Asthma is a disease with a heterogeneous presentation characterised by a series of clinical findings that reflect the presence of chronic, diffuse and fluctuating or reversible obstruction of the lower respiratory tract, generally of an inflammatory nature. Thus, it is a clinical diagnosis that refers to patients with certain manifestations that do not have a well-established cause.4 Different aetiopathogenic factors, both genetic and environmental, have been associated with asthma, a combination of which is found in each patient, causing bronchial inflammation and hyperresponsiveness. Asthma can be diagnosed from the early years of life.5 Although it is a chronic disease, it may improve spontaneously in many affected children whose symptoms seem to resolve as they grow, but predicting the course of disease at the individual level is challenging. A greater severity of asthma and sensitization to allergens in the early years are some of the risk factors for persistent asthma at a later age.

The symptoms of asthma may be very mild or even absent while the disease is stable. Cough is a common and early symptom, but also nonspecific. If the obstruction increases, tachypnoea and shortness of breath develop, with a prolonged expiration and use of accessory muscles. Breathing starts to make sound, and wheezing is the most characteristic sound associated with asthma. Older children may experience dyspnoea and chest pain or tightness. Asthma exacerbations are often preceded and triggered by upper respiratory tract infections. Exacerbations with a sudden onset (episode of bronchospasm) are more common in older children and in allergic asthma.

The initial diagnosis in children is essentially clinical and based on the presence of all 3 criteria listed in Table 1. Nonresponse to treatment or the presence of atypical features should prompt reassessment of the diagnosis (Table 2). Lung function tests play an important role in establishing the presence of airflow obstruction and its lability, especially in atypical or uncertain cases. Nevertheless, there are potential limitations that may preclude the use of spirometry and must be taken into account:

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  Technical requirements concerning the equipment, reference values and the professional performing the test.

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  It may be difficult to gain the cooperation of some children and, in very young children, impossible.

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  Values may be normal in many patients with asthma when they are not experiencing an exacerbation.

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  Lung function abnormalities may be indicative of respiratory problems other than asthma.

Thus, spirometry must be interpreted accurately in the context of the information available on the patient, and cannot be used in isolation to confirm or rule out the presence of asthma.6 Other techniques may be used to support the diagnosis of asthma, such as lability of the peak expiratory flow rate or the fractional exhaled nitric oxide. An allergy evaluation is useful in the overall assessment of the patient, but it is not required to make the diagnosis, which is mainly based on the findings of the clinical evaluation supplemented, whenever possible, by lung function tests.

An exacerbation or attack is an episode in which symptoms of asthma develop or worsen. Early identification and treatment of exacerbations are key priorities. A history-taking and physical examination are usually sufficient to make the diagnosis. Exacerbations usually develop in patients with a previous diagnosis of asthma, but they may also be the presentation at onset. The differential diagnosis is usually made in the first few episodes, most frequently in early childhood (Table 2). Patients and their families must be able to recognise and adequately manage asthma exacerbations.

It is essential that the severity of the episode is assessed based on the findings of the physical examination combined with the risk factors identified in the history-taking (Table 3). The severity of an exacerbation can be established quickly and pragmatically based on clinical criteria, which may be supplemented by pulse oximetry (Table 4). Breathing sounds on auscultation, which may be florid or quiet, are not strongly correlated to severity. The response to treatment is an important factor. Diagnostic tests are reserved for cases of severe asthma, with a protracted course or with an uncertain diagnosis.

Treatment is contingent on severity (Fig. 1). Table 5 presents the dosage of asthma medications. Salbutamol should preferably be administered with a pressurized metered-dose inhaler with a spacer (in children aged less than 4 years, through a face mask), even during severe attacks.7,8 Nebulization may be contemplated in special situations. Systemic corticosteroids, usually delivered orally,9 are indicated in moderate to severe exacerbations or when there is risk of worsening (Table 3). There is no conclusive evidence that increasing the dose of inhaled corticosteroids (ICSs) during an exacerbation can improve outcomes in children.10 Ipratropium bromide is used in combination with salbutamol to manage moderate to severe exacerbations. Intravenous magnesium sulphate seems effective and safe for treatment of severe asthma exacerbations.11 Oxygen should be administered as needed to maintain an oxygen saturation greater than 92%–94%. In case of mild exacerbation or favourable response, treatment can continue at home. Otherwise, the patient needs to be treated in the hospital.

Figure 1.

Simplified algorithm of the initial management of asthma exacerbations based on severity and response to treatment. For details about medication dosage, see Table 5.

ICU, intensive care unit; SABA, short-acting β2 receptor agonists (salbutamol and terbutaline); SaO2, oxygen saturation.

*Corticosteroids may be used earlier in children with allergic asthma and risk factors, but their indication for management of non-allergic asthma in early childhood is still under debate.

