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Biomedical subjects

R F Huxtable

Publications and source records attributed to R F Huxtable.

At least 19 recordsLinked to original sources
PubMed1990

Growth of the ferret tracheobronchial tree.

Because the ferret is being used increasingly in inhalation toxicology and lung physiology studies, it is necessary to better understand the airway structure of its tracheobronchial tree. Previously published information does not include dimensions of bronchi and bronchioles in either adult or growing ferrets. The airway structure of interest for calculating inhaled particle deposition patterns includes airway lengths, diameters and branching angles in each generation. Measurements of these dimensions were obtained for several selected airway paths on replica casts. Casts were made in-situ in four male litter mates age 14 hours, 9.5 days, 16.5 days and 56 days. These data demonstrate, that as with human lung growth, body length at a given age is a good predictor of airway lengths and diameters. Airway branch angles do not appear to change significantly during growth. Sufficient measurements were made to provide dimensions of a typical tracheobronchial pathway for this species. This pathway begins with the trachea and ends at the terminal bronchiole. The morphometric data were not sufficient to determine whether or not the number of tracheobronchial generations increase or decrease postnatally.

Animals↗
PubMed1986

Ligation of the patent ductus arteriosus in newborn respiratory failure.

Patent ductus arteriosus (PDA) is commonly associated with respiratory disease in newborn infants and may require ligation. Surgical ligation of the PDA can be done in small infants with low operative risk and minimal complications. The outcome of patients after ligation depends primarily on the severity of the underlying pulmonary disease. One hundred fifty-one patients have undergone ligation in an eight-year period at this center. A simplified technique performed in the neonatal intensive care unit with the use of local anesthesia and conventional ventilator management is described.

Birth Weight↗
PubMed1985

A noninvasive method for monitoring intestinal ischemia: changes in the pulmonary clearance of helium instilled into the colon as an index of colonic blood flow.

To evaluate the concept that changes in colonic blood flow will predictably alter the absorption of colonic gas, we measured the pulmonary clearance rate of helium (CHe) which was instilled rectally into the colon of rabbits at a dose of 2 ml/kg. CHE reached a plateau after 20 min at 109 nmol/min/kg. Using hypoxemia as a cause for bowel ischemia, at PAO2 = 38 torr, we noted a marked decreased in CHe from 110 nmol/min/kg to 75 nmol/min/kg (p less than 0.025). Because helium absorption from the colon is diffusion limited, a model can be developed relating "subvillus" colonic blood flow to pulmonary helium clearance. From this model we would predict the hypoxemia induced change in CHe to be secondary to colonic hypoperfusion. This type of indirect monitoring could be useful in detecting patients with bowel ischemia.

Animals↗
PubMed1984

Effects of polycythemia and hyperviscosity on cutaneous blood flow and transcutaneous PO2 and PCO2 in the neonate.

Neonatal hyperviscosity syndrome is known to affect multiple organ systems. The effects of polycythemic hyperviscosity on cutaneous blood flow and transcutaneous PO2 and PCO2 were compared in ten term infants prior to and following correction of the hyperviscous state. Cutaneous blood flow was measured by the heat clearance method; transcutaneous PO2 and PCO2 were detected by a polarographic O2 cathode and a potentiometric pH-sensitive glass electrode, respectively. Whole blood viscosity was measured at five shear rates from 11.25/s to 225/s using a Wells-Brookfield viscometer. Following partial exchange transfusion with fresh frozen plasma, there was a significant decrease in arterial blood hematocrit from 62.7% +/- 5.9% to 48.4% +/- 4.8% (P less than .001) and in whole blood viscosity from 13.9 +/- 2.9 cps to 8.5 +/- 1.8 cps (P less than .001) at a shear rate of 11.25/s. The arterial and transcutaneous O2 and CO2 tensions were in the normal range in the hyperviscous state and remained unchanged following exchange transfusion. The static measure of cutaneous blood flow increased 36% from 208 +/- 54 mW to 283 +/- 75 mW (P less than .01) while the dynamic measure of cutaneous blood flow increased 38% to 41% (P less than .01). The lack of demonstrable cutaneous hypoxia and hypercapnia, despite a significant decrease in blood flow in the hyperviscous state, may be due to one or more factors.

Blood Circulation↗
PubMed1981

In vivo evaluation of transcutaneous CO2 partial pressure monitoring.

Correlation between transcutaneous and arterial CO2 partial pressure (Ptcco2, and Paco2) under normal and hemorrhagic shock conditions was evaluated in rabbits. Under normal conditions the Paco2-to-Ptcco2 least-squares regression line had a slope of 1.03 an intercept of 4.57 Torr, and a root mean variance of +/- 3.79 Torr. Under hemorrhagic shock conditions the slope remained similar, but the intercept increased, producing a significant difference between arterial and transcutaneous values. The correlation line shifts to the left so that, for a given Paco2, the Ptcco2 value increases. The transcutaneous response time (90%) under conditions produced by breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the Paco2. The difference between transcutaneous and arterial CO2 observed during hemorrhagic shock and the lag in transcutaneous response time can be altered by topical application of dimethyl sulfoxide, by altering both flow and permeability. These results indicate that good Ptcco2-to-Paco2 correlation exists under normal conditions and that hemorrhagic shock will produce tissue CO2 accumulation and therefore higher than arterial Ptcco2 values.

Animals↗
PubMed1980

Technical aspects in the management of the meconium aspiration syndrome with extracorporeal circulation.

