Anaesthesia and intensive care
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Anaesth Intensive Care · Jul 2008
Review Historical ArticleThe origins of the sniffing position and the Three Axes Alignment Theory for direct laryngoscopy.
The Three Axes Alignment Theory and the sniffing position for direct laryngoscopy are the anatomical basis for direct laryngoscopy. This position has been one of the hallmarks of airway management and yet its development is based on a small number of descriptive texts published between 1852 and 1944. This paper explores the origins of direct laryngoscopy and how the sniffing position came to be described. The seemingly incongruent techniques of the rigid bronchoscopist and direct laryngoscopist are discussed from an historical perspective.
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Anaesth Intensive Care · Jul 2008
The performance of Dräger Oxylog ventilators at simulated altitude.
Ventilated patients frequently require transport by air in a hypobaric environment. Previous studies have demonstrated significant changes in the performance of ventilators with changes in cabin pressure (altitude) but no studies have been published on the function of modem ventilators at altitude. This experiment set out to evaluate ventilatory parameters (tidal volume and respiratory rate) of three commonly used transport ventilators (the Dräger Oxylog 1000, 2000 and 3000) in a simulated hypobaric environment. ⋯ Tidal volume and respiratory rate remained constant with the Oxylog 3000 over the same range of altitudes. Changes were consistent with each ventilator regardless of oxygen content or lung model. It is important that clinicians involved in critical care transport in a hypobaric environment are aware that individual ventilators perform differently at altitude and that they are aware of the characteristics of the particular ventilator that they are using.
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Anaesth Intensive Care · Jul 2008
Randomized Controlled TrialThe effect of timing of application of positive end-expiratory pressure on oxygenation during one-lung ventilation.
Many studies have confirmed that applying positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation (OLV) improves oxygenation. Our purpose was to investigate the best time and level of PEEP application. Thirty patients undergoing thoracic surgery were randomised into three groups. ⋯ When PEEP was set to 10 cmH2O, the airway pressure increased significantly (P <0.05). These findings indicate that PEEP applied at the initial time of OLV improves oxygenation most beneficially. Five cmH2O PEEP may produce this beneficial effect without the increase in airway pressure associated with 10 cmH2O PEEP.
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Historically, anaesthetic equipment manufacturers used a number of differently-sized connectors in anaesthetic breathing systems. This gave rise to the potentially dangerous possibility of mismatched taper connections and a failure to create a gas-tight breathing system capable of ventilating a patient. ⋯ The problem was aggravated by a move to adopt a slightly different International Standards Organisation design. By the time that universally-interchangeable connectors were widespread twenty years later disposable breathing systems had replaced the old, heavy metal connectors.
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Anaesth Intensive Care · Jul 2008
Relative reliability of the auditory evoked potential and Bispectral Index for monitoring sedation level in surgical intensive care patients.
Sedation is an important adjunct therapy for patients in the intensive care unit. The objective of the present study was to observe correlation between an established subjective measure, the Ramsay Sedation Scale, and two objective tools for monitoring critically ill patients: the Bispectral Index (BIS) and auditory evoked potential. Ninety patients undergoing major surgery scheduled for postoperative mechanical ventilation and continuous sedation with propofol and fentanyl were selected. ⋯ In conclusion, the auditory evoked potential and BIS monitors revealed an acceptable correlation with the Ramsay Sedation Scale. However, the BIS and auditory evoked potential monitors do not perform adequately as a substitute in the assessment of sedated intensive care unit patients. These monitors could be used as part of an integrated approach for the evaluation of those patients especially when the subjective scales do not work well in the setting of neuromuscular blockade or may not be sufficiently sensitive to evaluate very deep sedation.