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Biomedical subjects

R Ooi

Publications and source records attributed to R Ooi.

At least 19 recordsLinked to original sources
PubMed2000

Distribution of aldoxime dehydratase in microorganisms.

The distribution of phenylacetaldoxime-degrading and pyridine-3-aldoxime-degrading ability was examined with intact cells of 975 microorganisms, including 45 genera of bacteria, 11 genera of actinomyces, 22 genera of yeasts, and 37 genera of fungi, by monitoring the decrease of the aldoximes by high-pressure liquid chromatography. The abilities were found to be widely distributed in bacteria, actinomyces, fungi, and some yeasts: 98 and 107 strains degraded phenylacetaldoxime and pyridine-3-aldoxime, respectively. All of the active strains exhibited not only the aldoxime-dehydration activity to form nitrile but also nitrile-hydrolyzing activity. On the other hand, all of 19 nitrile-degrading microorganisms (13 species, 7 genera) were found to exhibit aldoxime dehydration activity. It is shown that aldoxime dehydratase and nitrile-hydrolyzing activities are widely distributed among 188 aldoxime and 19 nitrile degraders and that the enzymes were induced by aldoximes or nitriles.

Bacteria↗
PubMed1998

Isolation and characterization of a bacterium possessing a novel aldoxime-dehydration activity and nitrile-degrading enzymes.

A bacterial strain capable of utilizing E-pyridine-3-aldoxime as a nitrogen source was isolated from soil after a 4-month acclimation period and was identified as Rhodococcus sp. The strain contained a novel aldoxime dehydration activity that catalyzed a stoichiometric dehydration of E-pyridine-3-aldoxime to form 3-cyanopyridine. The enzyme activity was induced by various aldoximes and nitriles. The strain metabolized the aldoxime as follows: E-pyridine-3-aldoxime was dehydrated to form 3-cyanopyridine, which was converted to nicotinamide by a nitrile hydratase, and the nicotinamide was successively hydrolyzed to nicotinic acid by an amidase.

Amidohydrolases↗
PubMed1997

New agents, the circle system and short procedures.

Sevoflurane, desflurane and isoflurane were compared using a circle system in 97 patients undergoing short surgical procedures. Using initial high flows, the time intervals to equilibration between inspired and end-expired agent concentrations were measured; equilibration was defined as FE/FI = 0.8. The mean (SD) times obtained for sevoflurane, desflurane and isoflurane were 8.2 (2.1) min, 3.8 (0.7) min and 19.7 (6.5) min, respectively. These times were significantly different from each other (p < 0.0001). After equilibration total flow were reduced to 500 ml.min-1; at these flows the initial decline in end-expired agent concentration was minimal with desflurane, intermediate with sevoflurane and greatest with isoflurane. Both desflurane and sevoflurane are appropriate for efficient use of the circle system during short anaesthetics.

Adult↗
PubMed1996

Anaesthesia and the Internet.

The Internet is a network of computers that allows rapid transfer of information throughout the world. The number of medical, and particularly anaesthetic, resources is rapidly increasing. This article briefly describes the Internet and its features which may be of interest to anaesthetists and intensivists in the United Kingdom, together with some of the tools for working with them.

Anesthesia↗
PubMed1993

Extra inspiratory work of breathing imposed by cricothyrotomy devices.

Using a lung model for spontaneous ventilation, we have assessed the additional work of inspiration imposed by a variety of cannulae ranging from the 12- and 14-gauge intravascular cannulae to the 8.0-mm i.d. adult tracheostomy tube. Work (W) ranged between 9 and 2262 mJ litre-1 and power (W) between 0.2 and 37.7 mW litre-1 min; the smallest values were obtained with the 8.0-mm i.d. adult tracheostomy tube and the 12- and 14-gauge intravascular cannulae gave the largest values. With any given cannula, W and W were influenced by ventilation (tidal volume and frequency) and ventilatory wave pattern of the analogue lung. The results obtained from the 12- and 14-gauge cannulae represent what is probably an excessive inspiratory workload, whereas the other four devices (Portex MiniTrach, 4.0, 6.0 and 8.0 tracheostomy tubes) may be suitable in the short term for relieving airway obstruction and compatible with spontaneous ventilation.

Cricoid Cartilage↗
PubMed1993

Fresh gas flow requirements during spontaneous ventilation: fresh gas flow to total ventilation ratio or ml kg-1 min-1?

Both the performance of breathing systems and recommendations for the fresh gas flows to be used in patients breathing spontaneously can be expressed in ml kg-1 min-1 or fresh gas: total ventilation ratio (VF:VE). We have examined the relationship between these two descriptions. The data of 106 subjects (awake volunteers and anaesthetized patients) were retrieved from the archives of previous work performed in our department. The two methods of describing the requisite fresh gas produced different results, with correlation coefficients (r) between the methods of r = 0.69 and r = 0.49 for the awake and anaesthetized groups, respectively. The results of the multiple regression models suggest that both baseline total ventilation and body weight may be used to predict the fresh gas flow requirements, but residual analysis did not discriminate which method was a better predictor.

Adolescent↗
PubMed1993

The parallel Lack anaesthetic breathing system.

