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How to determine if a methacholine challange was positive?
A 20% or greater fall in FEV1
The dose or concentration that corresponded with the 20% fall in FEV1
PC20FEV1 value and severity classification
- 0.03-0.124---- Severe
- 0.125-1.99---- Moderate
- 2.00-7.99---- Mild
- Above 8---- Normal
What is the advantage of useing a dosimeter to deliver the methacholine as opposed to a SVN?
- Delivers a more precise does
- Uses less medication
- Trigger flow
- Have breath counters
- Delay periods
What is the basic procedure of exercise induced bronchospasm test?
- Start treadmill at low speed
- Increase the workload during the first 2 to 4 minutes
- Achieve a maximum heart rate 80% to 90% of the patients maximum heart rate by the 4th minute of exercise
- After the patient reaches the target heart rate, an additional 4 to 6 minutes of exercise should be maintained, keeping the heart rate at the target level.
- End exercise
Short acting bronchodilators (albuterol, terbutaline) should be withheld...
For at least 8 hours prior to methacholine challenge
Medium acting bronchodilators (ipratropium bromide) should be withheld...
24 hours prior to methacholine challange
Long acting bronchodilators (salmeterol, formoterol) should be withheld...
48 hours prior to methacholine challange
Contraindications of methacholine challange!
- Severe airflow obstruction (FEV1 less than 50% predicted or 1.0 liter)
- Recent myocardial infarction or stroke within 3 months
- Known aortic aneurysm
- Inability to perform the procedures
- Uncontrolled hypertension
- Upper respiratory tract infection within 2 weeks
Indications for 6-minute walk test!
- Assess functional status (single measurement)
- Measure response to medical interventions
- Predict mortality and morbidity
Exercise induced bronchospasm test can be used to...
- Detect airway hyperresponsiveness
- Confirm suspicion of EIB
- Evaluate pharmacotherapy
Indication for cardiopulmonary exercise test!
- Evaluation of exercise tolerance or limitation
- Evaluation of undiagnosed exercise intolerance
- Evaluation of patients with cardiovascular disease
- Pulmonary rehabilitation prescription and monitoring, O2 prescription
- Evaluation of patients prior to surgery
What are the two main exercise protocols?
- Incremential test
- Steady state
Progressive multi-stage (incremental test) protocol
- Used to determine VO2 max, max HR and ventilation; or symptom limitation to exercise
- Results are compared to expected patterns
- Workload increases at predetermined intervals
- The right combination results in an 8-10 minute test after warm-up
- Conditions of constant metabolic demands
- Defined in terms of HR, VO2, ventilation
- Used to evaluate effectiveness of therapy, meds, rehab on exercise ability
- Sometimes done at 50-75% of maximal workload obtained from prior incremental protocol test
6 minute walk!
- Submaximal test that measures distance walked in 6 minutes (6MWD)
- Test is usually conducted in hallway with flat hard surface
- Patients choose their own intensity and are allowed to stop and rest
- Useful test in providing info on patient’s abilities to perform activities of daily living
- Use only standardized phrases of encouragement during walk
Metabolic equivalent of task (MET)
- Energy cost of physical activities
- Energy is expressed by oxygen consumption in liters or in milliliters per minute or in metabolic equivalence
What is the normal MET value at rest?
3.5 mL O2/min/kg of body weight
Calculation for maximum heart rate!
220 - age
How to calculate the ventilatory ceiling?
Maximum amount of VE that can reached during exercise; determined from MVV or FEV1
Patient safety during cardiopulmonary excersise test!
- Thorough pre-test evaluation to ID contraindications
- Baseline lab tests
- –CBC with electrolytes
- –12-lead ECG
- –CXRResting Vital signs
- Indications for terminating test
- Monitor post test until HR, BP, ECG return to pretest levels; frequent tracings documentedEmergency equipment, medications, crash cart
Patient safety during exercise induced bronchospasms!
- Explain test and obtain signed consent form
- Pre test ECG, BP, and pulse oximetry
- Physician present during exercise and recovery periods
- Well-trained technologists capable of
- •Recognizing respiratory distress
- •Recognizing significant arrhythmias
- •Certified in basic CPR
Patient safety during 6 minute walk!
- Conduct test in location easily accessible in case of emergency
- Emergency care should be available
- Presence of physician not required, but well-trained individual should conduct test
- If patient on O2, conduct test at prescribed O2 level
6 minute walk should be stopped if...
- Patient experiences:
- Chest pain
- Intolerable dyspnea
- Leg cramps
- Walking instability
- Other signs of severe distress
Respiratory exchange ratio (R or RER)
- Ratio of CO2 production to O2 consumption
- Rises slowly with exercise up to AT, after which it rises more quickly
Why does alveolar ventilation increases suddenly towards the anaerobic threshold?
