Week 6: Pneumonia Flashcards
4 major categories of microbes that cause disease
bacteria
fungi
parasites
viruses
99% of cultureable bacteria are
anaerobes
Minute ventilation definition
Amount of air inhaled or exhaled per minute
TV x RR
Alveolar ventilation definition
Amount of air reaching alveolus per minute
Dead space ventilation definition
Volume of air inhaled that does not take part in gas exchange
Anatomic deadspace definition
Total volume of conducting airways: mouth/nose to terminal bronchioles
~150 mL average
Alveolar deadspace definition
Volume of air in the alveolus that doesn’t participate in gas exchange
Physiologic deadspace definition
Sum of anatomic and alveolar deadspace
What 4 factors affect the diffusion transport of a gas from alveolar air to pulmonary capillary blood ?
Membrane thickness
Membrane surface area
Pressure difference across the membrane
Diffusion coefficient of gas
What are the 5 etiologies of hypoxemia ?
Hypoventilation Ventilation perfusion mismatch (low VQ ratio) Right to left shunt Low FiO2 Diffusion impairment
Causes of hypoventilation
Impaired central drive
Spinal cord problems
Problems with nerve supplying resp muscle
Problems at neuromuscular junction
Problems with respiratory muscles (myopathy)
Defects in chest wall
Characteristics of hypoventilation
Good response to O2 therapy
P(A-a)O2 is usually normal
PaCO2 high
Most common cause of hypoxemia
VQ mismatch
What causes VQ mismatch ?
All lung diseases
What is the goal of hypoxia pulmonary vasoconstriction
Maintain matching between ventilation and perfusion by reducing perfusion to areas with reduced ventilation
Characteristics of right to left shunt
Poor response to O2 therapy
PCO2 normal
P(A-a)O2 is elevated
What can cause extremely short capillary transit time (a cause of diffusion impairment) ?
High cardiac output
Key anatomic components of the ventilatory pump
Respiratory muscles
Rib cage and abdomen
Cortical and brain stem that control ventilation
Neural connections
Describe airway branching
Trachea —> primary bronchi —> smaller bronchi —> bronchioles —> respiratory bronchioles —> alveolar ducts —> alveolar sacs
Type I vs Type II alveolar cells functions
Main site of gas exchange
Secrete surfactant
What 3 pressures is ventilation dependent on ?
Atmpspheric, alveolar, intrapleural
What happens during inspiration ?
Muscles contract —> increase thoracic volume —> decrease alveolar pressure —> air moves into the lungs
What 3 factors affect ventilation ?
Surface tension of alveolar fluid
Compliance of lungs
Airway resistance
What affect does surfactant have on surface tension ?
Increase surfactant —> decrease surface tension
What is lung compliance ?
How much effort is required to stretch the lungs and chest wall
Tidal volume definition
Amount of air inhaled or exhaled with each breath under resting conditions
inspiratory reserve volume definition
Amount of air that can be forcefully inhaled after a normal tidal volume inhalation
Expiratory reserve volume definition
Amount of air that can be forcefully exhaled after a Normal tidal volume exhalation
Residual volume definition
Amount of air remaining in the lungs after a forced expiration
Total lung capacity definition
Maximum amount of air contained in the lungs after a maximum inspiratory effort
TLC= TV+IRV+ERV+RV
Vital capacity definition
Maximum amount of air that can be expired after a maximum inspiratory effort
VC= TV + IRV + ERV
Inspiratory capacity definition
IC = TV + IRV
Functional residual capacity definition
FRC = ERV + RV
Dalton’s Law
Partial pressures
Henry’s Law
Quantity of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility
Two types of gas exchange and where they take place
Pulmonary
- occurs in alveoli
Systemic
- occurs between systemic capillaries and tissue cells
Conducting structures of the respiratory system
Nasal cavities Nasopharynx, oropharynx, larynx Trachea Bronchi Bronchioles
Respiratory structures of the respiratory system
Respiratory bronchioles Pulmonary alveoli - alveolar ducts -alveolar sacs -alveolus
3 components of conducting airways
Mucosa
-epithelium, basement membrane, lamina propria
Submucosa
-loose connective tissue containing seromucous glands
Adventitia
- outer connective tissue layer
-binds airway to adjacent structures
4 definable layers of the trachea
Mucosa - respiratory epithelium Submucosa - seromucous glands Cartilaginous layer Adventitia - loose connective tissue
Histological differences when bronchi enter the lungs
Rings of cartilage —> irregular cartilage plates
Circular of smooth muscle appears
3 important functions of mucus
Traps bacteria, viruses and foreign material
Antimicrobial properties
Lubricates and protects
Ways that pathogens can evade the immune system
Intracellular invasion Capsule Antigenic variation Immune modulation Immune privileged sites
Common signs and symptoms of infection
Fever (>38C)
Chills, rigours, sweats
Signs of inflammation: pain, erythema, swelling, pus
Lymphadenopathy
Weight loss, fatigue, poor energy and appetite
Typical skin changes or rash
What are the “big 3” that have dramatically improved life expectancy over the past 100 years ?
