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Biomedical subjects

P Schaller

Publications and source records attributed to P Schaller.

At least 19 recordsLinked to original sources
PubMed1992

[Measuring microcirculation after replantation and revascularization].

Eighty-four patients were evaluated following replantation or revascularization. Extremity function in daily and professional life was altogether satisfactory. Microcirculation investigations in eight patients included thermography, laser-doppler-flowmetry and photoplethysmography. The rewarming period and postocclusive hyperemia after standardized cooling of the upper extremity were determined. In areas of hypesthesia, the rewarming period was clearly delayed. In addition, reactive hyperemia after occlusion of circulation was significantly reduced.

Amputation, Traumatic↗
PubMed1992

[Plaster filling in surgical treatment of enchondroma--a justified therapeutic procedure?].

Enchondroma are the most frequent tumors of the hand. These benign tumours are characterized by slow growth, the lack of clinical symptoms and by accidental discovery. The surgical treatment of enchondroma includes resection of the tumor tissue from the bone matrix, and subsequent filling of the defect with autologous or homologous spongiosa or with sterile plaster of Paris. We showed in a period from 1982 to 1989 that there is no difference with respect to the clinical outcome between our patients receiving autologous spongiosa (n = 25) or plaster filling (n = 35). Owing to its simplicity and lack of additional surgery at the iliac crest, we prefer the method of plaster filling. Animal studies performed by our group have demonstrated that implanted plaster is transformed to spongiosa within four to ten weeks without adverse effects.

Animals↗
PubMed1991

High frequency oscillatory ventilation near resonant frequency of the respiratory system in rabbits with normal and surfactant depleted lungs.

It has been suggested that high frequency oscillatory ventilation (HFV) might improve gas exchange and reduce the risk of pressure-related side-effects compared to conventional mechanical ventilation (CMV). Whereas most studies have used arbitrarily set frequencies for HFV, we evaluated the effects of HFV near resonant frequency (fr). Anaesthetised and tracheotomized adult rabbits (n = 10; 3.8-5.1 kg body weight) were ventilated by alternating periods of CMV and HFV near fr. Negative ventilator resistance was used for complete resistive unloading of the respiratory system before each HFV period. This enabled a continuous swinging at resonance thus allowing measurement of fr and selection of exactly that frequency for the HFV run. Intra-animal CMV-HFV comparisons (n = 4) were performed on each animal: with healthy lungs at a mean airway pressure (MAP) of 0.5 kPa and after saline lung lavage at MAPs of less than 1.5 kPa; 1.5-1.8 kPa; greater than 1.8 kPa. Surfactant removal caused total respiratory system compliance (Ctot) to decrease from 44 +/- 5 to 22 +/- 3 ml/kPa. Corresponding fr was 244 +/- 48 and 360 +/- 30 min-1, respectively. HFV produced effective pulmonary gas exchange but did not improve arterial oxygenation in comparison with CMV at matched MAPs both before and after surfactant depletion. Volume amplitudes of oscillation necessary to achieve normocapnia were slightly above the natural plus equipment (2 ml) dead space. Maximum intra-alveolar pressure (Pmax) was calculated for the HFV runs from MAP, Ctot, and the volume amplitude of oscillation. Pmax during CMV was nearly twice that during HFV at equivalent PaCO2 and equivalent MAPs throughout the experiments.

Animals↗
PubMed1991

A ventilator generating a positive or negative internal compliance.

This paper describes technical details of a ventilator for altering the resistive and elastic load placed on respiratory muscles during spontaneous breathing in intubated infants. Positive or negative values for ventilator resistance and/or ventilator compliance can be chosen by superimposing the weighted sum of the flow and/or the volume signal over the input to a pressure controller within the pressure feedback control system of the ventilator. The aim of the study was to compare values of the ventilator's compliance (Cv), as measured with a ventilation mechanics calculator, with those Cv values set by the ventilator's Cv control knob on the front panel. Another aim was to compare measured values of total compliance of a combined ventilator-lung model system (Ct) with the values expected according to theory where 1/Ct = 1/Cv + 1/C1m (Eq. alpha; C1m is the lung model's compliance). The Cv values set on the front panel were nearly identical to those measured (Cvm = 0.97 * Cvs + 0.54) over the whole tested range from -20 to +20 ml/kPa. Similarly, the measured Ct values were almost equal to those expected according to Eq. alpha; the standard deviation of the relative residuals was 2.7% for elastic loading and 12.4% for elastic unloading. We conclude that the ventilator described in this study can effectively provide both elastic loading and elastic unloading of spontaneous breathing, as expected according to theory.

Biomedical Engineering↗
PubMed1991

[Determination of respiratory system compliance from resonance frequency--animal experiment].

10 anaesthetized and tracheotomized rabbits were used to test the possibility for calculation of total respiratory system compliance from resonance frequency (CR). Reference values were obtained by inflation method compliance (CI). A new servocontrolled infant ventilator was used with an integrated negative ventilator resistance mode for resistive unloading of combined resistances of lung, endotracheal tube and ventilator. This evoked oscillation at resonant frequency. By analogy with electrical circuit theory compliance was calculated as follows: CR = 1/(4 pi 2 x square root I.RF2). Pairs of CI and CR values were obtained from each animal during spontaneous breathing, after pancuronium relaxation and after surfactant depletion by lavage. There was found a significant linear correlation between CR and CI values (CR = 1.1 x CI-0.74; r = 0.97).

