1. Moisturizing and mechanical characteristics of a new counter-flow type heated humidifier 
S. Schumann, C.A. Stahl, K. Möller, H.-J. Priebe, J. Guttmann 
British Journal of Anaesthesia 
Volume 98, Issue 4, Pages (April 2007)
DOI: /bja/aem006
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

2. Fig 1
Mechanisms of humidification. (a) In the conventional humidifier, water is heated by a plate to produce vapour that is taken up by the gas flowing through the chamber. (b) In the counter-flow-type humidifier, water is heated outside the vaporizer, is pumped to the top of the humidifier, enters the inside of the humidifier through small diameter pores, and then runs down a large surface area. Gas flows in counter direction. During its passage through the chamber of the humidifier, the air is moisturized and warmed to body temperature.
British Journal of Anaesthesia  , DOI: ( /bja/aem006)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

3. Fig 2
(a) Experimental set-up for assessment of humidification performance of the heated humidifiers. A ventilator (Evita 2) delivered volume-controlled ventilation to a moisture-proof physical lung model. (b) Model used for measurements of work of breathing. A ventilator (Evita 2) delivered continuous positive pressure (CPAP). R = bacterial filter. V ˙ = Fleisch pneumotachograph. P = pressure transducer. HME = heat and moisture exchanger. (c) Model used for measurements of mechanical impedance. The lung simulator delivered a sinusoidal flow. V ˙ = Fleisch pneumotachograph. P = pressure transducer. HME = heat and moisture exchanger.
British Journal of Anaesthesia  , DOI: ( /bja/aem006)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

4. Fig 3
(a) Physical work exhibited by the counter-flow type (HC200), the conventional (MR850), and the passive humidifier (HME) during inspiration. Bars and whiskers are means (sd). *P < between all humidifiers. (b) Additional PTP (PTPadd) produced by the humidifiers during inspiration. Bars and whiskers are means (sd). #P < 0.05 passive humidifier (HME) compared with both heated humidifiers (HC200 and MR850).
British Journal of Anaesthesia  , DOI: ( /bja/aem006)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

5. Fig 4
Resistances of the heated humidifiers at low (a) and high flow (b) rates. Values are means (sd). −, absent tubing system; +, present tubing system. *P = 0.047, #P = §P < between humidifiers. Please note different scales on y-axis of both diagrams.
British Journal of Anaesthesia  , DOI: ( /bja/aem006)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions