British journal of anaesthesia
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The actions of alcuronium, vecuronium and tubocurarine have been studied in the isolated forearms of six healthy, non-anaesthetized volunteers. The responses of adductor pollicis were measured during onset and recovery of neuromuscular block for each agent. There was a drug-related disparity between mechanomyogram (MMG) and electromyogram (EMG) measurement of the first response of the train-of-four (T1) and of the ratio of the fourth (T4) to the first response (TOF ratio). ⋯ Analysis of variance of the differential fade loops failed to show a drug-related effect. We conclude that care should be taken in assuming interchangeability between MMG and EMG measurement of T1. Relationships between T1 and TOF ratio derived during recovery do not necessarily apply during onset and may lead to error in estimating the degree of muscle relaxation.
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We have assessed a Venturi driven device for delivering continuous positive airway pressure (CPAP) using a reservoir bag and expiratory valve under conditions of continuous flow and simulated spontaneous breathing. The system performed well and was economical, consuming only 3.5 litre min-1 of fresh gas. One Venturi was partially blocked and performed inadequately, but the function of a second one was close to the manufacturer's specification (inspired oxygen 33%, flow 20 litre min-1 against end-expiratory pressures of 0-1.8 kPa). ⋯ The characteristics of the expiratory valve approached those of a threshold resistor. Small fluctuations in airway pressure occurred at all settings of CPAP and decreased with the increasing compliance of the circuit at higher values of CPAP. The method provided to monitor the airway pressure was inaccurate and overestimated the true pressure by 20% at pressures greater than 1 kPa.