Minitracheotomy Seldinger—assessment of a new technique

A multicentre, prospective study of 26 patients was undertaken for the assessment of insertion of minitracheotomy tubes by the Seldinger technique. The technique of insertion is described. There were two misplacements, three blockages of the inserting Tuohy needle with fat, and six cases of difficulty in passing the minitracheotomy tube.     

Drawover anaesthetic systems

The factors that determine the inspired oxygen concentration delivered by drawover anaesthetic systems were studied in the laboratory and in anaesthetised patients. The inspired oxygen concentration is dependent upon oxygen flow, reservoir volume and total ventilation; respiratory rate and inspiration:expiration ratio have a small influence. A reservoir of at least of 1 m corrugated tube (internal volume 415 ml) makes optimal use of a 4 litres/minute oxygen flow. Delivery of a safe inspired oxygen concentration can be ensured with economical oxygen flows.     

Microcomputer-based data acquisition system for clinical research

We have described a computerized data acquisition system for clinical investigation that can record over fifty physiologic variables from up to twenty-four electronic monitors. The information is acquired by a personal computer using RS-232C serial communications and analog-to-digital conversion. In its present configuration the system records information from a Spacelabs 500 series physiologic monitor, Hewlett-Packard physiologic monitor with the Careport computer interface, SARA mass spectrometer, Nellcor pulse oximeter, Neurotrac processed EEG, Lawrence cardiac output monitor, Hewlett-Packard capnometcr, and Bourns spirometer. The software can be easily modified to accommodate other physiologic monitors. The system records parameter or waveform information and writes the data into a file that can be accessed by commercially available graphical and statistical packages. The data acquisition system is easy to use, transportable, and inexpensive.     

Minitracheotomy

Minitracheotomy is a simple percutaneous technique of tracheal cannulation using a small bore tube. It allows efficient tracheobronchial toilet while preserving glottic function. Examples of its use in the intensive therapy unit are described.     

Observations on deliberate dural puncture with a Tuohy needle: depth measurements

Observations were made during the use of a Tuohy needle to perform deliberate dural puncture for the insertion of lumbar drains to improve operating conditions for intracranial aneurysm surgery. The most striking finding was the distance from identification of the epidural space to penetration of the dura. We postulate that this was because of tenting of the dura by the blunt Tuohy needle. This was facilitated by the absence of a negative epidural space pressure because an open system was used, which allowed time for pressure equilibration. This minimised the reactive forces across the dura. Aspiration and rotation of the Tuohy needle revealed dural puncture in some cases.     

Low-flow anaesthesia

An 8-week survey was conducted to determine whether the introduction of low-flow anaesthesia (a fresh gas flow of 4 litres/minute or less) into routine use would be acceptable to members of a representative anaesthetic department and if the consequent reduction in use of volatile anaesthetics would result in financial savings. The hourly consumption of the volatile agents was measured during anaesthesia conducted using either conventional or low fresh gas flows. Anaesthetists' acceptance of low-flow anaesthesia was assessed using a questionnaire. Data were gathered on 286 patients undergoing inhalational anaesthesia for routine operative procedures. A 54.7% reduction in the consumption of isoflurane and a 55.9% reduction in that of enflurane was found. Of the 28 anaesthetists at the hospital, 21 would use low-flow anaesthesia routinely. The routine use of low-flow anaesthesia would therefore be acceptable and could result in annual savings of 26,870 pounds at Northwick Park Hospital.     

Selective bronchial intubation for one lung anaesthesia in thoracic surgery

A new method for one lung anaesthesia in thoracic surgery is described. Separate lung ventilation is obtained with selective main bronchus intubation, by means of an appropriate cuffed tube inserted through a standard orotracheal tube. Ventilation is carried out separately through the bronchial tube on one side and the residual tracheal tube lumen on the other side. This method greatly simplifies the technique of bronchial intubation and offers many advantages over commercially available double-lumen tubes.     

Pressure generated during insertion of lumbar epidurals. A comparison with the Portex epidural injection simulator

The aim of this study was to measure pressures exerted during insertion of lumbar epidurals in obstetric patients. The pressures were compared with those obtained when the Portex epidural injection simulator was used, and were significantly greater when a saline technique was used compared to those when air was used (p less than 0.05). There were no differences between the pressures obtained with the simulator and those measured in vivo.     

A comparison of the performance of 20 pulse oximeters under conditions of poor perfusion

The performance of 20 pulse oximeters with finger probes was evaluated by comparison of their readings with directly measured arterial blood oxygen saturations. The samples were taken from patients who had undergone cardiac surgery under hypothermic cardiopulmonary bypass and had poor peripheral perfusion. The mean difference (bias, accuracy), standard deviation (precision) and drop-out rate for each pulse oximeter was determined. An overall ranking of performance of each pulse oximeter was calculated using five criteria (accuracy, precision, number of readings within 3% of standard, percentage of readings given within 3% of standard, expected overread limit in 95% of cases). Two pulse oximeters achieved a combination of accuracy and precision such that 95% of measurements would be expected to be within 4% of the co-oximeter value; these two also had the lowest drop-out rate.     

Faulty Superset plastic catheter mounts

Nine Superset (Intersurgical Ltd) single-use corrugated plastic catheter mounts were found to be faulty in a boxed batch of 75. The manufacturer's meticulous system of batch coding enabled the source of the problem to be traced quickly. Sporadic faults must be expected to occur in mass-produced disposable equipment and the unusual origin of the defect reported in these catheter mounts is testimony to the way unexpected events can prejudice the most carefully regulated quality control. It is emphasised that the user can help safeguard the community by ensuring that stock is used in strict rotation and that batch numbers are accurately reported when faults arise.