Resp Tract Flashcards
What is pneumonia?
Infxn of lung parenchyma
How do people become susceptible to pneumonia? Give 3 examples and explain why each would increase the risk of a person getting pneumonia.
- Pneumonia occurs when normal defenses are impaired
- Examples:
1. Impaired cough reflex: Pt won’t be able to cough up organisms that may have gotten into the airways
2. Mucociliary escalator: Resp. epith has cilia that beat upwards to push mucus in the conducting portion of lung up along the airway and into the throat so that we can swallow it
3. Mucus plugging: whenever you have a block of a tube, you increase risk of infxn behind the block
How would a patient w/ pneumonia present clinically? (7 physical symptoms)
- Fever
- Chills
- Productive cough (yellow-green or rusty sputum)
- Pleuritic chest pain
- Tachypnea
- Decreased breathing sound
- Dullness to percussion
What causes the pleuritic chest pain seen in pneumonia?
Bradykinin and PGE2 are released during inflamm response, which sensitizes the sensory neurons for pain
What are 3 patterns of pneumonia that are classically seen on chest x-ray? Describe what changes in the lung would be seen in each type.
- lobar pneumonia: Consolidation of an entire lobe of the lung
- bronchopneumonia: Scattered patchy consolidation centered around bronchioles (often multifocal and bilateral)
- interstitial (atypical) pneumonia: Diffuse interstitial infiltrates
What is usually the etiology of lobar pneumonia? What are the most common causitive organisms?
- Usually bacterial
- Most common causes are: Strep pneumonia (~95%) and Klebsiella pneumoniae (~5%)
What is the causitive organism that is responsible for most community-acquired pneumonia cases? What patient population is generally affected?
- Strep pneumoniae
- Usually seen in middle-aged adults and elderly
What type of pneumonia (lobar, broncho, intersitial, or aspiration) would patients present with coughing up a jelly-like sputum? What is the causitive agent and why does it cause this type of presentation?
- Lobar pneumonia
- Klebsiella pneumoniae; Klebsiella has a thick mucoid capsule –> attracts water and makes it viscous –> Pt who cough this up will describe it as having a jelly-like consistency
What types of patients are most susceptible to lobar pneumonia caused by Klebsiella? Why?
- Alcoholics and elderly in nursing homes
- Klebsiella is normally found in the GI, but it can cause pneumonia if aspirated into the lungs –> Pt’s who are @ increased risk of aspiration would therefore be more susceptible to lobar pneumonia caused by Klebsiella
What are the 4 classic gross phases of lobar pneumonia? Explain how each arises.
- Congestion: inflammation increases leakiness of vessels –> leads to congested vessels and edema
- Red hepatization: Alveolar air space becomes filled w/ exudate + neutrophils + hemorrhage –> changes the lung from having a normal spongy consistency to one that is closer to the liver
- Gray hepatization: RBCs w/n the exudate begin to degrade –> changes the color from a dark red/blackish color to gray
- Resolution and healing: Healing is mediated by Type II pneumocytes, which act as the stem cells of the alveolar air sack
What is a complication of Klebsiella pneumoniae that commonly arises?
Abscess formation
What organism is the most common cause of bronchopneumonia?
Staph. aureus
What is secondary pneumonia? What are the most common organisms that cause secondary pneumonia?
- Secondary pneumonia is bacterial pneumonia that is superimposed on an existing viral URI
- Strep pneumoniae and Staph aureus
What organism is a common cause of secondary bronchopneumonia and pneumonia superimposed on COPD?
H. influenzae
What organism causes community-acquired pneumonia and pneumonia superimposed on COPD?
Moraxella catarrhalis
What is the most common cause of bronchopneumonia in cystic fibrosis patients?
Pseudomonas aeruginosa
What intracellular organism transmitted by water source causes community-acquired pneumonia, pneumonia superimposed on COPD, or pneumonia in immunocompromised states? How is it visualized?
- Legionella pneumophila
- Silver stain
Why is intertitial pneumonia also called atypical pneumonia?
Intersitial (atypical) pneumonia has “atypical” clinical symptoms in comparison to other forms of pneumonia. For example, Pts would present w/ mild upper respiratory symptoms (minimal sputum and low fever) than would be expected of Pts who have other forms of pneumonia
What is the most common cause of atypical pneumonia? What patient population is most affected by this organism?
- Mycoplasma pneumoniae
- Young adults (classically, military recruits or college students living in close quarters)
Mycoplasma pneumoniae is the most common cause of what type of pneumonia? What complications can arise in Pts who are infected with this organism?
- Interstitial (atypical) pneumonia
- Autoimmune hemolytic anemia: IgM-mediated (cold agglutinin) against I antigen on RBCs
What is the second most common cause of atypical pneumonia in young adults?
Chlamydia pneumoniae
Chlamydia pneumoniae causes what type of pneumonia? What patient population is most at risk?
- Intersitial (atypical) pneumonia
- Young adults
What is the most common cause of atypical pneumonia in infants?
