CCFP Topic: Asthma

Due to the high prevalence of asthma, assess all patients with respiratory symptoms for the possible diagnosis of asthma.

Asthma is a chronic inflammatory disorder of the airways leading to episodes of bronchial hyper-responsiveness and thus airflow obstruction.

Symptoms of Asthma
Respiratory symptoms common in asthma include

• wheeze,
• cough,
• shortness of breath, and
• chest tightness.

Historical Items Suggesting Asthma
Features on history that are supportive of the diagnosis of asthma include: 

• Symptoms that are worse
  • at night or early in the morning;
  • symptoms that are worse in response to:
    • exercise,
    • allergens,
    • irritants,
    • viral infections, or
    • cold or humid air
    • worse after taking ASA or BBlockers
• A personal or family history of atopic disorder (asthma, allergic rhinitis, or eczema)

Differential Diagnosis Considerations:
It’s important to consider alternative diagnoses during an assessment. Features that would point to an alternative diagnosis include features such as:

• Chronic productive cough in the absence of shortness of breath or wheeze
• Significant smoking history (i.e. >20 pack years)
• Prominent light-headedness
• History of cardiac disease
• Voice disturbance
• Failure to respond to a trial of asthma therapy
• Or other features that point towards an alternative diagnosis

Physical Exam Features of Asthma:
Physical examination is often normal in cases of a suspected diagnosis of asthma. However, features that you would look for on physical examination that would further support the diagnosis of asthma include:

1. Prolonged expiration and expiratory wheeze heard on auscultation
2. Note that a silent chest in the context of asthma exacerbation is a medical emergency as it indicates an extreme level of airflow obstruction
3. In children, evidence of atopy may also support the diagnosis. This includes signs such as atopic dermatitis (eczema), linear nasal crease, and swollen nasal turbinates.

Spirometry
Now that you suspect the diagnosis of asthma based on the assessment you’ve done, how do you confirm the diagnosis?

The test of choice is spirometry both pre- and post-bronchodilator therapy.

Variable airflow obstruction and thus the diagnosis of asthma is confirmed with an

• FEV1/FVC <0.8-0.9 in children ages 6+ and <0.75-0.80 in adults
  PLUS
• a 12% or greater improvement in the forced expiratory volume in one second (FEV1)
• and 200 ml from baseline is seen 15 minutes after use of an inhaled short-acting beta-2 agonist (SABA).

However, there are some important caveats to this test:

1. appropriate pulmonary function testing can only be done in patients 6 years or older as those younger than this cannot do the test reliably. In these cases, the diagnosis is based on a compatible history and physical examination, PLUS an 8-12 week therapeutic trial. If there is notable clinical improvement with an 8-12 week trial of inhaled corticosteroids and PRN SABA’s, the diagnosis of asthma is quite likely.
2. Number two, spirometry is more reliable when the patient is symptomatic. Negative spirometry results do not necessarily exclude the diagnosis of asthma. If the clinical suspicion remains high in these cases, repeat spirometry on another occasion.

While spirometry is the preferred diagnostic test, there are other confirmatory tests available.

• Peak flow monitoring
  can provide objective evidence of variable airflow obstruction as well but can be unreliable for various reasons.
  
  A positive test is typically reflected by a >20% change after administration of a bronchodilator. 

• A methacholine challenge
  can be used to assess for airway hyper-responsiveness.
  • A series of methacholine chloride solutions are administered via nebulizer for bronchoprovocation, ranging from 0.016 mg/ml (most dilute) to 16 mg/ml (most concentrated).
  • The concentration administered is sequentially increased until a decrease >20% is observed in the FEV1.
  • This is referred to as the provocative dose or PD20. A PD20 of 4 mg/ml is typically considered a positive test whereas a PD20 or 4-16 mg/ml is considered borderline. This mode of testing is also at risk of false negatives.

• Alternatively, a post-exercise decrease in FEV1 >10-15% is also considered diagnostic of asthma. 

• A trial of pharmaceutical therapy can also be considered to confirm the diagnosis of asthma but this is not recommended unless the patient is less than 6 years old.

Note that a chest x-ray is NOT required to diagnose asthma. It may be used to rule out other diagnoses but it is not beneficial in the diagnosis of asthma.

In a child with cough and wheeze, there are several clinical features that can help distinguish the diagnoses of asthma, bronchiolitis, croup, and foreign body aspiration. 

We’ve already discussed the recognition of asthma through history and physical exam. What about bronchiolitis?

