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Biomedical subjects

J V Snyder

Publications and source records attributed to J V Snyder.

At least 37 records · Page 2Linked to original sources
PubMed1986

Hospital guidelines for deciding about life-sustaining treatment: dealing with health "limbo".

The decision to withhold life-sustaining treatment from hopelessly ill patients is fraught with ethical dilemmas and legal uncertainties. Although there are extensive published commentaries on the subject and the law is gradually becoming clearer, care-givers often need concrete guidance when confronted with actual cases. Hospital ethics committees can assist care-givers, patients, and families in resolving these dilemmas, but the committees also need some specific guidance to be relatively consistent. Therefore, the Ethics and Human Rights Committee of Presbyterian-University Hospital, one of the University Health Center Hospitals in Pittsburgh, has developed guidelines for deciding about life-sustaining treatment.

Decision Theory↗
PubMed1985

LV filling pressure during PEEP measured by nadir wedge pressure after airway disconnection.

Pulmonary arterial occlusion pressure (Ppao) may not accurately reflect left ventricular filling pressure (LVFP) during ventilation with positive end-expiratory pressure (PEEP) because increases in pleural pressure (Ppl) increase measured intrathoracic vascular and cardiac chamber pressures relative to atmospheric while decreasing LVFP by decreasing venous return. Steady-state values of Ppao off PEEP are not useful in understanding the hemodynamics on PEEP because of changes in blood volume distribution and ventricular afterload associated with the removal of PEEP. We hypothesized that changes in Ppao immediately after abrupt airway disconnection from PEEP selectively reflect removal of PEEP-associated Ppl changes prior to other physiological changes. In pentobarbital-anesthetized closed-chest dogs, we compared absolute left atrial pressure and left atrial pressure relative to Ppl (Platm) prior to abrupt disconnection from 15 cmH2O PEEP (on-PEEP), with Ppao at its nadir (nadir Ppao) following airway disconnection in three sequential conditions: control (normal), after propranolol-induced acute ventricular failure, and after oleic acid-induced lung injury. For all conditions at low LVFP (less than 9 Torr), nadir Ppao reflects Platm better than on-PEEP Ppao, while at higher LVFP (greater than 9 Torr), on-PEEP Ppao better reflects Platm than nadir Ppao (P less than 0.05). Accurate predictions of on-PEEP Platm can be made using both on-PEEP and nadir Ppao values in a multiple regression equation.

Animals↗
PubMed1985

Subjective and objective measurement of tidal volume in critically ill patients.

Subjective assessment of the respiratory rate and the adequacy of tidal ventilation are the oldest and most widely practiced forms of respiratory monitoring in critically ill patients. Surprisingly, this method of assessment has itself never been evaluated in patients. The estimation of tidal volume in nine patients was performed by full-time intensive care unit (ICU) personnel and compared to the objective measurement of using a calibrated and validated respiratory inductive plethysmograph (RIP). Linear correlation analysis was performed. Poor correlation between clinical estimation by ICU personnel and actual measurement by RIP was revealed in all cases. A widespread and potentially dangerous tendency to overestimate tidal volume was noted. These data suggest that subjective assessment of tidal volume is inaccurate in critically ill patients and that the development of techniques of continuous, nonobtrusive and objective monitoring are to be encouraged.

Acute Disease↗
PubMed1985

Barotrauma and hypotension resulting from jet ventilation in critically ill patients.

We present the first reports of pneumoperitoneum secondary to jet ventilation, barotrauma secondary to jet ventilation through the suction port of a fiberoptic laryngoscope, and hypotension due to jet ventilation via nasotracheal and orotracheal catheters. We suggest that minimizing airway pressure and using jet catheters with side holes may help decrease the risk of such complications. We cannot, at present, recommend the use of hand-held jet ventilators unless both adequate exhalation space is guaranteed and direct impingement of the catheter's tip on the mucosal surface is avoided.

Aged↗
PubMed1985

Directed manual recruitment of collapsed lung in intubated and nonintubated patients.

Four patients with collapsed lung are presented that demonstrate the utility of the directed manual recruitment technique (DMRT) in a range of clinical situations presented by weaning difficulties, recurrent acute atelectasis, and acute respiratory failure in the nonintubated patient. DMRT is an easily applied noninvasive method of lung expansion in the treatment of patients with segmental and lobar collapse and is safe when carried out with appropriate precautions.

Adult↗
PubMed1984

Local lung ventilation in critically ill patients using nonradioactive xenon-enhanced transmission computed tomography.

