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Biomedical subjects

A C Pinchak

Publications and source records attributed to A C Pinchak.

35 records · Page 2Linked to original sources
PubMed1995

The effect of fiberoptic bronchoscopy on cerebral hemodynamics in patients with severe head injury.

STUDY OBJECTIVE: Concerns exist about the effect of flexible fiberoptic bronchoscopy (FFB) on intracranial pressure (ICP). We studied the effect of FFB on cerebral hemodynamics in patients with severe head injury. DESIGN: Prior to FFB, patients were anesthetized and muscle relaxants were given as necessary to eliminate coughing. Comparisons were made of mean arterial pressure (MAP), ICP, and cerebral perfusion pressure (CPP) prior to, during, and after FFB, as well as comparisons of mean cerebral hemodynamic values in an 8-hour period before and after FFB. Observations were made of changes in neurologic status post-FFB. SETTING: Surgical intensive care unit of Level 1 Trauma Center. PATIENT POPULATION: Fifteen patients with severe head injury in whom ICP was monitored and who required FFB for diagnosis of nosocomial pneumonia or treatment of lobar collapse. RESULTS: Pre-FFB ICP averaged 14.3 mm Hg (range, 6 to 26 mm Hg). During FFB, patients experienced a mean increase in ICP of 13.5 mm Hg above basal values (p = 0.0001). At peak ICP, MAP increased from a baseline of 92.3 mm Hg (SD +/- 16.1) to 111.5 mm Hg (+/- 13.9). Mean CPP was 83.7 mm Hg at peak ICP (range, 52 to 121 mm Hg), a 14.0% increase over baseline. The ICP and MAP returned to basal levels following bronchoscopy. No patient had a clinically significant increase in ICP or demonstrated any deterioration in Glasgow Coma Scale score or neurologic examination findings post-FFB. CONCLUSIONS: Although FFB causes an increase in ICP in patients with severe head injury, MAP also rises, and an adequate CPP is maintained. The ICP returns to basal levels after the procedure. When properly performed, FFB does not adversely affect neurologic status in patients with severe head injury.

Acute Disease↗
PubMed1994

Waiting time after non-depolarizing relaxants alter muscle fasciculation response to succinylcholine.

The purpose of the study was to determine the effect of nondepolarizing muscle relaxants and waiting time on muscle fasciculations after succinylcholine in anaesthetized patients. Adult men and women, 60-80 kg, received pretreatment doses of atracurium 5 mg (n = 160), pancuronium 1 mg (n = 123), d-tubocurarine 3 mg (n = 97), or vecuronium 1 mg (n = 62). Waiting times between pretreatment and succinylcholine, 100 mg, ranged between 0.6 and 5 min. Data points (presence or absence of fasciculations and waiting time) were entered for each patient. Waiting time response curves were obtained between the logit transformation of the probability of no fasciculations and the log waiting time for each drug. Statistical differences between wait time response curves were determined by non-overlapping of the associated 95% confidence intervals. The frequency of muscle fasciculations was reduced with increased waiting time for all nondepolarizers tested. Following wait times of three, four and five minutes, the probability of not fasciculating was greatest with d-tubocurarine (90, 97 and 99%, respectively) and atracurium (89, 93 and 96%). Corresponding values for pancuronium were 70, 82 and 88% and for vecuronium were 74, 82 and 86%. Waiting times to prevent fasciculations in 80% and 90% of patients were shorter with d-tubocurarine (2.46 and 3.02 min, respectively) or atracurium (2.16 and 3.24 min) than pancuronium (3.77 and 5.35 min) or vecuronium (3.73 and 6.36 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The influence of tape type and of skin preparation on the force required to dislodge angiocatheters.

