PFT Quiz number 3 Flashcards
Why do we need specialized tests?
-Patient has symptoms but a normal PFT but has respiratory symptoms.
-Hyperresponsiveness in the airways.
-Uncertain results of bronchodilator testing.
Bronchoprovocation Challenge
(Bronchial Challenge)
-Used to identify and characterize hyperresponsiveness in the airways.
- The less amount of time it takes to evoke a negative response, the more hyperreactive the airway.
Direct Stimulus vs. Indirect Stimulus
Direct stimulus-Acts directly on the parasympathetic smooth muscle.
Indirect stimulus-Release of endogenous mediators (chemical agent).
Agents used in the Methacholine challenge
Direct Stimulus Indirect Stimulus
-Methacholine -Mannitol
-Histamine -Adenosine
-Prostaglandins
Methacholine and Histamine
Increases parasympathetic response in bronchial smooth muscle.
Eucapnic Voluntary Hyperventilation
Uses cold air or room temp gases to cause heat and water loss from the airways.
Methacholine challenge
-Methacholine is inhaled in increasing doses 0.016 to 16 mg/mL
-Stimulates a parasympathetic response in bronchial smooth muscle
-Used for patients who cannot tolerate repeated spirometry testing.
-When the FEV1 is reduced by 20%, it is considered a positive test. AKA PC20 or Provocative Concentration.
-The test is considered negative if the dose of methacholine reaches 16 mg/mL without a 20% reduction in the FEV1.
Will ALL patients experience a change in airway with increasing concentrations?
Yes. The lower the dose needed to stimulate a response, the more hyperresponsive the patient is.
Testing Criteria
The patient must be asymptomatic.
Withholding Medications
Antihistamines (72-96 hours)
Performing the test
-Baseline spirometry is performed to ensure FEV1 is greater than 60%.
-Highest doses for either test is 16 mg/mL
-FEV1 is measured after each increase in concentration.
Dosimeter
-Dosing starts at 0.625 and is increased x4 for each step up until you reach the max dose of 16 mg/ml.
-Can be prepared in advance and stored in fridge, must be room temp at the time of use.
-Delivers a consistent volume of drug with a fixed volume of aerosol on each breath.
-Pt takes 5 breaths of 1st concentration.
-Spirometry is repeated 30 to 90 seconds after each dose.
-Test is repeated until FEV1 decreases 20% or until the maximum concentration of Methacholine is reached.
-At any time, the FEV1 decreases by 20%, the test is complete.
-After the test, a bronchodilator is given to reverse bronchospasms.
2-minute tidal breathing
-A filter is used on expiratory limb.
-Output needs to be 0.13 ml/min
-Dosage starts at 0.031 and increases x2 for each step up to the max of 16.0.
-Can be prepared ahead of time but room temp when used.
-A filter is used on expiratory limb.
-Bronchodilator is used to reverse bronchospasm.
Reporting the results
-If a decrease in FEV1 occurs after the first dose, report: PC20 less than first dose. (Less than the lowest concentration given).
-If there is no decrease after the last dose, report PC20 is greater than 16 mg/mL (greater than the maximum dose 16 mg/mL)
PC20 related to Asthma
A decrease in FEV1 of 20% at low doses of methacholine indicates a high probability of asthma.
A decrease of less than 20% of FEV1 at highest does of asthma indicate that asthma is highly unlikely.
Steroids
Never withhold steroids.
Histamine challenge
-Stimulates bronchoconstriction directly.
-As long as the patient does not have a decrease in FEV1 of greater than or equal to 20% with the diluent, the test continues.
-Patient breathes in 5 breaths at first concentration.
-Dosing starts at 0.03 mg/ml and doubled until max dose of 10.00 mg/ml is reached.
Common effects of histamine
Bronchospasm can be blocked by histamine.
Exercise challenge
-Bronchospasm usually occurs during or immediately after exercise.
-Usually related to heat and water loss in the airways.
-Do not repeat testing for at least 4 hours.
Pre-test prep
-History and physical
-EKG
-No bronchodilators prior to the test.
-FEV1 should be no less than 65% of predicted.
-No vigorous exercise for 4 hours prior to the test.
