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Byline: Francesco Imperatore (1), Salvatore Cuzzocrea (2), Carlo Luongo (1), Antonella Scafuro (1), Antonella De Angelis (1), Francesco Rossi (1), Achille P. Caputi (2), Amelia Filippelli (1) Keywords: Zymosan-induced shock; Hyperbaric oxygen therapy; Vascular reactivity; Malondialdeyde; Nitrotyrosine; iNOS Abstract: Objective This study investigated the effects of hyperbaric oxygen (HBO) therapy on the cardiovascular alteration (e.g. mean arterial pressure, vascular reactivity of thoracic aorta rings changes) caused by zymosan in rats. Design Rats. Setting University research laboratory. Intervention and measurements We investigated the effects of HBO therapy (2 ATA at the fourth and eleventh hours after study onset) on the cardiovascular alteration caused by zymosan (500 mg/kg, administered i.p. as a suspension in saline) in rats. Cardiovascular alterations were assessed 18 h after administration of zymosan and/or HBO therapy. Results Treatment of rats with HBO therapy attenuated the vasoplegic response to zymosan. In fact, the analysis of arterial pressure curves revealed no signs of vasoplegic shock. The aorta rings of animals treated with zymosan and HBO had a significantly increased contraction to norepinephrine (NE) and endothelin-1 (ET-1) and dilation to acetylcholine (ACh) compared with the zymosan group. The HBO therapy also attenuated the increase of malondialdehyde (MDA) levels caused by zymosan in the aorta. Immunohistochemical analysis for nitrotyrosine and for iNOS revealed positive staining in the aorta from zymosan-treated rats. The degree of staining for nitrotyrosine and iNOS was markedly reduced in tissue sections obtained from zymosan-rats treated with HBO therapy. Conclusion This study provides the first evidence that HBO therapy attenuates the degree of zymosan-induced cardiovascular derangement in the rat. Author Affiliation: (1) Department of Experimental Medicine, Faculty of Medicine, Section of Pharmacology 'L. Donatelli', Second University of Naples, Naples, Italy (2) Department of Clinical and Experimental Medicine and Pharmacology, School of Medicine, Torre Biologica--Policlinico Universitario, Via C. ValeriaUniversity of Messina, 98100, Gazzi, Messina, Italy Article History: Registration Date: 17/12/2003 Received Date: 30/05/2003 Accepted Date: 12/12/2003 Online Date: 12/02/2004 Article note: An editorial regarding this article can be found in the same issue ( http://dx.doi.org/10.1007/s00134-004-2211-y)

Byline: W. Stahl (1), P. Radermacher (1), E. Calzia (1) Keywords: Key words Hyperbaric oxygen therapy; Ventilator; Airway resistance; Gas density Abstract: Objective: To evaluate the function of four currently available, not specifically modified time-cycled ICU ventilators (EVITA 4, Oxylog 2000 HBO and Microvent from Dragerwerk, Germany and Servo 900C, Siemens-Elema, Sweden) under hyperbaric conditions using volume-controlled ventilation (VCV) and, if available, pressure-controlled ventilation (PCV).APDesign: All ventilators were studied on an electromechanical lung simulator consisting of a motor driven bellows (LS 1500, Dragerwerk, Germany) at normobaric (1 bar) and hyperbaric ambient pressures (1.3, 1.6, 1.9, 2.8 bar). Servo 900C and Microvent were additionally tested at 6 bar.APSettings: Hyperbaric chamber.APMeasurements and results: During VCV the tidal volume (V.sub.T) was set at 750 ml at normobaric conditions prior to starting hyperbaric exposure. During PCV the same V.sub.T setting was achieved by adjusting the inspiratory pressure level. At each ambient pressure we registered airway pressure (measured inside the bellows) and flow (derived from the linear displacement of the bellows) for a period of 1 min. From these data we calculated off-line V.sub.T, inspiratory airway peak and plateau pressure (P.sub.peak and P.sub.plateau) and, during PCV only, peak inspiratory flow (V.sub.max) and the time delay between onset of and peak inspiratory flow (V.sub.delay). During VCV inspiratory flow and, consequently, V.sub.T consistently decreased with increasing ambient pressure. In contrast, during PCV V.sub.T remained stable at each condition despite a slight decrease in V.sub.max.APConclusions: Whenever available, PCV should be preferentially used during hyperbaric oxygen therapy due to the stability of ventilator functioning. Based on the specific ventilator properties at increasing ambient pressures, appropriate corrections should be possible which will allow the safe use of ICU ventilators even during VCV. Author Affiliation: (1) Department of Anesthesiology, University Hospital Ulm, Section APV, Parkstrasse 11, D-89073 Ulm, Germany e-mail: Peter.Radermacher@medizin. uni-ulm.de Tel.: + 49-7 31-5 02 51 40 Fax: + 49-7 31-5 02 51 43, DE Article note: Received: 14 June 1999/Final revision received: 18 November 1999/Accepted: 20 January 2000

