1. Abnormal performance (core indicators)
Unstable readings:

SpO₂ values ​​frequently jump (such as fluctuations of more than ±5%) and cannot lock the value.

The signal strength bar (perfusion index/PI) is continuously too low (such as PI < 0.3%).

Inaccurate data:

Does not match clinical symptoms (such as the patient has no dyspnea but the SpO₂ display is extremely low).

Compared with other monitoring devices (such as arterial blood gas analysis), the difference is significant.

Unable to detect:

The probe has no signal output at all, or the device prompts "sensor failure" or "signal loss".

2. Physical damage
Appearance inspection:

The cable is damaged, broken, or the internal wire is exposed.

The probe clip spring is loose and cannot fit tightly to the finger/earlobe (affecting light transmittance).

The light-emitting window (LED or photoelectric receiver) is dirty, scratched, or aged and yellowed.

Functional test:

Signal interruption occurs when the probe is gently shaken (possibly poor internal contact).

3. Hygiene and contamination
Visible contamination:
Probes come into contact with blood, body fluids, sweat or adhesive residues.
Mold or odor on the surface (long-term non-replacement).
Infection risk:
Used between different patients (disposable probes are strictly prohibited from being reused).
Used by the same patient for longer than the recommended time (e.g. >24-48 hours).
 

4. Service life and time
Disposable probes:
Exceed the manufacturer's single/short-term use period (even if the appearance is intact).
Reusable probes:
Reach the manufacturer's nominal life (e.g. 1-2 years) or number of uses.
Excessive disinfection times lead to material aging (e.g. silicone hardening, loss of viscosity).
 

5. Clinical scenario requirements
High-risk environment:
It is recommended to strictly follow the specifications for replacement in surgery and ICU to avoid potential failures.
Home use:
If the reading is normal and there is no damage, the use time can be appropriately extended, but regular inspection is required.
 

Operational recommendations
Cross-validation:
Replace another device or a new probe to compare the readings.

Cleaning attempt:

Gently wipe the luminous window with alcohol cotton (only for cleanable probes) and observe whether the performance is restored.

Record replacement:

Mark the date of first use to avoid overuse.

Notes
Disposable probes cannot be reused: even if the performance is normal, repeated use may violate infection control regulations.

Newborns/burn patients: Skin is sensitive and needs to be replaced more frequently (such as every 12 hours).