Which apnea monitoring method uses optical fibers woven into a belt around the chest?

• A. Piezoelectric plethysmography
• B. Fiberoptic plethysmography
• C. Thermistors
• D. Electrical impedance tomography

Answer: (B)

Fiberoptic plethysmography is the technique that uses optical fibers woven into a belt around the chest to monitor breathing. As the chest expands and contracts, the belt stretches and changes how light travels through or reflects from the tissue. A detector picks up these light changes and converts them into a waveform that tracks respiratory effort and pauses. This optical method is distinct from other approaches: a piezoelectric sensor also measures chest wall movement but does so with a mechanical sensor rather than optics; thermistors detect airflow by sensing temperature changes of inspired versus expired air rather than chest motion; and electrical impedance tomography uses electrodes to measure impedance changes across the chest to infer ventilation, not optical signals from a fiber belt. So the described method—fiberoptic plethysmography—fits the use of optical fibers in a chest belt to monitor apnea.