Patient Monitoring System

An Android patient monitoring application that interfaces over serial communication with ZUG Medical and Witleaf multi-parameter modules, covering ECG, RESP, SpO₂, NIBP and TEMP. I architected and built it end to end, from requirements through to deployment. It is in clinical use at Lakshmi Foundation Hospital.

Holding the sample rate#

Waveform rendering and data acquisition run concurrently across four parameter streams, sustaining over 2000 samples per second on a multi-threaded Java architecture.

That figure drove the entire design. A clinician reading an ECG trace is reading its shape, so dropped samples change what the trace says, not merely how smoothly it animates. Acquisition and rendering could not be allowed to contend for the same thread, and neither could block behind storage writes.

Alarms#

The alarm subsystem separates physiological alarms, which concern the patient, from technical ones such as a detached lead or a disconnected module. These demand different responses from ward staff, so each class has its own visual state and audio tone rather than sharing a single undifferentiated alert.

Two behaviours mattered more than the rest. Alarm and arrhythmia logging is keyed to patient ID, so the record follows the patient rather than the device. Monitoring also resumes across a restart, because a monitor that forgets its state after a power event has failed at precisely the moment it was needed.

What I took from it#

Building for a ward changes the definition of finished. The questions that dominated review were not about features. They were about behaviour on power loss, on a disconnected lead, and on a device left running for three weeks without a restart. Most software is never asked those questions.