Section 1: Asthma and COPD 1 Flashcards
Therapy for COPD exacerbation
Bronchodilators (inhaled) = nebulized albuterol
Ipratropium (inhaled)
Steroids = prednisone or methylprednisone
Antibiotics = ceftriaxone
Counseling
Influenza vaccine
Pneumococcal vaccine
List the most important features of a severe asthma exacerbation
Hyperventilation/ increased respiratory rate
Decrease in peak flow
Hypoxia
Respiratory acidosis
Possible absence of wheezing
Enumerate the minimum management for patients with SOB
Oxygen
Continuous oximeter
CXR
ABG
What is the best test to determine a diagnosis of reactive airway disease in an asymptomatic patient suspected of being asthmatic?
Methacholine stimulation testing
What class of drug is methacholine?
Synthetic acetylcholine
What happens when methacholine is administered to asthmatic?
Methacholine will decrease FEV1 if the patient has asthma.
Name the two most frequently used pulmonary function tests
FEV1 (forced expiratory volume in one second)
FVC
What is the normal adult FEV1/FVC ratio?
> 75%
Describe the obstructive pattern in PFT
An FEV 1/FVC ratio of 70%
Total lung capacity (TLC) will be increased in some obstructive processes, such as COPD, whereas it may be normal or increased in asthma.
Name some obstructive lung disease
COPD
Asthma
Chronic bronchitis
Bronchiectasis
What is the meaning of DLCO
Diffusing capacity of carbon monoxide
What does DLCO measure?
Measures the gas exchange capacity of the capilary-alveolar interface
Why is DLCO normal in asthma
Because the alveoli are not affected
What is the DLCO in COPD
The DLCO in COPD is decreased because some alveoli are destroyed and unavailable for gas exchange.
Describe the restrictive pattern in PFT
Low FEV1, low FVC, but with normal or increased FEV1/FVC
Decreased TLC
An FVC of 80% is suggestive of restriction when the FEV1/FVC ratio is normal.
Examples of diseases with restrictive pattern on PFT
Obesity
Interstitial lung disease
Inflammatory/fibrosing lung disease
Kyphosis
Define hypoxia (or hypoxemia)
Defined as a room-air O2 saturation of 88%
or a PaO2 of 55 mm Hg on ABG measurement
or evidence of cor pulmonale.
Diagnosis: Hypoxia not responding to supplemental oxygen
Shunt physiology
Examples of diseases with ventilation-perfusion (V/Q) mismatch
Asthma
COPD
Nonmassive pulmonary embolus (PE)
Pneumonia.
Features of ventilation-perfusion (V/Q) mismatch
Responds to oxygen
Increased arterial-alveolar oxygen (A-a) gradient
What is the common cause of hypoventilation?
Oversedation from medications
Features of hypoventilation
Responds to O2
Characterized by a normal A-a gradient
Features of hypoxia due to decreased diffusion
Responds to O2
Characterized by an A-a gradient
Associated with a very low DLCO.
Le, Tao; Bhushan, Vikas; Herman Bagga (2010-09-21). First Aid for the USMLE Step 3, Third Edition (First Aid USMLE) (Kindle Locations 11153-11157). McGraw-Hill. Kindle Edition.
Features of hypoxia due to high altitude
Responds to O2
Characterized by a normal A-a gradient
Causes of SOB due to shunt physiology
Acute respiratory distress syndrome
Significant lobar pneumonia
Patent foramen ovale
Patent ductus arteriosus.
Features of SOB due to shunt physiology
Typically does not respond to O2
Characterized by an increased A-a gradient
Differential diagnosis of Asthma presenting as chronic cough
Allergic rhinitis
Postnasal drip
GERD
Differential diagnosis of wheezing
Asthma
Foreign body aspiration
Laryngeal spasm or irritation
GERD
CHF
In asthma management, can inhaled corticosteroids be used in pregnancy
Yes, they are safe
What is the implication of a normal PaCO2 in during an episode of asthma exacerbation
A normal Pco2 suggests that the patient is tiring out and is about to crash
Outline the management of acute asthma
Initiate short-acting β-agonist (albuterol) therapy (nebulizer or MDI)
Administer a systemic corticosteroid such as methylprednisolone or prednisone
Begin inhaled corticosteroids as well
Follow patients closely with peak flows, and tailor therapy to the response
Chronic antibiotics (without evidence of infection), anticholinergics, cromolyn, and leukotriene antagonists are generally not useful in this setting
Rx for exercise induced asthma
Inhaled bronchodilator prior to exercise
What is the management of acute shortness of breath in a patient with COPD?
