Measuring Shortness of Breath (Dyspnea) in COPD

Dyspnea is the medical term used to describe shortness of breath, a symptom considered central to all forms of chronic obstructive pulmonary disease (COPD) including emphysema and chronic bronchitis.

As COPD is both a progressive and non-reversible, the severity of dyspnea plays a key role in determining both the stage of the disease and the appropriate medical treatment.

Challenges in Diagnosis

From a clinical standpoint, the challenge of diagnosing dyspnea is that it is very subjective. While spirometry tests (which measures lung capacity) and pulse oximetry (which measures oxygen levels in the blood) may show that two people have the same level of breathing impairment, one may feel completely winded after activity while the other may be just fine.

Ultimately, a person's perception of dyspnea is important as it helps ensure the person is neither undertreated nor overtreated and that the prescribed therapy, when needed, will improve the person's quality of life rather than take from it.

To this end, pulmonologists will use a tool called the modified Medical Research Council (mMRC) dyspnea scale to establish how much an individual's shortness of breath causes real-world disability.

How the Assessment Is Performed

The process of measuring dyspnea is similar to tests used to measure pain perception in persons with chronic pain. Rather than defining dyspnea in terms of lung capacity, the mMRC scale will rate the sensation of dyspnea as the person perceives it.

The severity of dyspnea is rated on a scale of 0 to 4, the value of which will direct both the diagnosis and treatment plan.

Role of the MMRC Dyspnea Scale

The mMRC dyspnea scale has proven valuable in the field of pulmonology as it affords doctors and researchers the mean to:

• Assess the effectiveness of treatment on an individual basis
• Compare the effectiveness of a treatment within a population
• Predict survival times and rates

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

Using the BODE Index to Predict Survival

The mMRC dyspnea scale is used to calculate the BODE index, a tool which helps estimate the 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 on a scale of either 0 to 1 or 0 to 3, the numbers of which are then tabulated for a final value.

The final value—ranging from as low as 0 to as high as 10—provides doctors a percentage of how likely a person is to survive for four years. The final BODE tabulation is described as follows:

• 0 to 2 points: 80 percent likelihood of survival
• 3 to 4 points: 67 percent likelihood of survival
• 5 of 6 points: 57 percent likelihood of survival
• 7 to 10 points: 18 percent likelihood of survival

The BODE 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 your respiratory capacity.

In the end, the numbers are simply a snapshot of current health, not a prediction of your mortality. Ultimately, the lifestyle choices you make can play a significant role in determining whether the odds are against you or in your favor.