Measuring lung function

Question 1

Tidal volume

Answer 1

The amount of air inspired and expired during quiet breathing

500 ml

Question 2

Dead space

Answer 2

The volume of air inspired that does not undergo gaseous change.

150/500ml

Question 3

Total minute ventilation

Answer 3

The volume of air inhaled and exhaled in a minute.

This is 6L/min.

Question 4

Generations of conducting zones in the airway

Answer 4

1-16
Do not contain alveoli

Composed of trachea, bronchi, bronchioles.

1-4 are cartilaginous

Question 5

Respiratory zones

Answer 5

Zones 17-22

Question 6

23rd generation

Answer 6

The end of the respiratory tract- the alveoli

Question 7

Pneumotachograph

Answer 7

A piece of equipment that measures flow and converts it to volume.

Question 8

Inspiratory reserve volume

Answer 8

The maximal amount of air forcefully inhaled above normal inspiration.

Question 9

Expiratory reserve volume

Answer 9

The maximum amount of air exhaled above normal expiration.

Question 10

Residual volume

Answer 10

The amount of air left in the lungs after maximum expiration

Question 11

Tidal volume

Answer 11

The amount of air inspired and expired during quiet breathing.

Question 12

Functional residual capacity

Answer 12

The amount of air left in the lung after normal expiration.

Question 13

Total lung capacity

Answer 13

The maximum amount of air that can be inspired in the lung.

TLC= VC +RV

Question 14

Vital capacity

Answer 14

The amount of air that can be expired after the deepest inspiration.

VC= IRV+TV+ERV

Question 15

FEV1

Answer 15

FEV1

The volume of air expired forcefully at the end of the first second.

Question 16

FEV1/ FVC ratio

Answer 16

The ratio between the volume of air expired forcefully at the end of the first second compared to the total volume of air expired forcefully.

Normal value> 70%. If it is less than this, then obstruction in the airway is present.

Question 17

FVC

Answer 17

Forced vital capacity

The amount of air expired forcefully after the deepest breath.

Normal value is >80% of predicted FVC, according to general data.

Normal data is made from averaging gender, age, race, height.

Question 18

Albuterol

Answer 18

Bronchodilator that is used in asthmatic patients.

Question 19

Using spirometry to measure responsiveness to albuterol

Answer 19

1. The FEV1 is taken using the spirometer and recorded.
2. Albuterol is then administered to patient and FEV1 is measured 15 minutes later.
3. An increase in FEV1 by 12%/ 200 mL indicates reversible obstruction.

Question 20

Spirogram

Answer 20

Gram plotted from a spirometer to show the change in volume over time.

The first second will show the FEV1 value.
The graph should plateau after a few seconds due FVC being reached.

Question 21

Flow-volume loop

Answer 21

A graph plotted from a spirometer that shows flow (L/sec) in expiration and inspiration, against time.

The graph is read from the left on the x axis, in an anticlockwise direction.

TLC is when volume and rate is 0 at the end of expiration.
Volume at the end of inspiration is the residual volume.

Question 22

Effort and flow rates during expiration

Answer 22

It is important to ensure that the patient takes a full deep breath before blowing into spirometer.

Question 23

Effort-dependant phase

Answer 23

During flow rate measurements, this is when increasing effort, increases flow rates.

Decreasing effort and increased resistance decreases flow rate.

Question 24

Effort-independant phase

Answer 24

This is when despite increasing effort whilst measuring the peak expiratory flow rate, there is no change in flow rate.

This is due to airway resistance

Question 25

Peak expiratory flow rate

Answer 25

A measurement that shows volume of air forcefully expired in L/min. PEFR is the lowest in the morning for everyone. There is a wide variation in PEFR shown in asthmatics compared to healthier people. This is combated through- anti-inflammatory treatments and long acting beta agoinsts

Question 26

Salmeterol

Answer 26

Long acting beta-2 agonist used by asthmatics which is used to prevent asthmatic symptoms and control COPD symptoms

Question 27

Effort independent flow

Answer 27

Occurs when an increase in effort doesn't increase the flow rate. Due to airway resistance dropping the pressure of air from alveoli to the mouth. When pleural pressure exceeds alveolar pressure during expiration, this narrows the airway and creates greater resistance. Therefore since there is no cartilage to resist collapsing, the airway can collapse.

