SummaryA laboratory study of a widely available heat and moisture exchanger marketed for paediatric use was undertaken. The deadspace, measured by volume displacement, was 12 ml, similar to that of a standard catheter mount for paediatric use. Pressure drop across the device was measured at several different flows in Jive samples of the device in both the dry and wet state.Calculated resistance proved to be markedly lower when compared with that of other anaesthetic equipment such as tracheal tubes, and with similar humidijcation devices for paediatric use.
In a randomized prospective study of 150 patients, we compared two porous-tipped, finned leads, one with a vitreous carbon tip (surface area = 12 mm2) and the other with an Elgiloy tip (surface area = 8 mm2). We assessed the acute and chronic stimulation thresholds and the ease of implantation of the two leads. The acute current thresholds for the vitreous carbon and Elgiloy-tipped leads were 1.7 +/- 0.5 (+/- SD) mA vs. 1.1 +/- 0.4 mA (0.25 ms pulse width), 1.3 +/- 0.5 mA vs. 0.9 +/- 0.3 mA (0.5 ms), and 1.0 +/- 0.3 mA vs. 0.8 +/- 0.3 mA (0.75 ms), respectively (P less than 0.0005). Impedance at implantation was 473 +/- 121 ohms and 716 +/- 285 ohms (P less than 0.0005) for the carbon-tipped and Elgiloy-tipped leads, respectively. The R-wave amplitudes were 10.2 +/- 5.1 volts and 6.8 +/- 3.0 volts, respectively (P less than 0.0005). Both leads were easy to implant and showed low stable chronic thresholds from 3 weeks after implantation, at which time the stimulation threshold was 1.9 +/- 1.0 volts vs. 1.5 +/- 0.6 volts with the implanted voltage-variable generators and 1.8 +/- 0.8 mA vs. 1.6 +/- 0.6 mA with the implanted current-variable generators. Reoperation for displacement was required for two of the 87 (2.3%) carbon-tipped and 2 of the 67 (3.2%) Elgiloy-tipped leads. There was no exit block nor any other lead-related complication. We conclude that both leads have similar and satisfactory performance.
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