OPTIMIZING THE RESPIRATORY PUMP: HARNESSING INSPIRATORY RESISTANCE TO TREAT SYSTEMIC HYPOTENSION
Victor A Convertino PhD, Kathy Ryan PhD, Caroline Rickards PhD, Steven Glorslky MD, Ahamed H Idris MD, Demetris Yannopoulus MD et al
Respiratory Care Magazine-June 2011 Volume 56 number 6 pg846-855
In times of acute hypotension, severe shock can develop as the heart loses its effective contractility because of low preload pressure. As venous tone decreases, blood pools in the periphery. To reload the heart with blood, this study suggests that venous blood volume can be drawn from the periphery and back into the chest by strong Muller maneuvers, whereby the patient takes deep breaths against a valve which opens at seven cm below atmospheric. This in effect lowers thoracic CVP, milking the blood to the chest, creating a flow gradient from the periphery towards the heart. As blood volume increases so does stroke volume and thus peripheral perfusion. Consider. If the blood that was once pooling in the periphery is now in transit back towards the chest it is not something the heart has to push again on systole. To say again, a decreased resistance to forward propulsion of blood creates less myocardial work. Authors claim real effectiveness with Ambu bagging the hypotensive in the emergency arena. Patient is breath augmented at the very end of their inspiratory gasp with a breath prn when they fail to trigger the -7cm valve. In essence SVR is reduced in the head and extremities. The maneuver maintains sympathetic nervous system mechanisms in the face of the strong parasympathetic effects of shock.
The researchers note average increases of systolic blood pressures of 10 mm, a formidable increase in stroke volume by fifteen ccs, and most importantly increases in cardiac output by 1.7 liters per minute.
To say it another way. SVR is the systemic vascular resistance to flow of any liquid through a conduit. SVR for our purposes includes all blood vessels outside of the heart. The more conduit the more resistance. Or if that conduit is smaller in diameter-this also increases resistance to flow. Or if the conduit is full of fluid and not empty-this also increases resistance. How does this happen? The fluid from the last beat sits where the new wave should go. A heart that doesn’t have much blood to pump cant fill the coronary arteries well, a double whammy of more work and little pay for the myocardium. The heart has a hard time of moving blood through the capillaries when they are already full of the last three heart beat’s blood flow. If we can get some of this blood out of the capillaries and flowing back towards the chest, this takes enormous burdens off of the heart to do work and feeds it at the same time.
That is the goal of this temporary emergency regime.
This is not a substitute for hypotension management. This is for use in the emergent five minute window between the moment of realizing the patient’s situation and the ability to react with fluid and pressors.
The study used a valve with an opening pressure of seven cm through which the patient has to open to get a breath, this administered via a tight mask. Google ResQUOD, ResGUARD, and CircQlator. All devices FDA approved.
LUNGLORD NOTE: The idea is sound and well proven. But aren’t there simpler methods to accomplish as much? The raising of the legs and feet usually raises blood pressure esp for LUNGLORD in certain situations. In the hospital, however, for the hypotensive patient, leg lifts accomplishes much the same effect as inspiratory resistance pumping, However, pumping blood uphill is the same as increasing SVR. What if we raised the legs and lowered them a foot every ten seconds, essentially dumping blood back into the chest? LUNGLORD says Hmmmm. Would there be any benefit to it? This would require much less patient effort and cooperation. LUNGLORD declares this cogent trick nice to know and worthy of cranial space for those blanched patients discovered in chairs or on commodes where regaining blood pressure is critical before they can be safely placed with the legs and feet at a higher level than the heart. Further, requiring study, if decreased ICP were required, such a device would likely accomplish this objective as a means of control until surgery can be arranged. Avoid use in pulmonary edema and CHF, Pulmonary HTN, penetrating chest wound.