Lower Respiratory Tract Infections (LRIs) Flashcards
Unlike URIs that are common, LRIs are…
Respiratory tract infections remain a major cause of morbidity from acute illness in the North America
- single most common reason patients seek emergency medical attention
What is the reason why we don’t have more infections?
b/c of host defenses
The respiratory tract has an elaborate system of host defenses, including humoral immunity, cellular immunity, and anatomic mechanisms
• Infections only occur when host defenses are impaired
What are the 3 most common LRIs?
- Bronchitis
- Bronchiolitis
- Pneumonia
Are URIs and LRIs linked?
URI lead to most common LRIs (drain downward)
- moving more infective agent lower into lung tissue
• majority of pulmonary infections follow colonization of the upper respiratory tract with pathogens, where they gain access to the lung via aspiration of OROPHARYNGEAL SECRETIONS
• Less common, microbes enter the lung via the blood from an extra pulmonary source or by inhalation of infected aerosolized particles
What are the variety of host factors that determines if an infection is caused by an invading microorganism?
• patient age (v. young & v. old most commonly)
• lifestyle/ habits (smoking, vaping, workplace, etc.)
• anatomic features of the airway (surgeries , damage, etc. that affected lung tissue & lead to scarring that makes them more susceptible)
• specific characteristics of the infecting agent (if highly variant, highly pathogenic it can make even a v. healthy person sick)
What do most LRIs in children and adults most commonly result from?
either viral or bacterial invasion of LUNG PARENCHYMA
What is lung parenchyma?
lower ends of bronchioles, leading to alveolar sacs (severe –> O2 isn’t carried to blood)
What is Bronchitis?
is an inflammatory condition of the large and small airways→the tracheobronchial tree (large/major valves leading to lungs)
• excludes alveoli
When does Bronchitis occur?
Occurs year-round, but more commonly peaks during
the winter months (when cold/flu season increase)
What are the 2 types of Bronchitis?
- Acute bronchitis (AB)
- Chronic bronchitis (CB)
Acute bronchitis (AB) =
inflammation of the epithelium of the large airways resulting from infection or smoke inhalation
• AB symptoms are short-lived and last <1 month (b/c starts with URI & goes downward usually)
(ex: coal miners or smokers)
Chronic bronchitis (CB) =
chronic cough producing sputum lasting more than 3 months for 2 consecutive years without an underlying etiology of bronchiectasis or tuberculosis
What is the predominant infectious agents associated with AB accounting for 85% to 95% of occurrences?
Respiratory viruses
a primary bacterial etiology for AB is rare (b/c lots of mech’s to prevent it going down)
*secondary bacterial infections may be involved in patients with underlying disease(s) = co-morbidity
LRIs start as _____, but become problem if it becomes ______ (& if it is co-morbidity)
viral
bacterial
What are Acute Bronchitis Signs and symptoms?
starts as a URI
cough?
if yes, Cough may persist for up to 3 or more weeks
• Painful Cough +/- mucopurulent sputum
than it is AB
if no, than it is URI
Which infections are fevers most common in?
adenovirus, influenza virus, and M. pneumoniae infections
How do you diagnose Acute Bronchitis?
made on the basis of a characteristic history and physical examination, and should be differentiated from asthma or bronchiolitis
• these diseases are usually associated with WHEEZING, shortness of breath (DYSPNEA), and HYPOXEMIA (low of oxygenation)
What is the best diagnose/treatment plan for AB?
For majority of affected patients, an etiologic diagnosis is unnecessary and will not change the prescribing of routine supportive care
• Hydration, anti-pyretic/ analgesic (Aspirin or Acetaminophen), vaporizers (hydrate & maintain broncial airway function)
• COPD patients experiencing an acute exacerbation benefit from a short course of corticosteroid treatment (lower inflammation)
(bacterial cultures are no good b/c of contamination, and viral cultures are unnecessary unless COPD, congestive heart failure &/or immunocompromisation is there)
What is the bacterial AB treatment plan?
When possible, antibiotic therapy should be directed toward the anticipated respiratory pathogen(s)
• due to the increasing antimicrobial resistance, antibiotics should be only be administered upon culture serology or PCR confirmation in patients not responding to supportive care
What is the Viral AB treatment plan?
antiviral drug combinations are being explored as a treatment approach (b/c resistance is growing for antivirals)
Annual flu vaccination is recommended (depends on the formulation each year)
What is Bronchiolitis?
is an acute viral infection of the lower respiratory tract bronchioles that affects approximately 50% of children during the first year of life and 100% by 2 years of age
- b/c their bronchioles are v. narrow so even a small amount of inflammation can be severe
When does Bronchiolitis peak? & what is it a major cause of? & who does it affect
Peaks during winter months
of hospitalizations within 1st year of life
Also affects elderly and immunocompromised patients
What are the Bronchiolitis symptoms and etiology?
