Path: Lung and Renal Flashcards
What is the mechanism of barotrauma while diving?
Air spaces in the body are compressed at increased depth, which can cause tissue injury if normal volumes are not restored.
Can cause: eardrum rupture, dental pain, lung squeeze, pneumothorax, or air gas embolism
What is nitrogen narcosis?
Gas percentage at depth stays constant, but partial pressures increase with total pressure. This causes more nitrogen to be dissolved in blood at greater depths. As pN2 increases, effects increase in intensity. Mild intoxication, drunk equivalent, auditory/visual hallucinations, and finally loss of consciousness.
How does O2 cause problems at depth?
Similar to N2, increased pressure causes an increased amount of O2 to be dissolved in blood. As the amount increases, CNS and pulmonary toxicity can ensue. This is mitigated by reducing O2 percentage at depth or taking air breaks.
How do dissolved gases cause problems for divers?
As the partial pressure of a gas in the lung increases, the amount of that gas in the tissue increases, and vice versa. When returning from depth, the gas in the tissue cannot be transported away quickly enough. The gas then comes out of solution in the tissue or venous blood, causing harmful bubbles (“the bends”). These bubbles cause problems if they reach the arterial circulation, perhaps through a patent foramen ovale.
What is the mechanism by which bubbles in decompression sickness (the bends, or DCS) cause damage to tissue?
- stretching tissue and directly blocking blood flow.
- activation of Hageman factor and subsequent activation of kinin and complement system, platelet aggregation, vascular permeability, and relative ischemia.
How does decompression sickness (DCS) present? How are cases treated?
Depends on where the bubbles occur. Joint pain, neurologic decompensation (divers: spinal; aviators: brain), lung problems (dyspnea, nonproductive cough, substernal pain), cutaneous rash.
Responds to hyperbaric O2 therapy
How does flying DCS differ from diving DCS?
Air expands on ascent, which may cause pain at altitude (gut, intracranial, intraocular, intrathoracic, tooth abscess). If atmosphere drops to 50% of ambient, N2 can bubbles out of solution.
What are the symptoms of altitude sickness?
decreased exercise tolerance (10%@5000ft, 10% per subsequent 1000ft)
decreased alcohol tolerance
increased fluid loss (respiratory and urinary)
disturbed sleep
periodic breathing
resp alkalosis => apnea => incr. CO2, decr. O2 => hypervent
altered judgment
What illnesses are possible to due altitude?
- peripheral edema
- thromboembolism
- retinopathy
- acute mountain sickness (AMS)
- high altitude pulmonary edema (HAPE)
- high altitude cerebral edema (HACE)
What are the symptoms of acute mountain sickness (AMS)?
- throbbing, bi-temporal headache
- axorexia, possibly associated with nausea
- fatigue, 25% with rales (dyspnea at rest suggests HAPE)
- dizziness (when severe or with ataxia suggests HACE)
- difficulty sleeping
How does one prevent and treat altitude illness?
Prevent: slow ascent, supplemental O2, avoid alcohol/sedatives
Medications: acetazolamide, dexamethasone, phosphodiesterase
What are the symptoms of high altitude cerebral edema (HACE)?
- ataxic gate (defines)
- severe lassitude
- altered consciousness (confusion, drowsiness, stupor, coma)
- headache, nausea, vomiting
What causes high altitude cerebral edema (HACE)?
Normal brain autoregulation in an abnormal environment.
- brain increases blow flow to compensate decr. O2 content
- increased flow causes increased hydrostatic pressure leading to edema, causing regional ischemia and cell death
What are the symptoms of high altitude pulmonary edema (HAPE)?
- dyspnea at rest
- persistent dry cough and fever
- cyanosis
- HACE/AMS symptoms
- often affects the fittest individual
What causes high altitude pulmonary edema (HAPE)?
- Normal low ventilation response in an abnormal environment
- decreased O2 causes vasoconstriction throughout lungs => pressure rises to systolic levels => pressure causes fluid leak across membrane (climber’s pneumonia)
What pathogens commonly cause disease in the nasopharynx?
mainly viruses, i.e. rhinoviruses, coronaviruses, etc.
What pathogens commonly cause disease in the oropharynx?
streptococcus pyogenes (GAS) corynebacterium diptheriae Epstein-Barre virus adenovirus enterovirus
What pathogens commonly cause disease in the middle ear and parasinuses?
streptococcus pneumoniae
haemophilus influenzae
also, streptococcus pyogenes (GAS)
What pathogens commonly infect the epiglottis?
haemophilus influenzae type b
What are the major features of streptococcus pyogenes (GAS)?
- Gram+ cocci that tend to occur in chains
- catalase negative (distinguishes strept. from staph.)
- beta-hemolytic on blood agar plates (pale)
What disease states are associated with strept. pyogenes (GAS)?
