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Biomedical subjects

A I Hyman

Publications and source records attributed to A I Hyman.

At least 37 records · Page 2Linked to original sources
PubMed1983

Amino acids and respiration.

Parenteral nutrition containing glucose and amino acids may stimulate respiration. To ascertain the effects of these solutions on respiration, eight normal subjects received an infusion of 5% dextrose (100 mL/h) for 7 days followed by an infusion of 3.5% amino acids (125 mL/h) for 24 hours. Minute ventilation (VE), tidal volume, mean inspiratory flow (VT/VI), oxygen consumption, and carbon dioxide production were significantly depressed after 7 days of 5% dextrose infusion. Ventilation and metabolic rate increased within 4 hours after initiation of the amino acid infusion and returned to normal 24 hours after the infusion. The effects of the amino acids on (VE) was secondary to an increase in (VT/VI), which is an indicator of neuromuscular ventilatory drive. Thus, within 4 hours amino acids will restore depressed metabolic rate, minute ventilation, and ventilatory drive after prolonged infusion of 5% dextrose.

Adult↗
PubMed1983

Physiologic requirements during rewarming: suppression of the shivering response.

Intraoperative hypothermia has become a common occurrence. Postoperative rewarming often is accompanied by shivering and results in increased metabolic and circulatory demands. We examined the metabolic, hemodynamic, and biochemical variables in 2 groups of hypothermic (greater than 35.8 degrees C) patients requiring mechanical ventilation after a major operation. One was observed during routine medical management whereas the other group received 40 mg of metocurine iodide and then observed during routine medical management. All patients were allowed to rewarm passively. O2 consumption (VO2, ml/min, STPD), CO2 production (VCO2, ml/min, STPD) and respiratory quotient (RQ) measurements were made every 15 min using a Beckman Metabolic Measurement Cart. Esophageal temperature, arterial blood pressure, heart rate (HR), rate pressure product, CVP, arterial blood gases, serum lactate concentration, and duration of shivering also were recorded. Suppression of the shivering by metocurine increased rewarming time significantly and decreased VCO2, VO2, HR, rate pressure product, mean arterial pressure (MAP), and the O2 cost of rewarming. Thus, the elimination of shivering during postoperative rewarming is associated with a decrease in caloric, metabolic demands and myocardial work (as assessed by the rate pressure product) while rewarming time is prolonged. In the postoperative, hypothermic, critically ill patient, suppression of the shivering response in selected patients may be indicated.

Adult↗
PubMed1983

Breathing patterns during curare-induced muscle weakness.

This study examines the pattern of breathing used by normal subjects to compensate for an acute decrease in muscle strength. A continuous infusion of curare was used to reduce peak inspiratory pressure in six normal subjects from normal control levels to -45 cm H2O (moderate weakness) and to -70 cm H2O (mild weakness). Before administration of curare, inspiratory pressure exceeded -120 cm H2O. A canopy-computer-spirometer system was used for noninvasive spirometry and measurements of gas exchange. Partial curarization to a mild level of muscle weakness did not produce significant changes in the respiratory functions studied. With a moderate level of muscle weakness, there were significant increases in tidal volume from 166 to 186 ml/m2 and in inspiratory time from 1.51 to 1.71 sec (P less than 0.05). Minute ventilation and inspiratory flow did not change. However, when given 3% CO2, both normal and partially curarized subjects increased minute ventilation, from 2.3 to 5.7 L/min/m2 and from 2.5 to 6.7 L/min/m2, respectively. The increases in both conditions were secondary to increases in tidal volume. There was also a small increase in respiratory frequency from 15.4 to 18 breaths/min, P less than 0.01 in the partially curarized group given 3% CO2. Because minute ventilation was preserved while vital capacity decreased, it is proposed that respiration is maintained in the presence of muscle weakness associated with curare by diaphragmatic function which remains relatively unaffected by curarization.

Adult↗
PubMed1982

A systematic method for validation of gas exchange measurements.

