Introduction

Croup is a common respiratory illness that causes characteristics seal-like barking cough in children. Croup affects respiratory pathways of our body (trachea, larynx, and bronchi) and can bring on inspiratory stridor(characteristic turbulent noisy airflow).¹

Croup results in generalized airway inflammation and oedema of the airway mucosa.²  Airway obstruction causes respiratory distress, and thus a barky cough is produced. Croup is caused primarily by virus infection. What causes this barking cough in babies and children? This article lets you know more about typical barking cough and asthma in children.

Incidence

• Croup affects 3% of children per year. Croup affects children less than 6 years¹ 
• Croup is frequently present in children in the age group between 3 months and three years and is more common in boys than girls(1.5:1). It can also occur in children less than 3 months
• Parainfluenza virus accounts for the majority (75%) of croup infections
• Recurrent croup is seen in children who are sensitive to viral antigens

Causes of croup

Croup is most commonly a viral infection. Croup can also be caused by bacterial infection.

Viral

• Parainfluenza virus commonly causes viral croup or acute laryngotracheitis, primarily types 1 and 2¹
• Influenza A and B
• Measles
• Adenovirus
• Respiratory syncytial virus (RSV)

Spasmodic croup is caused by viruses but lacks signs of infection.

Bacterial

Bacterial croup is divided into:

• Bacterial tracheitis
• Laryngotracheobronchitis
• Laryngotracheobronchopneumonitis and
• Laryngeal diphtheria

Laryngeal diphtheria is caused by Corynebacterium diphtheriae.

Bacterial tracheitis, laryngotracheobronchopneumonitis and laryngotracheobronchitis¹ typically begin as viral infections, which worsen due to secondary bacterial growth.

The common bacterial causes are

• Staphylococcus aureus
• Hemophilus influenza
• Streptococcus pneumoniae, and
• Moraxella catarrhalis

Signs and symptoms 

Croup is characterized by a barking cough like a seal

• Stridor, hoarseness: Stridor can be heard at rest
• Difficulty breathing, which  becomes worse at night¹ 
• Fever and dyspnea: Fever is absent in some cases
• Increase in heart rate and respiratory rate (20 to 30 breaths per minute) 
• Visual inspection of nasal flaring
• Cyanosis (rarely)
• The duration of the croup could be 3 to 7 days. Severe symptoms occur on days 3 or 4

Evaluation

1. Westley score is used for classifying the severity of croup. Croup can be classified according to severity by Westley score. Westley's score consists of points ranging from 0 to 17 divided by five factors:
   • Stridor
   • Retractions
   • Air entry
   • Cyanosis
   • Level of consciousness¹

2. Nasal washings for influenza, parainfluenza, and  Respiratory syncytial virus serologies
3. Obstructive conditions, such as epiglottitis, an airway foreign body, subglottic stenosis, angioedema, retropharyngeal abscess, and bacterial tracheitis must be ruled out
4. Xrays: They are not usually performed. A frontal x-ray of the neck may show a characteristic narrowing of the trachea in some cases, known as the steeple sign

^{Steeple sign on x-ray}

5. Blood tests and viral culture: They are not performed as they can lead to further airway swelling and obstruction
6. Viral cultures, via nasopharyngeal aspiration, are used to confirm croup in research settings

Treatment 

• Treatment for croup is determined by the Westley score. 
• Children with mild croup; and Westley croup scores less than 2 are given a single dose of dexamethasone¹
• Children with moderate to severe croup; and Westley croup scores greater than 3 are nebulised with epinephrine and dexamethasone
• People with diminished oxygen saturation should receive supplemental oxygen
• Moderate to severe cases of croup require observation for up to 4 hours, if there is no improvement in symptoms, hospitalisation is required
• Steroids: Corticosteroids, such as dexamethasone. Dexamethasone at a dose of 0.6 mg/kg is mostly used
• Epinephrine: For moderate to severe cases, nebulised racemic epinephrine has been found effective.0.5 mL per kg of L-epinephrine 1:1000 via nebuliser
• Oxygen: Deliver oxygen by "blow-by" administration
• Intubation: Approximately 0.2% of children require endotracheal intubation for respiratory support. Due to swelling airways are narrower hence, use a tube that is a one-half size smaller than normal for the age/size of the child
• Antibiotics: They are used for bacterial infection. Vancomycin and cefotaxime are recommended for secondary bacterial infection¹
• Hot steam
• Cough medicine

Understanding asthma

Asthma is also a common respiratory tract illness that is characterized by airway inflammation and hypersensitivity. Since the airways of children are relatively small, asthma causes a limitation of breathing air out. Persistent respiratory symptoms are found including wheezing, coughing, shortness of breath, and chest tightness.³

Asthma often starts in childhood, persistent asthma is developed in children by age 6.

