Asthma

Lecture Notes

Reference Reading: Chapter 13

I. Reactive Airways Disease (RAD) vs. Asthma

a. In recent years the term “Reactive Airways Disease” has been used especially in the pediatric setting.

b. RAD is a general diagnosis that MDs use if they are unable to diagnose asthma.

c. It is very vague is used for symptoms that including :

üHx of cough

üSputum production

üWheeze or dyspnea

üIn possession of a inhaler

d. The Main difference is that a physician that has diagnosed a patient with RAD, has not, will not or can not obtain tests to diagnose asthma

e. “Reactive Airways Disease”: A lazy term of Uncertain Meaning That Should Be Abandoned

II. When a person has an asthma attack, there are several mechanisms physiologically that occur:

üSmooth muscle constriction

üExcessive production of bronchial secretions

üHyperinflation of alveoli

üMucus plugging

III. Etiology – Asthma is one of the first recognized diseases dating back to the time of Hippocrates. There is more than 5% of population in industrialized countries affected by the disease, but many go undiagnosed and untreated. In the US, approximately 15 million people suffer from some sort of asthma attack.

a. Asthma is the most common childhood chronic illness. Among younger children mails are more prevalent that girls.

b. After puberty it is more prevalent in females.

c. There are two categories for asthma and it relates to its precipitating factors

üExtrinsic Asthma – asthma caused by exposure to the environment

üIntrinsic Asthma – asthma that occurs without a immunologic response

IV. Extrinsic Asthma – Asthma that results from an immunologic (allergic) response.

a. Also called allergic of atopic asthma

b. Atopy - hypersensitivity condition associated with antigen-antibody response.

c. Understand immunologic mechanism

d. There can be two phases when a patient has a extrinsic asthma attack

üEarly response – happens within minutes of exposure; can resolve within an hour

üLate response - several hours after exposure, last much longer; may or may not occur with an early response

üBiphasic response – an early asthma attack that is followed by a late asthmatic response

V. Intrinsic asthma – Asthma that do not have it’s origins in the antigen-antibody response. These patients usually have no hx or family hx of any allergies.

a. The factors that cause this type of asthma are elusive and hard to determine in the clinical setting. They include:

üInfections – maybe bacterial, usually viral upper airway infections contribute to this asthma. (RSV)

üExercise – associated with vigorous exercise(Tennis); exercise in cold, dry air also may provoke an asthmatic response

üPollutants, Occupational irritants – exposure to irritants such as ozone, dust noxious gases; in occupational includes organic dusts, and various chemicals *Inhalation of cigarette/marijuana smoke is related to bronchoconstriction and inflammation.

üDrugs, Food additives/preservatives – There are certain drugs (usually aspirin or NSAIDS) that can induce an asthma attack. Food additives such as dyes, preservatives and antioxidants found in foods are also related.

üGERD – with or without regurgitation can induce bronchoconstriction in some patients.

üNocturnal – Some patients may suffer more from symptoms of asthma late in the night and early morning hours.

üEmotional stress – asthma induced with emotional or psychological factors

üPremenstrual Asthma – usually occurs in the late luteal phase of ovarian cycle when progesterone and estrogen levels are at the lowest

Clinical Manifestations of Asthma

I. Classic signs & symptoms suggesting asthma found in the clinical setting include:

üEpisodic wheezing – the absence of wheezing does not exclude asthma

üSOB - subjective

üChest tightness

üCough – sometimes can be the only sign of asthma (cough-variant asthma)

b. Note: Wheezing is NOT an immediate sign that a patient is suffering from asthma. Several factors can mimic the wheezing of asthma.

c. The patient will have signs and symptoms of increased WOB such as use of accessory muscles of both inspiration and exhalation

d. Increased cough and sputum production

e. Pulsus Paradoxus – when there is severe alveolar air trapping/hyperinflation pulsus paradoxus can present.

