Asthma is a condition , increasing in recent times , in which the small airways of the lung go into reversible spasms.The airways to the lung are called bronchii which split into smaller bronchioles and then open up to very thin walled grape like sacs called alveoli , from where oxygen diffuses into the capillaries nearby and is taken by red blood cells to all the parts of the body.
If the hyper sensitivity is severe the whole airway may be cut off and the person may suffer extreme distress . In asthmatics the maximal rate at which the air can be expelled - PEAK FLOW is reduced . In lung function tests the forced amount of air expelled in one second called FEV1 is reduced markedly during attacks but can return to near normal ( above 80% of predicted) at other times ie it it is REVERSIBLE whereas in COPD it is not .
The triggers or chemicals which cause the smooth muscle lining the airways to do this may be varied such as house dust mite ,pollen , cig smoke , cold weather , emotion, infections . work chemicals (do peak flows at work) and patients may report they are better on days off or on holiday etc. or unknown. These allergens bind to receptors on mast cells and set off a cascade which involves release of histamines , leukotrine and other inflammatory chemicals which seem to work via tumor necrosing factor to cause the smooth muscles to contract.This makes it more difficult to expel air from the lungs (as that is due to just passive recoil usually) and so the patient can be heard to wheeze on breathing out.
Main symptoms are cough esp at night esp younger children , wheezing , breathlessness on exercise in older children , very sticky sputum.
Diagnosis is by demonstrating a reduced peak flow to less than -mild 70% of predicted , moderate less than 60 and severe if less than 60% . Spirometer shows a reduced fev1 - 80% is normal , 60-80% is moderate severity and more than 60% fall of fev1 is severe asthma . When the patient is stable two readings are done , the second after taking two puffs of a blue inhaler and an improvementof 15% or more than 400ml in FEV1 is diagnostic of asthma.
People can die if oxygen saturations fall below 92% . A silent chest which means failing effort and is a grave danger sign.
Avoiding allergens like house dust mite , pollen is difficult . One can try killing the mites by putting the pillow in a deep freezer for one hour a week.
Treatment is aimed at stimulating the beta receptors which produces cyclic amp which causes the smooth muscle cells to relax . Short term beta agonists like salbutamol (ventolin) or terbutaline act for 4 hrs .Long term beta agonists like salmetrol and formetrol -9hrs are more fat soluble and sit on the receptors longer and give more lasting relief . These beta agonists act against the more severe early phase of allergen response
Steroid like beclometasone or fluticasone carried in inhalers attach to the steroid receptors on the cell membrane and are carried to the nucleus where they induce genes to make an enzyme called cyclic AMP . cAMP relaxes the muscle cell . They also induce the production of more beta agonist receptors .It takes many days for the genes to be activated and so there is a delayed action of about a week or so before the steroids take effect . However long term use helps in remodelling the airways and making them less hyperactive and the muscle layer less thick and they are the most important therapeutic agents in asthma.
Long acting beta agonists also induce the production of more steroid receptors and so add to the steroid effect.
Oral steroids, theophylline have also been used . Leukotrine antagonists like singulair act against the less severe late phase and are useful in children.
Antihistamines and nasal steroid sprays are useful in children who may suffer from allergic rhinitis or nasal polyps. Cromoglycate stabilises mast cell membranes and were much used at one time.
The aim of treatment is total control so that exercise tolerance is good , salbutamol (blue) inhaler use is at a minimum , 2 puffs a day or less , there is no night time waking and the peak flow is more than 80% of predicted . Asthmatics are encouraged to have a self management plan and to go along the steps below , each step should be about 12 weeks long. Step down at stable periods and step up esp steroid use when it is worsening ie peak flow going down .
In children spacers are used and for infants a mask may be attached to the spacer . An autohaler is actuated by the patients breath. Also available are dry powder inhalers where the device is primed and then the puffer pressed to release it . These actuated inhalers like Easibreathe , accuhaler , turbohaler , twisthaler , diskhaler , clickhaler , aerohaler , pulvinal etc. need the breath to be held for 10 seconds and a wait of 1min before another breath
A spacer is useful for children and in emergencies where it is better than nebuliser.Inhaler efficacy can be improved by spacer devices, which hold the medicine in a chamber for long enough so that patients can inhale slowly and deeply once or twice. Spacers can successfully decrease the oral deposition of medicine from 80 percent to just 8 percent. Commonly used spacer devices include aerochamber , nebuhaler etc. Upto 20 puffs can be given with 5 breaths between each actuation. After 3m if good control reduce medication eg steroids by 25%
In hospital if patient is having a severe attack ie cant speak , oxygen saturation less than 92% , pO2 less than 8 , resp rate more than 25 or heart rate more than 110 , can use oxygen , artificial ventilation , sc adrenaline , iv hydrocortisone , iv ipatropium , iv beta agonists , iv theophylline , iv magnesium ,oxygen at 6l/min
In future anti IgE monoclonal antibodies omalimuzamab , hookworm therapy seem promising. Hookworms dampen inflammation.