The study evaluated the effects of different techniques used to secure intravenous (i.v.) catheters. An angiocatheter attached to standard i.v. tubing was taped to human forearm using a standard taping method. A calibrated piezoelectric force transducer was attached to the i.v. tubing. The force applied along the longitudinal axis to pull out the taped catheter was measured and recorded on paper. Three tape types, Curity, Leukopor and Transpore, were evaluated alone, with benzoin skin pretreatment and with mastisol pretreatment. A randomized 3 x 3 block design with 20 replications per block was utilized, and a total of 180 pullout tests were performed on two adult volunteers. Without pretreatment, the forces required to dislodge catheters were (means +/- SEM) 46 +/- 2, 37 +/- 2 and 38 +/- 2 Newtons for Curity, Leukopor and Transpore tape, respectively. Corresponding values for mastisol pretreatment (64 +/- 1, 64 +/- 3 and 52 +/- 3 Newtons) were greater (P < 0.05) for each tape compared with benzoin (54 +/- 3, 53 +/- 2 and 40 +/- 2 Newtons) and no pretreatment. The most frequent failure mode for Transpore tape was by tape fracture, for Curity tape was by separation from the skin of tape and catheter as a single unit, and for Leukopor tape was by catheter separation while tape remained attached to skin (P < 0.001). The data suggest that the application of mastisol prior to taping i.v. catheters with Curity or Leukopor tape helps to minimize the risk of accidental dislodgement.

Adhesiveness↗
PubMed1990

Dye circulation times during cardiac arrest.

Dye dilution curves have been used to calculate cardiac output under conditions of normal circulation. Unfortunately, these curves cannot be integrated easily to determine cardiac output under the low flow states of CPR. The time to initial dye appearance (circulation time), may be useful in judging relative changes in flow when studying experimental resuscitation techniques. The purpose of this study was to investigate the relationship between dye circulation times and other hemodynamic measures during CPR. Repeated measurements of coronary perfusion pressure, dye circulation times, blood gases, and end-tidal CO2 (ETCO2) were made in dogs undergoing CPR. Dye circulation time was significantly associated with the systolic, diastolic, and coronary perfusion pressures. The correlation between circulation time and ETCO2 was -0.70 (P less than 0.0001). There was no correlation with the arterial-venous PO2 gradient. There were significant correlations between the circulation time and both the A-V PCO2 and the A-V pH gradients. We conclude that dye circulation times may be used to gauge relative changes in blood flow during CPR, particularly in laboratory investigations involving repeated measurements.

Animals↗
PubMed1990

The effect of bolus injection on circulation times during cardiac arrest.

Previous investigations have shown that peripheral injection of medication during cardiac arrest leads to prolonged circulation times and low peak drug levels. Current Advanced Cardiac Life Support guidelines suggest that administering a bolus of flush solution after injection of medication may hasten drug delivery, but there is little evidence to support this. The purpose of this study is to investigate the effect of peripheral bolus injection on circulation times during cardiac arrest. Measurements of circulation times were made following injection of indocyanine green dye both with and without a bolus of 20 mL saline flush into a peripheral vein of mongrel dogs. There was no difference in systolic, diastolic, or coronary perfusion pressures during the injections with or without bolus injection. Similarly, there was no difference in end-tidal CO2 or in arterial-venous PO2, PCO2, or pH gradient. The circulation time without bolus injection was 77.7 +/- 42.7 seconds while circulation time with the saline flush was 48.3 +/- 20.9 seconds (P less than .001). Peak dye concentration without saline flush was 3.0 +/- 1.0 mg/L, and peak dye concentration with saline flush was 3.8 +/- 0.9 mg/L (P less than .001). We conclude that a bolus injection of 20 mL of saline enhances dye circulation times and peak levels during cardiac arrest in this animal model. The clinical application of this technique warrants further investigation.

Animals↗
PubMed1989

Hemodynamic effects of the intra-aortic balloon pump during experimental cardiac arrest.

The low flow states and limited coronary perfusion provided by conventional cardiopulmonary resuscitation (CPR) have prompted investigations into alternative, more invasive, methods of resuscitation. Previous case reports and limited animal evidence have suggested that the intra-aortic balloon pump (IABP) may have a role in resuscitation. We used a canine cardiac arrest model to study the hemodynamic effects of the IABP during closed-chest CPR. A sensor attached to the chest plate of a Thumper was used to time a Datascope Model 3520 ventricular assist console such that the balloon inflated on the upstroke and deflated on the downstroke of the Thumper. There was no increase in systolic blood pressure with the balloon pump. Diastolic blood pressure and coronary perfusion pressure were significantly higher with the IABP. Circulation times were shorter and end-tidal CO2 was higher with the IABP. It was concluded that the IABP improves hemodynamic parameters during experimental cardiac arrest.

