Asthma Flashcards
How many people does it affect in the UK (approx) include detail of increased stats for incidences in children and why?
Affects 5 million people approx
1 in 4 children currently affected compared to 1 in 18 in 1970. Twice as many boys than girls.
Due to diet,lifestyle, environmental factors.
Define asthma and it’s main characteristics.
A chronic reactive airway disorder
Airway limitation
Airway hyper-responsiveness
Inflammation of bronchi with eosinophils (type of white blood cells), T lymphocytes (type of white blood cell) and mast cells (part of immune system,in connective tissue) - with associated plasma exudate, oedema, smooth muscle hypertrophy, mucus plugging and epithelial damage.
What happens in an asthma attack?
Episodic acute airway obstruction resulting from bronchospasm, increased mucus secretion and mucosal oedema.
Severity of attacks vary.
ICU treatment needed in complete airway obstruction or extreme fatigue.
Name the two classifications of asthma:
Intrinsic or Cryptogenic- when no causative agent can be identified
Extrinsic- implying a definite external cause
List some causes and triggers for asthma:
Note: there are over 200 found in the workplace known to give rise to occupational asthma!!….woah!!
Environmental exposure- faecal particles of house-dust mite, pets, pollen.
Occupational sensitisers- spray paint, soldering, allergens from animals and insects
Atmosphere pollution- sulphur dioxide, ozone, diesel exhaust, particulates,
Drugs- NSAIDS, Beta adrenoceptor agents (beta blockers)
Viral infections- Rhinovirus, parainfluenza virus
Cold air
Emotion
Irritant dusts/vapour and fumes- perfume, fags
What % of asthma admissions need mechanical vent?
2%
List some very exciting facts about asthma..with references please
Continues to rise globally (Phipps & Garrard 2003)
Often affects young people
By age of 10-30 (??second decade of life) asthma affects 10-15% of population (Kumar & Clark 2001)
2% of acute severe asthma admissions need ventilating
What is gas trapping?
When the patient cannot fully exhale before needing to take the next breath in, leading to an accumulation.
What is endobronchial mucus suffocation?
Extensive mucus plugging of bronchi (necroscopic studies)
How does asthma make you short of breath?
Bronchconstriction
Airway oedema
Mucus plugging
Describe the Pathophysiology of an asthma attack:
Immunoglobulin IgE antibodies attached to histamine containing mast cells and Receptors on cell membranes initiate intrinsic attack
When exposed to antigen (eg pollen) IgE antibody combines with antigen
On further exposure to antigen mast cells degranulate and release mediators
Mast cells in lungs are stimulated to release histamine and reacting substance of anaphylaxis.
Histamine and leukotrienes attach to bronchi - causing swelling.
Mucous membranes become inflamed (wheeze, ^RR)
Histamine stimulates mucous membranes to secrete more - further narrowing bronchi (coughing)
Inhalation- narrow bronchi expand slightly, air reaches alveoli.
Exhalation - increased intrathoracic pressure closes bronchi leading to air trapping.
Obstructed airway impede gas exchange - hypoxia
List some management options for asthma?
Oxygen therapy - humidified high flow, cpap, NIV, mechanical ventilation,
PaC02 monitoring for detection of fatigue or response to treatment
K monitoring, hypokaleamia common due to fluid resus and beta agonist bronchodilators
Give fluid to avoid hypovalaemia
Nebulise - Beta agonist (salbutamol), adrenaline, ipratropium bromide
Give corticosteroids
Give magnesium (not much evidence)
Give aminophyline
CXR (?collapse,pneumonia,flat diaphragm,hyperinflation)
Replace electrolytes (to avoid muscle weakness, arrhythmias)
Upright patient positioning to optimise lung expansion
Based on PEF when should an asthmatic be intubated?
Peak expiratory flow more than 75% of best or predicted - mild
PEF 33 - 75 % - moderate to severe
PEF less than 33 % of best or predicted - life threatening
What, ideally, the ventilator settings in an asthmatic?
Peak pressure less than 30cm/h20
1:2 I:E
Low rate 8-10
Minimal PEEP
TV 6-8 mls/kg
pH above 7.2
Eg- pressure controlled modes, SIMV.
How can we minimise gas trapping?
Controlled hypoventilation (lower TV=less gas to exhale) Reduce RR (longer expiratory time) Reduce need for night minute volumes by decreasing C02 production (sedation/paralysis,controlling fever/pain)
