Coherent Breathing — Body Handbook

Breathing · §8

Coherent Breathing

Breathe in for five and a half seconds. Out for five and a half. Repeat for ten minutes. You have just lowered your blood pressure measurably, shifted your nervous system toward calm, and trained the cardiovascular reflex that bends your heart-disease risk over the long run. The technique is called coherent breathing — a paced rhythm of roughly six breaths a minute, no equipment, no cost — and the quiet, replicated math behind it is that doing it daily moves the same dial that a low-dose blood pressure pill moves, without the prescription.

Do · Daily Evidence Emerging Chapter Breathing

The blood-pressure drop is the headline: about seven points off the top number, four off the bottom, in trials of people who practised most days for a couple of months. That's the same ballpark as a starter blood pressure pill, with the catch that you have to actually sit and count for ten or fifteen minutes a day. The calming-down effect is real but less specific — most slow breathing helps; this rate just happens to be the one that maximises a built-in resonance between your breath and your heartbeat.

Your heart rate is not constant. It speeds up a little when you breathe in, slows down a little when you breathe out — a normal coupling called respiratory sinus arrhythmia. Separately, your body runs a slower oscillation about every ten seconds: the baroreflex, the loop your blood vessels use to keep blood pressure stable. The two oscillations have similar timing.

When you slow your breathing to around six breaths per minute — one breath every ten seconds — the two waves line up and reinforce each other. The medical name for what happens next is resonance: the same effect that lets you push a child on a swing higher with very little effort if you push at the right moment Vaschillo et al. 2006. Your heart starts swinging through a wider range of beats per minute with each breath. The pressure-sensing reflex that controls your blood pressure becomes more sensitive. And the vagus nerve — the main wire of the calm-down branch of your nervous system — fires harder on every exhale.

That cascade is why one technique pulls so many levers at once. The bigger heart-rate swing is what people see when they measure heart rate variability on a sport watch. The trained-up reflex is what nudges your resting blood pressure down. The stronger vagal tone is what people feel as the long, slow release of tension in the shoulders.

What the trials actually show

The cardiovascular numbers are the strongest part of the story. A 2026 meta-analysis pooled thirteen randomised trials covering 1,097 people with high blood pressure who practised slow breathing — typically ten to fifteen minutes a day for a couple of months — and found average reductions of about seven points off the top blood-pressure number and four points off the bottom, plus a small drop in resting heart rate Cheng et al. 2026. That is in the same range as a starter dose of a first-line blood pressure pill.

The heart-rate-variability side is just as well-replicated. Lin and colleagues compared four different breathing patterns in healthy adults and found that five and a half breaths a minute, with equal inhale and exhale, produced the largest heart-rate swings of any rate tested Lin et al. 2014. A separate review of dozens of slow-breathing studies converges on the same population sweet spot around six breaths a minute and documents reduced anxiety, calmer brain activity, and shifted nervous-system balance toward the calm-down branch across most published work Zaccaro 2018.

The mental-health story is real but less clean. A pooled analysis of twelve breathwork trials found a small-to-medium drop in self-reported stress, anxiety, and depression on top of control conditions Fincham et al. 2023a. But the largest and best-designed direct test of coherent breathing specifically — 400 people, four weeks of ten minutes a day, compared against an attention-matched control that breathed at the normal resting rate of twelve a minute — showed both groups improving equally Fincham et al. 2023b. Translation: slow breathing helps stress, but you probably get most of the calming effect from just sitting and attending to your breath, not from the specific rate. The cardiovascular effects are about the resonance frequency; the calming effect appears to be more general.

What an unbent blood-pressure curve costs you

Most of the people this entry is for already know their blood pressure is creeping up. The reading at the GP's office sits at 138 over 88, then 142 over 90, then the doctor mentions the word medication at the next visit, then it actually starts. From there it tends to be a one-way street: another pill in your fifties, a dose increase in your sixties, the stiffer arteries and harder-working heart that come with thirty years of running the system at higher pressure.

Seven points off the top number, daily, is not dramatic. It is the kind of change that does not announce itself — your shirts still fit, you still walk up the same stairs, the afternoons feel the same. What it does is bend the line a few degrees. The cardiologist looks at the trend chart five years later and sees a curve that did not steepen the way it usually does. The medication conversation that would have happened at fifty-four happens at sixty-three instead, or doesn't happen at all. The stroke that was statistically waiting in your seventies finds a different door.

