Sleep medicine · Patient guide
TOSCA sleep study, home sleep study with continuous transcutaneous CO₂ monitoring.
A TOSCA sleep study is a home sleep test that adds continuous transcutaneous CO₂ monitoring to oxygen saturation — essential for detecting nocturnal hypoventilation, obesity hypoventilation and neuromuscular respiratory failure.
Key facts
What a TOSCA sleep study is, in six lines.
The essentials — what it measures, who runs it, and where it sits alongside a standard sleep study.
- 01
Definition
A home sleep study that measures oxygen saturation together with continuous transcutaneous carbon dioxide (TcCO₂) — a level of detail a standard oximetry study cannot provide.
- 02
Consultant sleep physician-led
Set up, interpreted and reported by a consultant respiratory or sleep physician — never a technician alone.
- 03
Combines SpO₂ + TcCO₂
Two channels captured overnight — pulse oximetry and transcutaneous CO₂ — the pairing that reveals hypoventilation.
- 04
Detects hypoventilation missed by pulse oximetry
A normal SpO₂ trace can hide rising CO₂. TOSCA measures the CO₂ directly, so the diagnosis isn’t missed.
- 05
Foundation for NIV titration
The reference test used to decide whether non-invasive ventilation is needed, and to titrate settings safely.
- 06
Complements PSG and Nox T3
Sits alongside full polysomnography and Nox T3 studies — chosen when the clinical question is ventilation, not just apnoea.
How the diagnosis is made
From consultation to report — the seven steps, in order.
A consultant sleep physician leads the whole pathway — no algorithm-only reports.
- 01
Before
Sleep consultation
A consultant sleep physician takes the history — symptoms, red flags, neuromuscular or respiratory disease, prior sleep studies.
- 02
Before
Home sensor fitting
The TOSCA earlobe sensor and pulse oximeter are fitted at home or in clinic — no hospital stay required.
- 03
The study
Overnight recording
You sleep in your own bed. The device records continuously through the night with no intervention needed.
- 04
The study
TcCO₂ + SpO₂ captured
Two continuous traces — transcutaneous CO₂ and oxygen saturation — form the core of the diagnostic dataset.
- 05
After
Analysis by sleep physician
The consultant reviews the traces manually — not an algorithm alone — looking at trend, peaks and time above threshold.
- 06
After
Structured report
A written report with clear findings, diagnosis and recommendation — written for both you and your referring team.
- 07
After
NIV / CPAP titration
If ventilatory support is indicated, the same team arranges NIV or CPAP titration and ongoing follow-up.
What it shows
When a TOSCA study is the right test.
The clinical questions TOSCA answers — and the red-flag finding that changes the whole plan.
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Nocturnal hypoventilation
Rising CO₂ overnight — the earliest and often the only signal, invisible to standard oximetry.
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Obesity hypoventilation syndrome
Daytime and nocturnal hypercapnia in the context of obesity — a treatable but under-diagnosed condition.
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Neuromuscular respiratory failure
Weak respiratory muscles from MND, DMD or post-polio — TOSCA quantifies the ventilatory failure.
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COPD nocturnal hypercapnia
Identifies patients with COPD who hypoventilate overnight and benefit from home NIV.
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Central hypoventilation
Congenital or adult-onset central drive failure — the diagnosis rests on continuous CO₂ measurement.
-
OSA with hypoventilation
Obstructive sleep apnoea complicated by hypoventilation — a different treatment pathway from OSA alone.
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CPAP failure workup
When symptoms persist on CPAP, TOSCA reveals whether unrecognised hypoventilation is driving the failure.
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Red flag: severe hypercapnia — urgent NIV
A severely raised nocturnal CO₂ is not a routine finding — it triggers urgent non-invasive ventilation review.
Treatment options
What TOSCA findings unlock in treatment.
The interventions a positive TOSCA study makes possible — from NIV titration to disease-modifying pathways.
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NIV / BiPAP titration
Bi-level non-invasive ventilation — the mainstay treatment for nocturnal hypoventilation, titrated against repeat TOSCA.
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CPAP with backup rate
For selected patients where a fixed positive pressure with a mandatory rate corrects the ventilation problem.
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Adaptive servo-ventilation (ASV)
A specific NIV mode reserved for particular central patterns — decided by the consultant sleep team.
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Weight loss + bariatric pathway
For obesity hypoventilation, medically supervised weight loss or bariatric surgery is disease-modifying.
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Diaphragm pacing
A neuro-stimulator option for selected central hypoventilation and high spinal-cord injury patients.
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Home ventilation programme
For long-term ventilatory failure — home NIV with structured follow-up and equipment support.
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Sleep follow-up
Repeat TOSCA at three to six months confirms the treatment is working and settings remain right.
