Mechanism of a Ventilator
Globally regarded as the crucial missing link between patients recovering and patients succumbing to the life-threatening Covid-19 virus, ventilators, according to experts in the field, helps doctors buy time for other agents known to heal a patient’s lungs ultimately leading to full recovery. Just like the need for fresh air in a room or in a building, ventilation in the human body aids in the exchange of air between the lungs and the atmosphere. It is here that a ventilator is required to simulate the process and provide temporary ventilatory support. According to the World Health Organisation (WHO), it is the ability to offer mechanical respiratory assistance and adequate ventilation to patients weighed down by illness, trauma, congenital defects, or drugs including anaesthetics that makes ventilators a crucial inclusion in any country’s arsenal.
A ventilator is typically made up of a flexible breathing circuit, a control system, monitors, and alarms. It functions such that the gas is delivered using a double-limb breathing circuit. The gas may be either heated or humidified using appropriate devices. The exhalation limb is known to release the gas to the ambient atmosphere. The intensive care ventilators are usually connected to a wall gas supply. Ventilators, in general, are microprocessor controlled and regulate the pressure, volume, and FiO2 with the power known to be supplied from either an electrical wall outlet or a battery unit. Here FiO2 is the per centage of oxygen in the air mixture delivered to the patient. The flow being the speed in litres per minute at which the ventilator delivers breaths and compliance being the change in volume divided by change in pressure.
Using the control mode, patients are provided with complete support in the case of not being in a position to breathe all by themselves. The ventilator in the control mode provides mandatory breaths at preset time intervals restricting the patient from breathing spontaneously. Assist/ control modes according to the WHO provides complete support. For instance, it delivers an assisted breath whenever the ventilator senses a patient’s inspiratory effort. Mandatory breaths are delivered at preset time intervals. Through volume-controlled breaths, a control system ensures that only a predetermined tidal volume is delivered during the inspiratory cycle. Pressure-controlled breaths regulate the flow delivery to attain and sustain a clinician-set inspiratory pressure level for a set time so that the ventilator delivers controlled or assisted breaths that are time cycled. Combination modes are also available. Ventilator manufacturers need to ensure no leaks in the breathing circuit or components as the latter could prevent the ventilator from delivering the appropriate amount of ventilation. Proper maintenance and imparting training to help operators avoid errors or machine failures is critical to the process.