Within the last 2 years much information has become available regarding VAP? Reduce breaking the circuit, draining away from the heater, use of inline suction, inline MDI, and use of OETT which can allow for suction of hypopharynx, and the use of bacteria filters/HME's. In the last year our CVU has all but done away with active humidification. The CVU has a very fast attrition rate for patient stay. Patients are fast tracked and are out next day in most cases. There are a few who are failure to thrive and difficult to wean patients. The policy with our short term vents thus far seems to be no active humidity but the use of antimicrobial hme such as PAL. Something efficacious at .3 mcs anyway.

Up until more recently for longer term patients over 36 hours on a vent and we switch to active humidity. With the new data on VAP our site will be switching out active humidity all together and running HMEs. Apparently our average length of stay in ICU is 3.3 days, seeing these as our longer term patients the idea of active humidity seems a waste of resources and an increase in source of infection.

Have other sites gone this way? What has been the experience? Are you finding any difference in secretion productivity such that it is? Are secretions dryer? Any problems with tube blockages? According to our manager the data shows actually less incidence of tube trouble with HMEs vs. Active humidity? What are your thoughts?

Oh yeah and how often are you changing them? We have decided without obvious complications that 36 hours would provide maximal coverage.

Having recently reviewed the AARC web resources on special articles I did find current data related to passive humidification. Thankyou for your attention to this question but it seems many have gone before on this one.

Incidently what is your opinion?

Check out the study..

"
Published ahead of print on July 21, 2004, doi:10.1164/rccm.200309-1245OC
This Article

American Journal of Respiratory and Critical Care Medicine Vol 170. pp. 1073-1079, (2004)
© 2004 American Thoracic Society
doi: 10.1164/rccm.200309-1245OC

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Original Article

Influence of Ambient and Ventilator Output Temperatures on Performance of Heated-Wire Humidifiers
François Lellouche, Solenne Taillé, Salvatore M. Maggiore, Siham Qader, Erwan L'Her, Nicolas Deye and Laurent Brochard
Service de Réanimation Médicale, Hôpital Henri Mondor, INSERM U492, Université Paris XII Créteil, France; and Istituto di Anestesiologia e Rianimazione, Università Cattolica Policlinico A. Gemelli, Rome, Italy

Correspondence and requests for reprints should be addressed to Laurent Brochard, M.D., Service de Réanimation Médicale, Hôpital Henri Mondor, 51 Avenue du Maréchal de Lattre de Tassigy, 94010 Créteil, France. E-mail: laurent.brochard@hmn.ap-hop-paris.fr

Although heated humidifiers are considered the most efficient humidification devices for mechanical ventilation, endotracheal tube occlusion caused by dry secretions has been reported with heated-wire humidifiers. We tested the hypothesis that inlet chamber temperature, influenced by ambient air and ventilator output temperatures, may affect humidifier performance, as assessed by hygrometry. Hygrometry was measured with three different humidifiers under several conditions, varying ambient air temperatures (high, 28–30˚C; and normal, 22–24˚C), ventilators with different gas temperatures, and two E levels. Clinical measurements were performed to confirm bench measurements. Humidifier performance was strongly correlated with inlet chamber temperature in both the bench (p < 0.0001, r2 = 0.93) and the clinical study. With unfavorable conditions, absolute humidity of inspired gas was much lower than recommended (approximately 20 mg H2O/L). Performance was improved by specific settings or new compensatory algorithms. Hygrometry could be evaluated from condensation on the wall chamber only when ambient air temperature was normal but not with high air temperature. An increase in inlet chamber temperature induced by high ambient temperature markedly reduces the performance of heated-wire humidifiers, leading to a risk of endotracheal tube occlusion. Such systems should be avoided in these conditions unless automatic compensation algorithms are used. "

I have a PDF of this and can send it to anyone whom requests. whitnack@pacbell.net

I also have a list of studies, as well as a survey I did about what humidification "rituals" are in existence (can also include). Offhand I'd estimate that about 50% of hospitals use some mixed forumula (3 days HME then switch to active humidificaiton--usually heated wire). Others (about 25% each I'd estimate) use exclusively either HME or active humidification (usually heated wire, but might be non-heated wire with target less than 37 degrees).

One issue is whether or not it is a valid clinical goal to achieve gas at 100% RH and 37 degrees at the carina. One camp says that critically ill patients benefit from not having to make up any humidity deficit. Another camp says the airways normally participate in giving up and taking back humidity, and that "subverting" this might be harmful. Then some propenents of active humidity favor active humidification targeted to 30-32 degrees and WITHOUT heated wires. The proponents of various routines have a lot of money to be made or lost on the table.

There doesn't seem to be any big "smoking gun" either favoring or decrying any one ritual. But bear in mind that heated wire circuits can actually (and ironically) cause a greater humidity deficit if what is sent to the patient is both hot and dry air. Better for the airway to receive cooler air which is 100% RH---so that it can heat and moisten up as it traverses down, as opposed to a sudden onslaught of heated and dry air--which mandates an immmediate dessication.