Dr. Alireza Safaiyan Occupational medicine specialist
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PFT Pulmonary Function Testing PFTs can include : 1) Simple
screening spirometry 2) Formal lung volume measurement 3) Diffusing
capacity for carbon monoxide 4) Arterial blood gases 5) Inhalation
challenge tests 6) Exercise stress tests
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Total lung capacity (TLC) FRC is usually measured by: 1) gas
dilution technique or 2) body plethysmography
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Gas dilution technique Helium dilution techniques: based on the
inhalation of a known concentration and volume of an inert tracer
gas, such as helium, followed by equilibration of 7 to 10 minutes
in the closed- circuit helium dilution technique. The final exhaled
helium concentration is diluted in proportion to the unknown volume
of air in the patient's chest (residual volume). Nitrogen-washout
technique: the patient breathes 100% oxygen, and all the nitrogen
in the lungs is washed out. The exhaled volume and the nitrogen
concentration in that volume are measured. The difference in
nitrogen volume at the initial concentration and at the final
exhaled concentration allows a calculation of intrathoracic volume,
usually FRC.
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Gas dilution technique A limitation of this technique is that
it does not measure air in noncommunicating bullae, and therefore
it can underestimate total lung capacity, especially in patients
with severe emphysema.
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Body plethysmography principle of Boyle's law, which states
that the volume of gas at a constant temperature varies inversely
with the pressure applied to it can measure the total volume of air
in the chest, including gas trapped in bullae. can be performed
quickly
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D L CO Diffusing capacity of the lung for carbon monoxide the
single-breath breath-holding technique a subject inhales a known
volume of test gas that usually contains 10% helium, 0.3% carbon
monoxide, 21% oxygen, and the remainder nitrogen. holds his or her
breath for 10 seconds. exhales to wash out a conservative
overestimate of mechanical and anatomic dead space. an alveolar
sample is collected. D L CO is calculated from the total volume of
the lung, breath-hold time, and the initial and final alveolar
concentrations of carbon monoxide Hemoglobin concentration is a
very important measurement in interpreting reductions in D L
CO
Exhaled Nitric Oxide The measurement of exhaled nitric oxide as
a reflection of airway inflammation is gaining rapid acceptance as
a pulmonary function test
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Inhalation challenge tests (Bronchoprovocation) To define
nonspecific airway hyperreactivity Methacholine and histamine are
the agents most often used with this procedure inhaled through a
nebulizer, although other agents may also be useful. a five-stage
procedure with five different increasing concentrations.(0.0625 16
mg/ml) After each stage, the patient performs a spirometry. a 20%
reduction in the FEV 1 (PC 20FEV1 ) is significant. In rare cases,
a bronchospasm can occur with inhalation challenge testing.
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Exercise stress tests Exercise stress tests evaluate the effect
of exercise on lung function tests. Spirometry readings are done
after exercise and then again at rest.lung function tests
Six-minute walk test
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Definition of spirometry A physiological test for measuring
volumes inhaled or exhaled by an individual as a function of time A
physiological test for measuring volumes inhaled or exhaled by an
individual as a function of time A non-invasive method of
evaluation of pulmonary function A non-invasive method of
evaluation of pulmonary function Not for definitive diagnosis Not
for definitive diagnosis Simple, cost effectiveness, accessible
Simple, cost effectiveness, accessible Needs patient cooperation
Needs patient cooperation
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Indication Not a screening test for general population Not a
screening test for general population Diagnostic Diagnostic
Monitoring Monitoring Impairment evaluation Impairment evaluation
Public health Public health
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Diagnostic To evaluate symptoms Chest pain Cough Dyspnea
Orthopnea Phlegm production To evaluate signs Wheezing Chest
deformity Cyanosis Diminished breath sounds Expiratory slowing
Overinflation Unexplained crackles To evaluate abnormal laboratory
tests Abnormal chest radiographs Hypercapnia Hypoxemia Polycythemia
To measure the effect of disease on pulmonary function To screen
persons at risk for pulmonary diseases Smokers Persons in
occupations with exposures to injurious substances Some routine
physical examinations To assess preoperative risk To assess
prognosis (lung transplant, etc.) To assess health status before
enrollment in strenuous physical activity programs
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Monitoring To assess therapeutic interventions Bronchodilator
therapy Steroid treatment for asthma, interstitial lung disease,
etc. Management of congestive heart failure Other (antibiotics in
cystic fibrosis, etc.) To describe the course of diseases affecting
lung function Pulmonary diseases Obstructive small airway diseases
Interstitial lung diseases Cardiac diseases Congestive heart