1 to 4 days of symptoms (eg, nasal congestion, rhinorrhea/runny nose, cough, and low-grade fever) indicative of an URI
• self-limiting and symptoms diminish within 7 to 10 days with resolution within 28 days
• infants frequently are dehydrated
Why are infants freq. dehydrated when they have Bronchiolitis?
due to limited oral intake because of coughing combined with fever, vomiting, and diarrhea
- failure of O2 in H20 & CO2 out
What is the most common cause of pediatric bronchiolitis?
Respiratory syncytial virus (RSV), accounting for up to 75% of all cases
(not adults b/c they already have them)
What are the detectable viruses most common in adult cases of bronchiolitis?
parainfluenza, adenovirus, and influenza
• Bacteria serve as secondary pathogens in a minority of cases
• Adult cases are rare often associated with co-morbidities
What are the Bronchiolitis and LRI Diagnosis Methods?
• Culture based methods are the gold-standard to detect pathogens but many clinical facilities lack viral culturing facilities (v. slow)
- use if you see outbreak
• Enzyme-linked immunosorbent assays (using antibody against antigen that’s related to infectious organism) and fluorescent antibody staining tests of nasopharyngeal secretions has increased the ability to identify viral antigens within several hours
• Not as effective for infant diagnoses (b/c infants are infected by various things)
• Prone to false-negative detection depending on infection stage (depends on how good the antibody is)
• PCR testing is available from most clinical laboratories, but its relevance to the clinical management of bronchiolitis is unclear
- only find what you’re PCRing for
• Radiographic chest X-rays in children with bronchiolitis yields variable findings and not recommended
- v. small and depend’s on health region/accessibility
What is the Bronchiolitis treatment in healthy patients?
it is a self-limiting illness
• Recommend antipyretics, and adequate fluid intake (for infants b/c of dehydration)
What is the Bronchiolitis treatment in hospitalized patients? & those with underlying pulmonary disease, cardiac disease or both in hospital?
• oxygen therapy and intravenous (IV) fluids to treat dehydration
• Determine if an underlying cardiac and pulmonary diseases exacerbate the symptoms (b/c may increase aggressiveness of treatments)
Patients with underlying pulmonary disease, cardiac disease, or both recommend therapy with the antiviral agent RIBAVIRIN
What is Ribavirin?
is an antiviral against a variety of RNA and DNA viruses, including RSV, influenza A, influenza B, parainfluenza, and adenovirus (a therapy used for severely ill children who have RSV)
• it is approved only in aerosolized form against RSV
• ONLY used for severely ill patients!!
a risk b/c can be bigger change at microbial resis (therefore used to prevent resis)
What is Pneumonia caused by?
Is caused by inspiration of ambient air into the lower respiratory tract with contaminated environmental and infectious particulate matter (ex: smoke, vape, etc.)
• Affects lung parenchyma (ends of bronchioles, leading to alveolar sacs that do oxygenation rxns for lungs) function
What is Pneumonia one of the most common causes of?
SEVERE SEPSIS and the leading infectious cause of death in children and adults in North America
• mortality rates as high as 50% depending on the severity of illness
(most severe form of common LRIs)
Does Pneumonia peak?
It is a year-round illness due to different infectious agents
that vary with seasons (*unlike URI)
Who does Pneumonia occur in?
persons of all ages but most severe in the very young, the elderly, and the chronically ill (have co-morbilities)
- get sicker easier so can carry through to other seasons
What are the 3 routes of infection for Pneumonia?
- Direct inhalation of infectious droplets
- Aspiration of oropharyngeal contents (URI)
- Hematogenous(bloodstream) spread from another infection site
What is Pneumonia Pathogenesis?
Respiratory host-defenses comprise innate and adaptive immunity pathways in alveoli (want to prevent it going into bloodstream)
• Disruption of normal lung microflora by antibiotic treatment, ethanol/ narcotics, tumors, co-morbidities can impede host defenses
• Alveolar function is affected in pneumonia (imp.)
What is Pneumonia caused by?
a variety of viral and bacterial pathogens
• The causative organism(s) is highly dependent on how and/or where the pneumonia was contacted
Common infectious agents differ depending on where it was acquired
Common infectious agents differ depending on where it was acquired for pneumonia:
What are they?
