Ex vivo water exchange performance and short-term clinical feasibility assessment of newly developed heat and moisture exchangers for pulmonary rehabilitation after total laryngectomy.

Laryngectomized patients suffer from respiratory complaints due to insufficient warming and humidification of inspired air in the upper respiratory tract. Improvement of pulmonary humidification with significant reduction of pulmonary complaints is achieved by the application of a heat and moisture exchanger (HME) over the tracheostoma. The aim of this study was to determine whether the new Provox HMEs (XM-HME and XF-HME) have a better water exchange performance than their predecessors (R-HME and L-HME, respectively; Atos Medical, Hörby, Sweden). The other aim was to assess the short-term clinical feasibility of these HMEs. The XM-HME and XF-HME were weighed at the end of inspiration and at the end of expiration at different breathing volumes produced by a healthy volunteer. The associations between weight changes, breathing volume and absolute humidity were determined using both linear and non-linear mixed effects models. Study-specific questionnaires and tally sheets were used in the clinical feasibility study. The weight change of the XM-HME is 3.6 mg, this is significantly higher than that of the R-HME (2.0 mg). The weight change of the XF-HME (2.0 mg) was not significantly higher than that of the L-HME (1.8 mg). The absolute humidity values of both XM- and XF-HME were significantly higher than that of their predecessors. The clinical feasibility study did not reveal any practical problems over the course of 3 weeks. The XM-HME has a significantly better water exchange performance than its predecessor (R-HME). Both newly designed HMEs did succeed in the clinical feasibility study.

A novel, simplified ex vivo method for measuring water exchange performance of heat and moisture exchangers for tracheostomy application.

BACKGROUND: Breathing through a tracheostomy results in insufficient warming and humidification of inspired air. This loss of air-conditioning can be partially compensated for with the application of a heat and moisture exchanger (HME) over the tracheostomy. In vitro (International Organization for Standardization [ISO] standard 9360-2:2001) and in vivo measurements of the effects of an HME are complex and technically challenging. The aim of this study was to develop a simple method to measure the ex vivo HME performance comparable with previous in vitro and in vivo results. METHODS: HMEs were weighed at the end of inspiration and at the end of expiration at different breathing volumes. Four HMEs (Atos Medical, Hörby, Sweden) with known in vivo humidity and in vitro water loss values were tested. The associations between weight change, volume, and absolute humidity were determined using both linear and non-linear mixed effects models. RESULTS: The rating between the 4 HMEs by weighing correlated with previous intra-tracheal measurements (R(2) = 0.98), and the ISO standard (R(2) = 0.77). CONCLUSIONS: Assessment of the weight change between end of inhalation and end of exhalation is a valid and simple method of measuring the water exchange performance of an HME.

Cost analysis of two anaesthetic machines: "Primus®" and "Zeus®".

BACKGROUND: Two anaesthetic machines, the "Primus®" and the "Zeus®" (Draeger AG, Lübeck, Germany), were subjected to a cost analysis by evaluating the various expenses that go into using each machine. METHODS: These expenses included the acquisition, maintenance, training and device-specific accessory costs. In addition, oxygen, medical air and volatile anaesthetic consumption were determined for each machine. RESULTS: Anaesthesia duration was 278 ± 140 and 208 ± 112 minutes in the Primus® and the Zeus®, respectively. The purchase cost was €3.28 and €4.58 per hour of operation in the Primus® and the Zeus®, respectively. The maintenance cost was €0.90 and €1.20 per hour of operation in the Primus® and the Zeus®, respectively. We found that the O2 cost was €0.015 ± 0.013 and €0.056 ± 0.121 per hour of operation in the Primus® and the Zeus®, respectively. The medical air cost was €0.005 ± 0.003 and €0.016 ± 0.027 per hour of operation in the Primus® and the Zeus®, respectively. The volatile anaesthetic cost was €2.40 ± 2.40 and €4.80 ± 4.80 per hour of operation in the Primus® and the Zeus®, respectively. CONCLUSION: This study showed that the "Zeus®" generates a higher cost per hour of operation compared to the "Primus®".

Infection prevention during anaesthesia ventilation by the use of breathing system filters (BSF): Joint recommendation by German Society of Hospital Hygiene (DGKH) and German Society for Anaesthesiology and Intensive Care (DGAI).

