Asthma And Airway Obstruction

There are three mechanisms of airway obstruction in Asthma. These mechanisms can occur with varying intensity, but commonly they equire three simple inhaler medications that alleviate the symptoms. Sometimes the symptoms can be so severe  that they can lead to acute care and emergency rescue interventions.

To visualize the mechanism of air way obstruction, imagine looking through a tube that is somewhat pliable, perhaps like a garden hose, except a short one, where you can see out to the other side.

When an asthma attack occurs, one of the first reactions is broncho constriction - the airway contracts. This usually happens suddenly. And so imagine the garden hose contracting, and imagine the visible world on the other end of the hose narrowing. Think of that reduced visual field as representing less oxygen getting into the lungs. Right away, we can imagine the discomfort of the asthmatic patient. But there are more mechanisms.

The second reactions is Swelling

The the interior lumen of of the airway swells - so imagine the hose as thicker on the inside- now we have a narrower hose from constriction. And we have obstruction occuring within the hose from swelling, both narrowing the the visual field in the hose as we look out to the other end. ( The same thing occurs in the bronchi during an asthma attack - air flow is reduced further, from the action of two obstructive mechanisms.

This swelling occurs because, in reaction to some stimulus that may be localized in the upper airway, the offended area is now being bombarded by white cells called mast cells (eosinophils and basophils, )These cells release Histamine..Histamine causes the affected tissue to swell.Histamine, when it is released is the primary cause of all "swelling."

(Note: In most cases the release of histamine is a protective measure designed to keep the irritation or trauma localized. An example of useful swelling might be when a break or sprain occurs in a bone, the area around swells, and this serves the purpose of immobilizing the area, and sealing it off, so that the area is not subject to infection. The same thing happens with local infection, or tissue trauma. And the purpose of the swelling is the same - functional.But when we have contraction of an airway, and interior swelling, we have a significant decrease in air exchange outward, and inward. The visual field in our garden hose analogy is that much less.Because the triggers are somewhat innocuous such as in the case of pollens or irritants, the swelling reaction in asthma is dysfunctional. It is an over reaction to the threat, when compared to the useful swelling in tissue from a broken bone.)

But there is a third insult added to this injury resulting in more narrowing. Mucous production. The production of mucous is is a defense designed to trap bacteria and infective agents. Mucous works to do this because it is very viscous. But most triggers of asthmatic reactions in asthmatic patients do not involve infective agents or extremely noxious agents. And so, there's another hyper reaction that narrows our visual field through the garden hose almost completely. When we can't see through the hose to the other side, that symbolizes the reduction of air flow in the patient with asthma, decreasing amounts of oxygen are getting to the lungs secondary to three hyper reactions and three mechanism of obstruction. .

So, what is the first line of defense during an asthma episode? The answer is: The bronchodilator, taken usually from an inhaler with a few puffs.

Albuterol is the most common bronchodilator provided in inhaler form. Two puffs of albuterol by way of inhaler produces an instant but short term result - in most cases the air way pops open that quick: BOOM!

The visual field in our garden hose increases. (So does oxygenation, and relief is usually immediate.)

Severe constriction may require IV theophiline type meds or other potent broncho dialating drugs such as Solumedrol. These are used if Albuterol based inhalers do not dialate the airway enough or for long enough and the patient is in severe distress.

The next treatment is the cough.

Once the airway is dialated the patient should cough. The cough frees the area of mucous, and this widens the airway more. Continuing with our our garden hose analogy, we can now see to the other side better because the airway is now dialated and free of debris. But the remaining problem is swelling.

Swelling is usually treated with a steroid inhaler. These inhalers contain natural or synthetic corticosteroids (such as those produced by the adrenal medulla) .

Corticosteroids reduce inflammation and swelling.

The steroid is the last treatment after the cough, which rids the area of mucous. Clearing the air way with the cough, laying down a layer of steroid on clean bronchial tissue, free of mucous, reduces the swelling faster because the medication is applied directly to the tissue in the air way. Using the steroid before the bronco diating medication is not as effective and contraindicated.

The medical names of the commonly used steroids are these: Beclomethasone, Budesonide, Ciclesonide, Flunisolide, Fluticasone and Triamcinolone

But the the mast cell inhibitors are contained in some other inhalers. These drugs act as preventives, and they may be used also in acute situations with the other drugs as an adjunct to steroids. They inhibit mast cells from de granulating to produce histamine. As stated Histamine is the natural chemical that produces swelling. They are not as effective as the common steroid in reducing inflammation but they may reduce over use of corticosteroids which can have side effects, And they may potentiate the effects of steroid therapy and broncho dialator therapy - resulting in less steroid use.

The common mast cell inhibitor drugs are Cromolyn or Nedocromil.

Many people with asthma have all three types of inhalers for mild to moderate asthma. The process of broncho dilation, cough and use of anti-inflammatory medications is called asthma rescue, and the sequence of treatment is a called “sandwiching.” (sandwiching refers to the order of treatment described above. That order maximizes treatment.

