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