PubMed Health⌕ Search

Biomedical subjects

M H Bryan

Publications and source records attributed to M H Bryan.

At least 19 recordsLinked to original sources
PubMed1994

Static respiratory compliance in the newborn. II: Its potential for improving the selection of infants for early surfactant treatment.

Static respiratory system compliance (Crs) and lecithin/sphingomyelin (L/S) ratios in tracheal aspirates were estimated in two independent groups of mechanically ventilated infants. Crs was measured rapidly at the cotside using a passive expiratory flow technique and L/S ratios were estimated in the laboratory by high performance liquid chromatography. In the reference group of 22 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 100% and a negative predictive value of 92%. In the validation group of 23 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 94% and a negative predictive value of 83%. Measurement of static Crs is a rapid, non-invasive technique which may usefully supplement current methods of selecting infants at high risk of respiratory distress syndrome.

Birth Weight↗
PubMed1987

Effect of bronchodilators on airway resistance in ventilator-dependent neonates with chronic lung disease.

Using a noninvasive passive flow volume technique to measure respiratory system resistance (Rrs) and compliance (Crs), the effects of two inhaled bronchodilators, salbutamol (beta 2-agonist) and ipratropium bromide (muscarinic blocker), were studied in 17 premature infants ranging in age from 19 to 103 days. All were ventilator dependent with chronic lung disease. The pretreatment Rrs was high (range 0.15 to 0.27 cm H2O X ml-1 X sec). After administration of salbutamol, the mean group Rrs decreased 24% +/- 11% (mean +/- SD), and Crs increased significantly, 17% +/- 21%. The response to ipratropium bromide in five infants did not differ significantly from their responses to salbutamol. Nebulized saline solution had no bronchodilator effect in five infants. These results suggest that in infants with early and late chronic lung disease, bronchospasm can be partially alleviated by inhaled bronchodilators.

Airway Resistance↗
PubMed1987

Diaphragmatic work of breathing in premature human infants.

Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.

Diaphragm↗
PubMed1987

Evaluation of respiratory inductive plethysmography in infants weighing less than 1,500 grams.

Calibration of the respiratory inductive plethysmograph (RIP) was performed in premature infants weighing less than 1,500 g. In only 25% of the studies was an acceptable calibration achieved, as assessed by statistical comparison of simultaneously measured pneumotachygraph and RIP tidal volumes. In 6 infants, dead space loading or air injection was performed in an attempt to alter abdominal and rib cage volume contributions and thereby improve the calibration. Neither of these maneuvers resulted in an improvement of the accuracy of the RIP calibration coefficient. We conclude that, when calibrated by the least squares technique, the reliability of inductive plethysmography in measuring tidal volume in small infants is low. This is presumably because they have very small tidal volumes and highly compliant rib cages.

Female↗
PubMed1987

Is chronic lung disease in low birth weight infants preventable? A survey of eight centers.

Chronic lung disease in prematurely born infants, defined as the need for increased inspired oxygen at 28 days of age, was thought to be more common in some institutions than in others. To test this hypothesis, we surveyed the experience in the intensive care nurseries at Columbia and Vanderbilt Universities, the Universities of Texas at Dallas, Washington at Seattle, and California at San Francisco, the Brigham and Women's Hospital in Boston, Texas Children's Hospital in Houston, and Mt Sinai Hospital in Toronto. The survey included 1,625 infants with birth weights of 700 to 1,500 g. We confirmed the relationship of risk to low birth weight, white race, and male sex. Significant differences in the incidence of chronic lung disease were found between institutions even when birth weight, race, and sex were taken into consideration through a multivariate logistic regression analysis. Columbia had one of the best outcomes for low birth weight infants and the lowest incidence of chronic lung disease.

Bronchopulmonary Dysplasia↗
PubMed1984

Spontaneous chylothorax in newborns.

During a 22-year period, 12 cases of spontaneous chylothorax in newborns were diagnosed at a large pediatric tertiary care center. Seven infants had right-sided effusions; only one effusion occurred on the left. Severe bilateral accumulations occurred in four nonimmune hydropic premature infants. The diagnosis was made by the milky appearance and/or the presence of more than 80% lymphocytes in the pleural fluid. Early diagnosis of the pleural effusion as chyle was associated with a less protracted course than when diagnosis was delayed. The total pleural fluid losses varied from 130 to 3,308 mL. Initial treatment included chest taps and/or drains in all the infants and mechanical ventilation in six. Oral feedings with standard or medium-chain triglyceride formulas were given in five; total parenteral nutrition was administered in seven. The conditions of two infants with copious and persistent drainage improved following surgery. All but one infant survived, and the chylothoraxes never recurred.

Chylothorax↗
PubMed1984

Rib cage and abdominal contributions to ventilatory response to CO2 in infants.

