A control unit for a combination respiratory therapy device, comprising: an air supply, a first air circuit operably coupled to the air supply to supply positive-pressure air flow to a positive air flow patient interface of the combination respiratory therapy device, a second air circuit operably coupled to the air supply to supply negative-pressure air flow to a negative air flow patient interface of the combination respiratory device; the second air circuit being physically separate from the first air circuit, a third air circuit operably coupled to an air pulse generator to supply a series of air pulses to an air pulse patient interface of the combination respiratory therapy device, wherein the third air circuit is physically separate from the second air circuit and is selectively coupled to the positive air flow patient interface; a controller to control the air supply, and memory accessible by the controller, the memory comprising instructions executable by the controller to activate the air supply to supply air to the first air circuit at a first positive pressure during a ventilation or lung volume recruitment portion of a respiratory therapy treatment session; and activate the air supply to supply air to the second air circuit at a negative pressure during a coughing assistance portion of the respiratory therapy treatment session, wherein the memory comprises instructions executable by the controller for each of a plurality of cough cycles of the coughing assistance portion to alternatingly activate the air supply to supply air to the first air circuit at a second positive pressure greater than the first positive pressure followed by the supply of air to the second air circuit at a negative pressure. an air supply, a first air circuit operably coupled to the air supply to supply positive-pressure air flow to a positive air flow patient interface of the combination respiratory therapy device, a second air circuit operably coupled to the air supply to supply negative-pressure air flow to a negative air flow patient interface of the combination respiratory device; the second air circuit being physically separate from the first air circuit, a third air circuit operably coupled to an air pulse generator to supply a series of air pulses to an air pulse patient interface of the combination respiratory therapy device, wherein the third air circuit is physically separate from the second air circuit and is selectively coupled to the positive air flow patient interface; a controller to control the air supply, and memory accessible by the controller, the memory comprising instructions executable by the controller to activate the air supply to supply air to the first air circuit at a first positive pressure during a ventilation or lung volume recruitment portion of a respiratory therapy treatment session; and activate the air supply to supply air to the second air circuit at a negative pressure during a coughing assistance portion of the respiratory therapy treatment session, wherein the memory comprises instructions executable by the controller for each of a plurality of cough cycles of the coughing assistance portion to alternatingly activate the air supply to supply air to the first air circuit at a second positive pressure greater than the first positive pressure followed by the supply of air to the second air circuit at a negative pressure.