In Reply:-Drs. Goto and Uezono are incorrect in stating that the study by Brimacombe et al. [1]was conducted at the same two Australian institutions as the study by Greenberg et al. [2]It was conducted only at Cairns Base Hospital, and Dr. Berry did not directly participate in the clinical aspects of the trial.
We disagree that the results of these trials are “contradictory.” In terms of ease of placement, time taken to achieve an adequate airway, first time placement success rates, airway sealing pressure, the number of airway interventions required, and postoperative jaw and neck pain, both trials showed that the laryngeal mask airway (LMA) was the better device. The main contradictory result was that the multicenter trial showed that the cuffed oropharyngeal airway (COPA) was associated with a lower incidence of oropharyngeal trauma and that the single-center trial had a higher incidence. We consider the postoperative data from the single-center trial more reliable because data collection was double-blinded. Although superficially similar, the two trials were not methodologically identical, and comparisons should be made cautiously. Notable differences were that the multicenter trial involved 62 variably experienced investigators conducting variable case numbers, more than 20 data collectors, unequal-sized groups, total intravenous anesthesia with propofol, and emergence either in the operating room or the post- anesthesia care unit. The single-center trial involved four experienced investigators conducting 30 patients each, equal-sized groups, one highly experienced data collector (more than 100 observed cases from the first trial) backed up by video recordings that were analyzed independently, isoflurane for maintenance, and emergence only in the operating room. Airway stability in different head and neck positions and the best position for emergence were only investigated in the single-center trial. Definitions for study end-points were frequently different. For example, in the multicenter study an “effective airway” was not defined, but in the single-center study it was defined as an airway sealing pressure >or= to 10 cm H2O and maintenance of SpO(2) as >or= to 90% with FIO(2) 0.3-0.4. In the single-center study, airway interventions were classified into major and minor and cataloged for every 5-min epoch, but no such time base was used in the multicenter study.
Drs. Goto and Uezono suggest that some of the difficulties that occurred with the COPA in the multicenter study were related to poor performance at the Australian study sites. In fact, the performance was significantly better at the Australian study sites in all aspects of airway management for the COPA, and most aspects of airway management for the LMA (Table 1). As discussed in the original paper, the higher incidence of problems at John Hopkins may reflect the use of more investigators, a lower level of clinical experience, differences in anesthesia practice, or difficulties in following the study protocol. It should be noted that although the overall performance varied between study sites, the relative performance between the devices was generally similar at each study site.
Table 1. Incidence of Problems for the Laryngeal Mask Airway (LMA) and Cuffed Oropharyngeal Airway (COPA) between the Australian and U.S. Study Sites
Finally, Dr. Greenberg invented the COPA, and therefore his clinical involvement in the multicenter study for FDA approval was not recommended. Drs. Brimacombe and Berry did not invent either device and were allowed to participate in the multicenter trial. Their performance was comparable with other Australian investigators as was Dr. Brimacombe's performance in the single-center study.
Joseph R. Brimacombe, M.B., Ch.B., F.R.C.A., M.D.
Department of Anaesthesia and Intensive Care; Cairns Base Hospital; Cairns, Australia;100236,2343@compuserve.com
A. Berry, M.B., Ch.B., F.R.C.A.
Department of Anaesthesia and Intensive Care; Nambour General Hospital; Nambour, Australia
(Accepted for publication December 14, 1998.)
