Acta anaesthesiologica Scandinavica. Supplementum
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The effects of high frequency asymmetric airway oscillations on mucus clearance were evaluated in excised tracheas of sheep, in an animal model of excessive mucus production, and in patients with bronchiectasis. Asymmetric high frequency ventilation (15 Hz) with expiratory biased flow profiles (expiratory peak-flow greater than inspiratory peak-flow) could move mucus droplets towards the pharynx in rigid and flexible tracheas by gas-liquid interaction. In rigid tracheas the mucus was transported towards the periphery of the model lung if the oscillations were inspiratory biased. ⋯ During forced expiration inward bulging of the posterior membranes of trachea and bronchi occurred at the negative pressure phase of the oscillations. This event was associated with increased appearance of sputum in the central airways. We conclude that high frequency ventilation with asymmetric flow profiles applied via tube or mouthpiece might be an effective future treatment of mucostasis.
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Acta Anaesthesiol Scand Suppl · Jan 1989
Gas flow distribution and tidal volume during distal high frequency jet ventilation in dogs.
During distal high frequency jet ventilation (HFJV) in anaesthetized healthy dogs gas flows were recorded at the proximal end of the open tracheal jet tube. Spirometer measurements of minute volumes with and without entrainment were made. ⋯ From these the effective minute volume, that is the minute volume of fresh gas entering the lungs, was calculated, as well as tidal volume. The results show that entrainment volumes are relatively small in an open system of distal HFJV and that at the same time bypass can (nearly) completely eliminate the effect of entrainment on tidal volume.
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Blood loss up to 10-15% of the total blood volume can be substituted by mere crystalloids. A quicker and more stable volume replacement can be accomplished with colloid solutions. Combination of artificial colloids (e.g., dextran 60, dextran 70 or hydroxyethyl starches with high degree of hydroxyethylation) with crystalloids (isotonic balanced solutions) produces a long lasting volume effect. Due to dose limitation recommendations for the artificial colloids, volume substitution may be continued, at a later stage, by albumin.