Respiratory syncytial virus (RSV)
What is the most common cause of atypical pneumonia in Pts w/ posttransplant immunosuppressive therapy?
CMV
What is the most common cause of atypical pneumonia in elderly, immunocompromised, and those w/ preexisting lung disease?
Influenza virus
What is the most common cause of mortality in Pts w/ atypical pneumonia due to influenza virus?
Superimposed S aureus or H influenza bacterial pneumonia is the most common cause of death in Pts w/ atypical pneumonia due to influenza virus
What organism is assoc w/ atypical pneumonia with a unique characteristic of causing high fever (Q fever) in Pts?
Coxiella burnetii
What patient population is most susceptible to pneumonia caused by Coxiella burnetii? What is unique to this organism in comparison to other organisms in the same genus?
- Farmers and veterinarians (since the spores are deposited on cattle by ticks or are present in cattle placentas)
- Coxiella is a rickettsial organism, but it is distinct from others in that:
1. It causes pneumonia
2. does not require an arthropod vector for transmission (survives as a highly heat-resistant endospore)
3. does not produce a skin rash
What is aspiration pneumonia? What complication classically arises in this form of pneumonia?
- Pts may aspirate into their lungs anaerobic bacteria of the oropharynx, which could cause pneumonia
- Classically, this results in right lower lobe abscess
Give 3 examples of anaerobic bacteria present in the oropharynx that may cause aspiration pneumonia.
- Bacteroides
- Fusobacterium
- Peptococcus
How is tuberculosis (TB) transmitted?
TB is trasmitted via inhalation of aerosolized Mycobacterium tuberculosis
What microscopic changes are seen in primary TB? Clinically, how would the Pt present?
- Primary TB results in focal, caseating necrosis in the LOWER lobe of the lung and hilar lymphnodes; fibrosis and calcification can also be seen subpleurally (Ghon complex)
- Clinically, Pts will generally be asymptomatic, but will present with (+) PPD
How does Primary TB progress to Secondary TB?
Primary TB arises after initial exposure; Secondary TB arises due to reactivation of Mycobacterium tuberculosis due to AIDS or aging
What histological changes are seen in secondary TB of the lung? How would Pts present clinically?
- Secondary TB would form foci of caseous necrosis @ the APEX of the lung (since there is relatively poor lymphatic drainage here and high O2). This may progress to miliary TB (tiny regions of TB which are scattered across the entire lung) or tuberculous bronchopneumonia
- Pts would present w fevers and night sweats, cough w/ hemoptysis, and weight loss
In secondary TB, what complications may arise from the reactivation of TB and ongoing caseous necrosis?
- Miliary pulmonary TB (where tiny regions of TB are scattered across the entire lung)
- Tuberculous bronchopneumonia
What would a biopsy in secondary TB reveal? What type of stain could be used to visualize the baccili?
- Caseating granulomas: would see central necrosis and surrounding it would be hisitiocytes
- Acid-Fast-Bacilli (AFB) stain: would show as red rods
Systemic spread of secondary TB can involve any tissue. Give 4 examples of common sites.
- Meninges (meningitis; specifically affecting the meninges @ base of the brain)
- Cervical l.n.
- Kidneys (sterile pyuria)
- Lumbar vertebrae (Pott disease)
In COPD, what changes are seen in spirometry (FEV1:FVC ratio; TLC)
- FEV1:FVC ratio decreases (both FEV1 and FVC decrease, but FEV1 decreases more since Pt is unable to effectively blow out air in COPD)
- TLC: TLC increases b/c air trapping means more air will be present in the lungs than normal @ any given time
Copious amounts of mucus is coughed up in what particular COPD? What is the cause of this?
- Chronic bronchitis
- (highly assoc w/ smokers) Pts who smoke breathe in a lot more pollutants –> Mucinous glands in the submucosa layer of bronchus undergoes extensive hypertrophy/hyperplasia in attempt to better filter the air –> Copious amounts of mucus is produced, which travel up the airway and can be coughed out
What changes in the Reid index would be expected in chronic bronchitis?
Reid index measures the thickness of mucinous glands in relation to the thickness of the entire bronchial wall: normally, it is <40%, but in chronic bronchitis, it will increase to >50%
How can chronic bronchitis cause cyanosis?
Copious mucus production may travel down into airways and produce a mucus plug –> this traps CO2, thereby increase PACO2 and reducing PAO2 –> leading to a increase in PaCO2 and decreasing PaO2
“Blue Bloaters” is a HY word to describe cyanosis seen in what specific COPD condition?
Chronic bronchitis
What cardiovascular disease can be precipitated by COPD conditions? How does this happen?
In COPD conditions, hypoxia results from the inability to blow out air properly –> arterioles in the lungs vasoconstrict in an attempt to shunt blood to other parts of the lung that may be better oxygenated; however, in COPD, oxygenation is compromised in most areas of the lung –> this causes pulm. HTN –> RV has to pump against this increased pressure –> RV hypertrophy –> RH failure (cor pulmonale)
What is the physiological cause of emphysema?
