Week 4 Prep Vid

What information do pulmonary function tests give us & what is it used for

When are these tests used

Not in emergency patient care - patient already under stress

These are used for ongoing patient care

Spirometer

A devise that measures the volume of air that moves in or out of the lungs

How does a spirometer work

It’s an air filled drum suspended over

Tidal volume

• what is it

• what are normal values

• what varies it

Inspiratory Reserve Volume

• what is it

• what are normal values

• what is its use

• what varies it

Expiratory Reserve Volume

• what is it

• what are normal values

Residual volume (in L and % of total lung capacity (TLC))

1.2L

25% of TLC

Who would have an increased residual volume

Emphysema - due to loss of elastic recoil of the lungs thoracic cavity can’t move down and in like it should during expiration. Air gets trapped and can’t get out - RV goes up

What would cause you to have a decreased residual volume

An increase in the contractility / elastic recoil of the lungs

Lung volume vs capacity

Lung capacity is 2 or more lung volumes added together

Inspiratory capacity

• what is it

• normal value

• formula

The largest volume that can e inspired from resting end expiration

3.5 L

IC = TV (tidal volume) + IRV (inspiratory reserve volume)

Expiratory capacity

• what is it

• normal value

• formula

Forceful expiration after a normal inhalation

1.6L

EP = TV (tidal volume) + ERV (expiratory reserve volume)

Pulmonary vascular resistance is lowest at what point

Functional residual capacity

Functional residual capacity

• what is it

• normal value

• formula

• what percentage of TLC

The volume of gas remaining in the lungs after a normal expiration

2.3 L

FRC = RV + ERV

40% of TLC

How do you measure FRC

Helium dilution method

• hook up patient to spirometer filled with air & known conc. of helium

• patient expires to end of normal expiration

• the volume in the lungs is FRC (V2)

• Let patient breathe in & out until it reaches equilibrium

• A formula is used to estimate V2

Formula to estimate FRC (V2) from helium dilution method for measuring FRC

Vital capacity

• what is it

• normal value

• formula

Volume change between maximal inspiration and maximal expiration

4.8L

VC = IRV (inspiratory reserve volume) + TV (tidal volume) + ERV (expiratory reserve volume)

TLC

• what is it

• normal value

• formula

Total volume of air in lungs after maximal inspiration

5.8L

TLC = VC (vital capacity) + RV (residual volume)

Why can’t you measure TLC with a spirometer

The residual volume can’t be expired

How do you measure TLC

helium dilution technique

What is a vitalograph used to measure

Dynamic changes

Flow rate

Forced vital capacity (FVC) (forceful expiration for 6 seconds after maximal inhalation)

FEV1

Forced expiratory value in 1 second

(the first second on a FVC graph)

What percentage of someone’s FVC is normally expired in the first second (normal range)

75-80%

What is FEV1 used for

Used to characterise lung disease as restrictive / obstructive

Is this a normal curve

Yes

Is this a normal curve

Yes - most air flow at the start of the 6 seconds