Other therapies to consider including nasal steroids and h1 antagonists like cetrizine and desloratidine for allergic rhinits . Often a trial period of the sprays can help as can oral steroids or surgery for nasal polyps.
28% get total control with just steroids , 44% with Laba plus low dose steroids 80% reduction in exacerbations
Self management plans teach patients to resume inhaled steroids if saba effects lasts less than 4hrs ,peak flow falls below 80% , to start oral steroids -which take 6hrs to start working and hence should be started early -if below 60 and to seek emergency help if below 40
Antihistamines reduce chest infections and asthma in children
Antibiotics for chronic sinusitis , surgery for nasal polyps
Aspirin and nsaids may cause asthma within hours in susceptible individuals by promoting leukotrines
Pregnancy continue steroids , laba , do not add leukotrine if not already on it , oral steroids prn
In elderly be careful of pulmonary emoboli , tumors
under 2's try steroid test
keep steroids below 400 per day in children , above 800 can get oral thrush , dysphonia , growth suppression.Most , apart from smokers , will go into long remission in adult life.
headaches and tremor with saba
spirometer needed to check for copd
cut steroid dose every 3m by 25% , keep check on peak flow ,
12 weeks for each step and then check and go on to the next step
28% get total control with just steroids , 44% with Laba plus low dose steroids
80% reduction in exacerbations
If night waking for two days or peak flow less than 85% step up for 7-10 days In copd need higher steroid doses .
Laba plus steroids give 28 extra symptom free days and 47% less exacerbations . Patient compliance is better with combined inhalers..
Advise to suck as hard as they can , lactose is the carrier , seretide accuhaler is easier.Symbicort and Spiriva have higher resistance
Seretide inhaler has less resistance and is easier to use than symbicort or spiriva handihaler
Total control is when there is minimal use of saba , no night awakenings , exercise function is good , peak flow >80% predicted and 75% get to it with seretide fluticasone plus salmetrol)
The dose response for steroids is very steep , so beyond a certain limit increasing the steroid dose does not help as the receptors are saturated .
Asthma is diagnosed when a low peak flow is increased after short acting beta agonist - saba- like ventolin is adminstred . The aim should be to keep it over 80% of predicted vaule for the patient . The patient is asked questions about waking at night with wheezing , playing sports or gym , walking to the shops , socialising , playing with children , going to work and sex life.
The British guidelines are in steps and go down one step if stable every 12 weeks
Step 1 - Here the patient needs a short acting bronchodilator-saba- inhaler -ventolin , salbutamol only once a day or less .May need to be taught how to use an inhaler properly.
Step 2 -If he needs the above more than once a day then usually an inhaled steroid is added . Beclomethasone 200-400 mcgm twice a day via an inhaler or spacer or fluticasone 100-200 mcgm twice a day. Children get half the dose.
Step 3 - If not controlled long acting bronchodilator -laba- salmetrol inhaler 50-200 mcgm or fometrol is added for adults or children . A two month trial is advisable .
Step 4 If there is no improvement at all the laba is withdrawn . Increase the inhaled steroid in twice daily doses upto a maximum of beclomethasone 2gm a day or fluticasone 1gm a day via a large volume spacer if needed. . If laba is kept on a combination laba-steroid like Seretide is very useful
Step 5 - A bronchodilator tablet called leukotrine receptor antagoinists like Singulair 5 or 10mg daily is becoming popular .
Step 6- If still not controlled Prednisolone soluble tablets 40mg a day or less in single does are given for a week or so . Also treat any infection that may have set off the acute attack. Patients should keep some Prednisolone tablets at home for emergency use .Taking steroid tablets for longer than a week can cause skin wasting and other unpleasant side effects . Steroid tablets used longer than 10 days should be tailed off slowly.
Step 7 may need an acute hospital admission .
Some patients may benefit from trials with anti allergic medications like sodium cromoglycates , nedocromil , ipratropium (atrovent) -mainly elderly , theophyllines.
Some chronic asthmatics may develop allergic aspergillosis and a very high eosinophil count and may benefit from a 4 month trial of itraconazole Putting the pillow in deep freezer for one hour a week is also said to kill the house dust mites and may prevent attacks.
An elderly new 'asthmatic' may need a chest xray to exclude lung tumor .
Once the patient becomes well controlled the aim is to take him stepwise down every three months ie from a higher to a lower dose of inhaled steroid keeping in mind the aims - good excercise tolerance and no night symptoms . Children on inhaled steroid may need regular height checks. Fluticasone has less effect on growth rate.
Children can benefit from from a volumatic spacer or the smaller aerochamber . Ventolin syrup can help at night .Older children can use a pressurised meter dose inhaler like ventolin evohaler . Breath actuated ones are available and may be more effective in emergencies . Some prefer dry powder ones like accuhaler or diskhaler. Turbohalers are dry powder reservoirs