Nonradioactive xenon is sufficiently radiodense to increase the density of gas-containing lung as seen in a computed tomography (CT) scan. Subtraction of a baseline CT scan from the xenon-enhanced CT scan can accentuate gas space differences by subtracting fixed tissue densities. The baseline scan and the scan obtained during wash-in of xenon (before equilibration) allow circulation of local ventilation. The xenon CT scan, thus, provides more precise information about distribution of ventilation than planar radiogas techniques. The technical aspects of application to a critically ill patient and the mathematical basis of the technique are presented.

Humans↗
PubMed1984

Cheyne-Stokes respiration revisited: controversies and implications.

Investigation of the periodic crescendo-decrescendo alterations in tidal volume in Cheyne-Stokes respiration (CSR) has provided remarkable insight into the physiology of respiratory control. Many patients with periodic breathing have both cardiac and neurologic disease. Considerable controversy has surrounded determination of the relative importance of cardiac and neurologic mechanisms in the genesis of this breathing abnormality. Several investigators have considered the respiratory center as a chemostat model with three basic components: the controller system (chemoreceptors), the controlled system (gas tensions of O2 and CO2), and the feedback loop (arterial circulation from the lung to the brain). If the relationship between these cardiac and neurologic components is altered, stability of the respiratory control system is lost. Such disturbance in the control system may arise by prolongation of the circulation time, or by the system becoming more dependent on its O2, rather than the CO2 component. Earlier investigators considered periodic breathing as a forewarning of ominous developments. In recent studies, mild degrees of periodic breathing, easily missed on physical examination, are often found in otherwise normal subjects, particularly during sleep. Generally no therapy is required, although aminophylline, O2 or CO2 administration has been shown to abolish periodic breathing.

Aged↗
PubMed1984

Local cerebral blood flow alterations (Xe-CT method) in an accident victim.

Computed tomography was used before and during inhalation of nonradioactive xenon gas to measure and map local cerebral blood flow noninvasively at two PaCO2 levels in a 19-year-old accident victim. The technique demonstrated normal response to elevated PaCO2 with only a regional loss of autoregulation.

Adult↗
PubMed1983

Effect of bacteremia and fluid resuscitation on cardiac output.

The cardiac output acutely inducible by a 1-ml/kg/min saline infusion was observed in 12 septic and 7 nonseptic cynomolgus monkeys. In septic monkeys intravenous live E. coli were titrated to rapidly produce equivalent hypotension which was maintained for 1 hr before saline. Bacteria dose range was 1.3 X 10(11) bacteria/kg-400 X 10(11) bacteria/kg. There was no significant correlation between the dose of bacteria and the cardiac output nadir; however, the subsequent maximum cardiac output during saline resuscitation was significantly negatively correlated with the bacterial dose. In conclusion, widely varying amounts of intravenous bacteria can produce the same degree of hypotension and not correlate with cardiac output. In contrast, cardiac output measured early during subsequent saline resuscitation better predicts the severity of bacteremia.

Animals↗
PubMed1982

Evaluating outcome from intensive care: a preliminary multihospital comparison.

To contrast mortality for groups of ICU patients treated in different hospitals, we surveyed 795 consecutive ICU admissions in 5 ICUs using a general severity of illness classification system. After obtaining information from the medical record on age, sex, indication for ICU admission, and severity of illness, we used a logistic multiple regression equation to project death rates for each ICU based on data from a sixth reference hospital. There were substantial differences in severity of acute illness among the hospitals which accounted for most of the variation in death rates. In all ICUs, however, projected death rates were quite similar to observed deaths. These findings suggest that the use of a general severity of illness index and multivariate statistical techniques could, after further refinement and validation, improve interhospital comparisons of the outcome of acutely ill patients.

Critical Care↗
PubMed1982

Comparison of high frequency jet ventilation to conventional ventilation during severe acute respiratory failure in humans.

High frequency jet ventilation (HFJV) was compared to conventional (high tidal volume, low frequency) ventilation in 9 patients with acute respiratory failure (ARF). Alveolar ventilation was comparable or lower with HFJV in all but one case. When comparisons were made at the same concentration of oxygen and level of PEEP, no consistent change in arterial oxygenation (PaO2) was found. In one case, it was possible to increase PaO2 during HFJV by additional increases in PEEP without elevation in peak airway pressure (AWP) compared to conventional ventilation (CV). At the same level of PEEP, peak AWP was lower during HFJV, except in 1 patient with bronchospasm. Cardiac output did not differ significantly between the 2 ventilation systems, except in the same patient with bronchospasm. HFJV may be useful in acute respiratory failure when peak AWP during CV limits effective use of mechanical ventilation for gas exchange. Patients with significantly elevated airway resistance may be an exception. Improvement in PaO2 will usually depend on increases in PEEP.

Acute Disease↗