Respiratory care clinics of North America
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Respir Care Clin N Am · Jun 2006
ReviewThe effect of humidification on the incidence of ventilator-associated pneumonia.
Breathing systems used with heated humidifiers are associated with a rapid and high level of bacterial colonization. This colonization is considerably reduced with the use of HMEs. ⋯ The incidence of VAP is not influenced by the type of humidification device (heated humidifier or HME). The incidence of VAP is not affected by the duration of use of HMEs or the type of HME, but prolonging the use of a HME further reduces the risk of cross-contamination and results in considerable cost savings.
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The use of breathing system filters may be particularly beneficial in small infants, compared with older children and adults, because of their greater need for warming and humidification of inspired gases as well as their increased susceptibility to lower respiratory tract contamination. The only evidence available regarding the safety and efficacy of breathing system filters in small infants comes from a few small studies conducted on intensive care patients, however. These studies have suggested that the use of HME filters may be effective in preserving body temperature and airway humidity while decreasing fluid build-up in the breathing system and therefore reducing breathing system contamination. ⋯ Individual institutions will need to formulate policies for the use of breathing system filters for clinical reasons as well as for cost containment or logistical reasons. These policies should be within the frameworks set out by their regulatory agencies. Any problems arising from policies that are in breach of these frame works will remain the responsibility of the individual clinicians caring for these small infants.
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This synopsis of the background to the standardization of medical devices allows a comparison of the functional operation of two regulatory authorities, the FDA and the European Commission. It can be seen that with time they have developed many common features. However, there remains a significant difference with the older style of regulation imposed by the FDA, in particular the obligation to comply with USA Federal Law and Federal Codes of Regulation. ⋯ This paralogism must be countered by the indisputable fact that BSF can significantly increase the work of breath-ing, enlarge the deadspace and even, as has been shown recently, result ina complete blockage of the breathing system. Whatever standards are in place with reference to any particular medical device, it must never be forgotten that it is only the clinician who will finally be accountable for the safe and effective operation of the equipment. While caveat emptor must always be the shibboleth of the purchaser, statutory or advisory regulations are no defense for an incompetent user.
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The efficiency of HMEs decreases with increasing tidal volumes. HMEs always result in an elevation of the inspiratory and expiratory airway resistances; this should be considered especially in cases that involve spontaneous respiration. The pressure drop across HMEs should be less than 2 hPa for a flow of 60 L/min, a level that also has been measured for cascade humidifiers. ⋯ Most of the products that are available on the market are, at best, adequate for anesthetic ventilation or short-term postoperative follow-up ventilation. Generally, this is true of all HMEs that have not been coated with hygroscopic substances. CoatedHMEs have a much better humidification efficiency; however, here too, the existence of substantial differences in quality among the products prohibits an uncritical application.
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Respir Care Clin N Am · Jun 2006
ReviewHumidification of respired gases during mechanical ventilation: mechanical considerations.
Humidification of inspired gases during mechanical ventilation remains a standard of care. Optimal humidity is an elusive target and is not clearly defined in the literature. ⋯ The author's group has used the data reviewed here to modify their previous algorithm for choosing a humidification device (see Fig. 2). Humidification requirements for noninvasive ventilation need further study.