More acute asthma reactions that are unresponsive to inhalers are treated with MDI inhalers. This treatment usually involves inhaling mist or aeresol produced from a machine with medication added, broncho dialators, which may be of the more potent types like solumedrol. The treatment may last 20” or so. The patient usually sits holding a tube with aerosol of medication piping out of the tube, inhaling the mist until the medication is gone. This treatment is usually fairly effective in terms of opening up the airway. There is sometimes cough, and application of steroid, or mast cell inhibitor drug that follows – to reduce swelling. In some cases IV Solumedrol, chest physical therapy and oxygen are required, as some asthma reactions are life threatening, requiring acute care.

Asthma Triggers

There are Allergens that can cause asthma reactions such as: Allergies to foods, dust, pollens, pet hair, chemical vapors..and others.

Non Allergens can be other causes: Irritants can trigger asthma, such as cigarette smoke, pollutants, strong emotional reactions. Infections, hormonal changes, gastric reflux (acid refluxing into the higher esophagus with vapors triggering asthma,) exercise, and temperature changes.

There are work related asthmas as well, that are caused by exposure to allergens and irritants But chronic exposure to irritants in work environs can lead to acquired allergy.

For example, many industries can expose workers to chemicals in the air, and in the work environment. Chronic exposure to chemicals that are irritating can trigger a severe asthmatic reaction in someone who is essentially non asthmatic, because the worker is becoming sensitized to that irritant as is “acquiring” an immune response to that irritant.

. To illustrate this I will give you two personal examples.

When I was a kid I worked as an electro plater. I worked over a tank that was filled with chemicals that applied metal to circuit boards through the electrolysis. I noticed there were many vapors that filled my work area from other processes in the building as well, including ammonia vapors from cleaning the finished circuit boards.

I noticed over time I would get very wheezy by the end of the week. And by the end of the summer that I worked in this place, I could not walk 3 feet on the following Saturday, my first day off, without stopping for air. Through the summer the wheeziness would go away on weekends and come back by mid week. But I was paralyzed by the end of the summer. When I made the connection I went to my doc, who said you have to quit that job. I did, and the symptoms went away. liked the job and it paid well, and I was doing very well – and it made me sad to leave.

Later in my life, when I got my nursing degree, I first worked in nursing homes to gain experience as a new grad. At my first nursing home job, toward the end of my stay there, my eyes would get very red and itchy. This did not happen until near the end of my two years employment. I thought that was very strange But over the last 6 months I also started to get very wheezy, and had to get an inhaler. I left that nursing home and the symptoms disappeared. I went to another, and the same thing happened. At my last job I worked in a medical respite, and occasionally my eyes would get red and itchy.

In the first two instances I never sorted the cause. When I was at my first job I thought it was the inhalation of aerosol deodorizers that were set to a timer in the hallways that fired off periodically that were causing the reaction. But those weren't t present at the next job or my last one.

I would only occasionally react in my new job. One thing was different: the patient population, at the first two jobs the patients were elderly, at my last job the patients were young to middle age. The homeless population.

Finally I over heard a nurse say that another nurse was allergic to Metamucil, a fiber given to bulk up stools. It stimulates the bowl and acts as a laxative. The active ingredient in Metamucil was a plant fiber - psyllium.

I decided to test whether I was allergic too as somethng clicked when I heard that. And so, took a pinch of Metamucil dust and sniffed it. The reaction was immediate, my eyes started itching, and my right eye blew up with swelling, it went sealed shut from the swelling.

Because my use of metamucil with this population was infrequent, The itchiness was infrequent. It is the elderly, with slower GI motility, that require so much of this stuff as they are some times on constipating medication complicating naturally slower Gi transit. (the elderly are at high risk for bowel obstruction for this reason) They can get psyllium as much as three times a day. And each time it is millions of tiny fibers poured in a 30 ml cup and they can invisibly fill the air and settle into the environment.

I realized that over a few years I'd acquired an allergy to Psyllium and so – where no allergy existed before to that dust, my immune system became sensitized to chronic exposure to that irritant.

Working in nursing homes for me then became contraindicated. That particular fiber, is very hard to remove from the environment In nursing homes and - it is everywhere - especially ubiquitous in nursing homes with rugs. Even regular vacuuming does not remove it all. The fibers in the Psyllium bind to the rug fibers and get kicked into the air when people walk on the rugs. There are alternatives to Metamucil which could be used as I expect more and more nurses will be developing this problem, especially those who work in nursing homes..

So in conclusion, even the non asthmatic can know what the asthmatic feels from the resulting obstruction of the airway caused by this fairly common condition called Asthma.

Certainly an asthmatic should be aware of the triggers in the work environment and make an effort to identify them to minimize exposure. This can often be hard to do...however, discussing this condition with your medical practitioner and developing strategies can help. Learn to recognize the symptoms of asthma as they begin, be alert to triggers in the environment and remove yourself from that trigger. Then apply the sandwiching technique early before more obstruction evolves.

As for nurses, if you are having these problems (symptoms like the ones I described,) and I believe more and more nurses are developing acquired allergy to Psyllium - consult with your administrator or nursing supervisors for alternatives to psyllium based bulk laxities Citrucel works just as well, and does not contain Psyllium The company may replace metamucil globally, and eventually the Psyllium may work itself out of the environment. In the interim, if you have these symptoms and cannot effect change soon, have another nurse pour the laxative.

Gary Stone BSN, MLT (ASCP)