A portable handheld pressure support system (10) is configured to provide pressure support therapy to a subject. The pressure support system provides a pressurized flow of breathable gas that is delivered to the airway of the subject to treat COPD and/or dyspnea, hyperinflation, and/or other conditions. The system is configured to adjust an expiratory pressure level of the pressure support therapy responsive to identification of hyperinflation in the subject. The pressure support therapy provided to the subject is configured to be used as needed to rapidly alleviate shortness of breath, hyperinflation, and/or other symptoms. The pressure support system is configured to be small and lightweight so that the subject may carry the system and use the system as needed.