Basic Physics and Measurement in Anaesthesia, 1995
Publisher Summary This chapter deals first with the systems by which gases or anaesthetic vapours... more Publisher Summary This chapter deals first with the systems by which gases or anaesthetic vapours may be delivered to the patient's airway.
Knowledge of the origin of hydrogen ions (protons) is central to their therapeutic regulation. It... more Knowledge of the origin of hydrogen ions (protons) is central to their therapeutic regulation. It is the purpose of this paper to indicate which factors are involved in the origin and control of hydrogen ions in order to optimize the biochemistry of patients undergoing cardiac surgery.
Basic Physics and Measurement in Anaesthesia, 1995
This chapter discusses the different methods used for presentation and handling of clinical data.... more This chapter discusses the different methods used for presentation and handling of clinical data. In circumstances such as the inflation of the lungs by a ventilator, there are several quantities or variables that change in value as inflation proceeds. A graph is a convenient way of showing how one variable depends on another. It has two axes, each of which is assigned to a variable, and on each axis, a scale is marked showing the values taken by that variable. The horizontal axis is called the abscissa or the x-axis, and the vertical axis is called the ordinate or the y-axis. In a histogram, the height of bands or columns is used to illustrate the relative sizes of quantities. The histogram gives good visual impact and is particularly useful for illustrations used in teaching. Graphs are not the only way in which data can be presented diagrammatically. A pie diagram is a useful technique to illustrate how a certain quantity is divided up. In skewed circumstances, although a mean and standard deviation can be calculated, the shape of the distribution may be described better by using percentiles. A percentile is the value of the variable being measured that splits the distribution into two parts with a particular percentage in each. When individual results are plotted as points on a graph they are usually scattered, although an underlying trend may be apparent. A scatter diagram thus shows how the results are distributed.
A workshop to introduce medical teachers to the use of microcomputers is described. Details are g... more A workshop to introduce medical teachers to the use of microcomputers is described. Details are given of the programs demonstrated, which include interactive programs to interview patients, clinical management simulations, educational games and diagnostic simulations and aids. The plenary discussion is reported as an explanation of computer terms and advice for setting up microcomputers as teaching aids.
Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and a... more Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and acidosis in patients with cardiorespiratory disease. The aim of the present study was to assess helium as an alternative to carbon dioxide for creating the pneumoperitoneum. Ventilation requirements and carbon dioxide levels were assessed at the beginning and end of laparoscopic cholecystectomy using helium (n = 30) and carbon dioxide (n = 30) pneumoperitoneum. Insufflation with helium did not result in an increase in ventilation requirement although, like carbon dioxide pneumoperitoneum, it was associated with a mean rise in peak airway pressure (of 7 cmH2O; P < 0·001). There was also a 3·2-kPa increase in the alveolar-arterial oxygen gradient with helium (P = 0·006). Carbon dioxide pneumoperitoneum was associated with a significant rise in arterial carbon dioxide levels, despite increasing ventilation. Four patients with helium pneumoperitoneum had surgical emphysema for 5 days. Heli...
As part of a randomized trial, ventilatory and arterial blood gas changes were assessed during op... more As part of a randomized trial, ventilatory and arterial blood gas changes were assessed during open (n = 30) and laparoscopic (n = 30) cholecystectomy. Measurements were made during anaesthesia before the start of surgery and at the time of removal of the gallbladder. Despite an increase in minute ventilation from a mean(s.d.) of 5·7(1·4) to 6·1(1·2) litres, mean(s.d.) arterial carbon dioxide tension (PaCO2) rose from 5·3(0·9) to 6·0(0·9) kPa during laparoscopic cholecystectomy. End-tidal carbon dioxide tension (PE'CO2) had poor precision in predicting PaCO2 (95 per cent interval of agreement −0·61 to 1·93 kPa). Mean(s.d.) peak airway pressure increased from 17(4) to 23(4) cmH2O. The mean PaCO2–PE'CO2 value did not change significantly, although there was significant within-patient variation. Arterial oxygen levels did not change significantly. By comparison, no clinically significant changes in ventilation or blood gas values occurred during open cholecystectomy. In conclus...
