Unrecognized suffering in the ICU: addressing dyspnea in mechanically ventilated patients

Abstract

Background: Intensive care unit (ICU) patients are exposed to many sources of discomfort. Although increasing attention is being given to the detection and treatment of pain, very little is given to the detection and treatment of dyspnea (defined as "breathing discomfort").

Methods: Published information on the prevalence, mechanisms, and potential negative impacts of dyspnea in mechanically ventilated patients are reviewed. The most appropriate tools to detect and quantify dyspnea in ICU patients are also assessed.

Results/conclusions: Growing evidence suggests that dyspnea is a frequent issue in mechanically ventilated ICU patients, is highly associated with anxiety and pain, and is improved in many patients by altering the ventilator settings.

Conclusions: Future studies are needed to better delineate the impact of dyspnea in the ICU and to define diagnostic, monitoring and therapeutic protocols.

Figure 1

Possible reasons for discomfort in mechanically ventilated patients

Figure 2

Modality of dyspnea experienced by ventilated patients (from reference [27]).

Figure 3. Relationship between dyspnea and tidal volume

Data replotted from Mols et al. [34] (left) and Leung et al. [33] (right). Although the authors of both papers reported a difference in respiratory comfort dependent on ventilator mode, these plots suggest that the main effect of changing mode is to change the tidal volume delivered by the ventilator. Consequent changes in pulmonary stretch receptor activity as well as blood gasses are in the correct direction to explain the observed effects on discomfort ratings. PAV, proportional assist ventilation; PSV, pressure-support ventilation; IMV, intermittent mandatory volume ventilation; dyspn unassist, unassisted breathing.