üThe systolic blood pressure will be 10 mmHg lower on inspiration than exhalation. This is due to extreme negative pressure required to ventilate.

f. Hyperresonance on percussion

II. Chest Radiograph –

a. Hyperinflation

b. Linear infiltrates, mucus plugs, maybe some atelectasis

c. Asthma CXR

III. PFT findings include (pp. 200):

a. Decreased flows (FEC, FEV₁, etc.)

b. Increased residual volumes and capacities, with exception to IC and ERV

IV. Staging Asthma refer to (table 13-1) - the NIH has categorized asthma in 4 stages:

a. Stage 4 - Severe persistant: This is the patient who is taking all these drugs and still has frequent exacerbations. Oral steroids are added to inhaled corticosteroids. Symptoms are affecting activities of daily life. PEFR are about 60% of predicted.

b. Stage 3 – Moderate persistant: This person must be on higher doses of inhaled steroids and needs a long-term Beta II such as salmeterol to keep from having daily symptoms & frequent nocturnal asthma. His PEFR is about 60-80% all the time.

c. Stage 2 - Mild persistent: Will have to add a steroid MDI for daily prevention because of increased Beta II rescue drugs to more than once a week. The patient’s asthma may be affecting sleep, and symptoms are still less than once a day. Use of long-term Beta II maybe started.

d. Stage 1 - Mild intermittent: Takes a Beta II drug less than once a week & whose asthma affects his sleep only once a month. As a baseline, will have a PERF or FEV1 that is close to 80% of predicted.

V. Peak Flow – The use of a peak flowmeter is a very useful tool for an asthmatic and helps clinicians determine the level of exacerbation that the patient is experiencing

a. Because SOB is subjective, many mild to moderate asthmatic are trained to measure their PEFR daily to establish a baseline.

b. After complete education regarding his current home drug schedules and triggers, the patient record triggers with his PEFR & over time the patient gets an idea about what works.

c. He gets an idea of what his ‘personal best’ PEFR happens to be. Based on the level of the patient’s asthma, his personal best may not be within 80% of predicted.

d. Some peak flowmeters utilize colored indicators to grade the amount of exacerbation.

Green zone	Yellow Zone	Red Zone
Patient is within ‘personal best’ PEFR. Continue current regimin	The patient’s PEFR has dropped to a lower level as determined by the MD  The patient has instructions to increase his medication & to possibly call the doctors office.	When the patient reaches this level of PEFR, he should call the MDs office for an appointment without delay. If his history warrants it, his doctor may have given him instructions to go to the ER without delay.

VI. ABG findings

a. Asthmatics with mild-moderate disease will usually have a normal ABG. If they are in exacerbation they may present with:

üUncompensated Respiratory Alkalosis with mild hypoxemia

b. If an attack goes untreated, or mismanaged the patient will eventually fall into:

üUncompensated Respiratory Acidosis with some degree of hypoxemia

VII. Lab Findings

a. Eosinophils – may increased, but not diagnostic for Asthma

b. Kirschman spirals – casts of mucus found microscopically

c. IgE – elevated in extrinsic

Treatment in Asthma

I. Education – Educations plays a large role in the management of asthma.

a. Environmental control – Efforts should be made to ensure that a patient’s environment is clear of triggers.

b. Know triggers! – A patient who knows the triggers to his asthma, can avoid them. Triggers

c. Proper use of home therapies.

d. Patient compliance

II. Oxygen Therapy – Treat hypoxemia in an asthmatic patient as you would a normal healthy person. Unless there is a chronic factor.

III. Bronchial Hygiene – Once wheezing has been resolved, bronchial hygiene may begin

IV. Medication

a. Bronchodilators – Include both sympathomimetic and parasympatholytic agents are used in exacerbation, some drugs can be inhaled q1 to even continuously.

b. Xanthines – used to encourage bronchial smooth muscle relaxation

c. Cortocosteroids – Usually used as maintenance drugs when environmental factors can not be controlled; Can be used IV in acute exacerbation

d. Other anti-inflammatory agents – Intal, Tilade, & leudotriene inhibitors

V. Treatment of Status Asthmaticus

a. Status Asthmaticus is defined as a severe asthma attack that is not responsive to conventional drug therapy.

b. Measures that could be taken for SA:

üContinuous Beta II agonist by SVN such as the Heart® nebulizer with doses albuterol at 10-15 mg/hr. 

üIV magnesium sulfate

üIV steroids

üAtropine or ipratropium bromide

üSubQ 0.25 ml of Terbutaline sulfate can be repeated in 30-60 minutes

ü Use of Heliox

üInhaled anesthetic agents

VI. Mechanical Ventilation – may be necessary if other methods fail and the patient falls into respiratory failure.

a. Use largest tube possible

b. Patient may need to be paralyzed

c. Watch for auto-peep, may need to increase I:E ratio

d. Synchronize bagging