Oxygen and arterial blood gas (ABG)
Chest x-ray
Albuterol, inhaled
Ipratropium, inhaled
Bolus of steroids (e.g., methyl prednisolone)
Chest, heart, extremity, and neurological examination
If fever, sputum, and/ or a new infiltrate is present on chest x-ray, add ceftriaxone and azithromycin for community-acquired pneumonia.
When to intubate patients with COPD?
Do not intubate patients with COPD for CO2 retention alone. These patients often have chronic CO2 retention. Only intubate if there is a worsening drop in pH indicative of a worse respiratory acidosis. Serum bicarbonate is often elevated due to metabolic alkalosis as compensation for chronic respiratory acidosis.
List the typical physical findings in COPD
Barrel-shaped chest
Clubbing of fingers Increased anterior-posterior diameter of the chest Loud P2 heart sound (sign of pulmonary hypertension)
Edema as a sign of decreased right ventricular output (the blood is backing up due to the pulmonary hypertension)
Laboratory findings in COPD
EKG: Right axis deviation, right ventricular hypertrophy, right atrial hypertrophy
Chest x-ray: Flattening of the diaphragm (due to hyperinflation of the lungs), elongated heart, and substernal air trapping
CBC: Increased hematocrit is a sign of chronic hypoxia. Reactive erythrocytosis from chronic hypoxia is often microcytic. An erythropoietin level is not necessary.
Chemistry: Increased serum bicarbonate is metabolic compensation for respiratory acidosis.
ABG: Should be done even in office-based cases to assess CO2 retention and the need for chronic home oxygen based on pO2 (you expect the pCO2 to rise and the pO2 to fall).
Pulmonary function testing (PFT): You should expect to find the following:
– Decrease in FEV1
– Decrease in FVC from loss of elastic recoil of the lung
– Decrease in the FEV1/ FVC ratio
– Increase in total lung capacity from air trapping
– Increase in residual volume
– Decrease in diffusion capacity lung carbon monoxide (DLCO) caused by destruction of lung interstitium
Chronic medical therapy for COPD
Tiotropium or ipratropium inhaler
Albuterol inhaler
Pneumococcal vaccine: Heptavalent vaccine,
Pneumovax Influenza vaccine: Yearly
Smoking cessation
Long-term home oxygen if the pO2 < 55 or the oxygen saturation is < 88 percent
Name two interventions that lower mortality in COPD
Smoking cessation
Home oxygen therapy (continuous)
Spot Diagnosis: A case of COPD at an early age (< 40) in a nonsmoker who has bullae at the bases of the lungs.
Alpha-1 antitrypsin deficiency
Rx for alpha-1 antotrypsin deficiency
Alpha-1 antitrypsin infusion
What is the most accurate diagnostic test for bronchiectasis?
High-resolution CT scan of the chest.
Diagnosis: Decreased TLC, Decreased RV, Decreased VC, Normal FEV1, Normal FEV1/FVC ratio, Normal DLCO
Extra-parenchymal (extra-thoracic) restriction
- Kyphosis
- Obesity
Diagnosis: Increased TLC, Increased RV, Decreased FEV1, Decreased FVC, Decreased FEV1/FVC ratio, Decreased DLCO
COPD
Diagnosis: Normal or Increased TLC, Normal or Increased RV, Decreased FEV1, Decreased FVC, Normal or Decreased FEV1/FVC ratio, Normal or Increased DLCO
Asthma
Diagnosis: Decreased TLC, Decreased RV, Decreased FEV1, Decreased FVC, Normal or Increased FEV1/FVC ratio, Decreased DLCO
Fibrotic (or Interstitial Lung) Disease
List the minimum that should be done for all patients with shortness of breath (SOB)
Oxygen
Continuous oximeter
Chest X-ray
Arterial blood gas (ABG)
Causes of low DLCO
Emphesema
Pneumonectomy
Interstitial lung disease
pulmonary embolism
Pulmonary HTN
Arterial blood gases measurements
pH: 7.35 to 7.45
PCO2: 33-45mmHg
PO2: 75-105mmHg
What is A-a gradient?
A-a gradient is alveolar-arterial gradient (PAO2-PaO2 gradient). It is a useful calculation for the assessment of oxygenation. A-a gradient increases with age and is only valid in room air. It is calculated as follows:
PA02-Pa02 gradient = 150 - 1.25 X PaCO2 - PaO2
i.e.,
A-a gradient = [150 - (1.25 X PaCO2) - PaO2]
This gradient is between 5 and 15 mmHg in normal young adults. It increases with all causes of hypoxemia except hypoventilation and high altitude