Bronchiolitis
Typically presents in young children less than a year old. This will likely be the child’s first episode of wheezing. In most cases, there is a prodrome of URTI with cough, rhinorrhea, and possible fever. Symptoms often peak at 3-4 days.

Croup
Is another common respiratory tract infection in children. 

It is common in children <6 years of age with a peak incidence between 7-36 months. It is common to see in the fall and early winter months. Clinically, there is typically a prodrome of rhinorrhea, pharyngitis, and cough and possibly a low grade fever. The history will likely also reveal symptoms that are worse at night. 

On physical examination, the child will present with a hoarse voice, a classic cough that is barking in nature, and stridor.

If a chest x-ray is done, the “steeple sign” is a common finding in which subglottic tracheal narrowing produces the shape of a church steeple within the upper trachea.

Foreign body aspiration
Is a do-not-miss diagnosis. In this case, the history will reveal a sudden onset of respiratory symptoms and perhaps a history of choking. On physical examination, you may hear stridor if the foreign body is lodged in the upper respiratory tract or monophonic or unilateral wheeze if the foreign body is lodged in the lower respiratory tract. 

Recall that this would be in contrast to asthma in which you would hear bilateral wheeze on auscultation. The diagnosis of foreign body aspiration may be confirmed with an x-ray revealing the object lodged in the respiratory tract. Note that some foreign bodies are not visible on x-ray.

In the setting of an acute exacerbation, severity is determined through a clinical assessment of the patient. Vital signs, work of breathing, accessory muscle use, and auscultation of the chest can all be used to make a clinical judgement regarding the severity of the patient’s asthma exacerbation. 

In the acute exacerbation setting, spirometry obviously is not practical to measure. Obtaining peak expiratory flow (PEF) using a mini peak flow meter is a common method of assessing airflow obstruction objectively in the Emergency Department or at home. Peak flow can be inaccurate, but if good technique is used can provide an objective measurement that can be monitored over time. 

Although definitions vary in regards to asthma severity, there are several guiding thresholds that vary according to sex, height, and age:

• Mild: PEF predicted >70%
• Moderate: PEF predicted 50-70% and does not reverse back to normal after initial bronchodilator therapy
• Severe: <200 L/min, PEF predicted <50%

Red flags indicating a severe exacerbation with need for urgent intervention include: 

• inability to speak in full sentences, 
• severe tachypnea (>30)/tachycardia (>120), 
• pulsus paradoxus, 
• cyanosis, 
• silent chest, or 
• decreased LOC. 

As an additional tool, an arterial blood gas measurement with normal or elevated PaCO2 is a sign of respiratory failure during an asthma attack.

In the setting of the outpatient, several criteria have been identified to determine the degree of well-controlled asthma:

1. Daytime symptoms occur <4 times per week, and thus rescue puffer use <4 times per week
2. Nighttime symptoms occur <1 time per week
3. Physical activity that is unimpaired by symptoms 
4. No asthma-related absences from school and work
5. Exacerbations mild and infrequent?
6. FEV1 or PEF >90% of personal best?
7. PEF diurnal variation <10-15%?

If these criteria are met, the patient exhibits well-controlled asthma.
Note that many patients overestimate their level of asthma control.

PEF monitoring at home can also help patients objectively classify their asthma using their Peak Expiratory Flow meter:

• GREEN: 80-100% personal best
• YELLOW: 50-80% personal best-      
• RED: <50% personal best

See below links and screenshots of available patients home actions plans from anxiety Canada. The top one intended for adults, and the bottom one for kids.

Treat Acute Episode:
In an acute exacerbation of asthma, the goal is for rapid reversal of airflow limitation and correction of hypoxemia and hypercapnia. 

• Supplemental oxygen should be administered to patients who are hypoxemic with an SpO2 < 90% with a target of SpO2 > 92%

• Short-acting beta-2-selective agonists (SABAs) are the mainstay of treatment of acute asthma exacerbations.
  A commonly used agent is albuterol, otherwise known as Salbutamol. Typically, this is administered three times in the first hour. Administration via metered dose inhaler (MDI) with a spacer device is as effective as nebulizer, unless of course they won’t be able to coordinate their inhalation. 

• Inhaled ipratropium, which is a short-acting inhaled anticholinergic, is added to cases of moderate or severe asthma exacerbation.
  • The dosing is 500 mcg by nebulizer or 4-8 puffs by MDI every 20 minutes for the first hour and then PRN for up to 3 hours.
    
