Why is it harder to breathe when its hot?

Five Pulmonologists Run Miami’s Half Marathon

Every year, running the Miami half marathon gets me 364 days to brag about it before having to run another. This year, Mami’s infamous heat and humidity came out for race day.

Each year, I experience significant breathlessness running and think of my respiratory patients who feel this constantly. And each year it seems my marathon time gets longer. Something I chalk up to heat and humidity instead of age.

This makes me think about a study my friend Michael Campos did where he compared the exercise capacity of patients with COPD inside and outside. He found the heat and humidity markedly reduced COPD patient’s exercise tolerance when he compared their ability to exercise inside with air conditioning. So, for patients with COPD and other respiratory limitations, the brutal heat and humidity of Miami further detracts from their functional capabilities adding insult to injury.

Why? Its complicated and not completely understood despite being widely experienced by people with respiratory problems.

Breathing requires body effort. Respiratory patient’s disease often requires more effort to get sufficient oxygen and achieve appropriate ventilation. At higher temperatures, the body’s energy demands to breathe and maintain normal temperatures increase. Increased effort requires more oxygen for muscles to function and more ventilation to expel the waste product gas (carbon dioxide) from working muscles. Therefore, heat causes respiratory patients to work harder just to breathe and quickly exhausts these people.

Respiratory patient’s increased need for oxygen, makes them breathe harder and faster. This rapid breathing further complicates patients with asthma and COPD. Patients with asthma and COPD experience airflow obstruction that make breathing out take longer. When they breathe too fast, they cant exhale all of their air before they need to take in a new breath. This traps increasing amounts of air in their lungs to the point where they run out of room to take in a full breath.

When asked, they usually say they can’t get in enough air and are horribly short of breath.

What to do it this happens?

As a general rule, one stops exercising and specific breathing exercises can help. Inhaling through the nose helps by humidifying the air since dry air irritates lungs. Then breathing out slowly through pursed lips helps unload the trapped air. When someone purses their lips, they create a small amount of back pressure that stent the airways open to allow better air flow.

Breathing like this can really help.

I’m just hoping the marathon is on a cooler day next year.