Introduction

Asthma, a medical condition that occurs due to chronic inflammation of the airways in the lungs. The airways are the pipes that allow air passage into and out of the lungs.

Asthma has a pattern of the airways becoming inflamed and then narrowing over time. This condition presents a problem when someone tries to breathe out, as air does not exit freely.

One in every thirteen people is asthmatic in the United States, according to statistics by the Centres for Disease Control (NIH). It may occur at any age, but most commonly begins in childhood. Asthma worsens with certain agents, called asthma irritants, such as pollen, a viral infection, or even cold weather.

Although asthma can be challenging as it does not have a specific cure, there are preventive measures and an asthma action plan that can help tackle the problem. Such a plan may address issues, including but not limited to monitoring the condition, avoiding known triggers, and taking medication.¹

Chronic sinusitis

Sinusitis is a clinical term describing the inflammation of the paranasal sinuses lasting for at least three months, or which does not resolve at all. Inflammation of the sinuses leads to nasal airway inflammation; for conditions in which the symptoms of rhinitis occur first, chronic rhinosinusitis (CRS) is a more appropriate term. CRS is one of the most frequently occurring chronic illnesses in the US and affects every age group. 

An individual with CRS may present with one of the three major clinical indications:

• Chronic rhinosinusitis without nasal polyps (CRSsNP)
• Chronic rhinosinusitis with nasal polyps (CRSwNP)
• Allergic fungal sinusitis

The treatment approach in CRS can be medical and/or surgical.²

Prevalence and overlap between asthma and sinusitis

The upper and lower respiratory tracts are connected, so many patients diagnosed with asthma also report chronic sinusitis.

Research studies suggest that chronic sinusitis is a very potent trigger of asthma. Literature in both children and adults indicates that adequate treatment or surgical intervention of sinusitis usually results in an improved condition of asthma.

Some rational explanations for this include the eosinophil (a type of white blood cell) acting as a cell mediator of inflammation, the involvement of an inflammatory mediator, and a reflex via the vagus nerve.³

Pathophysiology of asthma and chronic sinusitis

In asthma, the lower airways are inflamed and infiltrated by inflammatory cells such as: 

• Dendritic cells
• Mast cells
• Eosinophils
• T lymphocytes
• Macrophages
• Epithelial cells

These cells activate inflammatory processes resulting in changes in the airway, such as epithelial desquamation, hyperplasia of the mucus glands, hypertrophy of the smooth muscles, and collagen deposition. These alterations begin as fully reversible, but eventually become permanent, resulting in thickened airways, obstruction, and hyper-responsiveness.

Asthma manifests as different clinical types or endotypes, two of which are:

T2-high asthma

In T2-high asthma, there is eosinophilic inflammation as a result of the activation of Th2 cells and their associated cytokines (IL-4, IL-5, IL13), which lead to IgE production and hypersensitivity.

T2-low asthma

In T2-low asthma, there is neutrophilic inflammation secondary to the dominant effect of Th17 and Th1 cells, characterised by cytokines IL-6, IL-17, and TNF alpha.⁴

CRS shares asthma's inflammatory subtypes; preliminary diagnosis is classified as type 2 (T2-high) and type 1 (T2-low) inflammation. CRS traditionally has been further classified into: 

1. CRS with nasal polyps (CRSwNP)
2. CRS without nasal polyps (CRSsNP) 

CRSwNP is characterised by type 2 inflammation featuring eosinophils and mast cells, as well as high-level IgE and cytokines such as IL-4, IL-5, and IL-13, and is closely associated with asthma. Conversely, CRSsNP is characterised by type 1 inflammation involving Th1 cells and neutrophils.⁴

What shared underlying inflammatory processes are involved?

Asthma and chronic rhinosinusitis with nasal polyps (CRSwNP) share a common type 2 immunopathology characterised by epithelial barrier dysfunction.

The upper and lower airways of asthmatic patients with CRSwNP exhibit increased levels of type 2 cytokines (IL-4, IL-5 and IL-13) as well as release of immune mediators in an IgE-dependent manner.

