Spirometry 1

Question 1

What is Spirometry?

Answer 1

A physiological test measuring how an individual inhales or exhales volumes of air as a function of time.

Question 2

Types of Spirometer:

Answer 2

1) Volume measuring devices
2) Flow measuring devices

• -> integration of the flow signal gives VOLUME
• -> differentiation of the volume signal gives FLOW

Question 3

Flow (4)

Answer 3

Pneumotachygraph
Rotatory Vane
HWMFS
Ultrasonic

Question 4

Volume (2) types of Volume Measuring Devices

Answer 4

Dry Wedge Bellows

Dry Rolling Seals

Question 5

Obstructive:
Restrictive:

Answer 5

Narrow Airways

Size of Airways

Question 6

Why do we use Spiro? (ctd)

Answer 6

• Detect presence or absence of lung disease
• Assess severity of disease
• Assess progression of lung disorders (e.g. COPD, respi muscle disease, CF)
• Assess responses to treatments/ changes in medications (e.g. bronchodilators)
• Pre-Operative assessment (major surgery)
• Determine Prognosis

Question 7

Prognosis?

Answer 7

The likely course of a medical condition.

• Based on medical experience
• Poor Lung Function often means a poorer prognosis

Question 8

Making the Measurement?

Answer 8

1) Patient preparation/Contraindiciations
2) Equipment Preparation
3) Measurement of Relaxed VC or Spiro

Question 9

Equipment?

Answer 9

• Spirometer
• Barometer/Thermometer
• Height/Weight measures
• Calibration Syringe
• Consumables (bacterial/viral filter)
• Suitable Chair (arms)

Question 10

Equipment Preparation?

Answer 10

• Calibration/Quality Assurance
• Ambient Temperature and Barometric Pressure Recorded - Why?
• -> Manually OR Automatic
• Correct patients details/ demographics carefully entered into recording equipment
• All spirometry tests performed with patient seated.

Question 11

Relaxed Vital Capacity (RVC)

Answer 11

Remember the Graph

Question 12

RVC continued

Answer 12

• Recorded before forced manoeuvres
• Nose clips should be worn (or manual occlusion of nose)
• Patient asked to take a maximal breath in and then blow out
• 3 technically acceptable measurements reported
• 2 largest values < 150ml

Question 13

When should we end the test?

Answer 13

• Duration of Expiration exceeds 15s
• Maximal Patient Encouragement
• Clinical reasons (e.g. Dizziness, Syncope and Discomfort)

Question 14

Reproduce-ability: ARTP/BTS

Answer 14

ARTP/BTS

• Chosen Values for FEV1 and FVC should not exceed the next highest by >5% or 0.1L, whichever is the greater

Minimum of 3 Technically Acceptable attempts

Question 15

Reproduce-ability: ATS/ERS

Answer 15

• 2 largest values of FEV1 and FVC should be < 0.15 litre
• If FVC < 1.0 L, values are 0.1 Litres
• Minimum of 3 technically acceptable manoeuvres
• Recommend no more than 8 measurements

Question 16

MEF flow rates 25-75%

Answer 16

• Mean Forced Expiratory Flow
• Aka Maximal Mid Expiratory Flow
• Taken from the spirometry manoeuvres with the largest sum of FEV1 and FVC

Question 17

Common Errors in Spirometry Measurements:

Answer 17

• Leak at the Mouthpiece
• Obstructed mouthpiece (tongue)
• Poorly co-ordinated start
• Cough
• Early termination of the blow
• Patient did not inspire initially to TLC
• Expiratory effort was submaximal

Question 18

SUMMARY:

Answer 18

• Several indications
• Spirometers are available that primarily measure flow or volume
• Spirometry measurements should be technical acceptable and reproducible
• different guidelines : ATRP/BTS AND ATS/ERS
• Identify and Correct common errors in spirometry
• Writing of appropriate technical comments
• HCP’s should be aware of factors leading to unsafe clinical practice