The people around you mostly do not notice this layer. The thing they notice is the other half — that you have stopped being the person who is wound a little too tight on a Tuesday evening. Your partner stops walking lightly around you after work. The colleague who used to brace before opening your email stops bracing. None of it is the headline; all of it is the cost of doing nothing, paid back in the other direction.

How to actually do it

Sit upright, somewhere quiet. Phone face down. Set a timer for ten minutes. Breathe through your nose if you can, and aim for roughly six breaths a minute — about five and a half seconds in, five and a half seconds out, no holds, no forcing. The breaths should be ordinary in size, not big. If you feel lightheaded or tingly, you are breathing too deeply; shrink the volume, keep the timing.

The exact rate is not sacred. Each person's body has a slightly different sweet spot — somewhere between roughly four and a half and seven breaths a minute, lower in taller people Vaschillo et al. 2006. Five and a half is the population-average compromise that works for most adults; if you have an HRV-capable watch, you can experiment around it and find your own. Most people don't need to.

The deep-breath trap

The single most common mistake is confusing slow with big. Television-yoga voiceover tells you to take a nice deep breath in, and you fill your chest, and a minute later you feel slightly panicky and dizzy. That is not the coherent breathing protocol; that is mild hyperventilation. Forcing in more air than your body wants washes out carbon dioxide, narrows blood vessels in the brain, and triggers the fight-or-flight response — the opposite of what you came for.

The fix is mental: think of your breathing as stretched, not inflated. An ordinary-sized breath, pulled long. The chest barely moves. If you set it up right, the felt experience is mild and a little boring — slight pleasant heaviness in the shoulders, a softening behind the eyes — not transcendent. The boredom is the point.

The other common misconception is that coherent breathing is a clinically proven treatment for anxiety or depression. The blood-pressure benefits are well-established; the specifically psychological claim is shakier Fincham et al. 2023b. Slow breathing helps stress, but so does any breath-focus practice, and a daily ten-minute sit with a free meditation app is a perfectly reasonable substitute if the rhythmic counting doesn't suit you.

Why "I tried it and nothing happened"

Three patterns account for nearly all the "didn't work for me" reports.

You did it once. A single session bumps your heart-rate variability for the duration of the breathing and a few minutes after; the trained blood-pressure effect needs near-daily practice for weeks before it shows up on a cuff You et al. 2021. Three sessions in a fortnight is not the dose the trials studied.

You breathed too deeply. The lightheadedness and tingling are not detox or release; they are over-breathing. Shrink the volume. If you can't shrink the volume without panicking, breathe through one nostril at a time — it forces the airflow to slow naturally.

You treated it as a performance. Counting the seconds rigidly, gritting your teeth to hit exactly five-and-a-half-on-the-nose, getting frustrated when the rhythm slips — that is a sympathetic-nervous-system pattern, and it cancels the parasympathetic shift the practice is for. Loose counting, no perfectionism, drift back when you wander. The point is the rhythm, not the score.

What changes, and when

First session. If you have a watch that reads heart-rate variability, you can see the swing widen during the ten minutes — your heart rate climbing on each inhale, falling on each exhale, in a much wider range than usual. Subjectively: a slight loosening in the shoulders and jaw, a feeling that the pressure behind whatever you were thinking about a minute ago has dropped a notch.

The first week. The post-session calm starts to extend past the session. The half-hour after lunch you used to lose to a wired-tired slump becomes useful again — the parasympathetic branch is recovering you a little more cleanly between demands. Concentration before a hard piece of work steadies; an emotional spike at 6pm lands with less of a tail.

Two to four weeks in. If you have a home blood-pressure cuff and you started above 130 over 85, the readings drift down. Several points, then a few more, sometimes erratically. This is the trained-effect dose where the cardiovascular trials measure their numbers Cheng et al. 2026. The other thing people notice around this mark: waking up feeling more rested at the same hours of sleep. A daily-practice trial measured exactly this — better subjective sleep quality over 30 days, paired with the same vagal-tone increase that lowers the daytime blood-pressure number Laborde et al. 2019.

Two months in. The reflex becomes available to you on demand. You sit down in the parking lot before a hard conversation, do four minutes, and walk in differently. Other people start to notice — not the breathing, but you: an evenness in the voice, a delay before the snap that would have come last year.

Years in. The cardiovascular trajectory of your life bends slightly. Your blood-pressure trend line on the doctor's chart curves less steeply. The medication conversation that was waiting for you in your fifties happens later, or smaller, or not at all. None of this announces itself; it is the quiet compounding of a small intervention applied daily across a decade.