Patients suffering from CRSwNP who present a type 2 immune response (IgE, eosinophil, IL-4/IL-13, and IL-5 related) represent an exhausted, more destructive type of CRS, with higher rates of polyp recurrence and hard operative asthma.

Patients suffering from CRSwNP and asthma demonstrate high levels of tissue eosinophilia and raised local IgE levels. Moreover, lower airway eosinophilic CRS disease (with both subtypes) is common in Japan.

In addition, the presence of eosinophilia in the CRSwNP tissues changes the sense of smell. More specifically, some inflammatory cytokines released by eosinophils themselves may be partly responsible for the hyposmia or the complete loss of smell.⁵

Symptoms of acute severe asthma

For most people, the symptoms of acute severe flare-ups happen more often within some hours or days. Yet, these symptoms might occur in an even shorter period. They are:

• Difficulty in breathing and an increased degree of wheezing
• Increased respiration rate
• Coughing and a worsening feeling of constriction in the chest
• Difficulty in breathing, especially when lying down
• Inability to walk or even speak
• Increased sweating
• Increased heart rate
• A state of confusion and agitation⁶

Signs and indications of sinusitis 

The following are the usual signs and indications of a sinus infection:

• Post-nasal drip cough
• Nasal discharge – discolouration (mostly green colours)
• nasal congestion or blockage
• Facial pain or swelling, especially beneath the eyes or over the nose
• Shooting pain in the head
• Pain in the jaws
• Spitting
• High temperatures
• Exhaustion
• Halitosis⁷

Management and treatment of acute asthma

Asthma attack episodes require medical intervention and management of such episodes over long periods, including nighttime treatment and physical activity-induced manifestations.

Pharmacologic management includes the use of

• Control agents, such as inhaled corticosteroids
• Long-acting bronchodilators (beta-agonists and anticholinergics)
• Theophylline
• Leukotriene modifiers 

These strategies include the use of monoclonal antibodies to control allergic asthma, anti-IL5, and anti-IL4/IL13 targeted therapies in specific patient populations. Short-acting bronchodilators and corticosteroids are examples of reliever medications.

A stepwise management of asthma (step-up or step-down) has been a common practice in asthma guidelines. Management is classified into three groups: 0-4 years old, 5-11 years old, and 12 years old or older.

For all patients, quick-relief medications, including rapid-acting beta-2 agonists, can be used when necessary to relieve symptoms. The intensity of treatment depends on the severity of symptoms.⁸

Management and treatment of chronic rhinosinusitis

The treatment focuses on facilitating mucociliary clearance, enhancing sinus drainage and eliminating local infection and swelling; facilitating access to topical drugs. First-line treatment is nasal saline irrigation and intranasal corticosteroid sprays. Antibiotics may be used for a subset of patients with signs of active, superimposed acute sinus infection. 

If medical management is ineffective, endoscopic sinus surgery is offered. Patients with poor response to first-line medical treatment are referred to an otolaryngologist, and patients with pertinent medical history of other comorbidities (such as vasculitis, granulomatous diseases, cystic fibrosis, and immunodeficiency) are referred to an allergist or a pulmonologist.⁹

Summary

Asthma and chronic rhinosinusitis (CRS) are two conditions that tend to exist together since they both involve the submucosal airway layer’s inflammation. Asthma has its primary effector cells characterised as T2-high, which are predominantly eosinophilic and allergic cytokines (chiefly IL-4 and IL-5) driven, and T2-low types, which are primarily neutrophilic.

Such conditions are further subdivided into chronic rhinosinusitis with nasal polyps (CRSwNP) and chronic rhinosinusitis without nasal polyps (CRSsNP). The former type is a type 2 predominant inflammation, which resembles the asthma's T2-high subtype.

The overlapping inflammation patterns between asthma and CRS suggest that sinusitis can also be a precipitant of asthma episodes, hence, the two diseases ought to be addressed concurrently for better results.

Episodic attacks of asthma with chronic exposure to sinusitis exacerbate respiratory symptoms such as shortness of breath, wheezing, and chest tightening. When sinuses become infected, they obstruct the nasal passages and start dripping, which may further affect the airways and provoke asthmatic attacks.

Therefore, appropriate treatment of sinusitis can help reduce the frequency of asthma attacks and improve patients’ health.