The parallel Lack system is a new modification of the Mapleson A system comprising separate inspiratory and expiratory tubes. To determine that the function of the system was that anticipated of a Mapleson A, the fresh gas flow requirements to prevent rebreathing during spontaneous ventilation were assessed in three situations: (1) a lung model (2) conscious volunteers and (3) anaesthetised patients. Two sets of criteria to define rebreathing were used; (A) those based on changes in ventilation or end-expired carbon dioxide tension and (B) minimum inspired carbon dioxide tension. Using A, rebreathing occurred at a fresh gas flow to minute ventilation ratio (VF/VE) of 0.75 for the lung model, and 0.73 for conscious volunteers. These results were comparable to those obtained for a Magill attachment. They were also close to the point at which mechanical dead space began to increase in the lung model. Criteria B gave much lower values for the onset of rebreathing. Rebreathing was present by criteria A in five of the six anaesthetised patients at a fresh gas flow of 60 ml.kg-1.min-1 (VF/VF of 0.78). The results confirm that the parallel Lack behaves as a Mapleson A system. The resistance to breathing posed by the parallel Lack was also comparable to the Magill system.

Adult↗
PubMed1993

The additional work of breathing imposed by Mapleson A systems.

The additional work attributable to breathing through five Mapleson A anaesthetic breathing systems (Magill, Lack, Parallel Lack, Humphrey ADE and Enclosed Magill) was studied using a lung model. With all five systems, the additional work was found to be a function of fresh gas flow, respiratory flow as well as system geometry. Within the range of fresh gas flow and respiratory flow studied, the additional work ranged between 80 mJ.l-1 and 182 mJ.l-1. Expiratory work was always greater than the inspiratory workload. Increasing fresh gas inflow into the system increases expiratory work, both resistive and elastic components. The Magill system posed the least work expenditure. The values for the additional work obtained with the lung model were of the same order of magnitude when measurements were taken in volunteers.

Adult↗
PubMed1992

A high flow semi-open system for preoxygenation: an evaluation.

We have compared an alternative breathing system for preoxygenation comprising a Hudson face mask with high oxygen inflow (48 litre min-1) and a Mapleson A breathing system (100 ml kg-1 min-1). The study consisted of two parts: the first involved adult volunteers (10 male, seven female) and the second part used a lung model for spontaneous ventilation with a sinusoidal ventilatory wave pattern. In the volunteers, preoxygenation was achieved at mean times of 138 (SD 31.3) s and 164 (SD 36.7) s with the high flow semi-open and Mapleson A systems, respectively. In the lung model, at peak inspiratory flow rates of 30 and 40 litre min-1, the preoxygenation times were 139 and 120 s, respectively, with the semi-open system and 167 and 156 s with the Mapleson A system. The high flow semi-open system may be an alternative for current techniques, provided peak inspiratory flows are not excessive.

Adult↗
PubMed1992

Nitrous oxide administration using commonly available oxygen therapy devices.

Administration of nitrous oxide is useful for providing sedation and analgesia. The therapeutic range for nitrous oxide is 20-30%. Several oxygen treatment devices have been used for administering nitrous oxide, but little is known about the concentrations of nitrous oxide and oxygen delivered to the trachea. We have studied this, using an analogue lung model, with several oxygen therapy devices. With a 1:1 nitrous oxide-oxygen mixture in the primary flow for all systems, end-expired nitrous oxide concentrations varied between 6.5% and 34.3%. Therapeutic concentrations were produced using the Hudson (nominal oxygen concentration 60%) fixed-performance mask, the variable performance Hudson mask at 4 litre min-1, the MC masks at 4 and 6 litre min-1 and the nasal prongs at 6 and 8 litre min-1. Simultaneous end-expired oxygen concentrations for all devices tested were within a safe range.

Analgesia↗
PubMed1992

An evaluation of oxygen delivery using nasal prongs.

Oxygen delivery using nasal prongs was assessed using a lung model for spontaneous ventilation. The analogue lung was attached to a manikin, which provided a model of the 'face and pharynx' to which the nasal prongs were applied. Oxygen concentrations were measured in the model trachea at varying fresh gas inflow and peak inspiratory flows. The study demonstrated enormous variability in the both the peak-inspired (26.3-90.0%) and end-expired concentrations (25.2-78.6%) of oxygen delivered to the trachea. There was a regular relationship between the ratio of peak inspiratory flows, expressed over fresh gas inflow and the end-expired oxygen concentrations which could allow estimation of inspired oxygen concentration.

Evaluation Studies as Topic↗
PubMed1992

Pre-oxygenation: the Hudson mask as an alternative technique.

The use of a simple oxygen facemask (Hudson) with high oxygen inflow (48 l.min-1) was investigated as a technique for pre-oxygenation, comparing it with the Magill system (oxygen flow: 100 ml.kg-1.min-1). One hundred and thirty-eight patients scheduled for elective gynaecological and orthopaedic surgery were studied: group 1, Hudson mask and group 2, Magill system (ASA 1-2, n = 107); group 3, Hudson mask and group 4, Magill system (ASA 3, n = 30). Pre-oxygenation was assessed by measuring the times to 97%, 95% and 93% arterial desaturation (finger pulse oximetry) following 3 min of pre-oxygenation. The times taken to achieve these end-points in all the study groups suggest that the Hudson mask offers an alternative technique for pre-oxygenation.

Adult↗
PubMed1992

Nitrous oxide-oxygen analgesia: the performance of the MC mask delivery system.

Nitrous oxide administration via an oxygen facemask such as the Mary Catterall (MC) is an accepted technique for supplementing regional anaesthesia. This study assessed the range of nitrous oxide and oxygen concentrations delivered to the trachea using a mechanical lung model. The inspired concentrations of these two gases were determined by the total fresh gas inflow rates, their concentrations in the fresh gas mixture and the peak inspiratory flow rate of the analogue lung. A 1:1 nitrous oxide-oxygen mixture in the fresh gas with an inflow rate of 4-6 l/min is recommended to ensure adequate oxygen delivery into the trachea as well as achieving the therapeutic concentrations of nitrous oxide (20-30%).

Analgesia↗