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Biomedical subjects

H Pontoppidan

Publications and source records attributed to H Pontoppidan.

At least 19 recordsLinked to original sources
PubMed1992

Direct dye binding--a quantitative assay for solid-phase immobilized protein.

A direct dye-binding procedure was established for the quantification of protein after its immobilization on a solid phase, using IgG and BSA as model proteins. The assay, which in the range 0-5 mg protein/ml gel correlates well with indirect protein determination by A280 as well as determination of protein hydrolyzed from the gel, is based on a modified Bradford dye-binding assay. As the protein coupled to the gel binds the dye, a decrease in A465 of the supernatant is measured. Three solid supports commonly used for protein immobilization (Sepharose, Sephadex, Sephacryl) were found to be compatible with the dye-binding assay while nonspecific dye binding was found to HEMA gels. Protein was coupled to Sephacryl S-1000 using three different activation methods (aldehyde, hydrazine, and adipic acid dihydrazide). Artifactual dye-binding was not observed using any of the three different "linkers." The assay is easily carried out and represents a useful tool, e.g., when optimizing procedures for protein immobilization.

Coloring Agents↗
PubMed1986

A prospective study of acute hypoxic respiratory failure.

A prospective study of acute hypoxic respiratory failure was carried out by nine centers in a collaborative NIH study from 1 September 1975 to 1 March 1977. Serious hypoxic respiratory failure was defined in 713 patients by the presence of (1) endotracheal intubation and positive airway pressure for at least 24 hours, and (2) the administration of at least 50 percent oxygen. The 490 patients between 12 to 65 years of age had a mortality of 61 percent. Mortality increased with increasing organ failure: one organ system failure (lung only) 40 percent; two, 54 percent; three, 72 percent; four, 84 percent, five, 100 percent. Only 103 patients died with isolated lung failure, whereas 353 died of a combination of lung and other organ failures. Both the overall mortality (66 percent) and the mortality of those with only isolated lung failure (40 percent) were much higher than anticipated for the selection criteria.

Acute Disease↗
PubMed1985

Effect of prethymectomy plasma exchange on postoperative respiratory function in myasthenia gravis.

The effect of prethymectomy plasma exchange on postoperative mechanical ventilation requirement and length of stay in the intensive care unit were studied retrospectively in 37 patients with myasthenia gravis. We found a significantly decreased time on mechanical ventilation (mean 1.02 +/- 0.40 versus 3.43 +/- 0.60 days) and a shorter stay in the intensive care unit (mean 3.09 +/- 0.99 versus 5.15 +/- 0.66 days) for 11 patients with respiratory weakness who were treated with preoperative plasma exchange compared with 26 patients who did not receive plasma exchange. Patients with respiratory weakness who received prethymectomy plasma exchange required less time on mechanical ventilation (mean 1.02 +/- 0.40 versus 2.73 +/- 0.88 days) and a shorter stay in the intensive care unit (mean 3.09 +/- 0.99 versus 4.46 +/- 1.08 days) than those patients without respiratory weakness who did not receive plasma exchange. Eleven patients met the criteria for plasma exchange but did not receive it. They required significantly more time on mechanical ventilation (mean 4.43 +/- 0.94 versus 1.02 +/- 0.40 days) and in the intensive care unit (mean 6.09 +/- 0.86 versus 3.09 +/- 0.99 days) than patients who received plasma exchange. Our results indicate that patients with severe forms of myasthenia gravis treated with prethymectomy plasma exchange require less mechanical ventilation and less time in the intensive care unit postoperatively.

Adolescent↗
PubMed1982

Pulmonary vascular remodeling in adult respiratory distress syndrome.

