Asthma Flashcards
Describe asthma
A chronic inflammatory disease associated with a variable degree of airway hyper responsiveness to endogenous and exogenous stimuli
Symptoms of asthma
Wheezing, coughing, sputum production, chest tightness, shortness of breath, dyspnea
Prevalence in New Zealand
One in six Nz adults and 1 in 4 children
dyspnoea
Difficult of laboured breathing
Diagnosis of asthma
Physical exam- wheezing high pitched whistling (non-specific)
Hx of cough, recurrent wheeze, dyspnoea, chest tightness, reversible airflow limitation and diurnal variation.
Lung function test- evidence of variable air flow obstruction.
Lab studies and asthma
Not routinely indicated but may be used to exclude other pathologies.
Test include assays for eosinophilia and immunoglobulin E
Excesses in each may be supportive of asthma but low specificity.
Imaging studies
Most patients chest radiography findings are normal or indicate hyperinflation. Findings may help rule out other diseases.
Pulmonary function testing. Describe pros and cons of PEF
Peak Expiratory Flow.
Cheap and easy
Good for monitoring progress
Not good for diagnosis as too much variation between patients
Spirometry
Measures FVC- the maximal amount of air that can be expired from the point of maximal inhalation; and the FEV1- the volume of air forcefully expired in 1 second. FVC/FEV1 ratio generated and plotted against predicted values.
What is a reduction in FVC/FEV1 ratio suggestive of
A reduction in FVC/FEV1 ratio suggests the presence of an obstructive pulmonary disease.
What is decreased FVC suggestive of
A restrictive pulmonary disease
Name three techniques of measuring static lung volumes
Helium dilution, plethysmography, N2 washout
Plethysmography
?
Describe helium dilution
The subject is connected to a container with a known volume of helium in it. Through breathing in and out the subject is able to equilibriate the concentration of helium in the lungs with that in the container.
Two categories of asthma treatment
Relievers (bronchodilators) and preventers (Anti inflammatory agents and mast cell stabilisers)
What are the two categories of inhaled beta adrenergic agonists
SABAS and LABA
Short acting beta agonists and long acting beta agonists
Indication/ use of SABAs
Acute bronchospasm
Prevention of exercise induced asthma
Not recommended for regular use
Rapid onset of action
Three types of SABA
Adrenaline, isoprenaline, fast acting beta 2 agonists salbutamol and terbutaline.
Describe adrenaline treatment
SABA, Beta 2 receptors respond to circulating adrenaline which stimulates cAMP and results in smooth muscle relaxation. Activate both alpha and beta receptors so also caused vasoconstriction.
Describe isoprenaline treatment
SABA. Beta 1 and 2 agonist. Increases HR and relaxes smooth muscle.
Describe advantage of fast acting beta 2 agonists salbutamol and terbutaline
Resistant to break down by COMT so effect last 4-5 hours.
Benefit of drug administration through inhalers
Fewer side effects as more drug to lungs and less systemic
Problems with inhalers
Tachyphylaxis (resistance)
Mucous plugging, where mucous plugs stop the full amount of medication from reaching the distal lung sites.
Describe long acting B agonists
Act for 12 hour or more as stay in the cell membrane so bind to B2 receptors for longer.
Used for maintenance and control
Used for moderate-persistant, severve persistant asthma.
Adverse effect os SABAs and LABAs
Due to activation of beta 2 receptors in other non target tissues. Effects include cardiac stimulation, tremor, hypokalemia (potassium deficiency).
Describe inhaled cholinergic agent. 2 drug names
Inhaled bronchodilator. M1-M5 agonists. The M3 receptor causes smooth muscles to contract and mucous glands to secrete.
Includes atropine and tiotropium. Atropine causes smooth muscle dilatation for 6-8 hours. Tiotropium acts over 24 hours used as COPD treatment.
Describe asthma anti-infammatory drugs
Glucocorticoids. A class of steroid hormone that bind to GCR. This causes up regulation of anti-inflammatory proteins (transactivation), and repression of anti inflammatory proteins in the cytosol (transrepression). Considered the most effective class of medication for acute and long term control of asthma.
Name some anti inflammatory asthma drugs
Systemic: Cortisone, prednisone, hydrocortisone, dexamethasone.
Inhaled: Flixotide
Pulmicort
Adverse effects of GCs
Hypercortisolism Diabetes Osteoporosis Increased BP Psychosis Hoarseness, cough, oral candidiasis
