Technology and Health Care - Volume 7, issue 4

Authors: Eberhard, Luc | Haberthür, Christoph | Fabry, Ben | Guttmann, Josef

Article Type: Research Article

Abstract: In intensive care patients who receive ventilatory support or full mechanical ventilation, valuable information can be drawn from gas exchange measurements. In this setting, the most favorable method for gas exchange measurement is by simultaneous recording of gas concentrations and gas flow, and by time resolved multiplication and accumulation. This paper presents a new method to compensate for the signal delay time which occurs when a sampling capillary is used for measuring gas concentrations with a respiratory mass spectrometer or some equivalent sidestream gas analyzer. The signal delay of gas concentrations must be accurately compensated to avoid error accumulation in …gas exchange calculation. A delay time can be easily measured with a test gas in a laboratory setup and be readily compensated for during the measurements in a ventilated patient. This is a standard procedure which gives reasonable results under normal conditions. Special attention is however required in cases where the gas viscosity changes due to large changes in gas composition, e.g., those used for diagnostic breathing or ventilatory maneuvers. Such changes of viscosity will influence the delay time of the capillary, because they affect its flow resistance. As a consequence they will degrade the quality of measurements when done with a simple fixed delay compensation. The method described here consists of an algorithm which enables compensation for such a temporally changing delay time due to changes in gas composition. Show more

Keywords: ICU patient, ventilatory support, gas exchange, FRC, mass spectrometry, sampling capillary, gas transport, gas viscosity, delay time

DOI: 10.3233/THC-1999-7401

Citation: Technology and Health Care, vol. 7, no. 4, pp. 243-259, 1999

Authors: Riva, G. | Bacchetta, M. | Baruffi, M. | Borgomainerio, E. | Defrance, C. | Gatti, F. | Galimberti, C. | Fontaneto, S. | Marchi, S. | Molinari, E. | Nugues, P. | Rinaldi, S. | Rovetta, A. | Samuelli Ferretti, G. | Tonci, A. | Wann, J. | Vincelli, F.

Article Type: Research Article

Abstract: Virtual reality (VR) is an emerging technology that alters the way individuals interact with computers: a 3D computer-generated environment in which a person can move about and interact as if he actually was inside it. Given to the high computational power required to create virtual enviroments, these are usually developed on expensive high-end workstations. However, the significant advances in PC hardware that have been made over the last three years, are making PC-based VR a possible solution for clinical assessment and therapy. VREPAR – Virtual Reality Environments for Psychoneurophysiological Assessment and Rehabilitation – are two European Community funded projects …(Telematics for health – HC 1053/HC 1055 – http://www.psicologia.net ) that are trying to develop a modular PC-based virtual reality system for the medical market. The paper describes the rationale of the developed modules and the preliminary results obtained. Show more

DOI: 10.3233/THC-1999-7402

Citation: Technology and Health Care, vol. 7, no. 4, pp. 261-269, 1999

Authors: Elad, David

Article Type: Research Article

Abstract: The human respiratory system is an ‘open’ organ, which is designed to exchange oxygen and carbon dioxide between the circulating blood and the external environment. This gas exchange is successfully accomplished via a set of transport phenomena comprised of oscillatory air flow, heat and water vapor exchange, mucus transport and air-blood gas exchange all of which take place in a complex geometry that undergoes large changes. These transport phenomena occur simultaneously to supply the body’s need for oxygen in different physiological conditions and/or environments, while defending it from external hazards. The need for better comprehension of the mechanisms involved in …pulmonary diseases and for advanced techniques for both diagnosis and intervention stimulated numerous studies of the different biotransport processes that take place in the human respiratory system. Show more

Keywords: Pulmonary gas exchange, nasal physiology, mucus, diffusion capacity, biofluid

DOI: 10.3233/THC-1999-7403

Citation: Technology and Health Care, vol. 7, no. 4, pp. 271-284, 1999

Authors: Ylöstalo, Jyri

Article Type: Research Article

Abstract: Modern brain research experiments require the recording of large amounts of high-accuracy EEG data. Sampling frequency, bit resolution and number of channels are significantly larger than in routine clinical measurements. Because of this, the need of efficient signal compression has emerged. This paper presents a survey of available methods and explores some techniques, both lossy and lossless, for compressing EEG signals.

Keywords: EEG, data compression, vector quantization, subband coding, principal component analysis

DOI: 10.3233/THC-1999-7404

Citation: Technology and Health Care, vol. 7, no. 4, pp. 285-300, 1999

Authors: Bajd, Tadej | Munih, Marko | Kralj, Alojz

Article Type: Research Article

Abstract: Prolonged immobilization, such as occurs after the spinal cord injury (SCI), results in several physiological problems. It has been demonstrated that the standing posture can ameliorate many of these problems. Standing exercise can be efficiently performed by the help of functional electrical stimulation (FES). The first application of FES to a paraplegic patient was reported by Kantrowitz in 1963. It was later shown by our group that standing for therapeutic purposes can be achieved by a minimum of two channels of FES delivered to both knee extensors. The properties of the stimulated knee extensors (maximal isometric joint torque, fatiguing, …and spasticity) were not found as sufficient conditions for efficient standing exercise. According to our studies, the ankle joint torque during standing is the only parameter which is well correlated to the duration of FES assisted standing. For good standing low values of the ankle joint torque are required. To minimize the ankle joint torque the lever belonging to the vertical reaction force must be decreased. Adequate alignment of the posture appears to be the prerequisite for efficient FES assisted and arm supported standing exercise. Some patients are able to assume such posture by themselves, while many must be aided by additional measures. At present, surface stimulation of knee extensors combined with some appropriately “compliant shoes” looks to be adequate choice. Show more

DOI: 10.3233/THC-1999-7405

Citation: Technology and Health Care, vol. 7, no. 4, pp. 301-308, 1999

Authors: Mols, Georg | Kessler, Volker | Benzing, Albert | Schneider, Matthias | Kühne, Lioba | Geiger, Klaus | Guttmann, Josef

Article Type: Research Article

Abstract: Mechanical ventilation is an important, often life-saving component of modern intensive care medicine. However, it may further aggravate pulmonary pathology by endinspiratory overdistension of the alveoli or by their endexpiratory collapse. To prevent both the ventilator may be adjusted based on the slope of the pressure-volume curve, named as compliance, which is often determined by a stepwise inflation of the lungs. This maneuver gained no widespread clinical acceptance because of being cumbersome and invasive. Therefore, we developed a modification of the well known interrupter technique – the Traveling Shutter Wave. A wave of short-term (300 ms) occlusions “travels” over the …tidal volume range. Differential compliance is calculated by division of volume and pressure differences between two adjacent occlusion maneuvers. The technique is well suited for the clinical setting because the ventilatory pattern does not need to be changed. This manuscript describes the realization of the Traveling Shutter Wave as well as its application in two patients. Show more

DOI: 10.3233/THC-1999-7406

Citation: Technology and Health Care, vol. 7, no. 4, pp. 309-317, 1999