Measurement of Lung Function School of Medicine New York University Measurement of Lung Function Beno Oppenheimer, M.D. NYU/Bellevue Medical Ctr. Div. Pulmonary & Critical Care Medicine

Lung Volumes TLC IC TV VC FRC ERV RV Time Vol (L) TLC IC TV VC FRC ERV PIc 3 vol. that are conventional. At 0 flow. FRC balance TLC max insp effort giving sense of stiffness ( compliance) RV at max expirat giving sense of resistance and mostly infl by resistance. RV Time

Spirometry Now we see determinants of RV!!! 3 TLC Vol (L) 1 VC FRC 2 4 Time (s) Flow( L/sec) Now we see determinants of RV!!! 1 4 2 3 TLC FRC RV Vol (L)

Lung Volumes Flows Diffusion Normal Physiology Lung Volumes Flows Diffusion

Determinants of Lung Volumes

Determinants of FRC FRC

Normal Lung Structure

Lung Compliance. Determinant of TLC 120% 100% Normal 80% 60% Lung Volume (% predicted TLC) Palv DV Ppl 40% DP 20% Recoil pressure 0% 10 20 30 40 50 60 70 Transpulmonary Pressure (cm H O) 2 (Palv - Ppl)

Exhaled Volume (liter) Assessment of Airflow 1sec TLC Flow( L/sec) 1 FEV1 2 FVC Exhaled Volume (liter) 3 FRC 4 During exhalation, diameter decr res increases flow decreases in a homogeneous manner with a normal lung. 5 TLC FRC RV FEV1 = 4.0 FVC = 5.0 % = 80 Vol (L)

Determinants of flow Flow = Alveolar Driving Pressure / Resistance Altered driving pressure Lung recoil Muscle strength Altered resistance Size of the airways Number of parallel airways Collapsibility of airway walls P musc P recoil DP Flow = R Remember driving pressure relative to mouth pressure and /or PIP

Increasing # of Parallel Airways Decreases Resistance in Periphery Pedley et. at. Respir Physiol 1970; 9:387 West JB. Respiratory Physiology

Effect of Airway Collapsibility on Flow - + No Flow Inspiration Expiration

Maximal Expiratory Flow – Volume Curve Adapted from West JB. Respiratory Physiology

Effort Independence of Maximal Expiratory Flows (at mid – low lung volumes) FVL powerful tool because even with suboptimal flow, terminal ,loop unafected (caveat, extremely poor effort still problematic) Why does this behavior occur? West JB. Respiratory Physiology

Maximal Airflow at TLC “effort dependent” “driving pressure” 45-0 = 45 “driving pressure” 145-0 = 145 10 10 100 100 20 120 35 135 Palv= 45 Palv= 145 Precoil = 35 Precoil = 35 Pmusc = 10 Pmusc = 100 Volume V V Volume

Maximal Airflow at 50% VC “effort independent” 106 102 Palv= 108 100 Pmusc = 100 Precoil = 8 10 10 “driving pressure” 18-10 = 8 “driving pressure” 108-100 = 8 12 16 Palv= 18 Precoil = 8 Pmusc = 10 Volume V Volume V

Effort Independence of Maximal Expiratory Flows (at mid – low lung volumes) FVL powerful tool because even with suboptimal flow, terminal ,loop unafected (caveat, extremely poor effort still problematic) Why does this behavior occur? West JB. Respiratory Physiology

Diffusion Capacity [CO] i [CO] e

Clinical Application

Emphysema

Maximal Expiratory Airflow Normal Emphysema Low flow, normal VC Role for recoil

Emphysema Effort dependent V Volume Effort independent

Emphysema

Lung Histology Normal Emphysema

Lung Volumes and Diffusion Hyperinflation

Increased Static Lung Compliance 120% Emphysema 100% Normal 80% 60% Lung Volume (% predicted TLC) (high expiratory flow rates) Same DP yields a larger DV = high compliance 40% 20% 0% 10 20 30 40 50 60 70 Transpulmonary Pressure (cm H O) 2

Summary Increased static lung compliance (loss of lung parenchyma → low lung recoil) Increased lung volumes (hyperinflation) Decreased flows (airway collapsibility and reduced recoil) Decreased diffusion capacity

Asthma

Exhaled Volume (liter) Normal Asthma 1sec 1sec TLC TLC 1 1 FEV1 FVC IC IC 2 2 Exhaled Volume (liter) 3 FRC 3 FRC ERV 4 ERV 4 5 5 RV RV RV FEV1 = 4.0 FVC = 5.0 % = 80 FEV1 = 2.13 FVC = 3.11 % = 68

Normal Static Lung Compliance 120% 100% Normal 80% Recoil pressure 60% Lung Volume (% predicted TLC) DV 40% DP 20% 0% 10 20 30 40 50 60 70 Transpulmonary Pressure (cm H O) 2

Narrowed airway Mucus Contracted muscle Inflammation

Effect of Heterogeneity of Disease on Gas Distribution

Effects of Heterogeneity on the Shape of the Maximal Expiratory Flow Volume Curve

Summary Airway Obstruction Decreased flows Air trapping (Increased RV, Decreased ERV) Normal static lung compliance (Normal lung parenchyma) Normal diffusion capacity

Pulmonary Fibrosis

Maximal Expiratory Airflows Normal Fibrosis Lung recoil important for max flow

Pathology Normal Fibrosis

reduced increased reduced

Reduced Static Lung Compliance 120% 100% Normal 80% Lung Volume (% predicted TLC) 60% Pulmonary Fibrosis (high expiratory flow rates) 40% Same DP yields a smaller DV = low compliance 20% 0% 10 20 30 40 50 60 70 Transpulmonary Pressure (cm H O) 2

Summary Decreased static lung compliance (increased lung recoil) Decreased lung volumes Increased flows (in relation to volume: ↑ FEV1/FVC) Decreased diffusion capacity

Normal Asthma Emphysema Pulmonary Fibrosis Flow [l/s] Emphysema Pulmonary Fibrosis

Kyphoscoliosis

PFT’s

Pulmonary Function Tests