Bronchiectasis is a chronic inflammatory condition that causes permanent dilatation of the bronchi and bronchioles by destruction of structural components, resulting in decreased mucociliary clearance and increased airway susceptibility to bacterial colonization and infection.1

The diagnosis is traditionally performed using high resolution computed tomography (HRCT) in association with clinical signs and spirometry.2,3 Because spirometry requires great cooperation from subjects, the functional evaluation of patients with bronchiectasis can be complemented with impulse oscillometry (IOS), which provides compartmentalized information of the central and peripheral airways, during tidal breathing, with good sensitivity to identify changes in respiratory system resistance.4

Clinically, the most frequent characteristic of this disease is an increase in the production of bronchial secretions. The mucus produced is thicker and results in slower transport, causing damage to the mucociliary transport,5 and patients may benefit from specific physiotherapy techniques for the removal of secretions from the respiratory system,6 as well as overall exercises within pulmonary rehabilitation programs.7

The functional exercise capacity of patients with respiratory diseases, such as bronchiectasis, may be reduced by several factors, due to increase in ventilatory demand, which causes an overload to the respiratory muscles. During the exercise, these patients have an increase in the respiratory rate which induces a dynamic hyperinflation.

Because it is difficult to use some measurements during exercise, the literature describes some controlled experimental situations to simulate the increased ventilatory demand that occur during exercises, using voluntary controlled respiratory rate in COPD patients,8 and using voluntary controlled hyperinflation in subjects with restrictive pattern.9 However, no similar studies were found in patients with bronchiectasis, to identify how this exercise respiratory pattern can affect the respiratory system resistance and to propose respiratory control strategies that might enable less exhaustive exercise.

In this study, we evaluated the effects of controlled voluntary hyperinflation and increased respiratory rate on the mechanics of the respiratory system, simulating what happens during exercise, in bronchiectasis and healthy subjects.

In this cross-sectional study, the sample size was calculated based on pilot study by G*Power (3.1.9.2) using the resistance at 5Hz (R5), resulting in 16 volunteers per group. The project was approved by the Human Research Ethics Committee of the Clinical Hospital of the Ribeirão Preto Medical School, University of São Paulo, CAAE 66047717.2.0000.5440.

There were included volunteers aged 18–70 years, diagnosed with bronchiectasis not due to cystic fibrosis, recruited at the pulmonology outpatient clinic of the Hospital das Clínicas of the Medical School of Ribeirão Preto, as well as healthy volunteers who were not active or ex-smokers without lung disease. Participants with COPD, asthma, lung cancer, and lobectomy, active or ex-smokers, and individuals with cardiovascular disease or decompensated metabolic, neuromuscular, or musculoskeletal diseases were excluded. All participants have signed the Informed Consent Form.

The medical diagnoses were based on clinical history, HRCT, and spirometry. In the Laboratory of Assessment Respiratory, they were evaluated by sociodemographic and anthropometric data, Bronchiectasis Severity Index (BSI) for assess the severity, ventilometry, spirometry, and impulse oscillometry system (IOS).

The anthropometric and evaluation data of the subjects are described in Table 1. In the BSI score the patients were classified as intermediate, the mean of the group is 5 points. The values obtained for R5 and R5-20 were higher in subjects with bronchiectasis in all experimental conditions (Table 2).

In the bronchiectasis group, R5 (kPa/L/s) showed differences between VRb versus VR30 (p=0.0001), VR40 (p=0.0001), and HR40 (p=0.0001); VR30 versus VR40 (p=0.02); HRb versus HR40 (p=0.0001); HR30 versus HR40 (p=0.0005); HRb versus VR30 (p=0.0001), and VR40 (p=0.0001); and HR30 versus VR30 (p=0.001) and VR40 (p=0.0001).

For R20 (kPa/L/s), there were differences between HRb versus VR30 (p=0.01), and VR40 (p=0.001); HR30 versus VRb (p=0.02), VR30 (p=0.005), and VR40 (p=0.0004); and HR40 versus VR40 (p=0.009).

In R5-R20 (kPa/L/s), there were differences between VRb versus VR30 (p=0.0001), and VR40 (p=0.0001); VR30 versus VR40 (p=0.0001); HRb versus HR40 (p=0.0001); HR30 versus HR40 (p=0.0001); VRb versus HR30 (p=0.0008), and HR40 (p=0.0001); HRb versus VR30 (p=0.0001), and VR40 (p=0.0001); and HR30 versus VR30 (p=0.005), and VR40 (p=0.0001) (Fig. 1, Table 2).

Fig. 1.