To analyze microvascular changes, angiograms and microscopic sections of the lung were prepared from 12 patients dying after severe adult respiratory distress syndrome (ARDS) of diverse cause. Anatomic features of the precapillary arterial bed were morphometrically assessed and related to the duration of acute lung injury. In intra-acinar arteries, medial thickness was increased after short duration ARDS (less than 12 days). Preacinar arteries developed medial thickening only after ARDS of long duration (18-60 days). Mean external diameter (ED) of partially muscular intra-acinar arteries was less than normal in both duration groups, whereas ED of muscular arteries was less in the long duration group. Concentrations of partially and fully muscular arteries tended to be higher in ARDS lungs. These results give evidence of an extension of smooth muscle into normally nonmuscular, smaller pulmonary arteries. Total artery concentration in 7 of the 12 patients was less than the normal, and dilatation of intra-acinar muscular arteries was often observed. The ARDS is characterized by partial or complete disruption and even disappearance of much of the pulmonary vascular bed.

Adult↗
PubMed1982

Comparison of work of breathing on high gas flow and demand valve continuous positive airway pressure systems.

Using on-line computer analysis, the work of breathing (WOB) was measured in ten normal subjects breathing through four continuous positive airway pressure (CPAP) circuits. Two systems (Emerson ventilator) and MGH elastic loaded reservoir bag (ELRB) were high continuous flow systems and two (Puritan-Bennett MA-2 and Bourns Bear Ventilators) were demand valve circuits. Mean values for the WOB were similar with either of the two continuous high flow systems (Emerson 0.41 +/- .21 kg . m . L-1; ERLB 0.49 +/- .29 kg . m . min-1) and significantly lower than with the two demand valve systems (MA-2 0.89 +/- .40 kg . m . min-1; Bourns .71 +/- .30 kg . m . min-1).

Computers↗
PubMed1980

Mechanical aids to lung expansion in non-intubated surgical patients.

The reported incidence of postoperative pulmonary complications (PPC) varies markedly with the extent and type of surgery; for many types of major surgery, such as intracranial operations, data are unavailable. After upper abdominal surgery, the incidence ranges from 6 to 70%, depending on the diagnostic criteria used for detection and the physical status of the patients. Thus, the potential for serious PPC after major surgery is so great that some form of preventive respiratory care is mandatory. The most efficient methods remain to be determined. Mechanical aids to lung expansion have received widespread use. Unfortunately, few randomized, controlled trials have been reported, and results are difficult to compare because of important differences in protocol, specific details of therapy, and statistical methods used. We conclude the following: (1) There is little or no evidence documenting the efficacy of intermittent positive-pressure breathing (as customarily used) or blow bottles in decreasing the incidence of PPC. (2) Incentive spirometry may be of value in patients receiving routine "stir-up" regimen (turning, coughing, walking) by surgical housestaff and nurses, but does not appear to decrease further the incidence of PPC in patients treated with systematic preoperative regimens of chest physical therapy. (3) Data on the use of positive end-expiratory pressure and continuous positive airway pressure by face mask are to sparse to permit drawing definite conclusions concerning their efficacy. (4) Incentive spirometry and continuous positive airway pressure by mask are both based on sound physiologic rational and warrant further studies to determine their role in postoperative respiratory care.

Humans↗
PubMed1975

Hemodynamic responses to mechanical ventilation with PEEP: the effect of hypervolemia.

