Refractory breathlessness: Mechanisms and management
Chronic refractory breathlessness, defined as breathlessness that persists at rest or on minimal exertion despite optimising the treatment of any underlying causes that has persisted daily for more than three of the last six months, is highly prevalent across our community. A great deal of suffering results as a consequence of such breathlessness when it remains unrelieved.
The dominant paradigm would suggest that the mechanism is ultimately a mismatch between input into breathing, and the body's ability to respond. Such a stimulus can be peripheral (restriction of chest movement, stretch receptors in lung parenchyma peripheral chemo-receptors) or central input (central chemo-receptors, cognitive input). Any factor that limits the ability to respond adequately to the insult will result in the subjective sensation of breathlessness.
The evidence for the symptomatic management of chronic refractory breathlessness has developed rapidly in the last decade. The gold-standard measure is either a visual analogue scale, a numerical rating scale, a Borg scale or a Likert scale. These need to be anchored for both the (severity) intensity and an affective component (unpleasantness) of breathlessness. The minimally clinically important difference in the reduction of chronic breathlessness on a visual analogue scale has been defined. A moderate response would be 11mm on a 100mm scale.
Systemic opioids have a strong evidence base to ensure the safe reduction in breathlessness with benefits maintained over long periods of time. When adequately titrated, oral sustained release opioids are going to predictably help the majority of patients in whom they have started. For people already on opioids for other reasons the dose will need to be adjusted by 25% over baseline in order to achieve symptomatic benefit.
Other medications being studied include nebulised opioids and nebulised frusemide. Non-pharmacological interventions include a number of evidence-based cognitive and physical interventions.