In vitro evaluation of an active heat-and-moisture exchanger: the Hygrovent Gold.

BACKGROUND: To improve the heat and humidification that can be achieved with a heat-and-moisture exchanger (HME), a hybrid active (ie, adds heat and water) HME, the Hygrovent Gold, was developed. We evaluated in vitro the performance of the Hygrovent Gold. METHODS: We tested the Hygrovent Gold (with and without its supplemental heat and moisture options activated), the Hygrobac, and the Hygrovent S. We measured the absolute humidity, using a test lung ventilated at minute volumes of 5, 10, and 15 L/min, in normothermic (expired temperature 34 degrees C) and hypothermic (expired temperature 28 degrees C) conditions. We also measured the HMEs' flow resistance and weight after 24 h and 48 h. RESULTS: In its active mode the Hygrovent Gold provided the highest absolute humidity, independent of minute volume, in both normothermia and hypothermia. The respective normothermia and hypothermia absolute humidity values at 10 L/min were 36.3 + 1.3 mg/L and 27.1 + 1.0 mg/L with the active Hygrovent Gold, 33.9 + 0.5 mg/L and 24.2 + 0.8 mg/L with the passive Hygrovent Gold, 33.8 + 0.56 mg/L and 24.4 + 0.4 mg/L with the Hygrobac, and 33.9 + 0.8 mg/L and 24.6 + 0.6 mg/L with the Hygrovent S. The efficiency of the tested HMEs did not change over time. At 24 h and 48 h the increase in weight and flow resistance was highest in the active Hygrovent Gold. CONCLUSIONS: The passive Hygrovent Gold provided adequate heat and moisture in normothermia, but the active Hygrovent Gold provided the highest humidity, in both normothermia and hypothermia.

Performance of heated wire humidifiers: an in vitro study.

PURPOSE: We assessed the performance of heated wire humidifiers (HWHs), which should avoid water condensation in the circuit. METHODS: We evaluated the efficiency of 3 HWHs, MR850 (Fisher & Paykel, Auckland, New Zealand), CONCHATHERM IV (Hudson RCI, Temecula, Calif), and DAR HC 2000 (Mallinckrodt DAR, Mirandola, Italy), in comparison with that of the MR730 heated humidifier (HH), which has a standard circuit. We measured gas temperature and absolute humidity (AH) at the Y piece of the ventilatory circuit using a test lung ventilated at 2 minute ventilation volumes (5 and 15 L/min). Temperature levels at the Y piece of the ventilatory circuit of the HHs were set at 35 degrees C, 37 degrees C, and 39 degrees C with different gradients (-2 degrees C, 0 degrees C, and +2 degrees C) between the outlet chamber and the Y piece of the ventilatory circuit. RESULTS: At the set temperature levels of 35 degrees C, 37 degrees C, and 39 degrees C with a gradient of 0 degrees C, the MR850 and CONCHATHERM IV had lower gas temperature and AH levels as compared with the DAR HC 2000 and MR730 HH. With increasing temperature gradient, gas temperature increased only with the CONCHATHERM IV but AH increased with all the HWHs. The MR850 showed lower gas temperature and AH levels as compared with CONCHATHERM IV. The condensate was abolished inside the inspiratory circuit with the HWHs. CONCLUSIONS: Heated wire humidifiers eliminate water condensation but present significant differences in gas temperature and AH levels that are lower than the expected settings.

In vitro and in vivo evaluation of a new active heat moisture exchanger.

INTRODUCTION: In order to improve the efficiency of heat moisture exchangers (HMEs), new hybrid humidifiers (active HMEs) that add water and heat to HMEs have been developed. In this study we evaluated the efficiency, both in vitro and in vivo, of a new active HME (the Performer; StarMed, Mirandola, Italy) as compared with that of existing HMEs (Hygroster and Hygrobac; Mallinckrodt, Mirandola, Italy). METHODS: We tested the efficiency by measuring the temperature and absolute humidity (AH) in vitro using a test lung ventilated at three levels of minute ventilation (5, 10 and 15 l/min) and at two tidal volumes (0.5 and 1 l), and in vivo in 42 patients with acute lung injury (arterial oxygen tension/fractional inspired oxygen ratio 283 +/- 72 mmHg). We also evaluated the efficiency in vivo after 12 hours. RESULTS: In vitro, passive Performer and Hygrobac had higher airway temperature and AH (29.2 +/- 0.7 degrees C and 29.2 +/- 0.5 degrees C, [P < 0.05]; AH: 28.9 +/- 1.6 mgH2O/l and 28.1 +/- 0.8 mgH2O/l, [P < 0.05]) than did Hygroster (airway temperature: 28.1 +/- 0.3 degrees C [P < 0.05]; AH: 27 +/- 1.2 mgH2O/l [P < 0.05]). Both devices suffered a loss of efficiency at the highest minute ventilation and tidal volume, and at the lowest minute ventilation. Active Performer had higher airway temperature and AH (31.9 +/- 0.3 degrees C and 34.3 +/- 0.6 mgH2O/l; [P < 0.05]) than did Hygrobac and Hygroster, and was not influenced by minute ventilation or tidal volume. In vivo, the efficiency of passive Performer was similar to that of Hygrobac but better than Hygroster, whereas Active Performer was better than both. The active Performer exhibited good efficiency when used for up to 12 hours in vivo. CONCLUSION: This study showed that active Performer may provide adequate conditioning of inspired gases, both as a passive and as an active device.