Plasma hormone measurements following midazolam administration We were interested to read the exc... more Plasma hormone measurements following midazolam administration We were interested to read the excellent paper by Drs Dawson and Sear (Anaes/hesia 1986; 41: 268 71) since
Several investigators have emphasised the value of the analysis of volume-pressure waveforms as a... more Several investigators have emphasised the value of the analysis of volume-pressure waveforms as an aid to monitoring patients in the intensive care unit (Lewis et al., 1966; Proctor et al., 1970; Hilberman et al., 1975; Wilson, 1976).
Optimum management of the critically ill patient requires frequent monitoring of many variables a... more Optimum management of the critically ill patient requires frequent monitoring of many variables and an ability to detect and act upon significant changes in patient condition at an early stage. This intensive monitoring leads to the rapid accumulation of vast amounts of data in which significant changes in patient condition may remain undetected (Osborne et al. 1968). This type of data collection is ideal for handling by computer, which allows clear presentation of informative and relevant aspects of the information. The improvement in data presentation should result in fewer management errors by the clinician (Jenkins et al. 1968), and in the early detection and correction of adverse trends (Kenny and Campbell 1982).
In the past, the discovery of new drugs often occurred by chance. Over recent years, an increasin... more In the past, the discovery of new drugs often occurred by chance. Over recent years, an increasing knowledge of the mode of drug action and receptor sites has improved our ability to design new drugs. While the mode of action of volatile and intravenous anaesthetic agents remains unclear, neuromuscular blocking agents and opioids have undergone considerable development and design. Drugs are being tailored to produce fewer side effects and to improve desirable properties. As a result, the introduction of new drugs has helped to improve techniques in anaesthesia. The development of remifentanil is an example of this which is discussed. The application of modern technology with target controlled infusions (TCI) for the administration of remifentanil represents further advancement in techniques which may become available to anaesthetists in the future.
Propofol was administered intravenously using a first-order, three-compartment, computer-controll... more Propofol was administered intravenously using a first-order, three-compartment, computer-controlled infusion pump (CCIP) based on the Ohmeda 9000 syringe pump. The CCIP system produced a target-controlled infusion (TCI) based on the estimated blood concentration (EBC). Twenty-five patients undergoing ambulatory surgery completed the study. The induction EBC was 4.72 +/- 0.28 micrograms/ml, and was achieved rapidly with minimal hemodynamic changes. The emergence EBC was 1.55 +/- 0.21 micrograms/ml, and the discharge EBC was 1.06 +/- 0.22 micrograms/ml. The EBC, together with clinical signs, allowed for predictable inductance and emergence from anesthesia using propofol.
There is a growing interest in the potential benefits to be obtained from closed-loop control of ... more There is a growing interest in the potential benefits to be obtained from closed-loop control of drug infusion [1-5]. The most widely available infusion pump which is specifically designed for control by computer is the 929 volumetric infusion pump produced by Imed. The increasing availability of microcomputers suggests that they will be used more frequently to control such pumps. However, difficulties can arise when the attempt is made to establish communication between the computer and the pump [6] and a method employed for this purpose is described in this article. The aim was to provide a simple method of conducting the required communication between the computer and the pump using a high-level language. The commands specified in the high-level language are passed to a machine-code subroutine which organizes transmission to and receives data from the pump.
International Journal of Clinical Monitoring and Computing, 1992
A Psion microcomputer controlled infusion system for alfentanil was assessed for the provision of... more A Psion microcomputer controlled infusion system for alfentanil was assessed for the provision of postoperative analgesia in 14 patients who had undergone aortic bifurcation graft surgery. The system employed a pharmacokinetic model working in real time to deliver any selected target plasma concentration of alfentanil. The alfentanil infusion system was used for a mean time of 39 hours and for 96% of this time, patients were scored as having no pain or only mild pain. Severe pain was recorded for only 0.05% of the study time. The use of a pharmacokinetic delivery system may offer a convenient and simple method of providing postoperative analgesia with alfentanil.
