Search PubMed⌕ Search

Biomedical subjects

T N Hansen

Publications and source records attributed to T N Hansen.

72 records · Page 4Linked to original sources
PubMed1984

Lung fluid balance in hypoxic lambs.

In spontaneously breathing newborn lambs, alveolar hypoxia increases lung microvascular pressure, which causes lung lymph flow to increase and the concentration of protein in lymph to decrease. To see if this response derives from hypoxia itself rather than from the change in breathing pattern that occurs during hypoxia, we measured lung vascular pressures, pleural pressure, cardiac output, and lung lymph flow in 12 anesthetized lambs that were ventilated at a fixed rate and tidal volume, first with air, then with 10-14% O2 in nitrogen. Alveolar hypoxia did not affect pleural pressure, but pulmonary arterial pressure increased from 19 to 32 torr, lung lymph flow increased from 2.20 to 3.83 ml/h and lymph protein concentration decreased from 3.4 to 2.8 g/dl. To be certain that the increased lymph flow associated with hypoxia is not simply the result of an acute release of fluid from the lungs and to assess the effects of carbon dioxide on lymph flow during hypoxia, we next studied six unanesthetized lambs kept hypoxic for a total of 12 h. After a 2-4-h period in air the lambs breathed 9-11% O2 in nitrogen for 2-4 h, then 8-11% O2 and 3-5% CO2 in nitrogen for 8-10 h. In these lambs we injected intravenously radioactive albumin and measured its uptake in lymph to see if sustained hypoxia alters microvascular permeability to protein in the lungs. In these experiments pulmonary arterial pressure increased from 17 to 37 torr, lung lymph flow increased from 1.74 to 3.28 ml/h, and lymph protein concentration decreased from 3.8 to 3.1 g/dl during hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Contagious ecthyma in lambs and laboratory personnel.

Contagious ecthyma, diagnosed in three lambs, was transmitted to two researchers having direct contact with oral secretions from these lambs. Intracytoplasmic viral particles were demonstrated by electron microscopy in gingival biopsies from one lamb. Lamb to lamb transmission was most likely caused by use of a contaminated gavage feeding tube. Concern for the effects of this disease and Q fever on patients having contact with contaminated medical researchers prompted the formulation of safety guidelines to prevent potentially disastrous zoonotic disease.

Animals↗
PubMed1982

Lung fluid balance in lambs before and after birth.

To study lung fluid balance before and after birth, we measured lung lymph flow and concentrations of protein in lymph and plasma of 22 unanesthetized fetal lambs and compared results with previous studies done on 26 newborn lambs, 1-2 wk old. Lymph flow, relative to lung mass, was less in fetuses than in newborns; lymph protein clearance was not significantly different. Less lymph flow before birth probably reflects less available surface area for fluid exchange in microcirculation of fetal lungs, compared with newborn lungs, with no difference in endothelial permeability to protein. Extravascular lung water, measured gravimetrically for 24 fetuses (10 without labor, nine in labor, five 6 h after vaginal birth), decreased by 45% (15 +/- 2 g/kg body wt) before birth and by an additional 38% (6 +/- 1 g/kg) after birth. In five lambs killed after birth, we measured lung lymph flow before and during labor and for 6 h after breathing began. Lymph flow was unaffected by labor but increased transiently after birth, accounting for 11% of the liquid removed from lungs postnatally. Liquid clearance studies performed in eight anesthetized 3-wk-old lambs confirmed the observation that lung lymphatics drain only a small fraction of liquid in potential air spaces. Most of that liquid probably leaves the lungs directly through pulmonary circulation.

Animals↗
PubMed1981

Effect of oxygen administration during sleep on skin surface oxygen and carbon dioxide tensions in patients with chronic lung disease.

