Respiratory Rate

What Respiratory Rate Measures

Breathing is set by a cluster of neurons in the medulla oblongata, the lower part of the brainstem, that generates the basic rhythm and adjusts it using feedback from chemoreceptors that monitor oxygen, carbon dioxide, and pH in the blood.^[1] Carbon dioxide crosses easily into the fluid around the brain and shifts its acidity, which is the main signal that tells the breathing center to speed up or slow down.^[1] Because that feedback loop runs constantly, respiratory rate isn't a fixed number. It moves with activity, temperature, altitude, and hormonal state, among other things.

How It's Measured

A resting respiratory rate reading traditionally comes from counting chest rises over a set interval while someone is calm and still. Consumer wearables estimate it continuously overnight instead, using the same wrist sensors that already track heart rate: an optical pulse sensor that reads blood-volume changes, combined with an accelerometer that picks up the chest's subtle movement with each breath. A 2023 validation study checked a consumer smartwatch's overnight respiratory rate readings against nasal airflow sensors during in-lab sleep studies in 195 people and found the device's nightly average landed within about one breath per minute of the reference reading in people without severe sleep-disordered breathing.^[2]

Why People Track Respiratory Rate

Respiratory rate isn't the first metric people think to chart alongside their cycle, but it sits in the same family as resting heart rate and basal body temperature: a biometric that shifts with hormonal state and is now easy to capture passively overnight. Progesterone, the hormone that rises after ovulation, acts as a respiratory stimulant, which is why researchers have looked at breathing across the menstrual cycle at all.

The pattern in respiratory rate specifically is smaller and less consistent than the pattern in metrics like temperature, and the research section below explains why.

How Go Go Gaia Tracks Respiratory Rate

Go Go Gaia pulls respiratory rate automatically from Apple HealthKit, syncing whatever your Apple Watch or connected wearable already records overnight without any manual logging. The app charts it as a trend line next to your cycle phase, resting heart rate, and HRV, so you can see how it moves through your cycle instead of reading it as one isolated nightly number.

What the Research Shows

A 2006 study of healthy women found resting minute ventilation, the total volume of air moved per minute, ran about a liter higher in the luteal phase than the follicular phase, alongside higher progesterone and estradiol. The same study found no difference between phases in how sensitive the body's carbon dioxide chemoreflex was, so the higher ventilation didn't come from the breathing center reacting more strongly to CO2.^[3]

Researchers still haven't settled on exactly how progesterone raises ventilation. A 2008 review of sex hormones and breathing control concluded that progesterone consistently stimulates ventilation, especially alongside estrogen, but that the mechanism and the site in the body where it acts remain unresolved.^[4]

The largest analysis to date, a 2025 systematic review and meta-analysis pooling 35 studies and 64 datasets, confirmed higher resting minute ventilation in the luteal phase but found only a minimal menstrual cycle effect on respiratory rate itself. It also found that the size of the progesterone change predicted the ventilation difference during light exercise, but not at rest.^[5] That distinction between rate and volume is the honest summary: breathing tends to get somewhat deeper in the luteal phase, but breathing faster is a much less reliable part of that pattern.

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

Does respiratory rate change across the menstrual cycle?

The evidence is mixed depending on what's measured. Minute ventilation, the total volume of air moved per minute, tends to run higher in the luteal phase, the second half of the cycle after ovulation. Respiratory rate itself, the count of breaths per minute, shows a much smaller and less consistent pattern, and the largest analysis to date found only a minimal cycle-phase effect on rate specifically.

What's the difference between respiratory rate and minute ventilation?

Respiratory rate is how many breaths you take per minute. Minute ventilation is the total volume of air you move per minute, which is rate multiplied by the depth of each breath. You can raise minute ventilation by breathing more often, more deeply, or both, which is part of why the two don't always move together across the menstrual cycle.

Why does Go Go Gaia track respiratory rate alongside cycle data?

Go Go Gaia pulls respiratory rate automatically from Apple HealthKit and charts it as a trend next to cycle phase, resting heart rate, and HRV. Even though the cycle-phase pattern in respiratory rate is smaller than in other biometrics, seeing it in context with the rest of your data still gives a fuller picture over time.