Biomedical subjects

P Vock

Publications and source records attributed to P Vock.

At least 19 recordsLinked to original sources

PubMed1992

[Pathophysiology, prevention and therapy of altitude pulmonary edema].

Alveolar hypoxia and resulting tissue hypoxia initiates the pathophysiological sequence of high altitude pulmonary edema (HAPE). Very rapid ascent to high altitude without prior acclimatization results in HAPE, even in subjects with excellent tolerance to high altitude. Upon acute altitude exposure, HAPE-susceptible individuals react with increased secretion of norepinephrine, epinephrine, renin, angiotensin, aldosterone and atrial natriuretic peptide. In response to exercise at high altitude, subjects developing acute mountain sickness and HAPE secrete more aldosterone and antidiuretic hormone than subjects who remain well. This results in sodium and water retention, reduction of urine output, increase in body weight and development of peripheral edemas. The hypoxic pulmonary vascular response is enhanced in HAPE-susceptible subjects, thus favouring the development of severe pulmonary hypertension on exposure to high altitude. It has been postulated that uneven pulmonary vasoconstriction enhances filtration pressure in non-vasoconstricted lung areas, leading to interstitial and alveolar edema. The high protein content of the edema fluid in HAPE characterizes this edema as a permeability edema. The prophylactic administration of nifedipine prevents the exaggerated pulmonary hypertension of HAPE-susceptible subjects upon rapid ascent to 4559 m and thus prevents HAPE in most cases. This finding illustrates the crucial role of hypoxic pulmonary hypertension in the development of HAPE. The causal treatment of HAPE is descent, evacuation and administration of oxygen. Treatment of HAPE patients with nifedipine results in a reduction of pulmonary artery pressure, clinical improvement, increased oxygenation, decrease of the alveolar arterial oxygen gradient and progressive clearing of pulmonary edema on chest x-ray. Thus nifedipine offers a pharmacological tool for the treatment of HAPE.

Aldosterone↗

PubMed1992

Alterations in hepatic fructose metabolism in cirrhotic patients demonstrated by dynamic 31phosphorus spectroscopy.

Quantitative liver function tests are based on the clearance concept and measure the plasma disappearance of a test compound such as galactose. Metabolism is inferred to be predominantly hepatic, and usually no knowledge is obtained of the true time course of metabolite formation. Dynamic 31phosphorus magnetic resonance spectroscopy after intravenous administration of fructose directly measures hepatic sugar metabolism. To determine the feasibility and the utility of 31P magnetic resonance spectroscopy, we studied the responses of six healthy subjects and nine patients with nonalcoholic cirrhosis to a fructose load. Results were related to the impairment of hepatic function assessed by the galactose-elimination capacity test. Liver spectra were acquired in a 1.5 T whole-body nuclear magnetic resonance unit with a surface coil (9-cm diameter) placed ventrally on the liver; the one-dimensional chemical-shift imaging technique was used to obtain spectra from tissue slices parallel to the surface coil. After a basal spectrum had been obtained, fructose (250 mg/kg) was injected intravenously, and further spectra were collected sequentially every 6 min for 1 hr. Formation of monophosphate esters (9% +/- 5% vs. 20% +/- 8% of total area; p less than 0.01) and utilization of inorganic phosphate (5% +/- 4% vs. 11% +/- 3% of total area; p less than 0.005) were markedly decreased in cirrhotic patients. These measures correlated with the severity of the impairment of liver function measured by the galactose-elimination capacity (r = 0.53 to 0.69; p less than 0.05). We conclude that dynamic 31P magnetic resonance spectroscopy is a safe, clinically feasible test that allows detailed insights into biochemical events in liver disease.

Adenosine Triphosphate↗

PubMed1992

Prevention and treatment of high altitude pulmonary edema by a calcium channel blocker.

