Biomedical subjects
U Borg
Publications and source records attributed to U Borg.
Randomized clinical trial of pressure-controlled inverse ration ventilation and extra corporeal CO2 removal for ARDS.
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Survival after 67 days of continuous hemodiafiltration in a patient with multiple system organ failure.
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Efficacy of continuous arteriovenous hemofiltration with dialysis in patients with renal failure.
OBJECTIVE: To document the efficacy of continuous arteriovenous hemofiltration with dialysis following renal failure, without protein restriction, and to explore the magnitude and clinical applications of total daily urea clearance. DESIGN: A noncomparative, descriptive account of a case series. Data were collected prospectively and analyzed retrospectively. SETTING: A tertiary care facility in a statewide emergency medical services system. PATIENTS: Twenty-eight patients with renal failure were supported by continuous arteriovenous hemofiltration with dialysis in a critical care unit during a 14-month period (21 patients with multitrauma; three patients with soft tissue infections; and four patients with multisystem organ failure who had been transferred from other hospitals). Renal failure was most commonly due to multisystem organ failure or associated with adult respiratory distress syndrome. RESULTS: Continuous arteriovenous hemofiltration with dialysis days totaled 308 (mean 10.9). All patients received full protein alimentation (mean protein load 131 g/day). The blood urea nitrogen concentration was controlled, generally to 40 to 75 mg/dL (14.3 to 26.7 mmol/L) within 3 to 5 days. Total daily urea clearance ranged from 15 to 21 g/day. Five (18%) of the 28 patients survived. CONCLUSION: Continuous arteriovenous hemofiltration with dialysis appears to be effective for the control of blood urea nitrogen and clearance of urea. This modality also permits full protein alimentation. Total daily urea clearance can be calculated easily and may have important clinical uses and implications.
Efficacy of pressure support ventilation dependent on extravascular lung water.
Continuous positive-pressure ventilation and PSV were compared prospectively in patients at a surgical intensive care unit. All patients suffered from mild to moderate ARI (PaO2/FIO2 of 125 to 350 mm Hg). The patients were randomly assigned to a PSV group (n = 28) or a control group with continued CPPV (n = 27). The usual hemodynamic and oxygenation variables, ITBV, and extravascular lung water (ETV) were assessed before and six hours after switching to PSV. The changes (d) of PaO2/FIO2, RI, and P(A-a)O2 were used for evaluation of the effect of PSV. Significant correlations were found between the ETV(CPPV) and dPaO2/FIO2 (r = -0.672), ETV(CPPV) and dRI (r = 0.722), and ETV(CPPV) and dP(A-a)O2 (r = 0.601), which led to the conclusion that the level of ETV determined the efficacy of PSV. In the subgroup with ETV less than 11 ml/kg (n = 15), PSV significantly improved PaO2/FIO2 (248 to 286 mm Hg), RI (1.55 to 1.22), ITBV (801 to 888 ml/m2), cardiac index (4.21 to 4.76 L/min.m2), stroke index (42.2 to 48.1 ml/m2), and oxygen delivery (735 to 833 ml/min.m2). In the subgroup with ETV greater than 11 ml/kg (n = 13), PSV caused a significant deterioration of PaO2/FIO2, RI, and intrapulmonary shunt. It is concluded that in patients with moderate ARI in whom ETV is almost normal, PSV is superior to CPPV, and the efficacy of PSV is independent of the level of oxygenation during CPPV.
MR imaging of ventilator-dependent patients: preliminary experience.
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Quantification of asymmetric lung pathophysiology as a guide to the use of simultaneous independent lung ventilation in posttraumatic and septic adult respiratory distress syndrome.
The management of impaired respiratory gas exchange in patients with nonuniform posttraumatic and septic adult respiratory distress syndrome (ARDS) contains its own therapeutic paradox, since the need for volume-controlled ventilation and PEEP in the lung with the most reduced compliance increases pulmonary barotrauma to the better lung. A computer-based system has been developed by which respiratory pressure-flow-volume relations and gas exchange characteristics can be obtained and respiratory dynamic and static compliance curves computed and displayed for each lung, as a means of evaluating the effectiveness of ventilation therapy in ARDS. Using these techniques, eight patients with asymmetrical posttraumatic or septic ARDS, or both, have been managed using simultaneous independent lung ventilation (SILV). The computer assessment technique allows quantification of the nonuniform ARDS pattern between the two lungs. This enabled SILV to be utilized using two synchronized servo-ventilators at different pressure-flow-volumes, inspiratory/expiratory ratios, and PEEP settings to optimize the ventilatory volumes and gas exchange of each lung, without inducing excess barotrauma in the better lung. In the patients with nonuniform ARDS, conventional ventilation was not effective in reducing shunt (QS/QT) or in permitting a lower FIO2 to be used for maintenance of an acceptable PaO2. SILV reduced per cent v-a shunt and permitted a higher PaO2 at lower FIO2. Also, there was x-ray evidence of ARDS improvement in the poorer lung. While the ultimate outcome was largely dependent on the patient's injury and the adequacy of the septic host defense, by utilizing the SILV technique to match the quantitative aspects of respiratory dysfunction in each lung at specific times in the clinical course, it was possible to optimize gas exchange, to reduce barotrauma, and often to reverse apparently fixed ARDS changes. In some instances, this type of physiologically directed ventilatory therapy appeared to contribute to a successful recovery.
