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Biomedical subjects

L Bunegin

Publications and source records attributed to L Bunegin.

At least 37 records · Page 2Linked to original sources
PubMed1988

Continuous-flow apneic ventilation with small endobronchial catheters.

This study compares gas exchange and hemodynamic parameters during bronchial insufflation with two different internal diameter (ID) catheters (2.5 and 1.4 mm) at a constant mean gas exit velocity. Anesthetized, paralyzed dogs were instrumented to monitor arterial, central venous, and airway pressures, blood gases, temperature, ECG, and ventilated using continuous flow apneic ventilation (CFAV) via 2.5-mm or 1.4-mm ID bronchial insufflation catheters positioned 1.25 bronchial diameter units (BDU) beyond the carina. Initially, flow was adjusted to provide adequate oxygenation and ventilation through the 2.5-mm ID catheters. After a 30-min stabilization, physiological parameters were recorded and the mean gas exit velocity was calculated. The 2.5-mm ID insufflation catheters were then replaced by 1.4-mm ID catheters and the bronchial insufflation flow adjusted so as to produce the same mean gas exit velocity as for the 2.5-mm ID catheters. After a 30-min stabilization period, physiological parameters were again recorded. No significant differences were noted in arterial, central venous, or airway pressures, temperature, heart rate, pH, PaCO2, and PaO2 between the 2.5-mm and 1.4-mm ID bronchial insufflation catheters. However, significantly less bronchial insufflation flow (69.7%) was required to maintain oxygenation and ventilation for the 1.4-mm ID bronchial insufflation catheters.

Animals↗
PubMed1987

Gas exchange in low-compression HFPPV is maintained at low distending pressures in the pig.

The fact that collateral ventilation normally occurs in the human lung has led to the suggestion that it might contribute to the successful clinical effects of low-compression high-frequency positive-pressure ventilation (HFPPV). As the pig has poor collateral ventilation, pulmonary vasoconstriction has to be part of the regulatory mechanisms matching ventilation-perfusion. A study was made on nine pigs anesthetized with ketamine hydrochloride intravenously to elucidate the maintenance of ventilation-perfusion balance during mechanical ventilation. Comparisons were made between the ventilatory patterns provided by a conventional ventilator (Servo-Ventilator 900C) and an improved prototype of a low-compression system for volume-controlled ventilation (system H). A ventilatory frequency of 20 breaths per min (bpm) with SV-900C (SV-20) and system H (H-20) and of 60 bpm with system H (H-60) was used. The experimental conditions were otherwise identical. Positive end-expiratory pressures (PEEP) were applied to maintain the same mean airway pressure with the three systems. The tidal volume required for normoventilation differed significantly between the three ventilatory patterns, but there were no differences in circulatory and oxygen-transport variables. By measurements of airway pressure and intrapleural liquid surface pressure, it was demonstrated that the distending pressure (at end-inspiration) was significantly lower with a low-compression system (H-20 versus SV-20), especially at a high ventilatory frequency (H-60 versus H-20). Consequently, although the mean airway pressure was set at the same level for the three different ventilatory modalities, the distending pressures required for the same alveolar ventilation and arterial oxygenation differed significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Intracranial pressure measurement from the anterior fontanelle utilizing a pneumoelectronic switch.

A newly developed infant cranial model shows that accurate, reproducible, and noninvasive measurements of intracranial pressure (ICP) can be made from the anterior fontanelle when fontanelle pressure is referenced from the bony margins adjacent to the fontanelle opening. Also, this model provides insight into the elastic properties of the fontanelle membrane and the pressure/volume relationships governing ICP transmission through the fontanelle window. An anterior fontanelle pressure monitor design based on data from the infant cranial model was used to monitor anterior fontanelle pressure in three infants with elevated ICP and previously inserted ventricular catheters. Measured anterior fontanelle pressure was highly correlated to ICP (r = 0.962) with high reproducibility after blind application and reapplication. Base line adjustment and in situ recalibration were easily achieved, with the monitor showing no sensitivity to patient movement and excellent frequency response.

Humans↗
PubMed1987

Biomechanics of spinal cord injury.

This article summarizes the biomechanical relationship of the spinal column to load stresses with respect to column failure, and the resulting associated central nervous system injury. In addition, it presents pertinent animal research, which has focused onto the development standardized animal spinal cord injury model.

