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An introduction to Pulmonary Function Testing

Richard Stephenson

on 31 January 2014

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airway resistance
bronchoprovocation test
closing volume
diffusion capacity
expiratory reserve volume
forced vital capacity
functional residual capacity
inspiratory capacity
inspiratory reserve volume

lung capacity
lung volumes
maximum voluntary ventilation
minute volume
nitrogen washout
obstructive disease
peak inspiratory flow
residual volume
respiratory quotient
restrictive disease
total lung capacity
vital capacity
FEV1, FEV3, FEF 25-75%
What do you think are some of the purposes of PFT?
1. To determine if there is a pulmonary disease

2. To quantify and determine the extent of the pulmonary disease (mild, moderate, severe)

3. To assess and quantify a response to therapy

4. To evaluate those whose occupation exposes them to certain inhalants

5. To qualify one for disability

6. Preoperative screening
What determines what values a patient should achieve on a PFT?
Equipment used to measure volumes
Graphic presentation of the flow of air in and out of the lungs
Actual tracing of the the PFT

What is tidal volume?
Answer: the amount of air moving in and out of the lungs during quiet breathing
What is the formula for minute volume?
Answer: Vt x f
What is vital capacity?
Answer: the amount of air exhaled after a maximum inhalation
What is inspiratory capacity?
Answer: the amount of air inhaled after a
What lung expansion tool does this remind you of?
Incentive spirometer
What is functional residual capacity?
Answer: the amount of air left in the lungs after a normal exhalation
In summation:
The four capacities are
Total lung capacity
Forced vital capacity
Inspiratory capacity
Functional residual capacity
What is residual volume?
Answer: volume left in the lungs after a maximal exhalation
What is expiratory reserve volume?
Answer: volume of air exhaled in excess of normal expiratory tidal volume
What is inspiratory reserve volume?
Answer: volume of air inhaled in excess of a normal inspiratory tidal volume
Remember the volumes!
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume

Helpful Info?
How are capacities and volumes measured in the modern day PFT lab?
The Body Plethysmograph or "Body Box"
FRC, RV and TLC cannot be measured directly; only through indirect methods.
Body Plethysmography
Nitrogen Washout
Helium Dilution
These are referred to as static measurements
We will discuss each of these later!
Bring oxygen into the body via the airways
What do the lungs do?

PFT measure:
Dynamic flow
Lung volume and capacity
Diffusion capacity

Which of the following cannot be measured directly?
a. FRC
b. FVC
c. RV
d. TLC
ans: a,c,d
Four general principles that should be considered for pulmonary function tests.
Specificity: PFT are not specific in diagnosing diseases
Sensitivity: is the test able to detect disease even in apparently healthy people?
Does a patient have to be seriously ill before abnormal results are detected
Validity: is the test a good test?
Reliability: are the results consistent?

Dynamic Testing
forced vital capacity (FVC) or slow vital capacity (SVC):
should exceed 20 ml/kg
forced expiratory volume in 1 second (FEV1):
Normally we exhale > 75% of our air in 1 second

forced expiratory volume in 1 second-to-vital capacity ratio (FEV1/FVC percentage)
PEFR: the highest flowrate

Principles of Testing
Dynamic Testing
forced expiratory flow between 200 ml and 1200 ml of FVC (FEF200-1200) reflects flow through the larger airways: why?
forced expiratory flow between 25% and 75% of FVC (FEF25%-75%) reflects flow through the smaller airways
forced expiratory volume in half of a second (FEV0.5)
forced expiratory flow between 75% and 85% of FVC (FEF75%-85%) reflects flow at the end of exhalation

Forced vital capacity: curve and or loop

Spirometry is an effort dependent test; the better the effort, the better the results
We must demonstrate to the patient how we want them to perform the FVC
Have the patient wear nose clips; why?
Patient should either be standing or sitting
Teeth and lips should be sealed around mouthpiece

Spirometry: technique

Patient should breath normally in and out through the mouthpiece
At the end of a tidal volume breath, take a deep breath and blow out the air as forcefully as possible over at least 6 seconds
Have the patient take a large, deep inhalation after exhaling all their air (flow-volume loop)

Spirometry: technique

Always have the patient perform 3 FVC
Adults should exhale for at least 6 seconds
Reproducibility; the largest and 2nd largest FVC results should be within 0.150 L of each other
Choose the highest FVC and highest FEV1 to obtain an FEV1/FVC ratio
The best curve has the highest sum of FVC + FEV1
All reading must be converted to BTSPS

Rules to follow per American thoracic society (ATS)

When assessing the extent of airway obstruction, FEV1 and FEV1/FVC% are the results mainly observed by clinicians
Measures the volume exhaled in 1 second
The FEV1/FVC%: what % of the FVC was exhaled in 1 second?
Used to differentiate between obstructive and restrictive disease

Fev1 and fev1/ fvc percentage

Assessing the results
Obstructive vs. Restrictive: How can we tell the difference?
How to tell the difference between obstructive and restrictive lung disease

Obstructive or Restrictive

Obstructive vs. Restrictive
In patients with obstructive lung disease:
FEV1/FVC% will be below 70% e.g.

Example: Normal airways: FEV1 4.0 L and the FVC is 5.0L; what is the ratio?

Ans: 80%
Example: Obstructive airway disease: FEV1 3.0L and the FVC is 5.0 L; what is the ratio?

Ans: 60%
Obstructive vs. Restrictive
Why is the ratio lower in obstructive airway disease?