The measurement of gas exchange is useful, but thus far, has not been practical during the mechanical ventilation of critically ill patients. To validate two new commercial instruments, (Siemens-Elema Servo Ventilator 900B, Beckman Metabolic Cart), the authors constructed a lung model into which they delivered CO2 and N2 at precise rates to simulate Co2 production (Vco2) and O2 consumption (Vos). The model consists of 13.5-1 gas jar with an attached one liter anesthesia bag. The lung model was ventilated at present tidal volumes and frequencies. The authors also compared the measured respiratory quotient (RQ) with the known RQ of burning methanol (RQ = 0.67) in the jar. When the model was ventilated with levels of tidal volume and gas exchange applicable to adults, both instruments measured V02 within 5 to 13% of predicted values. Varying the FI02 did not significantly affect this accuracy. At tidal volumes below 350 ml, the difference increased between predicted VCO2 and measured VCO2. The difference between measured vs. the actual RQ of methanol was 5 and 1.5% in the Siemens-Elema and Beckman Systems, respectively.

Carbon Dioxide↗
PubMed1982

Effect of posture on the ventilatory response to CO2.

The effect of sitting and supine posture on breathing patterns and gas exchange during room air breathing and administration of 2 and 4% CO2 was studied in nine normal subjects using a noninvasive canopy system. During air breathing minute ventilation (VE) was 21% (P less than 0.005) higher in the sitting position. Tidal volume (VT) and mean inspiratory flow (VT/TI) were also greater in the sitting position. With the administration of 4% CO2, VE was 13.9 and 20.0 1/min in the supine and seated position, respectively. The relationship between VE and VT was the same in both cases. For any given level of VE, VT/TI was higher in the seated position. No difference in response to CO2 as measured by delta VE/delta PaCO2 and (delta VT/TI)/delta PaCO2 was observed. However, arterial PCO2 was lower both in the resting and stimulated states when sitting.

Adolescent↗
PubMed1981

Nutrition for the patient with respiratory failure: glucose vs. fat.

High glucose intakes given during administration of total parenteral nutrition (TPN) have been demonstrated to increase CO2 production. The workload imposed by the high CO2 production may precipitate respiratory distress in patients with compromised pulmonary function. Changes in CO2 production and O2 consumption induced by TPN using either glucose as the entire source of non-protein calories, or fat emulsions as 50 per cent of the non-protein calories, have been analyzed either in patients with chronic nutritional depletion or in acutely ill patients secondary to injury and infection. In patients with chronic nutritional depletion, shifting from the lipid to the glucose system caused a 20 per cent (P less than 0.025) increase in CO2 production which resulted in a 26 per cent increase in minute ventilation (P less than 0.01). In the acutely ill patients receiving the glucose system, CO2 production was significantly higher than in those receiving the lipid system (179 vs. 147 ml.min-1.m-2; P less than 0.01. Fat emulsions can serve as a source of non-protein calories and are associated with lesser degrees of CO2 production than isocaloric amounts of glucose.

Adolescent↗
PubMed1981

Dobutamine in the rejecting transplanted heart.

Dopamine is commonly used to improve cardiac output and to maintain peripheral perfusion after myocardial injury. It has several advantages over other catecholamines. At effective inotropic dose levels, dopamine produces less peripheral vasoconstriction than norepinephrine. Dopamine also causes fewer arrhythmias than isoproterenol. This is a case report of a heart transplant patient who began rejecting and developed heart failure. In addition to the immunosuppressive agents, dopamine was used initially as the vasopressor with marked deterioration in the patient's condition. Dobutamine, a new inotropic agent, was substituted for dopamine with subsequent improvement in cardiac function. The authors concluded that dobutamine may be the most appropriate agent to use in the rejecting transplanted heart because of the former's direct action on the heart. Dobutamine may also be preferred for support of the cardiac outputs of patients with chronic heart failure.

Cardiotonic Agents↗
PubMed1980

Respiratory changes induced by the large glucose loads of total parenteral nutrition.