Animals↗
PubMed1986

Continuous-flow apneic ventilation during thoracotomy.

Continuous-flow apneic ventilation (CFAV) by endobronchial insufflation of conditioned gas was evaluated in dogs during thoracotomy. In Group 1 (n = 6), dogs were anesthetized with pentobarbital (25 mg/kg). An endobronchial catheter (2.5 mm ID) was introduced into each mainstem bronchus using a fiberoptic bronchoscope and held in place by an endotracheal tube. Before the onset of CFAV (total flow 1.01 X kg-1 X min-1, the animals were paralyzed with pancuronium bromide and muscle relaxation was monitored with a peripheral nerve stimulator. The CFAV delivery system consisted of a flow meter, air/oxygen blender, oxygen analyzer, heated humidifier, and ultrasonic spirometer. Blood gas values were measured after 30 min of spontaneous ventilation, and CFAV with: 1) closed chest, fractional inspired O2 concentration (FIO2) 0.21; 2) open chest, FIO2 0.21; 3) open chest, FIO2 0.21, continuous positive airway pressure (CPAP) 5 mmHg; and 4) open chest FIO2 0.4, CPAP 5 mmHg. This last combination resulted in a mean PaO2 of 113.1 +/- 5.5 (SEM) mmHg and a PaCO2 of 35.0 +/- 2.1 (SEM) mmHg. In Group 2 (n = 6), animals with open chests were ventilated with CFAV (FIO2 0.4 and CPAP 5 mmHg) for 5 h. Adequate oxygenation and ventilation were achieved. PaCO2 after 5 h of CFAV was 41.8 +/- 1.9 (SEM) mmHg compared with 40.8 +/- 1.9 (SEM) mmHg during spontaneous breathing. PaO2 after 5 h of CFAV was 138.1 +/- 11.7 (SEM) mmHg. There were no significant changes observed in vascular pressures. Significant differences in other hemodynamic parameters were probably due to pentobarbital anesthesia. Adequate gas exchange can be achieved during CFAV in dogs with open chests for 5 h.

Animals↗
PubMed1986

An experimental study of craniocerebral trauma during ethanol intoxication.

This study evaluates the effects of ethanol (blood levels of 200 mg/dl for one hour) and dimethyl sulfoxide (DMSO) on cerebral lesion volumes after pressure-induced focal ischemia during normotension and induced hypotension in the canine. This experimental design simulates the situation where an individual imbibes two to four alcoholic drinks over a one-hour period, then drives a motor vehicle, and suffers a head injury either without significant blood loss or where the cerebral perfusion pressure is reduced to the lower limits of autoregulation (mean arterial pressure of 50 mm Hg). Ethanol was shown to increase brain lesion volumes in both the normotensive (4.5 +/- 0.7 cm3) and hypotensive (14.9 +/- 2.2 cm3) groups when compared to controls (0.8 +/- 0.3 and 2.9 +/- 0.4 cm3, respectively). DMSO markedly attenuated this response in the normotensive and hypotensive ethanol groups. It is thought that the intermediate metabolites of ethanol provide a large source of hydroxyl-free radicals in the presence of neuronal tissue damage and that these free radicals are effectively scavenged by DMSO.

Alcoholic Intoxication↗
PubMed1986

Effect of nitrogen on carbon dioxide elimination during continuous flow apneic ventilation in dogs.

Continuous endobronchial insufflation of air in paralyzed animals (continuous flow apneic ventilation - CFAV) has been shown to maintain adequate oxygenation and carbon dioxide removal. CFAV in patients using oxygen resulted in adequate oxygenation but a mean rise in PaCO2 of 0.6 mmHg/min (0.08 kPa/min). This experiment compared carbon dioxide removal in dogs with air and oxygen. Ten dogs were anesthetized and paralyzed, and CFAV was used for 1 h with either air or oxygen in a randomized fashion. Adequate oxygenation was obtained with air and oxygen. Normal PaCO2 levels were obtained with air; however, in the animals where oxygen was used, PaCO2 levels rose to a mean of 6.45 +/- s.e. mean 0.4 kPa (48.5 +/- s.e.mean 3.2 mmHg).

Air↗
PubMed1985

Brain and lungs at risk after cervical spinal cord transection: intracranial pressure, brain water, blood-brain barrier permeability, cerebral blood flow, and extravascular lung water changes.

