Pulmonary Function Testing
SPECIALIZED TEST REGIMENS
The diagnosis of specific
pulm. disorders requires
certain testing
The subject must go through a
thorough Hx
Regimens
Clinic or MDs office
– VC, FVC, FEVT, FEVT%, FEF 25-75, 200-1200,
MVV, VT, f, VE
Hospital lab & CP lab
– lung volumes and diffusing capacity
PULMONARY FUNCTION
TESTING IN CHILDREN
Uses many of the same basic tests as for
adults
Differences exists in dimensions and two
main areas of concern
– newborns, infants, and very young children cannot
strictly perform tests that require and depend on
pt. cooperation ( VC, FVC, MVV and DLCO)
– young children may perform with variability those
tests that are effort dependent and require
cooperation
A cooperative patient and good PFT
technologist
Children may not meet
ATS criteria but careful
evaluation of partial
parameters can provide
important information.
Techniques for infants and
young children
Partial Exp. Flow-Volume Curves ( PEFV) record of the maximal flow developed over a
portion of the VC
The forced exhalation is obtained by applying
either a positive pressure to the thorax and
abdomen or a negative pressure to the
airway
RAPID
THORACOABDOMINAL
COMPRESSION ( RTC) the
“squeeze” or “hug”
Non-intubated infants
uses an inflatable jacket that surrounds the
thorax and abdomen
– the PEFV is obtained by rapidly applying pressure
to the thorax and abdomen at the end of insp.
– performed after the infant has fallen asleep or
slightly sedated ( chloral hydrate)
– flow is measured using an infant mask sealed with
a lubricant and attached to a low Ds pneumotach
Flow @ FRC or Vmax FRC
By Rapid Thoraco-Abd.
Compression(Squeeze)
expiratory flow
limitations can now also
be measured in babies.
The baby wears an
inflatable cuff with the
help of which a forced
expiration is produced.
From Viasys (Jaeger)
WOW!
testing
RAISED VOLUME RAPID
THORACOABDOMINAL COMPRESSION
- RVRTC
Standardization of spirometry is dependent
on TLC
during insp., flow is augmented by a pump to
increase pressure and volume
the airway is occluded at the exh. port using a
cuff with variable pressure - rapid chest
compression is then performed - higher
flows are generated
– uses a pump to increase volume before the
squeeze is performed
METHODS
FORCED DEFLATION TECHNIQUE - The
infant needs to intubated, sedated &
paralyzed
– the lungs are manually inflated to TLC using
approx. +40 cmH20 - performed 4 times with a 2-3
sec breath hold
– the airway is then connected to a source of
negative pressure ( -40 cmH20)
– air is evacuated for a max. of 3 secs or until airflow
ceases
– exp. flow is plotted on a flow - volume graph
– lungs are reinflated with 100 % O2
– reserved for the critically ill
BRONCHODILATOR
BENEFIT TEST
Is the dz is reversible? Let’s find out.
Indication
– a pt. with an FEV1% of less than 70%
Technique
– follow guidelines on withholding certain meds prior
to test
– do PFT - give tx with bronchodilator via neb or
MDI - wait 15-20 mins before doing post tests
– monitor pt. for adverse effects
Significance
Calculate “ percent change of
each parameter”
%change = postdrug - predrug
predrug
FEV 1 or FVC are evaluated an increase of > 12 % and
> 200 ml is significant
asthma shows the best
improvement
SGaw should increase 30-40
% to be significant
100.00%
80.00%
60.00%
40.00%
20.00%
0.00%
FVC
FEV1
% Pred
% Pred Postdrug
% Change
SGAW
BRONCHOPROVOCATION
(METHACHOLINE
CHALLENGE)
Methacholine
Used to determine whether or not a patient has a
disorder of airway hypersensitivity
And to what extent
Is a parasympathomimetic
– May trigger bronchospasm
Methacholine challenge
the test is positive when there is a 20 %
decrease in the FEV 1 - the concentration at
which the decrease occurs is called the
provocative concentration or PC20%
Healthy subjects do not display a decrease in
FEV1 greater than 20 %
SGaw can be used with FEV1 to demonstrate
a reaction
Use a 16 mg/ml stock methacholine solution
Technique
Subjects should be
tested when
asymptomatic, baseline
FEV 1 > 70 % of the pt.
norm
Withhold meds
according to chart
2 methods accepted by
ATS,1st baseline spiro
– 5-breath dosimeter method
– 2-minute tidal breathing
method
5-Breath Dosimeter Method
Dosimeter- deliveres a consistent volume of drug
– Uses 5 doses each 4 x larger than the previous
– pt. inhales 5 nebulized NS breaths 1st
– perform spirometry
– if no positive response, start dosimeter
inhalations of 5 breaths for 2 minutes
– Repeat spirometry
• Use largest FEV1 and the average of 2 RAW
• Look for > 20% drop in FEV1 and > 35% drop in SGAW
2-Minute Tidal Breathing Method
Use nebulizer, nose clips and relaxed breathing
Perform diluent inhalation first, then spirometry
10 double concentrated doses are used, each
dose is breathed for exactly 2 minutes
Spirometry is performed 30 & 90 seconds after
the dose
– Look for > 20% in FEV1 and >35% drop in SGAW
– Give a bronchodilator & repeat spirometry in 10”
To caluculate the percent of decrease
%Decrease =
Con. FEV1 – Current FEV1
Control FEV1
Preoperative PF Testing- to…
Estimate postop lung
function
Plan periop care
Estimate morbidity &
mortality
Look at
– Spirometry/obstruction
– Bronchodilation studies
– ABG’s, Ex. Testing &
DLCO
PULMONARY FUNCTION TESTING
FOR DISABILITY
Respiratory impairment - the failure of one or more
functions of the lungs as determined by PFT
Disability - the inability to perform tasks required
for employment and includes medically
determinable physical or mental impairment - the
impairment must be expected to result in death or
last for at least 12 months
To determine impairment
should characterize the type, extent and cause of
impairment
other factors need to be known - age, educational
background and the subjects motivation and energy
requirements
for pulm. dz impairment, you also need a hx, physical,
CXR, other appropriate imaging techniques and PFT’s (should be specific to disorder being investigated)
FVC and FEV1
spirometry is the most useful for determination of
impairment caused by airway obstruction
–
–
–
–
–
the subject should be stable- use largest of the 3 tests
the 2 largest FVC and FEV1 should be within 5% or 100 cc
should be cont. for 6 secs or no volume change detected for 2 secs
- must have a volume-time tracing so hand calculations can be performed
before and after bronchodilator - all parameters reported in BTPS and ht.
obtained without shoes or arm span method
– must use disability limits
– Calibration of equipment is specific and must be documented
DLCO & ABG’s
useful in determining disability for restrictive
disorders
– should not be corrected for Hgb or COHb abnormalities but…
the values at the time of the test should be noted
– if the DLCO is > 40% predicted but < 60% , get resting ABG
ABGs
– may be nonspecific due to various factors
– look at other parameters along with ABGs
Exercise Testing
subjects considered should have resting ABGs
a Steady State protocol using the treadmill is
preferred
specific protocols should be followed
Limits for determining disability on the bases of
pulm. impairment have been set for the US by
the SS administration