Use Of Heat And Moisture Exchanger Research Articles

Prolonged use of heat and moisture exchangers does not affect device efficiency or frequency rate of nosocomial pneumonia

To determine whether use of a single heat and moisture exchanger (HME) for < or =120 hrs affects efficiency, resistance, level of bacterial colonization, frequency rate of nosocomial pneumonia, and cost compared with changing the HME every 24 hrs. Prospective, controlled, randomized, unblinded study. Surgical intensive care unit at a university teaching hospital. A total of 220 consecutive patients requiring mechanical ventilation for >48 hrs. Patients were randomized to one of three groups: a) hygroscopic HME (Aqua+) changed every 24 hrs (HHME-24); b) hydrophobic HME (Duration HME) changed every 120 hrs (HME-120); and c) hygroscopic HME (Aqua+) changed every 120 hrs (HHME-120). Devices in all groups could be changed at the discretion of the staff when signs of occlusion or increased resistance were identified. Daily measurements of inspired gas temperature, inspired relative humidity, and device resistance were made. Additionally, daily cultures of the patient side of the device were accomplished. The frequency rate of nosocomial pneumonia was made by using clinical criteria. Ventilatory support variables, airway care, device costs, and clinical indicators of humidification efficiency (sputum volume, sputum efficiency) were also recorded. Prolonged use of both hygroscopic and hydrophobic devices did not diminish efficiency or increase resistance. There was no difference in the number of colony-forming units from device cultures over the 5-day period and no difference between colony-forming units in devices changed every 24 hrs compared with devices changed after 120 hrs. The average duration of use was 23+/-4 hrs in the HHME-24 group, 73+/-13 hrs in the HME-120 group, and 74+/-9 hrs in the HHME-120 group. Mean absolute humidity was greater for the hygroscopic devices (30.4+/-1.1 mg of H2O/L) compared with the hydrophobic devices (27.8+/-1.3 mg of H2O/L). The frequency rate of nosocomial pneumonia was 8% (8:100) in the HHME-24 group, 8.3% (5:60) in the HME-120 group, and 6.6% (4:60) in the HHME-120 group. Pneumonia rates per 1000 ventilatory support days were 20:1000 in the HHME-24 group, 20.8:1000 in the HME-120 group, and 16.6:1000 in the HHME-120 group. Costs per day were $3.24 for the HHME-24 group, $2.98 for the HME-120 group, and $1.65 for the HHME-120 group. Changing the hydrophobic or hygroscopic HME after 3 days does not diminish efficiency, increase resistance, or alter bacterial colonization. The frequency rate of nosocomial pneumonia was also unchanged. Use of HMEs for >24 hrs, up to 72 hrs, is safe and cost effective.

Changing heat and moisture exchangers after 96 hours rather than after 24 hours: a clinical and microbiological evaluation.

The aim of this study was to determine whether changing heat and moisture exchangers (HMEs) every 96 hrs rather than 24 hrs would affect their efficacy to preserve the heat and moisture of inspiratory gases. The impact of a prolonged use of the HME on its microbial colonization was also assessed. Prospective cohort observational study. Intensive care unit of a university hospital. Thirteen consecutive patients with no previous history of respiratory disease requiring controlled mechanical ventilation with an HME for >4 days were evaluated. The same HME was used for 96 hrs in each patient. In each patient, during the inspiration phase, the following measurements were performed: peak and mean airway pressures, mean values of temperature, and relative and absolute humidity of inspired gases. In each patient, measurements were performed after 1 hr of HME use and then daily up to the fourth day. On days 1 and 4, microbiological samples were obtained from the patients' bronchial secretions and the ventilator side of the HME. After 96 hrs of ventilation with the same HME, tracheal tube occlusion was never observed. Using the same HME for 96 hrs rather than 24 hrs did not affect its technical performances: temperature at 24 hrs: 32.2 +/- 1.5 degrees C (90.0 +/- 34.7 degrees F), at 96 hrs: 32.1 +/- 1.6 degrees C (89.8 +/- 34.9 degrees F); relative humidity at 24 hrs: 97.9 +/- 2%, at 96 hrs: 98.1 +/- 1.7%; absolute humidity at 24 hrs: 33.1 +/- 2.4 mg H2O/L, at 96 hrs: 33.0 +/- 2.5 mg H2O/L. This analysis was based on a total of 312 measurements performed on the 13 patients. Peak and mean airway pressures did not change during the 96-hr study period, with identical tidal and minute volumes in the study patients. On day 1, ten patients had a positive culture of their tracheal secretions at a colony count of > or = 10(3) colony forming units/mL. After 96 hrs of use with the same HME, only seven patients had a positive culture of their tracheal secretions. Cultures from the ventilator sides of the HMEs were all sterile (13/13) after 96 hrs of use. In patients free from previous chronic respiratory disorder and ventilated for neurologic reasons, changing the HME after 96 hrs rather than 24 hrs did not affect its technical performance in terms of heat and water preservation of ventilatory gases. There is also some indirect evidence of very little, if any, changes in the HME resistance. No bacterial colonization of the ventilator sides of the HMEs was observed after 96 hrs of use. However, other large clinical trials should be undertaken to confirm the safety of extending the time between HME changes.

Study of Humidification Potential of a Heat and Moisture Exchanger in Tracheotomized Dogs

Though a heat and moisture exchanger (HME) has been used in clinical practice following a tracheotomy on a limited basis, no work has been done to document the humidification potential of an HME in this situation. Eighteen dogs underwent tracheotomy and were killed at either 1 day (nine dogs) or 10 days (nine dogs) postoperatively. Following the tracheotomy, the animals were divided into three groups according to the type of humidification received: ambient conditions, warm mist, or HME. The tracheal mucosa was studied for histologic changes in the cilia, the epithelium, submucosal reaction, and mucus production at the level of the carina. The results were significant (p = .02) for the interaction of the experimental type and method of treatment in their effect on the histologic changes noted at the carina. The study supports the use of an HME as an alternative for long-term humidification in a patient with a tracheotomy.