Feasibility Notes
Summary
The handheld BLE rhinomanometer is technically feasible, but diagnostic accuracy depends primarily on the complete pneumatic measurement system rather than the PCB alone. The largest risks are achieving both high sensitivity during quiet breathing and sufficient headroom during forced blowing, preserving matched pressure/flow dynamics through tubing and filters, managing condensation, and maintaining traceable calibration.
Recommended Technical Direction
- Use two synchronized differential-pressure measurement channels: one for nasal differential pressure and one across a calibrated bidirectional flow restriction.
- Select sensing ranges of at least ±1200 Pa for nasal pressure and a flow-channel pressure sensor matched to the chosen flowhead's pressure drop.
- Prefer digital or precision analog sensors with low zero drift and documented bandwidth; validate the assembled pneumatic channel to 80 Hz.
- Sample both channels at 500–1000 samples/s with a shared timebase, then stream or buffer data over BLE.
- Use a low-power BLE SoC and a single-cell battery with USB-C power-path charging.
- Include temperature, humidity, and barometric sensing for metadata and correction.
Main Engineering Risks
- Flowhead design: It determines flow accuracy, added breathing resistance, linearity, cleanability, and condensation behavior.
- Dynamic matching: Different tubing volumes or sensor filters can create phase shift and false pressure-flow loops.
- Zero stability: ±1200 Pa full scale must still provide useful resolution and low drift near 75–150 Pa.
- Patient-interface leaks: Mask and sealed-nostril leaks directly bias resistance results.
- Wireless data integrity: Continuous synchronized acquisition needs buffering and dropped-packet detection.
- Medical-device pathway: Diagnostic claims require ISO 14971 risk management, IEC 60601 electrical/EMC work, software lifecycle controls, usability engineering, and clinical validation as applicable.
Immediate Feasibility Experiment
Before freezing the schematic, construct and test candidate flow elements with a traceable reference source. Measure pressure drop, bidirectional linearity, hysteresis, added resistance, repeatability after cleaning/filter replacement, and response with representative tubing across ±1200 cm³/s. The resulting pressure-drop curve will determine the correct flow-channel sensor range.
Sources Used
- GM Instruments, NR6 Rhinomanometer Instructions for Use, Issue 18, 2025.
- Vogt et al., “The new agreement of the international RIGA consensus conference on nasal airway function tests,” Rhinology 56, 2018.
- Eccles, “A guide to practical aspects of measurement of human nasal airflow by rhinomanometry,” Rhinology 49, 2011.