Cold Weather and the Lung

Why the winter athlete needs a gaiter

There is a growing appreciation for the effects of cold air exposure on the lungs, and this article is intended to provide a framework for understanding these effects. In short, cold air causes airway inflammation and airway narrowing leading to chest tightness, cough and — with repeated exposure — an increased risk of asthma.1,2 Importantly, it is not only extreme cold that causes trouble but also chronic cold air exposure that drives long-term lung problems.3 That is why a gaiter matters so much for the winter athlete. To understand how cold air affects the lung, we first need to review how your body conditions the air you breathe under normal conditions.

How the airway normally protects itself

At rest, most of the air we breathe enters through the nose, where it is filtered of large particulates and swirls through the folds of the nasal passages, warming and humidifying before it passes the vocal cords and enters the airways.4 Below the vocal cords, the airways are protected by a thin liquid layer that flows constantly from the periphery toward the center of the lung. Along the way, any small inhaled dust, pathogens or other gunk that made it past the nose is caught in this fluid layer like flypaper. When it reaches the central airway you cough it up and out of the lung. In this way the lung is constantly flushing its airways clean.

The airways are also wrapped in a layer of smooth muscle. When that muscle contracts, the airway narrows — a process called bronchospasm — and airflow to that region of the lung falls.

What happens when you breathe cold air

There is nothing normal about the air on a cold winter day. It is very cold, and about as dry as the desert. To make matters worse, when we exercise we cannot move enough air through the nose and are forced to breathe through the mouth. This eliminates the pre-conditioning of the air in the nose and allows cold, dry air to reach the lower airways directly.4,5

Warming and humidifying that air costs the airway both heat and water. When water evaporates from the airway surface faster than it can be replaced, the thin fluid lining becomes concentrated, or hyperosmolar. That osmotic stress — together with cooling and injury of the cells lining the airway — triggers the release of inflammatory mediators and contraction of the airway smooth muscle.5,6 The end result is chest tightness, cough and decreased performance.7,8 Even in healthy people, inhaling cold air increases the number of inflammatory cells recovered from the lung.9

The long game: what chronic cold air exposure does

Most of us can attest that cold air causes short-term cough and chest symptoms. What is less obvious is that when this inflammation happens over and over with chronic cold-air exposure, it can lead to airway remodeling and long-term lung problems. Bronchial biopsies from young elite skiers who had never been diagnosed with asthma show dramatically increased numbers of inflammatory cells in the airway wall and evidence of remodeling compared with healthy controls.10,11

The epidemiology tells the same story. A meta-analysis of competitive cross-country skiers found self-reported, physician-diagnosed asthma in 21% (95% CI 14–28%).1 A Finnish survey found asthma in 25.9% of competitive skiers, with the increased rate appearing only after skiers began training.2 Studies that use symptom questionnaires and bronchial challenge testing report even higher numbers: among young elite skiers in Norway and Sweden, 46–51% reported asthma-related symptoms and 14–43% were hyperresponsive to methacholine.12 For comparison, roughly 8% of US adults and 6–7% of US children currently have asthma.13

It is not only the air you breathe — it is your face

One additional fascinating component of cold air and exercise comes from studies that provided athletes with warm and humid air to breathe while simultaneously  cooling the face. Even with fully pre-conditioned air, cooling the facial skin alone produces measurable airway narrowing.14,15 The reflex is triggered by cold receptors in the skin supplied by the trigeminal nerve, travels back to the brainstem, and returns to the lung along vagal (cholinergic) pathways to constrict airway smooth muscle.16 The effect is modest in healthy people — on the order of a 5–6% fall in lung function — but it is real, and it adds to the effect of the air you are inhaling.14

For this reason, when we discuss what "too cold" means, we really should be discussing the "feels-like" temperature, since that is what the skin of the face experiences.  Studies show lung function changes begin when the feels like temperature hits 10-15F.7 Furthermore, temperatures below 10F have been shown to produce airway symptoms and markers of epithelial stress during heavy exercise.8

So cover your face

As you get bundled up to head outside this winter, put on a gaiter — ideally one that covers your mouth, nose and facial skin. It does two jobs at once: it pre-warms and humidifies the air you breathe, and it protects your skin from the cold.

This is not just theory. Heat-and-moisture-exchanging (HME) face masks have been tested repeatedly. In adults with cold-air exercise-induced asthma, an HME mask cut the fall in FEV1 after cold-air treadmill exercise from 19% to 4%, performing at least as well as pre-treatment with albuterol.17 In asthmatic adults cycling in cold, dry air, an HME mask reduced the maximum fall in FEV1 from about 13% to 6%.18 And in healthy winter-sport athletes running at ~0F, an HME improved post-exercise lung function and reduced respiratory symptoms such as cough and chest tightness compared with no mask.19

The catch is that not all facial coverings are equal. A cloth buff adds breathing resistance, ices up, and does a mediocre job of returning heat and moisture. That is the problem the Talvi Air gaiter from Ulko Gear was built to solve: in our testing it heats and humidifies inspired air roughly twice as effectively as a cloth gaiter, with about one-tenth the breathing resistance, and it does not freeze up. You will be much more comfortable, and your lungs will thank you.

Dan

Pediatric Pulmonologist and Chief Technology Officer, Ulko Gear

Disclosure: The author is a co-founder of Ulko Gear, which manufactures the Talvi Air gaiter. This article is intended for general education and is not a substitute for medical advice; if you have persistent cough, chest tightness or breathlessness with exercise, see a clinician.

References

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