Spirometry Flashcards
Inspiratory reserve + Tidal volume=
Expiratory reserve volume + Residual volume=
Inspiratory reserve + Tidal volume= Inspiratory capacity
Expiratory reserve volume + Residual volume= Functional residual capacity
Tidal volume + Inspiratory reserve volume + Expiratory reserve volume =
Tidal volume + Inspiratory reserve volume + Expiratory reserve volume = Vital capacity
Atmospheric pressure =
Plural pressure at rest =
zero
negative
Define Transpulmonary pressure: Ptp
Palv-Ppl
What happens during inspiration in the lungs?
Hint: start with muscles cnx and how that changes volumes and pressures
Diaphragm and intercostals cnx–> thorax EXpands–> Ppl becomes more Subatmospheric (more negative)–> will cause INCREASE of Transpulmonary pressure –> Lungs expand–> Palv becomes subatmospheric–> air into alveoli
We must genenerate a ____ pressure in the alveoli to get air to rush in
Negative pressure (does this after lungs expand)
What determines airflow, particularly during expiration?
Flow =
Palv-Patm /airway resistance
Thus RESISTANCE big determining factor and changes across lengthand diamter of airway
What can you deduce from this graph about the size of bronhci and the resistance?
Key is HIGH resistance in the medium sized bronchi around 5-10 generations; less of a total cross sectional area. As we get to higher generations, resistance much lower
At low lung volumes, airway resistance is ______
HIGH, increasing lung volume increases x-section and decreases resistance.
Resistance and xsection have inverse relationship
The tip of this curve is what:
What is it defined by?
Point of zero airflow
Ptp = Ppl
When looking at this graph, what does the slope represent?
Ptp =
Compliance
Ptp = Palv = Ppl
What do we see in emphysema and fibrosis in a Vital capacity vs pressure graph?
Empysema requires less pressure generated to get to TLC
In fibrosis, you need a larger change in pressure to generate change in volume
Why do lines A, B and C meet at around 4 liters of expired air?
Past a certain point, expiration is effort independent, doesn’t matter how hard you blow out.
What is the pattern of the pressure in the alveoli as it moves towards bronchus?
We see pressure inside alveoli dissipates
starts at +40 while the pressure exerted against it is +30…
as we get closer to bronchus, pressure decreases and is more likely to collapse
Indications for PFTs
Indications for PFTs
• Diagnostic: Symptoms, signs, abnormal lab tests
• Assess the effects of diseases and therapies
• Screening: Smokers, occupational exposures, preoperative risk, disability, prognosis
START WITH SPIROMETRY
You’re on rotations and your attending calls you over and shows you a spirometry and asks you a dx… what’s your repsonse?
tell her you need the pt history as well.. can’t dx with spirometry alone!
What is going on in the Volume Time curve
Just showing us that the peak is air you are expiring. You reach a peak after 1 sec and slowly decreases after that. Most people reach residual volume at 6 seconds
Any structures that are affecting airflow inside the chest or intra-thoracic will affect _____
Structures outiside the chest (extra-thoracic) will affect _____
expiration
inspiration
At ____the inspiratory and expiratory flow rates should be about the same
50% vital capacity
Focusing on the expiratory phase (part on top) how is obstructive disease different then normal?
Restrictive?
Obstructive has a scalloped expiratory flow… result of air trapping. You can’t blow air out as fast.
Restrictive: you cannot bring in as much air, no issue on expiration
Which image shows fixed upper airway obstruction with flow limitation and flattening of both the inspiratory and expiratory limbs of the flow-volume loop.
One on far left
Could patient with COPD have a loop pattern like the one of the far left?
The diagram shows fixed upper airway obstruction as flow is limited in both inspiration and expiration.
This immediately rules out intrathoracic pathology – COPD and pulmonary fibrosis.
panel shows dynamic (or variable, nonfixed) extrathoracic obstruction with flow limitation and flattening of the inspiratory limb of the loop.
Middle loop = Vairable extrathoracic issue
panel that shows dynamic (or variable, nonfixed) intrathoracic obstruction with flow limitation and flattening of the expiratory limb of the loop.
Right panel = variale intrathoracic; determine by large intrathoracic airways
When interpreting Spiromety:
Look only at :
Always look at this first:
- Look only at FEV1/FVC ratio, FEV1, and FVC
- Always look at the FEV1/FVC ratio first
• FEV1/FVC must be close to____% of predicted to be “normal” - anything outside the____% confidence interval is low
100%
95%
Spirometry interpretation:
• A NOT-LOW ratio is seen in______ ventilatory
function and_____ processes
• A LOW ratio indicates_______ processes
normal and restrictive
obstructive
In order for a spirometry test to be within normal limits, what 2 things must be there?
- FEV1/FVC ratio (FEV1/VC%, FEV1/VC ratio) is normal
- AND VC (FVC) is normal
FEV1/FVC ratio (FEV1/VC%, FEV1/VC ratio) is normal in the range of:
(normal range can be .70 to .87, depending on demographics of patient)
VC (FVC) is normal when it’s in the range of:
(usually greater than or equal to 80% of predicted- within the 95% confidence level
What disease process do we see on this spirometry?