Computer-based evaluation of cardiopulmonary function for the optimization of ventilatory therapy in the adult respiratory distress syndrome.
A computer based evaluation system has been developed for the assessment of respiratory pressure flow dynamics, pulmonary gas exchange and ventilation perfusion interrelationships. This system is based on the acquisition of primary data on-line from intubated and ventilated patients consisting of airway pressures, ventilatory flows and mass spectrometric quantification of inspired and expired gas concentrations. The system has been applied to the study of patients with the adult respiratory distress syndrome (ARDS) following trauma and/or sepsis. The programs developed for evaluation of these data permit an interactive graphic capability to be used by the physician or the respiratory technician in a specific patient to determine the nature of the abnormalities in respiratory function. By use of this system for quantification of the extent and complications of the ARDS condition the specific ventilatory or cardiodynamic therapy can be tailored to meet the patient's physiologic needs. Techniques for optimization of conventional ventilator therapy are described and its application to the specific instances of combined high frequency ventilation or differential lung ventilation are presented. The clinical experience with this unit in a major trauma center suggests that quantitative analysis of an individual patients' respiratory dysfunction permits a precise, accurate and more effective approach to determining corrective therapy in ARDS.
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.
A simple flueric high frequency jet ventilator.
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Experimental studies of continuous positive-pressure ventilation and high-frequency positive-pressure ventilation.
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High-frequency positive-pressure ventilation (HFPPV): a review based upon its use during bronchoscopy and for laryngoscopy and microlaryngeal surgery under general anesthesia.
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A preliminary report on experimental studies of continuous positive-pressure ventilation (CPPV) and high-frequency positive-pressure ventilation (HFPPV).
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Physiologic evaluation of the HFPPV pneumatic valve principle and PEEP. An experimental study.
In experiments in dogs the ventilatory and circulatory conditions prevailing with the ventilatory pattern in high-frequency positive-pressure ventilation (HFPPV) were investigated with use of a pneumatic valve principle and a ventilator system of an "open" character. Keeping the gas input constant the importance of insufflation frequency and insufflation time and the reactions to various levels of positive end-expiratory pressure (PEEP) were investigated in terms of changes in arterial pH, Pco2 and Po2. With the volumes of delivered gas kept constant, an increasing insufflation frequency from 60 to 100 per min gave a parallel decrease in tidal volume accompanied by lower maximum intratracheal pressures and a significant decrease in alveolar ventilation. Also taking into account the possibilities of inducing a suppression of the spontaneous respiration, higher ventilatory frequencies than 60 per min do now seem to introduce any further advantages. Including the associated effects on cardiac output and venous admixture, the cardio-pulmonary and circulatory parameters studied did not show any substantial changes with PEEP levels below 7.5--10 cm H2O. Thus the level of PEEP, which often is part of the ventilatory pattern in HFPPV, does not seem to have any untoward influence on the circulation (stroke volume, cardiac output, total peripheral vascular resistance) and oxygen transport (arterial oxygen content and oxygen flux) in normovolaemic dogs.
High-frequency positive-pressure ventilation (HFPPV) applied in bronchoscopy under general anaesthesia. An experimental study.
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Full protein alimentation and nitrogen equilibrium in a renal failure patient treated with continuous hemodiafiltration: a case report of 67 days of continuous hemodiafiltration.
Standard care for patients with renal failure while in an intensive care unit involves traditional hemodialysis or peritoneal dialysis and protein restriction. We present a case of a patient with renal failure supported with continuous arteriovenous hemofiltration with dialysis (CAVH-D) who was given full protein alimentation. Total daily urea clearance was measured from the CAVH-D output. Protein load was 196 +/- 34 g/day while receiving total parenteral nutrition and 164 +/- 30 g/day while receiving enteral alimentation. Serum blood urea nitrogen was controlled between 40 and 75 mg/dL, except during septic episodes. Nitrogen balance was estimated based upon known alimentation protein load and measurable and estimated nitrogenous losses. The patient was potentially in nitrogen equilibrium during most of the dialysis period. The cumulative nitrogen balance was positive by 5.2 g after 67 days of dialysis. Volume of alimentation was 3.49 +/- 0.7 liters/day. With CAVH-D, the renal failure patient can receive full alimentation without volume or protein load limitations. Furthermore, nitrogen balances can be estimated easily while the patient is on CAVH-D.