Title: A comparison of the Supreme laryngeal mask airway with the Proseal laryngeal mask airway in anesthetized paralyzed adult patients: a randomized crossover study. Registrationnumber: Not reported.
Source: MEDLINE (through PubMed)
Reference: Tham HM, Tan SM, Woon KL, Zhao YD. Can J Anaesth. 2010 Jul;57(7):672-8. doi: 10.1007/s12630-010-9312-6. Epub 2010 Apr 22.
Abstract: PURPOSE: The Supreme laryngeal mask airway (SLMA) is a new single-use advanced form of the Proseal laryngeal mask airway (PLMA). This study tested the hy- pothesis that the SLMA is equally as effective as the PLMA as a supraglottic ventilato- ry device in anesthetized paralyzed adult patients. METHODS: Size 4 SLMAs and PLMAs were compared in a randomized crossover study involving 60 patients aged 21-75 yr and American Society of Anesthesiologists physical status I and II. Once the patients were anesthetized and paralyzed, the SLMA and the PLMA were inserted into each patient in random order. The primary outcome measure was the laryngeal seal pressure (LSP) at an intracuff pressure of 60 cm H(2)O. Secondary outcome measures included the ease of inserting the laryngeal mask airway devices (LMADs) and the fibreoptic position of the airway tube. RESULTS: There was no statistically significant difference in LSP between the 11 Louis T.A., Lavori P.W., Bailar J.C. III, Polansky M. ‘Crossover and self-controlled designs in clinical research’. In: Bailar J.C. III, Mosteller F., eds. Medical uses of statistics, 2nd edn. Boston, MA: New England Medical Journal Publications, 1992:83-104.
SLMA and the PLMA. The mean LSP was 19.6 +/- 5.8 cm H(2)O and 20.9 +/- 6.7 cm H(2) O for the SLMA and the PLMA, respectively. There was a similarity between the SLMA and the PLMA regarding the number of attempts required and the duration for insertion. How- ever, fibreoptic positioning was better with the PLMA than with the SLMA (P < 0.0001). CONCLUSION: The clinical performance of the SLMA as a ventilatory device is comparable with that of the PLMA, as illustrated by the similar LSPs. The inferior position of the SLMA airway tube compared with that of the PLMA does not affect its ease of ventilation. A4. Adaptive trials
This novel approach is defined as ‘a clinical study design that uses accumulating data to decide how to modify aspects of the study as it continues, without undermining the validity and integrity of the trial.’12 The randomisation ratio is changed during the course of the trial; these changes should not be ad hoc but by design. In general, there are two main approaches: monitoring the balance of baseline covariates in the rando- misation during the continuing trial; and a response-adaptive treatment allocation. An example of the latter is that, based on observed benefits (or absence of benefits) in particular subgroups in the first series of randomised subjects, one continues the randomisation (or discontinues the trial) in those subgroups only. Another version of an adaptive design is a sequential trial. In this approach, the number of participants is not pre-specified. Instead, participants are recruited until intervention differences are observed (or can be dismissed). These trials are designed with the idea that the accu- mulated evidence at – pre-specified – interim analyses is sufficient to draw appropri- ate inferences about the benefits (and risks) of the device. Particularly in these adap- tive trials, the use of Bayesian methods has been on the rise; that has also been true of clinical trials of medical devices over the past decade, as it may offer many advantages when it comes to evaluating more invasive, implantable medical devices.13 In Bayesian approaches, estimates of the benefits (and risks) are made based on prior informa- tion, which is complemented by and weighted against empirical observations taken from new studies. Accordingly, inferences about the benefits and risks of a device are not based solely on the empirical studies but on the weighted evidence of previous knowledge and new evidence. Prior information can come from previous studies or informative registries.
The major advantage of adaptive trial designs is that they can suffice with consider- ably smaller sample sizes and are very efficient compared to typical randomised trials 12 U.S. Food and Drug Administration: Draft Guidance for Industry: adaptive design clinical trials for drugs and biologics. http:// www.fda.gov/downloads/DrugsGuidanceComplianceReg- ulatoryIn formation/Guidances/ UCM201790.pdf.
13 Bonangelino P. et al., ‘Bayesian Approaches in Medical Device Clinical Trials: A Discussion with Examples in the Regulatory Setting’. Journal of Biopharmaceutical Statistics 2011; 21:5, 938-953; Pibouleaua L, Chevreta S. Bayesian statistical method was underused despite its ad- vantages in the assessment of implantable medical devices. Journal of Clinical Epidemiology 64 (2011) 270e279.
with fixed numbers of participants, thereby shortening the device evaluation process. As for Bayesian modelling, the combined use of existing data could further improve the efficiency of the evaluation process by potentially decreasing costs and shorten- ing the timelines for device evaluation. Adaptive designs also have greater flexibility. Another advantage is the possibility of recalculating and adjusting the required sam- ple sizes, with more real data (beyond assumptions) on differences in benefits (and risks) and variation between the groups while the trial is ongoing. Finally, there is the built-in possibility of stopping a trial prematurely in the presence of unexpected risks, or even in the clear presence (or absence) of major benefits.
A disadvantage of these designs is that not all outcomes or devices lend themselves to early discontinuation. Interim analyses may not be feasible when the primary endpoint cannot be measured relatively soon after start of the trial. Trials may also be discontinued prematurely in error. Moreover, sufficient experience using a superior device may be lacking if the trial is discontinued prematurely in the presence of clear benefits and the device is subsequently introduced to the medical profession. Finally, this design requires trained statisticians with specialist knowledge to conduct the analyses and interpret the results.