The use of impedance threshold devices in spontaneously breathing, hypotensive trauma patients

Abstract

Impedance threshold devices are a novel therapeutic option to increase blood pressure in the spontaneously breathing, hypotensive, trauma patient. They have multiple potential mechanisms of action. The most important is their ability to induce a more negative intrathoracic pressure during inspiration. They achieve this by the presence of a series of valves.These valves only open once the patient has generated a more negative intrathoracic pressure than is normally required for inspiration to occur. This negative intrathoracic pressure is thought to increase venous return and therefore cardiac output and subsequently blood pressure. This narrative review examines the evidence pertaining to the use of these devices in spontaneously breathing, hypotensive, trauma patients. While the literature supports the ability of these devices to increase systolic blood pressure in both animal and human models of hypotension, and more recently in patients with true pathological hypotension, potential flaws are discussed, and several key questions that have not been addressed by studies to date are highlighted. Notwithstanding these problems, impedance threshold devices may have a role in hypotensive trauma patients, particularly during the pre-hospital phase of care when available resources limit treatment options. Further work is required to prove both their clinical effectiveness and safety.