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Biomedical subjects

D J Powner

Publications and source records attributed to D J Powner.

At least 55 records · Page 3Linked to original sources
PubMed1982

Effects of mechanical ventilation on the measurement of cardiac output by thermodilution.

Phasic variation in cardiac output (CO) of 10-50% during mechanical ventilation was documented in dogs, and in 1 patient by injection of thermal indicator at 1-sec intervals throughout the ventilation cycle. Measured flow variation increased with inflation pressure when other variables were unchanged, and was not influenced to a significant degree by the injection of iced vs room temperature injectate. Such variation can occur in adult patients requiring only minimally increased airway pressure for ventilation. The technique of injecting indicator at a particular moment of the ventilation cycle is not appropriate to monitor absolute or even relative changes in CO because of occasional changes in the phase relation between the ventilation cycle and the flow variation. The mean CO by thermodilution technique is approximately best by the mean of values taken at regularly spaced intervals through the ventilation cycle.

Animals↗
PubMed1981

Ventilatory management of life-threatening bronchopleural fistulae. A summary.

The loss of a substantial portion of a critically ill patient's inspired tidal volume through a bronchopleural fistula (BPF) may significantly alter the intrapulmonary distribution of ventilation, ventilation-perfusion matching and arterial blood gases. If surgical closure of the fistulous tract is not possible, modifications of traditional ventilatory methods may be necessary to preserve adequate gas exchange. The effect of the methods summarized later in this paper upon the patient's mortality and morbidity has not been rigorously analyzed in a large numbers of patients but has been presented in the case studies referenced. Although these techniques might be considered investigational, they can be justified: (1) in the presence of profound hypoxemia and hypercarbia caused by a large BPF, and (2) when reduced gas loss through the fistula is considered an important part of therapy. All the methods discussed below apply in patients requiring endotracheal intubation and mechanical ventilation, whereas some (as indicated in the text) can be used during spontaneous breathing.

Bronchial Fistula↗
PubMed1976

Retroperitoneal air dissection associated with mechanical ventilation.

The radiologic patterns, etiology, and possible consequences of gas dissection into the retroperitoneal space from pulmonary sources are reviewed in three patients requiring mechanical ventilation. Airway disruption appears to be related to peak airway pressures, underlying pulmonary disease, and the patient's hemodynamic condition and may cause different forms of interstitial emphysema and air embolization, which may lead to severe respiratory or circulatory dysfunction. Gas migration to the retroperitoneum and, secondarily, into the peritoneal cavity should be considered in the differential diagnosis of free intra-abdominal gas.

Adolescent↗
PubMedDate not supplied

Differential lung ventilation with PEEP in the treatment of unilateral pneumonia.

A technique for differential lung ventilation via a Carlens tube with inspiratory retardation and the application of separate levels of PEEP to each lung are described in the treatment of a patient with severe unilateral pneumonia. In addition to isolating the diseased lung, this technique permits modification of the distribution of ventilation between the two lungs to improve the ventilation-perfusion ratio and enhance arterial oxygenation. Its clinical application is influenced by the flow characteristics of available mechanical ventilators and by the limitations of the currently available double-lumen endobronchial tubes.

Aged↗
PubMedDate not supplied

Changes in serum catecholamine levels in patients who are brain dead.

Prospective blood samplings from 15 patients admitted with a Glasgow Coma Score of less than 7 were obtained to observe and compare epinephrine, norepinephrine, and dopamine serum levels in patients with brain injury before, after, and in the absence of brain death. Nine of the patients developed or were admitted after brain death. Wide variations in catecholamine blood levels over time were documented, and subgroup analysis precluded useful statistical comparison or inference of the data. The data are presented therefore as descriptive observations only. No apparent differences were noted between similarly injured patients in whom brain death did not develop and patients before brain death or between patients with penetrating versus nonpenetrating brain injury. Brain death was preceded by hypertension and corresponding elevations in serum catecholamine levels in one patient with complete data. Catecholamine levels appeared to fall after brain death in most patients. Only minimal changes in myocardial histology were present in three donor hearts, and the two transplanted hearts functioned satisfactorily. Serum catecholamine measurement or monitoring does not provide a precise method of determining potential injury to the donor heart before or after brain death. Other experimental data and clinical observation indicate that some hearts may be injured in the donor during the evolution of brain death. Pharmacologic intervention may prevent such injury in experimental animals but must be used before brain death is induced. Such interventions should be studied in selected human donors before brain death to determine whether cardiac function is improved in the donor or recipient.

Adult↗
PubMedDate not supplied

In vitro comparison of six commercially available thermodilution cardiac output systems.

Six commercially available thermodilution cardiac output catheter-and-computer systems were evaluated over a variety of simulated clinical conditions using a fixed-output pulsatile-flow pumping unit. Simultaneous testing was performed at pumping rates of 60, 80, and 120 beats per minute and over an output range of 1.57 liters/min to 14.11 liters/min under normothermic, hyperthermic, and hypothermic conditions. Precision within each thermodilution system, as measured by the standard deviation (S.D.) of serial determinations, was acceptable with an overall S.D. range between 0.015 and 0.588 liters/min. When averaged over all experimental situations, the mean percent deviation of five or ten serial measurements was within 10 percent of the known pump output for all systems and maintained a fairly constant relationship above or below the pump output. In this in vitro test, iced injectate did not consistently improve precision or accuracy above that obtained with room-temperature injectate. Features other than performance should also be considered when selecting a particular unit to fulfill a clinical or research need.

Cardiac Output↗