Two cases of difficult removal of external jugular vein catheters and their probable cause are discussed.
Summary S~w i t y -o t w udult patients Key wordsEquipmmt; cuffs. tracheal.The inflatable cuff of a tracheal tube has two functions. It should prevent aspiration of pharyngeal contents into the trachea and it should allow leak-free positive prcssure ventilation. It is widely known that cxccssivc prcssurc on the tracheal mucosa can result in trauma' and many methods of cuff management and types of cuff design have been described2 in order to minimise this. Measurement of cuff pressure is rarely performed in British anaesthetic practice3 but such measurements may help to prevent accidental overinflation. In order to assess the degree of overinflation it was decided to measure cuff pressures generated during routine clinical practice and also to rncasure the minimum cuff pressure required to produce a leak-free tracheal seal in the same patients.The aims of the present study were thus two-fold: to assess syringe inflation of thc tracheal tubc cuff by measuring thc initial cuff prcssurc (ICP) after inflation by ;I traincd assistant; and to measure the minimum cuff pressure (MCP) compatible with the absence of leakage past the cuff as detected by auscultation ovcr the trachca. MethodsTwo instrurncnts were uscd, thc first mcasurcd and thc second incasured and controllcd. Thc measurement of ICP w a s hy a portable battery-powered pressure transducer (I('T series 1800) with built-in amplifier and digital display.The traiisduccr has a low compliance with a small internal volume (150 PI) so that conncxion to a previously inflated cuff enablcs the pressurc within thc cuff to bc dekrmined. The response is linear over the range 0-26.6 kPa and a built-in reference voltage enables thc calibration to be checked. The second instrument, thc Cardifl Cuff Controller." is an electropneumatic device which incorporates the same pressure transducer for measurement but it has an additional facility to maintain a constant tracheal tube cuff pressure at a preset value in the range 0.7--20 kPa. Both thcsc instrumcnts were calibrated against a mercury manometer over the range 0-26.6 kPa and were linear to within 0.133 kPa over this range.Seventy-one patients schcduled to undergo rlective surgery were studied and their tracheas were intubatcd aftcr induction of anaesthesia and musclc paralysis. Portex Rluc Line orotracheal. disposable tubes with standard cuffs were used, 9-min for adult malcs and 8-mm for adult females; the cuff was inflatcd by a trained assistant using a 10-ml syringe via a three-way tap. Air was hjcctcd until no gross leakage was audible. Neither of the instruments was connected to the tracheal tube at this stage in order that the normal routine was not influcnccd in any way.The initial cuff pressure (ICP) was incasured using thc low-compliance transducer after which the Cardiff Cuff Controller was connectcd and set a t 4.0 kPa. If'no leak was present at 4.0 kPa the minimum cuff pressure (MCP) was
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