Pulmonary Function Testing PDF

PULMONARY FUNCTION TESTING Tamethia Perkins MS, RRT-NPS, RRT-ACCS RT 3005/6005 LUNG VOLUMES AND CAPACITIES ◼ LUNG VOLUMES ◆ VT ◆ IRV ◆ ERV ◆ RV Lung Volumes LUNG CAPACITIES ◼ VC= Vol of air exhaled after a maximal inspiration. (IRV+VT+ERV)....

PULMONARY FUNCTION TESTING Tamethia Perkins MS, RRT-NPS, RRT-ACCS RT 3005/6005 LUNG VOLUMES AND CAPACITIES ◼ LUNG VOLUMES ◆ VT ◆ IRV ◆ ERV ◆ RV Lung Volumes LUNG CAPACITIES ◼ VC= Vol of air exhaled after a maximal inspiration. (IRV+VT+ERV). ◆ Slow VC (SVC) ◆ Forced VC (FVC) ◼ IC= Vol inhaled after a normal exhalation. (IRV+VT) ◼ FRC= Vol remaining after normal exhalation. (ERV+RV) ◼ TLC= Max amount of air lungs can accommodate. ◼ RV/TLC ratio. Normal values Obstructive vs. Restrictive PULMONARY MECHANICS ◼ FVC ◆ Max volume of gas exhaled forcefully and rapidly after a max inspiration. FEVT ◼ Max vol of gas exhaled over a specific period of time. ◼ Most common time period: 1.0 sec ◼ Normal values @ ◆ FEV0.5, 60% ◆ FEV 1.0, 83% ◆ FEV 2.0, 94% ◼ In obstructive diseases, FEVT decreases. FEVT FEV1/FVC ratio ◼ Decreased indicates obstruction ◼ Increased indicates restriction FEF 200-1200 ◼ Average rate of airflow between 200 and 1200mL of the FVC. ◼ Index of integrity of large airways. ◼ Average: 8L/sec (480 L/min) MALE 5.5 L/sec (330 L/min) FEMALES ◼ FEF decrease with age and in obstructive disease. FEF FEF 25%-75% ◼ Average flow rate during the middle 50% of the FVC. (N= 270L/min – 210 L/min) ◼ Reflects status of medium to small airways. ◼ Decreases with age and in obstructive disease. FEF 25-75 FEF 25%-75% PEFR ◼ Maximum flow rate that can be achieved. ◼ Can be obtained from the FVC. ◼ Average is 600 L/min – 450 L/min. ◼ Decreases with age and in obstructive disease. FEF 25-75 MMV ◼ Largest vol of gas breathed voluntarily in 1 minute. ◆ Test is done over 12-15 seconds. ◼ Evaluates performance of respiratory muscles, compliance, and R generated by the airways and tissues. ◼ Average 170 L/min – 110 L/min. ◼ Decreases with age and in obstructive disease. MMV FLOW-VOLUME CURVE ◼ Graphic representation of FVC followed by a forced inspiratory volume. ◼ Measurements that can be obtained from the flow-volume loop: ◆ PEFR ◆ PIFR ◆ FVC ◆ FEVT ◆ FEF25%-75% ◆ FEF50% F-V Loop Obstructive vs. Restrictive Flow Normal Values COMPONENTS OF F-V LOOP ◼ Effort-dependent portion of FEV maneuver: first 30% (resp. muscles). ◼ Effort-independent portion: 70%. Analysis of Flow/Volume Loops Lung Volumes (indirect) ◼ TLC ◼ RV ◼ FRC ◼ RV/TLC% tells us how much of the RV is taking up the TLC >35% is bad…why…airtrapping/hyperinflation DYNAMIC COMPRESSION OF THE AIRWAYS ◼ Flow limitation during last phase of FVC due to dynamic compression of the walls of the airways. ◼ During passive exhalation, P within the airways drops to zero. ◼ During forced exhalation, P within the airways equals the pleural P surrounding the airways @ equal P point. ◼ At this point airways are compressed. Dynamic Compression Interpretation ◼ Obstructive ◆ Can get in in but has trouble getting it out. (air trapping) ◼ Restrictive ◆ Can get it out, but cannot get it in (small lung (ie lung volumes)) More Simple interpretation ◼ Obstructive ◼ Restrictive ◆ Decreased flow ◆ Decreased vol ◆ FEV1 ◆ FVC ◆ FEV1% ◆ FEV1% increased ◆ FEF 200-1200 ◆ Reduced lung vol ◆ FEF 25%-75% ◆ FEF Max (PEFR) ◆ Increased lung vol Diseases ◼ Obstructive ◼ Restrictive ◼ C ◼ Basically everything ◼ B else ◼ A ◼ B ◼ E ◼ Epiglottitis ◼ Croup  DIFFUSION CAPACITY OF CARBON MONOXIDE (DLCO) ◼ Measures the amount of CO (diffusion-limited gas) across the ACM. ◼ CO has an affinity for Hgb 210 greater than that of O2. ◼ CO single-breath technique. ◼ Normal DLCO is 25 mL/min/mm Hg. ◼ Decreased in emphysema or any disease process that affects the integrity of the ACM. Interpretation Comparison ◼ FVC (L)4.71 2.94 ◼ FVC (L)4.71 3.34 62% 71% ◼ FEV1 (L)3.551.21 ◼ FEV1 (L)3.55 3.01 34% 85% ◼ FEV1/FVC 76 ◼ FEV1/FVC 76 44% 90% ◼ RV/TLC% 36 ◼ RV/TLC% 36 51% 32%