['The impedance threshold device (ITD-7) augments the vacuum created in the thorax with each inspiration, thereby enhancing blood flow from the extrathoracic venous systems into the heart.', 'To the best of our knowledge, the ITD-7 has not previously been investigated in hypotensive patients in the emergency department (ED) or the prehospital setting. The objective of this study was to determine whether the ITD-7 would increase systolic arterial pressures in hypotensive spontaneously breathing patients.', 'The ED study was a prospective, randomized, double-blind, sham control design. Patients with a systolic blood pressure ≤ 95 mm Hg were randomized to breathe for 10 min through an active or sham ITD. The primary endpoint was the change in systolic blood pressure measured non-invasively. The prehospital study was a prospective, non-blinded evaluation of the ITD-7 in hypotensive patients.', 'In the ED study, the mean ± standard deviation rise in systolic blood pressure was 12.9 ± 8.5 mm Hg for patients (n = 16) treated with an active ITD-7 vs. 5.9 ± 5.9 mm Hg for patients (n = 18) treated with a sham ITD-7 (p < 0.01). In the prehospital study, the mean systolic blood pressure before the ITD-7 was 79.4 ± 10.2 mm Hg and 107.3 ± 17.6 mm Hg during ITD-7 use (n = 47 patients) (p < 0.01).'] Does an impedance threshold device increase blood pressure in hypotensive patients?