Pulmonary

• Tidal volume (TV)


  In/out air with each quiet breath
• Expiratory reserve volume (ERV)


  Extra air pushed out with force beyond TV, RV remains in lungs

  
• Inspiratory reserve volume (IRV)


  Extra air can be drawn in with force beyond TV, lungs filled to capacity

  
• Residual volume (RV)


  Air that can't be blown out no matter how hard you try

  
• Total lung capacity


  Sum of all volumes: RV + ERV+ IRV + TV

  
• Inspiratory capacity


  Most air you can inspire: TV + IRV
• Forced vital capacity (FVC)


  Most you can exhale: TV + IRV + ERV
• Functional residual capacity


  RV plus ERV
• Pulmonary function tests must meet criteria for adequate test: sharp peak in flow curve, expiratory duration more than six seconds

  
• Inadequate test should be repeated
• Obstructive lung diseases (asthma, COPD)


  • Reduced FEV1 (slow flow out)
  • Reduced FVC (less air out)
  • Reduced FEV1/FVC (hallmark)

  
• Asthma


  Reversible obstruction, ↑ FEV1 with bronchodilators
• COPD


  Partial/no change in FEV1 with bronchodilators
• Obstructive lung diseases (asthma, COPD)


  • Increased volumes from air trapping: total lung capacity, functional residual capacity, residual volume

  
• Flow volume loops can distinguish obstructive, restrictive, and fixed airway obstruction
• Restrictive lung diseases


  • Reduced FEV1 (less air in/out)
  • Reduced FVC (less air in/out)
  • Normal (> 80%) FEV1/FVC (hallmark)

  
• Restrictive lung diseases


  • Reduced volumes: total lung capacity, functional residual capacity, residual volume

  
• DLCO


  Measures ability of lungs to transfer gas, normal = 75–140% predicted, severe disease < 40% predicted

  
• Conditions with low DLCO


  • Interstitial lung disease
  • Emphysema
  • Abnormal vasculature
  • Pulmonary hypertension
  • Pulmonary embolism
  • Prior lung resection
  • Anemia

  
• Asthma


  Reversible bronchoconstriction, usually triggered by allergic stimulus, type I hypersensitivity reaction
• Asthma


  • Common in children, associated with other allergic (atopic) conditions: rhinitis, eczema, may have family history of allergic reactions
• Asthma symptoms


  Episodic: dyspnea, wheezing, cough, hypoxemia, increased expiratory phase, decreased I/E ratio, reduced peak flow, mucous plugging (airway obstruction/shunt), death: status asthmaticus
• Asthma triggers


  • Respiratory infection
  • Allergens (animal dander, dust mites, mold, pollens)
  • Stress
  • Exercise
  • Cold
  • Aspirin
• Asthma diagnosis


  Usually classic history/physical exam, improvement with albuterol, reduced FEV1, reduced FEV1/FVC ratio, FEV1 improvement 12% after albuterol
• Methacholine challenge


  Muscarinic agonist (similar to acetylcholine) causes bronchoconstriction, administer increasing amounts and look for 20% fall in FEV1
• CBC may show increased eosinophils, serum IgE levels may be increased in asthma
• Pulsus paradoxus


  Fall in systolic blood pressure > 10 mmHg with inspiration, most frequent non-cardiac causes are asthma/COPD

  
• Asthma medications


  • Short-acting beta-agonist (SABA): albuterol
  • Long-acting beta-agonist (LABA): salmeterol, formoterol
  • Inhaled corticosteroids (ICS)
  • Oral corticosteroids
  • Intravenous corticosteroids
• Leukotriene receptor antagonists


  Montelukast (Singulair), useful in aspirin sensitive asthma
• Zileuton


  1. lipoxygenase inhibitor, blocks conversion of arachidonic acid to leukotrienes
• Omalizumab


  IgG monoclonal antibody, inhibits IgE binding to IgE receptor on mast cells & basophils
• Cromolyn


  Inhibits mast cell degranulation, blocks release of histamine, leukotrienes
• Asthma treatment


  • Avoidance of triggers
  • Bronchodilators
  • Corticosteroids
  • Leukotriene receptor antagonists
  • Zileuton
  • Omalizumab
  • Cromolyn
  • Theophylline
• Asthma acute exacerbations


  Shortness of breath, wheezing, cough, chest tightness, decrease in peak flow from baseline
• Asthma acute exacerbation treatment


  • Oxygen
  • Nebulized albuterol
  • IV or oral corticosteroids
  • Rarely used: ipratropium, IV magnesium sulfate
• Empiric antibiotics not recommended for asthma exacerbations, contrast with COPD exacerbations
• Increased WBC with left shift is a normal response to asthma therapy, does not indicate infection
• Asthma severity classification


  • Intermittent
  • Mild persistent
  • Moderate persistent
  • Severe persistent
• Intermittent asthma is treated with SABA as needed
• Persistent asthma treatment steps


  • Step 2: Add low dose ICS
  • Step 3: Medium ICS or low ICS + LABA
  • Step 4: Medium ICS + LABA
  • Step 5: High ICS + LABA
  • Step 6: High ICS + LABA + Oral Steroids