How does cold air trigger bronchial asthma (Asthma)?

From the Guidelines

Cold air can trigger asthma by causing the airways to narrow and become irritated, leading to inflammation, increased mucus production, and bronchospasm, as supported by the most recent and highest quality study 1. When someone with asthma breathes in cold air, it cools and dries the airways, which can irritate sensitive airways. This process happens because cold air contains less moisture, and the body attempts to warm and humidify the air before it reaches the lungs. Some key points to consider:

• The pathophysiology of exercise-induced bronchoconstriction (EIB) has been elucidated, and it is known that strenuous exercise creates a hyperosmolar environment by introducing dry air into the airway with compensatory water loss, leading to transient osmotic change on the airway surface 1.
• The hyperosmolar environment leads to mast cell degranulation with release of mediators, predominately leukotrienes, but also including histamine, tryptase, and prostaglandins, which can lead to bronchoconstriction and inflammation of the airway 1.
• To prevent cold-induced asthma attacks, individuals should cover their nose and mouth with a scarf or mask when outdoors in cold weather, pre-medicate with a rescue inhaler (like albuterol) 15-20 minutes before cold exposure if recommended by their doctor, gradually warm up before exercise in cold conditions, and maintain their regular asthma medication regimen 1.
• Some people may need to adjust their asthma action plan seasonally with their healthcare provider to better manage symptoms during colder months, as the prevalence of EIB is poorly defined and can vary among individuals 1. The airway inflammation and hyperresponsiveness associated with asthma can be managed with therapeutic interventions, including short-acting b2-agonists (SABAs) and anti-inflammatory medications, such as inhaled corticosteroids (ICSs) and leukotriene receptor antagonists (LTRAs) 1.

From the Research

Mechanisms of Cold Air-Induced Asthma

• Cold air can trigger bronchial asthma through various mechanisms, including airway smooth muscle contraction, mucus accumulation, and bronchial vascular congestion, as well as epithelial damage and vascular leakage 2.
• The primary stimulus for cold air-induced asthma is likely a combination of airway cooling and drying, leading to hypertonicity of airway lining fluid 2.
• Hyperventilation of dry air can cool the central airways and trigger subclinical bronchial obstruction in healthy subjects, and can cause asthma attacks in asthmatic subjects 3.

Effects of Cold Air on the Airways

• General exposure to cold air can cause pulmonary vasoconstriction, known as "Raynaud's phenomenon of the lung" in subjects with primary Raynaud syndrome, and can favor acute pulmonary oedema in subjects with congestive heart failure 3.
• Repeated hyperventilation of subfreezing air can cause "eskimo lung", a condition characterized by obstructive lung disease and increased wall thickness of pulmonary arteries 3.
• Cold air-provoked respiratory symptoms can be triggered by short-term responses to sudden cooling of the airways, long-term responses to repeated and long-standing cooling and drying of the airways, or physiological, reflex-mediated lower-airway responses to cooling of the skin or upper airways 4.

Relationship Between Asthma Control and Cold Weather-Related Respiratory Symptoms

• Subjects with poorly controlled asthma are more prone to experience cold weather-related respiratory symptoms, including shortness of breath, cough, wheezing, phlegm production, and chest pain 5.
• The relationship between asthma control and symptom occurrence is stronger among smokers and subjects with a body mass index (BMI) below or above 25-30 5.
• Even a slight worsening of asthma control can increase the prevalence of cold weather-related respiratory symptoms 5.