Hypoxemia, hypercarbia, and cor pulmonale ultimately occur in most patients with chronic lung disease. Although oxygen therapy may reduce or delay the development of pulmonary hypertension and myocardial failure in these patients, its use is thought to lead to CO2 narcosis and apnea. The effect of O2 administration during sleep has been examined in 12 patients (seven with cystic fibrosis, three with bronchopulmonary dysplasia, one with bronchiolitis obliterans, and one with severe hypersensitivity pneumonitis) using skin surface O2 (Roche) and CO2 (Radiometer) electrodes. Both electrodes were calibrated over wet gas and applied at 44 C. Ten patients had chronic hypercarbia (PaCO2 62 +/- 19 torr; range 46 to 103 torr) when awake. Humidified oxygen was administered by nasal cannula, Venturi mask, or head hood. Oxygen flow was increased every 20 minutes from 80 minutes or until the patient awoke. In eight of ten patients with hypercarbia and in the two normocarbic patients, skin surface carbon dioxide tension (PsCO2) increased by 10% or less as the skin surface oxygen tension (PsO2) was increased. In the remaining two patients with hypercarbia (both had cystic fibrosis) PsCO2 increased 18% and 24% as PsO2 was increased. These last two patients with depressed responsiveness to CO2 could not be separated from the other patients by clinical or laboratory criteria. It is concluded that the skin surface blood gas tensions are a simple and reproducible method for adjusting oxygen therapy in patients with chronic lung disease, and although the response to oxygen varies from patient to patient, most patients with chronic hypercarbia retain their central responsiveness to CO2 during sleep and for them O2 therapy is probably safe.

Adolescent↗
PubMed1980

Transfer of oxygen, nitrogen, and carbon dioxide through normal adult human skin.

The resistance to the flow of oxygen, nitrogen, and carbon dioxide through the skin ws measured in three normal adult human subjects. A sampling chamber 2.5 cm in diameter, heated to 43-44 degrees C, was applied to the skin of the forearm and gas sampled with a mass spectrometer at a rate of about 10(-5) ml . s-1 through membranes of different resistance. Skin resistance was calculated from the results of sequential studies with different membranes of known resistance on the sampling chamber. The resistance to oxygen flow (1.79 +/- 0.92 X 10(3) atm . ml-1 . min . cm2) was 1/5 of that for nitrogen and 28.5 times that for carbon dioxide. The response time of the skin to a sudden change in arterial gas tension was investigated by having the subjects rebreathe 5% carbon dioxide in oxygen and then breathe air. The mean transit times though the skin for oxygen and carbon dioxide were similar (approx 30 s) and about twice those for nitrogen. The finding of similar response times for oxygen and carbon dioxide transfer in the face of large differences in resistance suggests that there is a high capacitance for carbon dioxide in the skin, presumably due to its high solubility and the effects of buffering.

Carbon Dioxide↗
PubMed1980

Lung fluid balance in hypoxic, awake newborn lambs and mature sheep.

To study the pulmonary vascular response to hypoxia and associated transvascular flow of fluid into the lungs of newborn lambs and mature sheep, we collected lung lymph and measured pulmonary vascular pressures and blood flow in 14 unanesthetized lambs and 9 sheep breathing 10-12% oxygen for 3-6 h after a 2-hour control period in air. In both groups of animals, pulmonary arterial pressure, blood flow, and lung vascular resistance increased with hypoxia, but only in lambs did the flow of lymph increase and th concentration of protein in lymph decrease with hypoxia. These results suggest that hypoxia increased transvascular filtration of fluid into the lungs of the lambs by increasing hydraulic pressure in the pulmonary microcirculation. In sheep, the vascular response to hypoxia did not increase lung fluid filtration. Hypoxia had no effect on microvascular permeability to protein in the lungs of either group of animals.

Age Factors↗
PubMed1980

Continuous measurements of skin surface oxygen and carbon dioxide tensions in obstructive sleep apnea.

We have found that skin surface electrodes for continuously measuring oxygen (PSO2) and carbon dioxide (PSCO2) tensions provide reliable means of determining whether infants with apnea due to airway obstruction during sleep require treatment. Nine patients referred for evaluation of aqnea during sleep were studied. In 6 patients with PSO2 less than 50 torr during sleep, the hypoxic episodes were clearly associated with partial or total airway occlusion as judged by increasing respiratory effort without concomitant airflow. PSCO2 was found to increase during the episodes of obstruction in all 6 patients. These patients were treated with 1. tracheotomy, 2. tonsillectomy and adenoidectomy in 2 patients, 3. bilateral mandibular condylotomies, 4. pharyngeal flap release, and 5. discontinuing topical nasal decongestants. After treatment, all had decreased hypoxia, hypercarbia, or airway obstruction. Two of the remaining 3 patients had no alterations of PSO2 or PSCO2 associated with airway obstruction during sleep. The third exhibited hypoxia and hypercarbia secondary to central apnea. We conclude, therefore, that continuous monitoring of skin surface oxygen and carbon dioxide tensions is useful in evaluating children with obstructive sleep apnea.

