Comparative effects of laryngeal mask and tracheal tube on total respiratory resistance in anaesthetised patients.
We compared the effects of the laryngeal mask and tracheal tube on total respiratory resistance in 10 anaesthetised, mechanically ventilated patients undergoing otological microsurgery. The subjects were randomly divided into two groups. In the first group, the tracheal tube (Rüsch) was inserted for the first series of measurements. This was then replaced by a laryngeal mask (Intavent) and a second series of measurements was made during the first hour of operation. In the second group, the same protocol was applied with inverse order in the use of the devices. From the measurement of respiratory flow and pressure at the airway opening, total respiratory resistance was calculated by multiple linear regression. The data were corrected to eliminate the previously determined nonlinear resistance of the two devices. Arterial blood pressure, electrocardiogram, oxygen saturation and end-tidal carbon dioxide concentration were continuously monitored. With the laryngeal mask and the tracheal tube, mean (SE) minute ventilation was 9.4(0.9)l.min-1 and 8.1(0.9)l.min-1, 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 (SE) total respiratory resistance was not significantly different with the two devices (0.61(0.32) and 0.69(0.35) kPa.l-1.s, respectively). Leakage was avoided with the laryngeal mask because the insufflation pressure never exceeded 1.7 kPa except in one patient suffering from severe chronic obstructive pulmonary disease who had a total respiratory resistance of 1.45 kPa.l-1.s. During the first hour of the operation all respiratory variables remained stable irrespective of the device used.
Boisson-Bertrand
D
D
Departement d'Anesthésie, CHRU Nancy, France.
Hannhart
B
B
Rousselot
J M
JM
Duvivier
C
C
Quilici
N
N
Peslin
R
R
D000328:Adult; D000403:Airway Resistance; D000769:Anesthesia, Inhalation; D004423:Ear / Q000601:surgery; D006439:Hemodynamics; D006801:Humans; D007442:Intubation, Intratracheal; D017214:Laryngeal Masks; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D012121:Respiration, Artificial