- Community-acquired Pneumonia (CAP)
- Hospital-acquired Pneumonia (HAP)
- Ventilator-acquired Pneumonia (VAP)
Community-acquired Pneumonia (CAP)
• occurs outside of the hospital or within 48 hours of hospitalization (to determine how severe & what types you have)
Hospital-acquired Pneumonia (HAP)
• occurs in the hospital after at least 48 hours of hospitalization (typ. more severe b/c normally are bacterial)
Ventilator-acquired Pneumonia (VAP)
• occurs following 48 hours of endotracheal intubation
(most challenging - b/c on ventilator so already don’t have good oxygenation/function)
- could make it worse b/c pushing down
HAP/VAP tend to be…
bacterial & have specific pathogens
The longer the length of hospital stay and/or IV antibiotic usage within 90 days preceding HAP, the more likely a patient will have…
a multi-drug resistant bacterial infection
- complicates treatment (disinfection is v. imp - see more if staff are overworked at hospital)
CAP tends to be…
viral
Pneumonia Symptoms
• high fever, chills, malaise with cough, increased sputum production, dyspnea, chest pain (feel like weight on chest - pushing lungs to do more with less)
- b/c alveoli isn’t working well
Pneumonia Diagnosis
• pulmonary infiltrate with or without abnormal white blood cell (WBC) count or oxygen saturation can clinically diagnose pneumonia
- WBC will help determine how severe (higher WBC means more WB’s to help fight infection)
• recommend a chest X-ray (radiograph) for all adult patients with suspected pneumonia but only in select pediatric patients with severe CAP
• Atypical pneumonias often demonstrate patchy infiltrates on chest X-ray that are more extensive than clinical symptoms suggest→“walking” pneumonia (may be able to go on with day despite)
• Blood cultures and non-invasive sputum cultures are recommended for all adult patients with suspected HAP or VAP
• Confirmation of CAP etiology is only for severe CAP (if CRB-65 than do it)
Bacterial Pneumonia is…
lobular (bact will concentrate in a region (lobular in shape)
(closer to source - trachea perhaps)
Viral Pneumonia
diffuse
- b/c viral infections spread out & infect multiple areas
Children’s penumonia
can resolve with therapy (antibiotic doxycyline - used for adults to)
Why sputum for HAP or VAP?
b/c want to figure out what’s happening in hospital fast & can limit it fast if identified (just by simply changing infectious control process can help limit)
What is the Pneumonia Treatment?
• Eradication of the offending organism through selection of the appropriate antibiotic(s) or antiviral(s) and subsequent complete clinical cure is the primary goal
• Secondary goals include minimization of the unintended consequences of therapy, including toxicities and risk of acquiring secondary infection
• Good antimicrobial stewardship in therapies is key:
• “Pick the right drug for the right bug”
CAP severity assessment of mortality involves a
CURB- 65 (a.k.a CRB-65) scoring system (each yes = +1, no = 0):
• Confusion
• Uremia: blood urea nitrogen (BUN) > 20 mg/dL [7.1 mmol/L] • Respiratory rate: ≥30 breaths/min
• Blood pressure: systolic <90 mm Hg, diastolic ≤60 mm Hg
• age ≥65 years
Why does the CURB-65 use BP & not HR?
b/c its the pressure that builds in bloodstream that cause heart problems (i.e. increase pressure means not enough heart function that can cause cardiac arrest)
Interpretation of CURB-65 scores:
• Scores of <2 get outpatient treatments
• Scores of >2 get hospitalized
• Scores of >3 admit to intensive care unit (ICU)
There are too many empirical antibiotic and antiviral treatments to review for pneumonia so…
depend on causative organism and its antimicrobial resistance
• Rapid identification of a causative organism has better treatment outcomes for the patient
What are Pneumonia antibiotic therapies?
• Antibiotic COMBINATION THERAPIES (ie 2-3 drug combinations) are being used due to growing rates of multi-drug resistance in bacteria (have to hit them hard to get rid)
• Unclear how effective these combinations are
• Older antibiotics considered as LAST-RESORT DRUGS due to their toxic side-effects are increasingly being used
• e.g. polymyxins and aminoglycosides
Pneumonia antiviral therapies
• Few in use, some treatments are monoclonal antibody mediated, many rely on vaccine prevention (v. expensive to produce)
• ACYCLOVIR used to treat varicella and herpes simplex related pneumonia
Which infectious agents are frequent cases of acute bronchitis (AB)?
- Influenza A
- Respiratory syncytial virus (RSV)
- Parainfluenza virus
