A novel smartphone app for blood pressure measurement: a proof-of-concept study against an arterial catheter.

Smartphones may provide a highly available access to simplified hypertension screening in environments with limited health care resources. Most studies involving smartphone blood pressure (BP) apps have focused on validation in static conditions without taking into account intraindividual BP variations. We report here the first experimental evidence of smartphone-derived BP estimation compared to an arterial catheter in a highly dynamic context such as induction of general anesthesia. We tested a smartphone app (OptiBP) on 121 patients requiring general anesthesia and invasive BP monitoring. For each patient, ten 1-min segments aligned in time with ten smartphone recordings were extracted from the continuous invasive BP. A total of 1152 recordings from 119 patients were analyzed. After exclusion of 2 subjects and rejection of 565 recordings due to BP estimation not generated by the app, we retained 565 recordings from 109 patients (acceptance rate 51.1%). Concordance rate (CR) and angular CR demonstrated values of more than 90% for systolic (SBP), diastolic (DBP) and mean (MBP) BP. Error grid analysis showed that 98% of measurement pairs were in no- or low-risk zones for SBP and MBP, of which more than 89% in the no-risk zone. Evaluation of accuracy and precision [bias ± standard deviation (95% limits of agreement)] between the app and the invasive BP was 0.0 ± 7.5 mmHg [- 14.9, 14.8], 0.1 ± 2.9 mmHg [- 5.5, 5.7], and 0.1 ± 4.2 mmHg [- 8.3, 8.4] for SBP, DBP and MBP respectively. To the best of our knowledge, this is the first time a smartphone app was compared to an invasive BP reference. Its trending ability was investigated in highly dynamic conditions, demonstrating high concordance and accuracy. Our study could lead the way for mobile devices to leverage the measurement of BP and management of hypertension.

A feasability study of color flow doppler vectorization for automated blood flow monitoring.

An ongoing issue in vascular medicine is the measure of the blood flow. Catheterization remains the gold standard measurement method, although non-invasive techniques are an area of intense research. We hereby present a computational method for real-time measurement of the blood flow from color flow Doppler data, with a focus on simplicity and monitoring instead of diagnostics. We then analyze the performance of a proof-of-principle software implementation. We imagined a geometrical model geared towards blood flow computation from a color flow Doppler signal, and we developed a software implementation requiring only a standard diagnostic ultrasound device. Detection performance was evaluated by computing flow and its determinants (flow speed, vessel area, and ultrasound beam angle of incidence) on purposely designed synthetic and phantom-based arterial flow simulations. Flow was appropriately detected in all cases. Errors on synthetic images ranged from nonexistent to substantial depending on experimental conditions. Mean errors on measurements from our phantom flow simulation ranged from 1.2 to 40.2% for angle estimation, and from 3.2 to 25.3% for real-time flow estimation. This study is a proof of concept showing that accurate measurement can be done from automated color flow Doppler signal extraction, providing the industry the opportunity for further optimization using raw ultrasound data.

[Monitoring neuromuscular function: capnography versus relaxometry]. / Uberwachung der neuromuskulären Funktion: Kapnographie versus Relaxometrie.

OBJECTIVE: A notch ("curare cleft") in the plateau phase of the capnogram of the ventilated patient has been presumed to be a typical early sign of the fading effect of muscle relaxants on the diaphragm. For that reason a prospective study was done to investigate whether capnography can be used diagnostically to indicate the fading effect of vecuronium confirmed by peripheral relaxometry. METHODS: Twenty-five consecutive patients who received inhalation anaesthesia with isoflurane, N2O/O2, and vecuronium during elective neurosurgical procedures were studied. Whenever intraoperative "curare clefts" appeared in the capnogram, diaphragm activity was measured and a simultaneous relaxogram of the adductor pollicis muscle was recorded. After every such event, vecuronium was readministered for complete relaxation. RESULTS: A deformation of the capnogram was registered in 17/25 patients and in all instances (51/51) was caused by diaphragm activity. The deformation disappeared after renewed relaxation and was therefore a reliable indicator of spontaneous breathing. However, it did not correlate with the degree of relaxation of peripheral muscles, because diaphragm activity was present during all degrees of peripheral relaxation, but could also be absent even after complete recovery of neuromuscular transmission. CONCLUSION: Capnography is therefore not a reliable method to indicate the fading effect of muscle relaxants.

[Adjuvant therapy with pseudomonas immunoglobulin in artificially ventilated patients at a surgical intensive care unit]. / Adjuvante Therapie mit Pseudomonas-Immunglobulin bei beatmeten Patienten einer operativen Intensivstation.

