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Biomedical subjects

R Pizov

Publications and source records attributed to R Pizov.

At least 37 records · Page 2Linked to original sources
PubMed1998

Helium versus oxygen for tracheal gas insufflation during mechanical ventilation.

OBJECTIVE: To evaluate and compare the effect of tracheal gas insufflation using two gases with different physical properties, helium and oxygen, as an adjunct to conventional mechanical ventilation in patients with respiratory failure. DESIGN: Prospective, intervention study. SETTING: General intensive care unit in a tertiary university medical center. PATIENTS: Seven sedated and paralyzed patients with respiratory failure of various etiologies. All patients were ventilated in the volume-control mode (tidal volume 5 to 7 mL/kg). Inclusion criteria were PaCO2 of > or =50 torr (> or =6.7 kPa), together with peak inspiratory pressure of > or =35 cm H2O and respiratory rate of > or =14 breaths/min. INTERVENTIONS: All patients were intubated with an endotracheal tube that had an additional lumen opening at its distal end, through which tracheal gas insufflation was administered. The tracheal gas insufflation was applied continuously throughout the respiratory cycle at three flow rates (2, 4, and 6 L/min) with two gases, oxygen and helium, while the ventilatory settings were maintained constant. MEASUREMENTS AND MAIN RESULTS: In addition to airway pressures and arterial blood gases, the relative efficacy of tracheal gas insufflation with each gas was estimated using a "coefficient of efficiency" (which we defined as the change in PaCO2/peak inspiratory pressure) compared with baseline measurements. Tracheal gas insufflation with both gases decreased PaCO2 significantly (p < .05) at all flow rates. This effect was accompanied by an increase in airway pressure with both gases (oxygen and helium). However, at flow rates of 6 L/min, tracheal gas insufflation with helium resulted in lower peak inspiratory pressure than with oxygen. Tracheal gas insufflation with helium was more effective (as estimated by the coefficient of efficiency) than with oxygen at all flow rates (p < .05). CONCLUSION: In volume-controlled, mechanically ventilated patients with respiratory failure, tracheal gas insufflation with helium might be suggested as an alternative to oxygen.

Acute Disease↗
PubMed1998

Evaluation of Institutional Review Board review and informed consent in publications of human research in critical care medicine.

OBJECTIVE: To examine the frequency of obtaining Institutional Review Board (IRB) approval and informed consent in critical care research. DATA SOURCES AND DATA EXTRACTION: One-year retrospective review of original critical care research in humans published in seven journals, including American Journal of Respiratory and Critical Care Medicine, Chest, Critical Care Medicine, Intensive Care Medicine, The Journal of the American Medical Association, Lancet, and The New England Journal of Medicine. Studies were examined for general information (country/state where the research was performed, affiliation of the hospital to a medical school, and whether the work was supported by a grant and specifically by a pharmaceutical company), approval by IRB, method of consent, design of research, and interventions involved in the study. DATA SYNTHESIS: Two hundred seventy-nine studies were reviewed, 124 (44%) of which were conducted in the United States. Two hundred forty-three (87%) studies were performed in a university institution, 96 (34%) studies were supported by a grant, and 23 (24%) studies were supported by a pharmaceutical company. In 66 (24%) studies, there was no evidence of IRB review and informed consent approval. IRB approval was obtained but the method of consent was not specified in 36 (13%) studies. No significant differences were found in obtaining IRB approval and informed consent between research conducted in the United States (n=71, 57%) or outside the United States (n=92, 59%). Grant support was obtained in ten (9%) of the 116 studies not fully approved, compared with 70 (50%) of the 140 studies that obtained full approval (p < .05). All studies (23) supported by the pharmaceutical industry were fully approved. CONCLUSIONS: Many published studies in critical care lack IRB approval and/or informed consent. All research supported by the pharmaceutical industry was fully approved. The findings raise ethical concerns about critical care research.

Bibliometrics↗
PubMed1998

Tension pneumoperitoneum after blast injury: dramatic improvement in ventilatory and hemodynamic parameters after surgical decompression.

Tension pneumoperitoneum is a known although rare complication of barotrauma, which can accompany blast injury. We report two patients who suffered from severe pulmonary blast injury, accompanied by tension pneumoperitoneum, and who were severely hypoxemic, hypercarbic, and in shock. After surgical decompression of their pneumoperitoneum, respiratory and hemodynamic functions improved dramatically. Several mechanisms to explain this improvement are suggested. In such cases the release of the tension pneumoperitoneum is mandatory, and laparotomy with delayed closure can be contemplated.

Adult↗
PubMed1997

Influence of alterations in foregoing life-sustaining treatment practices on a clinical sepsis trial. The HA-1A Sepsis Study Group.

