers with artifacts such as airflow obstruction by tongue
or glottic closure, irregular breathing, coughing, crying, swallowing, and
improper technique will be discarded by the machine.
 A maximum of three acceptable maneuvers are recorded and checked
for coherence or CoV. Mean respiratory impedance (resistance and
reactance), resonant frequency, and reactance area are documented.
The procedure is repeated 15 min after inhaled short-acting β-2 agonist
to identify any post-bronchodilator reversibility.
Technique
Acceptability criterias – All are required

CICM FOT Theories and Reports interpretation slides (1) (1).pptx 5112023.pptx

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