Effect of an inspiratory impedance threshold device on hemodynamics during conventional manual cardiopulmonary resuscitation.
BACKGROUND
In animals in cardiac arrest, an inspiratory impedance threshold device (ITD) has been shown to improve hemodynamics and neurologically intact survival. The objective of this study was to determine whether an ITD would improve blood pressure (BP) in patients receiving CPR for out-of-hospital cardiac arrest.


METHODS
This prospective, randomized, double-blind, intention-to-treat study was conducted in the Milwaukee, WI, emergency medical services (EMS) system. EMS personnel used an active (functional) or sham (non-functional) ITD on a tracheal tube on adults in cardiac arrest of presumed cardiac etiology. Care between groups was similar except for ITD type. Low dose epinephrine (1mg) was used per American Heart Association Guidelines. Femoral arterial BP (mmHg) was measured invasively during CPR.


RESULTS
Mean+/-S.D. time from ITD placement to first invasive BP recording was approximately 14 min. Twelve patients were treated with a sham ITD versus 10 patients with an active ITD. Systolic BPs (mean+/-S.D.) [number of patients treated at given time point] at T = 0 (time of first arterial BP measurement), and T=2, 5 and 7 min were 85+/-29 [10], 85+/-23 [10], 85+/-16 [9] and 69+/-22 [8] in the group receiving an active ITD compared with 43+/-15 [12], 47+/-16 [12], 47+/-20 [9], and 52+/-23 [9] in subjects treated with a sham ITD, respectively (p < 0.01 for all times). Diastolic BPs at T = 0, 2, 5 and 7 min were 20+/-12, 21+/-13, 23+/-15 and 25+/-14 in the group receiving an active ITD compared with 15+/-9, 17+/-8, 17+/-9 and 19+/-8 in subjects treated with a sham ITD, respectively (p = NS for all times). No significant adverse device events were reported.


CONCLUSIONS
Use of the active ITD was found to increase systolic pressures safely and significantly in patients in cardiac arrest compared with sham controls.
Pirrallo
Ronald G
RG
Medical College of Wisconsin, Department of Emergency Medicine, 9200 W. Wisconsin Ave., FEH Room 1870, Milwaukee, WI 53226, USA. pirrallo@mcw.edu
Aufderheide
Tom P
TP
Provo
Terry A
TA
Lurie
Keith G
KG
D000368:Aged; D000704:Analysis of Variance; D016887:Cardiopulmonary Resuscitation / Q000009:adverse effects / Q000295:instrumentation* / Q000706:statistics & numerical data; D004311:Double-Blind Method; D004632:Emergency Medical Services / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000295:instrumentation* / Q000706:statistics & numerical data; D011446:Prospective Studies; D011654:Pulmonary Edema / Q000209:etiology; D020127:Recovery of Function; D016019:Survival Analysis; D014922:Wisconsin