Resp Flashcards
(71 cards)
What is asthma?
asthma is a disease of airflow obstruction due to airway inflammation that varies over time
asthma is characterized by pathophysiology of bronchoconstriction, mucus plugging, airway inflammation and edema hyper-responsiveness to various stimuli
Samter’s triad
asthma + nasal polyps + sensitivity / intolerance to NSAID / aspirin
Asthma pathophysiology
eosinophilic inflammation causing narrowing of airway as an immune response to allergen
1) allergen taken up by antigen presenting cell (dendritic cell or macrophage)
2) antigen presenting cell activate CD4 Th2 T cell, which secrete IL-4 and activate B cell to produce IgE antibodies
3) IgE antibodies attach to Fc receptors on mast cells, arming mast cells
4) on subsequent exposure, allergen bind to IgE on mast cells, causing mast cell degranulation
5) mast cell degranulation release inflammatory cytokines causing inflammation resulting in early phase asthmatic response (early asthma attack) inflammatory cytokines include histamine, IL-4, IL-5, leukotriene, serotonin, prostaglandin, eotaxin inflammatory cytokines increase vascular permeability, vascular inflammation, bronchospasm, airway hyperresponsiveness
6) inflammatory cytokines recruit leukocytes (including eosinophils) into airway tissue, resulting in inflammation resulting in late phase asthmatic response (late asthma attack) leukocytes cause increased vascular permeability leading to edema, smooth muscle contraction leading to bronchoconstriction, activation of goblet cells leading to increased mucus secretion
7) chronic inflammation cause remodelling of airway resulting in chronic asthma post asthmatic attacks eosinophils and lymphocytes release factors inducing permanent remodelling of airway, resulting in permanent narrowing of airway, such that airway function cannot return to normal level completely in chronic asthma even when treated with bronchodilator
What is status asthmaticus
severe asthma attacks that are poorly responsive to bronchodilators
What is the asthma control criteria
Good asthma control if all conditions are met
Poor if one isn’t met
Daytime symptoms - <4 days per week
Need for a fast acting beta 2 agonist - <4 doses per week
Nighttime symptoms - <1 night per week
Physical activity - normal
Exacerbations - mild, infrequent
Absence from work or school due to asthma - never
FEV1 or PEF - 90% + of personal best
PEF diurnal variation - <10-15%
Sputum eosinophils - <2-3%
PFT results seen in asthma
scooped flow volume curve low FEV1 (<80% predicted)
significant improvement in FEV1 with bronchodilator (improvement in FEV >12% provided improvement >200mL)
low FEV1/FVC ratio (<0.7 in adults, <0.8 in children)
disproportionately low FEF25-75 and FEF75
decreased peak flow
DLCO normal
increased airway resistance
What is the methacholine challenge
in asthma, with airway challenge with methacholine, usually significant (>20%) drop in FEV1 with small amount of methacholine (<8mg/mL)
PC20 = concentration of methacoline at which FEV decrease by 20%
PC20 <8mg/mL suggest asthma
What is airway challenge with exercise diagnosis
in asthma, with airway challenge with exercise, usually significant (>10%) drop in FEV1 by 80% maximum heart rate
Diagnosis of asthma
asthma diagnosed based on all of the following
- clinical history of asthma symptoms and asthma attacks
- PFT showing reversible obstructive lung disease:
scooped flow volume curve
low FEV1 (<80% predicted)
significant improvement in FEV1 with bronchodilator (improvement in FEV >12% provided improvement >200mL)
low FEV1/FVC ratio (<0.7 in adults, <0.8 in children)
What is a parameter that can be used to monitor asthma at home
peak flow
Asthma pharmacological management
all patients start with fast acting bronchodilator (SABA) PRN and add ICS if require maintenance therapy with ICS
if asthma is not controlled (see asthma control criteria), add in the following order:
increase ICS dosage
add long acting beta-adrenoreceptor agonist (LABA) note that long term use of LABA increase risk of severe asthma attacks
ICS LABA combinations include budesonide/formeterol, fluticasone/salmeterol, mometasone/formoterol
