An inspiratory impedance threshold device is a valve used in
cardiopulmonary resuscitation (CPR) to decrease
intrathoracic pressure and improve venous return to the heart. The valve is a part of a mask or other breathing device such as an
endotracheal tube, and may open at high or low pressures (called "cracking pressures.")
ITDs are still in the early phases of clinical use, but preliminary investigational studies have suggested a potential benefit in achieving
return of spontaneous circulation (ROSC) and early improvement after
cardiopulmonary arrest
Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possib ...
in humans. More recently, the Resuscitation Outcomes Consortium (ROC) Prehospital Resuscitation Impedance Valve and Early Versus Delayed Analysis (PRIMED) study (n=8718) failed to demonstrate improved outcomes with the use of an impedance threshold device (ITD) as an adjunct to conventional CPR when compared with use of a sham device. Quality of
cardiopulmonary resuscitation (CPR) was a deciding factor, with ITD increasing survival when in combination with "acceptable" CPR quality, but decreasing survival when CPR quality was not "acceptable".
This negative high-quality study prompted a Class III: No Benefit recommendation regarding routine use of the ITD.
ITD use may only be beneficial if the cardiac arrest is witnessed and the response time is rapid.
References
Further reading
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Cardiopulmonary resuscitation
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