Intrathoracic cardiac compression

Details Intrathoracic cardiac compression Intrathoracic cardiac compression

1998-12-09

2001-02-27

DeMille, Danton D. (Department: 3764)

Surgery: kinesitherapy

Kinesitherapy

Device with applicator having specific movement

C606S192000, C606S196000, C604S098020, C604S097020, C604S099010

Reexamination Certificate

active

06193680

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and devices for performing cardiopulmonary resuscitation, and is more specifically related to intrathoracic cardiac compression during cardiac resuscitation.
BACKGROUND OF THE INVENTION
Cardiopulmonary resuscitation (CPR) is widely used in clinical medicine to maintain perfusion of vital organs during episodes of sudden cardiac arrest when the heart stops spontaneously beating (asystole). Any period of prolonged asystole (such as from ventricular fibrillation) can cause irreversible hypoxic damage to vital end organs (such as the brain and heart) that are not perfused during the asystolic episode. CPR can often maintain a sufficient level of arterial oxygenation and blood flow to avoid irreversible end organ damage and death, at least until spontaneous cardiac activity resumes or external ventricular defibrillation converts the cardiac rhythm to a more effective electrocardiographic pattern.
The components of CPR usually include external cardiac compressions and pulmonary ventilation. The external cardiac compressions are achieved by repetitively forcing the sternum against the heart to compress the heart between the sternum and vertebral column. Manual chest compressions also produce a positive intrathoracic pressure and enhance emptying of the heart, possibly by reducing afterload of the left ventricle. Cardiac compressions are usually only interrupted to administer mouth-to-mouth or mechanical ventilation, which cyclically inflates the lungs to achieve oxygenation of the blood, or to attempt electrical cardioversion of the fibrillating heart.
Although CPR has improved initial survival of episodes of sudden cardiac death, its effectiveness is less than optimal. External compression of the heart, for example, is not as effective as surgically opening the chest and performing direct manual compression of the heart. Several studies have estimated that in-hospital CPR is effective in only 10-15% of patients. Open chest cardiac massage can better achieve normal or supranormal cerebral blood flows, which are associated with improved neurologic recovery from the cardiac event. Such dramatic surgical intervention is not usually available, however, and even in a hospital setting is often impractical or not feasible. The inability of closed chest CPR to maintain adequate levels of cerebral blood flow is the principal reason for the low survival rates and poor neurologic recovery often associated with CPR. Moreover, external chest compressions frequently cause significant morbidity, such as broken ribs or a fractured sternum.
Both external (closed chest) and surgical (open-chest) techniques of cardiac compression can be performed manually, or with the aid of mechanical devices. With either technique, the goal is to maintain artificial circulation, including perfusion of cerebral and coronary arteries, until spontaneous cardiac activity can be restored. An example of an intrathoracic cardiac massager is shown in U.S. Pat. No. 3,496,392, which discloses an inflatable bladder for insertion between the sternum and heart. After intrathoracic placement, the inflatable bladder is cyclically inflated and deflated to achieve cardiac compression.
U.S. Pat. No. 3,233,607, U.S. Pat. No. 3,478,737, U.S. Pat. No. 4,536,893, U.S. Pat. No. 5,119,804 and U.S. Pat. No. 5,383,840 all disclose mechanical devices that surround and engage the ventricular regions of the myocardium to provide auxiliary cardiovascular support for impaired myocardium. U.S. Pat. No. 5,385,081 shows a similar device, but the device is placed in the intrapericardial space. U.S. Pat. No. 5,484,391 describes a substernal heart massaging plunger that is surgically inserted through an intercostal space to compress the heart.
Although these and other heart compressing devices effectively achieve arterial perfusion, they require surgical placement that is often unavailable or impractical in emergency outpatient or clinical settings. Moreover, surgical procedures performed under emergency conditions often inadvertently and unavoidably introduce infectious pathogens into the patient, which can frustrate or prevent recovery.
Other devices have been developed to assist with external cardiac compression, and that avoid the necessity of surgical placement. U.S. Pat. Nos. 5,490,820 and 5,453,081, for example, both disclose external, vest-like devices that are worn by a patient to provide external chest compressions that promote movement of blood from the heart.
None of these devices have been able to provide an approach that combines the effectiveness of intrathoracic cardiac compression with the convenience and availability of external compression devices.
Accordingly, it is an object of this invention to provide an apparatus and method that achieves superior cardiac compression during episodes of ineffective cardiac contraction or asystole.
Yet another object is to provide such an apparatus and method that performs cardiac compression without the necessity of surgical intervention.
These and other objects of the invention will be understood more clearly by reference to the following detailed description and drawings.
SUMMARY OF THE INVENTION
The foregoing problems have been overcome by providing a device for performing intrathoracic transesophageal cardiac compression. The device includes an esophageal tube of suitable size and flexibility to be introduced into the esophagus. An inflatable compression member (such as a balloon) is provided on the esophageal tube. The esophageal tube is of sufficient length to allow the inflatable member to be introduced into the esophagus to a distance that disposes the inflatable member between the heart and vertebral column. The inflatable member has sufficient volume to compress the heart an effective volume (for example 200 cc) to perform therapeutically effective transesophageal cardiac compressions during CPR. A pump connected to the esophageal tube cyclically inflates and deflates the inflatable compression member at a sufficient frequency to restore adequate circulatory blood flow.
In a disclosed embodiment, the inflatable member is a distensible bladder or balloon that can expand to a volume of approximately 200-250 cc. The pump may be a hand-held resilient collapsible and expandable pumping chamber that is compressed to expand the inflatable member, and allowed to expand to deflate the inflatable member. The hand-held pump includes a check valve that allows air to be drawn into the pumping chamber if the pressure in the chamber exceeds a preselected negative value, and allows air to be expelled from the pumping chamber if pressure in the chamber exceeds a preselected positive pressure. Alternatively, the pump can be a rapidly cycling electrically powered or hydraulic actuated air pump. Another alternative method of cyclical inflation of the esophageal balloon is the use of a bottle of compressed air with a pressure regulated valve.
In one embodiment, the rapidly cycling pump includes a reciprocating pump piston that defines a variable volume gas chamber, the volume of which is varied by movement of the pump piston. The pump piston is driven by a separate drive piston, which is reciprocated in response to a hydraulic signal that can be rapidly changed to cycle the pump at the desired frequency. A delay mechanism can prolong the pumping cycle, for example by interposing a delay of approximately 250-300 milliseconds, between deflation and inflation of the esophageal balloon. This delay allows end diastolic filling of the heart to take place more efficiently than would occur if the pump constantly cycled without a pause between inflation and deflation of the balloon.
The invention also includes a method of performing transesophageal cardiac compressions by providing the inflatable member on an esophageal tube, and then introducing the inflatable member into the esophagus a sufficient distance to dispose the inflatable member between the heart and vertebral column. The inflatable member is then cyclically inflated and deflated a sufficient

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