diagnostic testing

Question 1

measuring FVC
what are we measuring
in what disease processes is this affected

Answer 1

forced vital capacity

1. max volume of gas pt can exhale as forcefully and quickly as possible
2. reduced in both obstructive and restrictive diseases

Question 2

measuring FEV1
def
what its measuring
#s (3)

Answer 2

forced expiratory volume in 1 second
1. volume of air exhaled during the first second of FVC
2. **reflects airflow in large airways
numbers
>2.0 L = little or no obstruction
1.0 <>2.0 L = mild to moderate obstruction
<1.0 L = severe obstruction

Question 3

measuring FEF 25-75v (2)
def
what its measuring

Answer 3

forced midexpiratory flow

1. volume of air exhaled over middle half of FVC / time required to exhale it
2. reflects airflow in small peripheral airways => more sensitive to detecting differences btwn smokers and non-smokers

Question 4

measuring FEV200-1200 (2)
def
what its measuring

Answer 4

forced expiratory flow

1. average expiratory flow during the early phase of exhalation = measuring dead space
2. measures flow for 1L of expired gas immediately following first 200mL of expired gas

Question 5

measuring MVV
what it is
procedure
why we use this

Answer 5

maximum voluntary ventilation

1. max vol of gas a person can move in 1 min
2. ask pt to breathe as rapidly and deeply for 10-15s and extrapolate to 1 min
3. this helps determine how impaired their reserve is because disease drops this number

Question 6

PEF
what it measures
normal #
what abnormal # means

Answer 6

peak expiratory flow

1. max flow that occurs at any point in FVC
2. normal: 9-10 L/ sec
3. decreased peak flow = non-specific mechanical problems in lung

Question 7

peak expiratory flow curve with
restrictive disease
obstructive diease

Answer 7

1. in restrictive disease- much smaller curve due to decrease in volume, but same shape because flow rates are same
2. obstructive disease- similar size curve, slope very different

Question 8

airway resistance (raw) (3)

Answer 8

1. driving pressure necessary to move a vol of gas in a specific pd of time
2. any problem that reduces size of airway causes an increase in airway resistance
3. loss of elastance causes increase in airway resistance

Question 9

administering bronchodilators- what/ when

what it tells us if there is or isnt a change in flow

Answer 9

1. repeat test 5-20m after administration of drug
2. normals and restrictive disease- no difference in flow rates
3. obstructive disease- may se reversibility (>15% improvement)

Question 10

3 factors that limit our diffusion capacity

Answer 10

1. decrease [Hb]
2. increased “thickness” of pulmonary-capillary membrane
3. decreased functional SA available for membrane (ie emphysema)