We have measured the ventilatory response to inhaled CO2 of six newborn infants in rapid-eye-movement (REM) and non-REM (NREM) sleep. Ventilatory responses were measured using the Read rebreathing technique. The response was further partitioned into the volume contributions of the rib cage and abdominal compartment using the respiratory inductance plethysmograph. Sleep state was defined by electroencephalogram, electrooculogram, and behavioral criteria. In NREM sleep, there was a highly significant linear correlation between both tidal volume (VT) and instantaneous minute ventilation (VI) with CO2. Among infants, the slope of VT varied from 1.0 to 0.34 ml X Torr-1 X kg-1. However, these differences were largely due to differences in rib cage contribution, which varied from 0.56 to -0.08 ml X Torr-1 X kg-1. The abdominal contribution was similar among infants (0.41-0.56 ml X Torr-1 X kg-1). In REM, the slopes of VI were less steep than in NREM, with greater breath-to-breath variability. Slopes of VT also tended to be lower. The abdominal responses were similar to those in NREM, whereas the rib cage response was low and negative in three studies. We conclude that the slope of the CO2 response curve is primarily determined by the extent of rib cage recruitment.

Abdominal Muscles↗
PubMed1983

Low flow oxygen therapy in infants.

Fifty one infants who were oxygen dependent after treatment for neonatal respiratory disease were entered into a study programme where 100% oxygen was delivered at low flow through a nasal catheter. Thirty five (69%) of the infants were discharged home and the remainder were either discharged to a convalescent hospital or back to their peripheral referring hospital. Excluding repeat admissions for monitoring or for the treatment of acute infections, 2760 hospital days (79 days/patient) were saved, representing a financial saving of $11990 (pounds 6500) per treated infant. A home low flow oxygen therapy programme has benefits to the infant/parent relationship, provides a more constant flow of oxygen than conventional methods, and the early hospital discharge represents a considerable financial saving.

Birth Weight↗
PubMed1983

Influence of chest wall distortion on esophageal pressure.

The caudocephalad profile of esophageal pressure swings was studied in 10 preterm and 5 full-term infants, and the effect of chest wall distortion on esophageal pressure swings was analyzed in 12 preterm infants. Esophageal pressure was measured with a fluid-filled catheter, tidal volume with a pneumotachograph, mouth pressure with a face mask and pressure transducer, and rib cage and abdominal motion with magnetometers. In preterm infants the profile of esophageal pressure swings fell very steeply in the caudocephalad direction. In full-term infants it was flat during quiet sleep and steep during rapid-eye-movement sleep. When breaths, standardized for pleural pressure, were compared between a period with maximal and a period with minimal chest wall distortion, esophageal pressure swings for both spontaneous and occluded breaths were higher in the former period. We conclude that the complaint preterm rib cage results in an uneven distribution of pleural pressure and that this distribution varies with changes in chest wall distortion. Esophageal pressure measurements are therefore an unreliable estimate of mean pleural pressure in the preterm infant and can be unreliable in the term infant.

Esophagus↗
PubMed1983

Effect of chest wall distortion on occlusion pressure and the preterm diaphragm.

We studied the effect of chest wall distortion (CWD) on transdiaphragmatic pressure (Pdi) and/or mouth pressure during end-expiratory airway occlusions in seven preterm infants. We measured mouth occlusion pressure (Pmo) with a face mask and pressure transducer, gastric pressure (Pga) with a fluid-filled catheter, diaphragmatic electromyogram (Edi) using surface electrodes, and rib cage and abdominal motion using magnetometers. We reasoned that Pdi = Pmo - Pga on airway occlusion. Periods with maximal and periods with minimal CWD were compared. We found that 1) when CWD was minimal, an increase in Edi produced an increase in Pmo and Pdi in all infants; when CWD was greatest, large increases in Edi produced no increase in Pmo or Pdi in four infants; 2) when breaths with the same Pmo or Pdi from each period in each infant were compared, those from the period with greatest CWD had an increased Edi (mean increase 76%, P less than 0.005, and 144%, P less than 0.01, for Pmo and Pdi, respectively). We conclude that in preterm infants, Pmo can be a poor indicator of respiratory drive, and CWD markedly limits the effectiveness of the diaphragm as a force generator.

Diaphragm↗
PubMed1983

Variations in intralipid tolerance in newborn infants.

Intravenous Intralipid tolerance tests (IVLTT) were done in 26 newborn infants of 26-40 wk gestational ages. The clearance constants (k2) ranged from 1.2-12.7 (%/min) after bolus injections given within 4.5 h (n = 12) or daily (n = 13). Significant variation (17-31%) occurred, similar to adults, and was unrelated to the time or dose given. Eleven infants received continuous Intralipid infusions for 10-24 h at a rate calculated to maintain a plasma Intralipid plateau concentration of 100 mg/dl. Nine infants did not exceed this optimal plasma level, although four could have tolerated more Intralipid. Two infants exceeded the ideal plasma concentration (greater than 100 mg/dl). All infants achieved and maintained plateaus within 5 h. Neither day-to-day variations nor the bolus dose used to establish clearance characteristics, accounted for the discrepancies in plateaus achieved. These studies identify some limitations of the IVLTT as a predictor of Intralipid utilization during continuous infusion, and the need for early monitoring of plasma Intralipid concentrations to optimize the therapeutic dose given to newborn infants.