-No Resp, infections 3 to 6 weeks prior to the test.
Excercise Testing
-Workload should be at 80% to 90 % of max HR for 4 to 6 mins.
-During the test, EKG HR, BP and saturations are monitored.
Positive Exercise Challenge Test
-A decrease of 10% to 15% in the FEV1 is consistent with airway hyperreactivity.
-In a healthy patient, the FEV1 will increase, not decrease.
Eucapnic Voluntary Hyperventilation Testing
-Provokes bronchospasms
-CO2 is added to prevent hyperventilation and maintain the pH.
-Creating a CO2 narcosis
Cold Air Method
-CO2 is added to prevent hyperventilation and maintain the pH.
Results
In a healthy patient, eucapnic voluntary hyperventilation will cause bronchodilation not a bronchospasm.
-A greater than or equal to 10% decrease in FEV1 indicates a hyper reactive airway.
ENo test (Exhaled NO)
-Measures inflammation in the lungs.
Before the test
-No smoking for 1 hour.
-No eating for 1 hour.
-No drinking for 1 hour.
-Must have at least 2 acceptable tests within 20% of each other, then average them.
What do Exhaled NO numbers mean?
If the levels are elevated above the norms, suspect eosinophilic inflammation alveolitis.
Why use NO?
Changes in NO happen quicker than PFT’s.
ABG’s
Considered most basic test of lung function.
-pH
-PCO2 is inversely related to pH.
-Oxygen tension (PO2)- influence by the altitude and temperature.
Henderson-Hasselbach equation
-PaCO2 (by separating the hydrogen and bicarbonate)
-Diffused through a Polarographic electrode AKA: Clark electrode
Body Temperature
-As the body temperature increases the CO2 increases and inversely the pH decreases.
-The body’s response to an increased CO2 level is to take deeper breaths or more breaths to compensate.
-When this happens, the Pao2 increases as well.
-Venous samples are not useful in assessing oxygenation.
Effects of air in the sample
When there is air mixed in the sample, it causes the CO2 to go down, therefore the PH will go up and the PO2 reads high.
Dead Space
If dead space is increased, the body’s natural response is to increase ventilation to compensate.
Pulse Ox
Functions by transmitting a light absorbed by oxyhemoglobin.
Oxygenated hemoglobin absorbs more light and allows more light to pass.
Stead wells water seal
Has a wet version and a dry version
Bellows Spirometer
-AKA wedge spirometer
-Accordion type
-Collapsible bellow that folds and unfolds when breathing.
Turbine flow sensor (Best known as Wright respirometer)
AKA Wright’s respirometer
Heated wire flow sensor
Based on the cooling effect of gas flow
PITOT Flow sensor
Usually has 2 sets of tubes so that bidirectional flow can be measured.
-Used in exercise testing.
Ultrasonic flow sensor
Uses frequency sound waves across a stream of gas.
Portable spirometry
-Portable spirometers use disposable flow sensors.
-Recommendations for spirometers are set forth by the National Lung Health Education program
Peak flow
Max inhalation followed by a forced expiration.
-Low range 400 L/Min
High range peak flow can measure flows up to 850 L/min
-Must be acceptable and replicable with a less than 5% variability.
Body Plethysmography
Pressure and volume vary inversely (Boyles Law)
With Body Plethysmography there are 2 types:(pressure and flow) and they both use what?
-They both use Flow sensors
(pneumotachometers)
-Most accurate when measuring volumes.
Demand Valves
Require pressure to trigger gas flow and responds to patient effort.
Gas analyzers
-Response time -How fast the analyzer can detect and display a change in the concentration of gas.
-Transportation Time-How long it takes to move gas from a sample site to an analyzer.
O2 Analyzer
-Polarographic 02 or Clark electrode
-Good for monitoring during exercise testing but not metabolic studies.
-Quick response time (200 msec)
-Breath by breath analysis.
Zirconium Fuel Cell
Can be used for exercise and metabolic studies.
-Fast response but it has to be heated.