Suppurative
- pharyngitis (uncommonly w/ scarlet fever)
- pyoderma (impetigo, erysipelas, cellulitis, necrotizing fasciitis)
- Non Suppurative streptococcal disease
What are the symptoms of pharyngitis?
nausea, vomiting, abdominal pain, oropharyngeal inglammation, petichiae
What are the complications of pharyngitis?
peritonsillar abscess, scarlet fever, cervical adenitis, otitis media, streptococcal toxic shock syndrome
How is streptococcus pyogenes infection related to rheumatic heart disease?
M-protein (on the surface of strep pyo.) mimics molecules found in the leaflets of the heart valves. These antibodies create deposits and fibrosis of the valves of the heart.
What are the characteristics of haemophilus influenzae?
- Gram-
- coccobacilli (curved ends on short rods)
- requires X (hemin) and V (NAD or NADP) to grow (chocolate agar)
What H. influenzae strain is responsible for the majority of disease in humans? What is the antigen associated with this capsule?
H. Influenzae type B
polyribose-ribitol phosphate (PRP or Hib)
What disease states are associated with H. Influenzae infections?
-meningitis: primarily toddlers who are not vaccinated
-epiglottitis: obstructive, cherry red epiglottis
-pneumonia
Others: bacteremia, cellulitis, septic arthritis
How does one treat H. influenzae infections?
3rd gen cephalosporins, switch to ampicillin if organism is susceptible
How can young infants be vaccinated to prevent disease?
Hib-conjugate vaccines. Babies’ immune systems cannot form antibody to carbohydrate, however the Hib carbohydrate antigen can be coupled to a protein, such as diptheria toxin
what is the causative agent of diphtheria?
Corynebacterium diptheriae
What is the pathogenesis of diphtheria?
organism colonizes mucosa => produces diphtheria toxin => causes necrosis and the formation of a pseudomembrane => death by obstruction
What types of infection does non encapsulated haemophilus cause?
- otitis media
- sinusitis
- conjunctivitis
What are the characteristics of corynebacterium diphtheriae?
- Gram+ rods
- form “chinese letters”
- catalase+
What are the primary viruses that cause the common cold?
rhinoviruses
What are the primary viruses that cause pharyngitis?
adenovirus
Epstein-Barre Virus (EBV)
What are the general characteristics of rhinovirus?
- non enveloped
- +ssRNA genome (RNA replicates in cytoplasm)
- more than 100 serotypes
- ICAM-1 is the primary infectious cell receptor
- flourishes best at 88-90 deg F (the nose)
What is the pathogenesis of respiratory syncytial virus?
- infections lasts 7-10 days
- runny nose
- fever
- rapid breathing
- wheezing and/or loud whistling on exhale
- breathlessness
- abdominal contraction while breathing
- continuous coughing
- lips turn blue
- immunity does not last long => repeat infxns possible
What are the characteristics of respiratory syncytial virus?
- enveloped
- -ssRNA genome (replicates in cytoplasm)
- helical capsid
- two major envelope proteins: F = fusion protein; G = attachment
- encodes its own RNA-dependent RNA polymerase
What does “syncytial” in RSV’s name mean?
It indicates that the disease forms syncytia. These are cytoplasmic masses or cells with multiple nuclei/inclusions.
How is respiratory syncytial virus diagnosed?
DFA, IFA, or ELISA are used to detect antigen in nasal washing/aspirates/swab samples.
Viral culture is carried out in certain cell lines.
What are useful first line drugs against tuberculosis?
- isoniazid
- rifampin
- rifapentine
- rifabutin
- ethambutol
- pyrazinamide
What respiratory diseases can be caused by adenovirus?
- febrile, undifferentiated URTI (young children and infants)
- pharyngoconjunctival fever
- acute respiratory disease (military recruits esp.)
- pertussis-like syndrome (infants, young children)
- pneumonia (infants, young children, military recruits, immunocompromised patients)
What cells does epstein-barre virus target to replicate in?
epithelial and B cells
What is a disease caused by epstein-barre virus (EBV) that commonly affects adolescents?
infectious mononucleosis
What is the general structure of epstein-barre virus (EBV)?
- enveloped
- linear dsDNA (replicates inside nucleus)
- large genmone, encodes numerous proteins for replication and immune evasion
- CD21 is the prinary receptor
What is the pathophysiology of infectious mononucleosis?
The virus infects B cells, which are then killed by CD8+ T cells in the acute phase. This makes the host immune compromised. Some of the infected cells may survive, and create a persistent phase.
What are the symptoms of infectious mononucleosis? Which of these occur in nearly every case?
- soreness and reddening of throat**
- cervical lymphadenopathy**
- atypical lymphocytosis**
- reddened, swollen tonsils with white patches
- fatigue, malaise, loss of appetite, headache
- cough
- splenic enlargement and pain
How is infectious mononucleosis diagnosed?
- atypical lymphocytes (irregular borders)
- agglutination test for herterophile antibodies
- EBV antibody ELISA
- PCR for EBV genes
What are the major components of the mycobacterial cell envelope?
