monitor of respiration. Bull. Eur. Physiopathol. Respirat., 18, 643-658. FRAa~R, R. A. S. and HANNING, C. D. (1986) Non-invasive respiratory monitoring. Intensive Care World, 3, 46-47. GEDDES, L. A. and BAKER, L. E. (1975) Principles of applied biomedical instrumentation, 2nd edn. Wiley, New York, Sect. 10.13. GRIBB1N, H. R. (1983) Using body surface movements to study breathing. J. Med. Eng. Technol., 7, 217-223. HANN1NG, C. D., SMITH, H. C. and LEDINGHAM, I. McA. (1978) Clinical application of inductive plethysmography. Scot. Med. J., 23, 310-311. HILL, D, W. (1973) Electronic techniques in anaesthesia and surgery, 2nd edn. Butterworths, London, Chap. 3. HILL, S. L., BLACKBURN, J. P. and WILLIAMS, T. R. (1982) Measurement of respiratory flow by inductance pneumography. Med. & Biol. Eng. & Comput., 20, 517-518. KONNO, K. and MEAD, J. (1967) Measurement of the separate volume changes of rib cage and abdomen during breathing. J. Appl. Physiol., 22, 407-422. MILLEDGE, J. S. and STOTT, F. D. (1977) Inductive plethysmography--a new respiratory transducer. J. Physiol. (London), 267, 4P-5P. MILLMAN, R. P., CntrNG, D.-C. C. and SHORE, E. T. (1986) Importance of breath size in calibrating the respiratory inductive plethysmograph. Chest, 89, 840-845. PATTERSON, R. P. (1985) Sources of the thoracic cardiogenic electrical impedance signal as determined by a model. Med. & Biol. Eng. & Comput., 23, 411-417. RAMO, S., WHINNERV, J. R. and VAN DUZER, T. (1965) Fields and waves in communication electronics. Wiley, New York, Sect. 5.25. SEAGAR, A. D. (1983) Probing with low frequency electric currents. Ph.D. Thesis, University of Canterbury, Christchurch, New Zealand. SEAGAR, A. D., GIBBS, J. M. and DAV[S, F. M. (1984) Interpretation of venous occlusion plethysmographic measurements using a simple model. Med. & Biol. Eng. & Comput., 22, 12-18. SOKAL, R. R. and ROHLF, F. J. (1981) Biometry. The principles and practice of statistics in biological re'search, 2nd edn. W. H. Freeman, San Francisco, Sect. 15.2. STRADLING, J. R., CHADWICK, G. A., QUIRK, C. and PHILLIPS, T. (1985) Respiratory inductance plethysmography" calibration techniques, their validation and the effects of posture. Bull. Eur. Physiopathol. Respirat., 21, 317-324. TISI, G. M. (1980) Pulmonary physiology in clinical medicine. Williams & Wilkins, Baltimore, Chap. 4. UNDERWOOD, Z. (1973) Beckman BR-100 Bilateral Impedance Rheograph operating instructions. Beckman Instruments Inc., Schiller Park, IL 60176, USA. WATSON, H. (1980) The technology of respiratory inductive plethysmography. In Proc. 3rd Int. Symp. Ambulatory Monitoring (ISAM 1979). STOTT, F. D., RAFTERY, E. B. and GOULDING, L. (Eds.), Academic Press, London, 537-563. WHEELER, H. B., ANDERSON, F. A. Jr, MATESANZ, J. M. and LARSEN, J. E. (1978) Impedance phlebography: the diagnosis of venous thrombosis by occlusive impedance plethysmography. In Noninvasive diagnostic techniques in vascular disease. BERNSTEIN, E. F. (Ed.), C. V. Mosby, St Louis, 359-373. WILSON, A. J., FRANKS, C. I. and FREESTON, I. L. (1982) Methods of filtering the heart-beat artefact from the breathing waveform of infants obtained by impedance pneumography. Med. & Biol. Eng. & Comput., 20, 293-298.