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Flashcards in USMLE World Deck (46)
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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.


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.


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


How do lung abscesses happen? (3 ways)

1. Aspiration (increased risk with any loss of consciousness)
2. Complication of bacterial pneumonia, especially in nosocomial pneumonias of old or immunocompromised. S aureus, E. coli, klebsiella, or strep pneumonia
3. Hematogenous spread of infection from endocarditis. Staph, strep, ecoli, fungus


Major causes of pulmonary artery hypertension

Idiopathic hereditary (BMPR2 gene, vascular smooth muscle proliferation); Left heart failure; Chronic hypoxia (COPD, OSA); chronic thromboembolism; HIV


CF effects on pancreas

Sever CF may cause total obstruction and fibrotic atrophy. Pancreatic insufficiency then causes deficiency of fat soluble vitamins (ADEK).

Low vitamin a causes squamous metaplasia


How does the vagus nerve affect the lungs?

Increases bronchial smooth muscle constriction --> increases work of breathing. Increases bronchial secretions --> increases airflow resistance => increases work of breathing.

Via M3 receptor.


What are the 4 stages of lobar pneumonia?

Congestion (first 24 hours)
Red hepatization (days 2-3)
Gray hepatization (days 4-6)


Lobar pneumonia congestion stage: macroscopic and microscopic appearance

Macroscopic: lobe is red, heavy, boggy
Micro: vascular dilation, edema, alveolar exudate of mostly bacteria


Lobar pneumonia red hepatization stage: macroscopic and microscopic appearance

Macro: red, firm, liver-like
Micro: exudate contains RBCs, neutrophils, fibrin


Lobar pneumonia, gray hepatization stage: macroscopic and microscopic

Macro: gray-brown, firm
Micro: RBCs lyse, exudate contains neutrophils and fibrin


Lobar pneumonia, resolution phase

Restoration of normal architecture, enzymatic digestion of exudate


What is the most common cause of meconium ileus?



Where is the fetal blood richest in oxygen content?

Mom - umbilical vein - liver (ductus venosus) - IVC - heart - tissues - umbilical arteries


At what point is the fetal lung considered to be mature?

When the lecithin to sphingomyelin ratio is > 2.

Note: lecithin is aka phosphatidylcholine.