USMLE World Flashcards
In type 1 hypersensitivity, IgE binds to the antigen. What causes the anaphylactic reaction?
IgE’s cross link on pre-sensitized mast cells and aggregate, causing degranulation. Histamine is responsible for most of the effects, but tryptase is also elevated.
Pulmonary reaction to histoplasma
Similar to TB. Fungal spores from bat droppings are inhaled and ingested by alveolar macrophages, where they can be seen as ovoid cells. The immune response is to form granulomata.
Some pts may develop acute pulmonary disease, and those with underlying disease may develop chronic pulmonary histoplasmosis, which resembles TB.
What must always be equal in the systemic and pulmonary circulation?
Blood flow per minute. Doesn’t matter if it is rest or exercising.
How does N-acetylcysteine help in CF?
N-acetylcysteine is a mucolytic agent that cleaves disulfide bonds in mucus glycoproteins
Nosocomial pneumonia, visualized with silver stain, grows on charcoal yeast with cysteine supplementation.
May show hyponatremia, GI, and CNS symptoms
Legionella - contaminates water sources, transmitted by aerosol transmission from the water source.
Tx macrolide or quinolone
Epithelium of the respiratory tract: nose, paranasal sinuses, nasopharynx, oropharyxn, laryngopharynx, larynx, anterior epiglottis, vocal folds.
Pseudostratified columnar: nose, paranasal sinuses, nasopharyxn, larynx, tracheobronchial tree
Stratified squamous: oropharynx, laryngopharynx, anterior and part of posterior epiglottis, vocal folds.
Are the expiratory flow rates in restrictive lung disease increased or decreased? Why
Increased expiratory flow rate
Decreased lung compliance, and increased radial traction exerted on the conducting airways by fibrotic lung
What kind of sweat do you see in CF pts?
These patients cannot resorb Cl and Na in the eccrine ducts, sweat is relatively hypertonic.
What is Cheyne Stokes breathing?
A breathing pattern seen in CHF. Apnea, increasing tidal volume, decreasing tidal volume, apnea, etc. Due to delayed feedback, leading to overcompensation.
What cells are responsible for protease and elastase release in centriacinar emphysema?
Macrophages and neutrophils. Neutrophils also generate free radicals which inhibit anti-protease activity.
Pt presents with triad of hypoxemia, confusion, and petechial rash in the setting of long bone fracture. Dx?
Fat embolism. Can cause respiratory distress, thrombocytopenia, and anemia. Fat emboli can be stained with osmium tetroxide.
Middle aged patient with sudden onset dyspnea and calf swelling.
Pulmonary embolism
pH, PaO2, PaCO2, and plasma bicarb expected in PE
Hypoxemia leads to hyperventilation and respiratory alkalosis. Increased pH, decreased PaO2, PaCO2.
High altitude: pH, PaO2, PaCO2, plasma HCO3-
Hypoxia stimulates body to increase ventilatory drive. Leads to respiratory alkalosis, increasing pH and decreasing PaCO2. Low bicarb by compensation, and low-ish oxygen.
What is the driver of respiratory regulation in health people? In people with longstanding COPD?
Normal: PaCO2 is major stimulator through central medullary respiratory center (pH and PaO2 are less important until you get profound hypoxemia)
COPD: Prolonged hypercapnia leads to PaCO2 no longer driving. PaO2 sensed in the peripheral chemoreceptors (eg carotid body) stimulate respiration.
Bronchiolitis obliterans
Chronic rejection after lung transplant affecting small bronchioli. An obstructive lung disease.
Lymphocytic inflammation, necrosis of bronchiolar walls, and fibrosis. Finally leading to occlusion of bronchiolar lumen
Cause of spontaneous pneumothorax, classic presentation
Caused by rupture of apical subpleural blebs.
Sudden onset unilateral chest pain with hyperresonance and absent breath sounds in a tall, thin male around 20 y/o.
How might one’s lungs be hosting species such as peptostreptococcus and fusobacterium?
These are normal oral flora. Can get in by aspiration or seizure disorder, which can cause aspiration. Lung abscesses often contain oral flora
