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Biomedical subjects

G C Carlon

Publications and source records attributed to G C Carlon.

At least 55 records · Page 3Linked to original sources
PubMed1983

Tidal volume and airway pressure on high frequency jet ventilation.

The principle of jet injector indicates that large tidal volumes may be delivered on high frequency jet ventilation (HFJV) without increasing airway pressure. Fifteen dogs were ventilated on HFJV in 2 separate experiments. In the first one, tidal volume was maintained constant at 10 ml/kg, while PEEP, respiratory rate, and cannula size were changed in 16 different experimental conditions. In the second experiment, driving pressure was progressively increased from 5 to 45 psig, and PEEP, respiratory rate, and injector size were changed in 32 experimental conditions. Mean airway pressure, tidal volume, driving pressure, thoracic aortic mean pressure, and abdominal aortic mean pressure were the variables measured. Tidal volume linearly increased with driving pressure, while airway pressure only increased when tidal volume exceeded 25 ml/kg. Blood pressure was inversely related to mean airway pressure. Tidal volume was twice as high with the 1.62 mm injector, as compared to the 1.06 mm injector, although resistances are 6 times higher with the smaller injector. The difference is related to the higher entrainment, which is observed when jet flow velocity increases, as is the case when the injector cannula is smaller. The experiments confirmed that HFJV follows the physical principles of jet mixing and entrainment.

Animals↗
PubMed1983

High frequency jet ventilation in experimental airway disruption.

Anecdotal observations suggest that high frequency jet ventilation (HFJV) is beneficial in major airway disruption. Quantitative evaluation is, however, unavailable. In 12 healthy mongrel dogs, a tracheal window of increasing size, from 0.5 x 1 cm to 1.5 x 2 cm, was opened. Dogs were supported on volume-cycled ventilation (VCV) and on HFJV, using injector cannulas of 1.06 and 1.62 mm internal diameter. The tracheal window was then closed and an upper lobectomy performed, followed by total pneumonectomy. Arterial blood gases were obtained after 10 min in each experimental condition. VCV could maintain life-supporting blood gases only with the tracheal window of 0.5 x 1 cm. HFJV, delivered with a 1.06-mm injector cannula, was adequate with a tracheal window of 1 x 1 cm, or after a lobectomy. In all experimental conditions, HFJV delivered with a 1.62-mm injector effectively maintained alveolar ventilation and arterial oxygenation. Gas transport on HFJV is based, in part, on the principles of jet mixing and entrainment; increasingly large tidal volumes can be delivered under conditions of low and constant pressure. Air leaks through pathological openings remain constant even when tidal volume is increased, so that alveolar ventilation can be adequately maintained.

Airway Obstruction↗
PubMed1983

Naloxone in septic shock.

Naloxone, 0.3 mg/kg of a 10 mg/ml solution, was administered as a single bolus to patients in septic shock if their systolic blood pressure (BP) was less than 100 mm Hg or MAP less than 70 mm Hg with evidence of renal or cerebral hypoperfusion. Patients with chronic or acute (less than 12 h) administration of narcotics were excluded. Ten patients received naloxone; 5 patients had significant increases in blood pressure; 5 had no response. Maximal response in BP occurred by 15 min, and lasted 45-165 min. Responders could not be separated by nonresponders by analysis of baseline, hemodynamics, or prior steroid therapy; nonresponders were hemodynamically compromised greater than 24 h; responders less than or equal to 8. Two patients in each group were chronically on high-dose steroids and responded to a 2nd smaller dose of naloxone when effects of initial bolus had ended. Naloxone, 0.3 mg/kg, can reverse endorphin-mediated hypotension in acute septic shock in patients who have received chronic steroid therapy.

Adult↗
PubMed1983

High-frequency jet ventilation. A prospective randomized evaluation.

Three hundred nine patients were randomly allocated to two ventilatory protocols; 157 patients were supported with a volume-cycled ventilator (VCV) (Bear Medical BEAR 1) and 152 with a high-frequency jet ventilatory (HFJV) developed at our institution. The two ventilators were compared for safety, reliability, ease of use, and efficacy in maintaining gas exchange. On VCV, end points of therapy were: fractional concentration of oxygen in the inspired gas (FIo2) less than or equal to 0.40; arterial oxygen pressure (PaO2) greater than or equal to 70 mm Hg; cardiac index (CI) greater than or equal to 3.5 L/min/sq m; and spontaneous respiratory rate less than or equal to eight breaths per minute. On HFJV, end points were: FIo2 less than or equal to 0.45; arterial oxygen saturation greater than or equal to 0.90; and CI greater than or equal to 3.5 L/min/sq m. Spontaneous ventilation and pulmonary venous admixture reduction were the goals on VCV, with oxygen transport the goal on HFJV, Total duration of use of the ventilators was approximately 800 days with both types of devices; there were no technical failures, and the incidence of barotrauma was less than 5 percent. The end point of mechanical ventilation was reached by a significantly higher percentage of the patients randomized to HFJV. Patients who failed to reach the therapeutic goal within 24 hours were crossed over to the other form of support. Those crossed from VCV to HFJV improved more rapidly and in greater number than those crossed from HFJV to VCV. When survival and total duration of stay in the intensive care unit were considered, there was no difference between VCV and HFJV. Considering data on gas exchange, VCV provided a higher PaO2 at equivalent positive end-respiratory pressure than HFJV. Alveolar ventilation was slightly better on HFJV. Differences were statistically but not clinically significant. On HFJV, oxygenation and ventilation were maintained with lower peak inspiratory pressures and smaller tidal volumes than those required for VCV. This investigation proves that HFJV is a safe and reliable method to provide mechanical support which does not, at this time, offer obvious benefits over VCV.