Shows airway obstruction:
could be caused by stuff like inflmmation or bronchoconstriction: mucus/fibrous damage could do it too.
What is the significance of using a spirometry test to tell if someoneh as obstructive diseaes?
Because FEV1 is effort dependent so that will IG look simular to normal, but as exhalation continues, it is effort independent and depends on smaller structures, such as bronchioles and alveoli, which ar damaged in obstructive diseases
If the FEV1/FVC Ratio is Low
• Degree of airway obstruction is based upon the percent of predicted FEV1
• % Predicted FEV1 >99% :
• % Predicted FEV1 70 - 99% :
• % Predicted FEV1 60 - 69% :
- % Predicted FEV1 >99% Physiologic Variant
- % Predicted FEV1 70 - 99% Mild
- % Predicted FEV1 60 - 69% Moderate
- % Predicted FEV1 50 - 59% :
- % Predicted FEV1 34 - 49% :
- % Predicted FEV1 < 34%:
- “OBSTRUCTIVE VENTILATORY DEFECT”
- % Predicted FEV1 50 - 59% Moderately Severe
- % Predicted FEV1 34 - 49% Severe
- % Predicted FEV1 < 34% Very Severe
- “OBSTRUCTIVE VENTILATORY DEFECT”
Bronchodilator Responsivity
• Assess for all patients with spirometry showing a :
• Assess for all patients suspected of :
low FEV1/FVC ratio
• asthma or chronic obstructive lung disease
• A significant response to a bronchodilator is
shown when the FVC or FEV1 increases at
least 12% and 200mls
What determines if a bronchodilatory response occured?
• A significant response to a bronchodilator is shown when the FVC or FEV1 increases at
least 12% AND 200mls
Obstructive Ventilatory Pattern
• Large conducting airways:
• Peripheral airways:
• Pulmonary parenchymal disease:
• Large conducting airways: tumors, foreign bodies
• Peripheral airways: asthma, chronic bronchitis, cystic fibrosis
• Pulmonary parenchymal disease: emphysematous changes from cigarette
smoking
Restrictive Ventilatory Defect
• Interstitial lung disease:
• Pleural disease:
• Chest wall disease:
• Extrathoracic conditions:
sarcoidosis, collagen vascular diseases, pulmonary fibrosis
pleural effusion
kyphosis, neuromuscular disorders
obesity
What do changes from normal in restrctive ventilatory defects on spirometry?
See the overall shape is normal but the FVC is low
Normal FEV1/FVC Ratio and a Decreased FVC
• Interpret cautiously from spirometry-should obtain lung volumes
We may want to think right away this is Restrictive disease, but _______ is the true hallmark of a restrictive ventilatory defect
• Reduced TLC
- % Predicted TLC 70% to LLN :
- % Predicted TLC 60 to 69% :
- % Predicted TLC < 60% :
- % Predicted TLC 70% to LLN Mild
- % Predicted TLC 60 to 69% Mod
- % Predicted TLC < 60% Mod Severe
- “RESTRICTIVE VENTILATORY DEFECT”
If cannot obtain lung volumes when determining restrictive disease is present or not, grade FVC via the
obstructive FEV1 criteria
If the FEV1/FVC Ratio is Not Low and TLC is
Low and You are Following the _____ to
Assess Restriction
FVC
If the FEV1/FVC Ratio is Not Low and TLC is Low and You are Following the FVC to Assess Restriction
• Degree of restriction is based upon the percent of predicted FVC
• % Predicted FVC 70 - 79% :
• % Predicted FVC 60 - 69%:
• % Predicted FVC 50 - 59% :
• % Predicted FVC 34 - 49% :
• % Predicted FVC < 34% :
Look at Shape of the Flow Volume Loop
• Beware of a flattened inspiratory curve
• Check the FEF50/FIF50 ratio
• FEF50/FIF50 1.00 or less :
• FEF50/FIF50 > 1.00 :
FEF50/FIF50 A little > 1 :
Normal if 1.0 or less
>1.0 is variable extrathoracic airway obstruciton
a little <1 : Fixed Extrathoracic airway obstruction
Guidelines for acceptibility in Spirograms
- Free from artifacts: Cough, early termination
- Good start: Extrapolated volume is <5% of FVC or 0.15 L, whichever is greater or time to PEF is <120 ms
- Satisfactory exhalation: 6 sec of exhalation and/or a plateau in the volume-time curve
Repeatability guidelines on spirometry
Repeatability
• After three acceptable spirograms: Are the two largest FVCs within 0.2 L of each other? Are the two largest FEV1s within 0.2 L of each other?
• If both of these criteria are not met, test until: Both are met or a total of 8 tests
• Save the 3 best maneuvers
Examples of unacceptable spirograms
extrapolated volume, hesitation while exhaling, cough, exhalation not complete
