Chapter 3: Pulmonary Function Testing

Question 1

Define the four lung volumes

Answer 1

Residual Volume (RV): volume remaining in the lungs after a maximal-effort expiration
Expiratory Reserve Volume (ERV): volume of air that can be exhaled with maximal effort from a resting tidal and expiratory level
Tidal Volume (TV or Vt): volume of air that can be inhaled or exhaled with each breath during resting, quiet breathing
Inspiratory Reserve Volume (IRV): volume that can be inhaled with maximal effort inspiration from the tidal end inspiratory level

Question 2

Define the four lung capacities

Answer 2

Total Lung Capacity (TLC): volume of air in the lungs after a maximal effort inspiration, sum of all volumes
Inspiratory Capacity (IC): volume of air that can be inhaled with maximal effort from a resting tidal, end- expiratory level; sum of TV and IRV
Vital Capacity (VC): maximal volume of the air that can be exhaled after a maximal effort inspiration; sum of IRV, TV, ERV
Functional Residual Volume (FRV): volume of gas remaining in the lungs at the end of a normal tidal exhalation (relaxed ventilatory muscles); sum of ERV and RV

Question 3

Calculate the four capacities based on the provided lung volumes.
Given: IRV 2300ml, VT 450ml, ERV 1350ml, RV 1100ml
Calculate FRC,IC,VC,TLC

Answer 3

FRC= 2450ml (sum of ERV,RV)

IC= 2750 (sum of IRV,VT)

VC: 4100ml (sum of IRV,VT, ERV)

TLC= 5200ml (sum of all volumes)

Question 4

Discuss methods of indirectly measuring FRC and RV

Answer 4

• helium dilution
• nitrogen washout
• body plethysmography

Question 5

State normal body temperature in degrees Celsius and Fahrenheit, and state the effects of temperature on the ability of gas to carry liquid.

Answer 5

Body temp: 37C, 98.6F

As gas temperature increases so does the gas’s ability to care humidity increase

Question 6

State the value for vapor pressure of water in a thoroughly saturated sample of gas at body temperature

Answer 6

BTPS humidity is 44 mg/l and produces a pressure of 47 mm Hg (PH2O)

Question 7

Discuss the utility of FVC, FEVt, and FEV1/FVC

Answer 7

These are used to determine if the patient has normal lungs, restrictive or obstructive lung disease

Question 8

Categorize normal, obstructive, and restrictive disease patterns based on PFT results

Answer 8

• Airway obstruction
-reduced FVC
-reduced FEV1
-reduced FEV1/FVC ratio

• Restrictive disease
-reduced FVC
-FEV1 normal to reduced
-FEV/FVC ratio normal or increased

Question 9

Patient has the following PFTs
FVC 75% predicted
FEV1 60% predicted
FEV1/FVC 58% predicted
What is the interpretation

Answer 9

Obstructive

Question 10

Identify obstructive and restrictive patterns from a flow-volume loop

Answer 10

Obstructive is like an ice-cream scoop (VC small and concave)
Restrictive is much smaller and narrow (VC shorter and narrower)

Question 11

Discuss how MIP, MEP, and RSBI can be useful in determining a patients ability to breathe spontaneously

Answer 11

-MIP normally -90 or more negative for women and even more negative for men. Critical value is -20. If patient cannot generate at least -20 cwp of vacuum, they are not likely to be able to maintain spontaneous breathing

-Egan’s (-) 20 - (-) 30 cwp. -25

-RSBI normal is 20-35. The critical value is 105. If the RSBI is greater than 105 it is unlikely the patient will be able to maintain spontaneous ventilation. The higher it goes, the less likely. Under 105, the lower it gets, the more likely the patient can maintain spontaneous ventilation

-MEP. Normal is greater than 100 cwp. When this value becomes less than 50 cwp the patients cough is impaired and the patient may not be able to maintain adequate airway clearance. We may want to institute airway clearance therapy.