Although respiratory discomfort (dyspnea) is as common as pain in seriously ill patients,1 there is no formal requirement to assess and manage it, such as the “fifth vital sign” requirement for pain assessment and management.
Mechanical ventilation is the most frequently used life-support measure in the intensive care unit (ICU). It is also used during anesthesia and the initial phase of postanesthesia awakening, and at home in patients with chronic respiratory failure. Many patients who are mechanically ventilated are thus conscious (or even fully awake), yet they can experience rapid and important changes in their respiratory status and metabolic needs. It is thus not surprising that ventilated patients do experience respiratory discomfort. They can report and quantify it, and there are strategies to address it. In this chapter we (a) propose that respiratory discomfort be routinely assessed in ventilated patients, and (b) suggest some approaches to managing this discomfort with minimal sedation. Together, these could be termed patient-centered ventilation.2 There is, however, a paucity of studies directly addressing prevalence, outcomes, and mechanisms of dyspnea and its relief in acutely ventilated patients.
Although we lack large-scale studies on the prevalence of dyspnea in mechanical ventilation, there have been a few studies in which a small sample of acutely ventilated patients have been asked to rate dyspnea.3–8 In three studies the severity of dyspnea was stratified: In a combined total of 204 patients, 19% of the respondents reported moderate to severe discomfort.3,6,7 In one study, patients were asked to characterize the quality of their discomfort: 69% reported experiencing air hunger; 51% reported excessive work/effort. About a third of the foregoing patients experienced both air hunger and work/effort.7 In another study, 29% of ventilated patients recalled after their stay in the ICU that they had been moderately to extremely bothered by not getting enough air from the endotracheal tube, which we equate to air hunger.9 Many patients, however, were too heavily sedated to respond; many of these latter patients had probably been heavily sedated in an attempt to alleviate respiratory discomfort. This clearly indicates that there is a problem to address. As discussed below, heavy sedation is not necessarily an adequate solution and may be harmful.
There is a clear association between anxiety and dyspnea in patients.10–12 In laboratory subjects, experimentally induced air hunger produces more discomfort and more anxiety than tasks that require a great deal of respiratory work and effort.13 In critically ill patients, emotional reactions such as panic, anxiety, and fear are significantly correlated with patient–ventilator dyssynchrony.14 Dyspnea can cause anxiety, even in healthy subjects who experience dyspnea in a safe laboratory situation.13,15,16 Conversely, anxiety can cause dyspnea. This is true even in the absence of cardiopulmonary pathology; for example, dyspnea is the most common symptom in anxiety and panic disorders.17 Because of this reciprocal ...