Anaesthetic Gas Monitor Research Articles

Dedicated monitoring of anesthetic and respiratory gases By Raman scattering

The monitoring of respiratory and anesthetic gases in the operating room is important for patient safety. This study measured the accuracy and response time of a multiple-gas monitoring instrument that uses Raman light scattering. Measurements of oxygen, carbon dioxide, nitrogen, nitrous oxide, halothane, enflurane, and isoflurane concentrations were compared with a gas mixer standard and with measurements made with an infrared anesthetic agent analyzer. Correlation coefficients were all greater than 0.999, and probable errors were less than 0.43 vol% for the gases and less than 0.03 vol% for the volatile anesthetics. Response time was 67 ms with a sample flow rate of 150 ml/min. There was some signal overlap between nitrogen and nitrous oxide and between the volatile anesthetic agents. Such overlap can be compensated for by linear matrix analysis. The Raman instrument promises a monitoring capability equivalent to the mass spectrometer and should prove attractive for the monitoring of respiratory and anesthetic gases in the operating room.

Chemical sensor research at the laboratory of applied physics in Linkoping

Various examples are presented to illustrate the interdisciplinary nature of chemical sensor research at the Linkoping Institute of Technology. At least three goals were followed-developing basic knowledge, developing new sensor ideas, and helping industry to solve specific sensor problems. Among examples presented are: the anaesthetic gas monitor called EMMA; a gas concentrator and separator for use in measuring very small quantities of halogenated hydrocarbons; H2-sensitive Pd-MOS structures for use in leak detection of buried cables and medical diagnostics.

Awareness during Surgery

Patients who experience awareness under surgery may suffer from the post-traumatic stress disorder with its long-lasting psychological damage. Furthermore, there are also media attention and legal consequences. In spite of understanding its causes, it is still occurring worldwide and there are no reports of awareness in the Saudi medical literature. This prospective study was conducted to determine the incidence of awareness when its causes are eliminated and to record patient satisfaction.Surgical patients >4 years old (ASA I-III) admitted to the Armed Forces Hospital, Wadi Al-Dawasir, Kingdom of Saudi Arabia, between October 1998 and November 2002 were included in the study. Patients were given a premedicant with an amnesic effect. Anesthetic equipment with a built-in end-tidal anesthetic gas monitor was checked preoperatively. Minimal anesthetic concentrations of vapors were delivered and monitored. Intraoperative analgesia was provided whenever appropriate. Patients were closely observed for signs of intraoperative awareness under general anesthesia. All patients were interviewed within 24 hours postoperatively on the occurrence of awareness and service satisfaction.There were 4368 patients admitted to the study. Their ages ranged from 14-104 years (mean 40.2 years). All patients were interviewed in the postoperative period. There was no report of awareness during surgery and patient satisfaction score was 100%.Preoperative and intraoperative anesthetic attention to patients presented for surgery, together with the use of modern anesthetic delivery units possessing facilities for monitoring anesthetic gases, and the provision of good analgesia are the most important combination in eliminating awareness during surgery.

Response time of the Narkotest anesthetic gas monitor.

Response time (RT) of the Narkotest anesthetic gas monitor was measured for 7 inhalation anesthetics, using a 5 L/min fresh gas flow (FGF). Time to 63 percent of maximum response (RT63) and to 95 percent of maximum response (RT95) was directly related to rubber/gas and oil/gas partition coefficients. RT95 ranged from 7 seconds for N2O to 843 seconds for methoxyflurane. RT measured at 0.5 L/min FGF was markedly prolonged over RT at 5 L/min. When the Narkotest was placed on the expiratory limbs of circle-absorber breathing circuits, the difference between the calibrated Narkotest reading (Fn) and the mixed expired circuit concentration (Fc) was shown to depend on the rate of increase of the circuit concentration.

Clinical and laboratory evaluation of an expired anesthetic gas monitor (Narko-Test).

A halothane analyzer (Narko-Test) was shown to have a linear response to various concentrations of cyclopropane, fluroxene, Ēthrane, diethyl ether, halothane and methoxyflurane. The factors necessary to convert the analyzer scale readings to the concentrations of the agents were 13, 2.3, 1.46, 1.25, 1.0 and 0.16, respectively. Corrections for saturated water vapor at room temperature and 100 per cent N2O were both 0.3 scale units. When used as a monitor of mixed expired gas in semiclosed or closed systems, the analyzer response was a measure of the anesthetic potency of a single agent or of the combined potency of a mixture of agents. The response to each agent was proportional to its solubility in silicon rubber or brain lipids; hence, the scale units may be regarded as multiples of minimum alveolar concentration (MAC).

A new concept for the continuous monitoring of anesthetic gases. I. Detector theory and clinical uses.

A new concept for the continuous monitoring of anesthetic gases. I. Detector theory and clinical uses.

A new concept for the continuous monitoring of anesthetic gases. II. Halothane: comparison of various vaporizers' outputs.

A new concept for the continuous monitoring of anesthetic gases. II. Halothane: comparison of various vaporizers' outputs.