Respiratory effects of sauna

Respiratory effects of sauna are the changes that the hot, humid air of the cabin produces in the airways and in breathing. They are generally mild and comfortable in healthy bathers — the air is warm, evaporation from the respiratory tract is relieved, and the breathing of most people slows and deepens as they relax — but they interact with the quality of the room air, with common respiratory infections, and with chronic conditions such as asthma and COPD in ways that deserve separate discussion.

Airway physiology in the hot room

The nose and airways normally warm and humidify the inhaled air, using a little of the body's heat for the purpose; in a hot, humid sauna the atmospheric water vapour does part of that work, so the mucosa dries less and the sense of a "soft" warm breath is a real physical effect, not merely comfort. The physiological literature on bathing records no adverse effect of ordinary sauna air on the healthy respiratory tract: airway resistance does not measurably rise, and the lung's ability to exchange air is unchanged by sessions of normal length. What does change is the respiratory contribution to heat loss: at rest the airways normally dispose of a meaningful share of body heat, but in the hot room that share shrinks, because the inspired air is already near body temperature and carries much water vapour — the whole of the cooling burden then shifts to the skin, with the consequences described under Sweating and Thermoregulation.

Breathing practices also belong to the subject. Slow, calm breathing is part of the sedentary pattern of traditional bathing, and some bathers practise deliberate deep breathing in the cabin as part of relaxation routines (see Breathing in a sauna). Deep breathing in hot, humid air is comfortable for a few minutes — it ventilates the airways with warm saturated air — but it has no documented therapeutic effect, and pushing it too far, like any exertion in the heat, raises heart rate and core load for no benefit. The same caution covers the older idea that the steam of the sauna "cleanses" the lungs: water vapour born in the cabin cannot clean anything, and the substances that would actually leave the body through the lungs — such as carbon dioxide — are unaffected by steam (see Detoxification claims about sauna).

Air quality and the respiratory tract

Respiratory effects are produced as much by what is in the cabin air as by its temperature. Carbon dioxide accumulates in a room where many people breathe for a long time, which encourages drowsiness and is one reason cabins are ventilated (see Carbon dioxide in a sauna and Sauna air change rate). Carbon monoxide from a defective wood stove is the serious danger: it is invisible, odourless and binds the blood's oxygen transport, and a wood-heated cabin is never a place to ignore symptoms of headache or drowsiness (see Carbon monoxide poisoning in a sauna). Volatiles off-gassing from new wood and the particles of wood smoke in old smoky saunas are the further constituents reviewed under Indoor air quality in a sauna; the practical translation for the lungs is the same as for any indoor heat: fresh, moving air, correct ventilation and, for wood-heated cabins, a properly functioning chimney.

Essential oils and scented water are a separate respiratory subject: added to the water thrown on the stones, they volatilise into the air and are inhaled, and while most bathers tolerate them, they are a recognised trigger for people with sensitive airways and asthma (the practical guidance for facilities is assembled in the Essential oils in a sauna article).

Conditions of the respiratory tract

In healthy bathers the respiratory effects of the ordinary session are benign and reversible, and surveys of regular bathing show no adverse association with respiratory complaints. The specific situations with a real literature are treated in their own articles: asthma, COPD, common colds and the question of infections. Two general rules cover the rest of the field. First, a sauna is not a place for a person with an acute respiratory infection — a feverish cold, flu or chest infection — both because heat puts a strain on the body that is trying to fight the infection (see Fever and sauna) and because the cabin is a closed room in which others are exposed (see Infection and sauna). Second, any symptom during bathing that concerns the lungs or breathing — wheezing, tightness, unusual breathlessness, coughing that does not settle — is a reason to leave the room, cool down and, if it persists, seek medical advice (see First aid in a sauna and Cardiopulmonary resuscitation in a sauna for the emergency side of the same rule).

For the healthy majority, the summary is the one the physiology supports: the warm air is comfortable, the respiratory tract is spared the work of warming and humidifying it, the lungs are not harmed by sessions of ordinary length, and the claims of deep steam "cleansing" are folklore rather than medicine (see Sauna research). The further respiratory angle of bathing, including the effects on the heart via the circulation, is covered under Cardiovascular effects of sauna and coronary disease.

See also

• Breathing in a sauna
• Indoor air quality in a sauna
• Carbon monoxide in a sauna
• Asthma and sauna
• COPD and sauna

References

• Kukkonen-Harjula K, Kauppinen K. "Health effects and risks of sauna bathing." International Journal of Circumpolar Health 65(3):195–205, 2006. doi:10.3402/ijch.v65i3.18102
• Laukkanen JA, Laukkanen T, Kunutsor SK. "Cardiovascular and other health benefits of sauna bathing: a review of the evidence." Mayo Clinic Proceedings 93(8):1111–1121, 2018. doi:10.1016/j.mayocp.2018.04.008
• Hussain J, Cohen M. "Clinical effects of regular dry sauna bathing: a systematic review." Evidence-Based Complementary and Alternative Medicine 2018:1857413, 2018. doi:10.1155/2018/1857413
• Tansey EA, Johnson CD. "Recent advances in thermoregulation." Advances in Physiology Education 39(3):139–148, 2015. doi:10.1152/advan.00126.2014