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Biomedical subjects

I D Frantz

Publications and source records attributed to I D Frantz.

At least 55 records · Page 3Linked to original sources
PubMed1985

Alveolar pressure swings during high frequency ventilation in rabbits.

In order to understand the pressures and volumes delivered during ventilation with the Emerson flow-interrupting high frequency ventilator, we have measured dynamic and mean pressures at the airway opening, trachea, and alveoli as well as delivered volumes in vivo in closed-chest adult rabbits ventilated at rates of 2-37.5 Hz. To measure alveolar pressure we opened the chest, glued an alveolar capsule to the visceral pleural surface, punctured the pleura and lung surface through the capsule, inserted a pressure transducer into the capsule and closed the chest. We measured delivered volume with a pressure plethysmograph. Alveolar pressure swings fell with increasing frequency, as did delivered volume. Alveolar pressure swings were always lower than those at the airway opening or in the trachea. Removal of the rib cage resulted in a decrease in alveolar pressure swings although muscle paralysis had little effect. Mean pressures were equal at the airway opening, trachea, and alveoli at all frequencies. These results suggest that using the high frequency ventilator tested, to minimize alveolar barotrauma one should choose the highest frequency where gas exchange is adequate.

Animals↗
PubMed1984

Comparison of effectiveness of thyrotropin-suppressive doses of D- and L-thyroxine in treatment of hypercholesterolemia.

In an attempt to compare the cholesterol-lowering effects of equivalent doses of D- and L-thyroxine, 10 euthyroid, hypercholesterolemic subjects were treated with graded doses of each medication in a cross-over design using thyrotropin suppression following thyrotropin-releasing hormone administration as the end-point. The mean thyrotropin-suppressive dose of D-thyroxine was 2.4 +/- 0.66 mg per day, which resulted in mean reductions of 10 percent in total plasma cholesterol, 10 percent in plasma low-density lipoprotein cholesterol, and 11 percent in plasma high-density lipoprotein cholesterol. The mean thyrotropin-suppressive dose of L-thyroxine was 135 +/- 46 micrograms per day, which resulted in mean reductions of 7 percent in total plasma cholesterol, 6 percent in plasma low-density lipoprotein cholesterol, and 14 percent in plasma high-density lipoprotein cholesterol. The reductions in total, low-density, and high-density cholesterol achieved with D-thyroxine were not significantly different from those achieved with L-thyroxine. Neither medication produced a significant increase in heart rate or ventricular ectopy as determined by Holter monitoring. These data do not support the belief that D-thyroxine has a preferential cholesterol-lowering effect in humans when compared with equivalent doses of L-thyroxine. In addition, both D- and L-thyroxine reduced plasma high-density lipoprotein cholesterol.

Adult↗
PubMed1984

Effect on ventilation of change to the upright posture in newborn infants.

We have investigated the effect of postural change on tidal volume (VT), inspiratory (TI) and expiratory (TE) duration, minute ventilation (VI), and end-tidal PCO2 in a group of 11 healthy full-term sleeping infants, 2-4 days of age. During tilts from the supine to upright posture, the average volume increase was 4.3 +/- 4.4 (SD) ml or 1.2 ml/kg in the maneuvers unassociated with sighs. In the 20% of tilts in which sighs occurred, the average volume change was slightly higher. Transition from supine to upright posture resulted in statistically significant increases in VT (6.45 +/- 0.06 to 6.72 +/- 0.06 ml/kg), TI (554 +/- 7 to 604 +/- 7 ms), and TE (629 +/- 12 to 777 +/- 14 ms), and decrease in VI (328 +/- 5 to 288 +/- 4 ml X kg-1 X min-1) (all means +/- SE, P less than 0.0005). Return to supine position resulted in statistically significant changes in the opposite direction. Tilting to the upright posture brought about a small (0.4 +/- 0.1 Torr, means +/- SE) but consistent statistically significant increase in end-tidal PCO2, which persisted through the first minute when the infant was returned to the supine position. The expiratory prolongation observed with tilting appears to minimize changes in end-expiratory lung volume, obviating the need for an effective compensatory muscle response to defend ventilation. Thus it appears that infants, in contrast to adults, adopt a breathing strategy to limit the extent of change in absolute lung volume, rather than to defend ventilation at increased lung volume.