A systematic review of the antifungal effectiveness and tolerability of amphotericin B formulations.

OBJECTIVE: A systematic review was performed to compare the effectiveness and tolerability of lipid-based amphotericin B (AmB) formulations and conventional AmB in the treatment of systemic fungal infections. METHODS: The literature and unpublished studies were searched using MEDLINE, EMBASE, Biological Abstracts, AIDSLINE, CANCERLIT, CRD database, Cochrane Controlled Trials Register, and other databases. Search terms included: amphotericin, liposom*, lipid*, colloid*, antifungal agents, and mycoses. Studies were selected according to predetermined criteria. The outcome measures reviewed were efficacy, mortality, renal toxicity, and infusion-related reactions. Meta-analyses and number-needed-to-treat (NNT) analyses were performed. RESULTS: Seven studies (8 publications) met the entry criteria. Meta-analysis showed that lipid-based formulations significantly reduced all-cause mortality risk by an estimated 28% compared with conventional AmB (odds ratio [OR], 0.72; 95% CI, 0.54 to 0.97). There was no significant difference in efficacy between the lipid-based formulations and conventional AmB (OR, 1.21; 95% CI, 0.98 to 1.49). AmB lipid complex (ABLC) and liposomal AmB (L-AmB) significantly reduced the risk of doubling serum creatinine by an estimated 58% (OR, 0.42; 95% CI, 0.33 to 0.54). There was no significant reduction in risk of infusion-related reactions with lipid-based formulations, although this was difficult to interpret given the lack of consistent control of confounding factors. Comparing the lipid-based formulations with conventional AmB, the overall NNT to prevent 1 death was 31. The NNT to prevent a doubling of serum creatinine for both ABLC and L-AmB compared with conventional AmB was 6. CONCLUSIONS: This study demonstrates advantages with lipid-based formulations over conventional AmB in terms of reduced risk of mortality and renal toxicity. Future trials in patients with proven fungal infection should control for factors such as premedication, infusion rates, fluid preloading, sodium/potassium supplementation, and concomitant medication.

Influence of albumin supplementation on tacrolimus and cyclosporine therapy early after liver transplantation.

Liver transplant recipients administered gelatin (GEL) rather than human albumin solution (HAS) can become profoundly hypoalbuminemic in the early postoperative period and often have hepatic dysfunction at this time. The combined effect of these two abnormalities could be an increase in the unbound (active) concentration of low-extraction highly albumin-bound drugs, such as tacrolimus (TAC). This may increase the efficacy and/or toxicity of such drugs. We prospectively compared the clinical outcome of 69 de novo liver transplant recipients randomized primarily to TAC or cyclosporine (CYA) and secondarily to HAS or GEL therapy during the first 14 days after liver transplantation. Antipyrine clearance on the 7th postoperative day was used as a measure of liver metabolic function. Serum albumin levels were significantly lower in both GEL arms than HAS arms during the first 14 days (P <.001). Although antipyrine clearance was similar in all four trial arms, it was intermediate between that found in historic healthy controls and patients with cirrhosis (P <.0001). Serum creatinine concentrations were significantly greater in the TAC plus GEL arm than the other three arms (P <.001). The linearized treated acute rejection rate was significantly greater in the TAC plus HAS arm than the other three arms (relative risk, 2.02; 95% confidence interval, 1.07 to 3.78; P =.03). These data indicate that excess nephrotoxicity can occur with TAC in liver transplant recipients with impaired hepatic metabolism who are administered GEL. In addition, supplementary albumin may reduce the efficacy of TAC in liver transplant recipients at a time when the risk for rejection is greatest.