INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation.

In recent years there has been an increase in mortality and morbidity and it is estimated that it will be the third cause of death in 2020. ^{1) (2}

In Portugal, comparing the patient’s records between 2011 and 2017, there was an increase from 54,000 to 136,958 cases, being the currently estimated prevalence of 14.2% for those over 40 years old, which should be around 800,000 people. ²

The degree of obstruction is associated with many symptoms of the disease; however it is poorly predictive of dyspnea and quality of life. ^{1) (2) (3}

In fact, respiratory function does not explain all the symptoms of the disease, resulting activity intolerance not solely from the loss of pulmonary function, but associated with impaired gas exchange and peripheral muscle dysfunction causing muscle fatigue (especially of the lower limbs) and dyspnea with important impact in self-care and quality of life. ³

This fact led Global Initiative for Chronic Obstructive Lung Disease (GOLD) to propose, since 2011, a new stratification of the disease, combining the risk of exacerbation, spirometry and symptomatic assessment ¹.

Symptoms resulting from the disease, especially dyspnea, activity intolerance and loss of lung function lead to the recognition of Respiratory Rehabilitation (especially due to the exercise training component) as a non-pharmacological treatment indicated for people with COPD. ^{2) (3) (4) (5} Provided that intervention of Rehabilitation Nurses must meet the individual needs of the person, increasing tolerance to the activity fundamentally through exercise training and the educational component, promoting functional independence and the adoption of healthy behaviors. ^{4) (5}

In this context, the initial assessment of respiratory rehabilitation programs is essential to determine the impact of the disease on the person, as well as understand the individual response and the health care sensitive gains of the respiratory rehabilitation program. ^{3) (4) (6}

In this sense, data on dyspnea, activity tolerance and quality of life should be evaluated, which can be easily collected using the COPD Assessment Test (CAT). ^{4) (5) (6}

This questionnaire contains eight questions centered on respiratory function data: cough, sputum, dyspnea and limited chest expansion and also on non-respiratory data such as activity intolerance, sleep disturbances, and inability to perform activities of daily living. ^{3) (4) (7}

The CAT is a short assessment tool that simply quantifies the various impacts of disease symptoms and was developed to assess the health status and also to simplify communication between the sick person and the healthcare team.

It consists in 8 items answered along a 5-point Likert scale, with a maximum disease score of 40 points.

It is a self-administered questionnaire where scores range from 0 to 10 (mild), 11 to 20 (moderate), 21 to 30 (severe) and 31 to 40 (very severe). ^{3) (4) (6) (7}

The recent 2019 GOLD report recommends that people with a CAT greater than 10 points be stratified as highly symptomatic. ²

A decrease of 2 points in the CAT questionnaire is considered a relevant gain in health, making this value the least clinically significant difference, which is a very important indicator since it translates gains in health. ⁸

This study aimed to evaluate the effect of a respiratory rehabilitation program on the symptoms perceived by people with COPD assessed by the CAT and to understand its relationship with activity tolerance

In this sense, there were two questions that guided this investigation:

METHODS

RESULTS

The study included 45 people (71.9% men) with a mean age of 65.82 years old with a mean FEV1% of 40%. (Table 2)

The CAT results show a statistically improvement (p < 0.001) in the overall test result with a mean variation of -7.67 (Table 3).

Table 3 CAT Results 

Functional capacity had a statistical (p = 0.001) and clinically significant variation with a mean variation of 32.4 meters in the six-minute walk test (Table 4).

Table 4 Results 6 minutes walk test (6MWT) 

Finally, it was found that there is a negative correlation between the two variables studied, more accentuated in the values after the respiratory rehabilitation program. (Table 5)

Table 5 Correlation between CAT and Walk Test 

DISCUSSION

This investigation aimed to assess the impact of a respiratory rehabilitation program on symptoms and to understand its relationship with activity tolerance in people with COPD.

Our investigation obtained results that overlap with those results found in the most recent published scientific evidence; they obtained clinically significant gains both in the symptoms variable (assessed by CAT) and in the functional capacity variable (assessed by 6MWT).

We also verified that there is a negative correlation between the two variables, more exacerbated in the results after the rehabilitation program, which can be explained by the fact that exercise training improves cardiovascular capacity and reduces oxygen consumption, leading to a consequent improvement in dyspnea and tolerance the activity.

Another important finding in our investigation supports the importance of individualizing rehabilitation programs, since the impact on daily life activities and social interaction achieved clinically significant gains, despite the variability found.

As mentioned above, respiratory rehabilitation is the non-pharmacological treatment indicated for the treatment of people with COPD, being a combination of complex interventions based on individualized assessment of the person that include, but are not limited to, education and exercise training. ^{4) (5) (9) (12} Its success is due to its effect on reducing dyspnea and muscle fatigue present in approximately 68% of people with COPD in an outpatient setting, improving their physical and psychological condition and promoting the acquisition of self-management tools for the disease. ^{5) (9}

In this context, the initial assessment is of particular importance in order to better design and implement the exercise training program.

Likewise, it is essential to evaluate the result of our clinical practice in order to identify interventions with greater clinical benefit, as well as to provide more robustness to rehabilitation nursing care, improving not only clinical practice but also validating the knowledge guided by nursing theory.

In this context, the CAT emerges as an excellent assessment tool due to its simplicity and to translating the symptoms that usually reflect the person's problems.

Liu et al (2015) in an experimental study with a control group in a sample of 80 people concluded that despite the respiratory function being more compromised in the intervention group, the values ​​of the walking test after respiratory rehabilitation were higher than those in the control group. This fact clearly shows that CAT is a valid instrument to assess respiratory function and activity tolerance. ¹¹

Candemir et al (2015), in a sample of 40 people with COPD undergoing an 8-week respiratory rehabilitation program, related the results obtained by CAT with dyspnea (assessed by the MRC), quality of life (assessed by the Saint George Respiratory Questionnaire), daily life activities (assessed by the London Chest of daily living) and exercise tolerance (assessed by the Incremental Shuttle Walking test and the Endurance Shuttle Walking Test) having concluded that CAT is positively correlated with Quality of life, a dyspnea and life activities and negatively with effort tolerance. It also suggests that CAT is a robust instrument to assess the results of respiratory rehabilitation programs since it analyzes all the variables normally used as an indicator of results in respiratory rehabilitation programs. ¹²

Dood et al (2015) carried out a larger multicenter quasi-experimental study with a sample of 261 people with COPD, assessing anxiety, depression, quality of life, activity tolerance and quality of life in addition to CAT, having concluded that CAT is a simple, practical, viable and easy-to-complete instrument, which should be an integral part of both initial and final assessments of respiratory rehabilitation programs. ³

The same result was reached by Houben-Wilke S. et al (2018), who carried out a quasi-experimental study with 497 people with COPD and which revealed a significant improvement in the CAT and 6MWT values ​​after the respiratory rehabilitation program. ⁶

CONCLUSION

The current scientific evidence is unanimous in accepting exercise training and education as fundamental pillars in the rehabilitation of people with COPD, reducing the main symptoms of the disease (dyspnea and muscle fatigue).

CAT is sensitive to these results, expressing the gains sensitive to Rehabilitation Nursing care, and should be adopted in the evaluation of respiratory rehabilitation programs.