Apple Watch SpO2 of 88% prompts CT that finds pulmonary embolism

AI system

System: Apple Watch Blood Oxygen app
Model: Not assessed
Release: Exact release not established.
Application developer: Apple
Role: The watch estimated blood-oxygen saturation from optical measurements.
Configuration: The initial event involved an Apple Watch Series 7. A later report involved a Series 6.
Inputs and outputs: Not assessed
Autonomy: Not assessed
Workflow: The wearer has an Apple Watch with the Blood Oxygen app and reviews its readings. A hypoxemic condition produces a persistently low reading at home. The wearer reports the reading and a clinician acts on it despite normal spot oximetry.
Human oversight: Not assessed
Relation to AI: The watch's pulse-oximetry algorithm produced the 88% reading on the patient's watch. The letter does not say who reported it to the clinicians and describes no automatic alert. Clinicians chose to perform CT angiography because of that reading and state that it led to the diagnosis.
AI contribution: The watch's pulse-oximetry algorithm produced the 88% reading on the patient's watch. The letter does not say who reported it to the clinicians and describes no automatic alert. Clinicians chose to perform CT angiography because of that reading and state that it led to the diagnosis.

Benefits

Outcome identifiers: Not assessed
Benefit: Apple Watch Series 7 had shown an oxygen saturation of 88% in the early morning
Category: Improved Physical Health
Status: Not assessed
Beneficiary groups: People.
Beneficiaries: Not assessed
Reach: Not assessed
Distribution and access: Not assessed
Duration: Not assessed
Expected?: No
Costs and harms: Not assessed

Measurement

Studies: Not assessed
Study design: Not assessed
Measurement: Not assessed
Setting and sample: Not assessed
Measures: Apple Watch Series 7 had shown an oxygen saturation of 88% in the early morning
Comparison: Not assessed
Results: Apple Watch Series 7 had shown an oxygen saturation of 88% in the early morning
Additional value from AI: Not assessed
Limitations: Not assessed
Denominators: Not assessed
Materials for replication: Not assessed

Money

Kind of value: Not assessed
Amount: Not assessed
Currency and prices: Not assessed
Period and unit: Not assessed
Realization: Not assessed
Recipients and payers: Not assessed
Gross or net: Not assessed
Included costs: Not assessed
Comparison: Not assessed
Method: Not assessed
Return and payback: Not assessed

People and places

Participants: Developer: Apple.
Jurisdictions: Benefit: Yufu, Oita Prefecture, Japan. Developer: United States.
Ownership and control: Not assessed
Dependencies: Not assessed
Cross-border connections: Not assessed
Geopolitical implications: Not assessed

Follow-up

Conditions for replication: The reading is not dismissed as artifact. Confirmatory testing (CT angiography, co-oximetry) is available. Effective treatment exists for the condition found.
Replication attempts: 1 follow-up entries. Benefit did not recur: 1.
Later findings: No development after the 2022 case report was found; the 2025 methemoglobinemia report involved a different patient and mechanism.
Availability: Not assessed
Institutional decision: Not assessed
Grounds: Not assessed
Action and result: Not assessed
Success criterion: Not assessed

Evidence

Source numbers: AIBD-0022-source-0001–0002
Citations: Numbered references below.
Language: Not assessed
Source relationships: Independent
Original evidence: Not assessed
Access and versions: Not assessed
Supported findings: Not assessed
Evidence links: Not assessed
Evidence strength: Not assessed
Missing evidence: Not assessed

Grades

Assessed benefits: People.
Depth: People: 3.
Reasons: People: A pulmonary embolism with bilateral DVT was diagnosed and anticoagulated after hospital oximetry had been normal. A life-changing benefit, though the source does not establish that death was imminent.
Observed or intended: Not assessed
Rubric: Not assessed
Assessor and date: Not assessed
Alternative assessments: Not assessed
Fill: Independently studied

Entry details

Kind

Not assessed

Related entries

Same device, Apple Watch: a sensor-driven alert that was false (Crash Detection dialed 911 for skiers) mirrors a sensor reading that was true (88% SpO2 prompting CT); harmed were Apple Watch users and dispatchers.

Field

Healthcare (emergency and respiratory medicine). Consumer wearables.

Purpose

The Blood Oxygen app measures oxygen saturation for general wellness and is not intended for medical diagnosis. Detecting a pulmonary embolism was not what it was built to do.

Dates

Date basis unassessed: 2022 (precision unassessed). Updated: 21 October 2026.

Stage

Not assessed

Version

SHA-256: 37aad5184fa2…

References

Other identifiers: AI Incident Database: 463.
Category mappings: Not assessed
Brief: Not assessed
Revisions: 6 revisions. Latest: 21 October 2026.

Sources

Case report Independent author

Shiota S, Horinouchi Y, Doi E, Miyazaki E (2022). Suspicion of pulmonary embolism after COVID-19 infection raised by a smartwatch. QJM, hcac217 (online 5 Sep 2022; issue 2023).
Case report Independent author

Tulisiak LN, Loesing ME, Ljungberg A, Kaczor EE (2025). Smartwatch Detection of Refractory Hypoxemia in Phenazopyridine-Induced Methemoglobinemia: A Case Report. Journal of Medical Toxicology 21(4):430-433.