High altitude pulmonary edema (HAPE) is characterized by marked pulmonary hypertension. Treatment of 6 subjects suffering from radiographically documented HAPE with the calcium channel blocker nifedipine, lowered pulmonary artery pressure and resulted in clinical improvement, better oxygenation, reduction of alveolar-arterial oxygen gradient and a progressive clearing of alveolar edema on chest x-ray. This amelioration occurred despite continued exercise at an altitude above 4000 m and without supplementary oxygen. Prophylactic application of nifedipine slow release preparation, 20 mg every 8 hours, prevented HAPE in 9 out of 10 subjects with a history of radiographically documented HAPE upon rapid ascent and subsequent stay to an altitude of 4559 m. Seven of 11 comparable subjects who received placebo developed pulmonary edema at 4559 m. As compared with the subjects who received placebo, those who received nifedipine had a significantly lower mean systolic pulmonary artery pressure, alveolar-arterial pressure gradient of oxygen and symptom score of acute mountain sickness at 4559 m. Thus nifedipine offers a potential emergency treatment of HAPE when descent or evacuation is impossible and oxygen is not available. Prophylactic administration of nifedipine prevents HAPE in susceptible subjects. High pulmonary artery pressure has an important role in the pathogenesis of HAPE.

Acute Disease↗

PubMed1992

Effect of reduced expiratory pressure on pharyngeal size during nasal positive airway pressure in patients with sleep apnoea: evaluation by continuous computed tomography.

BACKGROUND: This study aimed to determine whether reducing the expiratory pressure during nasal positive airway pressure for reasons of comfort causes a substantial decrease in the upper airway calibre. METHODS: Eight patients with obstructive sleep apnoea were studied. Continuous computed tomography (each run lasting 12 seconds) was used to measure minimum and maximum pharyngeal cross sectional areas at the velopharynx and the hypopharynx. Pharyngeal areas were measured while patients were awake and breathing without assistance, during the application of 12 cm H2O continuous positive airway pressure, and during bi-level positive airway pressure with an inspiratory pressure of 12 cm H2O and an expiratory pressure of 6 cm H2O. RESULTS: Nasal continuous positive airway pressure significantly increased the mean minimum and maximum upper airway areas at both the velopharynx and the hypopharynx compared with normal unassisted breathing. Bi-level positive airway pressure did not show a statistically significant increase in the minimum upper airway area at either level compared with normal unassisted breathing. The minimum areas of the velopharynx and hypopharynx were smaller with bi-level than continuous positive airways pressure in six of eight and eight of eight patients respectively but these were still greater than during unassisted breathing in seven of eight and six of eight patients respectively. CONCLUSIONS: Continuous positive airway pressure at 12 cm H2O is more effective in splinting the pharynx open than bi-level positive airway pressure with an inspiratory positive airway pressure of 12 cm H2O and an expiratory pressure of 6 cm H2O in patients with obstructive sleep apnoea during wakefulness, suggesting an important role for expiratory positive airway pressure. The clinical importance of this finding needs to be evaluated during sleep.

Humans↗

PubMed1992

[Radiologic and nuclear medicine diagnosis of lung embolism].

The imaging methods used in diagnosing pulmonary embolism and their appropriate indication in individual situations are discussed. Chest radiography is needed to exclude other diseases, whereas nuclear ventilation and perfusion scans are the main screening method and have not been replaced by intravenous digital subtraction angiography up to now. As long as these non-invasive methods are clearly negative or positive, no other method is needed. With questionable findings (intermediate scan probability), pulmonary angiography is needed, above all when there is a contraindication to anticoagulation.

Angiography, Digital Subtraction↗

PubMed1992

[Imaging procedures and fine needle puncture of focal liver lesions].

Ultrasonography, as screening method of choice, answers questions as to the size of the liver, the structure of the parenchyma, focal lesions and the dilatation of the biliary system. To characterize focal lesions, to stage tumors and for a better topographic localization, computed tomography or magnetic resonance imaging is useful. The differential diagnosis of focal lesions, such as cysts, hemangioma or focal nodular hyperplasia is achieved by the combination of laboratory, imaging and nuclear medicine methods. In other cases, needle-biopsy under sonographic or CT guidance is decisive.

