Method and device for diagnosing and/or treating sleep apnea and related sleep disorders, such as snoring and respiratory effort-related arousals, includes an inflatable implement which is applied to the external surface of the chest and/or abdomen (Vest). Pressure is caused to rise to a predetermined positive value. The rate of airflow into and/or out of said Vest is monitored, whereby the Vest Flow is displayed or processed to obtain information about the breathing characteristics of the patient.