A study of the relationship of hemodilution, blood viscosity and oxygen content (Ca(sub O2)), and cerebral blood flow (CBF) has revealed that the reduction in Ca(sub O2) after hemodilution is responsible for 40%-60% of the increase in CBF. Previous investigations have yielded inconsistent results due to the difficulty of separating the relative importance of blood viscosity and Ca(sub O2) in controlling CBF after hemodilution. The present study used a different approach in hemodiluted animals, such that Ca(sub O2) was varied without changing blood viscosity. Findings confirm that Ca(sub O2) and blood viscosity are important influences on CBF.

The effects of two methods of pressurization were examined on a thermophilic archaebacterium ES4. To accomplish this, a high-pressure reactor system was developed suitable for simultaneous hyperbaric and hyrostatic pressurization at elevated temperatures. At 95 degrees centigrade with 500 atm, the growth rate of ES4 was significantly higher under hydrostatic pressurization. Elevating the temperature also showed higher growth in the hydrostatic system. The system can be useful in assessing the effects of pressure and other parameters on the growth of deep-sea thermophiles.

Badr, A. E., W. Yin, G. Mychaskiw, and J. H. Zhang. Dual effect of HBO on cerebral infarction in MCAO rats. Am J Physiol Regulatory Integrative Comp Physiol 280: R766-R770, 2001.--Various reports in the literature have shown that hyperbaric oxygen (HBO) reduces cerebral infarction both in animals and humans. After the initial ischemic insult, however, initiating HBO treatment at different intervals has yielded conflicting results. The present study was undertaken to determine the optimal therapeutic window in which to start HBO treatment for cerebral infarction after transient focal ischemia. In this study, the operator occluded the middle cerebral artery (MCA) of anesthetized rats by introducing a blunted nylon filament into the proximal MCA from the dissected external carotid artery. When the operator removed the filament after 2 h, focal ischemia and reperfusion occurred. The operator then placed the rat in the HBO chamber and administered 3 atm absolute HBO for 1 h according to the protocol. The rat was killed 24 h after reperfusion, and the percentage of infarction (infarct ratio) was calculated by dividing the infarction area by the total area of the ipsilateral hemisphere. The results showed that the percentage of infarcted area decreased significantly (P [is less than] 0.05) both in the 3- (7.59%) and 6-h (5.35%) HBO-treatment groups compared with the control (no treatment) group (11.34%). However, the percentage of infarcted area increased significantly (P [is less than] 0.01 and P [is less than] 0.05, respectively) both in the 12- (23%) and 23-h (20%) treatment groups. The results of this study suggest that applying HBO within 6 h of ischemia-reperfusion injury could benefit the patient but that applying HBO 12 h or more after injury could harm the patient. cerebral ischemia; hyperbaric oxygen; infarct ratio