Biopsy, Needle↗

PubMed1992

[Lung radiology].

Specific clinical problems of the lung ask for evaluation by specific imaging methods. Chest radiography, although still fundamental, is used more carefully, whereas computed tomography, nuclear medicine methods, MRI and angiography all contribute to answer specific questions.

Diagnosis, Differential↗

PubMed1991

Prevention of high-altitude pulmonary edema by nifedipine.

BACKGROUND: Exaggerated pulmonary-artery pressure due to hypoxic vasoconstriction is considered an important pathogenetic factor in high-altitude pulmonary edema. We previously found that nifedipine lowered pulmonary-artery pressure and improved exercise performance, gas exchange, and the radiographic manifestations of disease in patients with high-altitude pulmonary edema. We therefore hypothesized that the prophylactic administration of nifedipine would prevent its recurrence. METHODS: Twenty-one mountaineers (1 woman and 20 men) with a history of radiographically documented high-altitude pulmonary edema were randomly assigned to receive either 20 mg of a slow-release preparation of nifedipine (n = 10) or placebo (n = 11) every 8 hours while ascending rapidly (within 22 hours) from a low altitude to 4559 m and during the following three days at this altitude. Both the subjects and the investigators were blinded to the assigned treatment. The diagnosis of pulmonary edema was based on chest radiography. Pulmonary-artery pressure was measured by Doppler echocardiography and the difference between alveolar and arterial oxygen pressure was measured in simultaneously sampled arterial blood and end-expiratory air. RESULTS: Seven of the 11 subjects who received placebo but only 1 of the 10 subjects who received nifedipine had pulmonary edema at 4559 m (P = 0.01). As compared with the subjects who received placebo, those who received nifedipine had a significantly lower mean (+/- SD) systolic pulmonary-artery pressure (41 +/- 8 vs. 53 +/- 16 mm Hg, P = 0.01), alveolar-arterial pressure gradient (6.6 +/- 3.8 vs. 11.8 +/- 4.4 mm Hg, P less than 0.001), and symptom score of acute mountain sickness (2.0 +/- 0.7 vs. 3.9 +/- 1.9, P less than 0.01) at 4559 m. CONCLUSIONS: The prophylactic administration of nifedipine is effective in lowering pulmonary-artery pressure and preventing high-altitude pulmonary edema in susceptible subjects. These findings support the concept that high pulmonary-artery pressure has an important role in the development of high-altitude pulmonary edema.

Adult↗

PubMed1991

Magnetic resonance angiography of abdominal vessels: early experience using the three-dimensional phase-contrast technique.

Based on three-dimensional acquisition of three sequences sensitive to one flow-direction, abdominal magnetic resonance phase-contrast angiography (MRA) was performed in 13 volunteers and 20 patients. The subjects received no antiperistaltic medication and were allowed to breath normally during the three acquisition periods of 11 minutes. The frequency of demonstration of the normal aorta, superior mesenteric and right and left renal arteries was 100%/100%/91%/100%, and of the inferior vena cava, splenic, superior mesenteric and portal veins was 92%/67%/92%/100%, respectively, whereas other abdominal vessels were seen less constantly. In renal artery stenosis or occlusion, MRA detected eight out of nine pathological arteries, missed only a minimal stenosis and was never false positive. In all 10 cases of portal hypertension, MRA demonstrated the venous collaterals detected by conventional angiography and in six cases showed more collaterals, particularly paravertebral vessels. A Budd-Chiari syndrome was investigated as well. If the accuracy of MRA can be proved in larger studies, it may become an important diagnostic tool in evaluating abdominal vascular pathology, such as renal artery stenosis or portal hypertension.

Abdomen↗

PubMed1991

Variable radiomorphologic data of high altitude pulmonary edema. Features from 60 patients.

