Spirometry Flashcards
What does spirometers recorded
• The spirometer records the volume of air that is breathed in and out
• & generates tracings of air flow (i.e. pneumotachographs)
• Tracings used to calculate:
– vital capacity, tidal volume
– the flow rate of air movement
What are reasons ƒor pulmonary function tests
• Diagnosis -Tests are rarely diagnostic on their own
– Results taken together with history and examination
• Patient assessment - Most usual reason for tests - increased communication between patient and physician
– Serial changes
– Response to therapy
– Assessment for compensation
– Pre-surgical assessment
• Research purposes
– Epidemiology
– Study of growth and development
– Investigation of disease processes
Describe modern spirometers
Modern Spirometers • Use electronic method of measuring the volume of gas inhaled / exhaled through a mouthpiece. • Vitalograph - a make of spirometer which records the volume expired during a vital capacity breath. • FVCstanding > FVCseated – BUT high intrathoracic pressure can result in reduced cardiac output and cerebral blood flow • Observe the subject
Descrive the conventional movements of the trace
• The classic presentation of the traces from these recordings is therefore: • INSPIRATION as an upward deflection • EXPIRATION as a downward deflection
What are Vt, irv, Rev, Rev, vc, flc, FCR
See slide
What is inspiratory capacity
Inspirational capacity =
– VT + IRV
What is frc
• Functional Residual Capacity =
– ERV + RV
What do forced flow volume measurements show us
• How much air can the subject blow out?
– can be reduced in restrictive disorders eg fibrosis
– or if there is airway narrowing precipitating early airway closure (e.g. asthma or CF)
• How fast is the air expelled? – can be reduced with airway narrowing.
• Pattern of change in flow-volume curve (insp & exp) can indicate site of obstruction
• Response to treatment (e.g. β2agonist)
• Change with age or growth
• Progression of disease
What is fvc
Maximal amount of air that the patient can forcibly exhale after taking a maximal inhalation
What is FEV1
Volume exhaled in the first second of FVC
FEV1 is the most reproducible flow parameter and is especially useful in diagnosing and monitoring patients with obstructive pulmonary disorders (eg, asthma, COPD).
What is PEF
Peak expiratory flow (PEF): Maximal speed of airflow as the patient exhales
What is the nomogram cfor fvc comparedto
– The measured value is compared to that of
healthy people of the same
• gender, • age and • height
Describe th time volume graph
• Convention shows expiration as a downward defection on a spirometry
trace:
• This is a graph volume (L) expired against time
• Follows normal graph conventions C and FEV
Graph gives amount breathed out against time
Describe volume-time graphs in obstructive disease
• FVC is not markedly reduced
• (if given sufficient time to completely breathe out)
• Narrowed airways reduces the speed at which air can be breathed out.
• Fraction of air expelled during 1st second (FEV1 /FVC) is markedly reduced.
• Typical pattern in obstructive airways
disease:
– FVC nearly normal – FEV1 markedly reduced – The FEV1 /FVC ratio < 70%
Obstruction means time taken is longer - come can pass through, but it takes longer. FEV1 is imparted in comparison to normal
Descrive volume time graphs in restrictive disease
• FVC is markedly reduced (lungs stiff, cannot be expanded adequately)
• However, the speed at which air can be breathed out is normal (because no
narrowing of airways)
• the fraction of air expelled during 1st
second is normal or even greater than
normal
• The typical pattern in restrictive airways disease:
– A Low FVC
– Low FEV1
– But FEV1 /FVC ratio ≥ 70%
Therefore notobstruction
FVC is lower bc ugs are less stretchy/not as compliant. Therefore, in restrictive conditions, FVc is reduced. May have reduced FEV1 but not too changed.
