The Extensometer

The Extensometer is a new device capable of continuous accurate measurement of length over convex surfaces with a rapid response rate. This makes it a powerful research tool and a useful clinical instrument, particularly in the field of respiratory monitoring. This paper describes the principles behind the device. The linearity of its response was demonstrated in laboratory tests and its ability to quantify abdominal and chest wall movement was assessed in anaesthetised patients. Potential applications in the field of ventilatory pattern analysis and respiratory monitoring in anaesthesia and intensive care are discussed.