PubMed Health⌕ Search

Biomedical subjects

M H Bryan

Publications and source records attributed to M H Bryan.

At least 37 records · Page 2Linked to original sources
PubMed1981

Human milk feeding in premature infants: protein, fat, and carbohydrate balances in the first two weeks of life.

The nutritional adequacy of the premature infant's own mother's milk was assessed during the first two weeks of life. Studies were carried out in three groups (n = 8) of infants of less than 1,300 gm birth weight, matched for gestational age and weight, and fed either pooled breast milk, their mothers own milk, or infant formula (SMA20 or SMA24). Macronutrient balances at the end of the first and second postnatal weeks demonstrated differences in nitrogen and lipid absorption and retention between groups. Nitrogen retentions (mg/kg/day) were similar to normal fetal accretion rates only in the PT and SMA24 groups. Fat absorption was poorest from the heat-sterilized PBM (average of 64.0% of intake) when compared to PT (88.2%) and SMA groups (83.3%). Average gross and metabolizable energy intakes were similar among groups. Nutritional status as measured by plasma total protein and albumin concentrations and weight gain tended to be poorest in the PBM-fed infants. It was concluded that either PT milk or infant formula of a composition similar to SMA24 are more appropriate than pooled banked milk for feeding the premature infant during the first two weeks of life.

Anthropometry↗
PubMed1981

Treatment of RDS by high-frequency oscillatory ventilation: a preliminary report.

The feasibility of high-frequency oscillatory ventilation was investigated in eight neonates with severe RDS. Low-volume, high-frequency flow oscillations were generated by a piston pump and delivered through standard endotracheal tubes. Oscillatory frequencies ranged from 8 to 20 Hz and mean airway pressure from 9 to 20 cm H2O. Heart rate, airway pressures, and arterial blood gases and blood pressure were monitored during both continuous positive pressure ventilation and HFO. During HFO mean PaCO2 was 44.0 +/- 4.8 mm Hg. During CPPV immediately prior to oscillation an FIO2 of 0.66 +/- 0.15 resulted in a PaO2 of 59.6 +/- 17.0 mm Hg. Oxygenation improved during HFO such that a mean FIO2 of only 0.41 +/- 0.11 was needed for similar oxygenation. Improvements in oxygenation correlated directly with increases in mean airway pressure. Based on an animal model the phasic pressure swings during HFO are estimated to be 5 to 7 cm H2O in the trachea, much less than conventional ventilation. We conclude that HFO shows great promise in the support of gas exchange in infants with RDS. The use of small phasic volume and pressure swings should minimize pulmonary barotrauma. HFO should also permit the use of lower inspired oxygen fractions.

Humans↗
PubMed1981

Intravenous nitrogen and energy intakes required to duplicate in utero nitrogen accretion in prematurely born human infants.

In order to determine the intravenous energy and nitrogen intakes required to achieve intrauterine rates of nitrogen accretion and growth, 30 studies were completed in 22 premature infants who were provided with various intakes of amino acids and energy (glucose +/- lipid) by peripheral vein infusion. At constant nitrogen intake, increasing energy intake (as lipid) from 50 to 80 nonprotein kcal/kg/day resulted in significant increases in nitrogen retention and weight gain. Increasing nitrogen intake from 494 to 655 mg/kg/day at constant low energy intake (mean = 53 kcal/kg/day) had no effect on nitrogen retention or weight change; however, at higher energy intakes (mean = 81 kcal/kg/day) increasing nitrogen intake correlated significantly with increasing nitrogen retention. At energy intakes greater than 70 kcal/kg/day the major determinant of nitrogen retention was nitrogen intake. When energy intake was greater than 70 kcal/kg/day, the infusion of nitrogen providing 430 to 560 mg/kg/day (2.7 to 3.5 gm protein/kg/day) resulted in the duplication of intrauterine nitrogen accretion rates.

Amino Acids↗
PubMed1981

Energy and macronutrient content of human milk during early lactation from mothers giving birth prematurely and at term.

The lactose, lipid, protein, and total energy content of milk produced during the first 4 wk of lactation was determined in milk from mothers giving birth prematurely and at term. Milk samples analyzed were representative of complete 24-h expressions. Over the first 4 wk of lactation lactose concentration increased, but nitrogen concentration decreased by an average of 25%. Lipid and total energy concentration increased by 25% from the 1st to 2nd wk and then remained stable in both groups. Although these changes with duration of lactation were similar in both groups, premature compared to full term milk was consistently 20 to 30% higher in total energy and lipid concentration, 15 to 20% higher in total protein and, after the 1st wk, approximately 10% lower in lactose. By comparing predicted nutrient intakes to estimated requirements of premature infants fed 150 to 200 ml/kg/day of their own mothers' milk, we predict that the quantities of protein and energy provided would be adequate to meet the needs of the infant during the early weeks of life.

