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User-friendliness of the Latest Generation of ICU Ventilators
Abstract & Commentary
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Attempting to complete eight basic tasks on each of 11 new-generation ICU ventilators, 10 intensivists who were experienced in mechanical ventilation but unfamiliar with those particular machines met with widely varying success. Some tasks could not be completed at all, and none of the ventilators were judged user-friendly in all areas.
Source: Vignaux L, et al. Evaluation of the user-friendliness of seven new generation intensive care ventilators. Intensive Care Med 2009;35:1687-1691.
In an attempt to reproduce the situation in which a covering physician is called urgently to a patient's bedside because of a ventilator-related problem, this laboratory study sought to determine how readily intensivists could operate new-generation ICU mechanical ventilators with which they were not personally familiar. The study was performed in Geneva using a test-lung set-up, with several ventilators available in the United States (Avea, EngstromCarestation, Evita XL, PB-840, and Servo-i) as well as six others mainly used in Europe. Ten experienced intensivist physicians (five pulmonologists and five anesthesiologists), who were familiar with mechanical ventilation but not with the study ventilators, were each given eight different tasks to perform, in random order. The tasks were: 1) turn ventilator on, 2) recognize mode and parameters, 3) recognize and set alarms, 4) change mode, 5) find and activate the pre-oxygenation function, 6) set pressure support, 7) activate standby, and 8) find and activate the non-invasive ventilation mode. The physicians were given 3 minutes to accomplish each task, and their times were compared with those of a clinician experienced with the operation of each of the ventilators.
All task times for the subjects were significantly longer than those of the reference operator. The ventilators recorded a mean of 13 task failures each, with a standard deviation of eight tasks. The largest number of task failures was recorded by the Avea, with 28; the Evita XL had the least failures with six, and the EngstromCarestation and Hamilton G5 were next with seven each. Finding and activating the non-invasive ventilation mode was the most frequently failed task (22 occurrences), followed by setting pressure support (19 times), and recognizing the ventilation mode and associated parameters (15 times). None of the physicians could successfully set pressure support or operate the non-invasive ventilation function on the Avea ventilator. For all of the other functions tested, there was substantial variation across ventilators and among individual physicians. No ventilator was clearly better than the others on all points tested.
Participating physicians were asked to grade their subjective impression of the overall difficulty of dealing with each ventilator, on a scale of 0 (very easy) to 10 (very difficult). These difficulty scores ranged from 3.8 (± 2.1) for the Hamilton G5 and 4.2 (± 1.5) for the Evita XL, to 6.4 (± 1.4) for the PB 840 and 7.3 (± 1.9) for the Avea.
Today's ICU ventilators are more capable than their predecessors in numerous ways, but they are also more complex, mandating adequate training and orientation for anyone who uses them. This study demonstrates that different machines in the current generation of ventilators vary considerably in their intuitiveness and general user-friendliness.
A previous study by Uzawa and colleagues was similar in design and overall results.1 These investigators asked 21 Japanese medical residents, who had worked in the ICU and were familiar with mechanical ventilation, but had not used the specific machines involved, to perform eight tasks while being timed and also to rate the ease of their completion with four different ventilators. In this case the ventilators studied were the Evita XL, PB-840, and Servo-i as in the Vignaux study, plus the Newport e500. Subjects were asked to start the ventilator, assemble the accessories, set the alarms, respond to alarms, and make four different specific changes from one ventilation mode to another. Overall, the rate of operational failures for all subjects, for all tasks, was 23%, with the greatest number of failures and longest task times for the Evita XL and the shortest for the Newport e500. There were more operational failures in setting up the ventilators and in making the ventilator setting changes than in setting or reacting to the alarms. Although there was considerable variation among the participants in their assessments, the Newport e500 and Servo-i were judged to be less difficult to operate than the PB-840 and the Evita XL.
In an accompanying editorial, Richard and Kacmarek point out that, unlike their predecessors of two decades ago, almost all new-generation ICU ventilators incorporate a computer screen as the basis of their user interface.2 Many of these screens have layers of menus that the user must navigate to change the ventilator settings, with even simple changes sometimes requiring multiple steps. As this study emphasizes, these interfaces vary substantially in their user-friendliness, such that the naïve would-be operator is unlikely to be able to figure out how to make every desired change. Richard and Kacmarek use this observation to forcefully make the point that no one should attempt to change the settings on an ICU ventilator who has not been adequately trained and checked out in its operation.
I agree completely. In the ICUs in which I practice, only respiratory therapists, by physician order, can perform the ventilator adjustments studied by Vignaux et al — except for brief trial changes, which must be reversed before the person who makes them leaves the bedside — and only therapists who have been fully trained on the ventilators in use can work in the units. Policy varies among institutions, and the central issue is not whether it is a respiratory therapist, a physician, or a nurse that manipulates the ventilator, but rather that every clinician who adjusts it must be thoroughly familiar with its functions, be authorized to make such changes, and appropriately document what they do.