Preoperative hospitalism and postoperative respiratory therapy together with antibiotical prophylaxis are risk factors for pulmonary infection due to Pseudomonas aeruginosa. Psomaglobin, a new Pseudomonas hyperimmune globulin, was given to 25 postoperative or posttraumatic patients during a prospective randomized study as an additional therapy for severe Pseudomonas infection. Respiratory therapy and therefore residence in the ICU were markedly shorter in the therapy (n = 25) than in the control group (n = 20).

[Comments on anesthesia procedures in mitochondrial encephalomyopathy]. / Uberlegungen zum Narkoseverfahren bei mitochondrialer Encephalomyopathie.

Mitochondrial encephalomyopathies (MEMP) are rare diseases caused by a disturbance of the mitochondrial chain of respiration. This prevents pyruvate from being completely integrated into the tricarboxylic acid (Krebs') cycle, and hence there is an accumulation of lactate. Histologically this is marked by the appearance of "ragged red fibres" in the light microscope which, in the electron microscope, are eventually recognised as typical accumulations of pathological mitochondria. The clinical pattern can vary greatly and ranges from ophthalmoplegia via mainly myopathic to encephalopathic forms. The pattern of signs and symptoms enables subclassification into three main syndromes (10): The Kearns-Sayre syndrome (KSS), "myoclonus epilepsy with ragged red fibres syndrome" (MERRF) and "mitochondrial myopathy, encephalopathy, lactic acidosis and strokelike episodes syndrome" (MELAS). Intermediate types, however, are frequent. Furthermore, quite a large number of other syndromes such as the "Toni-Fanconi-Debré syndrome" can be classified among the group of mitochondrial encephalomyopathies.--The patient must be classified as a risk patient. Disturbances of cardiac conduction may require a transient or permanent pacemaker. Increase in oxygen requirement must be avoided to prevent increase in lactate levels and development of lactate acidosis. The severity of the myopathy makes it necessary to exercise caution in the use of benzodiazepines and long-term relaxants. When using local anaesthetics one should consider both their negative dromotropism and the resulting reduction of the epileptic threshold. There is a relative contraindication for spinal and epidural anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on therapy of metabolic alkalosis during experimental uremia. Influences of arginine-hydrochloride on the intra- and extracellular acid-base status of the rat.

Severe metabolic alkalosis, combined with acute renal failure or uremia presents a difficult problem for the clinician. The standard treatment modalities of metabolic alkalosis are then limited and infusion of arginine-HCl is often tried in these cases. It was the purpose of this investigation to study the effects of arginine-HCl on the whole-body acid-base status during experimental uremia. While the extracellular acid-base status was determined from blood-gas measurements, the intracellular pH was calculated from the distribution of 5,5-dimethyl-2,4-oxazolidinedione. It was found that administration of arginine-HCl leads to a significant increase of intracellular pH though extracellular plasma pH decreases, and that arginine-HCl causes only an insignificant reduction of the intracellular bicarbonate concentration. The observed intracellular pH increase may have adverse consequences for patients and raises objections to the further use of arginine-HCl in the treatment of metabolic alkalosis, especially during renal failure or uremia.

[Acid-base equilibrium in anesthesiology and operative intensive care medicine. Physiology, pathophysiology and clinical aspects of alkalosis and mixed disorders]. / Der Säuren-Basen-Haushalt in der Anästhesiologie und operativen Intensivmedizin. Physiologie, Pathophysiologie und Klinik der Alkalosen und gemischten Störungen.

This review details basic and clinical aspects of metabolic and respiratory alkalosis and mixed acid-base disturbances. New experimental results show that NH4Cl and arginine-HCl should no longer be used in antialkalotic therapy because they increase intracellular pH and have no effect on intracellular bicarbonate concentration. Appropriate HCl solutions should be employed in severe metabolic alkalosis because they reduce pH and the bicarbonate concentrations in both body compartments.

[Acid-base homeostasis in anesthesiology and operative intensive care medicine. Physiology, pathophysiology and clinical aspects of acidoses]. / Der Säuren-Basen-Haushalt in der Anästhesiologie und operativen Intensivmedizin. Physiologie, Pathophysiologie und Klinik der Azidosen.

Basic and clinical aspects of acid-base physiology and acidoses are reviewed in this paper. Therapeutic principles on the treatment of metabolic and respiratory acidosis are discussed in detail. As far as buffer substances are necessary for antiacidotic therapy, sodium bicarbonate seems to be the agent of choice today. Sodium bicarbonate has a better extra- and intracellular effect than THAM, and should therefore be preferred in every day practice.

