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Biomedical subjects

R E Dutton

Publications and source records attributed to R E Dutton.

At least 37 records · Page 2Linked to original sources
PubMed1979

Ventilation-perfusion imbalance after head trauma.

To investigate the role of ventilation-perfusion (VA/Q) imbalance in the hypoxemia observed after head injury, 5 male subjects (17 to 26 years of age) with isolated head trauma and subsequent hypoxemia were studied. Disturbances of ventilation and perfusion were assessed using the steady-state elimination of six inert gases of different solubilities. Paired studies were conducted during mechanical ventilation with a volume-cycled ventilator and during spontaneous ventilation. Distributions recovered from studies of spontaneous ventilation show a mode of ventilation and perfusion near a VA/Q of 1.0. In addition, 41% of the cardiac output was distributed to a second population of lung units with low VA/Q (less than 0.1) and shunt. During mechanical ventilation, perfusion to these regions of low VA/Q decreased to 21% of the cardiac output, whereas shunt fraction was unchanged. This was associated with a marked broadening of the VA/Q mode near 1.0, relative to the studies during spontaneous ventilation. Mean functional residual capacity during mechanical ventilation was not different from that during spontaneous ventilation. These results suggest that head injury can lead to hypoxemia through a failure of VA/Q regulatory mechanisms.

Adolescent↗
PubMed1979

Evaluation of glucocorticoids during resuscitation of injured patients.

This study evaluates the effects of 30 mg/kg methylprednisolone (MP) administered to eight trauma patient over a 30-minute period during initial resuscitation. Vascular pressures, cardiac index (CI), left ventricular stroke work index (LVSWI), systemic (SVR) and pulmonary (PVR) vascular resistance, oxygen delivery (OD), oxygen consumption (VO2), physiological shunt (shunt), limb blood flow (LBF), limb-oxygen delivery (LOD), and limb oxygen consumption (VLO2) were calculated at control and 1, 2, 4 and 6 hours following MP administration. At 1 hour there was an increase in CI from 2.9 +/- 0.3 to 3.5 +/- 0.3 liters/min/m2 (P less than 0.01), in OD from 961 +/- 172 to 11067 +/- 148 ml/min (P less than 0.05), in VO2 from 178 +/- 16 to 220 +/- 16 ml/min (P less than 0.01), in shunt from 25 +/- 3% to 33 +/- 3% (P less than 0.05), and a decrease in SVR from 1187 +/- 98 to 1945 +/- 87, and in PVR form 222 +/- 22 to 178 +/- 18 dyne sec/cm5 (P less than 0.05). These values returned to control by 4 hours. In spite of a pulmonary wedge pressure (PWP) that did not increase form a control of 5 +/- 2 mm Hg, and a mean arterial blood pressure (MABP) that did not decrease from a control of 86 +/- 5 mm Hg, LVSWI increased significantly at 1 hour (P less than 0.01). LBF, LOD, and VLO2 decreased at 1 hour (P less than 0.05). Since increased cardiac output was associated with increased stroke volume and left ventricular stroke work index, but without an increase in preload (PWP) or a decrease in afterload (MABP), methylprednisolone(MP), in pharmacologic dosage appears to have a positive inotropic effect on the myocardium of trauma patients during resuscitation.

Adult↗
PubMed1978

Effect of chemoreceptor denervation on the pulmonary vascular response to atelectasis.

Six dogs anesthetized with 30 mg/kg pentobarbital were ventilated after differential cannulation of the main stem bronchi. Following sternotomy, blood flow was monitored by electromagnetic flow probes on the left pulmonary artery (QL) and on the pulmonary trunk or aorta (QT). Following 10 min of bilateral 100% O2, QL was 37.4 +/- 5.8% of QT. When left lung atelectasis was induced while the right lung remained on 100% O2, PaO2 remained above 75 mm Hg and QL fell to 26.1 +/- 5.0% of QT. However, when the right lung was ventilated with room air while the left lung remained atelectatic, PaO2 fell to 50.0 +/- 2.6 mm Hg and QL rose to 36.7 +/- 6.2% of QT. Six dogs which had undergone peripheral chemoreceptor denervation prior to these experiments showed a similar decrease in perfusion of the atelectatic left lung when the right lung was ventilated with 100% O2, but did not increase blood flow to the atelectatic lung during systemic hypoxemia. Thus, the increased blood flow to the atelectatic lung which occurs during systemic hypoxemia appears to be mediated by the arterial chemoreceptors.

