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Biomedical subjects

P Vanderhoeft

Publications and source records attributed to P Vanderhoeft.

At least 19 recordsLinked to original sources
PubMed1995

Starling resistor vs. distensible vessel models for embolic pulmonary hypertension.

We investigated whether the Starling resistor model (Mitzner et al. J. Appl. Physiol. 51: 1065-1071, 1981) or a distensible vessel model (Haworth et al. J. Appl. Physiol. 70: 15-26, 1991) best describes pulmonary vascular pressure-flow (Q) relationships in embolic pulmonary hypertension. Mean pulmonary arterial pressure (Ppa)-Q plots at constant left atrial pressure (Pla) and Ppa-Pla plots at constant Q were investigated in seven dogs before and after 500-micron glass bead pulmonary embolism. Embolization to a mean angiographic obstruction of 78% increased the slope and extrapolated pressure intercept (P(i)) of Ppa-Q plots and increased the inflection point of Ppa-Pla plots, above which an increase in Pla is transmitted to Ppa in a ratio of approximately 1:1. The Starling resistor and the distensible vessel model provided a reasonably good fit to the Ppa-Q and Ppa-Pla coordinates before and after embolism. However, contrary to the prediction of the Starling resistor model, no correlation was found between the inflection point of Ppa-Pla plots and P(i). We therefore conclude that an increased closing pressure is unlikely to contribute to embolic pulmonary hypertension.

Animals↗
PubMed1994

[Aspects of pathological physiology of the dog in extracorporeal circulation].

During ECC, dogs ventilate spontaneously according to classical physiology. Further, given the CO2 clearance insured by the ECC oxygenator, many hours of reversible apnea are tolerated without sequellae. Surgical removal of the lungs shows that an emptied chest still responds to chemical drives, but the absent lung-recoil causes hyperinflation with lethal failure. Finally, liquid ventilation induces metabolic acidemia through phasic gut ischemia and respiratory muscle strain that destroys the delicate lung structure.

Acidosis↗
PubMed1990

Effort rupture of the diaphragm.

Effort rupture of the diaphragm is rare and accounts for only 1% of all diaphragmatic injuries. A 23 year old patient with bilateral rupture that followed sudden movement is described.

Adult↗
PubMed1990

Effects of embolus size on hemodynamics and gas exchange in canine embolic pulmonary hypertension.

We examined the effects of different-sized glass-bead embolization on pulmonary hemodynamics and gas exchange in 12 intact anesthetized dogs. Pulmonary hemodynamics were evaluated by multipoint pulmonary arterial pressure (Ppa)/cardiac output (Q) plots before and 60 min after sufficient amounts of 100-microns (n = 6 dogs) or 1,000-microns (n = 6 dogs) glass beads to triple baseline Ppa were given and again 20 min after 5 mg/kg hydralazine in all the animals. Gas exchange was assessed using the multiple inert gas elimination technique in each of these experimental conditions. Embolization increased both the extrapolated pressure intercepts (by 6 mmHg) and the slopes (by 5 mmHg.l-1.min.m2) of the linear Ppa/Q plots, together with an 80% angiographic pulmonary vascular obstruction. These changes were not significantly different in the two subgroups of dogs. However, arterial PO2 was most decreased after the 100-microns beads, and arterial PCO2 was most increased after the 1,000-microns beads. Both bead sizes deteriorated the distribution of ventilation (VA)/perfusion (Q) ratios, with development of lung units with higher as well as with lower than normal VA/Q. Only 100-microns beads generated a shunt. Only 1,000-microns beads generated a high VA/Q mode and increased inert gas dead space. Hydralazine increased the shunt and decreased the slope of the Ppa/Q plots after 100-microns beads and had no effect after 1,000-microns beads. We conclude that in embolic pulmonary hypertension, Ppa/Q characteristics are unaffected by embolus size up to 1,000 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Penetration of aminoglycosides in uninfected pleural exudates and in pleural empyemas.

The concentrations of gentamicin, netilmicin, and amikacin were determined after one single intravenous injection in uninfected pleural fluid after thoracotomy and in purulent pleural empyemas. The mean peak concentrations in the pleural fluid after the injection of gentamicin (1.5 mg/kg), netilmicin (2.0 mg/kg), and amikacin (7.5 mg/kg) were 2.9 +/- 0.3 mg/L, 3.7 +/- 0.8 mg/L, and 11.0 +/- 3.1 mg/L, respectively. The pleural penetration of the drugs was very high (from 80.0 to 99.1 percent). By contrast, gentamicin and netilmicin were not detectable in empyema pus; in this exudate the mean peak level of amikacin was 5.7 +/- 2.2 mg/L, with the penetration of this drug being 31.0 percent. The concentrations of parenterally administered aminoglycosides are substantially lower in empyema pus than in sterile pleural fluid. The possibility of poor pleural penetration of some aminoglycosides, as well as the presence of local conditions in pleural empyema unfavorable to the bioactivity of these drugs, must be kept in mind when treating pleural infections.

Amikacin↗
PubMed1985

Hypophosphatemia after cardiothoracic surgery.

The incidence of hypophosphatemia during the first 48 h following cardiothoracic surgery was prospectively studied in 74 patients. Hypophosphatemia, defined by a serum phosphate below 2.50 mg/dl, was observed in 19 of 34 (56%) patients after thoracic surgery and in 20 of 40 (50%) patients after cardiac surgery. As a whole, hypophosphatemia occurred earlier after thoracic than after cardiac surgery. After thoracic surgery, hypophosphatemia was milder for patients in whom bleeding was more severe. The anticoagulant solution CPD used in stored blood was identified as an important source of phosphate. These results indicate hypophosphatemia is a common finding after cardiothoracic surgery. Since severe hypophosphatemia can be related to phosphate depletion, phosphate supplements could be warranted especially during thoracic surgery when blood transfusions are less than 1000 ml.

Adult↗
PubMed1982

Phrenic nerve function after pneumonectomy.

Using surface electrodes over the lower chest wall, we measured the phrenic nerve conduction time, ie, the time interval between the stimulation of the phrenic nerve in the neck and the onset of the diaphragmatic muscle action potential, in ten patients who had undergone pneumonectomy several years before (mean, eight years) and in 31 control subjects (bilaterally in 19 of them). The mean (+/- SD) value in the control subjects was 7.0 (+/- 0.9) msec, and no value exceeded 10 msec. All the values obtained in the patients were within the control range. We concluded that phrenic nerve function remains normal after pneumonectomy. This method appears to be the most effective means of identifying phrenic nerve involvement in these patients.

Adult↗
PubMed1981

Functional evaluation of tracheal stenosis before and after surgical management.

14 patients affected by tracheal stenosis resulting from assisted ventilation underwent a tracheal resection (n = 12) or dilatation (n = 2). Lung function tests were performed before and after surgical treatment. Prior to surgery, we observed a significant increase in airway resistance (Raw) in all subjects and a negative exponential relationship between Raw and FEV1/VC. Expiratory flows were also reduced with an increase in FEV1/PEFR ratios. After surgical correction of the stenosis, Raw normalized in 10 out of 14 subjects. The observed changes were more significant than for the other functional tests. After surgery, the patient's follow-up with Raw allowed the diagnosis of recurrent stenosis in 4 subjects lacking significant clinical symptoms. We conclude that measurement of Raw helps the clinical diagnosis and the appreciation of the possible changes in airway permeability after the surgical procedure.

Forced Expiratory Volume↗