Successful ventilation of two animals with a single ventilator: individualized shared ventilator setup in an in vivo mod
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RESEARCH LETTER
Open Access
Successful ventilation of two animals with a single ventilator: individualized shared ventilator setup in an in vivo model Michiel Stiers1* , Tom Bleeser2, Matthias Mergeay3, Hannah Pinson4, Luc Janssen3 and Tom Schepens5 Dear Editor, As the ongoing COVID-19 crisis is spreading from developed into developing nations, a shortage of ventilators in ICUs can be expected during peak prevalence. Sharing a ventilator among patients has been put forward as a rescue solution [1, 2]; in this setting, the so-called pairing of patients with similar characteristics is needed [3–5]. We have developed a modified shared ventilator design that allows for individualization of tidal volumes and driving pressures, positive end-expiratory pressure (PEEP), and inspired oxygen fraction (FiO2) [6], which can thus substantially individualize the delivered breaths, removing the need of pairing (see Fig. 1). We have now successfully used this ventilator setup in an in vivo model in a pair of ventilated sheep with different lung compliance, further supporting the potential of this shared ventilator setup as a lifesaving intervention in a crisis setting. After ethical approval, two healthy Swifter sheep (62 kg and 60 kg, 1 year old) received general anesthesia (buprenorphine-sevoflurane), intubation, arterial catheter, and a C-section. After baseline blood
gas and respiratory mechanics measurements, both sheep were connected to a single ventilator. Animal 1 had a lung compliance of 38 ml cmH2O− 1, while animal 2 had a lung compliance of 28 ml cmH2O− 1, differences in compliance could be explained by their position. Ventilator settings and measurements are shown in Table 1. The targeted tidal volume of the shared ventilator was set by adding together the individual tidal volumes of animal 1 (600 ml) and 2 (800 ml), creating a combined tidal of 1400 ml. We measured individual airway pressures, with a fluid-air interfaced pressure transducer (Edwards Lifesciences, Irvine, USA), and individual end-tidal CO2 (etCO2) levels (see Fig. 1). We then partially closed the inspiratory flow for animal 1 until the measured etCO2 levels for each animal were similar to those measured at baseline. This titration was successfully achieved within a few breaths, and the total set tidal volume could be distributed accurately among the two animals. With the added in-line individual PEEP valve, animal 2 received a PEEP of 7 cmH2O, whereas the other received 3 cmH2O of PEEP. The individually measured airway pressures demonstrated that the set PEEP levels were successfully achieved for each animal. FiO2 could be adjusted as expected, with one animal receiving an FiO2 of ~ 0.3 and the other ~ 0.8 with added O2 to its breathing circuit during a short test period. Adequacy of ventilation and oxygenation
* Correspondence: [email protected] 1 Department of Emergency Medicine, St-Dimpna, J-B Stessensstraat 2, 2440 Geel, Belgium Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This
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