Basic Physics and Measurement in Anaesthesia, 1995
Publisher Summary This chapter deals first with the systems by which gases or anaesthetic vapours... more Publisher Summary This chapter deals first with the systems by which gases or anaesthetic vapours may be delivered to the patient's airway.
Knowledge of the origin of hydrogen ions (protons) is central to their therapeutic regulation. It... more Knowledge of the origin of hydrogen ions (protons) is central to their therapeutic regulation. It is the purpose of this paper to indicate which factors are involved in the origin and control of hydrogen ions in order to optimize the biochemistry of patients undergoing cardiac surgery.
Basic Physics and Measurement in Anaesthesia, 1995
This chapter discusses the different methods used for presentation and handling of clinical data.... more This chapter discusses the different methods used for presentation and handling of clinical data. In circumstances such as the inflation of the lungs by a ventilator, there are several quantities or variables that change in value as inflation proceeds. A graph is a convenient way of showing how one variable depends on another. It has two axes, each of which is assigned to a variable, and on each axis, a scale is marked showing the values taken by that variable. The horizontal axis is called the abscissa or the x-axis, and the vertical axis is called the ordinate or the y-axis. In a histogram, the height of bands or columns is used to illustrate the relative sizes of quantities. The histogram gives good visual impact and is particularly useful for illustrations used in teaching. Graphs are not the only way in which data can be presented diagrammatically. A pie diagram is a useful technique to illustrate how a certain quantity is divided up. In skewed circumstances, although a mean and standard deviation can be calculated, the shape of the distribution may be described better by using percentiles. A percentile is the value of the variable being measured that splits the distribution into two parts with a particular percentage in each. When individual results are plotted as points on a graph they are usually scattered, although an underlying trend may be apparent. A scatter diagram thus shows how the results are distributed.
A workshop to introduce medical teachers to the use of microcomputers is described. Details are g... more A workshop to introduce medical teachers to the use of microcomputers is described. Details are given of the programs demonstrated, which include interactive programs to interview patients, clinical management simulations, educational games and diagnostic simulations and aids. The plenary discussion is reported as an explanation of computer terms and advice for setting up microcomputers as teaching aids.
Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and a... more Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and acidosis in patients with cardiorespiratory disease. The aim of the present study was to assess helium as an alternative to carbon dioxide for creating the pneumoperitoneum. Ventilation requirements and carbon dioxide levels were assessed at the beginning and end of laparoscopic cholecystectomy using helium (n = 30) and carbon dioxide (n = 30) pneumoperitoneum. Insufflation with helium did not result in an increase in ventilation requirement although, like carbon dioxide pneumoperitoneum, it was associated with a mean rise in peak airway pressure (of 7 cmH2O; P < 0·001). There was also a 3·2-kPa increase in the alveolar-arterial oxygen gradient with helium (P = 0·006). Carbon dioxide pneumoperitoneum was associated with a significant rise in arterial carbon dioxide levels, despite increasing ventilation. Four patients with helium pneumoperitoneum had surgical emphysema for 5 days. Heli...
As part of a randomized trial, ventilatory and arterial blood gas changes were assessed during op... more As part of a randomized trial, ventilatory and arterial blood gas changes were assessed during open (n = 30) and laparoscopic (n = 30) cholecystectomy. Measurements were made during anaesthesia before the start of surgery and at the time of removal of the gallbladder. Despite an increase in minute ventilation from a mean(s.d.) of 5·7(1·4) to 6·1(1·2) litres, mean(s.d.) arterial carbon dioxide tension (PaCO2) rose from 5·3(0·9) to 6·0(0·9) kPa during laparoscopic cholecystectomy. End-tidal carbon dioxide tension (PE'CO2) had poor precision in predicting PaCO2 (95 per cent interval of agreement −0·61 to 1·93 kPa). Mean(s.d.) peak airway pressure increased from 17(4) to 23(4) cmH2O. The mean PaCO2–PE'CO2 value did not change significantly, although there was significant within-patient variation. Arterial oxygen levels did not change significantly. By comparison, no clinically significant changes in ventilation or blood gas values occurred during open cholecystectomy. In conclus...
