Abstract
Background:
The COVID-19 pandemic of 2020 created concern regarding the preparedness of the US Health Care System. One major concern was the availability of mechanical ventilators. Consequently, the US government and many state and local health care systems called upon manufacturers of existing mechanical ventilators as well as entrepreneurs, innovators, and scientists to rapidly manufacture or develop devices to provide assisted ventilation. The Partners HealthCare System developed an Innovation center with one group devoted to ventilator innovation that met regularly. We present here the results of our evaluation of 2 of two “bag squeezer” types ventilators.
Methods:
We evaluated the performance of near final prototypes of the RISE and a version of the MIT “bag Squeezer” type ventilators using the Michigan Instruments TTL adult patient lung simulator. A NICO respiratory monitor (Philips) was used to assess the difference between ventilator settings and actual delivered gas volume. The primary outcome was the ability of each ventilator to perform to its specification, and secondary outcomes included alarm system response. Each device was tested through the same range of specified ventilation and lung simulator conditions. A greater than 10% deviation of actual delivered from device set parameter in a given setting was considered unacceptable.
Results:
Neither the MIT nor RISE ventilator were able to perform to their specification. Both were unable to maintain delivery of set tidal volume as respiratory rate and inspiratory time were varied (Figure 1a and 1b). However, both performed best when the compliance was 50 mL/cm H2O and the resistance 5 cm H2O/ L/s. Specifically, the MIT ventilator was unable to provide the set tidal volume in 86% of the respiratory rate trials (1a) while the RISE ventilator was unable to provide the set tidal volume 75% of the time (1b). Similar finding occurred with inspiratory time variation vs. set tidal (79% vs, 82% respectively MIT then RISE). Alarms inappropriately sounded in 100% of trials with MIT ventilators and 66% of trials with the RISE ventilator, with numerous alarms sounding unrelated to the clinical condition tested. However, it should be remembered that these ventilators were developed over 4 to 6 weeks.
Conclusions:
These ventilators were unable to meet specification. This data was provided to the manufacturers. Before these type ventilators are put into use their performance should be carefully evaluated.
The red dotted line represents a 1.0 ratio between set and measured tidal volume The red dotted line represents a 1.0 ratio between set and measured tidal volume
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