Addition of Impedance Threshold Device Therapy Improves Blood Pressure in the Out-of-Hospital Spontaneously Breathing Hypotensive Patient

Abstract

An impedance threshold device (ITD) intended for use in spontaneously breathing patients exhibiting low blood pressure. The ITD is reported to provide therapeutic benefit through inspiratory resistance of 7cmH2O, and clinical improvement has been observed as soon as a patient begins to breathe through it. Pre-clinical and clinical studies have shown that the ResQGARD (Advanced Circulatory, Roseville, MN) increases blood pressure during hypotension from a variety of causes. This device has yet to be tested in a large urban out-of-hospital system. This pilot study sought to identify a change in vital signs following paramedic administration of the ITD. Secondary outcomes included patient tolerance and paramedic perception of patient tolerance. A six-month prospective nonrandomized observational cohort study was conducted. All paramedics received 30-45 minutes of training on patient selection and application of the ITD. This initial training was reinforced utilizing a Web-based training video, and a visual reminder (8.5 x 11 laminated sheet) of the study protocol posted inside the ambulance. The cohort was spontaneously breathing adult patients with hypotension due to dehydration, sepsis, anaphylaxis, or hypovolemia. Exclusion criteria included: unable to maintain airway, pulmonary edema, or significant respiratory distress. Upon determination of hypotension (SBP<90mmHG), standard therapy (positioning, reassurance, and intravascular fluids) was initiated and the ITD was applied in accordance with manufacturer's recommendation. The subject was coached to breathe slow and deep utilizing the mask-type device. Supplemental oxygen was supplied if deemed necessary by the paramedic. Vital signs were documented every 2-5 minutes post intervention. Patient tolerance (observed), and patient comfort (reported) were documented. Two hundred subjects were recruited with a mean initial blood pressure 78/50 (± 14/13) heart rate 87 (± 25) beats per minute and ventilatory rate of 19 (± 7) breaths per minute. After paramedic treatment, including ITD mean blood pressure 97/63 (±19/15; p=<.0001) heart rate 87 (± 25; p=.47) beats per minute and ventilatory rate of 19 (± 7; p=.002) breaths per minute, with 66% of blood pressures increased after. Of the 200 hypotensive subjects, 29 were as a result of trauma (fall, auto collisions, shootings/stabbings). The trauma population also demonstrated a significant increase in mean blood pressure from 80 to 103 systolic, and 56 to 71 diastolic (p=<.0001 and .001, respectively), and non-significant change in mean heart rate from 89 to 80 (p=.17). In all groups, 75% of patients reported moderate to easy tolerance, and only 15% of patients reporting difficult tolerance. The ITD was easily assimilated into the standard bundle of care for the treatment of hypotensive patients. A significant increase in blood pressure was observed in the overall cohort. Importantly for the trauma cohort, the ITD did not restore “normal” blood pressure, but continued to allow for permissive hypotension, and continued to be generally well tolerated.