Carbon Dioxide↗
PubMed1984

Apnea duration is related to ventilatory oscillation characteristics in newborn infants.

The occasional short apneas seen in full-term infants within the first postnatal week are related to the minimum phase of oscillatory breathing patterns. To determine the relationship between breathing patterns and the longer and more frequent apneas seen in premature infants, we monitored respiration in 14 premature infants using a face mask and pneumotachograph. Tidal volume, breath duration, and ventilation were calculated on a breath by breath basis, converted to time-axis data strings, and filtered with a comb of zero phase shift digital band pass filters to detect breathing patterns. Compared with full-term infants, premature infants had breathing patterns that occurred more often and had twice the average amplitude. Of 182 apneas greater than or equal to 3 s long, 94% occurred at the minimum phase of oscillatory breathing patterns. All of the 38 apneas greater than or equal to 10 s long occurred at the minimum phase of oscillatory breathing patterns. Duration of apnea was related to breathing pattern characteristics, e.g., longer apneas were related to stronger, longer cycle-time breathing patterns. Apnea in the premature infant is not an isolated event but is one aspect of an underlying pattern.

Apnea↗
PubMed1984

Alveolar pressure nonhomogeneity during small-amplitude high-frequency oscillation.

In six excised canine lungs, regional alveolar pressures (PA) were measured during small-amplitude high-frequency oscillations applied at the airway opening. Both the regional distribution of PA's and their relationship to pressure excursions at the airway opening (Pao) were assessed in terms of amplitude and phase. PA was sampled in several capsules glued to the pleural surface and communicating with alveolar gas via pleural punctures. Pao and PA were measured over the frequency (f) range 1-60 Hz, at transpulmonary pressures (PL) of 5, 10, and 25 cmH2O. The amplitude of PA excursions substantially exceeded Pao excursions at frequencies near the resonant frequency. At resonance the ratio [PA/Pao] was 1.9, 2.9, and 4.8 at PL's of 5, 10, and 25 cmH2O, respectively. Both spatial homogeneity and temporal synchrony of PA's between sampled lung regions decreased with f and increased with PL. Interregional variability of airway impedance [(Pao - PA)/Vao] and tissue impedance (PA/Vao) tended to be larger than differences due to changing PL but not as large as between-dog variability. These data define the baseline nonhomogeneity of the normal canine lung and also suggest that there may be some advantage in applying high-frequency ventilation at frequencies at least as high as lung resonant frequency.

Airway Resistance↗
PubMed1984

Hemodynamic response to high-frequency ventilation in infants following cardiac surgery.

The hemodynamic response to high-frequency ventilation was compared with conventional ventilation in six infants following cardiac surgery. While undergoing high-frequency ventilation, adequate gas exchange was maintained in all infants. High frequency ventilation allowed a reduction of peak ventilatory pressure at the airway opening by 19%, and peak tracheal pressure by 42%. No clinically important changes in heart rate, systemic and pulmonary arterial pressure, cardiac index, or systemic and pulmonary vascular resistance were noted when high-frequency ventilation was compared with conventional ventilation.

Blood Pressure↗
PubMed1983

The hypolipidemic effect of locust bean gum food products in familial hypercholesterolemic adults and children.

Seventeen adults and 11 children, a group of 18 familial hypercholesterolemic (FHC) and 10 normal subjects, were fed products with and without locust bean gum (LBG) (8 to 30 g/day) to assess the hypolipidemic effect of LBG. Identical food products with and without LBG were consumed by two groups (A and B) of arbitrarily assigned patients using a cross-over design. Plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, very low-density lipoprotein cholesterol and triglycerides were measured at 2-wk intervals and compared to control feeding periods. In group A, FHC C decreased 10% and LDL-C 11%, normal subjects decreased C 6% and LDL-C 10% (p less than 0.001). In group B, FHC C decreased 17% and LDL-C 19%, normal subjects decreased cholesterol 11%, and LDL-C 6% (p less than 0.001). Cholesterol and LDL-C were lowered in FHC children in both groups. High-density lipoprotein/LDL ratios increased in both groups. The use of food products with LBG in children and adults is a unique approach to treating FHC. LBG food acceptance was good, and there were no significant side effects. LBG in food products appears to be an effective, safe approach to controlling hyperlipidemia.

