The situation regarding hygiene of HVC is slightly different in obstructive respiratory diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) compared with restrictive respiratory diseases. The major reason for this difference is a higher sensitivity to bacterial colonization of the airways in these patient populations. The rate of airway colonization often correlates with the severity and/or speed of obstructive disease progression. In addition, there is evidence that the need for noninvasive ventilation becomes more frequent after airway colonization in these patients.

Ventilator-associated pneumonia is well documented. In intensive care units, the use of mechanical ventilation is an important risk factor for the development of nosocomial pneumonia. Moreover, current risk is greater with the use of invasive mechanical ventilation compared with noninvasive ventilation. Unfortunately, the relationship between the use of noninvasive ventilation and an increased risk for nosocomial pneumonia is not demonstrated.

The greater number of manipulations and the presence of an endotracheal tube associated with invasive ventilation contribute to HVC contamination. It can be hypothesized that manipulations related to noninvasive ventilation also represent a potential risk for contamination. This implies a rigorous implementation of classical nonspecific rules of hygiene, including hand washing. Nevertheless, the ventilator, the circuit, and the interface do not represent major risk factors for contamination and colonization, but monitoring potential bacterial contamination of devices and paying attention to the basic rules of hygiene probably remain important challenges.

There is little published research to support the relationship between hygiene and noninvasive ventilation devices in obstructive diseases. In a small study on cystic fibrosis patients (particularly at risk of cross contamination), no evidence was found of pathogenic microbial contamination of NIV devices [6]. However, we can extrapolate findings from therapies such as respiratory physiotherapy devices to patients with obstructive disorders receiving long-term noninvasive ventilation. Indeed, the material involved in noninvasive ventilation is part of the semi-critical devices that are in contact with mucus membranes as defined by the Centers for Disease Control and Prevention. Fortunately, recommendations on hygiene of these devices are available.

In patients affected by CF and other chronic respiratory diseases, nebulizers are considered potential vectors of bacterial infection of airways. Notably, studies showed that nebulizers of CF patients are frequently contaminated [7]. Similarly, it was suggested that nebulizers can lead to nosocomial disease in COPD patients [8]. The bacterial contamination of HVC is related to the duration of its use and the airway colonization of the patient.

Based on this evidence, several recommendations were proposed and could be applied to the pieces of the circuit involved in noninvasive ventilation in obstructive diseases. As shown in Table 9.1, regular cleaning of HVC and masks is mandatory, at least as a basic hygiene procedure and, more specifically, to eliminate the biofilm deposited on the surfaces that further decreases the efficacy of disinfectants [9]. The necessary frequency of cleaning is still being debated. Based on the results of studies on nebulizers, a daily cleaning could theoretically be the recommended timing. However, a less regular cleaning, for instance, once a week, could be acceptable in the practice. The possibility of using tap water for cleaning must be taken into account whether HVC are contaminated by S. marcescens and Stenotrophomonas maltophila.

When considering disinfection, different methods may be proposed. The choice of the optimal method largely depends on the material chosen to disinfect. A thermal disinfection (e.g., sterilizer, boiling water) may be not suitable for some non-thermo-stable pieces of HVC even though its efficacy is evident with all germs. There are a number of chemical methods and each one has its own characteristics. The duration of soaking and the concentration of the chemical depend on the particular substance used, and the guidelines for each must be followed carefully. Acetic acid is not recommended due to its inefficacy on gram-positive and gram-negative bacteria [10, 11]. In contrast with acid acetic, hypochlorite solution (20 min of soaking in a concentration of 0.5 %) may be the best alternative of those readily available chemical solutions.