Pathophysiology Flashcards
Types of pulmonary disease that limit exercise tolerance
- obstructive diseases (high airway resistance/obstruction)
- restrictive diseases (fibrosis-loss of alveoli, non-compliant lung)
- chest wall defects (muscle weakness/chest wall deformity)
what is CODP characterized by?
by progressive development of airflow limitation, not fully reversible, caused by chronic inflammation of the airways and lung parenchyma
COPD and mortality
- 4th leading cause of death
- only cause of death in USA that continues to climb
what causes COPD
long-term exposure to noxious gases and particles
three major mechanisms of COPD
- Loss of elasticity and alveolar attachments to airways (emphysema)
- Narrowing of small airways lumen (inflammation and scarring)
- Excessive secretion of mucus that blocks the airways
More of what COPD is characterized by
- High airway resistance (low FEV1%) –> Hyperinflation at end-expiration.
- Patients have a high functional residual capacity which encroaches on inspiratory capacity
- Because of hyperinflation inspiratory muscles work more than normal, and are mechanically inefficient.
- Skeletal muscle deconditioning and/or myopathy
emphysema and barrel chest
• Loss of elasticity (increased compliance of the lung) in emphysema leads to hyperinflation of the lungs.
• Hyperinflation leads to increased chest wall diameter (called “barrel-
chest”)
obstructive disease has lower
FEV and FEV1%
what is the limiting symptom at rest and exercise of COPD
- Dyspnea = perceived difficulty or distress in breathing
* Shortness of breath
what does poor V/Q matching lead to?
increased need for VE (higher VE ) at given work rate to eliminate CO2 and maintain PaO
why is work of breathing increased with COPD
- Due to airflow obstruction (high resistance)
* Due to inefficient breathing mechanics (hyperinflation)
COPD and energy cost of breathing
- low VO2max
- increased energy of breathing, lactic acidosis at low work rates –> When severe energy cost during exercise can reach 40%!
- This energy cost “steals” blood away from exercising muscles –> Some COPD pts limited by leg fatigue, not dyspnea, during exercise
what can therapeutic interventions that decrease work of breathing do?
increase exercise tolerance
strategies for decreasing dyspnea
- bronchodilation
- exercise therapy
- oxygen therapy
bronchodilation for decreasing dyspnea
- Decreases Hyperinflation & Dyspnea
* Increases breathing efficiency
what does oxygen therapy decrease?
- VE
- Breathing Frequency
- Dyspnea
- Hyperinflation
- Improve Metabolic Status
what is much of the disability in COPD related to?
concurrent deconditioning
maybe some evidence for disease related muscle disfunction
evidence for muscle dysfunction in COPD
- low muscle mass and strength, muscle aerobic enzymes and capillarity, and OBLA
- slow rise in VO2 at exercise onset –> increased O2 deficit and reliance on anaerobic metabolism
- exercise training improves muscle tolerance and muscle function
Potential abnormalities in muscle structure and function in patients with COPD
CS
HADH
Mechanisms Underlying Muscle Dysfunction In COPD
• Deconditioning
• Malnutrition
• Skeletal muscle myopathy
— Associated with chronic corticosteroid use
— Associated with chronic hypoxia, hypercapnia, and/or inflammatory cytokines
• Low circulating androgens
Purposes Of Exercise Training In Persons With Pulmonary Disease
Exercise training has NOT been shown to affect the progression or reversal of the actual disease pathology /mechanisms
Benefits Of Regular Exercise Training
- Improve functional capacity for daily activities (work tolerance) via
improvements in muscle fitness, flexibility, cardiorespiratory endurance - Reduced VE during submaxexercise
- Shift OBLA to higher intensity by increasing skeletal muscle aerobic
capacity - Improved coordination and economy of movement, respiratory muscle endurance, and improved work tolerance by reducing dyspnea severity during submax exercise
Selected Evidence Based Clinical Practice Guidelines for Pulmonary Rehabilitation
- Exercise training of muscles of ambulation recommended as a mandatory component of pulmonary rehabilitation for patients with COPD
- Lower-extremity exercise training at higher exercise intensity has greater physiologic benefits than lower intensity training in patient with COPD
- Both low-and high-intensity exercise has clinical benefits for patients with COPD
- Addition of a strength training to pulmonary rehab increases muscle strength and mass
- Supplemental oxygen should be used during rehab exercise training in patients with severe exercise induced hypoxemia
A major difference between testing in a patient with cardiac disease and pulmonary disease