Question 28

Alveolar pressure

Answer 28

Alveolar pressure= pleural pressure + elastic recoil

Question 29

Equal pressure point

Answer 29

In cartilage free-bronchioles, this is when the intrapleural pressure is equal to the alveolar pressure. Cartilage-free bronchioles act as starling resistors therefore when intrapleural pressure exceeds alveolar pressure, resistance is increase in the bronchioles. Increased effort will increase alveolar pressure and pressure at the EPP but pressure difference and flow in unchanged.

Question 30

Variable intrathoracic large airway obstruction

Answer 30

An airway lesion in the thoracic trachea. Inspiration peaks but expiration does not. During inspiration the trachea is pushed outwards as the tracheal pressure exceeds pleura pressure. BUT during expiration, the trachea is pulled inwards due to the pleural pressure exceeding the tracheal pressure. This increases resistance and is why there is no peak during expiration.

Question 31

Variable large extrathoracic airway obstruction

Answer 31

Occurs when there is a lesion in the trachea, in the extrathoracic region. During inspiration, atmospheric pressure exceeds tracheal pressure, which pulls trachea inwards. This increases resistance in trachea and narrows airway. Whereas during expiration, tracheal pressure exceeds atmospheric pressure which pushes trachea outwards- hence why obstruction is variable

Question 32

Methacholine test

Answer 32

Tests for a hyperactive airway response. Spirometry test is taken to record FEV1. Methacholine is administered with the dose increased every 5 minutes. If there is a positive test result- a DECREASE in FEV1 by 20 % is seen, indicating a hyperactive airway- easily triggered bronchospasm

Question 33

What lung volumes are reduced in restrictive airway conditions?

Answer 33

Residual volume Functional residual capacity Total lung capacity This reduction can be determined by measuring TV, ERV and IRV to indirectly calculate FRC, TLC and RV.

Question 34

Methods of measuring lung volumes

Answer 34

Plethysmography- body box P1V1= P2V2 P1- alveolar pressure at the mouth at FRC V1= FRC ``` P2= Alveolar pressure during inspiratory effort against closed shutter V2= FRC + change in the volume of the box ```

Question 35

Conditions that show decreased lung volumes?

Answer 35

Pleural disease Chest wall disease Lung parenchymal process/ airspace filling process- expansion of the interstitial space due to water, scarring/inflammation. Weakness of the lung- Nerve/ muscle based Focal/ global

Question 36

Pathologies that show elevated lung volumes

Answer 36

Emphysema- increased lung compliance and FRC Hyperinflation- COPD Air trapping

Question 37

Hyperinflation

Answer 37

Increased TLC volume

Question 38

Air trapping

Answer 38

Increased residual volume. Seen in when airway, especially bronchioles collapse and is unable to expel air. Therefore there is more air left in the lungs after ex

Question 39

Diffusing capacity

Answer 39

Measurement of how well gases diffuse across alveoli. Measurement= CO transfer factor. Patients perform a breath hold with an inhaled gas that is diffusion-limitted. Amount of diffusion= inspired CO- expired CO. Gives DLCO

Question 40

Factors that affect gas exchange

Answer 40

The alveolar surface area- increase SA increases GE Thickness of respiratory membrane- increased thickness decreases GE

Question 41

DLCO

Answer 41

Diffusion capacity- the extent to which O2 passes from the alveoli into the blood.

Question 42

Pulmonary conditions that show reduced DLCO

Answer 42

Emphysema Lung infiltration Lobectomy

Question 43

CV and haematological conditions that reduces DLCO

Answer 43

Pulmonary hypertension Low CO Pulmonary oedema Anaemia

Question 44

Effect of polycythemia on DLCO

Answer 44

Increases- more O2 in blood

Question 45

Effect of pulmonary haemorrhage on DLCO

Answer 45

Increases- more O2 in lungs due to blood in lunds.