Adolescent↗
PubMed1983

Surfactant dysfunction in diabetic offspring: inhibitors and fatty acid lecithin content.

We have previously demonstrated that the lungs of fetuses of alloxan-diabetic rabbits are functionally immature when compared with controls. In this study we have examined pulmonary lavage fluid from fetuses of diabetic and control does for the presence of a surfactant inhibitor, cholesterol content, and phosphatidylcholine (lecithin) fatty acid content. When lavage fluids from fetuses of control and diabetic does were mixed and examined on the surface balance, the measured surfactant content corresponded to the arithmetic average of the surfactant content of the individual fluids, thus ruling out the presence of an excess of a surfactant inhibitor. We were able to demonstrate inhibition of surfactant function when exogenous cholesterol was added to lavage samples, but cholesterol content of lavage fluid from fetuses of diabetic and control does was not significantly different. Finally, the fatty acid composition of surfactant phosphatidylcholine was not different between the two groups. These studies indicate that mechanisms other than the presence of a surfactant inhibitor or altered fatty acid composition must explain the functional immaturity seen in offspring of the diabetic pregnancy.

Animals↗
PubMed1983

Respiratory system impedance from 4 to 40 Hz in paralyzed intubated infants with respiratory disease.

To describe the mechanical characteristics of the respiratory system in intubated neonates with respiratory disease, we measured impedance and resistance in six paralyzed intubated infants with respiratory distress syndrome, three of whom also had pulmonary interstitial emphysema. We subtracted the effects of the endotracheal tube after showing that such subtraction was valid. Oscillatory flow was generated from 4 to 40 Hz by a loudspeaker, airway pressure was measured, and flow was calculated from pressure changes in an airtight enclosure mounted behind the flow source (speaker plethysmograph). After subtraction of the endotracheal tube contribution, resistance ranged from 22 to 34 cmH2O liter-1 s; compliance from 0.22 to 0.68 ml/cmH2O; and inertance from 0.0056 to 0.047 cmH2O liter-1 s2. Our results indicate that, for these intubated infants, the mechanics of the respiratory system are well described as resistance, compliance, and inertance in series. Most of the inertance, some of the resistance, and little of the compliance are due to the endotracheal tube. When the contribution of the endotracheal tube is subtracted, the results are descriptive of the subglottal respiratory system. These data characterize the neonatal respiratory system of infants with respiratory distress syndrome (with or without pulmonary interstitial emphysema) in the range of frequencies used during high frequency ventilation.

Airway Resistance↗
PubMed1983

Lipid concentrations in serum and EDTA-treated plasma from fasting and nonfasting normal persons, with particular regard to high-density lipoprotein cholesterol.

Serum/plasma sample pairs, collected both during (12-h) fasting and nonfasting from 44 healthy subjects, were analyzed for total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. Values for total cholesterol and triglycerides averaged 2.1% and 5.2%, respectively, higher for serum than for plasma. Values for HDL cholesterol were not different. Triglyceride concentrations in nonfasting subjects were 40% higher than concentrations during fasting, but total cholesterol and HDL cholesterol were not significantly affected by fasting. These findings suggest that concentrations of HDL cholesterol may be directly compared in clinical and epidemiological settings without regard to whether serum or plasma was sampled or whether the subjects were fasting or nonfasting.

Adult↗
PubMed1983

High-frequency ventilation in premature infants with lung disease: adequate gas exchange at low tracheal pressure.

The technique of high-frequency ventilation (HFV) was used in ten infants with severe respiratory distress syndrome and five infants with pulmonary interstitial emphysema (PIE). The mean frequency used was 12 Hz (720/min). Peak tracheal pressure for the infants with respiratory distress syndrome was 28 +/- 4 (SD) cm H2O on conventional ventilation, and 22 +/- 4 cm H2O on HFV (P less than .05). For the infants with PIE, peak tracheal pressure decreased from 38 +/- 11 to 24 +/- 5 cm H2O (P less than .05). Mean tracheal pressure was the same for the two types of ventilation. No adverse clinical or pathologic side effects were seen. Clinical and radiologic improvements were seen in the infants with PIE after initiation of HFV. It is believed that these improvements in the patients with PIE were secondary to the decrease in tracheal pressure and that HFV may have a role in treatment of preexisting barotrauma and its prevention. These studies contribute to the preliminary data necessary before controlled trials of HFV in infants with respiratory distress syndrome and PIE can be carried out.

