Spirometry

Question 1

What are spirometry tests used for?

Answer 1

To detect abnormalities of measurements of flow and volumes during inspiration and expiration (respiratory disorders can alter mechanical properties of resp system).

Question 2

What is a spirometry test?

Answer 2

A basic test to start the journey of discovering resp disorders.
-spirare- to breathe
-metrai- measuring

Question 3

What does spirometry measure?

Answer 3

Measures ventilatory function by measuring the volume of air that can be breathed out and how quickly you can breathe it out, most common test.

Question 4

What are the indications for spirometry?

Answer 4

-medical diagnosis
-surgery
-disability evaluation
-research

Question 5

What does medial diagnosis include as an indication?

Answer 5

Measure effects of disease on resp function, follow course of a disease, evaluate signs and symptoms, physical fitness, reassure patient.

Question 6

What does surgery include as an indication?

Answer 6

Preoperative risk evaluation for anaesthetic and surgery, postoperative assessment of surgery (thoracic).

Question 7

What does disability evaluation include as an indication?

Answer 7

Industrial medical assessment (asbestos), gov compensation laws, personal injury lawsuit and other legal purposes (failure to provide a breath test).

Question 8

What does research include as an indication?

Answer 8

Clinical trials (lung function over time/ age), epidemiological studies.

Question 9

What is volume measured in?

Answer 9

Litres.

Question 10

What is flow measured in?

Answer 10

Volume/ Time (litres per second or litres per minute).

Question 11

What is tidal volume?

Answer 11

The volume of gas expired or inspired during one breath cycle (normal breathing).

Question 12

What is inspiratory capacity?

Answer 12

Maximum volume of gas the can be inspired from the position of functional residual capacity (from bottom of normal breathing/ tidal volume to breathing until full).

Question 13

What is inspiratory reserve volume?

Answer 13

Maximum volume of gas that can be inspired from the position of end inspiratory tidal volume (top of tidal volume).

Question 14

What is functional residual capacity?

Answer 14

Volume of gas in lungs and airways at the end of tidal expiration.

Question 15

What is expiratory reserve volume?

Answer 15

Volume of gas which can be maximally expired form position of FRC.

Question 16

What is residual volume?

Answer 16

Volume of gas remaining in the lungs and airways at the position of full expiration.

Question 17

What is total lung capacity?

Answer 17

Volume of gas in lungs and airways at position of full (maximal) inspiration.

Question 18

How can vital capacity be measured?

Answer 18

-Expired VC (max vol of gas expired from lungs during relaxed expiration from full inspiration).
-Inspired VC (max vol of gas inspired into lungs during relaxed inspiration from position of full expiration.

Question 19

What measurements are made during spirometry?

Answer 19

-forced expiratory volume in 1 second (FEV1)
-forced vital capacity (FVC)
-FEV1/FVC%
-peak expiratory flow (PEF)
-relaxed vital capacity (RVC)

Question 20

What is relaxed vital capacity (RVC)?

Answer 20

Measures the change in volume of air in lungs from TLC to RV in steady exhalation (ERVC) or RV to TLC (IRVC). Measured in Litres.

Question 21

What is the forced expiratory manoeuvre?

Answer 21

Patient breathes out as hard and fast as possible and continues until completely empty.

Question 22

Which two methods display forced expiratory manoeuvre?

Answer 22

-Spirogram
-Flow volume curve

Question 23

What is forced expiratory volume in 1 second (FEV1)?

Answer 23

Volume of gas expired during the first second of expiration. Measured in Litres.

Question 24

What is a spirogram?

Answer 24

Plots exhaled volume against time during forced expiratory. Starts from maximum inspiration (curve is steep as more air expired at the start and then levels off when they have breathed out completely).

Question 25

How do you calculate the FEV1/FVC %?

Answer 25

Measurement of how much of the vital capacity can be breathed out in the first second (healthy is more than 70%). Measured FEV1/ Measured FVC x100

Question 26

What is a flow volume loop?

Answer 26

This is information from the same test but displayed in a different way. This graph has a sharp rise at the start, sharp point at peak flow, steady decline from peak flow to RV. You can't measure FEV1 on flow volume loop!

Question 27

What is peak expiratory flow (PEF)?

Answer 27

Maximum flow that can be achieved during a forced expiration from TLC. Measured in L/min or L/second.

Question 28

What is forced expiratory flow (FEF)?

Answer 28

Max flow achievable during max forced expiration manoeuvre when X% of FVC inhaled (eg FEF25% is max flow rate achievable when 25% of FVC has been exhaled).

Question 29

When is PEF achieved?

Answer 29

Within the first 100 milliseconds of a forced expiration- represents index of resistance to flow through larger airways and bronchioles, effort dependent, measured during spirometry or separate test.

Question 30

How does a peak flow meter work?

Answer 30

Take a deep breath in, put mouthpiece to mouth and blow sharply into the mouthpiece (calibrated to read peak flow rate).

Question 31

Why is standardising lung volume measurement important?

Answer 31

According to Charles' Law, as volume increases, temp increases therefore measuring lung volumes in different situations (hot or cold) means volume can change. Eg when breathe out, gas will cool (volume will be smaller)

Question 32

What is BTPS standardisation?

Answer 32

All lung function volume and flows are corrected to body temp and barometric pressure, saturated with water vapour.

Question 33

What are the 2 different types of spirometer (measuring volume and flow)?

Answer 33

-Volume displacement spirometers -Flow sensing spirometers.

Question 34

What are the 3 types of volume displacement spirometers?

Answer 34

-Water spirometer -Dry rolling seal spirometer -Wedge bellows spirometer

Question 35

What are the 3 common types of flow sensing spirometers?

Answer 35

-Pressure- differential flow sensor (detects flow as pressure drop across a screen, flow then integrated to give volume). -Ultrasonic- Detects flow as changes in speed of ultrasonic signal from source detector -Rotary vane- Measures flow as speed of rotation of vane.

Question 36

What are the advantages of volume displacement spirometers?

Answer 36

-simple to use -robust -reliable, accurate, reproducible -hard core display -stable measurements

Question 37

What are the disadvantages of volume displacement spirometers?

Answer 37

-not portable -difficult to clean (infection risk) -prone to leaks from tubes or bellows -require regular servicing -flow signal may be noisy

Question 38

What are the advantages of flow sensing spirometers?

Answer 38

-excellent portability -ultrasonic and rotary vane are easy to clean (maintain infection control) -relatively cheap -reliable

Question 39

What are the disadvantages of flow sensing spirometers?

Answer 39

-rotary vane fragile -pneumotach readings can drift if temp changes -pneumotach readings sensitive to condensation -calibration is factory set (can't change yourself).