Fat Emulsions, Intravenous↗
PubMed1983

Hyaline membrane disease treated with bovine surfactant.

Six preterm infants with severe hyaline membrane disease requiring ventilation were treated, at a median age of 15.5 hours, with a single intratracheal bolus of a bovine surfactant suspension. Arterial oxygenation increased dramatically, and chest radiograms showed improvement after two to four hours. However, a variable degree of deterioration occurred within 24 hours. All of the infants required oxygen therapy for several weeks, and one developed severe bronchopulmonary dysplasia.

Animals↗
PubMed1983

Trace mineral balances in preterm infants fed their own mother's milk.

Balance studies were conducted on preterm infants (birthweight, 1,500 g or less) fed their own mother's milk or formula (SMA with iron) to compare the relative adequacy of these sources for copper (Cu), iron (Fe), and zinc (Zn). Urine and stools were collected for 72 h from infants aged 1, 2, or 4 weeks while they were fed milk or formula. Infants fed SMA 24 (but not SMA 20) received Cu, Fe, and Zn intakes within the recommended range. They did not, however, achieve estimated in utero retention rates for Fe, and were in negative Cu balance; they did approach in utero retention rates for Zn. Infants fed their own mother's milk received Cu and Zn, but not Fe, in recommended amounts. They achieved in utero retention rates for Cu at each age studied and approached the estimated in utero retention rates for Zn at 4 weeks, but they retained insufficient Fe throughout. Thus, neither the infant's own mother's milk nor this particular formula provides ideal amounts of all three minerals studied--Cu, Zn, and Fe--during the 1st month of life.

Copper↗
PubMed1982

Zinc, copper and iron content of milk from mothers of preterm and full-term infants.

Complete 24-hour expressions of milk were collected over the first month of lactation from mothers giving birth at term (FT) and prematurely (PT). Samples were analyzed for Cu, Fe and Zn concentration. Composition of PT and FT milks was similar during the first 4 weeks of lactation, but the concentrations of each mineral were higher during the first week than during the fourth week. From these data, the intakes of premature infants fed their own mother's milk were estimated and the proportion which must be absorbed and retained in order to accumulate the amounts laid down in utero were predicted. On the basis of these estimates, preterm infants who retain 25% of the Zn and 35% of the Cu in PT milk would approximate in utero accumulations. However, the Fe content of PT milk is unlikely to provide for in utero accretion rates, even if 100% absorption as achieved.

Adult↗
PubMed1982

Calibration of respiratory induction plethysmography (Respitrace) in infants.

To determine whether the recently increased sensitivity of the variable frequency oscillator and the use of separate rib cage and abdominal transducers made calibration of the Respitrace system easier, we performed 106 different calibration procedures against a pneumotachygraph in 36 normal infants, 41 using 2 separate periods of quiet sleep, 49 using quiet and REM sleep, and 16 using 2 separate periods of REM sleep. When the calibration was done using 2 separate periods of quiet sleep, or using periods of quiet and REM sleep, a change of at least 50% in the amplitudes of both the abdominal and rib cage signals between the 2 sleep periods, gave accurate calibration factors in 92%, compared with only 30% when the amplitude of either signal changed by less than 50%. Calculation of the calibration factors can be done either by the least squares method or by solving simultaneous equations with no significant difference between the results.

Humans↗
PubMed1982

Home apnea monitoring in 'near-miss' sudden infant death syndrome (SIDS) and in siblings of SIDS victims.

Electronic monitors were used at home to detect apnea in 134 infants who were considered to be at risk for sudden infant death syndrome (SIDS). Seventy-two infants had idiopathic apnea at a mean age of 2.2 +/- 1.4 (+/- 1 SD) months. Of these, 31 subsequently had prolonged apnea (greater than 20 seconds) with the last spell occurring at 6.2 +/- 3.2 months of age. Fourteen infants required vigorous stimulation on at least one occasion and 14 had more than ten separate episodes. Eighteen infants with awake apnea had a significantly smaller chance of subsequent spells (P less than .05). Ten additional term infants had apnea during the first week of life but none had subsequent episodes. Of 52 siblings of SIDS victims, only seven had had apnea before monitoring started. Sixteen had prolonged apnea while on a monitor; seven required vigorous stimulation on at least one occasion and one infant died despite cardiopulmonary resuscitation. The first documented spell in these 16 infants was at 2.6 +/- 2.1 months and the last at 7.2 +/- 2.7 months of age. Ten infants had more than ten subsequent spells. A tendency to clustering of spells was noted. Preceding events, especially a mild upper respiratory tract infection, were noted in 36 of the 47 infants who had apnea on the home monitor.

Apnea↗