Humans↗
PubMed1982

Lightly hydrogenated soy oil versus other vegetable oils as a lipid-lowering dietary constituent.

Fully refined, bleached, deodorized corn oil and soy oil, and lightly hydrogenated, winterized soy oil were compared for effectiveness in lowering plasma cholesterol. Twenty-four, healthy, young college students were the subjects for the 10-wk studies. At the 300 cal level, the corn oil and unhydrogenated soy oil diets contained approximately 53 g of polyunsaturated and 26 g of saturated fat. The hydrogenated soy oil diet contained 42 and 25 g, respectively. All diets contained approximately 700 mg of cholesterol. Corn oil and unhydrogenated soy oil were equally effective in lowering both total and low density lipoprotein cholesterol. Lightly hydrogenated soy oil was also quite effective, but less so that the more unsaturated oils. Triglycerides were also lowered, but very low density and high density lipoprotein cholesterol concentrations, as well as total high density lipoproteins, were scarcely affected. All of the polyunsaturated fat diets produced small but statistically significant reductions in the cholesterol to protein ratio of all three lipoproteins.

Adult↗
PubMed1982

High-frequency ventilation does not affect pulmonary surfactant, liquid, or morphologic features in normal cats.

Effects on pulmonary surfactant, liquid, and morphologic features were compared in normal cats ventilated with conventional and high-frequency ventilators for 4 h. Normal blood gases and comparable mean airway pressures (approximately 7 cm H2O) were maintained with the two techniques. Peak tracheal pressure during conventional ventilation (16.5 +/- 0.9 cm H2O) was significantly greater than that during high-frequency ventilation (8.5 +/- 1.1 cm H2O, p less than 0.00001). Pressure-volume curves were identical in control, conventional, and high-frequency ventilation groups. There was no effect on pulmonary lavage surfactant, whether measured functionally or biochemically. Likewise, lung liquid and morphologic aspects examined by both light and electron microscopy were not affected. These results provide evidence that high-frequency ventilation under these conditions does not cause pulmonary damage.

Animals↗
PubMed1982

Complications of pregnancy and fetal development.

Although the outcome of pregnancy for women with diabetes mellitus has improved in recent years, the infant of the diabetic mother has an increased risk of major clinical problems, particularly in the early neonatal period. These include birth injury due to macrosomia, neonatal hypoglycemia, respiratory distress syndrome, and serious congenital anomalies. Because of the great difficulties encountered during attempts to investigate these problems in clinical research protocols, there is a continuing need to establish appropriate animal models of the diabetic pregnancy. Studies carried out over the past decade, primarily with chemically-induced diabetes have suggested techniques which might be useful. In general, the choice of the animal to be studied will depend on the hypotheses being addressed. For instance, small animals such as rabbits and rats made diabetic with streptozotocin have been successfully used for investigation of fetal lung development. Furthermore, the rat model has been helpful for evaluation of fetal anomalies associated with maldevelopment of the spine and central nervous system. Larger animals, such as the nonhuman primate, are more appropriate for studying placental function and amniotic fluid composition in diabetic pregnancies. The task group on pregnancy and fetal development recommends that animal models of diabetes mellitus be used for a more extensive hormonal and metabolic characterization of diabetic mothers during pregnancy, for investigation of placental physiology with respect to the transfer of substrates from mother to fetus, for systematic and comprehensive study of mechanisms controlling fetal lung development, and for delineation of the pathophysiology of neonatal hypoglycemia. It is further recommended that animal models of spontaneous diabetes such as the BB/W rat be used in future studies dealing with pregnancy and fetal development. Because females with spontaneous diabetes show reduced conception rates, there is a pressing need to enhance the fertility of these animals in order to intensify studies on fetal development.

Alloxan↗