Comparative effects of laryngeal mask and tracheal tube on total respiratory resistance in anaesthetised patients

Abstract

SummaryWe compared the effects of the laryngeal mask and tracheal tube on total respiratory resistance in I0 anaesthetised, mechanically ventilated patients undergoing otological microsurgery. The subjects were randomly divided into two groups. In the first group, the tracheal tube (Riisch) 9.4(0.9)l.min-' and 8.1 (0.9) respectively). Leakage was avoided with the laryngeal mask because the insuflation pressure never exceeded 1.7 kPa except in one patient suflering from severe chronic obstructive pulmonary disease who had a total respiratory resistance of 1.45 kPa.1-'.s. During the first hour of the operation all respiratory variables remained stable irrespective of the device used. l.min-', respectively for end-tidal carbon dioxide concentrations between 3.6 and 4.1%. Although the glottic resistance was included in the measurement performed with the laryngeal mask but not with the tracheal tube, mean ( S E ) total respiratory resistance was not significantly dazerent with the two devices

Additional inspiratory resistance imposed by the laryngeal mask airway: in vitro versus in vivo comparison

“…However, Ferguson and colleagues only tested spontaneously breathing patients and did not specify any inspiratory flow. Boisson-Bertrand et al investigated the effects of the LMA and the tracheal tube on total respiratory resistance in 10 anaesthetised patients and concluded that LMA and tracheal tube size 8 and 8.5 additional resistances were comparable; they did not measure resistance in vivo directly [22]. In our study we calculated resistance in vitro and in vivo directly; the latter was higher for any flow we tested mainly because of an increase in the K 2 value.…”