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MDT review
Complex cases — MND, chest-wall disease, post-COVID — are discussed in a multidisciplinary meeting before treatment.
Red flags
When TOSCA moves from routine to urgent.
Findings and conditions that trigger urgent NIV assessment — not routine outpatient follow-up.
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Severe hypercapnia
A markedly elevated nocturnal CO₂ warrants urgent NIV assessment — this is not a routine outpatient finding.
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ALS / MND with FVC < 50%
Motor neurone disease with forced vital capacity below 50% predicted requires urgent ventilatory review.
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Duchenne muscular dystrophy
DMD patients with declining respiratory function need proactive TOSCA and NIV planning, not reactive.
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Post-polio syndrome
Late-onset respiratory failure decades after polio — a classic and often overlooked indication.
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Obesity hypoventilation with cor pulmonale
Right-heart strain from chronic hypercapnia — mandates urgent NIV and cardiology review.
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Kyphoscoliosis
Severe chest-wall deformity restricts ventilation overnight — TOSCA quantifies the deficit before it decompensates.
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Adult-onset central hypoventilation
A rare diagnosis with serious implications — requires TOSCA plus neurology input.
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Post-COVID hypoventilation
Persistent ventilatory failure after severe COVID-19 — an emerging indication for TOSCA-guided NIV.
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Congenital central hypoventilation (CCHS)
The paediatric-onset diagnosis, sometimes only recognised in young adulthood — TOSCA is the diagnostic reference.
Sources
The guidelines this guide is built on.
The four consensus and society guidelines that shape UK practice on nocturnal hypoventilation and NIV.
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American Academy of Sleep Medicine. Clinical practice guidelines on chronic hypoventilation.
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NICE. Motor neurone disease: assessment and management (NG42).
Last reviewed 2026-07-30 · Next review 2027-07-30 · 5-minute read
Frequently asked
Everything patients ask about TOSCA.
Quick answers on what TOSCA measures, how it differs from a standard sleep study, and what happens next.
-
What is a TOSCA sleep study?
A home sleep test that measures oxygen saturation together with continuous transcutaneous carbon dioxide (TcCO₂). Unlike a standard oximetry study, it detects nocturnal hypoventilation — a rise in CO₂ overnight — which is the key finding when the clinical question is ventilation rather than apnoea.
-
How is a TOSCA study different from a standard sleep study?
A standard home sleep study or pulse oximetry study measures oxygen but not CO₂. A patient can have normal oxygen and dangerously high CO₂ overnight. TOSCA adds continuous transcutaneous CO₂ measurement, closing that diagnostic gap. Polysomnography (PSG) adds brain, muscle and eye channels — TOSCA can be combined with PSG when both questions matter.
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Who should have a TOSCA sleep study?
Patients with suspected nocturnal hypoventilation — obesity hypoventilation, neuromuscular disease (MND, DMD, post-polio), advanced COPD, chest-wall disease (kyphoscoliosis), central hypoventilation and any patient where CPAP has failed to resolve symptoms despite apparent adequacy.
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Is a TOSCA study done at home?
Yes — the sensor is fitted at home or in a brief clinic visit, and you sleep in your own bed. There is no need for an overnight hospital stay in most cases.
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What happens after the study?
A consultant sleep physician reviews the traces manually and issues a structured written report, usually within a few days. If nocturnal hypoventilation is confirmed, the same team arranges NIV or CPAP titration and ongoing follow-up.
-
What are the red-flag results?
Severely raised nocturnal CO₂, motor neurone disease with FVC below 50%, obesity hypoventilation with signs of right-heart strain, and post-COVID hypoventilation all warrant urgent NIV assessment rather than routine follow-up.
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In practice, in London
Why private tosca sleep study moves differently in London
With tosca sleep study, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The NHS route for tosca sleep study is thorough, but the queue is real. Most patients we speak with have been told to expect anywhere from a handful of weeks to several months, depending on their local trust and how the referral is graded. Going private in London usually collapses that window to a matter of days — often the same week if the diary allows. It isn’t about jumping a queue so much as buying time back while you still have the flexibility to plan around it.
Once you’re in the private system for tosca sleep study, the pace picks up noticeably. Consultant slots run to time, imaging is usually available in the same building or a short walk away, and the report comes back typed and detailed. It’s the coordination that tends to feel different — one person on the other end of the phone, not a switchboard. For tosca sleep study specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
We’re careful about what a private pathway for tosca sleep study can and can’t promise. It can compress a wait, put you in front of a subspecialist quickly, and get a proper report in your hands within a week. It can’t rewrite what the imaging or the bloods say. Setting that expectation up front tends to make the whole experience less stressful.
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