A long flight can sometimes leave you feeling that your heart is beating differently, especially when you stand up after several hours of sitting. You may notice a faster heartbeat, mild breathlessness, fatigue or a feeling of heaviness. For most healthy people, these changes are temporary and are related to the conditions inside an aircraft rather than a direct problem with the heart. Cabin pressure is lower, while sitting for long periods, limited movement and not drinking enough water can also affect circulation.

Speaking to NDTV, Dr Ajit Menon, Director of the Department of Cardiology, Sir H. N. Reliance Foundation Hospital, said that as elevation increases, atmospheric pressure falls. Although oxygen still makes up about 21% of the air, the lower pressure means fewer oxygen molecules enter the lungs with each breath. "Due to the fact that air pressure is reduced, the molecules of air are further away from each other, thus the amount of oxygen taken into the lungs with every breath is smaller than on sea level. The air pressure can become so low at extreme elevations that oxygen becomes reduced by half, said Dr Menon.

During a flight, these changes are much less pronounced than at very high mountain altitudes, but they can still lead to temporary changes in how you feel.

How Does Cabin Pressure Affect The Heart?

Commercial aircraft cabins are pressurised, but cabin pressure is generally lower than the pressure at sea level. This means the body has slightly less oxygen available with each breath. The body has mechanisms to compensate. Sensors called carotid body chemoreceptors detect changes in oxygen levels and signal the brain to increase breathing. "This results in an increased breathing rate of forty to sixty percent to inhale more air. Since there is less oxygen taken into the blood, the amount of oxygen in the tissues reduces."

For a healthy passenger, these changes are usually well tolerated. However, people with certain heart or lung conditions may be more sensitive to reduced oxygen availability. People with serious cardiovascular disease should discuss air travel with their doctor, particularly before long-haul flights.

Can Dehydration Make Your Heart Beat Faster?

Dehydration is another factor that can make you feel different after a long flight. People may drink less water while travelling, and the dry cabin environment can lead to fluid loss. When the body does not have enough fluid, blood volume can fall. The heart may then beat faster to maintain adequate blood circulation. This can cause palpitations, weakness, dizziness or fatigue, particularly when getting up after sitting for several hours.

Staying adequately hydrated during a long flight can therefore help.

What Does Sitting For Hours Do To Circulation?

Long periods of immobility can affect blood circulation, particularly in the legs. When the leg muscles are inactive, they do not help push blood back towards the heart as effectively. This can result in swollen ankles, heaviness in the legs or discomfort after a long journey. More importantly, prolonged immobility can increase the risk of developing a blood clot in a deep vein, which is also known as deep vein thrombosis (DVT).

If part of a clot breaks away and travels to the lungs, it can cause a pulmonary embolism. Warning signs include sudden breathlessness, chest pain, coughing up blood, fainting or a very fast heartbeat. These symptoms require urgent medical attention.

Is This The Same As Altitude Sickness?

Not usually because altitude sickness is associated with travelling to much higher elevations without giving the body enough time to acclimatise.

At high altitudes, reduced atmospheric pressure means less oxygen reaches the blood and tissues. The body initially responds by increasing breathing. Over several days, acclimatisation involves changes such as increased red blood cell production.

Acute mountain sickness can cause headache, dizziness, vomiting, exhaustion and difficulty sleeping. In severe cases, it can progress to high-altitude cerebral edema (HACE), involving brain swelling, or high-altitude pulmonary edema (HAPE), in which fluid accumulates in the lungs. These conditions are associated with high-altitude travel rather than an ordinary commercial flight.

How Can You Protect Your Heart During A Long Flight?

A few simple measures can support circulation during long journeys:

  • Keep moving: Get up periodically and walk around the cabin when it is safe to do so.
  • Move your legs: When seated, flex your ankles and move your feet regularly.
  • Drink enough water: Avoid being dehydrated during the journey.
  • Limit alcohol: Alcohol can contribute to dehydration and prolonged sleep or inactivity.
  • Follow medical advice: People with heart, lung or circulation problems should ask their doctor whether any additional precautions are needed.
  • Know the warning signs: Persistent chest pain, severe breathlessness, fainting or a sudden racing heartbeat should not be dismissed as normal post-flight symptoms.

For mountain travel, prevention is different. Gradual ascent is important, particularly above 2,500 metres, because the body needs time to acclimatise. If you develop altitude sickness, descent is the main treatment. Supplemental oxygen and medicines may be used in certain situations under medical guidance.

For most people, feeling slightly tired, dehydrated or noticing a temporary change in heartbeat after a long flight is not necessarily a sign of heart damage. However, symptoms that are severe, persistent or accompanied by chest pain or significant breathing difficulty should be checked by a doctor.

Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.