OBJECTIVES: To evaluate the timing of foregoing life-sustaining treatments in patients enrolled in a sepsis trial and to determine their influence on patient outcome and trial results. DESIGN: Subset of patients in a prospective, randomized, double-blind, placebo-controlled study. SETTING: Twenty-three academic medical centers. PATIENTS: Enrolled patients who had life-sustaining therapies withheld or withdrawn. MEASUREMENTS AND MAIN RESULTS: The number of patients, types of disorders and interventions, reasons, and timing of withholding and withdrawing life-sustaining treatments and their effect on mortality and trial results were assessed. Foregoing of life-sustaining therapies took place in 117 (22%) of 543 patients and occurred within 72 hrs of study drug administration in 38 (32%) patients. Withholding treatment (60%) was more common than withdrawing treatment (40%), but withdrawing treatment was more frequent (51%) than withholding treatment (20%) in the first 72 hrs of the trial (p < .01). Sixty-one (52%) patients had severe underlying disorders with a poor prognosis. The hospital mortality rate was 94% (of the 117 patients). The mean time (SEM) from withholding or withdrawing of treatment until death was 2.83 +/- 0.57 and 0.32 +/- 0.13 days, respectively (p < .001). Patients who had therapies foregone in the first 24, 48, and 72 hrs after receiving the study drug had higher mortality rates in the first 72 hrs (p < .01). CONCLUSIONS: A substantial number of patients enrolled in a sepsis trial had severe underlying diseases and had foregoing of therapies early in the course of the trial, which led to a higher early mortality rate. Enrollment of patients in clinical trials with severe underlying disorders with a high likelihood of having therapies foregone may bias the potential for showing the efficacy of new therapeutic modalities.

Antibodies, Monoclonal↗
PubMed1997

Positive end-expiratory pressure increases pulmonary venous vascular resistance in patients after coronary artery surgery.

OBJECTIVE: To investigate the effect of positive and-expiratory pressure (PEEP) on the longitudinal distribution of pulmonary vascular resistance in patients immediately after coronary artery bypass grafting. DESIGN: Prospective, intervention study. SETTING: Postcardiac surgery intensive care unit in a teaching institution. PATIENTS: Twenty patients after elective coronary artery bypass grafting. INTERVENTION: The effect of PEEP on pulmonary circulation, at four different levels (0, 5, 10, and 15 cm H2O), was analyzed in 20 patients. MEASUREMENTS AND MAIN RESULTS: Mean pulmonary arterial pressure, left atrial pressure, pulmonary artery occlusion pressure, and pulmonary capillary pressure were measured at each PEEP level. A model consisting of two resistances in series was used to analyze the effect of PEEP on the pulmonary circulation. The pulmonary vascular resistance for each area (arterial and venous) of the circulation was calculated. Pulmonary vascular resistance increased from 216 +/- 70 dyne.sec/cm5 at a PEEP of 0 cm H2O to 308 +/- 125 dyne.sec/cm5 at a PEEP of 15 cm H2O (p < .001). This increase, however, resulted solely from an increase in the resistance of the venous part of the pulmonary circulation from 66 +/- 29 to 134 +/- 69 dyne.sec/cm5 (p < .001), without any change in pulmonary arterial resistance. CONCLUSIONS: PEEP increases pulmonary vascular resistance solely by increasing pulmonary venous resistance. When applying PEEP, changes in pulmonary vascular resistance may impede the resorption of pulmonary edema fluid.

Aged↗
PubMed1997

Alveolar macrophages fat stain in early diagnosis of fat embolism syndrome.

The aim of this study was to assess the contribution of bronchoalveolar lavage (BAL) in the diagnosis of fat embolism syndrome (FES). The presence of fat droplets in alveolar macrophages was addressed in 13 trauma patients with bone fractures and 10 non-trauma patients with acute respiratory distress syndrome (ARDS). The control group was composed of 5 anesthesized patients with ischemic heart disease, immediately prior to cardiac surgery. Two patients with suggestive clinical and laboratory signs of FES had 40% and 24% fat-containing alveolar cells, respectively. The trauma patients without signs of FES displayed a wide variation in the percentage of fat-containing macrophages (from 3% to 95%). Most of the patients with ARDS who were receiving lipid emulsion as part of their parenteral nutrition, had a high percentage (> 85%) of fat-containing macrophages. Patients with normal lungs had no fat-containing macrophages. Our findings suggest that BAL Oil Red O-positive macrophages are frequently observed in trauma patients irrespective of the presence of FES. Therefore, estimation of the percentage of fat-containing macrophages from BAL is an unreliable marker of FES.

Adult↗
PubMed1996

Positive end-expiratory pressure-induced hemodynamic changes are reflected in the arterial pressure waveform.