Improved hygiene
Vaccines
Antibiotics
4 main barriers to infection
Microbial
Chemical
Physical
Immunological
What 3 factors should you consider when you are making a differential diagnosis
Host
Local epidemiology
Exposures
Causes of pneumonia (mechanisms)
Aspiration
Droplet transmission
Hematogenous spread
Top 3 typical causes of CAP
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Top 2 atypical causes of CAP
Mycoplasma pneumoniae
Chlamydophila pneumoniae
Most common cause of CAP in infants and young children
Viral (RSV)
5 common causes of HAP
Strep p. H. Influenzae Staph A. Pseudomonas Eneterobacteraciae
Clinical presentation of pneumonia
Cough
Fever
Dyspnea
Abnormal lung exam: rales, rhonchi, dullness to percussion
Laboratory data for pneumonia diagnosis
Elevated WBC
Abnormal CXR
Maybe respiratory sample
Treatment for healthy outpatient with CAP
Amoxicillin or doxycycline
Treatment for CAP outpatient with co-morbidities
Amoxicillin-clavulanate + azithromycin
Treatment for CAP inpatient
Ceftriaxone + azithromycin
Common Treatment for HAP or VAP
Pipercillin-Tazobactam +/- vancomycin
Drugs for treatment of pseudomonas
PO: Ciprofloxin
IV: pip-taco, ceftazidime, cefepime, meropenem, imipenem
What is the difference between gram positive bacilli and mycobacteria ?
Thicker cell wall
Waxy
Hydrophobic
How long is pulmonary TB treatment ?
Minimum 6 months
Steps to TB infection
- Droplet nuclei containing tubercle bacilli enter lungs and travel to alveoli
- Tubercle bacilli multiply in alveoli
- Small # of tubercle bacilli enter bloodstream —> spread through body
- Macrophages surround tubercle bacilli
- If immune system can’t contain —> rapid multiplication —> TB disease
Basic viral structure
DNA or RNA genes
Capsid
Envelope (sometimes)
Protein molecules
General viral lifecycle
- Attachment
- Entry
- Replication and gene expression
- Assembly
- Release
Characteristics of Influenza
Enveloped Single stranded (-) sense RNA
Proteins on influenza
Hemagglutinin
Neuraminidase
What affect do neuraminidase inhibitors have on viruses ?
Block replication
3 main clinical presentations of adenovirus
Respiratory tract infection
Gastroenteritis
Conjunctivitis
Pneumonia definition
Inflammation of the pulmonary parenchyma
3 anatomical classifications of pneumonia
Lobar
Broncho
Interstitial
Pneumonia predisposing factors (6)
Suppression of cough Impaired systemic immunity Impaired mucociliary apparatus Impaired alveolar macrophage function Pulmonary edema General debility
Pathological stages of lobar pneumonia
Congestion
Red hepatization
Grey hepatization
Resolution
Characteristics of bronchopneumonia
Patchy infective consolidation of the lung in a predominantly lobular distribution
Usually bilateral
Complications of bacterial pneumonia
Bacterial dissemination
Lung abscess formation
Empyema
Death
Pathology of tuberculosis
Macroscopic appearance of cassation necrosis
Microscopic appearance of necrotizing granulomatous inflammation
Pathology of fungal infection in immunocompromised host
Necrotizing pneumonia
Angioinvasion
Consequent tissue infarction
Systemic dissemination