ABSTRACT
Twenty seven patients undergoing elective open heart surgery were included in this prospective study. They were randomly divided into two groups. Group C (n = 12) constituted the control group in whom no breathing filter was used in the anaesthesia circuit in the operating room or in the ICU. Humidification of breathing gases was achieved with the help of conventional heated humidifier. In group F (n = 15), heat and moisture exahanging bacterial / viral filter was incorporated in the breathing circuit at the patient end between the catheter mount and Y connection of the breathing circuit. In both the groups, samples of throat swab, protected broncho-alveolar lavage with double catheter and Ryles tube aspirate were collected preoperatively (in the operation theatre) and postoperatively (in the Intensive Care Unit on day 1). All the samples were sent to the laboratory immediately after the collection for Gram staining and culture and sensitivity. Pathogenic organisms were isolated from a total of 9 patients (33%) preoperatively. Exogenous spread of the organisms to the lungs was considered to have occurred if new pathogenic organisms were isolated from the postoperative bronchoalveolar lavage and the simultaneous samples of the throat swab and Ryles tube did not contain the same organism. By this definition, the exogenous spread of the organisms occurred in one patient in group C and in no patient in group F (P = 0.46, Fishers test). The commonest organisms isolated were Staphylococcus aureus, Klebsiella sp. and Pseudomonas sp. We conclude that colonization of the pathogenic organisms is common (33%) in orophrynx and gastrointestinal tract in hospitalized patients. There was no difference in the exogenous spread of the organisms between the two groups. The unity of the filter, therefore, appears to be limited to prevent contamination of anaesthesia machines or ventilators as has been shown by earlier studies.