Introduction to spirometry Flashcards
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
Describe what the flow volume loop graph looks like
-almost right angle triangle
-sharp rise at start
-sharp point at peak flow
-steady decline in flow from peak flow to RV
Define PEF/ peak expiratory flow test?
the maximum flow that can be achieved during a forced expiration from TLC
-reported in L/min or L/sec
What can you not measure on a flow volume loop?
-FEV1
What is FEF/ forced expiratory flow?
the maximum flow achievable during a maximum forced expiratory manoeuvre when x% of the FVC has been exhaled
Example FEF25% is the maximum flow rate achievable when 25% of the FVC has been exhaled
Describe what happens during a PEF test
-PEF is achieved within the first 100 milliseconds of a forced expiration
-represents an index of resistance to flow through larger airways and bronchioles
-effort dependent
How are lung volume measurements standardized?
-charles law states that a given quantity of gas held at a constant pressure will have a volume directly proportional to the absolute temperature
-as temperature increases, volume increases to
Whats the link between temperature and spirometry?
-patient breathes out = expired gas cools
-temp of exhaled gas falls from body temp to temp within spirometer
-Charles law states the volume of gas becomes smaller
-as air cools, water vapour within condenses
-to standardize results all lung function volumes and flows are corrected to body temp and barometric pressure, saturated with water vapour conditions (BTPS)