The early physiopathologic responses to transection of the cervical spinal cord (C-4) were studied in the experimental animal. After transection, increases were seen in the mean arterial pressure, pulmonary capillary wedge pressure, intracranial pressure, brain water, blood--brain barrier permeability, and extravascular lung water with a marked decrease occurring in cerebral blood flow. Pretreatment with an alpha-adrenergic blocker, phentolamine (Regitine Ciba-Geigy Corp.), followed by transection blocked the rise in mean arterial blood pressure and pulmonary capillary wedge pressure but did not affect the increases in intracranial pressure, brain water, blood--brain barrier permeability, and extravascular lung water and decreases in cerebral blood flow. Transection of the cervical spinal cord initiates a complex series of events involving intracranial compliance and pulmonary permeability, placing both brain and lungs at risk.

Animals↗
PubMed1985

Conventional and high-frequency ventilation in dogs with bronchopleural fistula.

Seven anesthetized dogs with bronchopleural fistulas were subjected to a sequence of continuous positive-pressure ventilation (CPPV), volume-controlled high-frequency positive-pressure ventilation (HFPPV), and high-frequency vibratory ventilation (HFVV). Adequate short-term ventilation and oxygenation were possible with all three ventilatory modes. During HFPPV and HFVV, PaCO2 was unchanged, but hypercarbia developed during CPPV. PaO2 decreased during each mode of ventilation, but HFPPV maintained PaO2 at a sufficient and constant level during the 30-min test period. HFPPV was the most efficient technique with respect to delivery of minute ventilation, the relation between fistula flow and delivered ventilation, and maintenance of both ventilation and oxygenation.

Animals↗
PubMed1985

Spinal cord and cerebral blood flow responses to subarachnoid injection of local anesthetics with and without epinephrine.

Subarachnoid anesthesia with lidocaine, mepivacaine, or tetracaine with and without added epinephrine (1:100 000) produced no demonstrable changes in average cerebral (CBF) or segmental spinal cord blood flow (SCBF) in 38 cats anesthetized with pentobarbital. Blood flow was measured by the injection of radioactive microspheres. Seven groups of cats received either lidocaine 15 mg, lidocaine 15 mg with epinephrine, mepivacaine 10 mg, mepivacaine 10 mg with epinephrine, tetracaine 5 mg, tetracaine 5 mg with epinephrine, or saline with epinephrine 1:100 000. Mean arterial pressure (MAP) decreased significantly (P less than 0.05) in Groups I-VI. Added epinephrine had no effect on the decrease in MAP. Amplitude of the somatosensory cortical evoked response decreased significantly in Groups I-VI, but did not change from control in Group VII. No significant change in CBF or SCBF was demonstrated in any group at any time. Plasma lidocaine and mepivacaine levels were significantly less at 5 min after subarachnoid injection in the groups receiving epinephrine compared to those not receiving epinephrine (P less than 0.05). The data appear to support the hypothesis of a vasoconstrictive reduction in systemic absorption of intrathecal local anesthetics, but suggest that significant segmental spinal cord ischemia does not occur. Maintenance of total flow in the face of a decrease in MAP suggests that autoregulation in brain and spinal cord may be maintained. Changes in regional SCBF or CBF may have been present but were not examined in this study. Further studies of brain and spinal cord blood flow dynamics, regional flow changes, and regulation of flow after intrathecal agents are necessary.

Anesthesia, Spinal↗
PubMed1984

Verification of global cerebral ischaemia using scintigraphy.

The induction of global cerebral ischaemia in laboratory animals is difficult to accomplish and has been even more difficult to verify. Most reported verification methods suffer from lack of sensitivity or from being traumatic and highly invasive. We describe a non-traumatic global cerebral ischaemia verification technique which is quantitative, simple, and highly sensitive. Radioactive technetium-99m pertechnetate is injected intravenously during the ischaemic phase of an experiment and the appearance of radioactivity within the animal's head is quantitated using a gamma camera and nuclear medicine computer. Radioactivity levels below the visual perception threshold are readily measured, thus providing a high degree of confidence in assessing the partial or total nature of cerebral ischaemia.

Animals↗
PubMed1984

Regional organ blood flow during high-frequency positive-pressure ventilation (HFPPV) and intermittent positive-pressure ventilation (IPPV).

