Post on 07-May-2015
Pulmonary Function Testing
Frank Sciurba, M.D.
Indications for Pulmonary Function Testing
1. Categorization of the type and severity of physiologic perturbation
• Restrictive vs. obstructive categorization– Asthma vs. emphysema
2. The objective assessment of pulmonary symptoms.– Documentation of abnormality– Disability assessment
3. Documentation of progression of disease. – COPD– Neuromuscular disease such as ALS
Indications for Pulmonary Function Testing
4.Documentation of the patient’s response to therapy.• Asthma control• Lung volume reduction surgery
5.Preoperative assessment• Lung cancer resection• Timing of lung transplantation
6.Screening for sub clinical disease• Emphysema in a tobacco smoker.• Occupational risk.
Component of respiration
Pulmonary function test
Ventilation a. Spirometry (FVC, FEV1 etc.)
b. Lung volume (RV, FRC, TLC)– Plethysmography
– Helium dilution
c. Inspiratory and expiratory pressure (MIP, MEP)
d. Lung compliance (rarely actually measured clinically)
e. Maximal voluntary ventilation (MVV)
f. Exercise ventilation (Ve-max, Vd/Vt)
Diffusion Diffusing capacity
Exercise Oxygen Saturation
Circulation Diffusing capacity (DlCO)
Cardiopulmonary exercise testing (VO2-
max)
Control (see Sanders lecture)
Spirometry
• Measures how much and how fast
• Most common and simple test
(can be performed in primary care office)
Spirometry
• Only measures what comes out
• How much and how fast?
• How much: Vital Capacity– A strong prognostic indicator in Framingham
study for all cause mortality
• Slow vital capacity (SVC) vs Forced Vital Capacity (FVC)
Measurement of Forced Vital Capacity (FVC)
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6
Seconds
Liters(BTPS
)
FVC = 5.8 L
Spirometry: How Fast?
• Forced expiratory volume in one second (FEV1)– Reduced with both small lungs (restriction) and with
diseases causing resistance to airflow (obstruction)
• FEV1/FVC ratio– Value < 0.70 defines obstruction
• FEF 25-75– Only important when FVC and FEV1 are normal
– Sensitive to earlier disease “minimal obstruction”
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6
Seconds
Liters(BTPS
)
FEV1 = 4 L
Measurement of Forced Expiratory Volume (FEV1 )
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6
Seconds
Liters(BTPS
)
Spirometric Changes with Increasing Degrees of
Obstruction
Hyperinflation in Emphysema
Spirometry-Quality Control
• Technician dependent• Acceptable effort
– sharp peak
– gradual return to 0 flow
– At least 4 seconds
• 3 acceptable maneuvers within 5% of each other
• Often more easily seen on Flow-volume tracings
Normal/Predicted Values
• Height
• Age
• Gender
• Race– 10% lower in Asian and African than European
descent
Predicted Normal Examples
• 21yo 6’6” male- FVC predicted- 6.9 L– Therefore a measured value of 2.1 L would be
only 30% predicted.
• 80yo 4’10” female- FVC predicted- 1.9 L– Therefore a measured value of 2.1 L would be
111% predicted
Which individual would be most likely to tolerate lung resection?
Spirometry and Detection of DiseaseNormal Values
• FVC 80% of predicted
• FEV1 80% predicted
• FEV1/FVC ratio 0.70
• FEF 25-75 65% predicted– Greater variance in the measurement
Obstruction vs.
Restriction
Obstructive Lung Disease
• FEV1/FVC < 0.70 defines obstruction
• FEV1 usually decreased
• FVC may be decreased – e.g. if expiration incomplete due to air trapping
• If FEF 25-75 decreased and all of the above are normal – “Minimal airways obstruction”
Restrictive Lung Disease
• FVC Decreased
• FEV1 often decreased proportionate to FVC
• FEV1/FVC Normal or Increased
• Can have simultaneous obstruction and restriction
• May need lung volume measurements (RV, FRC, TLC) to confirm.
• Patient retested before and after administration of a beta agonist bronchodilator
• Determines reversibility (asthma)
• 15% and 200ml improvement indicates a positive bronchodilator response
Bronchodilator Response
Bronchial Challenge Testing
• Pulmonary function in the laboratory may not represent the function at the time of symptoms.
• Attempt to mimic condition of symptoms– Work place chemicals– Cold air– Exercise
• Methacholine (histamine derivative) induces bronchospasm in occult asthmatics
• 20% decrease indicates a positive challenge test
Peak Expiratory Flow (PEF)
• Can be obtained during spirometry
• Portable devices can be used to make meaurements at home or in work place
Flow-Volume loops
•same data as volume-time plots but separate graphical representations allow the human eye to recognize patterns.
Normal Obstructed
F-V loops
• The assessment of patient effort on repetitive testing
• The presence of specific patterns for upper airway obstruction
• Specific patterns in other disease processes confirm but add little to spirometry numbers
F-V loops in Upper Airway Obstruction
• Intra vs. Extra-thoracic
• Variable vs. Fixed
Variable Extrathoracic Upper Airway Obstruction
•“inspiratory plateau”
•e.g. glottic tumor
Variable Extrathoracic Upper Airway Obstruction
Intrathoracic Variable Upper Airway Obstruction
•“expiratory plateau”
•e.g. tracheal tumor
Intrathoracic Variable Upper Airway Obstruction
Fixed Upper Airway Obstruction
Measurement of lung volume
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6
Seconds
Liters(BTPS
)
Spirometric Changes with Increasing Degrees of
Obstruction
Hyperinflation in Emphysema
Severe Emphysema (decreased FVC but increased FRC & RV)
Measurement of lung volume
• Helium dilution
• Body plethysmography
Helium Dilution Lung Volume Measurement
Body Plethysmography
Box Pressure
Mouth Pressure
Plethysmographic Determination of FRCPlethysmographic Determination of FRC
Body Plethysmography- Technique
Plethysmography vs. Helium technique
• Plethysmography equipment more expensive and requires more technical expertise
• Helium falsely low in bullous emphysema– Plethysmography measures all air in the chest
including non-communicating bullae; Helium only measures alveoli communicating with the mouth
Measurement of Diffusing Capacity
Diffusing Capacity
• Gas exchange (not ventilation)• Clinically assesses pulmonary capillary bed
in contact with ventilated alveoli• Influenced by
– Capillary volume– Capillary surface area
• Single breath Carbon Monoxide (CO) technique now most common.
Single breath Carbon Monoxide Diffusing Capacity (DlCO)
• Simple/automated
• Standardized normal values available
• 10 second breath hold
• Inspire mixture of CO, He and O2
• Measure change in volume of CO between inspiration and expiration adjusted for dilution effect with He
Single breath Carbon Monoxide Diffusing Capacity (DlCO) Technique
Conditions Lowering Diffusing Capacity
1. Loss of alveolarcapillary membrane• emphysema• pulmonary fibrosis• pulmonary vascular disease
2. alveolar filling diseases• congestive heart failure• pulmonary alveolar proteinosis
3. decreased total lung volume• neuromuscular disease• chest wall deformities• patient post pneumonectomy
Conditions Increasing Diffusing Capacity
• Polycythemia
• Mild congestive heart failure
• Asthma
• Pulmonary hemorrhage.
Thank You