The purpose of the study was to collect radiomorphologic data of a large population of subjects with high altitude pulmonary edema. A blinded retrospective analysis of 60 patients severe enough to warrant hospital admission is reported. Immediately after rescue to low altitude, the severity of HAPE was graded using a quadrant-based scoring system (0-4 each quadrant). Its distribution and the morphologic features were noted. HAPE was more severe in the base, and specifically, the right lower quadrant, as compared to the other quadrants. It was often located both centrally and peripherally (60 percent) and in 92 percent was characterized by air space disease of homogeneous (n = 40) rather than patchy distribution (n = 15). In recurrent HAPE (n = 13), radiomorphologic data were as variable as among different HAPE patients. We conclude that HAPE does not have one common radiomorphologic condition. Based on the literature, earlier experience, and follow-up observations, we hypothesize that it may start patchy and peripheral, supporting the concept of uneven vasoconstriction with overperfusion and/or permeability leak. Later on, such as in the severe cases studied, it becomes homogeneous. Recurrent episodes generally do not show an identical distribution of HAPE, suggesting that structural abnormalities are not involved in the pathogenesis of HAPE.

Adult↗

PubMed1991

Effects of slow ascent to 4559 M on fluid homeostasis.

Since acute mountain sickness (AMS) is associated with rapid ascent and with fluid retention, we assessed clinical status and fluid homeostasis in men slowly ascending on foot over 3 d to 4559 m and remaining at this altitude 5 d. We studied 15 male mountaineers, 6 of whom had previously had repeated, severe AMS or high altitude pulmonary edema (HAPE), at 1170 m, 3611 m, and 4559 m. We found that four of the six subjects with previous AMS or HAPE compared with none of nine with no such history, developed these conditions. Those who remained well had a diuresis that could not be overcome by increasing fluid intake and no change in renin activity, plasma aldosterone, or atrial natriuretic peptide (ANP). Those who became ill showed considerable weight gain independent of fluid intake, and a great increase in ANP which correlated with measurements of right atrial cross section. We conclude that mountaineers who have previously experienced repeated AMS or HAPE get fluid retention despite slow ascent and that this is associated with widening of the atrium and an increase in ANP.

Adult↗

PubMed1991

Detection of flexor tenosynovitis by magnetic resonance imaging: its relationship to diurnal variation of symptoms.

Fifteen patients with noninfectious arthritis and morning stiffness were examined clinically, and with magnetic resonance imaging (MRI) at the metacarpophalangeal level of one hand in the evening and early the following morning. Our purpose was to determine the prevalence of hand flexor tenosynovitis, and to look for diurnal changes in the swelling state of the flexor tendon sheaths as a possible cause for morning stiffness. MRI showed a higher prevalence of flexor tenosynovitis than clinically suspected by using the pinch test. We could not observe an increase in soft tissue swelling in the morning compared to the evening.

Adult↗

PubMed1991

[Imaging procedures in the evaluation of tumors of the thoracic wall].

Modern sectional imaging methods supplement the clinical examination of chest wall tumors ideally by demonstrating their deeper components and relation to neighbouring structures. Imaging methods are still limited in demonstrating detail anatomy, a disadvantage that is caused by limited soft tissue contrast and motion artifacts. In certain cases, a specific diagnosis is made by the specific behaviour of the tissue, whereas much more often morphological criteria and the topographic location and relation of the tumor help get the specific diagnosis. Image-guided percutaneous biopsy of the chest wall is an easy, relatively non invasive way of getting the definitive diagnosis.

Humans↗

PubMed1991

Clinical, radiologic and magnetic resonance monitoring for skeletal toxicity in pediatric patients with cystic fibrosis receiving a three-month course of ciprofloxacin.

