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) Volume b) 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 the lung with a known Volume 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 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

FEV1FVCFEV1/F VC FEF ObstructiveN or RestrictiveN orNN

FEV1/FVC FVC Combined Obstructive FVC Restrictive Normal Yes No YesNo YesNo Further examination Reversibility? Asthma COPD Yes No

Staging in pulmonary function abnormalities %FVCFEV 1FEV1/F VC DLCO Normal> Mild= Medium= Severe<50 40

Reversibility Assessment of postbronchodilator response in obstructive pathologies Spirometry is repeated 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 %FVCFEV 1FEV1/F VC DLCO Normal> Mild= Medium= Severe<50 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

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