Characterization of tannery wastewater and biomass in a membrane bioreactor using respirometric analysis.

Respirometric techniques and an activated sludge model (ASM) were applied for the characterization of tannery wastewater and biomass in a pilot plant membrane bioreactor (MBR) operating at high sludge age. The traditional respirometric tests and the IWA-ASM1 were modified to take into account the specific operating conditions, the solid-liquid separation technology and the wastewater complexity. As a result the wastewater biodegradable COD was fractionated into four components: readily biodegradable, rapidly hydrolysable, slowly hydrolysable and inorganic (due to the presence of reduced sulphur compounds). The kinetic and stoichiometric parameters of the biomass (heterotrophic and nitrifying) were estimated through the integration of model simulations and respirometric tests results. In particular the ammonium and nitrite-oxidizing biomasses were separately characterized: the growth kinetics of ammonium and nitrite-oxidizing bacteria resulted noticeably lower than the traditional reference values (mu(max,AOB)=0.25d(-1)e mu(max,NOB)=0.23d(-1) at 20 degrees C, respectively). The ASM was finally used to confirm that the results of the wastewater and biomass characterization allow to properly simulate the mixed liquor suspended solids in the MBR pilot plant and the COD concentration in the effluent.

Pharmacological atrial defibrillation via temporarily occluded coronary sinus: first clinical experience and implications for an implantable device.

UNLABELLED: The aim of this paper is to report the first experience of pharmacological atrial defibrillation in humans via a temporarily occluded coronary sinus. PATIENTS AND METHODS: In 6 patients (3 women, 3 men; mean age 57.8y, min 31, max 71), with clinical recurrences of atrial fibrillation, an occlusive coronary venogram was carried out in order to establish the origin of the Vein of Marshall. Atrial fibrillation was then induced by atrial pacing in all the patients and after an adequate waiting period to assure that the atrial fibrillation episode was persistent and stable, a bolus of a very low dose of an antiarrhythmic drug was delivered in 3-4 seconds into the temporarily balloon occluded coronary sinus near the orifice of the vein of Marshall. For both the venogram and the pharmacological test a Baim-Turi (USCI-Bard, Billerica MA) or a Vueport (Cardima, Fremont CA) catheter was used. RESULTS AND COMMENTS: In five patients a single dose of 7 mg of propafenone was immediately effective in restoring the sinus rhythm. In the remaining patient 2 doses of 7mg of propafenone failed to interrupt the arrhythmia, which was subsequently interrupted by a bolus of 0.1mg of ibutilide fumarate given after a waiting period of 20 minutes. Retroperfusion of the left atrium could account for these results; in fact the Vein of Marshall has no valvular apparatus in contrast with other coronary sinus tributary veins which are equipped with an uni- or bicuspidal valve. CONCLUSIONS: Pharmacological atrial defibrillation with a minimal dose of an antiarrhythmic drug delivered near the orifice of the Vein of Marshall via the temporarily occluded coronary sinus is feasible and effective. This new pharmacological atrial defibrillation can offer interesting opportunities in developing an implantable pharmacological atrial defibrillator.

Implantable pharmacological defibrillator (AIPhD): preliminary investigations in animals.

The treatment of ventricular fibrillation (VF) by means of automatic implantable cardioverter defibrillators (AICD) poses many severe problems and limitations at the present time. In order to overcome these problems, we propose a totally new way to terminate VF or ventricular sustained tachycardia (VST). Our proposal consists of replacing the electric shock, which is dangerous, delayed, and sometimes ineffective, with a "chemical" shock: i.e., a chemical bolus retroperfused in the coronary sinus (CS) immediately after VF arises. The possible device is hypothesized and preliminary investigations in animals, performed to verify the theoretical assumption, are presented. In rabbits, and in larger animals (sheep and swine). Drugs were perfused in the coronary bed: lidocaine was used in 86% and bretylium tosylate in 14% of the animals. The results were: lidocaine immediately terminated VF in 100% and sinus rhythm was restored in rabbits; lidocaine terminated VF in VST in sheep; and in swine, bretylium immediately produced sinus rhythm in one case; in another one, only delayed sinus rhythm was achieved but lasted a short time; in the last case ventricular tachycardia at 128 beats/min appeared. Because new drugs, which are really "defibrillating" drugs, are available (bretylium tosylate, bethanidine, clofilium, tricyclic antidepressants, phenotiazine derivatives), we plan to investigate these defibrillating drugs in isolated hearts, found in suitable animals like dogs (sheep and swine are difficult to defibrillate) and in humans during routine electropharmacological studies.

Results, problems and perspectives with the autoregulating pacemaker.

Experimental in vitro testing coupled with animal and clinical studies have shown that a pH sensor may sense acute changes in pH occurring in response to exercise. This signal may in turn be used as a determinant for optimal pacing rate. Further investigation into membrane coating of electrodes and algorithm testing is necessary to maximize sensor response and control.

[Epicardial pacing: clinica evaluation and comparison with transvenous pacing (author's transl)]. / Elettrostimolazione epicardica. Valutazione clinica e confronto con la stimolazione endocardica.

Clinical experience with permanent epicardial pacing during a five year-period in our centre is presented. The report is based on 37 epicardial and 656 transvenous pacemaker implantations. Intraoperative and early postoperative mortality were absent in the epicardial pacing group. Late hospital mortality, morbidity and electro-mechanical complications were less than with transvenous pacing. Among the complications peculiar to the epicardial pacing technique, we observed 3 cases of breakage of a lead, at the level of its epicardial connection. We conclude that the use of epicardial leads represents a safe and effective technique of cardiac pacing.

Preliminary experience with the pH-triggered pacemaker.

A cardiac pacemaker capable of responding to blood acidosis by change in its stimulation rate allows adjustment to a patient's metabolic needs. The blood pH is sensed by an iridium oxide electrode in the right atrium. During exercise, the venous pH decreases and the paced ventricular rate increases. If acidosis persists, the paced rate gradually returns to baseline and reaches it after about 70 minutes. A pH-triggered pacemaker has been implanted in a 72-year-old male. The pacemaker remained responsive one year after implant, increasing rate during exercise, cold pressor stress, ischemia of the arms and emotional stress.

[Clinical and biological aspects in patient with pH-triggered implanted pacemaker (author's transl)]. / Aspetti clinici e biologici in pazienti portatori di pacemaker pilotato dalle variazioni del pH ematico.

The Authors have selected the variations of blood pH to drive the pacing rate according to the new biological balance created by exercise. The clinical tests performed on the patients who have had a pH-triggered pacemaker implanted one year previously demonstrated that: a) during physical exercise there is an increase of cardiac rate triggered by the pacemaker, comparable with that noted when sinus rhythm is present; b) situations causing an increased production of cathecolamines and thus a pH variation--Cold Pressor Test, Ischaemic Test, as well as emotional stress--cause an increase of the stimulation rate of pH triggered pacemaker.