The device is mechanically relatively straightforward but physiologically
more complex.
When you compress the chest air leave the lungs through the ITD with minimal
or no impedance. When you ventilate a patient during CPR air goes into the
patient through the ITD with minimal or no impedance. However, when the
chest is recoiling (passively or actively) after being compressed, the ITD
blocks air from entering the lungs, thereby creating a greater decompression
phase vacuum inside the thorax. This pulls more blood back into the heart
and lowers intracranial pressure. In this way the heart is more efficiently
refilled after it is emptied during the compression phase and the brain gets
more blood by two different mechanisms. If the patient starts to breathe
after they are resuscitated, they can breathe through the ITD but it can be
difficult.
The ResQPOD that is being sold commercially in the US has -10 cm H2O
resistance when a patient inspires through it. The ITD used in the ROC study
had a -16 cm H2O resistance. The higher resistance is needed to optimize ACD
CPR (which we thought would eventually be used in the US at it is used now
in some other countries). However, with standard CPR we never achieve a very
large vacuum in the thorax with passive chest wall recoil so -10 cm H2O
resistance is adequate. That is, with passive recoil of the chest, the
vacuum created with an ITD is typically only -2 to -6 cm H2O.
So, in short, the ITD turbo-charges CPR. It doubles blood flow back to the
heart when used with manual standard CPR and it lowers intracranial
pressures (ICP) (part of the normal physiology we rediscovered about 8 years
ago). This results in more blood flow to the brain as there is less
resistance to forward flow.
You have to take the ResQPOD or ITD off of the patient when not doing CPR or
it can cause potential harm after the patient has been resuscitated. On the
other hand if a patient is gasping but in cardiac arrest then they are
trying to generate a negative intrathoracic pressure on their own and you
should leave the ResQPOD on the patient as long as CPR is needed and being
performed.
Most people do not know that each time we take a breath and inspire
spontaneously, or when we create a negative intrathoracic pressure within
the chest during the decompression phase of CPR with the ITD, this lowers
intrathoracic pressure and the lower pressure in the thorax is immediately
transferred to the brain via the rich venous plexus surrounding the spinal
cord. So with greater negative intrathoracic pressure, the ICP goes down.
Thus, we can lower ICP by lowering intrathoracic pressure. One way to do
this is with the ITD or ResQPOD. Needless to say we did not rediscover this
overnight but we believe this is contributes to why more patients wake up
after cardiac arrest when they are treated with the ITD. The lower the ICP
or resistance to forward blood flow, the more blood will go to the brain.
This principle has not been well exploited in medicine. The converse is also
true. One of the reasons that pressure bombs cause head injury is that
pressure waves are transmitted through the abdomen and thorax via the spinal
cord and venous plexus around the cords to the brain and this can cause a
sharp and deadly rise in ICP.
ResQPOD on ITD (Impedance
Threshold Device), joka kytketään elvytyspalkeen ja maskin väliin tai
intubaatioputkeen. ResQPOD parantaa rintakehän sisäisen paineen vaihtelua ja
edesauttaa verenkiertoa. Tutkimustulosten (yhteenveto
julkaisuista ja julkaisuluettelo)
mukaan ResQPOD parantaa veren virtausta sydämeen, nostaa systolista painetta
ja parantaa veren kulkua aivoihin. Potilaiden neurologinen ennuste paranee.
ResQPODia käytetään mm. sydänpysähdyspotilaille tai muille tajuttomille
potilaille, joiden verenpaine on laskenut. Yhdysvalloissa puolustusvoimat
käyttävät ResQPODia päävammapotilaiden kallonsisäisen paineen (ICP,
intracranial pressure) laskemiseen.
ResQPOD estää
tarpeettoman ilman pääsyn rintakehään PPE:n aikana. Suurempi negatiivinen
paine parantaa veren virtausta takaisin sydämeen2.
Kuva 2: Tavallisen PPE:n ja ResQPOD -avusteisen PPE:n ero
The Lancet on julkaissut tutkimuksen, jossa on verrattu mm. ResQPODia
perinteiseen PPE:n:
In this study, when the ResQPOD was used in combination
with active compression decompression cardiopulmonary resuscitation (ACD-CPR),
patients had a 53% improvement in survival to hospital discharge with
favorable neurologic outcome, and this survival benefit persisted to one
year.
Findings
2470 provisionally enrolled patients were randomly allocated to treatment
groups. 813 (68%) of 1201 patients assigned to the standard CPR group (controls)
and 840 (66%) of 1269 assigned to intervention CPR received designated CPR
and were included in the final analyses. 47 (6%) of 813 controls survived to
hospital discharge with favourable neurological function compared with 75
(9%) of 840 patients in the intervention group (odds ratio 1·58, 95% CI
1·07—2·36; p=0·019]. 74 (9%) of 840 patients survived to 1 year in the
intervention group compared with 48 (6%) of 813 controls (p=0·03), with
equivalent cognitive skills, disability ratings, and emotional-psychological
statuses in both groups. The overall major adverse event rate did not differ
between groups, but more patients had pulmonary oedema in the intervention
group (94 [11%] of 840) than did controls (62 [7%] of 813; p=0·015).
Interpretation
On the basis of our findings showing increased effectiveness and
generalisability of the study intervention, active compression-decompression
CPR with augmentation of negative intrathoracic pressure should be
considered as an alternative to standard CPR to increase long-term survival
after cardiac arrest.
