Knowledge

Sourced guides on how the body stays warm, how patients and clinicians are kept comfortable, how crews work safely in cold and heat, and how warming gear works. Pick the theme closest to your world.

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Technology and Gear David S Technology and Gear David S

PTC self-regulating heaters in wearables, explained

A PTC (positive temperature coefficient) heater is an element whose electrical resistance rises sharply as it warms. As it heats, less current flows, so heat output drops on its own near a designed switching temperature. In wearables, PTC films and inks provide built-in temperature limiting without a separate sensor, but the set point is fixed at manufacture and does not replace good design.

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Technology and Gear David S Technology and Gear David S

How heated vests work: carbon fiber, wire and batteries

A heated vest works like a small, flexible electric blanket. A rechargeable battery pushes current through thin heating elements, usually carbon fiber or metal alloy wire, sewn into panels at the chest, back or collar. The elements resist the current and turn electrical energy into heat. A controller sets the heat level, and the vest's insulation holds that heat near your core.

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Technology and Gear David S Technology and Gear David S

Can you wash a heated vest? Care guide for heated and heat-reflective garments

Most heated vests can be washed, but only after the battery is removed and the connector is secured. Follow the care label first. When it allows machine washing, use a gentle cycle, cold water and mild detergent, then air dry completely before reconnecting power. Never tumble dry, iron, bleach or dry clean a garment with heating elements unless the label allows it.

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Technology and Gear David S Technology and Gear David S

Are heated vests safe? Pacemakers, pregnancy, elderly and more

For most healthy adults, a well-made heated vest used as directed is a low-risk way to stay warm. The real hazards are skin burns from prolonged contact heat and fire from damaged or poorly made lithium batteries. People with reduced sensation, diabetes, implanted cardiac devices, pregnancy, young children and frail older adults need extra caution and a clinician's input.

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Everyday Life and Health David S Everyday Life and Health David S

Heated clothing with diabetes or neuropathy: safety first

Heated clothing can be used by many people with diabetes, but neuropathy changes the risk. When nerves cannot sense heat properly, a heated panel, sock or hand warmer can burn skin without warning. Talk to your clinician first, avoid direct heat on numb areas, especially the feet, use the lowest effective setting, keep fabric between heat and skin, and check your skin every time.

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Everyday Life and Health David S Everyday Life and Health David S

Scleroderma, lupus and cold: living well in cold weather

Cold sensitivity is one of the most common experiences in scleroderma and lupus, mostly through secondary Raynaud's. Nearly 90% of people with scleroderma have Raynaud's symptoms, and it affects up to one-third of people with lupus. Living well in the cold means warming the whole body, protecting fragile skin, avoiding sudden temperature changes and reporting sores early to your care team.

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Everyday Life and Health David S Everyday Life and Health David S

Cold intolerance: thyroid, anemia, chemotherapy and other causes

Cold intolerance is an abnormal sensitivity to cold temperatures. MedlinePlus lists its main causes as anemia, hypothyroidism, blood vessel problems such as Raynaud's, anorexia nervosa, problems with the brain's temperature center and chronic severe illness. Some cancer drugs, notably oxaliplatin, also make people very sensitive to cold. A clinician can usually narrow the cause with an exam and blood tests.

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Everyday Life and Health David S Everyday Life and Health David S

Why keeping your core warm helps cold hands

Your body gives up hand warmth first when it senses cold. To protect core temperature, the hypothalamus narrows blood vessels in the skin, and fingers cool quickly. Keeping the torso warm reduces that signal, so the body has less reason to hold warm blood back from the hands. That is why Raynaud's organizations advise warming the whole body, especially the core, not only the fingers.

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Everyday Life and Health David S Everyday Life and Health David S

Raynaud's vs chilblains, acrocyanosis and other look-alikes

Raynaud's causes short episodes in which fingers or toes turn white, then blue, then red. Chilblains are itchy red or purple patches that appear hours after cold. Acrocyanosis is persistent, usually painless blue discoloration. Erythromelalgia is red, burning skin triggered by warmth. Cold urticaria causes itchy welts within minutes. Buerger's disease is a tobacco-linked artery disease that can mimic Raynaud's.

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Everyday Life and Health David S Everyday Life and Health David S

Primary vs secondary Raynaud's: what the difference means

Primary Raynaud's happens on its own, usually starts in the teens or twenties, and is generally mild. Secondary Raynaud's is caused by another condition, medicine or exposure, often begins later in adulthood, and is more likely to cause finger sores. Clinicians tell them apart with a history, an exam, a look at the nailfold capillaries and blood tests such as ANA.

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Everyday Life and Health David S Everyday Life and Health David S

Cold hands and feet: causes, patterns and practical fixes

Cold hands and feet are usually the body's normal way of protecting core temperature by narrowing blood vessels in the skin. The pattern tells you more than the coldness itself: episodes of white or blue fingers suggest Raynaud's, one-sided coldness can point to blocked arteries, and numbness with cold feet may reflect nerve damage. Most people improve by warming the whole body.

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Everyday Life and Health David S Everyday Life and Health David S

Why am I always cold? Common causes and when to see a doctor

Feeling cold all the time is often a normal difference in how your body conserves heat, shaped by body size, activity and clothing. Persistent or worsening cold can also come from hypothyroidism, anemia, very low body weight, Raynaud's phenomenon or other blood vessel problems. If cold intolerance is long-term, extreme or comes with fatigue or other new symptoms, see a clinician.

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Healthcare David S Healthcare David S

Core temperature monitoring: methods and accuracy

Core temperature is best measured where blood from the body's core is sampled directly or closely: the pulmonary artery, distal esophagus, nasopharynx or tympanic membrane. Bladder, oral, axillary and zero-heat-flux forehead sensors are practical near-core options with known limits. Infrared temporal and ear scanners are not accurate enough to guide perioperative care, and NICE advises against indirect estimates.

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Healthcare David S Healthcare David S

Operating room temperature and humidity standards (ASHRAE 170 and AORN)

In the US, operating room design conditions come from ANSI/ASHRAE/ASHE Standard 170, which sets a temperature range of 68°F to 75°F (20°C to 24°C) and relative humidity of 20 to 60 percent. CMS lowered its minimum humidity from 35 to 20 percent in 2013. The UK's NICE guideline adds a patient-focused rule: at least 21°C (69.8°F) while the patient is exposed.

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Healthcare David S Healthcare David S

Passive vs active warming: when each is used

Passive warming reduces heat loss by insulating the patient with blankets, heat-reflective layers or clothing, but relies on the body's own heat. Active warming adds external heat through devices such as forced-air, resistive or circulating-water systems. In surgery, anesthesia blunts the body's heat production and defenses, so guidelines favor active warming for most anesthetized patients and use passive measures as support.

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Healthcare David S Healthcare David S

Forced-air vs conductive warming: what the evidence shows

Both forced-air and conductive warming reduce perioperative hypothermia, and neither eliminates it. Forced air has the larger evidence base and is NICE's default; some trials find it slightly more effective, while others find conductive warming equivalent or better, especially when combined with prewarming. Timing, coverage and consistent use often matter more than the choice of technology.

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