Pulmonary fxn test

Question 1

Forced Vital Capactiy (FVC)

Answer 1

• the maximal amount of air that can be exhaled forcibly and completely after maximal insipration
• normal adult: 3-5 Liters (up to 6 L in a tall, young male)
• lower in women, lower as we age (vital capacity decreases 200 - 250 cc per 10 yrs after ~ age 20)

Question 2

Forced Expiratory Volume in one second (FEV1)

Answer 2

• measures how much air a patient can “blast out” in first second of forceful expiration
• normal: 75-80% of their FVC is exhaled in first second (majority of FVC can be exhaled in 3 seconds)

Question 3

FEV1/FVC Ratio

Answer 3

• used to determine if the pattern of spirometry is obstructive, restricive, or normal
• normal: >0.80

Question 4

Tidal Volume (TV)

Answer 4

• volume of air inhaled or exhaled w/ each breath with “quiet breathing” (breathing at rest)
• normal adult male: 500 mL at rest
• normal adult female: 400 mL at rest

Question 5

Inspiratory Reserve Volume

Answer 5

• max amount of air forcefuly inhaled after normal inhalation

Question 6

Expiratory Reserve Volume

Answer 6

• max amount of air forcefully exhaled after normal inspiration and expiration

Question 7

Residual Volume (RV)

Answer 7

• amount of air left in lungs after max exhalation

Question 8

Total Lung Capacity (TLC)

Answer 8

• total amount of air the lungs can hold; it is the sum of all the volume components after maximal inhalation

Question 9

Preditcted values

Answer 9

• preloaded into machine (or can be looked up on tables), so that the pt’s values are automatically compared to a cohort of individuals w/out lung impairment of the same gender, age, height (and sometimes race)

Question 10

Obstructive dz/pattern

Answer 10

• dz state
  
  • disease states characterized by increased airway resistance to expiratory flow, pt struggles to get air out quickly
• clinical characteristics
  
  • dyspnea, cough, wheezing
• spirometry results
  
  • defined by low FEV1/FVC ratio (<0.7)
• severity of restriction
  
  • severity of obstruction classified by reduction in FEV1 expressed as a percent

predicted FEV1

• examples
  
  • COPD, asthma, cystic fibrosis
• Residual Volume
  
  • elevates
• TLC
  
  • normal or elevated

Question 11

restrictive dz/ pattern

Answer 11

• dz state
  
  • disease states that restrict lung expansion and are characterized by loss of lung volume
  • dec in compliance & elasticity and harder for lungs to force air out quickly
• clinical characteristics
  
  • dyspnea, cough
• Spirometry results
  
  • defined by low lung volumes - both FVC and FEV1 are reduced, thus the FEV1/FVC ratio remains normal
• Examples
  
  • intrinsic lung parenchyma”, i.e. interstitial lung diseases
  • “extrinsic lung parenchyma,” i.e. chest wall abnormalities
  • neuromuscular diseases affecting diaphragm (scoliosis, ALS, Guillain-Barre)
• Residual Volume
  
  • decreased
• TLC
  
  • decreased (the lower the percent predicted TLC, the more severe the restrictive

impairment)

* Demonstration of reduced TLC is the GOLD STANDARD for the Dx of restrictive lung
* disease it both adults and children

Question 12

What is a PFT

Answer 12

• provides quantitative data on a pt’s lung fxn as method of initially evaluating / diagnosing & subsequently monitoring resp disease states
• Includes spirometry, static lung volume measurement, diffusing capacity measurement

Question 13

PTF indication

Answer 13

• aid in eval of on-going pulm signs & Sx, usu chronic dyspnea or chronic cough
• monitor known pulm disease severity / progression or response to Tx
• provide pre-operative assessment of lung fxn prior to major surgery, esp. throacic surgeries
• screen pts @ high risk of COPD
• aid in diagnosing the development of pulm toxicity w/ drug or enviornmental / occupational exposures

Question 14

Bronchodilator Responsiveness

Answer 14

• use 2-4 MDI inhlations of short-acting beta-agonist (albuterol) via a valve holding chamber
• post-bronchodilator is performed after an appropriate delay for the bronchodilatory used to work (10-20 min)
• if either the FEV1 of the FVC increases by @ least 12% and @ least 200 mL = pt has “a significant bronchodilator response” or “bronchodilator reversibility”
• reversibility argues in favor of asthma as a diagnosis (less response = COPD)

Question 15

what is spirometry ?

Answer 15

• measures air moving in and out of lungs during various resp maneuvers
• determines how much air can be moved (volume) and how fast (flow rates)
• most common, simplest PFT
• Pros: easily obtainable w/ office machine, inexpensive, widely available, can be done pre /post short-acting bronchodilator administration if desired
• Cons: requires pt cooperation and “good effort” to get reliable results
• Dx and monitoring of COPD is the single most common reason for spirometry

Question 16

how does spirometry work?

Answer 16

• Pt takes deep breath and blows as hard as possible in a tube while the technician monitors and encourages the patient during the test. The machine records the results of the exam.
• Measures: FVC, FEV1, FEV1/FVC ratio

Question 17

spirometry results

Answer 17

• It CANNOT diagnose a specific disease state on its own, but abnormal values can be helpful clue in accurate Dx
• Obstructive Disease
  
  • defined by low FEV1/FVC ratio (<0.7)
• Restrictive disease
  
  • defined by low lung volumes: both FVC and FEV1 are reduced, thus the FEV1/FVC ratio remains normal

Question 18

Lung Plethysmography

Answer 18

• Gold Standard for measurement of lung volumes, particularly in significant airflow obstruction; diagnosis of restrictive resp disease in both adults & children
• alternative methods include helium dilution, nitrogren washout, measurements based on chest imaging (helium dilution & nitrogen washout may underestimate lung volume in pts w/ moderate to severe COPD bc they do not access under or nonventilated areas)

Question 19

how does Lung Plethysmography work?

Answer 19

• utilizes a “body box” to determine lung volumes
• pt sits in an air-tight booth in which the pressure is measured as he or she breathes
• uses Boyle’s law (states that the product of pressure and volume remains constant in a closed system)
• Measures: RV, TLC, FRC

Question 20

Lung Plethysmography results

Answer 20

• Elevated RV
  
  • “air trapping”
  • obstructive lung disease
• Decreased RV
  
  • resctrictive lung disease
  • Normal or Increased TLC
  • obstructive disease
• Decreased TLC
  
  • restricted lung disease
  • the lower the percent predicted TLC, the more
  • severe the restrictive impairment

Question 21

Diffusing Capacity of Carbon Monoxide (CO)

Answer 21

• measure of the ability of the lungs to transfer gas; used as a surrogate for oxygen diffusion capacity

Question 22

how does Diffusing Capacity of Carbon Monoxide (CO) work?

Answer 22

• pt breathes in fixed small amount of carbon monoxide in a single deep breath & calculates how much diffuses into the blood by measuring how much is breathed back out
• ideal diffusion occurs when SA for gas transfer is high & the blood is readily available to accept the gas being transferred

Question 23

Diffusing Capacity of Carbon Monoxide (CO) results?

Answer 23

• Decreased
  
  • diminished surface area of lung (i.e. emphysema)
  • increased thickness of alveolar-capillary membrane (i.e. pulm fibrosis)
  • diminished perfusion of ventilated areas (i.e. pulm embolism)
  • diminished hemoglobin concentration (i.e. anemia)
• Increased
  
  • polycythemia
  • pulm hemorrhage

Question 24

obstructive vs restrictive

Answer 24

Question 25

Spirometry graph

Answer 25