failure Neuromuscular diseases Guillain-Barr syndrome To monitor
persons in occupations with exposure to injurious agents To monitor
for adverse reactions to drugs with known pulmonary toxicity
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Evaluation of Disability or Impairment To assess patients as
part of a rehabilitation program Medical Industrial Vocational To
assess risks as part of an insurance evaluation To assess persons
for legal reasons Social Security or other government compensation
programs Personal injury lawsuits Other
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Public Health Epidemiologic surveys Comparison of health status
of populations living in different environments Validation of
subjective complaints in occupational or environmental settings
Derivation of reference equations
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Indications in occupational medicine Primary prevention
(Pre-employment) Primary prevention (Pre-employment) physical
demands of a job require a certain level of cardiopulmonary
fitness, eg, heavy manual labor or firefighting Respirator use can
impose a significant burden on the cardiopulmonary systems, eg, use
of a self-contained breathing apparatus, or prolonged use of
certain negative- pressure masks under conditions of heavy physical
exertion and/or heat stress Research (Respiratory hazards)
Contraindications Active hemoptysis Active hemoptysis
Pneumothorax Pneumothorax Unstable Cardiovascular status (6 w)
Unstable Cardiovascular status (6 w) Cerebral/Thoracic/Abdominal
aneurysm Cerebral/Thoracic/Abdominal aneurysm Recent eye surgery
Recent eye surgery Acute disorder that may interfere with
performance (e.g, vomiting) Acute disorder that may interfere with
performance (e.g, vomiting) Thoracic or abdominal surgery( 3 w)
Thoracic or abdominal surgery( 3 w) Recent CVA or pulmonary emboli
Recent CVA or pulmonary emboli Respiratory distress Respiratory
distress
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Confounding factors Common cold (previous 3 days) Common cold
(previous 3 days) Severe respiratory infection (previous 3w) Severe
respiratory infection (previous 3w) Smoking( 1hr) Smoking( 1hr)
Heavy food (1hr) Heavy food (1hr) Bronchodilator use Bronchodilator
use
Type of spirometer Flow-type spirometer Volumetric
spirometer
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Hygiene & infection control Hand washing Hand washing
Gloves Gloves Disposable mouth piece & nose clip Disposable
mouth piece & nose clip Disinfection or sterilization of
reusable mouth piece Disinfection or sterilization of reusable
mouth piece Extra precautions for patient with known transmissible
infection Extra precautions for patient with known transmissible
infection
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Normality and predicted equations lung function, such as FEV 1
or FVC, are affected most significantly by standing height, age,
gender, race, and, to a lesser extent, weight These reference
standards are based on a cohort of normal subjects of similar age,
height, and race, with normal being defined as persons without a
history of smoking or disease that can affect lung function.
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Reference values Knudson (male/ female) Knudson (male/ female)
National Health and Nutrition Examination Survey (NHANES III) ERS
(ECCS) ERS (ECCS) ATS ATS Golshan Golshan ITS ITS
Slide 29
Spirometric values FVC Forced vital capacity; the total volume
of air that can be exhaled during a maximal forced expiration
effort. FEV 1 Forced expiratory volume in one second; the volume of
air exhaled in the first second under force after a maximal
inhalation. FEV 1 / FVC ratioThe percentage of the FVC expired in
one second. FEV 6 Forced expiratory volume in six seconds. FEF
2575% Forced expiratory flow over the middle one half of the FVC;
the average flow from the point at which 25 percent of the FVC has
been exhaled to the point at which 75 percent of the FVC has been
exhaled. MVVMaximal voluntary ventilation. This measures the
greatest amount of air you can breathe in and out during one
minute. Lung volumes ERVExpiratory reserve volume; the maximal
volume of air exhaled from end-expiration. IRVInspiratory reserve
volume; the maximal volume of air inhaled from end-inspiration.
RVResidual volume; the volume of air remaining in the lungs after a
maximal exhalation. V T Tidal volume; the volume of air inhaled or
exhaled during each respiratory cycle. Lung capacities
FRCFunctional residual capacity; the volume of air in the lungs at
resting end-expiration. ICInspiratory capacity; the maximal volume
of air that can be inhaled from the resting expiratory level.
TLCTotal lung capacity; the volume of air in the lungs at maximal
inflation. VCVital capacity; the largest volume measured on
complete exhalation after full inspiration.
Subject maneuvers FVC maneuver Closed circuit Closed circuit
Open circuit Open circuit Well-fitting false teeth yes or no
Well-fitting false teeth yes or no Sitting or standing Nose clip
Procedure Procedure 1. Inhale compete 2. Exhale: with minimal
hesitation blast not just blow keep going
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maneuver evaluation Start of test criteria Start of test
criteria - Extrapolation volume (EV < 5% of FVC or 150 ml) -
Time-to-PEF < 0.120 s - Time-to-PEF < 0.120 s End of test
criteria End of test criteria - the subject cannot or should not
continue - exhalation at least 6s (in children
