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Biomedical subjects

R H Phibbs

Publications and source records attributed to R H Phibbs.

At least 55 records · Page 3Linked to original sources
PubMed1976

Persistent pulmonary hypertension of the newborn infant.

Persistent pulmonary hypertension of the newborn infant can be difficult to distinguish from other cardiopulmonary causes of cyanosis during the newborn period. Infants with PPHN have cyanosis, tachypnea, acidemia, normal pulmonary parenchymal markings on the chest radiography, and anatomically normal hearts. We have identified and treated 11 infants and have noted several signs and symptoms not previously emphasized. These are cineangiocardiographic evidence of atrioventricular valve insufficiency in association with systolic murmurs and slow ventricular emptying, apnea, hypocalcemia, only a small rise in abdominal aortic blood oxygen tension during breathing of 100% oxygen, and no response to continuous positive airway pressure. Right-to-left shunting through the patent ductus arteriosus was documented in nine infants: in all six of those in whom simultaneous temporal and abdominal aortic blood oxygen tension measurements were made; in three by means of cardiac catheterization. Ten infants survived after variable courses and treatments which makes it difficult to ascribe improvement to any one therapy. The distinct increase in blood oxygen tension with tolazoline HCl and curare in some instances is discussed.

Cyanosis↗
PubMed1976

Morphological development of the pulmonary vascular bed in fetal lambs.

The morphological development that accompanies increasing pulmonary blood flow and decreasing pulmonary vascular resistance with advancing gestational age has not been delineated. To study this point we developed a method of comparing pulmonary arterial vessels of the same generations in fetal lambs. Pulmonary arteries were perfused with glutaraldehyde solution at pressures appropriate for gestational age and then injected with an India ink-gelatin-Micropaque mixture. Using the dissecting microscope and serially prepared sections we studied successively smaller generations of arteries. We assessed the medial width/external diameter ratio in a total of 825 vessels from six fetal lambs of 85 to 140 days gestation. In fifth generation, or resistance vessels, this ratio remained constant over the gestational period studied (N = 529, Y = 0.16, slope = 0.0003). We measured the volume of 17-34 randomly selected sections from each of the six fetuses, counted the total number of fifth and sixth generation vessels in these sections, and calculated the total number of these vessels per right lung. This number increased from 0.10 X 10(6) to 4.08 X 10(6) with increasing gestational age. The number of vessels per unit volume increased from 7.2 X 10(3)/ml to 61.8 X 10(3)/ml or right lung over this gestational period. The results indicate that increased pulmonary blood flow and decreased pulmonary vascular resistance with advancing gestation are due to an increase in the total number of vessels and increased vasomotor reactivity is related to an increase in the total amount of smooth muscle while the thickness of muscle in individual vessels remains constant.

Animals↗
PubMed1976

Pneumothorax in the respiratory distress syndrome: incidence and effect on vital signs, blood gases, and pH.

We determined the incidence of pneumothorax in 295 infants (mean birthweight, 1,917 gm) with the respiratory distress syndrome (RDS) treated according to the same protocol. Fifty-five infants (mean birthweight, 1,594 gm) developed pneumothorax (incidence, 19%); incidence varied with severity of RDS and intensity of respiratory assistance. Pneumothorax occurred in 3.5% (2 of 58) of infants who received no assisted ventilation and in 11% (14 of 124) of infants who received continuous positive airway pressure (CPAP) as the only form of assisted ventilation; the difference between these two groups is not significant. Forty-nine infants initially treated with CPAP later required mechanical ventilation with positive end-expiratory pressure (PEEP). Pneumothorax occurred in 12 of the 49 (24%) and in 21 of 64 (33%) of those infants initially treated with PEEP; the incidence of pneumothorax for both these groups was significantly higher than for those treated with no assisted ventilation or CPAP only. To assess the value of frequent measurement of vital signs, blood gas tensions, and pH in the recognition of pneumothorax, we analyzed these variables by the cumulative sum statistical technique. We noted the following significant changes associated with pneumothorax: arterial blood pressure, heart rate, and respiratory rate decreased in 77% of cases; pulse pressure narrowed in 51% of cases; Po2 decreased in 17 of 20 cases in which ventilatory settings were constant for at least three hours prior to pneumothorax. However, pH and Pco2 showed consistent changes. Frequent measurements of vital signs and Po2 aid in the early diagnosis of pneumothorax.