[Concentrations and levels of activity of important serum protein components in preserved serum]. / Konzentrations- und Aktivitätsmessungen wichtiger Serumproteinanteile in Serumkonserven.

The content of transport proteins, immune globulins, components of the complement system and protease inhibitors were estimated in two different plasma preparations, using bioassays by chromogenic substrates and laser nephelometry. The content of proteins under consideration was found about 50% less than in untreated human plasma. Some proteins such as antithrombin III and factor XIII are missing. The results are discussed in respect to clinical used of plasma preparations.

Influences of experimental uremia on the intra- and extracellular acid-base status of the rat.

In an experimental study the influences of beginning uremia were studied in nephrectomized rats. It was observed: (1) Though there was found a continuous decrease of extracellular pH due to accumulation of fixed acids there was a slight increase of intracellular pH resulting from concomitant hypocapnia. (2) There was found a constant loss of bicarbonate from the extra- and intracellular body compartment which was much more pronounced for the extracellular space. This loss of bicarbonate reflects the progressing metabolic acidosis and demonstrates that the intracellular compartment is more protected against an increase of hydrogen ion concentration than the extracellular space is. (3) The stability of the intracellular acid-base status during uremic metabolic acidosis arises the question whether our clinical practice with alkali substitution according to the Mellemgard-Astrup equation is still adequate in these cases. (4) Blood-gas analysis can only give information about the acid-base status of the extracellular body compartment. The large intracellular space which is the aim of our clinical therapy is excluded from these measurements. Simple reliance of blood-gas analysis may lead to wrong conclusions and mistakes in therapy.

[Systolic time intervals during increasing left ventricular filling pressure following extracorporeal circulation. A comparative impedance-cardiographical study (author's transl)]. / Systolische Zeitintervalle bei steigenden linksventriculären Füllungsdrucken nach extracorporaler Zirkulation. Eine vergleichende impedanzcardiographische Untersuchung.

In 26 patients invasively measured haemodynamic parameters and impedance cardiographically determined systolic time intervals have been compared after open heart surgery with cardio-pulmonary bypass (aortic valve replacement, AVR (n = 7); mitral valve replacement, MVR (n = 7); aorto-coronary bypass, ACB (n = 10)). In both the AVR and ACB group an increase of left atrial pressure resulted in 1) a significant increase of left ventricular stroke work index (LVSWI), 2) a significant decrease of the relation of the pre-ejection period to left ventricular ejection time (PEP/LVET), and 3) a significant increase of cardiac output (thermodilution technique and impedance cardiography), whereas no significant alterations were found in the MVR group. Furthermore cardiac output determination using both the direct thermodilution technique and the indirect impedance method revealed a close correlation (n = 63, range cardiac output 1.5-12.51/min, r = 0.852). These data clearly demonstrate the utility of the non invasive impedance cardiography method compared with invasive methods with respect to measurement of cardiac and haemodynamic parameters, even in critical situations.

[Leakage of irrigating solution during transurethral prostatectomy. An impedance cardiography study (author's transl)]. / Einschwemmung von Spülflüssigkeit bei transurethraler Prostataresektion. Impedanzcardiographische Untersuchungen.

The aim of this study was to investigate the influence of the incorporation of irrigating solution during transurethral prostatectomy on the pulmonary and cardiovascular system. In 16 patients the changes of thoracic ground impedance were compared with those of the central venous pressure. Myocardial function was evaluated semiquantitatively by use of the systolic time intervals and pulmonary gas exchange by arterial blood gas analysis. There was a significant correlation between the increase of central venous pressure and the decrease of thoracic ground impedance. There was also a significant increase of the relation of pre-ejection period (PEP) to left ventricular ejection time (LVET) meaning an impairment of myocardial function, an increase of cardiac output, and a severe decrease of arterial oxygen pressure. The influence of the incorporation of irrigating solution on the pulmonary and cardiovascular system is discussed, the noninvasive character and simplicity of handling the impedance cardiography is pointed out, and the possibilities of monitoring critically ill patients undergoing transurethral prostatectomy by this method is demonstrated.

[New aspects in the clinical picture of malignant hyperthermia (author's transl)]. / Neue Aspekte zum Krankheitsbild der malignen Hyperthermie und seine Therapie.

The key factor in malignant hyperthermia does not seem to be a defect in the calcium-storing membrane of the skeletal and cardiac muscle cells. The primary cause would appear to be deficiency of adenylate kinase.