_applied sciences_  
_Article_  
Validation of a Simulink Model for Simulating the Two Typical Controlled Ventilation Modes of Intensive Care Units  
Mechanical Vertilators \({}^{\ddagger}\)  
[PERSON] 1  
[PERSON] 1  
1 Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari,  
70121 Bari, Italy; [EMAIL_ADDRESS] (P.T. ); [EMAIL_ADDRESS] (E.D. ); [EMAIL_ADDRESS] (R.A.)  
2 Interdisciplinary Department of Medicine, University of Bari, 70121 Bari, Italy; [EMAIL_ADDRESS]  
3  
The mechanical ventilator is a vital component of critical care services for patients with severe acute respiratory failure as it provides the energy necessary to ensure adequate flow, pressure, and volume of gas in the alveoli during inspiration. Modern mechanical ventilation exploits the concept of positive pressure ventilation, in which the mechanical ventilator allows the patient to inhale by applying an over atmospheric pressure to the airways of the patient, generating a positive pressure inside them that mechanically produces the current volume [5]. The ventilator can be connected to the patient's airway through an endotracheal tube (invasive mechanical ventilation) or through a face mask (non-invasive ventilation) [6]. A mechanical ventilator is a sophisticated electronic machine that replaces, either totally or partially, the mechanical functions of the respiratory system when it becomes unable to perform its task because of critical conditions due to illness or surgical procedures [7]. It consists primarily of two blocks. The first is a pneumatic unit, composed of directional valves, check valves, pressure regulators, filters, tanks, pressure transducers, and flow rate sensors, and is connected to the patient's lungs through a series of tubes. The second is an electronic unit that performs logic operations, and allows the doctor to set the conditions and parameters of the values of interest and that trigger alarms if the patient is in danger [5]. Modern ventilators use closed-loop control to keep the inspiration and expiration pressure, or the inspiration flow, constant in the face of the changing conditions of the patient [7,8]. The control system of the ICU ventilator allows the operators/doctors to set different ventilation modes according to the required parameters, such as, respiratory rate (RR), peak inspiratory flow rate (I\({}_{\text{pf}}\)), the percentage of inhaled oxygen (FiO\({}_{2}\)), inspiratory: expiratory ratio (I:E), tidal volume (V\({}_{\text{T}}\)), peak of inspiratory pressure (PIP), and the positive end-expiratory pressure (PEEP) [9,10]. At least three of these parameters have to be set independently in order to achieve the required ventilation mode [11]. The pneumatic schemes of commercially available ventilators for ICUs can present some variations depending on the design adopted by the manufacturer. Most manufacturers have made the pneumatic circuit of their ventilators available as part of their published technical information in response to the emergency caused by the spread of COVID-19. Ventilators for intensive care units include: the Siaretron 4000, produced by Siare Engineering; the Galileo ventilator, produced by Hamilton Medical [12]; the Drager Infinity V500 intensive care ventilator, produced by Drager Medical AG & Co [13]; the Aisys CS2, produced by GE Healthcare [14]; the Puritan Bennett 800, produced by Medtronic [15]. In order to address the emergency situation caused by the pandemic, the Medicine and Healthcare products Regulatory Agency (MHRA) in the United Kingdom, and the Food and Drug Administration (FDA) in the US, have recently published guidelines on the technical specifications that ventilators must possess in order to be used in hospitals during the COVID-19 outbreak [16]. An extensive review of the expected parameters, performance, and the mode of operation of mechanical ventilators is provided in [17,18].