• Early administration of systemic glucocorticoids is recommended for patients who do not have a sustained improvement in symptoms and PEF after initial SABA and anticholinergic therapy.
  • Typically, the equivalent of prednisone 40-60 mg (1 mg/kg/day) in a single or divided dose is given within the first hour.
  • There is no difference in results when comparing oral vs IV glucocorticoids. Note that it can often take up to 6 hours for the onset of action of systemic glucocorticoids to become clinically evident.

• Administration of a single dose of IV magnesium sulfate is suggested for patients with severe asthma exacerbation unresponsive to initial therapy as it can act as a bronchodilator in acute asthma.
  • This is administered as IV magnesium 2 grams infused over 20 minutes.

It’s important to note that asthmatics can decompensate very quickly so equipment and personnel for rapid sequence intubation should also be readily at hand in case it is needed.

Disposition:
After initial stabilization, the question remains of whether your patient can now go home or if they require admission into hospital. This is largely guided by clinical judgement including the patient’s response to therapy, symptomatic status, airflow limitation, outpatient supports, as well as the patient’s history of asthma control and severity of past exacerbations. Each patient requires an individualized assessment. 

However, a general approach is as follows:

• After the first hour of treatment, a patient whose symptoms have resolved and PEF is >80% can be discharged home safely.

• If a patient has had an incomplete response and their PEF remains between 60-80%, they must be observed for another 1-3 hours and reassessed after that time.

• If following those 1-3 hours, the patient has not shown significant improvement or their PEF remains unchanged, they will need to be observed overnight in the Emergency Department or admitted to hospital.

Rule out Co-Morbid Disease:
In an acute exacerbation of asthma, features suggesting a co-morbid disease or an alternative diagnosis should always be considered. It’s important to maintain a broad differential and inquire about other symptoms using a systems-based or head-to-toe approach.

For example, symptoms that should prompt consideration of another diagnosis include:

• fever,
• purulent sputum production,
• pleuritic chest pain,
• orthopnea,
• PND,
• peripheral edema,
• urticaria…
• and so on and so forth.

Once a diagnosis of asthma has been made, maintenance asthma therapy should be initiated. In asthma, initiation of inhaled corticosteroid, either alone or in combination with a long acting beta-agonist is recommended. The medication may be prescribed on an as needed basis or everyday, with the goal of elimination of symptoms of asthma. 

You can consider stepping up therapy if symptoms are not routinely controlled or if the patient continues to have recurrent asthma attacks at the current step. Before stepping up, it is important to ensure the diagnosis is correct, review the patient’s self-management education, lifestyle, and environment, and ensure the patient is taking their medication appropriately

You can consider stepping down therapy if symptoms are controlled for >3 months and the risk of an acute exacerbation is low.

It is important to note that the guidelines for asthma management are currently under review. Most notably, it is likely that the recommendation for SABA alone use will have been removed and will be replaced with SABA + ICS/LABA on demand. Stay tuned!

Patients can use their Asthma Action Plan to monitor how well their asthma is controlled. An Asthma Action Plan should be completed with all patients with the diagnosis of asthma. This is a written plan developed by patients and their physicians which includes symptoms and signs to help patients recognize their current level of respiratory distress, which is broken down into a green zone, yellow zone, and red zone. They are able to assess themselves subjectively via symptoms and objectively via PEF measurements. The Asthma Action Plan then gives patients direction regarding treatment adjustments for each zone. 

Depending on the patient’s asthma control, follow up visits can be scheduled accordingly every 1-6 months.

Patient education is key to the care of the asthmatic patient. As we discussed, a patient’s asthma control can be assessed using various criteria. 

A discussion regarding adherence with medication and appropriate use of inhalers should be done at every visit. Ensure that there are no barriers to medication adherence such as cost or inhaler burden such as multiple inhalers that can be simplified to combination inhalers. Additionally, ensure that the patient is using the correct technique. 

In addition to optimizing medical management, lifestyle should also be discussed. It is important to discuss smoking cessation and weight loss. The patient should be aware of their own personal triggers and should avoid such triggers. 

Common asthma triggers include: URTIs; allergens such as pet dander, house dust, moulds, and cockroaches; irritants such as cigarette smoke and poor air quality; drugs such as NSAIDs and BB; and preservatives such as MSG and sulfites. Other triggers include heightened emotions, anxiety, exercise, cold air, and GERD. 

Referral to an asthma specialist is important if patients have uncontrolled asthma (with oral steroid use or emergency department visits) so that the diagnosis can be confirmed and therapy can be augmented to include biologic medication where appropriate.