Adult↗
PubMed1981

Cysteine supplementation to cysteine-free intravenous feeding regimens in newborn infants.

To determine if cysteine is an essential amino acid for the intravenously fed newborn infant, growth parameters, nitrogen balance, plasma sulfur amino acid levels, and urinary amino acid excretion of premature and term infants were measured in the presence or absence of infused cysteine. Control intravenous formulations provided amino acids, including adequate methionine, carbohydrate, lipid, minerals, vitamins, and trace elements to all infants. Group and pair-matched comparisons showed that nitrogen retention, weight change, and growth in length and head circumference were not affected by cysteine supplementation of 77 mg/kg/24 h. The failure of cysteine supplementation to alter nitrogen retention was independent of postnatal age or gestational age. Plasma 1/2 cystine concentration was increased by 60% in the supplemented group with a concomitant 3-fold increase in urinary excretion of 1/2 cystine and taurine, but not of urinary methionine or cystathionine. Cysteine-supplemented infants exhibited a small increase in 3-methylhistidine excretion compared to pair-matched controls, suggesting that either an increase in muscle protein catabolism or an increase in muscle mass may have occurred.

Amino Acids↗
PubMed1981

Synergistic behavior of inspiratory muscles after diaphragmatic fatigue in the newborn.

We studied diaphragmatic and intercostal muscle activity and the pattern of motion of rib cage and abdomen after diaphragmatic muscle fatigue in 15 newborn infants (birth wt 1,251 +/- 424 g, mean +/- SD). Rib cage and abdominal motion were monitored with magnetometers and intercostal and diaphragmatic electromyograms (EMG's) with surface electrodes. Twelve infants showed a total of 66 episodes of muscle fatigue identified by EMG frequency spectrum analysis. Two patterns of responses to fatigue were observed. In the first case, five infants consistently recruited their intercostal muscles; this was followed by a normalization of the diaphragmatic frequency spectrum. In these infants, recruitment of intercostal muscles successfully prevented any clinical deterioration. In the second, seven infants showed no change in their intercostal muscle activity, and diaphragmatic fatigue was followed by apnea. We conclude that in newborn infants the synergistic behavior of the diaphragm and intercostal muscles can maximize the performance of these muscles and, in some infants, seems to prevent development of apnea.

Apnea↗
PubMed1981

Importance of inspiratory muscle tone in maintenance of FRC in the newborn.

The importance of inspiratory muscle tone in the maintenance of functional residual capacity (FRC) in newborns was studied in eight premature infants with birth weights of 1,166 +/- 217 g and gestational age 29 +/- 1.9 wk (mean +/- SD). Rib cage and abdominal anteroposterior diameters were monitored with magnetometers, and electromyograms of the diaphragm and intercostal muscles were recorded with surface electrodes. Sleep state was monitored using electrooculogram and behavioral criteria. We assessed the decrease in tonic activity of the inspiratory muscles and the fall in end-expiratory lung volume during apnea compared with the period just preceding apnea. A total of 98 apneas were analyzed. In all instances a decrease in diaphragmatic and intercostal tone was associated with a decrease in the anteroposterior diameter of both rib cage and abdomen, indicating a fall in FRC. These changes were more marked during quiet sleep than during rapid-eye-movement sleep (P less than 0.01). Our results suggest that inspiratory muscle tone is a major determinant of FRC in the newborn.

Apnea↗
PubMed1981

Respiratory induction plethysmography (Respitrace): an evaluation of its use in the infant.

Respiratory Induction Plethysmography (RespitraceTM) is a recently described method for noninvasive respiratory monitoring in adults. We report here on its calibration and use in 15 infants. Tidal volume, as measured by this method, was compared with the tidal volume integrated from a pneumotachygraph attached to a tightly fitted face mask. The 2 volumes had a correlation greater than 0.85 (p less than 0.001) with a slope between 0.9 and 1.1. The results were similar in both quiet and rapid eye movement sleep demonstrating that the method can accurately follow paradoxical inward rib cage movement. However, the accuracy decreased at respiratory rates above 80 breaths/min. When the minute ventilation was computed over the same sampling interval by both methods, the mean difference was +0.2 +/- 3.4% (+/- 1 SD) in quiet sleep and +0.8 +/- 4.5% in rapid eye movement sleep. We concluded that this is an accurate method of measuring long-term minute ventilation and tidal volume in small infants, provided that both the calibration procedure and measurements are made in the same posture, and the infant's respiratory rate is less than 80 breaths/min.