Animals↗
PubMed1988

A comparison of venous blood gases during cardiac arrest.

Previous reports have advocated the use of mixed venous blood gases to estimate arterial pH and as a reflection of tissue acid-based balance. However, true mixed venous samples are difficult to obtain during cardiac arrest as they require a pulmonary artery catheter. The purpose of this study was to determine whether central or femoral venous samples could be used in place of pulmonary artery samples. Blood gases from these sites were drawn at intervals during experimental cardiac arrest in dogs. The PO2, PCO2, and pH from the pulmonary artery samples were strongly correlated with those from the central venous (r = .93, .99, and .99, respectively) and from the femoral venous samples (r = .73, .93, and .97, respectively). There were no significant differences in the pulmonary artery, central, or femoral venous gases. This animal model suggests that femoral and central venous samples mirror true mixed venous blood gases from the pulmonary artery and could be used in their place.

Animals↗
PubMed1988

Chest wall acceleration and force measurements in simulated manual and mechanical cardiopulmonary resuscitation.

During CPR, the dynamics of the chest compression process play a major role in determining the outcome of the resuscitation effort. To quantify chest wall motion during CPR, a number of important variables must be determined, including maximum downward acceleration and velocity of the chest wall, time during which the wall is held in compression, and maximum depth and rate of chest compression. In this study, miniature accelerometers were used to record chest wall motion during simulated CPR with standard training manikins. One series of CPR tests included force measurements from a three-dimensional force platform placed under the manikin. The results of this investigation showed that American Heart Association (AHA)-certified rescuers are able to produce a consistent pattern of chest wall displacement during a manikin training exercise, and only small differences in displacement recordings are found when comparing one certified rescuer to another. Any given rescuer will usually generate a consistently repeatable acceleration pattern during CPR. However, these cyclical acceleration patterns differ markedly when comparing different certified rescuers. Mechanical CPR with a standard device produced larger peak accelerations than manual CPR. However, the maximum downward velocity was usually higher with manual CPR. In comparison with trained but clinically inexperienced individuals, rescuers with extensive in hospital experience produced relatively larger downward accelerations, longer "hold" times with the chest in compression, and maximum chest displacements that exceeded the current AHA recommendations. Measurements of the force transmitted through the manikin to a force platform clearly indicated the presence of a "hold" phase (if present) and the existence of large force components in the horizontal plane.

Acceleration↗
PubMed1988

Effect of injection site on circulation times during cardiac arrest.

Cardiopulmonary resuscitation requires effective, prompt drug administration. In order to analyze Advanced Cardiac Life Support (ACLS) recommendations for site of drug administration, we studied dye circulation times after central, femoral, and peripheral venous injection during both closed and open chest CPR using a canine arrest model. Measurements of circulation times were made after injection of indocyanine green dye at femoral, central, and peripheral venous sites. Circulation times during closed chest CPR were 62.7 +/- 19.6 sec after central injection, 86.6 +/- 23.5 sec after femoral injection, and 93.6 +/- 17.9 sec after peripheral injection (p less than .001). During closed chest CPR, peak dye concentration after central injection was significantly higher than that after peripheral injection (4.0 +/- 1.3 vs. 3.1 +/- 0.8 mg/L, p less than .01). Circulation times were significantly shorter during open chest CPR with times again shortest after central injection. This animal model suggests that prompt drug delivery during CPR is enhanced by central venous injection of medication. There appears to be no advantage in femoral over peripheral injection.

Animals↗
PubMed1984

Beat frequencies in high-frequency positive-pressure ventilation.

Amplitude modulation of the waveforms of several cardiovascular variables was investigated during high-frequency (1.3 to 3.3 Hz) positive-pressure ventilation (HFPPV). The amplitude modulation of the pulmonary artery pressure wave was most prominent and its beat frequency (BF) was equal to the difference between the heart rate and the ventilation rate. Spectral analysis of the pulmonary artery pressure demonstrated well-defined peaks associated with the BF. No significant physiologic changes in either cardiovascular or pulmonary function were attributable to the presence of the beat phenomenon.