Total parenteral nutrition (TPN) using glucose as nonprotein calories was associated with increases in O2 consumption (VO2) and CO2 production (VCO2). The magnitude of the changes was a function of the patient's clinical state and glucose load. Depleted patients showed a minimal increase in VO2, while VCO2 increased 23%. Minute ventilation (VE) increased 32%. Hypermetabolic patients (major trauma, sepsis) had a 30% increase in VO2 and a 57% increase in VCO2, while VE increased 71%. Patients with mild to moderate injuries (energy expenditure +/- 15% of normal) showed a 21% increase in VO2 and a 53% increase in VCO2, while VE increased 121%. Large carbohydrate intakes were associated with increases in CO2 production in all patients, while increases in O2 consumption were seen primarily in hypermetabolic patients. These changes suggest that the high glucose loads of TPN may be a physiologic stress.

Adult↗
PubMed1980

Ventilatory requirements of critically ill neonates.

Ventrilatory requirement was assessed in 15 critically ill neonates on a total of 31 occasions. All were either currently receiving mechanical ventilation or had had mechanical ventilation in the recent past. Minute ventilation, respiratory frequency, carbon dioxide production (VCO2) and arterial blood PaCO2 were measured. Dead space-to-tidal volume ratios (VD/VT) were calculated. The ventilatory requirements of the infants ranged from 1.16 to 4.30 times normal. Derived parameters related the increased ventilatory requirement to pulmonary (VD/VT) and metabolic (VCO2) factors. The increased requirement was not significantly related more often to either of these two factors, although one or the other was frequently predominant in individual cases. Data presented allow specification of the minute volume range needed for ventilators designed for neonates, and the maximal compressible volume that can be tolerated when expired volume monitoring is desired.

Body Weight↗
PubMed1980

Increased body temperature secondary to total parenteral nutrition.

Administration of total parenteral nutrition (TPN) (glucose/amino acids), on the 2nd day after surgery, to a 26-year-old male with multiple fractures resulted in a rise in rectal temperature from 37.6 to 39 degrees C. Resting energy expenditure showed a sustained 23% increase when the nutritional intake was changed from 5% dextrose to TPN. This case demonstrates that the increased metabolic rate associated with administration of TPN in acutely injured patients may be associated with an increase in body temperature.

Adult↗
PubMed1980

Use of the ventilatory equivalent to separate hypermetabolism from increased dead space ventilation in the injured or septic patient.

Normal subjects and surgical patients were studied with a noninvasive canopy-spirometer system which provides prolonged measurements of gas exchange and pattern of breathing. Values for normal subjects agreed with published values. Twenty-nine patients undergoing uncomplicated elective operation had a mean preoperative minute ventilation of 3.44 +/- 0.84 L/min/m2, a VO2 of 0.132 +/- 0.022 L/min/m2, and VCO2 of 0.105 +/- 0.017 L/min/m2, and the postoperative values on the third to fifth day were not statistically different. The ventilatory equivalent (V.E.CO2) or the liters of air moved per liter of CO2 excreted has been used instead of the dead space/tidal volume (VD/VT) ratio for the indication of levels of minute ventilation, which are excessive for the associated metabolic demands for gas exchange. Thirty-eight runs on 18 acutely ill surgical patients showed mean increases in minute ventilation of 85%; the associated increases in metabolism averaged 17%. Therefore, their V.E.CO2 increased from a normal of 31 +/- 6 to 50.7 +/- 8, indicating a sharp increase in dead space ventilation. The additional clinical information provided by the serial graphic presentation of V.E.CO2 supplements what is learned from successive numbers representing the trend in VD/VT.

Bacterial Infections↗
PubMed1980

Effects of respiratory apparatus on breathing pattern.

