Spirometry Flashcards
Intro to Spirometry, types of spirometer
What are spirometry tests used for?
To detect abnormalities of measurements of flow and volumes during inspiration and expiration (respiratory disorders can alter mechanical properties of resp system).
What is a spirometry test?
A basic test to start the journey of discovering resp disorders.
-spirare- to breathe
-metrai- measuring
What does spirometry measure?
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.
What are the indications for spirometry?
-medical diagnosis
-surgery
-disability evaluation
-research
What does medial diagnosis include as an indication?
Measure effects of disease on resp function, follow course of a disease, evaluate signs and symptoms, physical fitness, reassure patient.
What does surgery include as an indication?
Preoperative risk evaluation for anaesthetic and surgery, postoperative assessment of surgery (thoracic).
What does disability evaluation include as an indication?
Industrial medical assessment (asbestos), gov compensation laws, personal injury lawsuit and other legal purposes (failure to provide a breath test).
What does research include as an indication?
Clinical trials (lung function over time/ age), epidemiological studies.
What is volume measured in?
Litres.
What is flow measured in?
Volume/ Time (litres per second or litres per minute).
What is tidal volume?
The volume of gas expired or inspired during one breath cycle (normal breathing).
What is inspiratory capacity?
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).
What is inspiratory reserve volume?
Maximum volume of gas that can be inspired from the position of end inspiratory tidal volume (top of tidal volume).
What is functional residual capacity?
Volume of gas in lungs and airways at the end of tidal expiration.
What is expiratory reserve volume?
Volume of gas which can be maximally expired form position of FRC.
What is residual volume?
Volume of gas remaining in the lungs and airways at the position of full expiration.
What is total lung capacity?
Volume of gas in lungs and airways at position of full (maximal) inspiration.
How can vital capacity be measured?
-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.
What measurements are made during spirometry?
-forced expiratory volume in 1 second (FEV1)
-forced vital capacity (FVC)
-FEV1/FVC%
-peak expiratory flow (PEF)
-relaxed vital capacity (RVC)
What is relaxed vital capacity (RVC)?
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.
What is the forced expiratory manoeuvre?
Patient breathes out as hard and fast as possible and continues until completely empty.
Which two methods display forced expiratory manoeuvre?
-Spirogram
-Flow volume curve
What is forced expiratory volume in 1 second (FEV1)?
Volume of gas expired during the first second of expiration. Measured in Litres.
What is a spirogram?
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).
How do you calculate the FEV1/FVC %?
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
What is a flow volume loop?
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!
What is peak expiratory flow (PEF)?
Maximum flow that can be achieved during a forced expiration from TLC. Measured in L/min or L/second.
What is forced expiratory flow (FEF)?
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).
When is PEF achieved?
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.
How does a peak flow meter work?
Take a deep breath in, put mouthpiece to mouth and blow sharply into the mouthpiece (calibrated to read peak flow rate).
Why is standardising lung volume measurement important?
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)
What is BTPS standardisation?
All lung function volume and flows are corrected to body temp and barometric pressure, saturated with water vapour.
What are the 2 different types of spirometer (measuring volume and flow)?
-Volume displacement spirometers
-Flow sensing spirometers.
What are the 3 types of volume displacement spirometers?
-Water spirometer
-Dry rolling seal spirometer
-Wedge bellows spirometer
What are the 3 common types of flow sensing spirometers?
-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.
What are the advantages of volume displacement spirometers?
-simple to use
-robust
-reliable, accurate, reproducible
-hard core display
-stable measurements
What are the disadvantages of volume displacement spirometers?
-not portable
-difficult to clean (infection risk)
-prone to leaks from tubes or bellows
-require regular servicing
-flow signal may be noisy
What are the advantages of flow sensing spirometers?
-excellent portability
-ultrasonic and rotary vane are easy to clean (maintain infection control)
-relatively cheap
-reliable
What are the disadvantages of flow sensing spirometers?
-rotary vane fragile
-pneumotach readings can drift if temp changes
-pneumotach readings sensitive to condensation
-calibration is factory set (can’t change yourself).
