Journal of Clinical Monitoring and Computing, 1993
Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyh... more Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyhemoglobin and methemoglobin. This paper attempts to alleviate some of the confusion that exists between fractional and functional saturation, and to clarify the comparison of each with SpO2. A series of theoretical relationships between pulse oximeter reading (SpO2) and actual oxygen saturation (both fractional and functional) is derived using simple absorption theory. The theoretical relationships are checked using an experimental in vitro test system. This consists of a blood circuit containing a model finger, capable of simulating the pulsatile transmission signals through a real finger. Theoretical predictions and experimental results are compared and are found to agree well in the presence of carboxyhemoglobin, but less well with methemoglobin. Possible reasons are discussed.
Surgical diathermy is an important tool for arresting bleeding from small vessels and for cutting... more Surgical diathermy is an important tool for arresting bleeding from small vessels and for cutting tissues whilst maintaining haemostasis. Although haemostasis can be achieved by the application of heat generated and conducted to the tissues by means other than electrical, radio-frequency (RF) diathermy is a convenient, quick and reasonably safe method.
Journal of Clinical Monitoring and Computing, 1993
Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyh... more Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyhemoglobin and methemoglobin. This paper attempts to alleviate some of the confusion that exists between fractional and functional saturation, and to clarify the comparison of each with SpO2. A series of theoretical relationships between pulse oximeter reading (SpO2) and actual oxygen saturation (both fractional and functional) is derived using simple absorption theory. The theoretical relationships are checked using an experimental in vitro test system. This consists of a blood circuit containing a model finger, capable of simulating the pulsatile transmission signals through a real finger. Theoretical predictions and experimental results are compared and are found to agree well in the presence of carboxyhemoglobin, but less well with methemoglobin. Possible reasons are discussed.
Surgical diathermy is an important tool for arresting bleeding from small vessels and for cutting... more Surgical diathermy is an important tool for arresting bleeding from small vessels and for cutting tissues whilst maintaining haemostasis. Although haemostasis can be achieved by the application of heat generated and conducted to the tissues by means other than electrical, radio-frequency (RF) diathermy is a convenient, quick and reasonably safe method.
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Papers by John Moyle