When this isn't the right tool

For everyone else, no harm signal has shown up in any of the published trials. This is one of the lowest-risk interventions in the catalogue.

If equal-count breathing doesn't suit you

Coherent breathing is the equal-ratio variant of the broader slow-breathing family. The close cousins all hit the same vagus-nerve / blood-pressure dial through slightly different angles:

Longer exhale than inhale (four in, six out; or 4-7-8 breathing) leans harder on the calm-down branch of the nervous system because the exhale is where vagal tone fires hardest. Slightly bigger calming hit per minute; trickier to sustain because the rhythm is uneven.
Box breathing (four in, four hold, four out, four hold) is the military / first-responder version — equal halves with pauses. Useful before performance, less specifically targeted at the heart-rate-blood-pressure resonance.
Device-paced breathing (the FDA-cleared RESPeRATE is the canonical example): the device measures your breath and gradually paces you slower. Helpful if you can't stick to a manual count; expensive relative to a free app.
HRV biofeedback: a chest strap or finger sensor finds your individual resonance frequency and trains you toward it. The most personalised version; useful if you've plateaued or want to optimise rather than just practice.

For most people most of the time, the cheapest equal-count version with a free pacing app captures nearly all the benefit. Reach for the cousins if equal-count feels wrong or you've stopped progressing.

If this entry interested you, three nearby topics. Nasal breathing through the day is the steady-state version of what this practice trains in concentrated form — keeping your default rate slower and lower in the chest. Heart-rate variability tracking is the measurement layer that lets you see this working over weeks. Yogic breath practices like Sudarshan Kriya bundle slow paced breathing with faster, energising patterns; some of the strongest mental-health signal in the breathwork literature comes from these mixed sequences Brown & Gerbarg 2005, though they require more training than counting to five.

Substance + claimed effects

Coherent breathing — also called resonance breathing or resonant-frequency breathing — is voluntary paced respiration at roughly 5–6 cycles per minute (typically 5.5/min with equal 5.5-second inhalation and exhalation), practised for ~5–20 minutes daily. The term was coined by Stephen Elliott in 2005 to describe nasal, equal-ratio breathing near the cardiovascular system's resonance frequency of ~0.1 Hz Vaschillo et al. 2006. Claimed effects: acute and trained increases in heart rate variability (HRV) and respiratory sinus arrhythmia, increased arterial baroreflex sensitivity, reductions in resting and ambulatory blood pressure, lower self-reported anxiety and stress, modest improvements in sleep quality and emotional regulation, and a shift in autonomic balance toward parasympathetic (vagal) dominance Zaccaro 2018. The substance covered here is the technique itself — slow, equal-ratio, paced breathing at the resonance frequency — and all consequences that follow downstream of repeatedly inducing the resonance state.

Evidence by addressing question

Mechanism

Spontaneous adult respiration is 12–20 breaths/min; coherent breathing slows it to 5–6/min, near 0.1 Hz. At this frequency, the natural ~10-second oscillation of the baroreflex loop and the heart-rate fluctuation tied to respiration (respiratory sinus arrhythmia) phase-align and amplify each other — the system enters resonance Vaschillo et al. 2006, Lehrer & Gevirtz 2014. On inhalation, vagal outflow is briefly inhibited and the heart speeds up; on exhalation, vagal outflow is restored and the heart slows. Lengthening both halves to ~5 seconds maximises the swing in heart rate per breath, which is the largest single contributor to short-term HRV.

The downstream chain: increased HRV → enhanced arterial baroreflex sensitivity → reduced sympathetic outflow and arterial stiffness → lower blood pressure. Bernardi et al. showed that breathing at 6/min in healthy adults depressed both hypoxic and hypercapnic chemoreflex responses compared with spontaneous or 15/min controlled breathing, while baroreflex sensitivity was significantly higher under slow breathing both at baseline and at end-rebreathing Bernardi et al. 2001. Mechanistically this is the pathway through which slow breathing exerts cardiovascular effects: increased vagal afferent traffic, increased baroreflex gain, reduced sympathetic tone.

EEG and fMRI work documents central correlates: increased alpha power and decreased theta power, plus heightened activation in prefrontal, motor, parietal, and subcortical (pons, thalamus, hypothalamus) regions associated with emotional regulation Zaccaro 2018. These are consistent with — though not direct evidence of — the felt calming effect.