The effect of high-frequency ventilation (HFV) on cerebral blood flow (CBF) at normal and elevated intracranial pressure (ICP) was compared with flows measured under the same conditions during intermittent positive pressure ventilation (IPPV). Renal, lung (bronchial artery supply), and cardiac blood flows also were measured during HFV and compared with flows observed during IPPV. Measurements were made in canines with stable hemodynamic variables and arterial CO2 and O2 tensions in the normal range, CBF during HFV was comparable to the CBF during IPPV. Following an increase in ICP to a mean of 44 +/- 18 mmHg (SD), mean CBF decreased to 22.5 +/- 11 ml . 100 g-1 . min-1 (SD) during IPPV and 21.7 +/- 13.2 ml . 100 g-1 . min-1 (SD) during HFV. No statistical differences could be noted in regional or global flow as a function of ventilatory mode. Renal, lung (bronchial artery supply), and cardiac blood flows also showed no statistical variation between HFV and IPPV. Ventilator-synchronous fluctuations in ICP observed during IPPV were reduced during HFV at normal ICP and eliminated by HFV at elevated ICP.

Animals↗
PubMed1984

Percutaneous transtracheal jet ventilation for cardiopulmonary resuscitation: evaluation of a new jet ventilator.

This study compared percutaneous transtracheal jet ventilation (PTJV) at a frequency (f) of 20/min, with high-frequency positive-pressure ventilation (HFPPV) at f of 60/min, and endotracheal intubation and intermittent positive-pressure ventilation (ET IPPV) at f of 10/min in apneic dogs. Fifty-four emergency medicine trainees (EMTs) attempted PTJV via a 14-gauge Angiocath attached to a hand-held jet ventilator, f of 20/min, and ET IPPV using an Ambu bag, f of 10/min. Twenty-nine other EMTs attempted cricothyrotomy using a prototype nonkinkable catheter (Arrow) and a new jet ventilator, Bronchovent, f of 60/min, equipped with a pressure sensor which stops ventilation at pressures greater than 20 cm H2O. Adequate oxygenation was achieved by all 3 groups, but only the HFPPV group avoided respiratory alkalosis. There was a higher equipment failure rate (catheter kinking and dislodgment) in the PTJV group. In the HFPPV group, the Bronchovent's pressure-limiting sensor stopped ventilation when the catheter was kinked or out of position, reducing the extent of subcutaneous emphysema and barotrauma. With further catheter improvements, HFPPV Bronchovent may offer a safe and reliable method of ventilating patients during CPR in the field.

Alkalosis, Respiratory↗
PubMed1984

Continuous flow apneic ventilation.

A study was designed to evaluate the adequacy of gas exchange during continuous flow apneic ventilation (CFAV) in dogs. Seventeen dogs (average weight 22.9 kg) were divided into three experimental groups. Group I (n = 7) was anesthetized, paralyzed and ventilated with air using intermittent positive pressure ventilation (IPPV) through a tracheal tube. The tube was removed and each main stem bronchus was cannulated with a 2.5 mm i.d., 4 mm o.d. polyethylene catheter using a fiberoptic bronchoscope. The tracheal tube was replaced to hold the catheters in place. Heated, humidified air was continuously delivered equally to each catheter. Total flows ranged from 8 to 28 l/min (0.4-1.4 l X kg-1 X min-1). Airway pressure (Paw) in the trachea did not exceed 2 mmHg (0.27 kPa). Adequate gas exchange in terms of arterial oxygen and arterial carbon dioxide tension (Pao2 and Paco2) was found after 30 min at flows greater than 16 l X min-1. Group II (n = 7) was managed similarly to the first group, insufflating endobronchial air using the optimal flow of 1.0 l X kg-1 X min-1 obtained from Group I. CFAV continued for 5 h in all animals. Blood gas samples and measurements of systemic blood pressure, heart rate (HR), pulmonary artery blood pressure, pulmonary artery wedge pressure, cardiac output (Qt), and temperature were taken every 30 min. Group III (n = 3) was anesthetized similarly to the other groups. Pulmonary gas distribution was evaluated in relation to catheter placement using Xe133. Results showed significant differences between Pao2 values during CFAV and IPPV; however, all animals were adequately oxygenated.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