Cat Sleeping Respiratory Rate: The HCM Early Warning Every At-Risk-Breed Owner Should Run

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. By some estimates, 15% of all cats have it; in some at-risk breeds the prevalence is much higher. Most cats with HCM appear asymptomatic for years. The disease progresses silently, and the first time many owners learn their cat has it is when the cat presents in respiratory crisis at the ER — often too late for the best outcomes.

One simple measurement, run weekly at home, dramatically changes that picture. The sleeping respiratory rate (SRR) is the gold-standard early warning for HCM progression — established in feline cardiology literature for over a decade, validated in clinical practice, and now built into modern cat-care apps as a one-tap home screen.

Why SRR works as an early warning

HCM thickens the wall of the left ventricle, the chamber that pumps oxygenated blood out to the body. As the muscle thickens, the chamber becomes stiffer — it can't relax fully between beats, which means it can't fill with blood efficiently. Blood backs up into the left atrium, then into the pulmonary veins, and eventually into the lung tissue itself. This is pulmonary oedema — fluid in the lungs.

The earliest measurable consequence of pulmonary oedema is a small but persistent increase in respiratory rate. The cat doesn't necessarily look sick yet. Their behaviour might be unchanged. But the lungs are working harder to oxygenate the blood, so the body breathes a little faster, even at rest. SRR catches this before clinical signs appear.

Cardiology research has consistently established that SRR rising above 30 breaths per minute in a sleeping cat correlates with progression of underlying heart disease. Cats whose owners noticed and acted on a rising SRR get earlier vet workups, earlier medication, and meaningfully better outcomes than cats whose owners first notice when the cat is gasping in the corner.

How to measure SRR correctly

The measurement is simple but the conditions matter.

Wait for true rest or sleep

SRR specifically means the cat is sleeping or fully resting. Not actively grooming, not having just played, not in the middle of a conversation with you. The rate during activity is naturally higher and meaningless for cardiac monitoring.

Count chest rises, not full cycles

One inhale + one exhale = ONE breath. Watch the chest. Each visible rise (or rise + fall) counts as one. Don't count the rise AND the fall separately — that doubles your count.

30 seconds × 2

Count for 30 seconds, multiply by 2 to get breaths per minute. Counting for a full minute is also fine but unnecessary; 30 seconds is enough to get an accurate rate.

Interpret the result

• Normal: 16-30 breaths/minute.
• Borderline: 30-35. Could be a one-off; recheck the next day at a similar time.
• Elevated: 35-45. Vet call within 24-48 hours. Ask about an echocardiogram if not already done.
• High: 45+. Especially with any other symptom (lethargy, decreased appetite, gum colour change, open-mouth breathing) — ER tonight.

Sustained pattern matters more than a single reading. A reading of 32 once might be the cat dreaming or warm. A pattern of 35-40 across multiple measurements over a week is the actionable signal.

Which cats need this most

Eight breeds have well-documented elevated HCM prevalence — owners of these cats should be measuring SRR weekly from at least age 2.

• Maine Coon — the genetic mutation (MYBPC3 A31P) is well-characterised; testing is widely available. Even cats that test negative for the known mutation can develop HCM, so the screening is still important.
• Ragdoll — separate Ragdoll-specific genetic mutation (MYBPC3 R820W).
• Sphynx — high observed prevalence; genetic testing emerging.
• Persian — long-recognised familial pattern.
• British Shorthair — elevated population rate.
• Bengal — emerging pattern in breed-specific reporting.
• Norwegian Forest Cat — included on most cardiology screening lists.
• Siberian — included on most cardiology screening lists.

Mixed-breed cats and other breeds can develop HCM too, but at lower population rates. For these cats, SRR baseline checks are still useful — especially after age 7 — but the cost-benefit ratio of weekly measurements is highest in the at-risk breeds.

What to do when the SRR is elevated

The decision tree:

• SRR 30-35, no other symptoms: recheck the next day at a similar time of day. If still elevated, mention to your vet at the next routine visit. If your cat has never had a cardiology workup and is in an at-risk breed, request an echocardiogram.
• SRR 35-45, no other symptoms: book a vet appointment within 1-2 weeks. Ask about an echocardiogram. The cardiologist will look for left ventricular wall thickening and assess the cat's overall cardiac function.
• SRR 45+ OR any symptoms: same-day vet visit. If after hours, ER. Cats in heart failure decompensate fast — what looks "manageable" at 8 PM can be a crisis at 11 PM.