The hemodynamic effects of prolonged mechanical ventilation with positive end-expiratory pressure (PEEP), with and without blood volume augmentation, were studied in 18 beagles anesthetized with halothane (0.7 per cent end-tidal). Addition of 12 cm H2O PEEP during mechanical ventilation in normavolemic dogs was associated with reductions of transmural cardiac filling pressures, cardiac index and stroke index to 50 per cent of control values. Circulatory adaptation did not occur. Filling pressures and flow remained unchanged during the ensuing 8 hours when PEEP was maintained. They returned to control levels when PEEP was discontinued, except for the transmural right ventricular end-diastolic pressure, which remained elevated above control levels. Systemic vascular resistance was unchanged, but pulmonary vascular resistance doubled upon addition of PEEP. Following autologous whole blood transfusion (25 ml/kg) during mechanical ventilation with PEEP, cardiac index returned to, and remained at, control levels. After PEEP was discontinued, cardiac index increased acutely and remained elevated for the remainder of the study period (as long as 7 hours). Comparable transfusion during mechanical ventilation without PEEP elevated cardiac index only transiently. Right atrial, pulmonary capillary wedge, and right and left ventricular end-diastolic pressures showed marked increases relative to atmospheric with PEEP and after transfusion. Calculated transmural pressures demonstrated clear reductions with application of PEEP, followed by increases to control levels with transfusion and further increases to above control when PEEP was discontinued. Study of ventricular function curves revealed that changes in filling pressures and not to changes in ventricular contractility. Transmural pulmonary arterial diastolic pressure rose throughout the 12 hours of study, despite return of pulmonary vascular resistance to control level with removal of PEEP. Thus, acute decreases in cardiac filling pressure, cardiac index, and stroke index persist consequent to application of PEEP, and circulatory adaptation does not occur. The apparent hemodynamic deterioration may be reversed by blood volume augmentation, but when PEEP is discontinued, hypervolemia with consequent increases in filling pressures and a move along a ventricular function curve will occur. Changes in cardiac index will depend upon the overall state of right and left ventricular contractility.

Animals↗
PubMed1975

Extracorporeal perfusion for acute respiratory failure: recent experience with the spiral coil membrane lung.

Selection criteria, clinical data, and physiological measurements obtained during five extracorporeal membrane lung perfusions for acute respiratory insufficiency are presented. Four patients died and 1 survived. A new technique of femoral artery cannulation to allow aortic arch perfusion is described. When properly monitored, this route provides improved oxygen delivery to the brain during venoarterial (VA) perfusion. The importance of monitoring the equivalent of carotid artery Po2 during VA perfusion is emphasized. Recognition of the effects of high cardiac output in limiting the quality of extracorporeal perfusion, plus the use of hypothermia to reduce output, are stressed. We have confirmed that perfusion can be accomplished with small quantities of heparin, so that bleeding is reduced, but thrombocytopenia and occasional hemorrhage continue to be persistent problems.

Acute Disease↗
PubMed1972

Ventilation with end-expiratory pressure in acute lung disease.

In 10 patients with severe, acute respiratory failure we studied the effects of positive end-expiratory pressure when intermittent positive pressure ventilation (IPPV) with inspired oxygen (F(IO2)) up to 0.5 failed to maintain arterial oxygen tension (P(aO2)) above 70 torr.Positive end-expiratory pressures (PEEP) of 0, 5, 10, and 15 cm H(2)O were applied for 30-min periods each and in random order. Blood gas exchange, lung volumes, compliance, and hemodynamics were studied at each level of PEEP. P(aO2) (F(IO2) = 1.0) rose linearly with elevation of PEEP, the mean increase being from 152 to 347 torr, or 13 torr/cm H(2)O PEEP. Mean functional residual capacity (FRC) was 1.48+/-0.78 liters at zero PEEP (i.e., IPPV) and the increase was essentially linear, reaching 2.37 liters at 15 cm H(2)O PEEP. P(aO2) and FRC showed a close correlation. Total and lung static compliance were greater during ventilation with high than with low levels of PEEP. The increase in P(aO2) correlated with the specific lung compliance. Dynamic lung compliance decreased progressively with rising levels of PEEP except for an increase with 5 and 10 cm H(2)O PEEP in patients with initial values of 0.06 liter/cm H(2)O or higher. Cardiac index fell in some patients and rose in others and there was no correlation of mean cardiac index, systemic blood pressure, or peripheral vascular resistance with level of PEEP. The most probable explanation for the effect of PEEP on P(aO2) and compliance is recruitment of gas exchange airspaces and prevention of terminal airway closure.

Acute Disease↗