Adult↗
PubMed1981

Net acid excretion during first week of life.

Metabolic acidosis occurs frequently in newborns. Net acid excretion (NAE) in 34 preterm and 12 term infants was measured during the first week of life. Twenty preterm infants received breast milk or formula; the remaining infants received total parenteral nutrition (TPN) -- synthetic amino acids or casein hydrolysate solution. NAE for breast milk vs formula fed infants was 5.4 +/- 0.4 and 7.8 +/- 0.6 muEq/min/m2 (mean +/- SEM). The corresponding values for the two TPN solutions in preterm infants were significantly higher at 12.5 +/- 1.4 and 19.4 +/- 3.5 muEq/min/m2. Term infants produced even greater amount of net acid, 20.6 +/- 2.9 and 35 +/- 3.7 muEq/min/m2 respectively for the two TPN solutions. Milk fed infants are less prone to acidosis because of base generated from milk consumption. Due to its inherent acidogenic effect, TPN solutions induce acidosis more readily. Infants receiving TPN are therefore required to generate a higher NAE rate to maintain acid-base homeostasis compared to milk fed infants.

Acid-Base Equilibrium↗
PubMed1980

Macro-mineral content of milk obtained during early lactation from mothers of premature infants.

Milk from mothers giving birth prematurely was analyzed for Na, Cl, K, Mg, Ca and P concentrations. The data presented are from analyses of milk samples representative of complete 24-hour expressions and collected serially over the first 29 days of lactation from mothers giving birth at term (FT) and mothers giving birth prematurely (PT). Mineral composition of FT and PT milks was similar during the first month lactation. With the exceptions of Mg and P, the concentrations of the minerals studied were higher initially than at the end of the fourth week of lactation. From these data, intakes of premature infants fed their own mothers' milk can be estimated and compared to predicted mineral requirements for the premature infant. On the basis of this comparison, we suggest that the quantities provided of Na, Cl, K and Mg, but not Ca and P, would be adequate to meet requirements of premature infants during the early weeks of life.

Adult↗
PubMed1980

Human milk: comparison of the nitrogen composition in milk from mothers of premature and full-term infants.

Total nitrogen concentration of human milk during the first 4 weeks of lactation is higher in milk obtained from mothers giving birth prematurely than in milk from mothers giving birth at term. In the present study, the relative composition of total nitrogen was found to be similar in premature and full-term milk except for some minor differences in small molecule components. Total nitrogen is comprised of an average of 82% protein, 8% of the nonprotein nitrogen components--urea, free amino acids, uric acid, and ammonia--and the remaining 10% is predicted to be peptide nitrogen.

Female↗
PubMed1980

Congenital central hypoventilation and sleep state.

Congenital central hypoventilation (Ondine's curse) is described in an infant with persistant symptoms throughout the first nine months of life. Respiratory control was most severely affected in quiet sleep, although abnormalities were present in rapid eye movement (REM) sleep and while awake. Failure of metabolic control in quiet sleep led to profound hypoventilation. Behavioral or "behavioral-like" inputs in the awake state and REM sleep increased ventilation, but not to expected normal levels. The ventilatory response to inhaled 4% CO2 was markedly depressed in all states.

Carbon Dioxide↗
PubMed1979

The consequences of diaphragmatic muscle fatigue in the newborn infant.

We have previously demonstrated that diaphragmatic muscle fatigue can be diagnosed in infants from spectral frequency analysis of the surface diaphragmatic electromyogram. This requires a digital computer, but the analysis takes several days. Spectral frequency changes, however, can be accurately reflected by band pass filtering and expressing the ratio of high-frequency power to low-frequency power. A fall in this ratio of greater than 20% indicates muscle fatigue. Using a simple analog device to obtain this ratio permits the results to be immediately available; we have used this method to study weaning from mechanical ventilators in ten infants. With a successful weaning step there is no significant change in the ratio, whereas an unsuccessful weaning step invariably leads to a decrease in the ratio of greater than 20%, which precedes CO2 retention and clinical deterioration. These data indicate that diaphragmatic muscle fatigue plays an important role in the infant's response to lung disease. Monitoring of the high/low frequency ratio may be helpful in weaning infants from assisted ventilation.

