Anaesthesia and intensive care
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Anaesth Intensive Care · May 1992
Alveolar oxygenation and mouth-to-mask ventilation: effects of oxygen insufflation.
The effect on alveolar oxygen fraction (FAO2) of insufflating oxygen under a mask (or through an inflow nipple provided in the mask) during simulated mouth-to-mask ventilation was investigated using a lung model. A variety of commercially produced masks were evaluated. Two patterns of artificial ventilation were applied: 1. 500 ml tidal volume at 20 breaths per minute, and 2. 900 ml tidal volume at 12 breaths per minute. ⋯ The relationship between oxygen flow and FAO2 was not linear however, and an oxygen flow rate of 10 l/min was adequate to generate FAO2's around 50% with either ventilatory pattern. The equilibrium FAO2 achieved was greater with smaller tidal volumes and with larger mask deadspace. We also found that several breaths were required for equilibration of FAO2 during each trial, supporting recommendations that several breaths should be given on commencement of artificial ventilation during cardiopulmonary resuscitation.
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Anaesth Intensive Care · May 1992
The relationship between a person's height and appropriate endotracheal tube length.
The relationship between a person's height and the dimensions of that person's upper airways has been studied in adult subjects. Using this relationship, formulae have been derived which predict appropriate lengths for endotracheal tubes. The formulae are as follows: 1. ⋯ Orotracheal tube (teeth to mid-point of trachea + 3 cm) = Subject height (cm)/10 + 5 3. Nasotracheal tube (external naris to mid-point of trachea) = Subject height (cm)/10 + 8 These formulae are not foolproof but provide a useful working guide. All usual comfirmatory tests of correct placement should be employed.
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Anaesth Intensive Care · May 1992
Randomized Controlled Trial Comparative Study Clinical TrialThe addition of pethidine to epidural bupivacaine in labour--effect of changing bupivacaine strength.
The effects of varying the strength of bupivacaine used in epidurals for the relief of labour pain was examined. The trial randomly allocated sixty women in the first stage of labour to one of three groups. All women were of ASA status 1 or 2 and had uncomplicated pregnancies. ⋯ This study suggests that when epidural pethidine 25 mg is added to local anaesthetic solutions of bupivacaine, adequate analgesia for the first stage of labour is achieved with the 0.125% bupivacaine solution. The use of stronger solutions of bupivacaine achieves no greater degree of analgesia nor longer duration of action, although the onset of analgesia may be faster with the stronger solutions. Further investigations are needed to determine if 25 mg of pethidine is the best choice of dose to use under these circumstances.