Animals↗
PubMed1990

Titration of continuous positive airway pressure by the pattern of breathing: analysis of flow-volume-time relationships by a noninvasive computerized system.

Infants can defend or even dynamically elevate their functional residual capacity with additional respiratory muscle work by retarding early expiratory airflow (V) with postinspiration inspiratory muscle activity and/or laryngeal narrowing, or by starting inspiration before expiration to the relaxation volume has been completed. In order to study the effect of continuous positive airway pressure (CPAP) on both phenomena in 23 infants (birthweight 1,746 +/- 417 g), we elevated the airway pressure stepwise in 0.2 kPa increments. A computerized bedside flow-volume (V/V) analysis was used for evaluation. In 16 "responders" early expiration braking decreased and "premature inspiratory interruption" was postponed at an "appropriate CPAP level." The linear segment (relaxation line) of the V/V-loop was lengthened until expiratory time reached a maximum. Elevation of CPAP beyond this level again produced a rapid, shallow pattern, often combined with flow acceleration late in expiration (recruitment of expiratory muscles). In the remaining seven infants (non-responders) these latter signs of excessive airway pressure already occurred at the lowest CPAP levels applied during the "titration trials." Respiratory rate without CPAP was different between responders (84 +/- 17/min) and non-responders (46 +/- 17/min). This approach for determining the appropriate CPAP level might reduce the risk of respiratory muscle fatigue.

Computer Systems↗
PubMed1990

An infant ventilator technique for resistive unloading during spontaneous breathing. Results in a rabbit model of airway obstruction.

The combined system of ventilator circuit, endotracheal tube, and lung commonly imposes a resistive load on spontaneous breathing efforts. It is possible to compensate for this positive resistance by a device generating a "negative ventilator resistance" (NVR), i.e. delivering a positive pressure during inspiration and a negative pressure during expiration in constant proportion to the instantaneous flow of the spontaneous breathing. The concept of NVR implies that there must not be any phase lag between flow and pressure signals. In eight anesthetized, intubated, spontaneously breathing rabbits (mean body wt 3570 g, range 2900-4600 g), challenged either by aerosolized histamine or an extrapulmonary resistive load, lung mechanical data were calculated from esophageal pressure and flow signals. Each animal served as its own control with and without NVR. In a total of 39 experiments, NVR was applied in amounts between 1 and 15 kPa.s/L. During both types of additional resistive load, NVR immediately reduced the resistive work of breathing. There was a strong linear correlation between the amount of NVR applied and the decrease in total resistance, where the total resistance equals the resistive load on the animal's respiratory muscles (sum of the resistances of all components of the combined respirator-lung system): r = 0.93, p less than 0.001. The relationship between NVR and the drop in resistive work per mL of tidal volume was similar: r = 0.85, p less than 0.001. Throughout the experiments, NVR operated in perfect synchronization with the animal's spontaneous breathing activity.

Airway Obstruction↗
PubMed1990

A method of calculating total respiratory system compliance from resonant frequency: validity in a rabbit model.

Ten anesthetized, tracheotomized, adult rabbits were used to test the validity of a method for calculation of total respiratory system compliance from resonant frequency (Cr). Reference values were obtained during constant flow inflation of the relaxed respiratory system by dividing the volume gain by the related difference in pressure at the airway opening (inflation method compliance, Ci). The animals were connected to a new type of servo-controlled infant ventilator. Besides volume-controlled mechanical ventilation at constant inspiratory flow rate and intermittent mandatory ventilation, there is a negative ventilator resistance mode integrated in this device for resistive unloading (Schulze A, Schaller P, Gehrhardt B, Mädler H-J, Gmyrek D: Pediatr Res 28:79-82, 1990). To measure resonant frequency (fr), the respiratory system was totally unloaded for a short period by a negative ventilator resistance exceeding the combined resistances of the endotracheal tube and airways. This evoked a continuous oscillation at fr. By analogy with electrical circuit theory, Cr was calculated according to C = 1/(4 pi 2.I.fr2) where C is compliance and I is inertance. The inertance of the endotracheal tube is given and that of the bronchial tree was ignored assuming a much greater total cross-sectional area and therefore much lower inertance when compared with the endotracheal tube. Three pairs of Ci - Cr values were obtained from each animal: 1) during intact respiratory muscle activity; 2) after pancuronium relaxation, and 3) after surfactant depletion by saline washout.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Malignant somatostatinoma--diagnosis after 6 years].

