Clinical Application of Pulmonary Function Tests
Sevda Özdoğan MD, Prof.Chest Diseases
Pulmonary Function Tests
• Spirometry (SVC)• Flow Volume Curve• MVV• Diffusion test• Reversibility and Provocation tests• Exercise tests
– 6 minutes walking test– Cardiopulmonary exercise tests
A physiological test that measures how an individual inhales or exales volumes of air as a function of time
a) Volumeb) Flow
İndications for PFT
• Diagnostic– To evaluate dispnea!! – To assess the etiology of dyspnea
(cardiac/pulmonary)– To measure the effect of the disease on
pulmonary function– To assess any airway obstruction, the
severity of the obstruction and response to bronchodilators
– To assess prognosis
– To assess preoperative risk– To assess etiology of chronic cough– To assess respiratory muscle strenght– To measure gas diffusion– To monitor for adverse reactions to
drugs with known pulmonary toxicity– Disability/impairment evaluations– Epidemiological or clinical survey
Definitions
• Static Lung Volumes:– Tidal Volume (TV): The volume of gas inhaled
and exhaled during a respiratory cycle (resting)– Expiratory Reserve Volume (ERV): Maximum
volume of gas that can be exhaled from the end expiratory level during tidal breathing
– Inspiratory Reserve Volume (IRV): Maximum volume of gas that can be inhaled from the end inspiratory level during tidal breathing
– Total Lung Capacity (TLC): The volume of gas in lungs after maximal inspiration (Sum of all compartments)
– Vital capacity (VC): Maximal volume of air exhaled from a position of full inspiration
– Residuel Volume (RV): The volume of gas remains in the lung after maximal exhalation
– Functional Residuel Capacity (FRC): The volume of gas present in the lung at end expiration during tidal breathing
• Static lung volumes can be measured by:– Spirometry (SVC maneuver)– Body pletismography
PxV=k– Washout Techniques
• Nitrogen Washout:Based on washing out the N2 from the lungs when the patient breathes 100% O2
– Multipl breath Body pletismography
•Helium dilution:
Based on the equlib-ration of gas in thelung with a knownVolume of gas containing helium
Slow vital capacity
• After 2-3 normal breathing (TV) • Make a slow maksimum inspiration
(TLC)• Then make a slow maksimum
expiration (VC)
• Static Lung volumes are decreased in – Restrictive lung diseases– Atelectasis– Lobectomy, pneumonectomy– Chest wall deformities– Diaphragmatic paralysis– Neurologic pathologies– Hiatus hernia(Normal values are calculated according to the
patients age, height, weight)
• Dynamic Lung Volumes (Flow volume Curve)– Forced Vital Capacity (FVC): is the
maximal volume of air exhaled with maximaly forced effort from a maximal inspiration.
– Forced Expiratory Volume 1 (FEV1): the maximal volume of air exhaled in the first second of forced expiration from a position of full inspiration
• Peak expiratory flow (PEF): The maximum flow rate reached during a forced expiration
• FEF 25-75%: Average expiratory flow over the middle half of FVC (MMEF)
Decreases in small airway obstructions
• Maximum Voluntary Ventilation (MVV): A dynamic test in which the patient breaths rapidly and deeply for 10-15 seconds. The total volume (inhaled and exhaled) is calculated and expressed as L/min)
Decreases in obstructive and restrictive diseases as well as neuromuscular diseases
• Dynamic lung volumes and flow rates are decreased in:– Obstructive lung diseases (COPD,
Asthma)
• İnpiratory parameters are also important especially in upper airway pathologies– MIF; IC; FIV1
FEV1 FVC FEV1/FVC
FEF25-75
Obstructive
N or
Restrictive
N or N N
Yes No
Yes No Yes No
Further examinatio
n
Reversibility?
Asthma COPD
Yes No
Staging in pulmonary function abnormalities
% FVC FEV 1 FEV1/FVC
DLCO
Normal
>80 80 75 80
Mild =79-60
79-60 74-60 79-60
Medium
=59-51
59-51 59-41 59-41
Severe <50 40 40 40
Reversibility
• Assessment of postbronchodilator response in obstructive pathologies
• Spirometry is repeated 15-20 minutes after the administration of an inhaled short acting bronchodilator. An 12-15% increase in FEV1 or an absolute value of 200 ml increase represents a significant positive reversibility test.
Bronchoprovocation test (Challenge)
• Performed in patients who have suspected reactive airway disease with normal spirometry.
• Can be performed by – Methacoline– Histamine– Cold air inhalation?– Exercise
Most frequently
• Methacoline responsiveness:• Starting with a single inhalation at a
very low concentration, patients are tested each time after progresively increasing inhaled doses until– Either a predetermined maximum dose
(16 mg/ml) has been achieved– Or FEV1 has been observed to fall by
20%
CO Diffusion test
• The capacity of the lung to exchange gas across the alveolocapillary interface is determined by DLCO
• This process is a passive diffusion and is a function of– Pressure difference– Surface area – Resistive properties of the membrane
• CO gas is used as the test gas because of its high affinity to hb
Single breath method
Staging in pulmonary function abnormalities
% FVC FEV 1 FEV1/FVC
DLCO
Normal
>80 80 75 80
Mild =79-60
79-60 74-60 79-60
Medium
=59-51
59-51 59-41 59-41
Severe <50 40 40 40
Cardiopulmonary Exercise Testing
• To assess a patients exercise capacity objectively
• To observe the response of the components of oxygen delivery system to this stress
• To determine the factors that limit exercise capacity or cause exertional dyspnea
• Performed on – Treadmill with increasing speeds and
slope– Bicycle pedaled at a constant rate with
a variable resistance• Load is increased in a continious
ramp or at intervals• ECG, Pulse oxymeter, respiratory
rate, Vt, minute ventilation and blood gases are monitored
Parameters measured
• Oxygen consumption (VO2max)• Heart rate• Oxygen pulse• Blood pressure• Ventilation (VEmax)• Anaerobic treshold• Arterial blood gases