If HCM is diagnosed via echocardiogram, the cardiologist will likely prescribe medication. SRR then becomes the at-home monitoring tool for medication efficacy: stable SRR over weeks = meds are working; rising SRR = time to titrate.

What an elevated SRR is NOT necessarily

HCM is the highest-priority differential, but not the only cause of elevated respiratory rate in cats. Other causes worth knowing:

• Pleural effusion (fluid around the lungs, not in them) — can cause similar elevated breathing. Workup distinguishes via chest X-ray.
• Asthma — feline asthma is common and treatable. Often has audible wheeze and intermittent presentation; SRR measurement is less useful here than during active respiratory distress.
• Anaemia — body breathes faster to compensate for low oxygen-carrying capacity. Distinguishes via gum colour (see the gum colour guide) and bloodwork.
• Pain — significant pain can elevate respiratory rate. Score a Feline Grimace Scale alongside SRR if pain is suspected.
• Stress — a recent vet visit, new household member, or moved furniture can transiently elevate SRR. Recheck after the stressor passes.

The vet workup distinguishes among these. From the home-monitoring perspective, the action is the same: persistently elevated SRR = vet call.

What this changes day-to-day

Owning an at-risk-breed cat without measuring SRR is leaving a major early-warning system unread. Owning the same cat with a weekly SRR routine catches HCM progression weeks or months earlier than waiting for symptoms — and "weeks earlier" is the difference between starting medication during stable disease and meeting your vet at the ER for a cat in respiratory crisis.

30 seconds of counting, once a week. The single highest-leverage at-home cardiac monitoring any cat owner can do.

Frequently asked questions

What is sleeping respiratory rate (SRR) in cats?

The number of breaths per minute a cat takes while sleeping or fully resting. Each chest rise + fall = ONE breath. Normal sleeping range is 16-30 breaths per minute. Above 30 sustained while asleep is a strong flag for fluid accumulating in the lungs (pulmonary oedema) — the most common acute presentation of advanced hypertrophic cardiomyopathy (HCM). The measurement is easy: count chest rises for 30 seconds, multiply by 2.

Why is SRR specifically the gold-standard early warning for HCM?

HCM thickens the heart muscle, eventually impairing the heart's ability to relax and fill properly. As the disease progresses, blood pressure backs up into the lungs, causing pulmonary oedema. The earliest measurable sign of this fluid accumulation — often weeks before the cat shows visible distress — is an elevated resting respiratory rate. Cardiology research consistently shows SRR rises before clinical signs in cats with progressing HCM, giving owners (and vets) lead time to intervene with medication.

Which cat breeds are at highest HCM risk?

Eight breeds with documented elevated HCM prevalence: Maine Coon (well-characterised genetic mutation), Ragdoll (separate genetic mutation), Sphynx, Persian, British Shorthair, Bengal, Norwegian Forest Cat, and Siberian. Mixed-breed cats and other breeds CAN develop HCM too, but at lower population rates. If your cat is one of the at-risk breeds — even if asymptomatic — running a baseline SRR weekly from age 2 onward is the single highest-leverage thing you can do for early detection.

My cat's SRR is 35. Is that an emergency tonight?

It's a flag worth a vet call within 24-48 hours, not necessarily an ER tonight — UNLESS combined with open-mouth breathing, lethargy, gum colour change, or visible respiratory distress, which are all immediate ER. SRR 30-45 alone usually means the disease is progressing and warrants an echocardiogram + possible medication adjustment. SRR 50+ alone OR any combination of SRR + symptoms = ER tonight. The 30 threshold is conservative; a single reading at 31 is less concerning than a sustained pattern of 35-40 over multiple measurements.

How often should I measure SRR?

For at-risk-breed cats with no known HCM diagnosis: weekly baseline measurements starting around age 2. For cats with diagnosed HCM on medication: as directed by the cardiologist, typically daily during titration and weekly during stable phases. For all cats: any time you notice changed breathing, increased rest, or a behaviour change suggesting heart-related decline.