Female↗
PubMed1982

High-frequency jet ventilation: theoretical considerations and clinical observations.

High-frequency jet ventilation (HFJV) described a technique of mechanical respiratory support based on the delivery of gases under conditions of constant flow and low pressure. Among the benefits ascribed to HFJV are lessened interference with hemodynamic function and reduced danger of barotrauma. The theoretical and technical aspects of HFJV are discussed and the clinical experience with 39 patients in respiratory failure reported. Synchronization of HFMV with heart rate was attempted in three patients. Cardiac output and ejection fraction increased in all of them. At present, results suggest that HFJV may be the ideal form of support for patients with major airway disruption. The available data also indicated that extensive clinical trials are warranted to define advantages and limits of this form of ventilation.

Bronchial Fistula↗
PubMed1981

Clinical experience with high frequency jet ventilation.

High frequency jet ventilation (HFJV) has been used in recent years in some forms of respiratory failure, where the presence of barotrauma limited the application of high peak inspiratory pressure. In the present report, the authors describe the clinical experience with 17 patients, who could not be supported with conventional mechanical support and were placed on HFJV. Rates of 100 breath/min, inspiratory/expiratory ratio of 1:2 and cannula size of 1.06--1.62 mm (18--14) gauge were used. Driving pressure required to maintain a PaCO2 of 40--45 torr was 14--45 psig; however, except in 2 patients who developed hemorrhagic tracheitis with subtotal obstruction of both mainstem bronchi, a driving pressure higher than 27 psig was never required, even when PEEP up to 32 cm H2O was used. Of 17 patients treated, 8 survived. In all cases, alveolar ventilation could be maintained within the desired range with high frequency ventilation, even in those patients who eventually died; mechanical support never provided better oxygenation or alveolar ventilation than high frequency ventilation. Hemodynamic function was essentially unchanged with high frequency ventilation; indeed, in three cases, inotropic support with dopamine could be discontinued after initiation of high frequency ventilation.

Carbon Dioxide↗
PubMed1981

Technical aspects and clinical implications of high frequency jet ventilation with a solenoid valve.

High frequency jet ventilation (HFJV) is an incompletely studied technique of mechanical respiratory support. The authors have built a ventilator based on a solenoid valve, that allows independent selection of respiratory rate and inspiratory/expiratory ratio. The ventilator can be synchronized to the heart rate. Humidification is provided by warm saline dripped in front of the injector nozzle, so that the jet stream itself acts as a nebulizer. Tube diameter, length, and deformability are fundamental determinants of inspiratory flow rate and wave form. Cannula kinking and inadequate humidification were the most significant sources of complications.

Respiration, Artificial↗
PubMed1981

Comparison of electronic and manometric central venous pressures. Influence of access route.

Manometric central venous pressure (CVP) measurements are still routinely used as indicators of intravascular volume, particularly during surgery and when cardiorespiratory function is assumed to be normal. The difference between manometric measurements of CVP, from a 16-gauge polyvinylchloride catheter, and those obtained electronically from the level of the right atrium through the proximal port of a pulmonary artery catheter was studied in 40 patients admitted to the ICU. Despite correct position of the catheter tips and adequate respiratory oscillations, manometric measurements differed considerably from right atrial mean pressure determinations. The discrepancy was largest and the direction of change not predictable when the CVP catheters was inserted via an antecubital or right subclavian vein. When catheters were inserted from the left subclavian vein or the internal jugular, on the other hand, manometric CVP was consistently 4-6 cm H2O higher than the electronic pressure determination. If a manometric CVP catheter is to be used, the internal jugular or left subclavian routes appear preferable.

Blood Pressure Determination↗
PubMed1981

Dopamine administration in oliguria and oliguric renal failure.

Oliguric renal failure significanlty worsens the prognosis of many critical illnesses, particularly in patients with respiratory failure. In 52 patients, a continuous infusion of dopamine, 1.5-2.5 micrograms/kg . min, was administered when creatine clearance (Ccr) fell below 40 ml/min and urinary output was less than 1 ml/kg . h despite normal intravascular volume. In 18 patients, a continuous infusion of furosemide (3-5 mg/kg . day) was also administered. Daily, two 3-h collections of urine and blood specimens were obtained to determine Ccr, osmolar clearance (Cosm), free water clearance (CH2O) and excreted fraction of filtered sodium (FENa); one collection was made during dopamine infusion and one while the infusion was suspended. Cardiac output and pulmonary venous admixture were also measured. The authors obtained 199 urine collections in 52 patients; considering the aggregate patient pouplation, urinary output increased by 42.3% (30.2 +/- 3.45 (SEM) ml/h), on dopamine infusion. Cosm, FENa, and Ccr were also higher on dopamine. CH2O and hemodynamic variables were not altered by dopamine infusion. When patients were startified on the basis of mechanical ventilatory support, Ccr and furosemide administration, dopamine infusion essentially caused the same changes in the variables studied as described for the aggregate patient population. Diuresis and sodium excretion increased significantly on dopamine even in those patients receiving furosemide infusion. The authors conclude that fluid and osmolar load can be eliminated more effectively in critically ill patients with continuous infusion of 1.5-2.5 micrograms/kg . min of dopamine.

Anuria↗