Mechanical ventilation in the term used for assisted ventilation where oxygen is supplied to the lungs by means of artificial ways. It can be of two main types: 1. Assist-control Ventilation: In this type of ventilation preset tidal volume is given by the ventilator regardless of the fact that whether it was initiated by the patient or the ventilator itself. 2. Controlled mechanical ventilation: Tidal volume provided to the person is only initiated by the ventilator at a predetermined rate. ADVANTAGES OF ASSIST-CONTROL MECHANICAL VENTILATION 1. Breaths can be initiated by both the person and the machine. 2. Patient can control the timing and frequency of breaths. 3. More comfortable and decreased work required for breathing. 4. Easy correction of respiratory acidosis and alkalosis. DISADVANTAGES OF ASSIST-CONTROL MECHANICAL VENTILATION 1. Risk of barotrauma in stiff lungs 2. Unsynchronization between the patient and the ventilator if the patient is an active breather with strong drive. 3. Patient may end up with respiratory alkalosis if he/she hyperventilates. 4. Tachypneic patients or those who are not exhaling properly can develop hypotension and decreased venous return.