How is Blood flow related to lung function during Exercise?

How is blood flow related to lung function during exercise?

This is a question I get asked quite often, and one that we have been studying for over ten years. We also cover in the new book  Fitness As A Way Of Life.

I’ve seen it claimed that you “breathe harder” to get more oxygen into your body during exercise, and when people do this, they get more oxygen into their bodies. Although this is true, breathing harder doesn’t increase the amount of blood sent to the exercising muscles.

If you breathe harder during exercise, it’s because your body is trying to match the airflow coming into what is being expelled out by the contracting muscles. If you breathe too complicated/fast, your body can’t keep up and “blow-off” CO2, so there is less O2 in your blood. But this doesn’t happen when you are fit because with more muscular muscle contractions come faster respiration rates which mean there isn’t any time for elevated levels of CO2 to build up.

It takes longer for blood flow through vessels (i.e., arteries) to be matched by blood flow back to the heart (i.e., veins).

This means that if you increase your flow through a vessel by increasing blood pressure, there is a short delay before flow into that vessel reduces, and vice versa. If you decrease blood pressure, there will be a short delay before flow out of that vessel increases.

For this reason, it takes longer for blood flow through vessels (i.e., arteries) to be matched by blood flow back to the heart (i.e., veins). In less refined terms, even with increased breathing during exercise, more O2 gets sent to your muscles because vascular resistance decreases as you become fitter, which means increased amounts of O2 rich-blood reach those working muscles.

In addition, there is more O2 in your blood because “pumping” the working muscles increases the O2 content of the blood (i.e., you do some work on your strengths, but they also do work on you), and this increase in blood flow accounts for most of the change in how much O2 makes its way to those exercising muscles.

So it’s not just about breathing harder, or even breathing harder faster, during exercise – it’s about living hard/fast enough so that there isn’t any time for increased CO2 levels to reach dangerous levels before new air comes into the lungs. This ensures that your body can deliver ample amounts of oxygen rich-blood to active muscles without allowing too much time for CO2 levels to become elevated to dangerous levels.

We now have an online calculator that allows you to estimate the effect of exercise on your arterial blood gases, cardiovascular system, and lung function; visit our website for more information.

How does blood flow affect the lungs?

And how does this depend on whether you are exercising or at rest?

There isn’t much known about blood flow in the lungs because it’s difficult to measure. It is estimated that there are about 60 ml of blood per minute flowing through each lung, but a lot of this volume goes outside the capillaries and into the air spaces within your lungs.

So for most intents and purposes, we can say that, on average, very little blood flows through your alveoli during exercise, with only around 2-3% of cardiac output going to capillary beds in your lungs.

In healthy individuals, what is essential is matching blood flow out of the lungs (capillaries) with flow back towards the heart (venules) so that venous blood returning to the heart doesn’t get “backed up” and form deleterious blood pools or edema in your lungs.

This is achieved with increases/decreases in breathing rate during exercise, which keeps pulmonary capillary pressures from becoming too high, even when exercising at a very high intensity with large volumes of gas moving through the alveoli per minute.

What does this mean?

During exercise, healthy lung function ensures that O2 rich-blood can be delivered to active muscles without allowing too much time for CO2 levels to become elevated to dangerous levels.

We don’t need as much ventilation during rest because of a reduction in metabolism and because the pressure inside the lungs becomes less harmful as you relax. Your breathing slows down, allowing air into the lungs.

This happens because blood flow through the lungs reduces. The “muscles” surrounding alveoli (called inter-alveolar muscles) help keep airways open relax, so that lung volume increases, allowing fresh air in.

What are the dangers of being physically active with asthma?

Whether or not you “over-breathe” during exercise depends on your lung function and how well it is controlled. For example, some people who have good lung function and only mild (reversible) airway obstruction may find that they can get by with low levels of ventilation, while others who have both severe (irreversible) airflow limitation and poor control over their asthmatic symptoms might require very high rates of breathing to maintain adequate gas exchange (i.e., oxygen saturation).

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