There is destruction of alveolar air sacs due to loss of elastic recoil and collapse of airways during exhalation –> leads to obstruction and air trapping
Explain the physiological process by which there is air trapping and collapse of airways in emphysema.
- Air trapping: Normally, alveoli expand during inhalation and recoil in order to push the air out during exhalation. However, in emphesema, this elastic property is lost (“instead of having a bunch of small balloons, it’s like having a big shopping bag”) –> air is unable to be pushed out effectively
- Collapse of airways: As air goes from distal to proximal lung during exhalation, it gradually accelerates (“recall that area is related to velocity; although the terminal bronchioles may individually be smaller than larger bronchi, there are many more of them = much larger surface area”) –> this causes a drag force that tries to collapse the airway –> normally, this drag force is resisted in the upper airways by the cartilage and it is resisted in the lower airways by the recoil of alveoli that keep the airway open –> in emphysema, loss of elastic recoil means there is no counterbalancing force in the terminal bronchioles = airway collapse during exhalation
What is the molecular reason for emphysema?
There is always some underlying inflamm in the lower lungs due to debris in the air –> alveolar macrophages clean this debris, but in the process of inflammation, they release proteases (specific to emphysema is elastase) –> liver produces alpha1-antitrypsin (A1AT), which travels via blood into lungs and neutralizes the elastase and protects it from dmging the lung parenchyma
- In emphysema, there is either excessive inflammation (increased protease) or lack of A1AT (genetic deficiency)
What is the most common cause of emphysema?
Smoking
What type of emphysema is characteristic of smokers?
Centriacinar emphysema that is most severe in upper lobes (as smoke comes down the airway, the first part of the acinous that gets hit with the brunt of it is the center; smoke travels upward, hence upper lobes is most severely affected)
What type of emphysema is characteristic of A1AT deficiency?
Panacinar emphysema that is most severe in lower lobes
What liver symptoms could be seen in panacinar emphysema? Why is this the case?
- Liver cirrhosis
- Panacinar emphysema is caused by A1AT deficiency. However, the disease is caused b/c there is insufficint levels of circulating A1AT, not b/c it is not being made in the liver. The liver is making misfolded A1AT, which is why it becomes sequestered in the ER –> accumulation of mutant A1AT results in liver dmg –> liver cirrhosis
In a Pt w/ panacinar emphysema, what would be seen on liver biopsy?
Pink, PAS-positive globules in hepatocytes (the pink/purple globules are the non-fxnal sequestered A1AT in the ER of hepatocytes)
What are the 2 most common alleles of A1AT?
PiM is the normal allele (2 copies are usually expressed: PiMM)
PiZ is the most common clinically relevant mutation that results in low levels of circulating A1AT and sequestration in ER
What COPD condition is associated w/ Pts having a “pink-puffer” presentation? Why do these Pts present this way?
- Emphysema
- “pink-puffer” is a description of how Pts w/ emphysema have pursed-lip breathing. Careful breathing with pursed lips increases back pressure –> keeps the walls of airways from collapsing
What changes in chest wall can be seen in Pts w/ emphysema? Why does this occur?
- Barrel-chest can be seen (increase in anterior-posterior diameter of chest)
- The chest wall has a tendency to want to expand out and the lungs have a tendency to want to collapse in. Normally, these two opposing forces are counterbalanced (fxnal residual capacity; think of it as Chest wall: Lung ratio). In emphysema, due to loss of elastic recoil, the opposing force by the lung is reduced –> FRC increases –> barrel chest
The clinical presentation of barrel chest is associated w/ what COPD condition?
Emphysema
What is asthma? What is it most often caused by?
- Asthma is reversible airway bronchoconstriction (not spasm)
- Most often due to allergic stimuli (atopic asthma; Hypersensitivity Type 1)
If asthma presents in childhood, what other comorbidities does it present w/?
Childhood asthma is often assoc w/ allergic rhinitis, eczema, and a family Hx of atopy
Explain the pathogenesis of atopic asthma.
- Allergens induce a TH2 CD4+ response in genetically susceptible individuals
- TH2 CD4+ cells secrete IL-4, IL-5, and IL-10 –> IL-4 mediates class switching to IgE; IL-5 attracts eosinophils; IL-10 potentiates TH2 response
- Reexposure to allrgen leads to IgE-mediated activation of mast cells (APCs w/ IgE will present a cross-linked allergen upon second exposure to mast cells) –> Acivated mast cells release preformed histamin granules (causes vasodilation and increased vascular permeability) and generate LTC4, LTD4, and LTE4 (causes constriction of smooth muscles = leads to increased vascular permeability by contracting pericytes and bronchoconstriction)
- Arrival of eosinophils exacerbates and perpetuates bronchoconstriction (late-phase of asthma reaction) via the release of major basic protein
What unique features are seen in the productive cough of asthmatic Pts?
Sputum of Pts w/ asthma would classically have: Curschmann spirals (spiral-shaped mucus plugs) and Charcot-Leyden crystals (crystal aggregates of major basic protein)