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Communications to the Editor |

Defining Dyspnea FREE TO VIEW

Madathil Govindaraj, MD
Author and Funding Information

Affiliations: Calicut, Kerala State, India,  Washington University School of Medicine St. Louis, MO

Correspondence to: Madathil Govindaraj, MD, Caribbean Cottaghe, Wynad Rd, Calicut, Kerala State, 673001, India; e-mail: govindaraj@vsnl.com



Chest. 2002;121(2):662-669. doi:10.1378/chest.121.2.662
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To the Editor:

Roger D. Yusen (February 2001)1 ponders the selection of outcome measures in COPD and recommends that quality of life or, more specifically, health-related quality of life (HRQL) is the appropriate choice. Yusen makes a good case for making generic or disease-specific HRQL the basis of the choice, well ahead of conventional lung function tests. However, before that method of choosing outcome measures becomes a useful reality, more needs to be done, more cobwebs must be cleaned. When we remember that there is no consensus about a definition of dyspnea, and when we realize that there is no way to readily quantify dyspnea, then we understand that talk about HRQL is nothing more than empty counsel aimed at a level of perfection that we cannot measure. Proceeding beyond dyspnea, characteristics such as “fatigue, sleep disturbances, irritability, and a sense of helplessness” are all features that do not easily lend themselves to quantification. When we are guided (and hindered) by such nebulous characteristics, the resulting HRQL inevitably makes for a fragile structure. As Yusen rightly says, “direct measurement of dyspnea and other areas of HRQL” are needed, and this is what we should strive for.

I probed this area 15 years ago, with interviews with two polar groups of subjects with asthma and emphysema, and reported my findings.2 I asked the subjects to express their difficulty in their own words. Further, they were specifically asked whether their distress occurred upon inspiration or upon expiration of breath. The majority of patients with asthma (68%) reported that their difficulty was during inspiration. The emphysematous group, however, could not fix their difficulty in either phase of respiration. Only 11% in this group described dyspnea as inspiratory, as the asthmatic subjects did. They put it variously: “my breathing just stops,”“ I just cannot breathe,” “my breath sticks in my chest,” and so on.

It is true that, as recently as the 1970s, at least three of our most widely read textbooks35 called asthma a disease of inspiratory dyspnea. It is a humbling thought that, until so very recently, our perception of an important dyspneic state was so wide off the mark. We are still a long way from understanding fully the subjective symptom of dyspnea.

What precisely is the role of hyperinflation in the dyspnea of emphysema? When an asthmatic patient experiences an exacerbation, she or he often becomes hyperinflated. How much of the dyspnea is due to airways narrowing, and how much is due to hyperinflation?

We need more information in these gray zones. Roger Yusen rightly makes a plea for direct measurement of dyspnea and other areas of HRQL. Already, surgery has found a place in the therapy of emphysema. Even from our position of imperfect understanding, and our belief that advances in theory are not likely to fetch improvement in management, we should not shy away from seeking more insight. A workable definition of dyspnea and a generally acceptable system of quantifying dyspnea are high priorities.

References

Yusen, RD (2001) What outcomes should be measured in patients with COPD?Chest119,327-328. [PubMed] [CrossRef]
 
Govindaraj, M What is the cause of dyspnea in asthma and emphysema?Ann Allergy1987;59,63-64. [PubMed]
 
Hinshaw, CH Diseases of the chest.1969,332 Igaku Shoin. Tokyo, Japan:
 
Beeson, PB, McDermott, W Textbook of medicine 14th ed.1975,827 Saunders. Philadelphia, PA:
 
Davidson, S Principles and practice of medicine 11th ed.1975,377 Churchill Livingstone. Edinburgh, United Kingdom:
 
To the Editor:

Dr. Govindaraj’s letter emphasizes several important issues about the measurement of dyspnea in patients with COPD. In the context of clinical trials involving patients with COPD, we may struggle with defining what constitutes a successful outcome after an intervention, due to our limited understanding of dyspnea and the enigmatic interactions between major medical interventions and patient perceptions. Use of measured lung function (eg, FEV1) as the sole outcome of clinical trials is not good enough. Although physiologic parameters are relatively easy to follow, they are only surrogate markers of the improvements in dyspnea, functional status, satisfaction, and overall quality of life sought by patients. Too often we determine the success or failure of an intervention based on surrogate of outcomes, and we ignore the outcomes dependent on the perspectives of the patients. We should use physiologic parameters to diagnose illness, assess disease severity, help understand pathophysiology, and validate the subjective outcomes. Subjective outcome measurements provide unique information and, in conjunction with survival data, provide a more comprehensive assessment of medical and surgical interventions.

I agree with Dr. Govindaraj’s points that the appropriate development of instruments used to measure subjective outcomes requires methodologic rigor. The instrument developers should test their instruments for validity, reliability, and responsiveness. The instruments should be refined and retested until they have acceptable operating characteristics. Interestingly, the test performance of some instruments that measure subjective outcomes (eg, dyspnea questionnaires) may be better than the characteristics of other instruments that measure objective outcomes (eg, diffusion capacity of the lung for carbon monoxide) in certain situations (eg, patients with severe COPD). After undergoing appropriate testing and development, objective measurement tools will allow for accurate and precise quantification of subjective outcomes.


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References

Yusen, RD (2001) What outcomes should be measured in patients with COPD?Chest119,327-328. [PubMed] [CrossRef]
 
Govindaraj, M What is the cause of dyspnea in asthma and emphysema?Ann Allergy1987;59,63-64. [PubMed]
 
Hinshaw, CH Diseases of the chest.1969,332 Igaku Shoin. Tokyo, Japan:
 
Beeson, PB, McDermott, W Textbook of medicine 14th ed.1975,827 Saunders. Philadelphia, PA:
 
Davidson, S Principles and practice of medicine 11th ed.1975,377 Churchill Livingstone. Edinburgh, United Kingdom:
 
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