Clinical Application of Pulmonary Function Tests Sevda Özdoğan MD, Prof. Chest Diseases Pulmonary Function Tests • Spirometry (SVC) A physiological test that • Flow Volume Curve measures how an individual inhales or exales volumes of air • MVV as a function of time a) Volume • Diffusion test b) Flow • Reversibility and Provocation tests • Exercise tests – 6 minutes walking test – Cardiopulmonary exercise tests 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 equlibration 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 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 Obstructive Restrictive FVC FEV1/F VC FEF2575 N or N or N N FEV1/FVC Yes No FVC FVC Yes Combined Further examination No Obstructive Yes Restrictive Reversibility? Yes Asthma No COPD No Normal Staging in pulmonary function abnormalities % FVC Normal >80 Mild FEV 1 80 FEV1/F DLCO VC 75 80 =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 Most frequently Histamine Cold air inhalation? Exercise • 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 Normal >80 Mild FEV 1 80 FEV1/F DLCO VC 75 80 =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 End