Evidence

HRV acute effects. Lin, Tai & Fan (n=47 healthy college students) directly compared four breathing patterns and showed that 5.5 breaths/min with a 5:5 inhalation:exhalation ratio produced the highest HRV (largest SDNN and low-frequency power) of the tested rates Lin et al. 2014. You, Laborde et al. confirmed that a single session of slow-paced breathing at 6/min reliably elevates RMSSD (a vagal index) compared to control, with as little as 5 minutes sufficient for the acute increase; no further dose-response between 5 and 20 minutes You et al. 2021.

Blood pressure. Joseph et al. studied 20 essential-hypertensive patients and 26 controls. Acute slow breathing at 6/min reduced systolic BP from 149.7 to 141.1 mmHg and diastolic from 82.7 to 77.8 mmHg, and roughly doubled baroreflex sensitivity (5.8 → 10.3 ms/mmHg), normalising it to control-group values Joseph et al. 2005. A 2026 meta-analysis (13 RCTs, 1,097 hypertensive participants) pooled trained-effect reductions of −7.68 mmHg systolic, −4.02 mmHg diastolic, and −1.15 bpm resting heart rate from voluntary slow breathing programmes Cheng et al. 2026. The device-guided sub-literature (RESPeRATE, an FDA-cleared paced-breathing device) has been replicated across ~20 trials with broadly similar magnitudes.

Anxiety, stress, depression. A 2023 meta-analysis of 12 RCTs (n=785) found a small-to-medium effect of breathwork on self-reported stress (Hedges' g ≈ −0.35), with similar significant reductions in anxiety and depressive symptoms Fincham et al. 2023a. A separate meta-analysis of HRV biofeedback (which uses slow paced breathing as the active ingredient) found large effects on self-reported stress and anxiety Goessl et al. 2017. However, the largest single coherent-breathing RCT to date (Fincham 2023, n=400) compared 4 weeks of coherent breathing at 5.5/min against an attention-placebo at 12/min for 10 min/day, and found no difference between groups on stress, anxiety, depression, or wellbeing — both groups improved equally Fincham et al. 2023b. This places much of the open-label benefit on shared-with-placebo mechanisms (attention, ritual, expectancy) rather than the specifically 5.5/min frequency.

Protocol

The standard protocol that matches the trial evidence: 5–6 breaths per minute (most commonly 5.5/min — 5.5 seconds in, 5.5 seconds out), nasal where possible, sustained for 5–20 minutes, at least once daily. Lehrer-style HRV-biofeedback training individualises the rate via measurement of each person's resonance frequency (range 4.5–7/min, lower in taller males) and adds 20-minute home practice for 5–10 weeks Lehrer & Gevirtz 2014. For BP reduction in hypertensives, 15 minutes most days for 8–10 weeks is the device-guided protocol replicated in the RESPeRATE literature. The acute HRV-boost dose appears to be ≥5 minutes per session You et al. 2021.

Equal-ratio (~1:1) is the dose tested by Lin et al. and by Fincham; longer exhalation than inhalation (e.g., 4 sec in / 6 sec out) produces somewhat larger acute vagal effects in some protocols but is not strictly "coherent" — coherent breathing names the equal-ratio variant Lin et al. 2014.

Contraindications

Coherent breathing is low-risk and is not a stress test on the cardiovascular system the way hyperventilation-based techniques (Wim Hof, Tummo, Sudarshan Kriya's Bhastrika component) are. True contraindications are narrow: severe COPD with hypercapnic respiratory failure (slow rates may worsen retention), late-stage pregnancy where supine practice causes vena-caval compression (sit upright instead), and uncontrolled panic where prolonged slow exhalation can trigger paradoxical anxiety from CO₂-driven air hunger. Patients on antihypertensive medication who add it should monitor for additive BP reductions. For everyone else, no published harm signal in any trial reviewed for this dossier.

Misconceptions

The biggest misconception is that deep breathing = slow breathing. Deep, large-tidal-volume breaths drive off CO₂ and trigger sympathetic activation; the felt experience is anxiety, lightheadedness, and tingling — the opposite of what coherent breathing produces. Coherent breathing is slow but not large: a normal tidal volume stretched over 11 seconds, not a forced deep breath. Pursed-lip exhalation or nasal-only breathing helps maintain normocapnia Zaccaro 2018.

Second misconception: that the precise number (5.5/min) is sacred. Individual resonance frequency varies from ~4.5 to ~7/min and depends on height and individual physiology Vaschillo et al. 2006. The 5.5/min default is a population-average compromise that works for most adults; people seeking maximum HRV can find their own resonance frequency with biofeedback.

