Lungs volume and testing

Question 1

Long compliance =?

Answer 1

stretchiness

Question 2

At high pressure the lung is stiffer and less compliant

Answer 2

TRUE!

Question 3

Lung bases are more compliant

Answer 3

TRUE!

Question 4

What is compliance ensured by?

Answer 4

Elastic recoil

Question 5

Give an example of decreased compliance?

Answer 5

Pulmonary fibrosis and alveolar oedema

Question 6

Give an example of increased compliance?

Answer 6

Normal ageing lung - elastic recoil is compromised

Question 7

Total lung compliance is dependent on what?

Answer 7

Thoracic cage and elasticity

Question 8

For efficient ventilation, healthy people tend to have

Answer 8

High lung compliance

Low alveolar surface tension due to surfactant

Question 9

List the three things tests need to assess for lung function

Answer 9

Mechanical condition (pul. fibrosis - condition of compliance)
Resistance of airways (asthma - obstructive deficit)
Diffusion across alveolar membrane (pul. fibrosis - gas transfer)

Question 10

What is the normal tidal volume?

Answer 10

0.5l

Question 11

What is the equation for vital capacity?

Answer 11

TV+IRV+ERV

Question 12

What is the equation for the functional residual capacity?

Answer 12

(amount of air that remains in the lungs at the end of a normal expiration)
ERV+RV (residual volume)

Question 13

What is the equation for total lung capacity and what is the normal value?

Answer 13

VC+RV

7.3l

Question 14

Forced Vital Capacity (FVC) - total volume exhaled - what kind of deficit and what does it indicate?

Answer 14

Restrictive deficit and indicates the compliance

Question 15

FEV1.0 - volume expired in the first second

Answer 15

Typically >70%

Obstructive deficit and indicates the lung function

Question 16

List physiological and environmental factors affecting lung volumes

Answer 16

Smoking, age, weight, exercise, living at high altitude, sex

Question 17

What is used instead of a spirometer to measure FRC, TLC or RV?

Answer 17

Helium dilution or nitrogen washout

Question 18

Why do we use helium?

Answer 18

Is not absorbed by the body

Question 19

List the procedure for nitrogen washout

Answer 19

Patients inspires 100% oxygen
Expires into spirometer system, N2 meter detects N in expired air
As no. of breaths increases, N2 conc, decreases - O2 replaces the N2
Procedure repeats till N2 is replaces
FRC calculated from exhaled N2 and estimated alveolar N2

Question 20

What happens in a restrictive deficit?

Answer 20

Lung expansion compromised
Lungs don’t fill to capacity - e.g. pulmonary fibrosis and scoliosis
FVC IS REDUCED BUT FEV1 IS RELATIVELY NORMAL
FEV1/FVC remains relatively normal

Question 21

What happens in a obstructive deficit

Answer 21

Airway obstruction 
Can still fill to capacity 
Resistance is increased on expiration - e.g. asthma and COPD 
FEV1 IS REDUCED BUT FVC WILL BE NORMAL 
A LOW FEV1/FVC WILL BE REDUCED

Question 22

Peak Expiratory Flow Rate (PEF) - what is it?

Answer 22

Fully expanded lungs - airways are widest and flow is maximum - it reaches a plateau (means no matter how much they breathe out the flow rate will be unaffected)
Flow falls and ceases at RV

Question 23

TLC –> PEF

Answer 23

Is EFFORT dependent - incr. effort increases flow rate

Question 24

PEF–>RV

Answer 24

Is effort INDEPENDENT - incr. effort DOES NOT increase flow rate

Question 25

PEF–>RV

Answer 25

Is effort INDEPENDENT - incr. effort DOES NOT increase flow rate

Question 26

What is the normal flow rate? and normal TLC?

Answer 26

11 and 7

Question 27

How do you measure diffusion conductance

Answer 27

Measure CO crossing alveolar air to blood - higher affinity to haemoglobin.
Patient inhales single breath of dilute CO followed by holding breath for 10 secs
DIFFUSION CAPACITY is calculated from the lung volume and the % of CO in the alveoli at the beginning and end of 10s breath hold
Fibrosis - diffusion is compromised