Lung Volumes and Gas Distribution

Lung Volumes and Gas Distribution - Report Interpretation RET 2414L Pulmonary Function Testing Module 3.0

Lung Volumes / Gas Distribution • Lung Volumes • The most significant volumes for evaluating the effects of pulmonary disorders are VC, FRC, RV, and TLC

Lung Volumes / Gas Distribution • RV and TLC Determination • Determination of RV and TLC are based on the FRC from indirect spirometry and volumes measured during direct spirometry RV = FRC – ERV or RV = (FRC+IC) - VC TLC = FRC + IC or TLC = (FRC – ERV) + VC

Lung Volumes / Gas Distribution • Lung Volume Changes • Restrictive patterns • Obstructive patterns Demonstrate reductions in ALL lung volumes Demonstrate increases in only some lung volumes Exception: VC may be normal or even decreased

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Obstructive Pattern • Increase FRC is considered pathologic • FRC values >120% of predicted represent air trapping • Emphysematous changes • Obstruction caused by asthma or bronchitis

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Obstructive Pattern • Increased RV often results in a equivalent decrease in VC • Increased RV is characteristic of: • Emphysema • Bronchial obstruction • RV and FRC usually increase together

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Obstructive Pattern • As RV becomes larger, increased ventilation is needed to adequately exchange O2 and CO2 • Requires increased VT and/or respiratory rate • Work of breathing is increased • Often display hypoxemia or CO2 retention

Lung Volumes / Gas Distribution • Obstructive Pattern • Two types of obstructive patterns • Increases in RV with a proportional reduction in VC; TLC remains constant (normally 80-120% of Predicted) • Air Trapping

Lung Volumes / Gas Distribution • Obstructive Pattern • Two types of obstructive patterns • RV increases with little or no change in VC; TLC increased proportional to RV • (TLC >120% of predicted) • Hyperinflation

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Restrictive Pattern • FRC, RV and TLC typically decreased • Usually lung volumes are decreased equally • When TLC is <80% a restrictive process is present • RV/TLC is relatively normal

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Restrictive Pattern • Asbestosis • Sarcoidosis • Complicated silicosis • Neuromuscular disorders • Respiratory depression • Diaphragmatic paralysis • CHF

Lung Volumes / Gas Distribution • Significance/Pathophysiology • Restrictive Pattern • Kyphoscoliosis • Obesity • Pleural effusion • Pneumonia • Tumor • Atelectasis • Surgical excisions

Lung Volumes / Gas Distribution • RV/TLC Ratio • Describes the percentage of total lung volume that must be ventilated by tidal breathing

Lung Volumes / Gas Distribution • RV/TLC Ratio • The RV/TLC ratio also known as RV/TLC% and is expressed as a percentage RV/TLC% = RV x 100 TLC • In normal, young, healthy adults, the RV/TLC% ranges between 20% and 35%

Lung Volumes / Gas Distribution • TLC and RV/TLC Ratio • RV/TLC% >35% + Normal TLC = • RV/TLC% >35% + >Normal TLC = AIR TRAPPING HYPERINFLATION

Lung Volumes / Gas Distribution • Lung Volume Changes Patterns of Lung Volume Changes Volume Restrictive Air Trapping Hyperinflation TLC  N  VC   N FRC    RV    RV/TLC% N  

Case 3 – 1 History M.B. is a 27-year-old male high school teacher whose chief complaint is dyspnea on exertion. He states that his breathlessness has worsened over the past several months. He has smoked one pack of cigarettes per day for 10 years (10 pack years). He denies a cough or sputum production. No one in his family ever had emphysema, asthma, chronic bronchitis, carcinoma, or tuberculosis. There is no history of exposure to extraordinary environmental pollutants.

Case 3 – 1 Personal Data Sex: Male Age: 27 yr Height: 65 in Weight: 297 lb Body surface area (BSA): 2.28 M2

Case 3 – 1 Spriometry and Airway Resistance Predrug Pred %Pred FVC (L) 2.90 4.7 62 FEV1 (L) 2.47 3.86 64 FEV1% 85 82 - FEF 25%-75% 4.62 4.35 106 FEF 50% 4.94 5.82 85 MVV (L/M) 178 130 137 Raw 2.33 0.6-2.4 SGaw 0.23 0.12-0.50

Case 3 – 1 Lung Volumes by (plethysmograph) Predrug Pred %Pred VC (L) 2.90 4.7 62 IC (L) 1.96 2.91 67 ERV (L) 0.94 1.8 59 FRC (L) 1.87 3.29 57 RV (L) 0.93 1.49 57 TLC (L) 3.83 6.2 62 RV/TLC% 25 24

Case 3 – 2 History R. B. is a 37-year-old pipe fitter whose chief complaint is shortness of breath at rest and with exertion. His dyspnea has worsened in the past 6 months, so much so that he is no longer able to work. Additional symptoms include a dry cough. He admits some sputum production when he has a chest cold. He has smoked one pack of cigarettes per day for 19 years (19 pack years). He quit smoking approximately 3 weeks before the tests. His father died of emphysema, and his mother of lung cancer. His brother is in good health. His occupational exposure includes working for the past 13 years in the assembly room of a boiler plant. He admits to seldom using the respirators provided at work despite a dusty environment.

Case 3 – 2 Personal Data Sex: Male Age: 37 yr Height: 69 in Weight: 143

Case 3 – 2 Spirometry Predrug Pred %Pred Postdrug %Pred % FVC (L) 3.04 5.05 60 3.10 61 2% FEV1 (L) 2.03 3.90 52 2.26 58 11% FEV1% 67 77 - 73 - FEF 25%-75% 1.3 4.09 32 1.60 39 23% FEF 50% 2.12 5.78 37 2.42 42 14% FEF 25% 0.78 2.95 26 1.2 41 54% MVV (L/M) 83 141 59 91 65 10% Raw 2.51 0.6-2.4 - 2.47 - SGaw 0.14 0.11-0.44 0.15 -

Case 3 – 2 Lung Volumes (by N2 Washout) Predrug Pred %Pred VC (L) 3.04 5.05 60 IC (L) 1.62 3.18 51 ERV (L) 1.42 1.87 76 FRC (L) 2.75 3.81 72 RV (L) 0.33 1.94 69 TLC (L) 4.37 6.99 63 RV/TLC% 30 28 -

Lung Volumes and Gas Distribution - Report Interpretation