Blood Pressure↗
PubMed1976

A volume-displacement plethysmograph to measure limb blood flow in the newborn infant.

An instrument is described that measures limb blood flow in newborn infants by venous occlusion plethysmography. The plethysmograph is filled with air and a pneumotachygraph measures the volume displaced during venous occlusion. The response of the system is linear for flows over the range 1 to 100 ml/min and the frequency response to a square wave pressure change is 22 Hz with a 95% response time of 0.5 second. The average flow in the forearm of 10 normal newborn infants was 5.9 ml/min per 100 ml of tissue.

Blood Flow Velocity↗
PubMed1976

Cardiorespiratory status of erythroblastotic newborn infants: III. Intravascular pressures during the first hours of life.

We measured aortic and central venous pressures beginning soon after birth in 40 prematurely born infants with moderate or severe erythroblastosis fetalis, including 13 with severe and 10 with mild hydrops fetalis. All but four were asphyxiated at birth and this affected intravascular pressures. Before resuscitation, aortic or central venous pressure or both were elevated in more than one third. All but two of the remaining infants had normal initial pressures. Following resuscitation which relieved acidosis, hypoxia, and anemia, but did not reduce blood acidosis, hypoxia, and anemia, but did not reduce blood volume, the high pressures usually fell to normal and occasionally to subnormal levels, normal pressures fell to subnormal in almost one half, and those with initial subnormal pressures remained hypotensive. In all, 40% were hypotensive after resuscitation; treatment with blood volume expanders consistently returned these pressures to normal. Only two of the 13 severely hydropic infants and none of the mildly hydropic had findings indicative of hypervolemia and myocardial failure which persisted after treatment of asphyxia.

Animals↗
PubMed1975

Angiographic and ultrasonographic appearance of renal cortical and medullary necrosis in the newborn.

Renal cortical and medullary infarction are 2 of the severe complications of perinatal asphyxia and shock. The angiographic and ultrasonographic findings in these conditions have not been described previously. They demonstrate nephromegaly, a nonhomogeneous nephrogram, and internal echoes. Similar findings may be seen in renal vein thrombosis, hydronephrosis, and polycystic kidneys.

Angiography↗
PubMed1975

Cesarean section prevents placenta-to-infant transfusion despite delayed cord clamping.

We have adapted and calibrated an accurate method for measuring residual placement blood volume (RPBV). We used this method in 33 normal vaginal deliveries and 18 cesarean section deliveries in which the umbilical cord was clamped from 5 to 118 seconds after delivery. Infants born vaginally received 10 to 20 ml. per kilogram of body weight of placental transfusion when umbilical cord was not clamped until 30 seconds or more after delivery. Equivalent delay of umbilical cord clamping in cesarean section infants produced no placental transfusion.

Birth Weight↗
PubMed1975

Continuous positive airway pressure and pulmonary and circulatory function after cardiac surgery in infants less than three months of age.

Continuous positive airway pressure (CPAP) was used to support the ventilation of infants less than 3 months of age who had undergone thoractomy for cardiovascular surgery. The functional residual capacity, which was approximately 30 per cent of predicted at zero CPAP, increased 35 per cent in cyanotic and 33 per cent in acyanotic infants with the application of 5 mm Hg pressure. Increasing airway pressure from zero to 5 mm Hg increased PaO2 4 per cent in cyanotic and 13 per cent in acyanotic infants. There was no change in heart rate, respiratory rate, mean arterial pressure, pH or PaC02 under similar circumstances, but central venous pressure increased 1.5 mm Hg in cyanotic and 0.8 mm Hg in acyanotic infants.

Blood Circulation↗