The delivery of oxygen by a venturi T piece

We have evaluated the performance of the Intersurgical 40% Oxygen Recovery T-Kit in ten healthy volunteers. Inspired oxygen and end-tidal carbon dioxide concentrations were measured during normal respiration and with variations in respiratory rate and depth. The performance of the device was then studied after modifications to the inspiratory limb, the expiratory limb and the arrangement of the attachments to the T piece. The standard arrangement of the T piece was associated with inadequate inspired oxygen concentration (31.9 +/- 0.6%), independent of respiratory rate and depth. All three modifications increased the inspired oxygen concentration, the longer expiratory limb to 34.6% (p < 0.01) and the altered T piece arrangement to 37.3% (p < 0.01). The highest inspired oxygen concentration of 40.3% (p < 0.01) was obtained by increasing the length of the inspiratory limb.