Resistive load of laryngeal mask airway and ProSeal laryngeal mask airway in mechanically ventilated patients.
BACKGROUND
The ProSeal Laryngeal Mask Airway (PLMA) ventilation tube is narrower and shorter than the standard Laryngeal Mask Airway (LMA) and is without the vertical bars at the end of the tube. In this randomized, crossover study, PLMA and LMA resistances were compared.


METHODS
Respiratory mechanics was calculated in 26 anesthetized, mechanically ventilated patients with both LMA and PLMA. The laryngeal mask positioning was fiberoptically evaluated. Differences in the respiratory mechanics of the LMA and the PLMA were attributed to the differences between the laryngeal masks.


RESULTS
In the total study population the airway resistance was 1.5 +/- 2.6 hPa.l-1.s-1 (P = 0.005) higher with the PLMA than with the LMA. During the PLMA use, the peak expiratory flow reduced by 0.02 +/- 0.05 l min-1 (P = 0.046), the expiratory resistance increased by 0.6 +/- 1.3 hPa.l-1.s-1 (P = 0.022), and the time constant of respiratory system lengthened by 0.09 +/- 0.18 s (P = 0.023). These differences doubled when the LMA was better positioned than the PLMA, whereas they disappeared when the PLMA was positioned better than the LMA.


CONCLUSIONS
The standard LMA offers a lower resistive load than the PLMA. Moreover, the fitting between the laryngeal masks and the larynx, as fiberoptically evaluated, plays a major role in determining the resistive properties of these devices.
Natalini
G
G
Department of Anesthesia, Intensive Care and Emergency, Casa di Cura Poliambulanza, Brescia, Italy. natalini-giuseppe@poliambulanza.it
Rosano
A
A
Lanza
G
G
Martinelli
E
E
Pletti
C
C
Bernardini
A
A
D000328:Adult; D000399:Air Pressure; D000403:Airway Resistance / Q000502:physiology; D000768:Anesthesia, General; D018592:Cross-Over Studies; D004562:Electrocardiography; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology