British journal of anaesthesia
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The use of small endotracheal tubes reduces the trauma of intubation. Ventilator and tracheal pressures were measured during controlled ventilation with various tube dimensions and ventilation volumes. Ventilation with large volumes using small tracheal tubes results in high ventilator pressures. ⋯ Small endotracheal tubes and high ventilation volumes result in a positive tracheal pressure at the end of expiration. The measured end-expiratory pressures are within the limits which might be used therapeutically (in PEEP). The force required to reshape endotracheal tubes of varvious dimensions to an "anatomical" shape was related to the tube dimensions; the beneficial effects of performed, "anatomically shaped" endotracheal tubes can be achieved by using small tubes of standard design.
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The effect of Althesin, diazepam, ketamine, propanidid and thiopentone on the release of acetylcholine was tested at the mouse neuromuscular junction. Althesin, diazepam and thiopentone increased the quantal content of the end-plate potential. Ketamine at low concentration (3.6 micromol litre-1) had a similar effect, but at high concentration (116.7 micromol litre-1) quantal content decreased sharply. ⋯ The increase in quantal content antagonized the effect of postsynaptic depression on the amplitude of the end-plate potential. The lack of enhancement of acetylcholine release appears to explain the in vitro interaction of propanidid with tubocurarine. The diversity of presynaptic actions of these drugs makes it unlikely that this is an important mechanism in producing anaesthesia.