Genetic and environmental factors are involved in asthma development and severity. Asthma also results in airway hyperresponsiveness and inflammation.

Two groups of children exhibit wheezing and asthma-like symptoms:

1. Children experiencing symptoms are usually triggered by viral infections and tend to overcome these episodes as they age.
2. Children who develop symptoms at a later age often in combination with a family history of asthma and atopy and hence develop persistent asthma in the future.

Causes of asthma in children

• Viral infection

Respiratory syncytial virus (RSV) causes asthma in young children.

• Genetics

Genetic factors can influence asthma development.

• Risk Factors

Atopy, parental asthma, urbanization, socioeconomic status.

• Prenatal and perinatal factors

Prematurity, preterm delivery before 36 weeks increases chances for asthma due to reduced lung development.³

Maternal smoking during pregnancy is associated with reduced lung function in newborns including premature delivery, which increases the chances of childhood asthma.

Vitamin D deficiency during pregnancy may contribute to early-life wheezing and asthma due to the effects on immune function and fetal lung development.

Symptoms

• Cough: Cough that occurs primarily at night and in response to specific triggers like cold air or exercise,
• Wheezing, stridor
• Excessive daytime fatigue and poor school performance may indicate disturbed sleep due to night symptoms.
• Shortness of breath and chest tightness
• Nasal discharge, decreased air entry, inflamed nasal mucosa
• Halitosis ³
• Dark circles under the eyes, eczema, atopic dermatitis,
• Digital clubbing,
• Inability to speak in complete sentences.

Management of asthma 

Non-pharmacological management

• Non-pharmacological management includes educating patients. Asthma education explaining asthma symptoms and triggers has been proven effective
• Personalized one-on-one education reduces asthma exacerbations and hospitalizations
• Avoiding environmental triggers that could trigger asthma, such as pollutants and irritants, tobacco smoke, food or medication triggers is essential³

Pharmacological management

There is a stepwise process outlined by GINA (Global Initiative for Asthma) for choosing pharmacological therapy in children aged 5 and young. According to GINA,

• Step 1: The child experiencing wheezing should be able to use a SABA (short-acting β-agonist),
• Step 2: If a child requires a SABA more than twice a week for 1 month daily low-dose ICS (inhaled corticosteroids) is initiated along with SABA as needed, maintaining this regimen for at least 3 months
• Step 3: The initial dose of the ICS is doubled for 3 months. If asthma symptoms persist despite this adjustment, approach an asthma specialist
• Step 4:Treatment options may involve further increasing the ICS dosage, adding a Leukotriene Receptor Antagonist (LTRA), combining a Long-Acting β-agonist (LABA) with ICS, or introducing a low-dose oral corticosteroid (OCS) until symptom improvement is observed

Inhalers and nebuliser

• A pressurised metered dose inhaler with a valved spacer can be used for children 5 or younger.
• Nebulisers are used for young children³

Asthma action plans 

• Asthma action plans are necessary for asthmatic people. These plans are individualised for each patient.
• Action plans include detailed directions for managing asthma during the onset of symptoms or worsening of conditions³

Biological agents

• Biological agents used in children are Omalizumab, Dupilumab, Mepolizumab⁴

Magnesium sulfate 

• Children who do not respond to SABAs, ipratropium, and glucocorticoids receive magnesium sulfate (MgSO4)
• The addition of MgSO4 to the treatment regimen for children reduces hospitalisation in severe asthma cases

Parenteral β-agonists 

• Subcutaneous and intramuscular β-agonists, such as epinephrine and terbutaline, can be used for children presenting with severe symptoms or those unable to cooperate with nebuliser treatments.

Glucocorticoids

• Glucocorticoids can be administered in children with moderate-to-severe asthma, early administration reduces hospital admission rates
• Oral and IV glucocorticoids have equivalent effects but OCS are preferred more since they are less invasive

 Croup and asthma

• Croup and asthma are common inflammatory airway diseases in children
• Children living in urban areas are exposed to environmental allergens and air pollutants and hence, they might have a hyperreactive airway compared to children in rural areas. Children who develop croup due to viral infections can have inflammatory immune responses thus leading to asthma²
• Sex, age, bronchiolitis, and urbanisation level are associated with croup and asthma
• A high risk of asthma is found in children with a history of croup. They should be monitored for three years of age
• The physiological association between asthma and croup are unclear
• Croup and asthma symptoms worsen at night² 
• Genetic factors influence asthma and croup. CD14 plays a crucial role in signalling the innate immune response and detecting inflammation-provoking pathogens. People with CD14 variants of the TT haplotype are prone to asthma and croup² 

Summary

Croup is a respiratory illness seen in children less than 6 years old and characterized by a distinctive barky cough. Children with croup have seal-like barking cough. Croup is mainly caused by the parainfluenza virus.