ICS LABA combinations can also replace SABA as emergency puffer but is 2nd line to them
leukotriene receptor antagonist (LTRA) (Montelukast sold as Singulair)
Theophylline
oral prednisone
if patient ever had an asthma attack, automatically add ICS and LABA upon discharge
if SABA is used more frequent than Q4H, then send to emergency
SABA should be used sparingly, because frequent use of bronchodilator results in tolerance and increases frequency of asthma attacks
all medications are safe to use during pregnancy
Management of acute asthma exacerbation
- Assess for current state and complications
- SABA and short acting anti-cholinergic (SAAC) to relieve dyspnea
if symptoms still uncontrolled, can use IV SABA in ICU
setting systemic oral or IV corticosteroid to reduce inflammation, which aborts exacerbation, prevent relapse, speeds recovery and decrease need for hospitalization
proper hydration
if hypoxemia, then oxygen therapy
if respiratory failure, mechanical ventilation
- Treat underlying cause (ex. infection, beta blocker…), treat cormobidities
Why is ICS not used during asthma attack
ICS is slow acting and may not be breathed in during respiratory distress, so not used during asthma attack
Metered dose inhaler (MDI) procedure
1) shake inhaler
2) take off cap
3) sit up straight or stand with chin lifted up
4) exhale completely
5) seal with lips on the inhaler tightly and start inhaling slowly
6) depress top of inhaler once
7) hold breath for >10 seconds
8) wait 45-60 seconds between puffs
9) rinse mouth
Dry powder inhaler (DPI) procedure
1) hold disk level with one hand
2) push notch away from user as far as possible with other hand, such that the mouth piece appears
3) push lever away from user as far as possible with other hand until it clicks
4) lock lips onto the mouth piece
5) breath deeply with mouth
6) hold breath for >10 seconds
7) slide notch and lever back to original position, such that disk is ready for another dose
Common ICS
Budesonide (Pulmicort)
Fluticasone (Flovent)
What is the only asthma medication shown to decrease mortality
ICS
ICS MOA
late onset with greatest effect within 3 months
inhibit production of cytokine resulting in anti-inflammatory effects (reduce eosinophil infiltration, inhibit macrophage function and reduce production of leukotrienes)
ICS adverse effects
ICS is inhaled, so its effect is localized to lung and do not have any systemic adverse effects
thrush oral candidiasis, which can be reduced by using inhaler with spacer and followed by mouth rinse
dysphonia (impaired ability to produce voice)
osteoporosis (only for high dose steroid in high risk patient population who need to be monitored regularly with bone mineral density scan)
decreased growth velocity in short term for children, but no change in adult height
adrenal suppression
worsening of glaucoma (only in high risk patient with glaucoma who need to be monitored regularly in terms of intra-ocular pressure)
increased risk of cataract, which is rare and does not require routine surveillance
skin thinning
Long acting beta 2 agonist LABA examples
Salmeterol (Serevent), green diskus DPI
Formeterol (Oxeze), green turbuhaler MDI
LABA MOA
same mechanism as SABA, but with longer lasting effect
1) beta agonist binds beta adrenergic receptor, which activate intracellular adenyl cyclase to convert ATP to cAMP
2) increased cAMP relaxes bronchial smooth muscle, resulting in bronchilation
LABA adverse effects
similar to SABA
sympathetic effects: tachycardia, tremor, headache, agitation, irritability
metabolic: hypokalemia, hyperglycemia
prolonged QT, which can lead to arrythmia
Commonly used combined ICS/LABA
Fluticasone/Salmeterol (Advair), MDI or diskus DPI
Budesonide / Formoterol (Symbicort), turbuhaler MDI
Indication for LTRA use
used as controller (i.e. taken regularly no matter if symptoms appear) and 2nd or 3rd line therapy
usually added to ICS for uncontrolled symptoms
can substitute LABA with LTRA, but usually added to ICS and LABA
preferred treatment and more effective for asthmatic patient with more allergic profile of eczema, nasal polyps, rhinitis, aspirin allergy