Animals↗
PubMed1978

Hypoxia, hyperammonemia, and cerebrospinal fluid metabolites.

During hemorrhagic shock, increased uptake of NH3 from the gut with inadequate compensation by the liver results in hyperammonemia. The effect on brain metabolism of acute hyperammonemia alone, as compared with normocapnic hypoxia, was investigated in 11 pentobarbital anesthetized (30 mg/kg) dogs. These animals were paralyzed (pancuronium bromide) and artificially ventilated to maintain the end-tidal fraction of FETCO2) CO2 constant. Arterial blood and cerebrospinal fluid (CSF) samples were obtained following control, 30-minute hypoxia, 60-minute NH3 infusion, and 30-minute hypoxia combined with NH3 infusion. These were analyzed for PaO2, PCO2, pH, and NH3. CSF samples were further analyzed for glutamine, urea, lactate, pyruvate, and citrate. There were no significant changes in urea or citrate. Glutamine, lactate, and the lactate/pyruvate ratio were significantly elevated by hypoxia and by NH3 infusion. (formula: see text). Thus, an acute NH3 load is capable of disrupting aerobic glycolytic metabolism. Hence, hyperammonemia may affect brain function during shock.

Ammonia↗
PubMed1977

Cardiac output and pulmonary wedge pressure. Use for evaluation of fluid replacement in trauma patients.

Cardiac output and pulmonary wedge pressure (PWP) were used to evaluate the end point of fluid resuscitation in 20 patients suffering from multiple trauma and shock. Eleven patients received crystalloid resuscitation and nine patients received colloid resuscitation. Fifteen of 20 patients had an adequate cardiac output at the termination of resuscitation, but but only six of these patients had a PWP above 10 mm Hg. There was no significant correlation between left ventricular stroke work index and PWP in these patients, either at the completion of resuscitation or during the following three days. Five patients did not achieve adequate cardiac output and four of these patients died, suggesting that cardiac output was the most important criterion for adequate resuscitation. If the goal of fluid resuscitation is to achieve an adequate cardiac output, then PWP was not a reliable guide. Furthermore, using both cardiac output and PWP as a guide to fluid resuscitation of our patients, we found that the type of fluid (crystalloid or colloid) for resuscitation did not influence the course of respiratory distress in these patients up to three days following resuscitation.

Adult↗
PubMed1977

Chemoreceptor influence on pulmonary blood flow during unilateral hypoxia in dogs.

Dogs anesthetized with 30 mg/kg pentobarbital were artificially respired after differential cannulation of the main stem bronchi. Following median sternotomy, blood flow was monitored by electromagnetic flow probes on the left pulmonary artery (QL) and on the pulmonary trunk or aorta, QT. Following 10 min of bilateral 100% O2, QL was 42.5 +/- 7% of QT. When 6% O2, was substituted as the gas mixture inspired by the left lung while the right lung remained on 100% O2, PaO2 was above 70 mm Hg and QL fell to 24.5 +/- 5% of QT. Room air was then used to ventilate the right lung while the left lung remained on 6% O2. This caused PaO2 to fall to 42.3 +/- 3 MM Hg and QL to rise to 38.3 +/- 6% QT. This increase in blood flow to the unilaterally hypoxic lung during systemic hypoxemia did not occur in dogs after peripheral chemoreceptor denervation. Therefore, interference with the local response to alveolar hypoxia during systemic hypoxemia appears to be mediated by the arterial chemoreceptors.

