Different Efficiency Of Different Breathing Filters In Mechanical Ventilation

Objective: The aim of this study was to compare the efficiency on the osmosis of liquid and the different filter function of bacteria of four breathing filters(BFs) represented by simple hydrophilic and sponginess adiabator membrane PALL HME 80E(P1),simple hydrophobic and fold filter paper membrane PALL BB 25S(P2),compound membrane DAR 352/5805(D) composed of hydrophilic moist-heat exchange material and static electric dewatering membrane, and compound membrane Vital signs 5708 HEPA(V2) composed of moisture absorption salt material and electret membrane. And further more, we have got information about the influence on the airway temperature and the resistance force of the airway in clinical anesthesia of BFs: Vital signs 5708 HEPA(V2),PALL BB 25S(P2),DAR 352/5805(D) and Vital signs 5702 TMP(V1) composed of simple hydrophilic moisture absorption salt material. We tried to comprehensively evaluate the influence of the mechanical ventilation on the prevention of infection in the airway, temperature maintenance and the respiratory work provided by the above mentioned filters. After these studies we will provide experimental data for the feasibility and security of breathing filters (BF) in clinical application and to promote the clinical application of breathing filters.Methods:1 We tested the membrane of BFs with Sodium Chloride mixed blood plasma whose initial dose was 3 ml, increased 1 ml each time.2 We set up the mechanical model(the imitate lung connected to the distant place of respiration circuit loop, the filter placed between imitate lung and respiration circuit loop). Based on category, the BFs divided into four groups: P1, P2, V2 and D (each group included 18 cases). We tested the efficiency of their bacterial filter by three detected methods (each method included 6 cases): firstly, dropped 1 ml liquid mixed bacterium on the imitate-lung side of the BF; secondly, dropped 11 ml sodium chloride and 1 ml liquid mixed bacterium on the similar position; thirdly, dropped 14 ml sodium chloride and 1 ml liquid mixed bacterium on the similar position. After ventilation for 3 hours (gas flow is 1 L·min-1), with the disinfected method, we took three samples from the imitate-lung side of BF, the breathing circuit side of BF and the Y connectors of the breathing circuit, and cultured for nearly 24 hours.3 To compare the degree of bacterial circuit colonization in intensive care patients using either PALL BB 25S(P2) or DAR 352/5805(D), we choose fifty trachea incision patients undergoing mechanical ventilation for a minimum period of 72 hrs from march to September in 2006. Patients were randomized to two groups and ventilated at lest 24 hours (n=25). Circuit colonization was assessed using semi-quantitative culture of swabs 5 cm from the end of intraductal side of incision of trachea tube, the patient side and the respiration circuit loop of BF, the sample was cultured on blood-agar plate or eosine methylthioninium chloride agar plate for nearly 24 hours. And then bacterium colony was observed and analyzed.4 We investigated patients who had suffered from surgery operation in the department of cerebral surgery, cardia and chest surgery. And we compared the rate of lower breathing system infection between the group P2 (Patients had been used the PALL BB 25S BF during operation.) and group O(Patients had not been used any BF during operation.).5 Seventy five ASAⅠorⅡpatients, aged 18~65 years old, weighing 50~80 kg, operating time about 3 hours, who underwent elective abdominal or pelvic surgery in general anesthesia were enrolled. All patients had no breathing system diseases. All patients were randomly divided into five groups (n=15): P2, D, V1, V2 and control group (O). We recorded the temperature scale of the airway at 0min, 1min, 5min, 30min and 60min after tracheal intubation.6 Sixty ASAⅠ~Ⅲpatients, aged 18~65 years old, weighing 50~80 kg, operating time about 3 hours, who underwent elective abdominal surgery in general anesthesia were enrolled. All patients had no breathing system diseases and heart failure diseases. All patients were randomly divided into four groups (n=15): P2, D, V1 and V2 group. The airway pressure scale was recorded at 5min before applying BF, 5min after applying BF and the finishing time of operation.7 All the data were dealed with the statistical soft of SPSS 13.0. The numeration data were presented as percentage, Fisher exact propability was used to compare the difference between two groups. The quantitative data were presented as mean±standard deviation. Repeated measurement data ANOVA were used to compare the differences of temperature and airway pressure among groups, also used to compare the differences of intragroup. One-way ANOVA was used to compare the differences of different group, but at the same time. T-rest was used to compare the differences between two independent sample means. P<0.05 was considered statistically significant.Results:1 The result of liquid permeation test: Accompanied by liquid dropping, the test liquid was permeating into the membrane of P1 BF. When 12 ml liquid was dropped in, the testing liquid leaked out of the opposite membrane of BF. During the same experiment, the liquid was increasedly accumulated on the membrane of P2 BF, no liquid permeated or leaked out. For the V2 BF, firstly the test liquid permeated, when this liquid added up to 12 ml, the membrane was partly soaked. For the D BF, the test liquid was permeating into the membrane, no liquid leaked out.2 The positive rate of bacterial culture of P1,V2,P2 and D BFs in the sample①was 100%, showing the success of the bacteria culture. And in the sample②and③after imitated ventilation: None of them was positive in first detected method; while in second and third detected method, the results of P1 and V2 were all positive, its positive rate was 100%. No result of P2 and D is positive.3 The results of bacterial culture in ICU: The similar bacterium was cultured in the sample①and②, including respiratory tract normal flora and conditional pathogenic bacteria, its positive rate was 100%, while no bacterium was cultured in the sample③.4 The findings of lower respiratory infection after operation were 1%, 6.7% in group P2 and group O respectively. There was significant difference between two groups(P﹤0.05).5 The temperature influence of different BFs: There was no significant difference among five groups at the 0 min(t1)after intubation(P﹥0.05), but at other time, the airway temperature heightened in experiment group than control group(P﹤0.05). Compared with group P2, the airway temperature of group D, V1 and V2 heightened at the t3,t4 and t5 time(P﹤0.05). But there was no significant difference among group D, V1 and V2 at the same time(P﹥0.05); At the t2 and t3 time, the value of temperature was higher than its former time in the same group(P﹤0.05).6 The airway pressure influence of different BFs: There was no significant difference among four groups at the different time(P﹥0.05). But at the t′2 and t′3 time, the value of airway pressure was higher than its former time in the same group(P﹤0.05).Conclusion:1 When the membrane of simple hydrophilic BF(PALL HME 80E) was kept drying, no bacterium was filtered. But when its membrane was soused, the breathing circuit was seriously contaminated. The membrane of simple hydrophobic BF(PALL BB 25S) is well-hydrophobicity, so no bacterium filtered in either drying or wet condition. The compound membrane of DAR 352/5805 has well-hydrophobicity, just like the membrane of PALL BB 25S thus no bacterium filtered in either drying or wet condition. When the whole membrane of Vital signs 5708 HEPA was kept drying, no bacterium was filtered. But when its membrane accumulated water and airway resistance increased, the bacterium filtered through membrane.2 The further result have achieved that the simple hydrophobic PALL BB 25S BF and compound BF DAR 352/5805 have well bacterial filtration in ICU, and the same result has gotten during retrospective study, Which hinted the group with hydrophobic BF had lower respiratory infection rate after mechanical ventilation.3 During the general anesthesia, BF has well-performance of heat preservation. And BF with hydrophilic material has better function than BF with purely hydrophobic membrane in maintaining airway temperature, which benefits the function of respiratory system. 4 Using BF had little influence on airway pressure. But its change was permitted in clinical practice. The use of BFs could not increase the work of respiratory system.