Search PubMed⌕ Search

Biomedical subjects

C F Babbs

Publications and source records attributed to C F Babbs.

At least 91 records · Page 5Linked to original sources
PubMed1985

Gastric insufflation during IAC-CPR and standard CPR in a canine model.

This study was undertaken to determine the effect of interposed abdominal compressions (IAC) during cardiopulmonary resuscitation (CPR) on gastric insufflation when the airway is not secured with an endotracheal tube. A canine model was used in which a common ventilation pressure was applied to separate cuffed esophageal and tracheal tubes. Gas entering the stomach was collected by a pre-placed gastrostomy tube leading to a bell spirometer. Gas entering the lungs was measured with a Wright Respirometer in series with the endotracheal tube. During standard CPR, measurable gastric gas volume was collected in 28 of 30 trials (mean 215 +/- 93 ml/ventilation). During IAC-CPR, in which abdominal pressure was maintained during ventilation after every 5th chest compression, measurable gastric gas was collected in 15 of 30 trials (mean 40 +/- 11 ml/ventilation). Interposed abdominal compressions as an adjunct to standard CPR may not only be of hemodynamic benefit, but may also reduce the incidence of gastric insufflation and attendant complications.

Abdomen↗
PubMed1985

Abdominal counterpulsation in cardiopulmonary resuscitation: animal models and theoretical considerations.

Abdominal counterpulsation improves blood flow during otherwise standard CPR in animal models and in electronic models of the circulation. The method generates both central aortic and central venous pressure pulses. Success depends upon maximizing the former and minimizing the latter. Solution of a simple, first-order, differential equation may provide insight into proper technique. The equation suggests that the central arteriovenous pressure difference is maximized when pressure is applied directly over the abdominal aorta and when fluid loading is avoided. Proper technique may be critical in generating the largest possible arteriovenous pressure difference.

Abdomen↗
PubMed1985

Electroventilation.

Electroventilation is a term used to describe the production of inspiration by applying rhythmic bursts of short duration stimuli to extrathoracic electrodes to stimulate motor nerves to the inspiratory muscles. In the dog, the optimum site for the electrodes was found to be on the upper chest wall, bilaterally. The inspired volume increased with increasing current intensity. The maximum tidal volume attainable was about four times resting tidal volume. The ability of electroventilation to maintain arterial blood oxygen saturation without the production of cardiac arrhythmias was demonstrated in pentobarbital-anesthetized dogs. The technique has several potential applications and offers promise in emergency and critical-care medicine.

Animals↗
PubMed1985

Writing a scientific paper prior to the research.

We propose that many potential pitfalls of a research study can be brought to light through the exercise of writing a zeroth draft of the paper before beginning formal data collection. Further, because the zeroth draft of the paper contains the elements required in most research proposals--background, rationale, approach to data analysis, methods, and significance--it may serve as a generic grant application that can be easily recast in the style required by a specific funding agency. Moreover, the task of preparing the final report after completing the study is a shorter, less painful process if one has only to revise the zeroth draft rather than face the blank page. In these ways writing the scientific paper before gathering the data can help an investigator plan, fund, execute, and report a study that asks and answers specific and important questions.

Adolescent↗
PubMed1985

Role of iron ions in the genesis of reperfusion injury following successful cardiopulmonary resuscitation: preliminary data and a biochemical hypothesis.

Presented is a rationale for use of a new class of drugs, the iron chelating agents, in advanced cardiac life support (ACLS) to prevent late deaths and brain damage following successful cardiopulmonary resuscitation. The relevant biochemical hypothesis states that free iron ions, liberated from bound intracellular stores during ischemia, catalyze initiation of free radical mediated reactions that propagate through membrane lipids and proteins. Progressive ultrastructural damage may result, ultimately causing deterioration of function and death. Chelation of intracellular iron by deferoxamine, a commercially available drug that distributes to the intracellular space and has a great affinity for iron ions, may prevent such reactions. A hypothesis concerning relevant pathological chemistry is developed in detail.

Animals↗
PubMed1985

Endotracheal versus intravenous epinephrine during electromechanical dissociation with CPR in dogs.

The dose-response curves of epinephrine given either IV or endotracheally (ET) were compared during resuscitation from electromechanical dissociation (EMD). Ten anesthetized dogs were subjected to a two-minute period of electrically induced ventricular fibrillation (VF) followed by defibrillation without CPR to produce EMD. Mechanical CPR was followed by injection of either ET or IV epinephrine. Successful response was defined as a return of pulsatile blood pressure within two minutes of drug administration. Using log-dose increments of epinephrine, experimental trials were repeated in each animal. The IV and ET median effective doses were 14 and 130 micrograms/kg, respectively. When the trials were successful, the time between drug administration and either arterial blood pressure increases or return of spontaneous circulation did not differ significantly for the ET and IV groups. These results show that the dosage for epinephrine delivered ET must be higher than the IV dosage to achieve the same response during CPR.

Animals↗
PubMed1985

Manual versus mechanical cardiopulmonary resuscitation in an experimental canine model.

Manual and mechanical chest compressions during CPR were compared in the canine model. Endpoints were hemodynamics produced during CPR, resuscitation success at 30 min, 24-h survival, neurologic function of survivors, and CPR-produced trauma. Ten animals in each group underwent 20 min of ventricular fibrillation, during which CPR was performed for 17 min. Hemodynamics produced with manual and mechanical chest compressions were similar. Seven of ten animals in each group were resuscitated. Five animals from the manual group and four animals from the mechanical group survived for 24 h. Neurologic function of survivors was excellent and similar in each group. There was no significant difference in trauma between the two types of chest compression. The similar results for manual and mechanical chest compression in this canine model suggest that different experimental CPR studies can be compared regardless or whether manual or mechanical chest compressions were performed.