Plasma hormone measurements following midazolam administration We were interested to read the exc... more Plasma hormone measurements following midazolam administration We were interested to read the excellent paper by Drs Dawson and Sear (Anaes/hesia 1986; 41: 268 71) since
Several investigators have emphasised the value of the analysis of volume-pressure waveforms as a... more Several investigators have emphasised the value of the analysis of volume-pressure waveforms as an aid to monitoring patients in the intensive care unit (Lewis et al., 1966; Proctor et al., 1970; Hilberman et al., 1975; Wilson, 1976).
Optimum management of the critically ill patient requires frequent monitoring of many variables a... more Optimum management of the critically ill patient requires frequent monitoring of many variables and an ability to detect and act upon significant changes in patient condition at an early stage. This intensive monitoring leads to the rapid accumulation of vast amounts of data in which significant changes in patient condition may remain undetected (Osborne et al. 1968). This type of data collection is ideal for handling by computer, which allows clear presentation of informative and relevant aspects of the information. The improvement in data presentation should result in fewer management errors by the clinician (Jenkins et al. 1968), and in the early detection and correction of adverse trends (Kenny and Campbell 1982).
In the past, the discovery of new drugs often occurred by chance. Over recent years, an increasin... more In the past, the discovery of new drugs often occurred by chance. Over recent years, an increasing knowledge of the mode of drug action and receptor sites has improved our ability to design new drugs. While the mode of action of volatile and intravenous anaesthetic agents remains unclear, neuromuscular blocking agents and opioids have undergone considerable development and design. Drugs are being tailored to produce fewer side effects and to improve desirable properties. As a result, the introduction of new drugs has helped to improve techniques in anaesthesia. The development of remifentanil is an example of this which is discussed. The application of modern technology with target controlled infusions (TCI) for the administration of remifentanil represents further advancement in techniques which may become available to anaesthetists in the future.
Propofol was administered intravenously using a first-order, three-compartment, computer-controll... more Propofol was administered intravenously using a first-order, three-compartment, computer-controlled infusion pump (CCIP) based on the Ohmeda 9000 syringe pump. The CCIP system produced a target-controlled infusion (TCI) based on the estimated blood concentration (EBC). Twenty-five patients undergoing ambulatory surgery completed the study. The induction EBC was 4.72 +/- 0.28 micrograms/ml, and was achieved rapidly with minimal hemodynamic changes. The emergence EBC was 1.55 +/- 0.21 micrograms/ml, and the discharge EBC was 1.06 +/- 0.22 micrograms/ml. The EBC, together with clinical signs, allowed for predictable inductance and emergence from anesthesia using propofol.
There is a growing interest in the potential benefits to be obtained from closed-loop control of ... more There is a growing interest in the potential benefits to be obtained from closed-loop control of drug infusion [1-5]. The most widely available infusion pump which is specifically designed for control by computer is the 929 volumetric infusion pump produced by Imed. The increasing availability of microcomputers suggests that they will be used more frequently to control such pumps. However, difficulties can arise when the attempt is made to establish communication between the computer and the pump [6] and a method employed for this purpose is described in this article. The aim was to provide a simple method of conducting the required communication between the computer and the pump using a high-level language. The commands specified in the high-level language are passed to a machine-code subroutine which organizes transmission to and receives data from the pump.
International Journal of Clinical Monitoring and Computing, 1992
A Psion microcomputer controlled infusion system for alfentanil was assessed for the provision of... more A Psion microcomputer controlled infusion system for alfentanil was assessed for the provision of postoperative analgesia in 14 patients who had undergone aortic bifurcation graft surgery. The system employed a pharmacokinetic model working in real time to deliver any selected target plasma concentration of alfentanil. The alfentanil infusion system was used for a mean time of 39 hours and for 96% of this time, patients were scored as having no pain or only mild pain. Severe pain was recorded for only 0.05% of the study time. The use of a pharmacokinetic delivery system may offer a convenient and simple method of providing postoperative analgesia with alfentanil.
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