Animals↗
PubMed1977

Uneven ventilation of the lung following trauma.

Ventilatory function of the lungs has been studied in 13 post-trauma patients using a two compartment analysis. The analysis is based upon a model of the lung which describes a nitrogen washout curve in terms of fast and slowly ventilated compartments. Data output from a digital computer provides values that compare the fractions of the alveolar ventilation and volume of the two compartments. All patients on initial investigation had large identifiable slow spaces. Subsequent evaluation at a time of clinical improvement showed that the ventilation of the slow space had increased significantly (P less than .003), whereas no change was evident in the volume fraction. The ventilation to volume ratio of the slow space, measured on these two separate occasions increased in twelve of the patients studied. An increase in this ratio correlated with improvement in the patient's clinical condition.

Adolescent↗
PubMed1977

Pulmonary wedge catheterization during positive end-expiratory pressure ventilation in the dog.

In ten supine anesthetized dogs, recordings of left atrial (LA) and pulmonary-artery wedge (PW) pressures were simultaneously obtained at several levels of positive end-expiratory pressure (PEEP) ventilation with the thorax either open or closed. Lateral roentgenograms were taken to determine the relative vertical positions of the LA and PW catheter tips. When the wedge catheter tip was vertically above the left artrial catheter tip, mean PW followed airway pressure at PEEP of more that 5 cm H20. For PEEP 5 cm H20 or less, and for PW catheter tip positions vertically below the LA catheter tip at all levels of PEEP, mean wedge catheter pressure was close to left atrial pressure. Thus, it appears the LA pressure can best be estimated by PW catheter positions vertically below the left atrium during positive end-expiratory pressure ventilation.

Animals↗
PubMed1977

Continuous positive airway pressure versus positive end-expiratory pressure in respiratory distress syndrome.

The hemodynamic and respiratory effects of spontaneous ventilation with continuous positive airway pressure (CPAP) and mechanical ventilation with positive end-expiratory pressure (PEEP) were compared in nine patients who had adult respiratory distress syndrome. These patients were capable of maintaining spontaneous ventilation (tidal volume above 300 ml. and PaCO2 below 45 torr). Arterial and mixed venous blood gases, cardiac output, oxygen delivery and consumption, pulmonary artery pressure, and pulmonary wedge pressure were measured in 11 instances, with each patient on 5 or 10 cm. H2O CPAP or PEEP, and in nine instances, with each patient on the ventilator but without PEEP (O PEEP). During CPAP, when compared to PEEP at the same level of end-expiratory pressure, mean PaO2 increased significantly (p less than 0.05) and mean physiological shunt decreased (p less than 0.05). In nine of 11 instances, cardiac output was higher on CPAP than on a corresponding level of PEEP. Thus CPAP was more effective than the same amount of PEEP in improving arterial oxygenation by the lung without adversely affecting cardiac output.

Adolescent↗
PubMed1976

Phasic reflux of pulmonary blood flow in atelectasis: influence of systemic PO2.

In 16 dogs ventilated with 100% O2, control blood flow to the left lung was 35 +/- 2% of aortic flow. When left lung atelectasis was induced, left pulmonary artery flow fell to 19 +/- 2% of aortic flow. A large retrograde component of flow developed in this pulmonary artery, suggesting that blood flows into the pulmonary arteries of both lungs during systole, but flows back out of the collapsed lung and into the uncollapsed lung during diastole. Systemic PaO2 remained above 78 mmHg. Subsequently, when the ventilation of the right lung was changed from oxygen to room air, systemic PaO2 fell to 64 +/- 3 mmHg and atelectatic left lung flow rose from 19 +/- 2% to 28 +/- 2% f aortic flow. This was associated with a reduction in reflux from the atelectatic lung. These results suggest that the attenuation of flow to an atelectatic lung is more pronounced if systemic normoxemia is maintained by adequate oxygenation of the normal lung.

Animals↗