Spirometry and Mechanics

Question 1

methods of measuring lung volume

Answer 1

helium-dilution, nitrogen washout, or body plethysmography

Question 2

helium dilution

Answer 2

involves inhaling a known volume and concentration of helium for several minutes until stead state conditions are reached

by measuring the decrease in helium concentration casued by its larger volume of distribution, lung volume can be estimated

Question 3

nitrogen washout technique

Answer 3

the patient breathes 100% oxygen until all the nitrogen in the lungs is washed out

the exhaled volume and nitrogen concentration in that volume are measured

the difference between the initial and final concentrations of nitrogen allows for calculation of lung volume

Question 4

body plethysmography

Answer 4

requires patients to sit inside an air-tight box and breathe through a mouthpiece

lung volume is determined by measuring the change in box volume and pressure during a panying maneuver using Boyle’s Law

Question 5

expiratory obstructive diseases

Answer 5

ex. emphysema, chronic bronchitis, and asthma

may be hyperinflated and trap gas

Question 6

restrictive lung diseases

Answer 6

ex. pulmonary fibrosis, asbestosis

characterized by low lung volumes

lung volume is decreased because of increased elastic recoil pressure

Question 7

FRC

Answer 7

functional reserve capacity

resting lung volume

the volume in the lung at the end of a quiet tidal breath

determined by the inward elastic recoil of lung and the outward elastic recoil of the chest wall

Question 8

IC

Answer 8

inspiratory capacity

IC = TLC - FRC

Question 9

TLC

Answer 9

total lung capacity

the amount of air present within the lungs when they are maximally inflated

Question 10

RV

Answer 10

residual volume

the amount of air present within the lungs when they are maximally deflated

Question 11

ERV

Answer 11

expiratory reserve volume

ERV = FRC - RV

Question 12

IRV

Answer 12

inspiratory reserve volume

IRV = IC - TV

Question 13

TV

Answer 13

tidal volume

amount of air inspired during a quiet breath

Question 14

equation for expiratory flow

Answer 14

Pel/Rus

Pel = elastic recoil pressure

Rus = resistance upstream to the equal pressure point

Question 15

FEV1

Answer 15

the volume can exhale from FVC in the first second of trying

when airflow obstruction is present, this falls more than FVC, which lowers the FEV1/FVC ratio

Question 16

What does normalization of FEV1 and FVC after albuterol in asthma patients mean?

Answer 16

it suggests that asthma patients can have normal pulmonary function when asymptomatic