Animals↗
PubMed1985

Choice of the optimum pulse duration for precordial cardiac pacing: a theoretical study.

In precordial pacing with skin-surface electrodes, the goal is to excite the ventricles with minimal stimulation of overlying tissues. A theoretical analysis is presented to identify the relevant factors; the two most important are electrode location and pulse duration. Using the basic law of stimulation, we developed a model which indicates that the optimum pulse duration for the closed-chest pacing pulse is one that is long with respect to the membrane time constant of cardiac muscle. Current-versus-duration curves are presented for pacing and pain, based on experimentally obtained data. For pacing with minimum pain, the optimum stimulus duration was found to be about 10 ms.

Adult↗
PubMed1985

Correlation of the cardiogenic air flow in the respiratory airway (i.e. the pneumocardiogram) with left ventricular stroke volume in dogs.

The pneumocardiogram (PNCG) is a record of the pulsatile flow of air in the trachea coincident with each heart beat. In 5 anesthetized mongrel dogs, the cardiogenic air flow through an endotracheal tube was measured with a research pneumotachograph. The correlation between the pneumocardiographic volume of air, obtained by integrating the PNCG over the period of ventricular ejection, and stroke volume (SV), measured by the saline-dilution method, was determined for a physiologic range of SV. Although the pneumocardiographic volume tracked measured SV, the former was always less. The range of correlation coefficients was 0.60 to 0.91. The results suggest that the PNCG may be suitable for continuous tracking of changes in SV on a noninvasive, beat-by-beat basis. The technique is ideally applicable to intubated human subjects, particularly those undergoing closed-chest surgical procedures.

Animals↗
PubMed1984

Cardiac, thoracic, and abdominal pump mechanisms in cardiopulmonary resuscitation: studies in an electrical model of the circulation.

To investigate alternative mechanisms generating artificial circulation during cardiopulmonary resuscitation (CPR), an electrical model of the circulation was developed. Heart and blood vessels were modeled as resistive-capacitive networks; pressures in the chest, abdomen, and vascular compartments as voltages; blood flow as electric current; blood inertia as inductance; and the cardiac and venous valves as diodes. External pressurization of thoracic and abdominal vessels, as would occur in CPR, was simulated by application of half-sinusoidal voltage pulses. Three modes of creating artificial circulation were studied: cardiac pump (CP), in which the atria and ventricles of the model were pressurized simultaneously; thoracic pump (TP), in which all intrathoracic elements of the model were pressurized simultaneously; and abdominal pump (AP), in which the abdominal aorta and inferior vena cava of the model were pressurized simultaneously. Flow was greatest with the CP, less with the TP, and least with the AP mechanism. However, the AP could be practically combined with either the CP or TP by interposition of abdominal compressions between chest compressions (IAC-CPR). Our model predicts that this combined method can substantially improve artificial circulation, especially when cardiac compression does not occur and chest compression invokes only the thoracic pump mechanism.

Abdomen↗
PubMed1984

An experimental circulatory arrest model in the rat to evaluate calcium antagonists in cerebral resuscitation.

A circulatory arrest model in the rat was developed for use in cerebral and cardiac resuscitation studies. Whole-body ischemia was produced for 8 to 18 minutes by arresting the heart with a cold potassium chloride cardioplegic solution. Following cardiopulmonary resuscitation, minimal, standardized intensive care was provided. As the duration of ischemia was increased from 8 to 18 minutes, survival immediately following resuscitation decreased from 100% to 25%, and survival at 48 hours after ischemia decreased from 60% to 0%. Thirty per cent of the rats recovering from 11 minutes of ischemia suffered motor seizures. Survival and the incidence of motor seizures appear to be good measures of outcome following ischemic circulatory arrest. These measures can be used to test the possible anti-ischemic actions of calcium antagonists or other drugs.

Animals↗
PubMed1984

Preclinical studies of abdominal counterpulsation in CPR.

Abdominal counterpulsation added to standard cardiopulmonary resuscitation improves blood flow in animal models when compared to chest compressions alone. Similar effects can be demonstrated in analog and digital computer models of the circulation. The technique generates both central aortic and central venous pressure pulses, and successful application of the method depends on maximizing the former and minimizing the latter. Proper technique is important in order to generate the largest possible arteriovenous pressure difference.

Abdomen↗
PubMed1984

Intrapulmonary epinephrine during prolonged cardiopulmonary resuscitation: improved regional blood flow and resuscitation in dogs.

Blood flow to vital organs was measured at five-minute intervals during 20 minutes of cardiopulmonary resuscitation (CPR) and ventricular fibrillation in two groups of anesthetized dogs (n = 15 per group). The relationship between organ blood flow and restoration of circulation after 20 minutes was assessed with no additional treatment in Group I and with intrapulmonary epinephrine in Group II. Cardiac output and organ blood flow did not vary significantly in Group I. In Group II, intrapulmonary epinephrine significantly improved blood flow to the myocardium, the brain, and the adrenals. A mean myocardial blood flow of less than 0.13 mL/min/g resulted in no survival, while a flow of greater than 0.16 mL/min/g resulted in survival. These studies show that a critical level of myocardial blood flow is required to restore ability of the heart to function as a pump after prolonged CPR, and that a drug that increases flow improves resuscitation efforts.

Animals↗