Lying Down Changes the Breath

Lying Down Changes the Breath

Some people are fine during the day and feel tight once they lie down. An extra pillow helps; turning onto one side eases it. Tests are usually taken sitting, and at that point nothing much is said.

I read that mismatch as a difference posture makes. The breath standing and the breath lying down are not the same breath.

Lying Down, the Abdomen Pushes the Diaphragm Upward

Standing, the abdominal organs settle downward with gravity. Lying down, that weight bears toward the back and upward instead. The abdominal contents then push the diaphragm upward.

When the diaphragm is pushed up, the space on the chest side shrinks by that much. Even after breathing all the way out, some air remains in the lungs; that remaining share is called functional residual capacity. It is greatest standing, and decreases lying down.

When the remaining air decreases, the small chambers collapse more readily, and there is more to reopen on the next breath in. That is part of why the breath feels shallow lying down.

The Movement of Blood Is Laid Over It

Posture changes more than the air.

Blood and water that stayed low during the day return upward when you lie down. More blood is held within the chest. The lungs now have one more party to share the room with.

So tightness when lying down usually has more than one cause. The share from the diaphragm being pushed up and the share from blood returning to the chest act together. Raising the pillow helps because both of those partly reverse.

Tests Are Usually Taken Sitting

Lung function tests are generally taken sitting or standing, because matching the posture is what makes values comparable. And that posture also happens to favour the lungs.

The discomfort, though, comes lying down. That is how "the lung test is normal, and I feel tight when I lie down" arises. Neither is the test wrong nor the patient oversensitive. The posture measured and the posture that troubles you are simply different.

I Ask Which Posture

In the consulting room, along with when it happens, I ask in which posture: only flat on the back, easier on one side, how many pillows make it comfortable, whether you wake at night having to sit up.

And what posture changed, posture has some room to change back: raising the upper body a little, lying on one side, not weighing the abdomen down before bed. Rather than straining for bigger breaths, making room for the diaphragm to descend often comes first.

That said, if lying down leaves you so breathless that you can only sleep sitting up, if you wake at night unable to breathe, or if the legs swell along with it — that is not a story about posture alone. Having the heart and lungs examined comes first.

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Breathing is not always done under the same conditions. Standing and lying down, the body does the same work in a different situation.

If you are fine by day and tight once you lie down, it is not an illness that flares at night. It may be the body reporting, plainly, the conditions that posture changed.

Related Reading

• The Organs in Your Abdomen Ride Up and Down with Your Breath — the diaphragm and what lies below it
• Tests Look at the Body of That Moment — matched conditions and the body in daily life

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Sources

• Functional residual capacity is greatest upright and decreases when supine, closing the airways of some lung regions — StatPearls, Physiology, Functional Residual Capacity, 2023
• In the supine position, upward displacement of the abdominal contents into the diaphragm decreases functional residual capacity and respiratory compliance — StatPearls, Anatomy, Patient Positioning, 2023

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)