Acta anaesthesiologica Scandinavica
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Acta Anaesthesiol Scand · Jan 1978
Flow requirements in the Hafnia modifications of the Mapleson circuits during spontaneous respiration.
The Mapleson A, B, C and D circuits can be changed into non-polluting circuits by employing continuous gas evacuation directly from the circuit, via an ejector flowmeter (Jørgensen 1974); Mapleson A and C circuits with this modification have been described previously as the Hafnia A and C circuits (Christensen 1976, Thomsen & Jørgensen 1976). If evacuation from a closed reservoir is employed, total removal of the expired and surplus gases from the operating theatre is obtained (Jørgensen & Thomsen 1976). There will be resistance to expiration in all the circuits with a relief valve for the discharge of surplus gas. ⋯ As in any other circuit, the relief valve remains open except during controlled ventilation. A dumping valve may also be included as a safeguard against low pressures (Jørgensen & Thomsen 1976). The flow requirements of the Hafnia B and D circuits and the corresponding Mapleson circuits have been studied in conscious, spontaneously breathing subjects, and the results are discussed in relation to the flow requirements of other semi-closed system.
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Acta Anaesthesiol Scand · Jan 1978
Cerebral autoregulation in unconscious patients with brain injury.
In 18 unconscious patients with traumatic brain injury, the cerebral autoregulation was tested during the first 2-3 weeks after the acute trauma. Regional cerebral blood flow (rCBF) was measured by the intra-arterial 133xenon washout method before and after an increase of about 20% in the mean arterial blood pressure (MABP) by angiotensin. The difference between MABP and intraventricular pressure (IVP) was used as cerebral perfusion pressure (PP). ⋯ Regional loss of autoregulation indicated by a 20% flow increase was observed in 29 out of 35 studies (83%), while hemispheric loss of autoregulation was observed in only one study. The results of the autoregulation tests were unrelated to the clinical outcome, the presence of brain-stem lesion, and the ventricular fluid pH, lactate and lactate/pyruvate ratio. In repeated studies, a gradual normalization of the autoregulation was observed about 5 days after the acute trauma.
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Three anaesthetic circuits for use in nose-piece application of inhalation analgesia are described. An ejector flowmeter is used for the scavenging of overspill gas.
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Acta Anaesthesiol Scand · Jan 1978
Arterial oxygenation during artificial ventilation. The effect of airway closure and of its prevention by positive end-expiratory pressure.
Airway closure and arterial blood gases were measured in 11 healthy subjects both before and during anaesthesia with artificial ventilation, prior to routine surgery. The functional residual capacity was then increased by positive end-expiratory pressure (PEEP), so that ventilation took place at a lung volume where no airway closure was present, and the effect on arterial oxygenation was again investigated. ⋯ There was no improvement in arterial oxygenation on increasing functional residual capacity (FRC) in either group. It may well be that this failure to improve oxygenation was due to a deleterious effect of PEEP on the circulation, even though the PEEP was the minimum required to abolish airway closure.