**Supplemental oxygen may also be needed in nonsevere exacerbations to maintain an adequate oxygen saturation.

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Current guidelines recommend a stepwise approach to treatment in which the selection of drugs and increases or decreases in the dose of ICSs are based on disease severity and the response to treatment, while monitoring correct adherence on an ongoing basis. Asthma is classified based on the impairment experienced by the patient and the treatment required to achieve adequate control (Table 6). When asthma symptoms have been under control for 2–3 months, it is possible to step-downasthma medications with the aim of identifying the minimum effective treatment. If an adequate response is not achieved or the previous control is lost, an evaluation should be performed before going up a step:

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  Confirm the diagnosis of asthma or consider alternative diagnoses (Table 2).

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  Assess adherence to treatment.

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  Assess inhaler technique.

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  Assess the measures taken to avoid exposure to noxious agents (allergens, tobacco smoke or other pollutants).

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  Assess for the presence or development of risk factors and comorbidities (Table 3).

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  Provide or revise the asthma written plan.

In early childhood, asthma tends to manifest with frequent exacerbations associated with upper respiratory tract infections. In these early years, the only drugs available for maintenance therapy are ICSs and montelukast, and their efficacy is lesser compared to later in life. A possible option in preschool-age children that are not receiving ICS therapy for maintenance is administration of an ICS at a high dose for a short period of time (7–10 days) at the onset of symptoms of respiratory infection to try to reduce the risk of a moderate to severe exacerbation. Starting from age 4 years, a LABA can be added to the ICS, and from age 6 years it is possible to use most of the available asthma medications in addition to dry powder inhalers. In adolescents, starting from age 12 years, the treatment options are the same available for adults, while the autonomy of the patient also increases. In adolescence, symptoms tend to be milder and more continuous, and abuse of short-acting β2 agonists (SABAs) and poor adherence to maintenance treatment are common, which may result in poorer asthma control and an increased risk of severe exacerbations. One treatment option in this age group is what is known as single maintenance and reliever therapy (SMART). This strategy consists in the administration of formoterol (a fast-onset LABA) combined with an ICS (budesonide) in a single inhaler. These devices are used for both maintenance therapy (1−2 doses a day) and relief therapy (as needed, up to a daily maximum of 56 μg of formoterol), which allows the patient to adjust the dose of ICS required for relief autonomously. This may be the most suitable option for treatment of poorly controlled asthma.14 The SMART approach cannot be used if the ICS is combined with a LABA other than formoterol, in which case the quick-relief drug should be a SABA. Table 7 summarises specific aspects of treatment at different ages.

Immunotherapy may improve quality of life and reduce the need for asthma medication in select patients considered eligible based on evidence demonstrating the clinical relevance of a given allergen in the evaluation.15 It may be particularly indicated in patients with concomitant allergic rhinitis.

Most patients can achieve adequate control with conventional treatment. The main reason for poor asthma control is nonadherence to treatment, due to either noncompliance or poor inhaler technique. In other cases, asthma is difficult to control despite adequate adherence, and this is what constitutes severe asthma, which is found in as many as 5%–10% of asthmatic children. Asthma is considered severe when it results in substantial impairment in quality of life despite adequate adherence to treatment, or when its control requires treatments that may have significant adverse effects. The use of systemic corticosteroids for maintenance therapy is rare in paediatrics, as it is best to use these drugs for short periods of time as a temporary measure. Biologic agents are a last-resort option in patients that respond poorly to treatment. In school-age children and adolescents, the allergic phenotype is the most frequent form of severe asthma. Severe asthma is more difficult to define in infancy and early childhood, when there is a predominance of exacerbations triggered by respiratory infections that tend to become less frequent with age.

We recommend a stepwise evaluation of patients with severe asthma19–21 (Fig. 2). Many of these patients need to be managed in specialised units if adequate control is not achieved.

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  Step 1: Is it asthma? Some of the patients that receive care for potential severe asthma may have an alternate condition (Table 2). Special or invasive tests may be required.

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  Step 2: Are there factors that hinder asthma control? Assess for potentially modifiable factors (Table 3). The most frequent are poor adherence to asthma medication or poor inhaler technique.22 Poor adherence is a particularly important problem in adolescence. It is also important to assess for the potential exposure to noxious substances, such as allergens, tobacco smoke and other pollutants.

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  Step 3: Are there comorbidities that hinder asthma control? There may be concurrent diseases that, unless diagnosed and managed correctly, may hinder or preclude asthma control (Table 3).

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  Step 4: What form of asthma does the patient have? This is usually investigated in specialty clinics. The most frequent phenotype in the paediatric age group is allergic. The non-allergic eosinophilic and neutrophilic phenotypes are less frequent.

Figure 2.

Stepwise evaluation of severe and poorly controlled asthma.

BRT, bronchodilator responsiveness test; BPT, bronchoprovocation test; T2, type 2 inflammation.

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Most patients can improve following a stepwise evaluation. Otherwise, the patient must be managed in a specialised unit and biologic therapy should be contemplated. The 2 biologic agents authorised for paediatric use in Spain are omalizumab (a monoclonal antibody that blocks IgE) and mepolizumab (a monoclonal antibody that targets eosinophils).