However, the precise mechanism of blood flow during chest compressions Protein Tyrosine Kinase inhibitor has been controversial since the 1960s. The two main hypotheses are the external cardiac massage model and the thoracic pump model. The external cardiac massage model suggests that chest compressions directly compress the heart between the depressed sternum and the thoracic spine [1]. This ejects blood into the systemic and pulmonary circulations while backward flow during declick here Compression is limited by the cardiac valves. The external cardiac massage model is supported by radiographic evidence of direct compression of cardiac structures

during chest compressions [14]. The thoracic pump model suggests that chest compressions intermittently increase global intra-thoracic pressure, with equivalent pressures exerted on vena cava, the heart and the aorta [9]. Thus blood is ejected retrograde from the intra-thoracic venous vasculature as well as antegrade from the intra-thoracic arterial vasculature and both arterial as well as venous pressures rise concomitantly. Therefore the presence of an arterial pulse in itself is not a reliable indicator of blood flow. This principle is illustrated

by the fact that a ligated artery will continue to pulsate even in the absence of blood flow. However, the compliance Ganetespib in vitro of venous capacitance vessels is greater than the compliance of arterial resistance vessels. Therefore a pressure differential between the extra-thoracic arterial and venous sides of the vascular tree is formed. This pressure differential is but a fraction of the arterial pulse pressure, yet it is sufficient to drive some blood flow. The thoracic pump model is supported by arterial and venous pressure tracings demonstrating simultaneous peaks in venous and arterial pressures during

chest compressions [15]. In toto, the available evidence suggests that both cardiac massage and the thoracic pump contribute to blood flow during chest compressions. Yet even excellent chest compressions can only generate a fraction of baseline blood flow [16]. Therefore the time during chest compressions contributes to the ongoing ischemic insult to the Rebamipide patient’s heart and brain. The brain is the organ most susceptible to decreased blood flow and suffers irreversible damage within 5 minutes of absent perfusion. The myocardium is the second most susceptible organ, with ROSC directly related to coronary perfusion pressures [17]. Therefore successful resuscitation with neurologically intact survival and ROSC critically depends on maintaining blood flow to the heart and brain via chest compressions. Technique for Chest Compression Chest compressions consist of forceful and fast oscillations of the lower half of the sternum [1]. The technique of delivering chest compressions is highly standardized and based on international consensus that is updated in 5-year intervals [4, 13, 18].