OBJECTIVE: To examine whether the hemodynamic changes due to mechanical ventilation with positive end-expiratory pressure (PEEP) can be assessed by the respiratory-induced variations in the arterial pressure waveform during normovolemia and experimental acute ventricular failure. DESIGN: Prospective, controlled experimental study. SETTING: Institutional experimental laboratory. SUBJECTS: Adult mongrel dogs. INTERVENTIONS: Experimental acute ventricular failure was induced by the infusion of pentobarbital (a cardiodepressant) and methoxamine (a vasoconstrictor), combined with volume loading. Both the control and acute ventricular failure groups were subjected to ventilation with incremental levels of PEEP up to 20 cm H2O. MEASUREMENTS AND MAIN RESULTS: Cardiac function was evaluated by cardiac output and left and right ventricular change in pressure over time (dP/dt) measurements. Arterial pressure waveform analysis was performed by measuring the systolic pressure variation, which is the difference between the maximal and minimal systolic blood pressure values during one mechanical breath. The components of the systolic pressure variation, namely, dUp and dDown, which are the increase and decrease in the systolic pressure during the mechanical breath relative to the systolic pressure during apnea, were also measured at each PEEP level. PEEP caused significant reduction of cardiac output in normovolemic dogs, and was associated with significant increases in systolic pressure variation and dDown. Acute ventricular failure decreased the variations in the systolic pressure and caused the dDown component to disappear. The application of PEEP did not affect cardiac output in dogs with acute ventricular failure, nor did it change systolic pressure variation and the dDown. CONCLUSIONS: Analysis of arterial pressure waveforms during mechanical ventilation reflected the decrease in cardiac output in dogs with normal cardiac function subjected to incremental PEEP. In dogs with acute ventricular failure in which PEEP did not affect cardiac output, the systolic pressure variation was similarly unaffected by PEEP. In the absence of cardiac output measurement during mechanical ventilation with PEEP, the analysis of the respiratory variations in the arterial pressure waveform may be useful in assessing changes in cardiac output.

Animals↗
PubMed1995

Wheezing during induction of general anesthesia in patients with and without asthma. A randomized, blinded trial.

BACKGROUND: Patients with asthma who require general anesthesia and tracheal intubation are at increased risk for the development of bronchospasm during induction. The incidence of wheezing during induction with different intravenously administered agents is unknown. A randomized, double-blinded prospective study was undertaken to evaluate the incidence of wheezing in asymptomatic asthmatic and nonasthmatic patients receiving three commonly used intravenous anesthetic agents for induction of anesthesia. METHODS: Fifty-nine asymptomatic asthmatic and 96 nonasthmatic patients of ASA physical status 1 and 2 were studied. All patients received 1.5 micrograms/kg fentanyl, oxygen, followed by either 5 mg/kg thiopental or thiamylal, 1.75 mg/kg methohexital or 2.5 mg/kg propofol, 1.5 mg/kg succinylcholine, tracheal intubation, and inhalational anesthesia. Wheezing was assessed by an independent blinded observer, auscultating the lungs at 2 and 5 min postintubation. Data were analyzed by Pearson's chi-squared, Fisher's exact test, and multiple logistic regression with significance set at P < 0.05. RESULTS: Both asthmatic and nonasthmatic patients who received a thiobarbiturate for induction had a greater incidence of wheezing than did patients receiving propofol. In asthmatic patients, 45% (23, 67) (mean and 95% confidence interval) who received a thiobarbiturate, 26% (8, 44) who received an oxybarbiturate, and none (0, 17) who received propofol wheezed after intubation. In nonasthmatic patients, 16% (3, 28) who received thiobarbiturate and 3% (0, 9) who received propofol wheezed. CONCLUSIONS: This study suggests that propofol should be considered for induction of anesthesia in patients, particularly those with asthma, who require timely intubation.

Adolescent↗
PubMed1995

A look into the nature and causes of human errors in the intensive care unit.

OBJECTIVES: The purpose of this study was to investigate the nature and causes of human errors in the intensive care unit (ICU), adopting approaches proposed by human factors engineering. The basic assumption was that errors occur and follow a pattern that can be uncovered. DESIGN: Concurrent incident study. SETTING: Medical-surgical ICU of a university hospital. MEASUREMENTS AND MAIN RESULTS: Two types of data were collected: errors reported by physicians and nurses immediately after an error discovery; and activity profiles based on 24-hr records taken by observers with human engineering experience on a sample of patients. During the 4 months of data collection, a total of 554 human errors were reported by the medical staff. Errors were rated for severity and classified according to the body system and type of medical activity involved. There was an average of 178 activities per patient per day and an estimated number of 1.7 errors per patient per day. For the ICU as a whole, a severe or potentially detrimental error occurred on the average twice a day. Physicians and nurses were about equal contributors to the number of errors, although nurses had many more activities per day. CONCLUSIONS: A significant number of dangerous human errors occur in the ICU. Many of these errors could be attributed to problems of communication between the physicians and nurses. Applying human factor engineering concepts to the study of the weak points of a specific ICU may help to reduce the number of errors. Errors should not be considered as an incurable disease, but rather as preventable phenomena.

Ergonomics↗