Obstructive Lung Disease

Question 1

Asthma general characteristics

Answer 1

• chronic inflammatory disorder
• associated w/airway hyperresponsiveness ==>
• recurrent episodes of wheezing, breathlessness, chest tightness, and coughing
• reversible spontaneously or w/treatment

Question 2

Airway inflammation in Asthma

Answer 2

• persistant inflammation ==> most prominent @ medium-sized bronchi
• inflammatory cells involved =
  
  • mast cells
  • eosinophils
  • T lymphocytes
  • dendritic cells
  • neutrophils

Question 3

Structural airway changes in asthma

Answer 3

• increased smooth muscle cells
• blood vessel proliferation
• mucus hyper-secretion (increased goblet cells + submucosal glands)

Question 4

Control of Airway diameter

Answer 4

• neural regulation
  
  • parasympathetic (cholinergic) motor neurons via vagus ==> aCH stimulates smooth muscle contraction
  • nonadrenergic noncholinergic receptors (excitatory and inhibitory)
• Beta-adrenergic ==> increase intracell cAMP ==> smooth muscle relax
• ion channels: Ca²⁺ and K⁺

Question 5

Physiologic consequences of asthmatic airflow obstruction

Answer 5

• increased resistance to airflow (accentuated during expiration) ==> air trapping ==> hyperinflation
• hyperinflation ==> flattening of diaphragm ==> inefficient msucular respiratory effort

Question 6

Mechanics of diaphragm in obstructive lung disease

Answer 6

• Muscle fibers of the flattened (shortened) diaphragm cannot generate adequate tension ==> operating @ suboptimal point on length-tension curve
• in addition to overcoming increased airway resistance, the asthmatic must use less efficient respiratory muscles to inflate their lungs.
• these pathophysiologic effects increase oxygen consumption and carbon dioxide production by the diaphragm (and other respiratory muscles).

Question 7

PFTs in Asthma

Answer 7

• exacerbation ==> obstructive pattern
  
  • DECREASE in FEV₁/FVC that usually responds to beta-adrenergic agent
    
    • improvement = >12% or >200mL
  • increase in TLC, RV and FRC due to air trapping
• may look normal in between episodes

Question 8

Bronchoprovocation testing in possible asthmatics

Answer 8

• serial spirometry after inhaling progressively high concentrations of methacholine (histamine analog)
• PC₂₀ = concentration required to lower FEV_1​
  
  • several times lower in asthmatics than healthy people
• Can also be performed using exercise as bronchoprovocation

Question 9

Goals of asthma therapy & strategies

Answer 9

• reduce airway tone
  
  • beta-agonists (albuterol)
  • anti-cholinergers
  • leukotriene inhibitors
  • methylxanthines = PDE inhibitor ==> increase intracell cAMP
• reduce inflammation
  
  • corticosteroids
  • mast cell stabilizers
  • leukotriene inhibitors
  • Anti-IgE therapy

Question 10

Acute asthma treatment

Answer 10

• systemic corticosteroids
• inhaled bronchodilators (beta-agonists, anticholinergics)
• possibly: positive pressure ventilation or mechanical vent

Question 11

Asthma severity classification system

Answer 11

Question 12

COPD general characteristics

Answer 12

• irreversible airflow limitation
• FEV₁/FVC < .7
• risk factors:
  
  • smoking
  • inhaled biomass smoke
  • occupational exposures
• subtypes:
  
  • emphysema
  • bronchitis
  • chronic obstructive asthma

Question 13

Characteristics of Chronic Bronchitis

Answer 13

• Clinical: productive cough for 3 months per year over 2 year period w/out other explanation
• airway epithelium ==> squamous metaplasia
• disease of airways (vs. emphysema = disease of parenchyma)
• increased airway resistance due to changes in airway structure ==> impaired ventilation
• normal D_LCO
• minimal reversibility

Question 14

Characteristics of Emphysema

Answer 14

• enlargement of air spaces distal to terminal bronchioles accompanies by destruction of their walls
• airflow obstruction due to airway collapse during expiration
• most common cause = smoking
• may also be cause by alpha1 anti-trypsin deficiency

Question 15

Pathophysiology of chronic bronchitis

Answer 15

• limitation of airflow (particularly expiratory)
• resistance due to excessive mucous secretion + bronchial wall inflammation/thickening

Question 16

Pathophysiology of ephysema

Answer 16

• limitation in airflow rates (expiratory)
• loss of alveolar-capillary surface area + loss of elastic recoil

Question 17

PFTs for COPD

Answer 17

• FEV₁/FVC < /7
• RV, FRC, and TLC are all increased
• Chronic bronchitis = normal D_LCO
• Emphysema = low D_LCO

Question 18

Clinical presentation of COPD

Answer 18

• dyspnea
• cough, wheezing, chronic sputum production
• evidence of hyperinflation
• limited diaphragm movement + use of accessory muscles
• purse-lipped breathing
• tripodding
• breath/heart sounds diminished
• prolonged forced expiratory time

Question 19

Severity of COPD

Answer 19

• GOLD classification. Survival is associated with the FEV1 as well. The lower the FEV1, the poorer the survival.
• Other contributors: severity of symptoms, risk of exacerbations and comorbid conditions.
  
  • Zero to one exacerbation per year is considered low risk for exacerbations, while >= 2 per year is considered high risk for future exacerbations.

Question 20

COPD treatment

Answer 20

• releave sx and reduce severity of exacerbations
• agents to relax airway: inhaled anticholinergics, beta-agonists
• agents to decrease inflammation/edema: corticosteroids
• smoking cessation
• respiratory rehab, O₂ therapy, lung transplant

Question 21

Bronchiectasis characteristics

Answer 21

• abnormal dilation of proximal medium-sized bronchi (cartilage-containing airways)
  
  • destruction of muscular and elastic components of airway walls
• common associated conditions:
  
  • chronic bacterial infection ==> large quantities of foul-smelling sputum
• leads to impaire tracheobroncial clearance ==> predisposes to airway colonization and infection

Question 22

Common causes of bronchiectasis

Answer 22

• severe pulmonary infection
• bronchial obstruction
• primary ciliary dyskinesia
• immunodeficiency
• cystic fibrosis

Question 23

Cystic Fibrosis characteristics

Answer 23

• CFTR mutation ==> dysfxnl chloride transport
• recurrent sinus/pulmonary infections
• PMN recruitment ==> widespread airway inflammation/decstruction ==> bronchiectasis
• respiratory sx, GI sx, failure to thrive
  
  • pancreatitis, diabetes, male infertility
• dx via sweat test

Question 24

Cystic Fibrosis Tx

Answer 24

• CFTR modulators
• antibiotics
• bronhcodilators
• nebulized hypertonic saline
• inhaled DNAase I
• Chest physiotherpay
• exercise
• lung transplant

Question 25

Bronchiolitis characteristics

Answer 25

* inflammation of the membranous bronchioles * children = usually viral illness ==\> fever, cough, dyspnea * adults = toxic gases, immune-mediated, drugs, transplant reject * auscultatory hallmark: inspiratory squeak

Question 26

Upper airway obstruction characteristics

Answer 26

* patterns of obstruction: variable extrathoracic obstruction, variable intrathoracic obstruction, and fixed obstruction