Biomedical instrumentation & technology / Association for the Advancement of Medical Instrumentation
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Biomed Instrum Technol · Nov 1991
Case ReportsIntermittent-flow expiratory ventilation (IFEV): delivery technique and principles of action--a preliminary communication.
The ventilator support utilized in acute respiratory failure can exacerbate an underlying lung injury. Various ventilation techniques have been introduced to prevent such damage by limiting tidal volume and inflation pressure, ensuring uniform expansion of the lung, and stabilizing lung volume during expiration. Acceptance of such methods has been limited. ⋯ By eliminating end-tidal gas in the conducting air passages, series deadspace is functionally reduced, permitting lowering of tidal volume and airway pressures without a corresponding reduction in CO2 removal. This effect may benefit patients who have acute lung injury by permitting ventilator settings with lower tidal volumes and peak airway pressures. The technique of IFEV delivery, a successful clinical application, and possible ways to improve IFEV efficiency are discussed.
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Biomed Instrum Technol · Nov 1991
Noninvasive measurement of arterial oxyhemoglobin saturation with a heated and a non-heated skin reflectance pulse oximeter sensor.
The feasibility of measuring arterial oxyhemoglobin saturation (SaO2) noninvasively using a skin reflectance pulse oximeter sensor attached to the scalp, neck, and thigh regions of anesthetized swine was investigated. The optical reflectance sensor used consisted of a pair of red and infrared light-emitting diodes and a concentric array of six identical photodiodes. Two prototype sensor assemblies were evaluated: one assembly housed only the optical sensor, whereas the other also included a miniature heater. ⋯ The equations for the best-fitted linear regression lines describing the relationships between SpO2(r) and SaO2 values in the range between 30 and 100% were: SpO2(r) = 10.7 + 0.90 (SaO2), n = 321, r = 0.97; SpO2(r) = 16.72 + 0.82 (SaO2), n = 217, r = 0.95; and SpO2(r) = 20.21 + 0.77 (SaO2), n = 37, r = 0.97 for the neck, thigh, and scalp measurements, respectively. The regression analysis revealed significant correlation and a relatively small standard error of estimate (SEE = 4.05% for the neck, 4.79% for the thigh, and 3.50% for the scalp measurements). This study demonstrated the feasibility of measuring SaO2 noninvasively over a wide range of values utilizing the principle of reflectance pulse oximetry.
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Biomed Instrum Technol · Jul 1990
Comparative StudyComputer-aided characterization and optimization of the Thumper compression waveform in closed-chest CPR.
Optimization of blood flow and blood pressure is critical for a positive outcome of cardiopulmonary resuscitation (CPR). The use of models can facilitate the analysis of different methods of performing CPR. Programming with SPICE software, the authors modified a hardware model electrically equivalent to the human cardiovascular system into a software model to analyze and predict the hemodynamic output parameters of different compression waveform inputs used in thoracic pump CPR. ⋯ The model also predicted increased mean systolic pressure when the duty cycle increased from 20% to 80% while diastolic pressure decreased slightly. Although mean systolic pressure increased with increased duty cycle, the model predicted a decrease in coronary flow at the higher duty cycles of all compression waveforms. Increases of 75% to 100% in systolic pressure and blood flow were produced when increases in chest compression force and the rapidity of the rise time, termed "spike-impulse" CPR, were simulated.
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Biomed Instrum Technol · Mar 1990
Comparative StudyA comparison of a new reflectance oximeter with the Hewlett-Packard ear oximeter.
The purpose of this study was to characterize the accuracy and dynamic response characteristics of traditional transmittance pulse oximeters and a new reflectance pulse oximeter with regard to the current standard in oximetry, the Hewlett-Packard ear oximeter. Studies were performed with 15 healthy male and female subjects. A rebreathing technique was employed to produce a steady fall in oxygen saturation and to maintain constant, eucapnic, end-tidal CO2 levels. ⋯ This value was similar to that of the transmittance oximeters (Criticare 501+: 0.92 +/- 2.11), (Physio-Control: 3.15 +/- 2.04), (Ohmeda 3700: 2.05 +/- 2.06). There was virtually no response-time difference between the reflectance oximeter with the sensor placed on the subject's forehead and the Hewlett-Packard ear oximeter. The authors conclude that the accuracy of the reflectance oximeter is within the limits of clinical acceptance for monitoring and trending of arterial oxygen saturation in healthy subjects.