Computers, Analog↗
PubMed1979

Diaphragmatic muscle tone.

It is generally believed that there is a scarcity of muscle spindles in the diaphragm and that there is no tonic activity at end expiration. This conclusion is based mainly on animal studies and the difficulty in differentiating tonic electromyogram activity from noise. We have, however, found a number of muscle spindles in the newborn human diagphragm, concentrated in the region of the central tendon. We also tried to detect tonic activity by decreasing it (by rapid-eye movement (REM) sleep or anesthesia) or increasing it (with abdominal loading). During REM sleep in five infants and five adults, using subcostal electrodes were observed a marked fall in tonic activity (P less than 0.001) compared to non-REM or quiet sleep. We also observed a reduction in diaphragmatic tonic activity with halothane anesthesia (P less than 0.001). With esophageal electrodes in adult subjects, there was a rise in tonic diaphragmatic activity proportional to the amount of abdomina load (P less than 0.001). We conclude that there are muscle spindles in the human diaphragm and that there is tonic activity at end expiration.

Adult↗
PubMed1979

Appearance and characterization of lipoprotein X during continuous intralipid infusions in the neonate.

The development of hyperphospholipidemia and hypercholesterolemia was studied in infants that required total parenteral nutrition and given a continuous infusion of Intralipid, (1-4 g/kg body wt per 24 h. Detailed studies were carried out on infusion periods lasting 1-10 d. After 24 h there was a marked increase in plasma free cholesterol (68%) and phospholipid (77%) concentrations. Based on the amount of cholesterol in Intralipid, and the rate of infusion, it was estimated that at least 50% of the plasma cholesterol increment during 64-h infusions was derived from endogenous sources. By contrast, the hyperphospholipidemia could be attributed to the Intralipid as the rise in plasma was calculated to be equivalent to only 16% of the exogenous phospholipid infused. Approximately 10% of the phospholipid in Intralipid was in a triglyceride-free mesophase form with a free cholesterol:phospholipid molar ratio of 0.063. There were no systematic changes in plasma concentrations of cholesterol ester or triglyceride during Intralipid infusions. The increase in free cholesterol and phospholipid was localized in the low density lipoproteins (d = 1.006-1.063 g/ml). The presence of lipoprotein X (Lp-X) in the low density lipoprotein fraction was demonstrated by electrophoresis in agar and by isolation and chemical characterization with hydroxylapatite chromatography. Isoelectric focusing of urea-soluble protein of Lp-X revealed that albumin and apolipoproteins CII and CIII were major components, whereas apolipoprotein E and AI were minor constituents. The abnormal lipoprotein was apparent by 16 h during 64 h of infusion. After 6 d of continuous infusions the free cholesterol in Lp-X was 30+/-10 mg/dl (mean+/-SD), which represents a total Lp-X mass of 90 mg/dl. After cessation of the infusion, Lp-X, as monitored by electrophoresis in agar, disappeared within 72-96 h. Thus, during infusion of Intralipid in infants at rates commonly employed, the capacity of the clearance mechanisms for phospholipid are exceeded, which causes the accumulation of phospholipid and free cholesterol in the form of Lp-X particles. It is suggested that mesophase phospholipids in Intralipid may play a significant role in this process.

Apolipoproteins↗
PubMed1979

The effects of abdominal loading on rib cage distortion in premature infants.

The action of the diaphragm in inspiration is to decrease intrathoracic pressure and raise abdominal pressure, which elevates the rib cage. In the supine position, the rise in abdominal pressure is smaller because of the lack of abdominal muscle tone. In premature infants the inward pull of the diaphragm on the very compliant ribs causes inward movement on inspiration (ie, distortion) which is exacerbated by the lack of intercostal muscle activity during rapid eye movement (REM) sleep, their predominant state. We raised abdominal pressure by means of an inflatable cuff in 12 newborn infants (gestation 28 to 40 weeks) to try to improve inspiratory coupling of the rib cage and diaphragm. There was no significant change in minute ventilation, indicating no ventilatory impairment. In all studies in which there was distortion, abdominal loading produced a reduction or abolition of distortion (P less than .01). Abdominal loading may be useful in reducing diaphragmatic activity in premature infants.

Abdomen↗