Nihon Kohden BSM-2301K: NIBP pumps endlessly, no reading
What happened
The monitor's NIBP never completes a measurement: the pump keeps inflating without reaching a result, and the behaviour is the same with different cuffs.
What was checked
- Leak-check the cuff and extension hose first — the quickest things to rule out and a common offender.
- Inspect the internal pneumatic line and its connections along the whole path for leaks.
- Hold the compressor pistons up to a light: a pinhole can be so small it is only visible on backlight.
Cause
A leak somewhere in the pneumatic circuit: a punctured cuff or extension hose, a leak in the internal line inside the monitor, or a pinhole in one of the compressor pistons — the case describes a four-piston compressor, and such a hole can be nearly invisible except against a light. While the leak persists, the pump never reaches the target pressure and keeps running, so no measurement is produced.
The cause is probable and was not fully confirmed.
What was done
Find and eliminate the leak: replace or repair the cuff or extension hose, seal the leaking internal line (in this case, done with ties), or replace the compressor or its pistons. The engineers noted this resolution as probable for the case; after the repair, confirm a full inflate–measure–deflate cycle completes normally.
Safety
Bleed off any residual pressure in the pneumatic circuit and unplug the monitor before opening it, and run an electrical safety test before the unit is returned to patient use.
Lesson: When NIBP pumps endlessly with any cuff, treat it as a leak hunt: start at the cuff and hose, then work inward through the line to the compressor pistons.
Covered in the course: Patient Monitor Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.