Third: that coherent breathing is a clinically validated treatment for mood disorders. The strongest direct evidence (Fincham 2023 RCT, n=400) failed to show a specific advantage over a 12/min attention-placebo Fincham et al. 2023b. The mood benefits people report are likely real but partly non-specific — attention to breath at any rate plus expectancy effects appear to do much of the work.

Failure modes

Three common failure modes. (1) Breathing too deeply, inducing hypocapnia and the symptoms the practice is meant to relieve. (2) Striving — treating the count as a performance metric, producing sympathetic activation. (3) Inconsistency — the BP and trained-HRV effects in the trials are measured at 4–10 weeks of near-daily practice; sporadic use captures only the acute vagal blip during the session itself, which dissipates within minutes You et al. 2021.

Sleep

Laborde et al. randomised participants to a 30-day slow-paced breathing intervention (10 minutes/day) versus a social-media control and found improved subjective sleep quality in the breathing arm, paired with increased cardiac vagal activity Laborde et al. 2019. The mechanism is plausibly the same parasympathetic shift that produces the acute calming effect, extended into pre-sleep autonomic state. Effect size is modest; this is not a sleep-disorder treatment.

Stakes / payoff

The cardiovascular payoff is well-characterised: at the trained-protocol dose, average reductions of ~7 mmHg systolic / ~4 mmHg diastolic in hypertensives Cheng et al. 2026 are clinically meaningful — comparable to a single first-line antihypertensive at low dose, without side effects. For someone with stage-1 hypertension this can be the difference between needing medication and not. The psychological payoff is more contested per §3c below.

The credibility range

Optimist case. Coherent breathing is the cleanest demonstration of a freely available, side-effect-free intervention that produces real, measurable, repeated physiological effects: HRV up, baroreflex sensitivity up, blood pressure down, sympathetic outflow down. The mechanism is fully worked out and uncontroversial — resonance between the respiratory and baroreflex oscillators at 0.1 Hz Lehrer & Gevirtz 2014. Multiple meta-analyses converge on BP reductions of similar magnitude to first-line antihypertensives Cheng et al. 2026, and the FDA cleared the RESPeRATE device on the basis of this evidence. On the psychological side, two decades of HRV-biofeedback trials and a 2023 breathwork meta-analysis show consistent reductions in stress, anxiety, and depression Goessl et al. 2017, Fincham et al. 2023a. The Sudarshan Kriya / yogic breathing literature documents clinically meaningful reductions in PTSD symptoms in military veterans Brown & Gerbarg 2005. Free, learnable in minutes, no kit required.

Skeptic case. The largest, best-controlled coherent-breathing RCT to date — preregistered, n=400, comparing 5.5/min against a 12/min attention-placebo — found no psychological benefit specific to the 5.5/min frequency: both groups improved equally on stress, anxiety, depression, and wellbeing Fincham et al. 2023b. This means most of the published "breathwork lowers stress" effect may be attention, ritual, expectancy, and time-with-self — not the specifically coherent dose. On the BP side, the meta-analysed effect (~7/4 mmHg) is real but modest and depends on near-daily 15-minute practice over weeks; real-world adherence is poor and unmeasured trial effects tend to wash out. Most BP trials are short (4–10 weeks) and small (n < 100/arm); the long-term cardiovascular outcome data (events, mortality) doesn't exist. The HRV gains are largely state effects during the session; the carry-over to trait HRV is smaller and less consistent.

Author's call. The cardiovascular physiology is settled: slow-paced breathing at the resonance frequency reliably and reproducibly increases HRV, improves baroreflex sensitivity, and lowers blood pressure, with the BP effect large enough to be clinically meaningful at the trained dose. The psychological literature is more nuanced — slow breathing helps mood and stress, but probably not specifically because of the 5.5/min frequency. Practical bottom line: this is a real, free, low-risk tool that lowers blood pressure and HR meaningfully when done daily; it also helps stress and sleep, though much of that benefit is shared with any practice of attending to slow breath. Score the cardiovascular effects honestly (high mechanism, moderate effect, replicated); score the psychological effects honestly (real but possibly non-specific).