- waxes
- mycolic acids
- polysaccarides
- peptidoglycan (murein)
- phenolic glycolipid I (PGL-1)
- lipoarabinomannan (LAM)
How is TB transmitted?
- inhalation
- ingestion via contaminated milk/milk products (M. bovis)
Describe the stages of Pulmonary TB
Stage 1: inhalation and seeding into the mid/lower lung
bacteria multiply in alveolar space
macrophages ingest bacteria (some killed, some grow)
Stage 2: logarithmic growth of bacteria in phages (kill by lysis)
arrival of new macrophages, and subsequent infxn
infected phages spread through bloodstream
Stage 3: bacterial growth finally countered by CD8+ CTL
formation of granulomas and ghon complexes at primary
infxn site
Stage 4: bacterial multiply within granulomas, protected from
immune response
granulomas become necrotic
lesions heal, but organisms may remain viable
What groups are at high risk for TB infection or exposure?
- close contacts with people known or suspected to have TB
- foreign born people from areas where TB is common
- residents and employees of high risk congregate settings (retirement homes)
- health care workers who serve high risk clients
- medically underserved, low income populations
- high risk racial or ethnic populations
- children exposed to adults in high risk categories
- people who use illicit IV drugs
What groups are at higher risk for developing disease after being infected with TB?
- HIV infected
- recently infected
- people with certain medical conditions (immune comp, etc)
- illicit IV drug users
- history of poorly treated TB
How is TB diagnosed?
- sputum smear
- culture (gold standard; takes 2-3 weeks to form colony)
- tuberculin skin test (Mantoux or PPD)
What is the pathogenesis of a primary influenza infection?
- short incubation period
- virus replicates locally in respiratory epithelium
- damage to the epithelium and ciliated columnar cells causes susceptibility to bacterial infection
- no viremia
- macrophage and lymphocyte infiltration
- interferons and cytokines cause fever, aches, edema
- direct virus damage and immune response kills infected cells
- antibodies and virus specific T cells formed
- virus cleared
- IgA in respiratory tract mediates immunity to reinfection by same strain
Why do we take cultures even if they take so long to develop?
- drug susceptibility testing
- genotyping
What are two possible outcomes of a secondary influenza virus infection?
- asymptomatic, limited infection mediated by IgA
2. mild symptoms, but still sheds enough virus to infect others
What are the clinical features of influenza virus?
- abrupt onset
- headache
- high fever(100-103 degF)
- chills
- myalgia
- malaise
- sore throat
- non productive cough
- runny or stuffy nose
What are three possible complications of influenza infection?
secondary bacterial pneumonia: following improvement, fever reappears, cough,purulent sputum (S. pneumoniae, S. aureus, H. influenzae)
viral pneumonia: relentless progression of illness, dyspnea, hypoxia, cyanosis, severe alveolar inflammation,edema => ARDS
CNS or muscle involvement
What are the high risk populations for influenza complications?
- people over 65yo
- nursing home residents (& other chronic care facilities)
- anyone with a chronic pulmonary or CV disorder (incl. asthma)
- anyone who requires regular medical follow-up/hospitalization
- anyone 6mo-18yo who has long term aspirin therapy (Reye Syn.)
- women in the 2nd or 3rd trimester during flu season
What are the general characteristics of influenza virus?
- -RNA virus
- enveloped
- haemagglutinin and neuraminidase spikes
What are the three types of influenza virus, and which undergo antigenic shift and drift?
Type A: shit and drift
Type B: drift only
Type C: stable (no disease in humans)
What are the functions of the M2 ion channel, hemagglutinin, and neuraminidase in influenza virus?
hemagglutinin (HA): viral attachment and membrane fusion
neuraminidase (NA): virus release and disaggregation
M2: facilitates virus disassembly and HA maturation
What triggers hemagglutinin conformational change and virus release in the cell?
low pH (when bound to an endosome)
How is influenza virus diagnosed?
- isolated from clinical specimens (throat swab/wash, nasal wash, nasopharyngeal aspirate)
- virus grown in eggs or cell cultures
- serotype determined
OR
-rapid diagnosis by RT-PCR based tests
What is antigenic shift and drift?
shift: occurs as segments of the virus genome are rearranged in large animal reservoirs
drift: occurs when mutations are introduced during replication
What are the two types of influenza vaccination?
trivalent inactivated virus (TIV) -intramuscular injection -chemically inactivated -induces serum antibodies -6mo and older live attenuated influenza vaccine (LAIV) -nasal spray -induce mucosal immunity (IgA) -5-49yo (healthy)
What proteins on influenza are the target of antiviral therapies, and what drugs are associated with each?
neuraminidase (NA): prevents viral release
-oseltamivir
-zanamivir
M2 ion channel: block channel and prevent H+ entry and viral disassembly
-amantadine
-rimantadine
What is the presentation of a typical pneumonia?
high fever
shaking chills
chest pain
lobar consolidation on CXR