PFT Flashcards
Restrictive pattern
- low volume and normal flow
- Reduced FVC
- Normal FEV1/FVC ratio
- obesity, Pulmonary fibrosis, interstitial lung disease, muscular dystrophy, scoliosis, sarcoidosis, pulmonary embolus
small airway obstruction
- Low flow, FVC normal or low
- Asthma exacerbation
- emphysema
- chronic bronchitis
- Bronchodilators, corticosteriods
fixed large airway obstruction
- Reduced flows on insp and exp
- tracheostenosis
- reduced vols and flows
Variable intrathoracic large airway obstruction
- Expiratory curve flattened
- flows and volumes are impacted on exhalation only
- inside thorax
- tracheal CA
- tracheal malacia(soft trachea)
- tumor
- tx: surgical intervention
Variable extrathoracic large airway obstruction
- Inspiratory curve flattened- reduced flow and volume
- outside of thorax
- laryngeal CA
- vocal cord dysfunction - speech therapy
When performing spirometry it is important that values are reported at?
BTPS
GOLD Standard
Stage 0
At-risk- symptoms present, Normal spirometry
Avoid risk factors
Get influenza vaccine
GOLD Standard
Stage 1
- mild
- FEV1/FVC <70%
- FEV1 > or equal 80%
- Add short acting Bronchodilator PRN
GOLD Standard
Stage 2A
- Moderate
- FEV1/FVC <70%
- 50%<= FEV1<=80%
- Add LABA and rehab
GOLD Standard
Stage 2B
- Moderate
- FEV1/FVC <70%
- 30%<=FEV1<=50%
- Add inhaled steroids if repeated exacerbations
GOLD Standard
Stage 3
- FEV1/FVC <70%
- FEV1<=30% or PaO2<60 or right heart failure
- Add long term O2 if chronic resp failure, ? surgical rx
Nitrogen washout
- Measures FRC by measuring volume of N2 in lungs at end exhalation
- open circuit- no rebeathing
- only measures gas with communication airways (Not trapped gas)
Helium dilution
- Closed circuit (rebreathing)
- pt. FRC is mixed with a second separate gas with know volume and %
- 10% He (or other inert gas)
- 21% O2
- 69% N2
- gas is rebreathed until helium diluted to equilibrium
DLCO
- used to assess diffusion of CO across alveolar membrane
- pt exhales to RV, then maximally inhales gas mixure
What effects DLCO results?
- Direct relationship
- surface area of ACM
- capillary blood vol
- lung volume active in gas exchange
- amount of Hb
- Inversely
- thickness of ACM
- carboxyhemoglobin level (smoker)
- alveolar O2 tension (PAO2)
What causes decreased DLCO?
- interstital lung disease (restrictive fibrosis)
- emphysema
- Pulmonary vascular disease (vasculitis, Pulm HTN)
- pneumonia
- sarcoidosis
What could cause increased DLCO?
- increased VA
- polycythemia
- exercise
- normal or high with asthma
FENO
- Fractional exhaled nitric oxide
- evaluates eosinophilic airway inflammation
- increased value: asthma not in control or COPD exacerbation (nonmed compliance)
- Decreased value: CF and smokers
- Normal adult: 15-25 ppb
- Normal child: 5-22 ppb
Bronchoprovocation study
- Determination of airway hyper-reactivity
- Precations
- Resuscitation equipment on hand
- MD immediately available
- Meds to reverse the provocation agent
- A positive test is when a 20 DECREASE in FEV1 is observed
What values show Obstruction in spirometry?
- Low FEV1/FVC defines the presence of obstruction
- FEV1 determines the severity
What values show restriction on spirometry?
- Low FVC with normal or high FEV1/FVC suggests restrictive lung disease
- Measurement of TLC used to confirm restriction and grade severity
The predicted FVC value for African American is?
10-15% less than that for caucasions
what spirometry parameter would you recommend to assist a patient with asthma in monitoring their day to day symptoms?
PEF
What is the proper method to minimize cross contamination between patients performing tests that only require exhalation into the apparatus?
- Change only those elements through which rebreathing occurs
- Place a disposable bacterial filter between the patient and breathing circuit
What do you do every time before you perform spirometry?
Calibrate the device
ATS standards
Free from
- hesitation(slow start)
- cough
- Early termination ( lasts at least 6 seconds)
- a Valsalva maneuver (glottis closure)
- leak
Must be reproducible
- two best FVC are within 50 ml of each other
- two best FEV1 are within 150ml of each other
Vt
Volume inspired with a normal breath
MVV
Maximal voluntary ventilation
The greatest amount of air you can breathe in 12 to 15 seconds
TLC
argest amount of air the lungs can hold
PEFR or PEF
Fastest flow generated at the very beginning of forced exhalation
large airways
Can be used to help an asthmatic monitor their daily symptoms
DLCO
Millimeters of gas the lung can transfer to the blood
VC
Amount of air you can exhale after a maximum inspiration
IRV+ Vt+ ERV
FEV1/FVC
- Ratio of volume exhaled in 1 second to the total volume exhaled
- Ratio >70% = obstruction
- a reduced FVC with normal ratio suggests restriction
IC
Amount of air you can inhale after a normal expiration
IRV+Vt
IRV
Amount of air you can inhale after a normal inspiration
RV
Air left in the lungs after a maximum exhalation
FRC
Air left in the lungs after a normal exhalation
ERV+RV
FVC
Amount of air you can forcefully exhale after a maximum inhalation
Reduced in restrictive lung disease (because they, in general, have reduced volumes)
FEF25-75%
Average expiratory flow during the middle part of forced expiration
FEV1
Volume of air you can forcefully exhale in 1 second
- Reduced in obstructive disease
- Normal in Restrictive
ERV
Amount of air you can exhale after a normal exhalation
in addition to calibration with a 3-L syringe, what method should be used to validate the spirometer performance and accuracy of software computations?
testing with biologic controls
when performing bedside spirometry, you observe an S-shaped plotted FVC-versus-time curve on the display. What most likely caused this?
failure to achieve a rapid start exhalation
What is a positive test in a methacholine challenge/bronchoprovocation study?
a 20% decrease in the FEV1
What is a normal respiratory quotient value?
.8
What is a positive bronchodilator reversal on a PFT?
- 12% increase on FEV1
AND
- 200mL increase on FEV1 or FVC