Airway Obstruction↗
PubMed1979

Skin surface carbon dioxide tension in sick infants.

Skin surface PCO2 (PSCO2) was measured at 44 C in 17 sick infants using a Radiometer surface PCO2 electrode. Values obtained for PSCO2 were compared with simultaneous values for arterial PCO2 (PaCO2). PSCO2 was found to be linerarly related to PaCO2 by a regression line with a slope 1.37. PaCO2 could be predicted from PSCO2 to within 6 torr in all instances. The relationship was not affected by the patient's gestational age, postnatal age, weight, or blood pressure. This electrode is a valuable clinical tool in the management of sick infants.

Arteries↗
PubMed1977

Renal tubular abnormalities in a patient with the phenotypic appearance of C-trisomy mosaicism.

In 1971, SINHA et al. described a patient with isochromosomes arising from a C-group autosome. This patient had the phenotypic appearance of C-trisomy mosaicism. Six years later she presented with complaints of polydipsia and polyuria and was documented to have nephrogenic diabetes insipidus and renal tubular acidosis. The abnormal cell line of the patient had disappeared at the time of this observation.

Acidosis, Renal Tubular↗
PubMedDate not supplied

Prediction of brain blood flow using pulsed Doppler ultrasonography in newborn lambs.

The purpose of this study was to evaluate the ability of pulsed Doppler ultrasonography to predict brain blood flow by comparing measurements made in basal cerebral arteries using a pulsed Doppler system with measurements of brain blood flow using radioactive microspheres in lambs. We measured the instantaneous maximum velocity during peak systole and end diastole and the mean velocity over the pulse cycle in basal cerebral arteries, calculated Pourcelot's index of resistance and Gosling's pulsatility index, and used regression analysis to compare the pulsed Doppler measurements with brain blood flow measured with radioactive microspheres. Pulsed Doppler measurements of the peak systolic, end diastolic, and mean flow velocity in basal cerebral arteries were directly related to brain blood flow. In contrast, no linear relationship was detected between the resistance or pulsatility indices and brain blood flow measured by microspheres (p greater than 0.14). Prediction of brain blood flow for individual subjects lacks the quantitative precision necessary for use as a clinical tool. However, the direct relationship between brain blood flow and the peak systolic, end diastolic, and mean flow velocities in basal cerebral arteries supports the use of these measurements in clinical research for the qualitative assessment of change in brain blood flow.

Animals↗
PubMedDate not supplied

Endotracheal continuous positive airway pressure after rescue surfactant therapy.

OBJECTIVE: To determine if premature infants greater than 31 weeks of gestation with established hyaline membrane disease (HMD) can be treated with endotracheal continuous positive airway pressure (ETCPAP) after rescue surfactant replacement therapy. STUDY DESIGN: Retrospective study of 46 premature infants (>31 weeks of gestation) admitted to Texas Children's Hospital with HMD. Tolerance to ETCPAP after surfactant replacement was evaluated. Prenatal and postnatal characteristics and outcome were compared in the success and failure groups. Multiple logistic regression was used to determine predictive factors associated with failure. RESULTS: Thirty infants (65.2%) were successfully treated with rescue surfactant and ETCPAP. Cesarean section, higher 1-minute Apgar score, and higher FiO2 level at entry were independent predictors of failure to remain on CPAP due to hypoxemia (56.3%), hypercapnia (31.2%), and apnea (12.5%). In the success group duration of intubation (p < 0.001), oxygen administration (p < 0.01), >40% oxygen requirement (p < 0.001), hospital stay (p < 0.05), and respiratory support on day 7 (p < 0.001) were significantly favorable. CONCLUSION: Two thirds of infants greater than 31 weeks of gestation, with HMD needing rescue surfactant treatment, can be successfully managed with ETCPAP.

Combined Modality Therapy↗