increased emphasis on measuring pulmonary function before, during and after the testing
General Considerations For Exercise Testing For Persons With Pulmonary Disease
- Pulmonary gas exchange measurements –> static and dynamic lung function tests and respiratory muscle tests
- ALWAYS includes a measurement of arterial oxygenation: pulse oximetry (SaO2), arterial blood gases (PaO2, PaCO2)
Considerations For Exercise Prescription for pulmonary disease
•In patients with functional limited by ventilatory variables, prescription of intensity can’t be made based on % age predicted HRmax or HRR –> Monitor S/S dyspnea and breathlessness to adjust individualized exercise prescription
No one optimal strategy
FITT Recommendations in COPD - Resistance Training
- F: 2-3 days per wk, non-consecutive days
- Strength: 60-70% of 1RM for beginners; ≥80% 1 RM for experienced lifters; 2-4 sets, 8-12 reps
- For endurance, <50% 1RM, 1-2 sets, 15-20 reps
FITT Recommendations in COPD - Aerobic Training
- F: 2-3 days per wk, non-consecutive days
- Strength: 60-70% of 1RM for beginners; ≥80% 1 RM for experienced lifters; 2-4 sets, 8-12 reps
- For endurance, <50% 1RM, 1-2 sets, 15-20 reps
Modified BORG Dyspnea Scale
0: nothing
0.5: very, very slight
1: very slight
2: slight
3: moderate
4: somewhat severe
5, 6: severe
7, 8: very severe
9: very, very severe
10: maximal
During exercise, oxygen supplementation is indicated if:
- PaO2 < 55mmHg
- SaO2 < 88%
- Titrate O2 flow to maintain SaO2 at >=90%
Asthma is characterized by:
an increased responsiveness of the airways to various stimuli and manifested by a diffuse (functional) narrowing of the airways, that changes in severity either spontaneously or as a result of treatment
Underlying pathology of asthma is believed to involve:
chronic inflammatory processes
What is Exercise-induced Bronchospasm
15% or greater postexercise reduction of FEV1 or peak expiratory flow rate (PEFR) from pre-exercise values after standard
submaximal exercise stress
what can EIB occur with?
chronic asthma as well as in persons with no evidence of asthma at rest
what falls with EIB
V1%
FEV1/FVC
EIB Symptoms/Signs Can Occur During Or Post Exercise
- Wheezing
- Chest tightness
- Shortness of breath (dyspnea)
- Cough
- Mucus production
- Need to stop exercising
Bronchospasmic Conditions During Exercise
• Cold, dry air
• Pollens, dust, air pollution (in individuals with chronic airway hyperresponsiveness)
• The more intense and longer in duration the exercise
(resulting in a larger VE and loss of fluid) the more bronchospasmicthe exercise
Why is swimming less bronchospasmic than running or cycling (other than the humid conditions)?
- Interrupted nature of breathing pattern (airflow)
- Lower ventilation volume
- Greater catecholamine response b/c of activation of a smaller (upper body) muscle mass to do the same work
Potential Causes Of EIB
- Release of “bronchoconstrictor substance” in response to changes in osmolality of the periciliary fluid, from airway fluid loss during conditioning of inspired air (humidification , filtering and warming), mast cell release of histamines, leukotrienes, prostaglandins
- Result: inflammation, can trigger neurally-mediated constriction, or act directly on smooth muscle
airway irritation during exercise –>
release of chemical modulators –> smooth muscle constriction, increased mucous –> increased airway resistance –> EIB symptoms- Wheezing, coughing, dyspnea
standard test for EIB
• Standard test: 6-8 min of exercise (usually treadmill) at 75-85% hrmax
• Under asthmogenic conditions: cold dry air, use of treadmill running, no premedication or caffeine
• 80-90% of asthmatics develop EIB after this test
• Fall in FEV1% or PEFR:
– Mild: 10-24%
– Moderate: 25-39%
– Severe: >40%
Avoiding EIB - Refractory Period
• About 50% of asthmatics have a refractory period after the first bout of exercise
• Such that a second bout will provoke EIB response that is
~50% of the initial response
– Lasts 1-4 hours
– Value of a warm-up!
Avoiding EIB- Pharmacology
- Aerosol beta-2 agonist: at least 15 min prior to exercise
- also effective in interrupting an EIB in progress (“rescue inhaler”)
- Cromolyn sodium (mast cell stabilizer)-prior to exercise
- Inhaled corticosteroids- usually daily use
Symptom refractory period
sub threshold warmup intense enough to tax system without causing symptoms –> inhaler use immediately following warmup –> 20-30 minute interval for medication delivery to tissues –> symptom free exercise
Exercise And Glucose Transport
• During exercise and continuing for several hours —there is an insulin-independent, contraction-initiated increase in glucose uptake via translocation of pre-formed GLUT4 transporters to the cell surface
most prevalent modifiable risk factor for CV disease
sedentary lifestyle