UNLABELLED: Early symptoms of malignant somatostatinoma with dyspeptic complaints, moderate diabetes mellitus and cholecystolithiasis are the reason of primary treatment of these patients by surgeons. CASE REPORT: In a 34-year old patient with typical anamnesis of cholecystitis and moderate diabetes mellitus liver metastases were seen during laparotomy. In the beginning the metastases were mistaken for hepatocellular carcinoma histologically. There was no deterioration until June 1988 when a high-grade stenosis of the duodenum has developed. Now a malignant somatostatinoma was diagnosed histologically and confirmed by immunohistology. Somatostatinomas are generally diagnosed by repeated measures of increased plasma SLI associated with decreased insulin, glucagon, pancreatic-polypeptide (PP) and vasoactive-intestinal-peptide (VIP). In normally or moderately increased plasma SLI concentrations provocation with tolbutamid may be helpful. Treatment should remove most of the tumor by surgical intervention, while chemotherapy must be less pronounced.

Adenoma, Islet Cell↗
PubMed1990

[The etiology of ulnar nerve compression syndrome].

A retrospective investigation of the etiology of 132 patients with peripheral ulnar nerve compression was performed. Mainly there was external long-term pressure or compressive lesions near the nerve and disturbances of the osseous structures at the elbow and the wrist.

Female↗
PubMed1989

High frequency oscillatory and conventional mechanical ventilation in experimental surfactant deficiency: a study using a new infant ventilator technique.

The performance of a new infant ventilator system had to be evaluated. Technically it is characterized by flow (V)- and pressure (P)-transducers mounted immediately near the endotracheal tube. A microcomputer works as a function generator and governs servo-controllers for V and P thus offering a multiplicity of different modes both of the conventional (CMV) and high frequency oscillatory (HFO) type. The additional dead space imposed by the system is identical with its internal compressible volume of 2 ml. Serial pulmonary lavages were performed in 17 adult rabbits while on CMV. PaO2 per unit of mean airway pressure (MAP) decreased thereby from 95.9 +/- 29.3 to 9.0 +/- 6.7 (kPa/kPa). The animals were then alternately ventilated by HFO (5, 10, or 20 Hz) and CMV, at matched MAP's. No significant difference in PaO2 between the two methods was revealed in intra-animal comparisons except a slight superiority of CMV at MAP's above 1.7 kPa (P less than 0.05). There was no clear linear relationship between PaO2 and MAP both at CMV and HFO. A strong increase in PaO2 often occurred beyond a MAP threshold. In 37 postlavage HFO runs at 5 Hz in 13 animals volume amplitudes of 3.19 +/- 0.5 ml/kg of bodyweight resulted in PaCO2 levels of 6.29 +/- 1.87 kPa. Except in one experiment (10 Hz) volume amplitudes below the natural dead space produced arterial hypercapnia.

Animals↗
PubMed1989

[Rupture of the palmar plate--conservative or surgical therapy].

Disruptions of the palmar plate are frequently overlooked injuries. As the palmar plate stabilises the PIP joint in combination with the collateral ligaments untreated injuries may result in severe complaints. Detailed anatomical and functional knowledge is therefore necessary to diagnose the degree of injury. In addition to ligamentous disruption osseous chips may occur and can be divided into four degrees (Hintringer 1987). By the study of results of 178 cases specific treatment has been established. Surgical intervention is indicated in the presence of an unstable PIP joint, subluxation or osseous chips grade 3 and 4 (Hintringer). The aim should be a painfree and stable joint. Small limitations in movement can be tolerated.

Adult↗
PubMed1987

[Primary hyperparathyroidism--experiences with concomitant diseases, symptoms, preoperative diagnosis and surgical procedure over a period of 14 years].

In a 14-years period (1970-1984) eight-three patients were operated on for primary hyperparathyroidism (pHPT) at the University Hospital of Erlangen. Special attention was paid to associated diseases, symptoms, preoperative diagnostic parameters were serum calcium, parathyroid hormone in venous blood, cyclic AMP in 24 h-urine. In 15.7% only borderline increased serum calcium values were measured. Ulcer incidence in pHPT was 19% as compared with approx. 7% in the general population. There was no increased incidence of pancreatitis in pHPT. The possibility of an association of pHPT with the Multiple Endocrine Neoplasia (MEN) syndrome was emphasized and measures of early diagnosis proposed.

Adenoma↗
PubMed1986

Intravenous glucose tolerance after Whipple's procedure in patients with chronic pancreatitis--relative influence of occlusion of the pancreatic duct.

An intravenous glucose tolerance test was carried out to compare chronic pancreatitis patients (n = 17) who had undergone partial duodenopancreatectomy with (n = 9) and without (n = 8) occlusion of the residual pancreatic duct by Prolamin. The results obtained in 10 healthy volunteers were plotted as background information reflecting the normal metabolic response. Insulin- and C-peptide secretion were greatly decreased after both resection alone, and resection plus occlusion. However, the glucose tolerance (integrated glucose; K-values) appeared relatively well preserved in the two groups. The decrease in insulin appeared more marked after resection plus occlusion as compared with the non-occluded group. It is concluded that partial duodenopancreatectomy without or with ductal occlusion impairs insulin secretion, and leaves tolerance to an intravenous glucose load relatively stable. The mechanism underlying the latter observation is unknown at present.

Adult↗