Because of arthropathic toxicity observed in growing animals the quinolone antibiotics are not recommended for use in children. Recently, magnetic resonance imaging performed in juvenile animals was found to predict ciprofloxacin-induced cartilage damage at the knee joint. We conducted clinical, laboratory, radiologic and magnetic resonance imaging investigations in 13 prepubertal (age range, 6 to 13 years) and 5 postpubertal patients (age range, 14 to 24 years) with cystic fibrosis at the start and the end of a 3-month course of ciprofloxacin (30 mg/kg of body weight/day, administered orally in two equal doses) and at follow-up 4 to 6 months later. Our comprehensive monitoring gave no evidence for arthropathogenicity. Detailed physical skeletal function tests, height velocity values, laboratory studies of bone metabolism and conventional radiographs of both knees revealed no abnormalities. Moreover the serial magnetic resonance images of the left knee demonstrated lack of joint effusion, intact two-layer appearance of the cartilage and unaffected thickness of the articular cartilage measured at five anatomically different points. Our results together with the published data on quinolone use in pediatrics suggest that ciprofloxacin does not cause arthropathy in humans.

Adolescent↗

PubMed1990

[Magnetic resonance angiography. Work in progress].

Rapid progress has been made in the development and clinical application of magnetic resonance (MR) techniques for creating angiogram-like images of blood vessels. Combinations of techniques such as gradient-echo pulse sequences and flow compensation (bright blood imaging) or presaturation (black blood imaging) permit the signal intensities of moving spins to be altered, so as to generate contrast between flowing blood and stationary tissues. Postprocessing of the images allows the creation of projection angiograms, which show the vasculature in a large slice of the body. Preliminary studies suggest a variety of potential clinical applications, including intracranial arteriovenous malformations and aneurysms, carotid artery disease, portal hypertension, renal artery stenosis, peripheral arterial disease and venous thrombosis. At present, MR angiography is not directly competitive with conventional contrast angiography because of lower spatial resolution and loss of signal from flow turbulence and from slow flow. Nonetheless, it is proving to be a useful clinical tool for the investigation of vascular pathology involving the head and body.

Angiography↗

PubMed1990

[Magnetic resonance in oncology].

The physical and biological background to magnetic resonance imaging (MRI) in patients with neoplasms is reviewed. The clinical indications for this method of diagnosis, staging, and follow-up of malignant neoplasms are discussed on the basis of the guidelines given by the MRI Consensus Conference on April 25-26, 1989, in Berne. MRI is the modality of choice in patients with neoplasms of the central nervous system and the musculoskeletal system. Further emerging indications for MRI are neoplasma of the ENT region, liver, and pelvic organs. Finally, the foreseeable developments in MRI and in magnetic resonance spectroscopy (MRS) are mentioned.

Abdominal Neoplasms↗

PubMed1990

[Nuclear spin tomography in synovitis: experimental and clinical results].

We report our experimental and clinical results in the evaluation of synovitis using magnetic resonance imaging (MRI), and discuss them in the light of the literature. Using rheumatoid arthritis in the rat as a model, we have shown that MRI is more sensitive than physical examination and X-ray for the diagnosis of early soft-tissue inflammation in arthritis. On the basis of MRI findings, in patients with morning stiffness we have found an incidence of tenosynovitis higher than that reported in the literature. Because other groups have demonstrated the usefulness of MRI for the evaluation of inflammatory cartilage and bony lesions in arthritis as well, we anticipate that this method will assume increasing importance in the diagnosis and monitoring of rheumatoid arthritis and related diseases.

Animals↗

PubMed1990

Spiral volumetric CT with single-breath-hold technique, continuous transport, and continuous scanner rotation.

Continuous computed tomographic (CT) scanning of organ volumes during a single breath hold was studied. The authors modified the table feed mechanism of a continuously rotating CT scanner to allow patient transport at low, but accurately controlled, speeds (0.1-11.0 mm/sec) during continuous 1-second scanning. An algorithm was designed to reconstruct artifact-free images for arbitrary table positions from the helical data by interpolating between adjacent scans. Section sensitivity profiles were enlarged; the section width for a 10-mm section and a speed of 10.0 mm/sec was increased by a factor of 1.3, compared with the nominal value. Clinical examples were presented for studies of lung nodules and studies enhanced with contrast medium. Major advantages are the possibility of continuous scanning of extended volumes within a breath-hold period and retrospective, arbitrary selection of anatomic levels.

Humans↗