The effects of ventilatory apparatus on breathing pattern and gas exchange were studied in normal supine subjects. Using a canopy system, measurements of O2 consumption, CO2 production, tidal volume (VT), frequency (f), minute ventilation, mean inspiratory flow, and inspiratory, and expiratory time (TI and TE) were made and compared to data obtained with the use of a mask (m) and mouthpiece plus noseclip (mp + nc). Use of the m or mp + nc caused a 32.5 and 15.5% increase in VT, respectively, whereas f, TI, and TE remained unchanged. As TI did not change the increase in VT was caused entirely by increased inspiratory flow.

Adult↗
PubMed1979

Patterns of ventilation in postoperative and acutely ill patients.

Acutely ill patients commonly increase minute ventilation (V) to varying degrees. The pattern of breathing utilized to increase V was analyzed in normal subjects and acutely ill surgical patients. V = tidal volume (VT) x frequency (f), or V = inspiratory flow x (TI/TTOT, inspiratory time/total cycle time). CO2 inhalation and exercise were used to induce supine hyperventilation in normal subjects. This was compared to hyperventilation in acutely ill surgical patients. Measurements were made of O2 consumption, CO2 production, V, VT, f, inspiratory flow, TI, and TTOT. With small increases in V (up to twice control), normal subjects increased inspiratory flow and TI/TTOT with both CO2 and exercise. CO2 inhalation increased VT with no change in f, while exercise increased both VT and f. When V increased beyond twice control, TI/TTOT remained constant and increases in inspiratory flow accounted for the entire increase in V. In acutely ill patients with increased V, average f was elevated and VT decreased, but there was no constant relationship of f and VT with increasing V. However, TI/TTOT was relatively constant at 0.40- 0.46; therefore, in order to increase V, inspiratory flow had to increase! Patients also showed a tendency to breathe at a relatively fixed VT while normal subjects did not show this phenomenon, even with increases of up to 3 times control V. Continuous, rapid analysis of gas exchange and breathing patterns holds promise for early detection of patients with V inappropriate to metabolic demands, and serves as a sensitive indicator of abnormal patterns used by acutely ill patients to increase V.

Acute Disease↗
PubMed1979

Effects of hypercaloric glucose infusion on lipid metabolism in injury and sepsis.

UNLABELLED: Lipolysis was studied by measuring glycerol turnover (GTO) in injured and infected patients. GTO was elevated two to three times the normal values in five injured and four infected patients during D5W infusion. No correlation was found between GTO and plasma glycerol concentration in the two patient groups. GTO showed similar levels when measured during TPN in five injured and three infected patients. During TPN, plasma FFA levels remained unchanged in injured but decreased by 48% in septic patients. B-OH butyrate concentrations were high during D5W and dropped in both groups during TPN. Norepinephrine urinary output was high in both groups during D5W and TPN. CONCLUSIONS: 1) GTO was elevated two to three times the normal range in injury and infection; plasma glycerol concentration was not related to GTO. 2) In face of high catecholamine output, the insulin response to TPN did not inhibit TG breakdown but did decrease plasma ketone body concentrations.

Adult↗
PubMed1979

Influence of exercise and CO2 on breathing pattern of normal man.

Ventilatory patterns during rest, CO2 inhalation (2, 3, and 4%) and three levels of exercise were analyzed in supine men using a canopy system for noninvasive measurements. Changes in tidal volume (VT) and breathing frequency (f) with equal increases in minute ventilation (VE) differed significantly during exercise and CO2 inhalation. Increases in VE during exercise was accompanied by increases in VT and f. During CO2 inhalation, the change in frequency was less than during exercise. However, when analyzed in terms of inspiratory flow (VT/TI) and inspiratory duty cycle (TI/Ttot), the response to both stimuli was similar. With increases to twice control VE both TI/Ttot and VT/VI increased. Thereafter only VTTI increased with increasing VE. At rest, inspiratory time on a breath by breath basis increased minimally with VT, while changes in inspiratory flow accounted for the variability in VT. These two respiratory stimulants appear to increase ventilation through different mechanisms when analyzed in terms of VT and f. However, changes in inspiratory flow and duty cycle are similar in both.

Adult↗