A ventilator system for providing respiratory support, the ventilator system comprising: a controller configured to generate a first control signal for a first time-period based on a pre-stored data, and a second control signal for a second time-period during an inspiration time of a ventilation cycle based on at least one of a pressure and a flow rate of the medical gas supplied from the bellow assembly to the patient during the inspiration time of the ventilation cycle, wherein the second time-period is after the first time-period during the inspiration time and wherein the first control signal is a pulse width modulation signal having a constant pulse width and the second control signal is a pulse width modulation signal having a varying pulse width; a bellow assembly; a rotary pump electrically coupled to the controller and configured to: run an intermediate speed to change one of a pressure and a flow rate of a drive gas to a first value if the first control signal is received from the controller; and vary the speed of the pump to change the one of the pressure and the flow rate of the drive gas to a second value if the second control signal is received from the controller, wherein the second value is greater than the first value; and the rotary pump further configured to deliver the drive gas to the bellow assembly, wherein the bellow assembly is configured to supply a medical gas during the inspiration time based on the one of the pressure and the flow rate of the drive gas delivered from the rotary pump. a controller configured to generate a first control signal for a first time-period based on a pre-stored data, and a second control signal for a second time-period during an inspiration time of a ventilation cycle based on at least one of a pressure and a flow rate of the medical gas supplied from the bellow assembly to the patient during the inspiration time of the ventilation cycle, wherein the second time-period is after the first time-period during the inspiration time and wherein the first control signal is a pulse width modulation signal having a constant pulse width and the second control signal is a pulse width modulation signal having a varying pulse width; a bellow assembly; a rotary pump electrically coupled to the controller and configured to: run an intermediate speed to change one of a pressure and a flow rate of a drive gas to a first value if the first control signal is received from the controller; and vary the speed of the pump to change the one of the pressure and the flow rate of the drive gas to a second value if the second control signal is received from the controller, wherein the second value is greater than the first value; and run an intermediate speed to change one of a pressure and a flow rate of a drive gas to a first value if the first control signal is received from the controller; and vary the speed of the pump to change the one of the pressure and the flow rate of the drive gas to a second value if the second control signal is received from the controller, wherein the second value is greater than the first value; and the rotary pump further configured to deliver the drive gas to the bellow assembly, wherein the bellow assembly is configured to supply a medical gas during the inspiration time based on the one of the pressure and the flow rate of the drive gas delivered from the rotary pump.