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Kettering-PFT's (copy)


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What are spirometers
-Positive displacement-flow
-Measures volumes and flow
What do pneumotachs measure
-Not accurate at high or low flows
What are the types of pneumotachs?
-Fleisch(pressure differential) Can be used to continuously measure minute ventilation
Body Box
-Based on Boyle's Law
- Temp remains constant
- Measures airway resistance and compliance
-FRC or TGC (thoracic gas volume)
How is volume calibration, leak tests and flow calibration done
-Volume calibration and leak tests are done by using a large volume syrings (super syringe at 3 L)
- Flow is done with rotometer
What measures restrictive lung diseases?
-Vital Capacity (SVC, VC)
- Vital capacity is the best measurement (IRV+VT+ERV)
What measures obstructive lung disease?
-FVC The volume that can be expired forcefully. Provides flow rates
-FEV1 (should be able to blow out 75%
What measurement is the best indicator of obstructive lung disease
-If FEV1 is decreased but FEV1/FVC is normal, restrictive only
FEF 200-1200
-Large airway obstruction
-Typical value: 8L/sec (480L/min
FEF 25-75
-Small airway obstruction
-Typical value 6L/sec
-Effort dependent
- Typical value 10L/sec
This is not a flow, it is a volume. SHould be equal to SVC. If FVC smaller than SVC, air trapping. If cannot be completed in 3 seconds, obstructive
-The patient is told to breathe inand out as fast as possible until told to stop (12-15 seconds)
-Measures muscular mechanics
-Decreased=obstructive, increase RAW, muscle weakness, dec. conpliance, poor patient effort
Pre and Post bronchodilator PFT testing
-measures reversibility of obstruction
-Increase of 15% is significan
- Stop bronchodilator therapy 8 hours prior to testing
He dilution
-closed meethod
-determines FRC
N2 washout
-Open method, FRC is washed out
-Calculates FRC
What do flow volume loops evaluate
-restrictive=skinny and tall
-Obstructive=short and wide
-Best evaluates a patient with partial vocal cord paralysis (large airway obstruction)
In gas distribution, what does phase oneand two indicate
Phase one=deadspace
Phase two is combination of deadspace and alveolar gases
In gas distribution, what does phase three and four indicate
-Phase 3=evenness of gas distribution (flat mid portion)
- Phase 4=a sudden rise in N2% and is called closing volume
What is a normal DLCO and when does it decrease?
Normal=25 mL CO/min/mmHg STPD
- Decrease occurse in PEASE, pulm fibrosis, sarcoidosis, ARDS, edema, emphysema
What is a bronchial provocation test?
It is performed by administering a provocotave agent (meth, histamine, fold air, irritant, exercise) to a patient to see if there is airway hyperactivity.
When is the bronchial provocation test positive
When there is a 20% decrease in FEV1
What is the dosage of methacholine required for a positive test called?
-Provocative dose or PD20%
- Can be given via a nebulizer or dosimeter
How long should patients not take the following drugs prior to bronchial provocation test? Beta 2 drugs, methyl, comolyn sodium, antihistamines
-Beta 2 drugs 8 hours
-methylxanthines - 12 hours
-cromolyn sodium - 24 hours
- antihistamines - 48 hours
In bronchial provocation testing, what can asthma be described as
-a paradoxical finding of decreased compliance, couples with decreased maximum lung elastic recoil
What are predicted values based on for PFT's?
How do you interpret PFT's
80-100% of predicted=normal
60-79 = mild disorder
40-59 = moderate disorder
<40% = severe disorder
What test should be used with PFT tests
-The best test should be determined and used for recording
- best test=highest FVC/FEV1

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