Galvanic
Most popular
Gas Chromatograph
-Very accurate
-Can analyze multiple gases (As many gases as it has tubes)
Thermal Conductivity Analyzer
Can not be used to detect rapid changes
Chemoluminescent Analyzer
Routinely used to assess airway inflammation FENO
CO2 and H2O absorbers
Prevents interference from water vapor or CO2
pH electrodes
AKA: Sanz Electrode
PCO2 Electrode sensor
AKA: Severing Haus Electrode
PO2 Electrode
AKA: Clark Electrode
-Needs a POLARIZING VOLTAGE SO THEREFORE IT IS A POLARGRAPHIC ELECTRODE
Portable Blood gas analyzers
-Provides rapid bedside results.
-Accuracy is comparable to large machines.
Pulse oximeter
-Must have a good Pleth wave
-Anemia may cause the pulse ox to read higher than it truly is (estimates oxygenation at the tissue, it’s not a measurement of PAO2)
CPET
-Highly sensitive noninvasive stress test
-CPET assess how well the heart and lungs and muscles are working individually and in unison.
-The traditional treadmill test only relies on changes in EKG.
Progressive multi-stage
Uses increasing workloads 3–4-minute intervals.
Steady State
-If the HR remains unchanged for 1 minute, a steady state is assumed.
-Uses the Bruce protocol to estimate or calculate the VO2 max.
Bruce Protocol
-A max. exercise test where the subject works to complete exhaustion as the treadmill speed and incline is increased every 3 minutes.
-The length of time on the treadmill is the test score and can be used to estimate the VO2 max value.
-During the test, the HR, blood pressure and ratings of perceived exertion are measured.
VO2 Max
For healthy people, the VO2 max will plateau at maximum intensity for exercise (Watch for changes on the graph)
6 minute Walk test
-Patient limited- can stop and rest if needed.
-However, if the patient stops, the time does not stop.
Treadmill
-Workload is adjusted by changing the speed and or slope of the walking surface.
-Work performed is a factor of the patient’s weight.
-Patient should relax with hands resting on side rails slightly above their body for support only.
Cycle Ergometer
Workload is increased by adjusting the resistance to pedaling and frequency.
Maximum Heart Rate
To estimate your maximum heart rate, subtract your age from 220.
What is monitored during testing?
BP
HR
EKG and Pulse Ox
Contraindications
PaO2 below 40 on room air
PaCO2 above 70
Early termination of testing
Progressive chest pain (Angina)
2 mm ST segment depression
T wave inversion or Q waves present
V Tach
Lightheadedness, mental confusion
Monitoring system failure
Cyanosis
Isocapnic buffering
During exercise, lactic acid accumulates after anerobic threshold (VAT) sets in. Lactic acid begins to increase and the body releases bicarb to compensate. The higher intensity of the workload, the more lactic acid that is produced.
At some point the body finds it difficult to compensate by the release of bicarb and hyperventilation occurs. This is called the RCP (Respiratory compensation point)
Isocapnic buffering is the phase between VAT and RCP.
Oxygen pulse
Volume of O2 consumed with each heartbeat.
A low pulse with increasing work (low stroke volume) indication of CAD or valvular insufficiency.
ABG’s and Excercising
If the PaO2 decreases to 40 or saturations decrease to 85% or less- Terminate the test.
Borg Scale (Patient’s Perceived perception of exertion)
Perceived perception of how hard your patient feels their body is working.
For example: If a person’s rating of perceived exertion is (RPE) is 12 then 12 x 10 is 120 so the approximate heart rate should be 120 bpm.
Interpretation strategies
To interpret a study appropriately, the practitioner must assess the degree of effort and determine if this was a maximal effort.
Only one criterion must be met to determine maximal effort.
What disease processes may benefit from Pulmonary rehab?
CBABE
Lung resection
Neuromuscular disease
Education and training
-Community resources and ancillary Support groups
-Better Breathers Club (COPD)
-Harmonica club (COPD)
-Quest for breath (provides up to date info on idiopathic Cystic Fibrosis)
Based on individualized assessment.
Contraindications of Pulmonary Rehab
Ischemic Heart disease
Acute cor pulmonale
Pulmonary hypertension (can have exceptions)
Metastatic Cancer
Renal failure
Significant hepatic dysfunction
Severe cognitive deficit
Assessment and need for the program
Pulmonary function studies
