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This study investigates the characteristics of human exhalation through the mouth with three different ventilation strategies: displacement ventilation, mixing ventilation and without ventilation. Experiments were conducted with one breathing thermal manikin in a full scale test room where the exhalation airflow was analyzed. In order to simulate the gaseous exhaled substances in human breathing, N2O was used as a tracer gas. The concentration of N2O and the velocity of the exhaled flow were measured in the center line of the exhalation flow. The velocity decay of the exhalation flow versus distance was analyzed for the three ventilation strategies. The relationship between gas concentration values and distance from the manikin was also examined. The measurements show distribution system. Two equations could be applied to describe the relationship between distance from the manikin and, respectively, peak velocity values and maximum mean gas-concentration values. This study investigates the characteristics of human exhalation through the mouth with three different ventilation strategies: displacement ventilation, mixing ventilation and without ventilation. Experiments were conducted with one breathing thermal manikin in a full scale test room where the exhalation airflow was analyzed. In order to simulate the gaseous exhaled substances in human breathing, N2O was used as a tracer gas. The concentration of N2O and the velocity of the exhaled flow were measured in the center line of the exhalation flow. The velocity decay of the exhalation flow versus distance was analyzed for the three ventilation strategies. The relationship between gas concentration values and distance from the manikin was also examined. The measurements show distribution system. Two equations could be applied to describe the relationship between distance from the manikin and, respectively, peak velocity values and maximum mean gas-concentration values.

Introduction. Pseudomonas aeruginosa is one of the important causes of hospital-acquired infections in Intensive Care Unit (ICU) and considered as a major determinant of morbidity and mortality in patients affected by cystic fibrosis (CF). The aim of this study was to investigate clonal diversity among randomly picked P. aeruginosa isolates of CF and the other hospitalized patients in ICU. Methods. Cultivation, identification, and antimicrobial suscep- tibility testing of P. aeruginosa isolates were performed using standard techniques. The genetic similarity of the strains was investigated by amplification of the Enterobacterial Repetitive Intergenic Consensus-polymerase chain reaction (ERIC-PCR) sequence. Results and discussion. Among 49 isolates, sixteen were isolated from 11 patients affected by CF and 33 came from an epidemiologi- cal investigation of 25 P. aeruginosa infected patients of ICU. Five clusters were generated for all isolates analyzed through ERIC-PCR genotyping. Two major clusters (B and C) were discovered in P. aer- uginosa isolates of ICU and CF patients during the whole period of this study. Fifteen unique antibiogram patterns obtained from all iso- lates and multi-resistant P. aeruginosa (MRPA) were identified in 23 isolates (47%). MRPA isolates were detected in all clusters (except A) while pan-resistant isolates were recovered only in cluster C. The high prevalence of related or identical isolates in CF and non-CF patients can be due to transmission of particular domi- nant clones in ICU ward. Therefore, enhanced infection-control may become necessary to prevent further spread of clonal strains., Journal of Preventive Medicine and Hygiene, Vol 54, No 1 (2013)