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Biomedical subjects

W R Elliott

Publications and source records attributed to W R Elliott.

6 recordsLinked to original sources
PubMed1991

Linking mass spectrometers to provide continuing monitoring during system failure.

Although multipatient monitoring with a time-shared mass spectrometer provides considerable cost advantages, failure of one component in a shared system can disrupt gas monitoring at all sites. We describe a simple method for linking two central mass spectrometer systems to provide continual monitoring during failure of one unit, without the need for time-consuming reconfiguration of individual patient sample line and display connections.

Equipment Failure↗
PubMed1989

Positive end-expiratory pressure: implications for tidal volume changes in anesthesia machine ventilation.

In clinical practice, the addition of positive end-expiratory pressure (PEEP) into a standard anesthesia circle circuit decreases the delivered tidal volume (DTV) to a patient. We studied the magnitude of the delta DTV/delta PEEP relationship in two commonly used anesthesia systems. In addition, the magnitude of the delta DTV/delta PEEP relationship varies with both pulmonary compliance and volume of gas contained in the patient's breathing system between the ventilator and PEEP valve site, and this was also evaluated. Routine monitoring of expired tidal volume should be used whenever PEEP is added to an anesthesia circuit.

Anesthesia, Closed-Circuit↗
PubMed1989

The theoretical effect of carboxyhemoglobin on the pulse oximeter.

The relationship between arterial oxygen saturation as measured by the pulse oximeter (SpO2) and the fractional arterial oxygen saturation (SaO2) in the presence and absence of carboxyhemoglobin (COHb) has been derived according to the theory of absorption spectroscopy. We find that our theoretically derived correction equation is similar to that found in the technical literature of Nellcor. However, the correction equations presented by Barker and Tremper and the technical literature of Ohmeda differ substantially from our equation when sufficient quantities of reduced hemoglobin are present and the fractional COHb saturation (SaCO) is high. Our approximated equation, derived from the Lambert-Beer law, is SaO2 = SpO2 (1 - 0.932 SaCO) + 0.032 SaCO. The equation of Barker and Tremper is SaO2 = SpO2 - 0.9 SaCO. The Nellcor equation is SaO2 = SpO2 (1 - SaCO).

Carboxyhemoglobin↗
PubMedDate not supplied

The influence of the mechanics of anesthesia breathing circuits on respiratory monitoring.

Anesthesia breathing circuit mechanics influence respiratory monitoring. Even when the magnitude of these effects is small, their presence may cause confusion and misinterpretation of information. Understanding the interactions between circuit mechanics and monitoring is critical in the design of new circuits and monitoring equipment, and important in their clinical use.

Adult↗
PubMedDate not supplied

A programmable variable waveshape generator for electrosurgical research.

A variable waveform electrosurgical unit (VWESU) was designed and used for electrosurgical research. The design criteria included the ability to modulate the amplitude of a sinusoidal carrier on a cycle-by-cycle basis, output power equivalent to commercial generators, and provision for varying the output impedance. These were realized with a microprocessor-controlled variable waveform generator which allows the user to program waveforms into memory with a set of simple descriptive commands, a linear power amplifier, and a custom output transformer. The contents of the memory are directly pipelined to a set of analog switches, which modulate the radio-frequency carrier with one of eight amplitude levels, thereby bypassing the speed limitations of the microprocessor.

Biomedical Engineering↗