Ans: they have increased airway resistance caused by:
-Airway inflammation

- Bronchial smooth muscle contraction

- Increased airway secretions

- Loss of airway tone

Obstructive vs Restrictive
Patients with
restrictive lung

will have:
Below normal FEV1
Below normal FVC
Normal or higher than normal FEV1/FVC% (80% or higher)

Restrictive Lung Disease
Obstructive Lung Disease
Restrictive example:
Normal FVC = 4.0L
Their Actual FVC is = 2.5L
Normal FEV1 = 3.2L
Their Actual FEV1 is = 2.0L
What is the FEV1/FVC ratio?
Ans: 80%; why are the volumes decreased?
Ans: Restrictive disease
Lower Limits of Normal:
Interpreting PFT Results

LLN: what does it all mean?
Why is this important?
Because a young person may have an FEV1 that is 80% of predicted but may be in the 5th percentile or the lower limits of normal meaning they may have airway disease that would be undiagnosed
An older person may have an FEV1 that is 60% of predicted but is within the 95th percentile meaning they are normal. However they could be misdiagnosed as having obstructive lung disease and given unnecessary treatment for it
Obstructive usually means one is having difficulty exhaling
Restrictive usually means that one is having difficulty inhaling
In Wilkin’s Clinical Assessment in Respiratory Care 7th Edition, read pages179-188
In Egan's, read pages 418-432. Stop after bronchial challenge
In the Egan workbook, answer the following:
1. Do the Word Wizard page 153
2. Numbers 17-20, 25 -32
Due Wed 1/29/14
Homework Assignment
Reversibility: Pre and Post Bronchodilator
Pre and post bronchodilator test; what is the purpose?
Reversibility is defined as a 12% improvement in FEV1 per the ATS and/or a 200 ml increase in FEV1
Which bronchodilator listed below would you administer to do a pre and post study?
a. Serevent
b. Pirtbuterol
c. Spiriva
c. Intal

Pre and post bronchodilator testing

Ans: b
Bronchial Provocation:
What does this mean?
What drug is used for bronchial provocation?
Ans: methacholine
Why methacholine?
Ans: it is a cholinergic medication
Saline or cold air can also be used
What is the indication for this test?

When PFT is normal but hyperractive airway disease is suspected due to exertional dyspnea, dyspnea due to occupational exposure, or cold air dyspnea

Before the bronchial provocation test, the patient should avoid:

Beta 2 adrenergics and anticholinergics for at least 8-12 hours

Cigarettes, caffeine for 6 hours

NSAID and theophylline for 48 hours

Patient can continue using anti-inflammatory drugs

Administer methacholine via aerosol starting with a dose of 0.03 mg/ml followed by an FVC

Technique for Bronchoprovocation Testing

Double the dosage until FEV1 drops to 20% of predicted

A 20% drop is considered a positive response and indicates hyper-reactive airway

Which medication below should be administered following a bronchial provocation?

a. Salmeterol
b. Arfomoterol
c. Albuterol
d. Tiotropium bromide

Ans: c
Maximum voluntary ventilation or MVV
MVV: Why?
Assess respiratory muscle strength
Assess airway resistance
MVV is an effort dependent test

MVV Technique:

Have the patient sit down
Patient breaths deep and fast for 12 seconds
Extrapolate the minute volume by multiplying the volume reached in 12 seconds by 5
Normal values should be 150 L to 200 L / minute

Remove carbon dioxide (CO2) from the body via the airways

Allow gas exchange between the alveoli and the capillaries
Pulmonary Function Test can tell the clinician:
The ability of gases to diffuse across the alveolar/capillary membrane
Lung volumes and capacities
The status of the airways
there is an easier method to measure MVV
When performing a routine PFT, multiply the FEV1 by 40
This will give you an estimated MVV
However to evaluate muscle strength, we must have the patient do an MVV the old-fashioned way
MVV Video
Upper Airway Obstruction
There are 3 types of obstructions:
Fixed upper airway obstruction
Extrathoracic upper airway obstruction
Intrathoracic upper airway obstruction
What is the formula for resistance?
Raw = change in P/change in flow
Remember Poiseulle's Law?
What happens to flow when resistance increases?
Ans: flow decreases
What happens to flow when radius decreases?
Ans: flow decreases
What happens to flow if pressure increases?
Ans: greater the pressure change, the greater the flow
What is the formula for compliance?
C =
What happens to volume if compliance decreases and pressure is constant?
Ans: volume decreases
What happens to pressure if compliance decreases but volume is constant?
Ans: pressure must increase
Homework for next week
Due next Wednesday February 5th
Read Egan Chap 17 pages 433-445
Read Wilkin’s Chap 9 pages 188 Static Lung Volumes to page 196 Bronchoprovocation Testing
In the Egan workbook do the following:
Questions 33-39

PFT: Hazards and Complication

Paroxysmal coughing
Increased ICP
Syncope, dizziness

O2 desaturation from interruption of O2 therapy

Per the AARC
Chest pain
Per the AARC
Contraindications of PFT
Hemoptysis of unknown origin
Cardiovascular instability
Thoracic, abdominal or cerebral aneurysm
Recent eye surgery
Presence of acute disease that may impair performance
Recent abdominal or thoracic surgery

This assures that the spirometer is accurate and precise

Should be performed everyday before use and documented

Use a 3 L syringe (known volume of air)

Inject and withdraw piston on syringe at different speeds to make sure fast, medium, and slow flows are measured correctly

Acceptable range of calibration with a 3 L syringe is + or – 3% or 2.91 to 3.09 L

Calibration and Quality Contol
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