* p<0.02; VR30: TV and RR 30 breaths/min; VR40: TV and RR 40breaths/min; HRb: hyperinflation (H) with RR b; (HR30): H with RR 30breaths/min and HRR40: H with RR 40breaths/min.

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In the healthy group, only R20 (kPa/L/s) showed a difference when compared the HR30 versus HR40 (p=0.007); and HR40 versus VR40 (p=0.004) (Fig. 1, Table 2).

Our results demonstrated that an increased respiratory rate promotes increases in the total, central and peripheral resistances, in subjects with bronchiectasis and an increase in the central resistance in healthy subjects. When they were instructed to perform a voluntary controlled hyperinflation, the high resistance and reactance, induced by the respiratory rate increases was attenuated, close to the baseline values, in the bronchiectasis group. Comparing bronchiectasis to the healthy group, there was an increase in the total and peripheral resistance of the respiratory system in all experimental conditions, which could be explained to the more compromised peripheral airways in the subjects’ with bronchiectasis.14

People with bronchiectasis experience reduction in both exercise capacity and health-related quality of life.15 Reduction in exercise capacity has been associated with structural alterations to lung tissue, progressive airflow obstruction, dyspnea secondary to dynamic hyperinflation, and psychological morbidity.15–17

In general, dynamic hyperinflation is associated with a mechanically disadvantageous position for the respiratory muscles, causing increased respiratory work and exercise limitation.18 Nevertheless, the hyperinflation mechanism, as the increase in the lung volume, promotes a reduction in the airways resistance because the bronchi are supported by the radial traction of surrounding lung tissue, and their caliber increases as the lung expands.19

The use of strategies to reduce respiratory work during exercise is widespread, for example, the pursed-lips breathing. This maneuver maintains positive expiratory pressure on the airways, increasing alveolar pressure and central displacement of the point of equal pressure, avoiding alveolar collapse.20

However, the effects of pursed-lips breathing during exercise capacity are still controversial. Studies with COPD showed a reduction in dynamic hyperinflation and an increase in SpO2, in the endurance and incremental tests, after the use of a bronchodilator plus pursed-lips breathing.21 Another study using pursed-lips breathing without bronchodilator, reported a reduction of dynamic hyperinflation in the Glittre test, but not in the six-minute walk test distance.22

Physical activities and exercises are recommended for patients with chronic respiratory diseases because they are associated with clinical patient outcomes improvements. Pulmonary rehabilitation programs for people with bronchiectasis, that increases the ventilator demand during aerobic exercises, aims to improve exercise capacity, through effects on aerobic capacity and peripheral muscle, as well as to enhance disease management and improve quality of life.7 Programs of pulmonary rehabilitation for stable patients have clinically significant benefits but the improvements in exercise capacity and healthy related quality of life are of a short duration. Further exploration to identify the effects of these interventions on disease severity and optimal approaches to maintain positive outcomes are needed.23

Our findings have shown that hyperinflation is not detrimental when we observe it effects on airway resistance. In our protocol, hyperinflation was beneficial even without the use of the bronchodilator, reducing resistance values that were elevated by increased respiratory rate. Based on these results, we hypothesize that, during exercise, individuals with increased resistance values may benefit from voluntary control of respiratory frequency and volume of exhaled air, and that this strategy could contribute to clinical improvements in dyspnea.

The exertional dyspnea for people with respiratory diseases is usually multifactorial in origin, partly reflecting peripheral muscle dysfunction, the consequences of dynamic hyperinflation, increased respiratory load, or defective gas exchange.24–26 Although dyspnea is not the primary symptom of bronchiectasis, a reduction in dyspnea may partially contribute to the improvement in the exercise capacity and healthy related quality of life.23

In this study we had a controlled situation, without other adaptations to exercise, and we need to know if these physiological strategies could contribute to reduce the exercise limitation in bronchiectasis patients. It is important to identify strategies that may improve exercise tolerance, which need to be evaluated during exercise in patients with bronchiectasis, contributing to a reduction of sedentary behavior and an improvement in the quality of life. It is also important to identify whether other patients with increased respiratory system resistance, such as asthma sufferers for example, may also benefit, since there was a decrease in central resistance in subjects with bronchiectasis and in subjects without lung disease. Because the evaluation occurred in a controlled experimental setting, it is necessary to know if these results could be reproduced during exercises for aerobic training.

In conclusion, the tachypnea increases the resistance and reactance of the respiratory system in bronchiectasis patients, and the voluntary hyperinflation caused attenuates this increase. These results can guide the development of strategies to reduce the limitation of physical activity in patients with bronchiectasis

This work was supported by São Paulo Research Foundation (FAPESP process numbers 2016/20077-6), and National Council for Scientific and Technological Development (CNPq). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES).

The authors declare no conflicts of interest.