An interdisciplinary working group from the German Society of Hospital Hygiene (DGKH) and the German Society for Anaesthesiology and Intensive Care (DGAI) worked out the following recommendations for infection prevention during anaesthesia by using breathing system filters (BSF). The BSF shall be changed after each patient. The filter retention efficiency for airborne particles is recommended to be >99% (II). The retention performance of BSF for liquids is recommended to be at pressures of at least 60 hPa (=60 mbar) or 20 hPa above the selected maximum ventilation pressure in the anaesthetic system. The anaesthesia breathing system may be used for a period of up to 7 days provided that the functional requirements of the system remain unchanged and the manufacturer states this in the instructions for use.THE BREATHING SYSTEM AND THE MANUAL VENTILATION BAG ARE CHANGED IMMEDIATELY AFTER THE RESPECTIVE ANAESTHESIA IF THE FOLLOWING SITUATION HAS OCCURRED OR IT IS SUSPECTED TO HAVE OCCURRED: Notifiable infectious disease involving the risk of transmission via the breathing system and the manual bag, e.g. tuberculosis, acute viral hepatitis, measles, influenza virus, infection and/or colonisation with a multi-resistant pathogen or upper or lower respiratory tract infections. In case of visible contamination e.g. by blood or in case of defect, it is required that the BSF and also the anaesthesia breathing system is changed and the breathing gas conducting parts of the anaesthesia ventilator are hygienically reprocessed.Observing of the appropriate hand disinfection is very important. All surfaces of the anaesthesia equipment exposed to hand contact must be disinfected after each case.

Effect of thermode application pressure on thermal threshold detection.

Studies using quantitative sensory testing (QST) often present incongruent results due to intra- and intersubject as well as interobserver variability which limit widespread use of the technique. Eliminating or reducing the factors responsible for this variability is of great interest, as it increases reliability and reproducibility of QST. Thermal sensory threshold determination is a crucial part of QST. It was previously suggested that the pressure of the thermode on the skin could influence measurements. To verify this, we developed a new thermode with a built-in pressure sensor. Thresholds obtained with this thermode were compared to those obtained with a commercially available thermotesting device (Medoc TSA-II). Heat detection and heat pain detection thresholds were higher, and cold detection thresholds were lower when measured with our thermode than they were with the Medoc thermode. Cold pain detection thresholds did not differ between the thermodes. Analysis of the heat transfer capacity of the thermodes indicated that the material of the skin contact surface of the thermode may play a role in these shifts in threshold values. Altering the thermode pressure on the skin did not affect the thermal thresholds. Furthermore, the intrasubject variability of the measurements (minimal-to-maximal range of measured threshold values in individual subjects) was also not influenced by the pressure with which the thermode was attached to the skin. Our results suggest that the pressure with which the thermode is attached to the skin does not significantly affect the intra- and intersubject reproducibility of the thermal sensory threshold measurements.

Humidification: measurement and requirements.

Humidification measurement is now feasible, but it is cumbersome and costly for routine use. The user therefore may rely on data supplied with the humidification device and obtained according to ISO standards. For comparison purposes it would be extremely helpful if both standards used to describe humidification properties quoted performance values in the same manner, preferably as moisture loss measured as milligrams of water per liter at the maximum tidal volume. The acceptable water loss should be between 0 and 7 mg/L water depending on the specific situation of the patient.

Evaluation of heated humidifiers for use on intubated patients: a comparative study of humidifying efficiency, flow resistance, and alarm functions using a lung model.

OBJECTIVE: Evaluation of humidification efficiency, flow resistance, and alarm functions of heated humidifiers (HH;(Kendall-Aerodyne-delta, Fisher&Paykel-MR 730; Dräger-Aquapor; Puritan-Bennett-Cascade II) in accordance with ISO/EN-8185:1997 and on a ventilated lung model in accordance with ISO/EN-9360:2000. METHODS: Humidification efficiency was evaluated by (a) measuring the water content of the inspiratory air on perfusion with different gas flows, (b) measuring the water loss of a lung model, and (c) simultaneous measurement of the in- and expiratory water content with a capacitive hybrid sensor. The resistance characteristics were measured, the data were compared with a mathematical approximation. The alarm functions were determined. RESULTS: The humidification efficiency of HHs is a function of gas flow and design characteristics. In HHs with tube heating it is possible to make settings at which the inspiratory humidity falls below the minimal value of 33 mgH(2)O/l stipulated by ISO/EN-8185:1997. The inspiratory resistances extend from 0.5 to 4.4 cmH(2)O l(-1) s(-1); the expiratory flow resistances of the devices are low. The alarm functions of HHs with tube heating are inadequate for cases involving both "dry start" and "running dry." CONCLUSIONS: Efficiency data that allow a direct comparison with heat and moisture exchangers data according to ISO/EN-9360:2000 can also be determined for HH. HH do not prevent pulmonary water losses in intubated patients. These losses can exceed the physiological range. The airway resistance of the Cascade II prohibits its use in spontaneously breathing patients. The warning and shut-off features of HH are unacceptable and hazardous.