Measuring Shortness of Breath in COPD

Score-based tool measures disability caused by dyspnea

Patient consulting Doctor for breathing difficulties, Asthma
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Dyspnea is the medical term used to describe a person's shortness of breath, the symptom considered central to all forms of chronic obstructive pulmonary disease (COPD), including emphysema or chronic bronchitis. We evaluate dyspnea to determine how much the disease has affected our ability to function and what we might expect moving forward.

From a clinical standpoint, the problem with dyspnea is that is very subjective.

While one person may experience little shortness of breath with a certain activity, another may feel completely winded. The same variations can occur from one day to the next.

Even a person's perception of dyspnea can determine how they react to it. Persons who respond to their symptoms with high levels of anxiety will tend to experience it "worse" and function far less well than someone who is less anxious.

Because of this, pulmonologists will use a tool called an MMRC Dyspnea Scale to quantify how shortness of breath causes disability rather than how "bad" or "good" it is.

Understanding the MMRC Dyspnea

The challenge of measuring dyspnea is that a more a sensation than an objective value. While you can measure the volume of air a person can inhale, for example, you can't measure how "short" that person is of breath. It is a sensation as much as pain is a sensation.

There are certainly a number of objective tests we use to evaluate COPD, such as spirometry to measure the forcefulness of a person's breath and pulse oximetry to measure blood oxygen levels.

However, from the standpoint of dyspnea, we need to take a different approach.

So, rather than defining the sensation, we instead describe it in terms of degrees of disabilities when faced with certain everyday activities.

In order to standardize the evaluation, we use a simple, five-option grading system called the Modified Medical Research Council (MMRC) Dyspnea Scale.

The scale measures a person's limitation base on a scale of 0-4 and uses the final value to determine how much disability is caused by shortness of breath.

GradeDescription of Breathlessness
0I only get breathless with strenuous exercise.
1I get short of breath when hurrying on level ground or walking up a slight hill.
2On level ground, I walk slower than people of the same age because of breathlessness or have to stop for breath when walking at my own pace.
3I stop for breath after walking about 100 yards or after a few minutes on level ground.
4I am too breathless to leave the house, or I am breathless when dressing.

Role of the Dyspnea Evaluation

The MMRC Dyspnea Scale has proven invaluable in the field of pulmonary by allowing doctors and researchers to:

  • Assess the effectiveness of medications and pulmonary rehabilitation on an individual basis
  • Compare the effectiveness of treatment approaches within a population
  • Predict survival rate as part of the BODE index

From a clinical viewpoint, the MMRC scale correlates fairly well with such objective measures as pulmonary function tests and walk tests. The values also tend to be stable over time, meaning that they are less prone to subjective variability than one might assume.

Using the BODE Index to Estimate Survival

The MMRC Dyspnea Scale is used calculate BODE index, a tool doctors use to estimate survival times of people living with COPD.

The BODE Index is comprised of a person's body mass index ("B"), airway obstruction ("O"), dyspnea ("D"), and exercise tolerance ("E"). Each of these components is graded in the same manner as dyspnea and then tabulated for a final value. That final, tabulated value—ranging from as low as zero to as high as 10—provides us a percentage value of how likely a person is to survive for four years:

  • 0-2 points: 80 percent likelihood
  • 3-4 point: 67 percent likelihood
  • 5-6 point: 57 percent likelihood
  • 7-10 points: 18 percent likelihood

The values, whether large or small, are not set in stone. Changes to lifestyle and improved treatment adherence can improve long-term outcomes, sometimes dramatically. These include things like quitting smoking, improving your diet, and engaging in appropriate exercise to improve lung function.

In the end, the numbers are simply a guideline meant to assist us in improving your health, not predicting your mortality. As such, you play the central role in determining whether the odds are against you or in your favor.

Sources:

Chhabra, S., Gupta, A., and Khuma, M. "Evaluation of three scales of dyspnea in chronic obstructive pulmonary disease." Annals of Thoracic Medicine. 2009; 4(3):128-32.

Perez, T.; Burgel, P.; Paillasseur, J.; et al. "Modified Medical Research Council scale vs Baseline Dyspnea Index to evaluate dyspnea in chronic obstructive pulmonary disease." International Journal of Chronic Obstructive Pulmonary Disease. 2015; 10:1663-72.

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