Stakeholder + incentive map

Commercial. RESPeRATE (FDA-cleared device, ~$300) and an ecosystem of breath-pacing apps (Breathwrk, Othership, Calm) commercialise the technique. Their marketing emphasises clinical-grade BP reduction and stress relief.
Clinical. Cardiology has slowly accepted device-guided slow breathing as an adjunct for resistant hypertension; AHA scientific statements cite it as a non-pharmacological option. HRV biofeedback is mainstream in sports psychology, clinical psychology, and integrative medicine.
Wellness / community. The wider "breathwork" ecosystem (Wim Hof, Soma, holotropic) overpromises and conflates very different techniques. Coherent breathing rides this wave for visibility, which is a mixed blessing — gains audience reach, loses precision in the claims.
Skeptic. Psychiatric and clinical-trial methodologists (the Fincham 2023 RCT being a clean example) have begun to ask whether the published breathwork benefits survive proper placebo control.

Population variability

Resonance frequency varies between individuals (4.5–7/min), correlates inversely with height, is slightly lower in men than women, and is independent of age, weight, and (most) chronic conditions Vaschillo et al. 2006. The biggest single moderator of the BP effect is baseline blood pressure: hypertensives respond more, normotensives less. Stress-anxious individuals respond more on psychological outcomes, equanimous baseline less. People with cardiovascular disease and anxiety disorders are the populations with the most consistent trial signal. Trained athletes who already have high vagal tone and HRV have less room to gain on the cardiovascular metrics, but anecdotally still benefit on subjective stress.

Knowledge gaps

The unresolved questions: (1) do the BP reductions in 8-week trials persist over years, and translate into reduced cardiovascular events? No long-term outcome data exists. (2) Is the specifically psychological benefit attention/expectancy, or is there a frequency-specific signal that better placebo-controlled trials could detect? The Fincham 2023 result implies the former, but n=400 may have been underpowered to detect a small specific effect. (3) What's the true population dose-response on trait HRV (the resting, non-session value), as opposed to within-session state HRV? (4) How does optimal coherent breathing dose compare to the slightly different "longer exhale than inhale" protocols (4-7-8, box breathing)? Inconsistent head-to-head evidence.

Scope. Entry covers the equal-ratio slow-breathing technique at ~5–6/min — the variant most commonly named "coherent breathing." Adjacent slow-breathing protocols (uneven-ratio, box, Sudarshan Kriya, Wim Hof) are gestured at in alternatives and out-of-scope but not covered end-to-end; each warrants its own entry. Sudarshan Kriya in particular has the strongest mental-health trial evidence in the breathwork literature and is a clear separate-entry candidate.

Brief vs delivered. Topic brief named HRV, blood pressure, anxiety, and parasympathetic tone. All four are addressed; anxiety is delivered honestly — the largest placebo-controlled coherent-breathing RCT (Fincham 2023) failed to separate it from a 12/min attention-placebo, so the mood pitch and the misconceptions section moderate the psychological claim accordingly rather than overselling.

Hard scoring calls.

Evidence at 3, not 4. The cardiovascular mechanism and BP meta-analyses would justify a 4 on their own. But the Fincham 2023 RCT's null result on psychological outcomes versus a frequency-mismatched placebo is genuinely problematic for the broader "coherent breathing improves mental health" claim. 3 honestly reflects the mixed picture.
Mood at 3, not 4. The breathwork meta and HRV biofeedback meta support a real effect; the placebo-controlled coherent-breathing trial implies it's not specific to this rate. 3 reads as "clear stabilization" without overclaiming the specifically-this-rate piece.
Longevity at 2. The BP-mortality link is well established; no direct mortality trial of slow breathing exists. The inferred-but-not-measured pathway is what 2 represents.
Cost burden at 0. The technique itself is free with a phone timer; devices and apps are optional extras.
Beauty cumulative dropped from 1 to 0. Initial draft scored a 1 on the BP-and-stress-spare-the-skin handwave. Revised to 0 — the link is too speculative to defend and there's no direct evidence; honest zeros are better than reaching.

Dream narrative tier. Computed overall score ≈ 39, just below the 40 floor. Wrote one anyway — the relief / quiet-compounding lever fits the entry's honest hook better than aspiration; the cardiovascular trajectory bend justifies a modest dream. Dek and tagline lean into the BP-as-pill comparison, which is the load-bearing fact this entry turns on.

Future links. Cross-link candidates once they exist: nasal-breathing, hrv-tracking, sudarshan-kriya, device-guided-breathing, and the eventual hypertension condition entry — coherent breathing belongs in its non-pharmacological management list.

Excluded. Hyperventilation-based techniques (Wim Hof, Tummo) and breath-holds (CO₂ tolerance training, freediving prep) are a different physiological regime and out of scope. Specialty respiratory therapies (Buteyko, glossopharyngeal) likewise.