Spirometry Flashcards
DLCO
diffusing capacity of the lung, capacity of lung to transfer CO2
ERV
expiratory reserve volume, max volume of air that can be exhaled from end-expiratory tidal position
FET
forced expiratory time - amt of time pt exhales during FVC
FEV1
forced expiratory volume in 1 second
FRC
functional residual capacity, volume of air in the lungs following tidal volume exhalation
FVC
forced vital capacity, total volume can be forcefully expired from max inspiratory effort (all the way full to all the way empty except residual air in lungs)
IC
inspiratory capacity, max volume of air can be inhaled from tidal volume end-experiatory level
IRV
inspiratory reserve volume
LLN
lower limit of normal
PEF
peak expiratory flow, fastest rate of flow
RV
residual volume, air remaining in lungs after max exhalation
TLC
total lung capacity, total volume in lungs at full inhalation
TV (or VT)
tidal volume
VC
vital capacity - max air that can be exhaled starting from max inspiration
spirometer def
device that measures the volume of air inspired or expired and records the time over which volume change occurs
What are four main reasons to use spirometry
- diagnostic
- public health (epidemiology studies, reference calcs, etc.)
- monitoring
- disability/impairment evaluations
Diagnostic reasons to use spirometry
- eval sx
- eval abnormal lab reports
- measure effect of disease on pulm fn
- assess pre-op risk
- screen people at risk for pulm dx
- assess prognosis
- assess health status prior to start of strenuous activity
monitoring reasons to use spirometry
- assess therapeutic intervention
- describe course of disease that affects lung fn
- monitor people exposed to injurious agents
- monitor for adverse reactions to drugs with well known pulm toxicity
role of spirometry in primary care
- provide objective measure of airflow restriction/obstruction
- assess reversibility of airflow obstruction
- provide objective measurements for asthma assessment and monitoring
- assist with initial dx of asthma and assessment of asthma control
what age can start using spirometry to dx asthma
=>5 usually
how is asthma reversibility determined using spirometry
After administering short acting bronchodilator:
- increase in FEV1 > 12% from baseline
- increase that is at least 200mL
*2-3 week steroid tx might be required to demonstrate reversibility
Methods to establish dx of asthma
- med history with detailed sx (cough, wheezing, SOB with exercise)
- PE assess respiratory tract, chest, skin
- Spirometry to demonstrate obstruction and assess reversibility
- additional studies as needed to exclude other dx
NAEPP recommends spirometry in five situations (5)
- initial assessment
- after tx to determine “normal” airway fn
- during periods of loss of control
- when assessing change in pharmacotherapy
- every 1-2 years to assess maintenance of airway function (Kaitlin… hahaha)
Spirometry results that demonstrate obstruction
- FEV1 <80% predicted
2. FEV1/FVC below LLN of individual’s predicted value
what is the gold standard of objective asthma (other breathing disorders?) measurements
spirometry
What does spirometry require from the pt
- effort
- coordination
- cooperation
careful coaching/instruction from medical professional
what is required for consistently accurate test results
- correct technique
- calibration of machines
- maintenance of equipment
what is essential for accurate assessment
reproducibility of efforts
Spirometry maneuvers
- nose clip preferred
- normal breathing prior to test
- max forced exhalation during test
- repeated until acceptability and reproducibility are achieved
coaching for best technique
- fill lungs completely
- seal lips - no leaks!
- blast out as hard and fast as possible
- blow until lungs are completely empty
Criteria for acceptability
- lack of artifact (cough, glottic closure, equipment problems)
- start without hesitation
- satisfactory exhalation with 6 sec smooth continuous exhalation or reasonable duration with a plateau
- 3 acceptable spirograms, 2 largest FVC within 200 mL
Look at slides for pictures of acceptable and unacceptable efforts
:)
Once three acceptable spirograms are obtained, what tests must be done?
- 2 largest FVC must be within 0.150 L of each other
- 2 largest FEV1 must be within 0.15 L of each other
OR
- 8 tests have been performed
- pt can’t continue
* then save best 3
PEFR
peak expiratory flow rate - max air flow rate during forced exhalation
How assess spirometry results
based on
- FVC
- FEV1
- FEV1/FVC
relative to reference or predicted values
what do the predicted values depend on
age
gender
height
race
how are predicted values used
as percentage of average expected, called “percent predicted”
how are FEV1 and FCV expressed on spirogram
- absolute number
- percent predicted
> 80% predicted are normal
what happens to FEV1/FVC as we age
declines
what 4 reduce FVC
- lung disease (resection, collapse, obstructive dz)
- probs with pleural cavity (enlarged heart, pleural fluid, tumor)
- chest wall restriction
- respiratory muscle issues don’t allow inflation and deflation of lungs
What is the most reproducible measure in spirometry
FEV1
- most commonly obtained
- most powerful measurement
what is interesting about children FEV1/FVC ratio
high flow for size so ratios often higher, up to 90%
What is the significance of FEV1/FVC ratio
- IDs people with airway obstruction in people with reduced FVC
- IDs the cause of low FEV1 (restrictive or obstructive)
FEV1/FVC in restrictive disease
decrease proportionately, ratio is normal. May even be increased bc of elastic recoil of lungs
FEV1/FVC in obstructive disease
reduced ratio vs. predicted value
Obstructive defect def
process that causes a decrease in max expiratory flow so that can’t rapidly empty lungs
- emphysema, chronic bronchitis, asthma
- generally see associated decrease in FVC
restrictive defect
lung volume is reduced by any process except obstruction
- total lung capacity must be less than normal!
what does a reduced FVC with a normal FEV1/FVC suggest
restrictive pattern
what does a reduce ratio of FEV1/FVC indicate
obstruction
Pattern appearance on flow loop
- normal
- obstructive
- restrictive
- normal: rapid peak, gradual decline to zero
- obstructive: rapid peak, scooped decline
- restrictive: normal shape just smaller, witch hat
What to do when get abnormal test result
- confirm demographic data (m vs. f makes a big difference)
- was test acceptable and reproducible
- look at appearance of flow/volume curve
- look at FEV1/FVC ratio
FEV1/FVC ratio
- low value
- normal value
- low: obstructive
- normal: restrictive or normal
Obstructive and Restrictive pattern
- FVC
- Obstructive: decreased or normal
- Restrictive: decreased
Obstructive and Restrictive pattern
- FEV1
- Obstructive: decreased
- Restrictive: decreased or normal
Obstructive and Restrictive pattern
- FEV1/FVC
- Obstructive: decreased
- Restrictive: normal
Obstructive and Restrictive pattern
- total lung capacity
- Obstructive: normal or increased
- Restrictive: decreased
FEV1 abnormality severity
- mild >70%
- moderate 60-69%
- moderately severe: 50-59%
- severe: 35-49%
- very severe: <35
Discussing spirometry results with pts
- acknowledge info, combined with hx and PE, will help establish dx
- spirometry alone does not make the dx
- add’l tests might be necessary for further assessment
- spirometry might improve with effective asthma management