Onset of metabolic acidosis caused mostly by the increased rise of arterial blood lactate during exercise
- The onset of O2 debt in the exercising muscle
- Occurs when the energy demands of the exercising muscles exceed the body’s ability to produce energy by aerobic metabolism
- The workload at the AT is an index of fitness in healthy adults
- Indicator of cardiac performance in heart disease
- Greater than 40% of predicted VO2 max
What additional parameter can you calculate because you have blood gas values?
- Gas exchange
- A-a gradient
What is the difference in oxygen consumption obtained on a cycle ergometer vs a treadmill?
The cycle ergometer produces a slightly lower VO2 max
- Linear relationship between heart rate and VO2
- Normal greater than 80%
What is the normal response to the VD/VT with increasing workload?
Calibration prior to a stress test!
- Should be calibrated before testing every patient
- Validation of the flow measuring device using 3 liter syringe, a range of flows shou,d be used to asses linearity
- Gas analyzers should have a two point verification with precision gas mixtures
How to increase the workload on a cycle ergometer?
- By adjusting the break cycle to increase the resistance
- resistance & RPMs
- Work is increased in 5 to 25 watt increments every minute untill the patient reaches exhaustion
How to increase the workload on a treadmill?
Speed & % grade (incline)
What are the different modes of exercise that can be used during an exercise induced bronchospasm?
- Free running--- most likely to trigger a bronchospasm
- Cycle ergometer
After performing a methacholine challenge what must be done before the patient can leave?
FEV1 should be ≥ 90% of the prechallenge value before patient leaves the laboratory.
Indications for a methacholine challange!
- To diagnose hyperresponsive airways when other methods, such as spirometry before and after bronchodilator, have not been helpful
- Evaluate the effects of occupational and environmental exposures
- Assess the severity of asthma
- Assess the response to therapy
- Use of serial methacholine challenges can be useful in monitoring patients as well as in research trials
When explaining a methcoholine challenge to a patient prior to testing them...
you need to be careful not to give to much information, you need to use suggestive terms… Could influence their response, you don’t want to provoke anxiety
What do the experts believe causes an exercise induced bronchospasm?
- The effect of heat and moisture loss from the respiratory tract
- Mechanical stimulation of breathing at a high minute ventilation
- Lower CO2 tension, which narrows the airways
- Release of lactic acid by exercising muscles
What is a normal ventilatory response to an increase in workload?
- Increase in F and VT untill the higher workloads, Then only the F increases
- The VT increases up to approximately 60% of the patient’s VC and levels off, while f increases up to 50 to 60 breaths/min
- Used in both the 6 minute walk and stress test
- Essential for connecting subjective symptoms to physiologic responses
- Used for assessing breathlessness and leg fatigue
During a symptom limited incremental exercise test, VE in a normal individual...
- Increases in a linear fashion up to approximately 50% of maximun VO2
- Increases up to ventilatory ceiling
The main cardiovascular response to exercise is...
Increase in cardiac output
Which of the following are most correct about minute ventilation during exercise?
- Increases linearly with work up to the anaerobic threshold
- Increases linearly with O2 consumption up to the anaerobic threshold
A normal amount of physiologic dead space at rest in healthy individuals is usually less than...
35% of tidal volume
During exercise, the O2 consumption increases with work...
In a linear fasion
What is the response of PaO2 during exercise in healthy individuals?
Remains relatively even up at high work rates
During the CPET, exercise should be stopped if there is...
- Severe chest pain (angina)
- Systolic blood pressure over 250 mmHg
- Fall in diastolic blood pressure of more than 20 mmHg
The anaerobic threshold can be identified by which of the following?
Change of rate of VCO2 relative to VO2
Exercise induced bronchospasm!
- Studies have shown a relationship between the severity of EIB and the type, intensity, and duration of exercise.
- During an exercise period of 6 to 8 minutes (a standardized time for this test), both asthmatic and normal patients have a rise in peak expiratory flow rate (PEFR) and FEV1
- –Increased catecholamine release most likely causes this bronchodilatation
- Near the end of or just after the exercise period, an asthmatic patient with EIB has a marked fall in PEFR and FEV1, with the values reaching their lowest level 3 to 15 minutes after exercise
The advantages of fitness when we train aerobic?
- Increased SV at rest & exercise
- Decreased systolic BP & ventilation
- Lower resting HR
- Reach higher VO2 max
- Able to maintain higher level of work for longer periods
What drugs might blunt the hearts response to exercise?
Normal O2 pulse at rest!
2.5 - 4.0
Normal O2 pulse with stress!
10 - 15
What are some conditions that might cause the patient not to respond with their heart correctly to exercise?
- Ventilation gas exchange problem
- Poor effort
In normal adults the anarobic threshold occurs...
At 60 - 70% of VO2 max