Animals↗
PubMed1984

High-frequency positive-pressure ventilation with the MA-1 ventilator.

A conventional, low-frequency ventilator was modified to ventilate dogs at high frequencies of 85 to 185 cycle/min while cardiovascular and pulmonary variables were monitored. Although gas transport was adequate, cardiac output was diminished when compared to low-frequency ventilation. The addition of an in-line pneumotachograph markedly increased PaCO2 during high-frequency ventilation. Carbon dioxide transport was primarily dependent upon the magnitude of the tidal volume at all high frequencies tested.

Animals↗
PubMed1984

Flow-monitoring system for high-frequency ventilation.

With the addition of appropriate logic circuitry and a single-board microcomputer, a thermistor flowmeter becomes a clinically useful ventilation monitor. The microcomputer calculates upper and lower reference (voltage) levels from the baseline (normal) flow signal generated by the thermistor bridge. If the flow signal fails to pass repetitively through one or both of these reference levels, visual and audio alarms are generated. Tests performed with both high-frequency (3 Hz) and low-frequency (0.2 Hz) ventilator systems show the usefulness of this system in sensing a variety of malfunctions, including endotracheal tube occlusions, leaks, changes in flow or tidal volume, and hose disconnects.

Humans↗
PubMed1983

Mechanical aspects of epidural catheter insertion--prevention of catheter buckling by means of a needle hub insert.

Six commercially available epidural catheters were tested in a special apparatus designed to simulate epidural catheter insertion and quantitatively measure the buckling strength of these catheters. The experimental apparatus utilized a modified Tuohy needle and a specially calibrated force transducer. Catheters were inserted through the Tuohy needle in a manner similar to that employed clinically, and the maximum forces developed against the surface of the force transducer were recorded electronically. In addition, a custom-designed "needle hub insert" was tested for its ability to prevent catheter buckling during insertion of an epidural catheter through a Tuohy needle. Catheter buckling forces were measured with new catheters and also with catheters that had been damaged by previous insertion attempts. Both the new and damaged catheters were tested with and without the presence of a needle hub insert. Each combination of experimental conditions was replicated four times. The results showed a marked difference in the effective buckling strength of the catheters tested. Buckling strengths ranged from a minimum of 201 +/- 21 g (SD) to 418 +/- 15 g of force. The largest forces were obtained with a Deseret type catheter that had an internal plastic stylet. When comparing only new catheters without stylets, the buckling forces ranged from 201 to 285 g. All catheters, whether new or damaged showed an increase in the maximum buckling force with the use of the needle hub insert. The percentage increase in force (needle hub insert vs. no insert) ranged from a low of 23% to a maximum of 108%.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Epidural↗
PubMed1976

Blood flow in branching vessels.

Flow visualization studies were conducted in a water-Plexiglas tube model which simulated flow conditions commonly encountered in major vessels. Complex secondary flow patterns in the main line downstream of a branching vessel were observed in found to be relatively independent of the diameter ratio and angle of departure of the branching tube. The ratio of branching to total flow was the prinicipal determinant of the aforementioned secondary flows. Venous and arterial branching markedly differed. Arterial-type flows produced a pair of vortex sinks downstream of the branching port. These vortex-sink flow fields, which previously have not been reported, captured fluid particles already downstream of the branching orifice and returned these particles upstream to exit via the branching tube. In a region very close to the tube wall, streamlines were also observed moving upstream to be captured by the branching vessel. The interaction of this local upstream flow with the general downstream flow produced a pair of stagnation points located downstream and lateral to the branching orifice. These stagnation regions are discussed in relation to atheroma and thrombus formation.

Arteries↗
PubMedDate not supplied

Models for pulsed polarographic electrodes.

A simple model has been developed for analyzing the pulsed polarographic electrode. For short pulse durations the charge transfer kinetics must be incorporated into the boundary condition at the electrode surface. The predicted velocity dependence for long pulse durations is in good agreement with experimental data.

Electrodes↗