The focal reason of positive weight ventilation is that gas streams along a weight inclination between the upper aviation route and the alveoli. The size, rate and term of stream are controlled by the administrator. Stream is either volume focused on and weight variable, or weight constrained and volume variable. The example of stream may be either sinusoidal (which is ordinary), decelerating or consistent. Stream is controlled by an exhibit of sensors and microchips. Ordinarily, motivation is dynamic and termination is inactive (albeit cutting edge ventilators have dynamic exhalation valves).
    There are two stages in the respiratory cycle, high lung volume and lower lung volume (inward breath and exhalation). Gas trade happens in both stages. Inward breath serves to recharge alveolar gas. Dragging out the span of the higher volume cycle upgrades oxygen uptake, while expanding intrathoracic weight and diminishing time accessible for CO2 evacuation.
    Inability to oxygenate is brought on by lessened diffusing limit and ventilation perfusion confuse. This can frequently be overcome by restoring FRC by expanding benchmark aviation route weight utilizing CPAP. On the off chance that the issue is atelectasis due, for instance, to bodily fluid stopping or diaphragmatic propping after stomach surgery, or directed measures of pneumonic edema, CPAP, as conveyed by facemask or endotracheal tube, might sufficiently restore aspiratory mechanics to dodge expansion inspiratory backing. CPAP is anything but difficult to apply: all that is needed is a PEEP valve and a stream generator. 

    The stream generator is critical as top inspiratory stream in many patients is 30-60 liters every moment, and this stream rate is obliged to evade a circumstance where the patient is endeavoring to take in against an expiratory (PEEP) valve. The extent of PEEP is controlled by a spring stacked system on the expiratory valve. At the point when conveyed through an endotracheal tube, CPAP can be regulated by connecting a PEEP valve to the end of a T-piece, or through a "stream by circuit" inside a mechanical ventilator. 

    For the larger part of patients, in any case, the capacity to create minute ventilation or to expand ineffectively consistent lungs, is deficient. Inspiratory support utilizing one of a large number of modes of ventilation is needed.