Introduction to spirometry
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What is a spirometry test?
-measures ventilatory function by measuring the volume of air which can be breathed out and how quickly you can breathe it out.
What are some general indications for spirometry?
-medical diagnosis -surgery -disability evaluation -research
What are some medical diagnosis indications for spirometry?
-measures effect of disease on respiratory function -evaluate signs, symptoms or lab findings -physical fitness, selection or evaluation in health and disease -reassure patient and physician -follow the course of disease affecting respiratory function
What are some surgical indications for spirometry?
-pre- op risk evaluation for anaesthetic and surgery -post-op assesment of surgery, in particular thoracic surgery
What are some indications for spirometry based on disability evaluation?
-industrial medical assessment -government compensation laws -personal injury lawsuit -other legal purposes( failure to provide a breath test)
What are some indications for spirometry in regards to research?
-clinical trials -epidemiological studies
What are the units of volume and flow?
volume - litres flow- litres/second or litres/minute
Whats the equation that links flow, volume and time?
flow= volume/time
What are the lung subdivisions?
volumes- VT, ERV, IRV, RV capacities-IC, VC, TLC units-litres
Define tidal volume
the volume of gas expired or inspired during one breathing cycle
Define inspiratory capacity (IC)
the maximum volume of gas which can be inspired from the position of functional residual capacity (FRC)
Define inspiratory reserve volume (IRV)
the maximum volume of gas which can be inspired from the position of end inspiratory tidal volume
Define functional residual capacity (FRC)
the volume of gas in the lungs and airways at the end of a tidal expiration
Define expiratory volume (ERV)
the volume of gas which can be maximally expired from the postion of FRC
Define residual volume (RV)
The volume of gas remaining in the lungs and airways at the position of full expiration
Define total lung capacity (TLC)
the volume of gas in the lungs and airways at the position of maximal inspiration
What measurements are made during spirometry?
-FEV1 (forced expiratory volume in 1 second -FVC (forced viral capacity) -FEV1/FVC% -Peak expiratory flow (PEF) -relaxed vitall capacity (RVC)
what is relaxed vital capacity?
measures the change in the volume of air in the lungs from expiratory relaxed vital capacity or inspiratory relaxed vital capacity exp-from TLC to residual volume insp-from residual volume to TLC measured in litres
Describe the forced expiratory manoeuvre
-patient breathes out as hard and as fast as possible and continues until they are completly empty -spirogram -flow volume curve
Define FEV1
volume of gas expired during the first second of expiration is also measured -measured in litres
Whats a spirogram?
plots exhaled volume against time during a forced expiratory effort -graph starts at a position of maximum inspiration
How to calculate FEV1/FVC% ratio?
-calculate FEV1 as a percentage of the FVC • how much of the vital capacity can you breathe out in the first second -in healthy subjects the FEV1/FVC% will be over 70%
FEV1/FVC% ratio equation?
FEV1/FVC% = measured FEV1/ Measured FVC% all x100
What is the flow volume loop?
information from the same test but displayed in a different way -measures expiration and inspiration