Sixteen neonatal patients diagnosed as having the meconium aspiration syndrome were selected for management with extracorporeal circulation with a membrane oxygenator (ECMO) with 8 survivors over 4 yr. All patients weighed greater than 2 kg. Each was placed in the 100% mortality group according to a Neonatal Pulmonary Insufficiency Index (NPII) based on hourly pH and FiO2 determinations. The typical patient course on ECMO was stabilization for the first 12 hr then improvement on high bypass flow rates for 12-24 hr to maintain a pAO2 for 50-60 mm Hg with minimal ventilator settings with an FiO2 of 0.3-0.4. Bypass flow rates were reduced to maintain adequate pAO2 with similar ventilator settings for another 24 hr. Survivors were taken off bypass and decannulated while on similar ventilator settings. Nonsurvivors did stabilize or improve but usually exhibited symptoms of intracranial hemorrhage by 48 hr. Intracranial hemorrhage appeared to be related to the degree of prebypass acidosis. Successful ECMO support reduced the expected mortality from severe meconium aspiration from 100% to 50%. Early institution of ECMO, before acidosis worsens, seems to be indicated to reduce the morbidity of conventional ventilator management and to prevent intracranial hemorrhage from severe prebypass acidosis. Long term followup indicates that these patients have progressed satisfactorily according to developmental testing for as long as 4 yr.

Catheterization↗
PubMed1979

Prospective application of an index of neonatal necrotizing enterocolitis.

Fifty-five patients were scored 1 to 3 according to the criteria: the character of stools, abdominal findings on palpation, x-ray evidence of pneumatosis intestinalis, the development of pulmonary insufficiency, and the duration of symptoms to positive x-rays. Fifteen patients with scores of less than five were considered to have subclinical NEC with one late death. Twenty-nine of 30 patients with scores of 5-10 responded to medical management with 2 deaths related to recurrent bouts of sepsis without recurrent NEC. Eleven patients required surgery with index scores of 10-14 with 6 deaths occurring uniformly in those patients with scores of 12 or more. Two patients were scored inappropriately low due to the lack of the passage of a stool for analysis. One patient with a score of 4 did not pass a stool but had the other diagnostic criteria for the single false negative of the series. This index correctly determined the severity of NEC of 53 of 55 patients, identified the patients who required surgical intervention and predicted survival.

Enterocolitis, Pseudomembranous↗
PubMed1979

In vivo evaluation of monopolar intravascular PO2 electrodes.

Ten intravascular electrodes were evaluated on ten rabbits. The mean stabilized time of 118 +/- 52 min was excessively long for clinical use. The in vitro cal factor was not reproducible nor accurate. The differences between the PO2 values measured by the electrode and those obtained from intermittent blood samples were within +/- 10 mm Hg during the first 12 hr using the in vivo calibration after electrode stabilization. After 12 hr, the electrode PO2 values using the in vitro cal factor or based upon the in vivo calibration were increased significantly indicating a possible membrane rupture. This occured more rapidly in the animal experiments than in the in vitro studies using a tonometer, suggesting that continuous flow and pressure changes inside of the aorta contribute greatly to mechanical breakage of the membrane. Histologic evaluation indicated the electrode catheter system was thrombogenic at the level of the electrode tip and this thrombogenicity was primarily related to intimal injury caused by the electrode tip movement as a result of flow and pressure changes inside the aorta.

Animals↗
PubMed1979

Transcutaneous PO2 monitoring of flap circulation following surgery.

In a series of rabbit experiments, tcPO2 was found to be a very sensitive indicator of flap viability, reflecting minute-to-minute changes in physiology. It is safe, reproducible, and easily verified by comparing flap tcPO2 to a control site and by measuring response to increased FIO2. Transcutaneous PO2 measurements should prove a valuable tool in flap research and in monitoring pedicle flaps and microvascular tissue transfers.

Animals↗
PubMed1978

Low impedance pH sensitive electrochemical devices that are potentially applicable to transcutaneous PCO2 measurements.

Two cases of low impedance, non-glass membrane electrodes for pH measurement were evaluated: (I) Metal--metal oxide electrodes and (II) Reduction-oxidation electrodes. The fundamental cause of oxygen sensitivity of metal-metal oxide electrodes were examined and three approaches for its suppression were proposed. For the case of Sb--Sb2Ox electordes, oxygen sensitivity can be attenuated partially by cell loading, either directly across the reference electrode or indirectly across a third slave electrode. In a PO2 range of 8--54 kPa, more than 95% of the PO2 response can be suppressed by loading the cell emf to half of tis open-circuit value. The oxygen sensitivity also was observed to diminished by grinding the metal-metal oxide and pressing it under high pressure into a pellet electrode. Other metal-metal oxide electrodes that have promise in transcutaneous measurement are the Pd-PdO2 electrodes. The redox electrodes are typified by the Quinhydrone electrode. A membrane Quinhydrome electrode showed a sensitivity of 56 mV/Decade at 37 degree C and no oxygen sensitivity up to 50 kPa and a drift of 1 mV/h over a 24-h period. However, the stability deteriorated over a long-term period.

Blood Gas Analysis↗
PubMed1977

Management of pulmonary insufficiency in diaphragmatic hernia using extracorporeal circulation with a membrane oxygenator (ECMO).

Persistent fetal circulation (PFC) causes severe pulmonary insufficiency in patients who have demonstrated adequate lung function following diaphragmatic hernia repair. Patent ductus arteriosus (PDA) ligation corrects this condition, but carries the risk of sudden right ventricular failure. Pharmacologic reversal of PFC may be attempted, and if unsuccessful, prolonged venoarterial bypass becomes necessary to provide effective pulmonary support. PDA ligation can then be performed safely and maturation of the pulmonary vasculature allowed to occur. Pulmonary artery pressure monitoring is essential.

Ductus Arteriosus, Patent↗