Objective: To describe the development of a silicone stent and perform in vivo testing for biocompatibility/applicability in the normal canine trachea. Methods: Four different densities were tested in order to obtain the silicone prototypes. The pressure required for compression considering a contact area of 1 cm2, and a 30% reduction in diameter was calculated for each density. The best density was 70-75 Shore A hardness. Powdered barium sulfate was added to the silicone to make the stent radiopaque and easily identifiable in radiological imaging. This novel stent presents a corrugated external surface with discontinuous and protruding arcs resembling the tracheobronchial rings (for intercalation and fixation in the lumen of the lower airways), a highly polished inner surface and smooth extremities (to prevent friction-related damage). The prototype considered most appropriate in terms of rigidity and flexibility was bronchoscopically implanted in normal canine tracheas. After eight weeks, the animals were euthanized, and the tracheas were removed for anatomopathological analysis. Results: There were no postimplantation complications, and none had to be removed. After eight weeks, the devices were found to be well-positioned. Histopathology revealed a well-preserved epithelial basal membrane, foci of denuded epithelium, mild submucosal inflammatory infiltrate with scattered granulation tissue, vascular neoformation, and no microorganisms. Conclusions: The stent developed proved resistant to mechanical stress, biocompatible in the canine trachea and well-preserved at the study endpoint.

Keywords: Implants, experimental; Silicones; Biocompatible materials.

The surgical treatment of patients with tracheobronchial stenosis requires individualized attention due to the complexity of its origin though tracheoplasty is considered to be the ideal procedure. The most common causes of stenosis are tracheal intubation and the development of neoplasias. These are the very conditions that most benefit from endoscopic treatment when surgical correction is not indicated. Today, endoscopic procedures include the application of different kinds of laser and dilators usually delivered with a rigid bronchoscope, as well as radiotherapy and stents that may be used separately or associated. Basically, there are two types of stents, metal or silicone. The metallic ones are more frequently indicated in cases of tracheomalacia and extrinsic compressive stenosis. Silicone are more applicable in cases of tracheobronchial obstruction resultant from acute inflammation or endoluminal tumor. Although these methods can be used interchangeably in some cases, the best way to correct tracheobronchial stenosis is to correctly decide upon the treatment as early as the preliminary steps.

Keywords: Tracheal stenosis. Orthopedics fixation devices. Angioplasty.

Objective: Few studies have evaluated the variability of the perception of dyspnea in healthy subjects. The objective of this study was to evaluate the variability of the perception of dyspnea in healthy subjects during breathing against increasing inspiratory resistive loads, as well as to assess the association between the level of perception of dyspnea and the level of physical activity. Methods: This was a cross-sectional study involving healthy individuals 16 years of age or older. Subjects underwent inspiratory resistive loading testing, in which the level of perception of dyspnea was quantified with the modified Borg scale. We also determined body mass indices (BMIs), assessed maximal respiratory pressures, performed pulmonary function tests, applied the international physical activity questionnaire (IPAQ)-long form, and conducted six-minute walk tests (6MWTs). The level of perception of dyspnea was classified as low (Borg score < 2), intermediate (Borg score, 2-5), or high (Borg score > 5). Results: We included 48 healthy subjects in the study. Forty-two subjects completed the test up to a load of 46.7 cmH2O/L/s. The level of perception of dyspnea was classified as low, intermediate, and high in 13, 19, and 10 subjects, respectively. The level of perception of dyspnea was not significantly associated with age, gender, BMI, IPAQ-long form score, maximal respiratory pressures, or pulmonary function test results. Conclusions: The scores for perceived dyspnea induced by inspiratory resistive loading in healthy subjects presented wide variability. The perception of dyspnea was classified as low in 31% of the subjects, intermediate in 45%, and high in 24%. There was no association between the level of perception of dyspnea and the level of physical activity (IPAQ or six-minute walk distance).

Keywords: Dyspnea; Respiratory function tests; Exercise test.

Objective: To identify the role of bronchodilators in the maximal breath-hold time in patients with obstructive lung disease (OLD). Methods: We conducted a case-control study including patients with OLD and a control group. Spirometric tests were performed prior to and after the use of a bronchodilator, as were breath-hold tests, using an electronic microprocessor and a pneumotachograph as a flow transducer. Respiratory flow curves were displayed in real time on a portable computer. The maximal breath-hold times at end-inspiratory volume and at end-expiratory volume (BHTmaxVEI and BHTmaxVEE, respectively) were determined from the acquired signal. Results: A total of 35 patients with OLD and 16 controls were included. Prior to the use of a bronchodilator, the BHTmaxVEI was significantly lower in the OLD group than in the control group (22.27 ± 11.81 s vs. 31.45 ± 15.73 s; p = 0.025), although there was no significant difference between the two groups in terms of the post-bronchodilator values (24.94 ± 12.89 s vs. 31.67 ± 17.53 s). In contrast, BHTmaxVEE values were significantly lower in the OLD group than in the control group, in the pre- and post-bronchodilator tests (16.88 ± 6.58 s vs. 22.09 ± 7.95 s; p = 0.017; and 21.22 ± 9.37 s vs. 28.53 ± 12.46 s; p = 0.024, respectively). Conclusions: Our results provide additional evidence of the clinical usefulness of the breath-hold test in the assessment of pulmonary function and add to the existing knowledge regarding the role of the bronchodilator in this test.

Keywords: Respiratory function tests; Pulmonary disease, chronic obstructive; Bronchodilator agents; Apnea.

Objective: To evaluate the behavior of oxygen saturation curves throughout the six-minute walk test (6MWT) in patients with COPD. Methods: We included 85 patients, all of whom underwent spirometry and were classified as having moderate COPD (modCOPD, n = 30) or severe COPD (sevCOPD, n = 55). All of the patients performed a 6MWT, in a 27-m corridor with continuous SpO2 and HR monitoring by telemetry. We studied the SpO2 curves in order to determine the time to a 4% decrease in SpO2, the time to the minimum SpO2 (Tmin), and the post-6MWT time to return to the initial SpO2, the last designated recovery time (RT). For each of those curves, we calculated the slope. Results: The mean age in the modCOPD and sevCOPD groups was 66  10 years and 62  11 years, respectively. At baseline, SpO2 was > 94% in all of the patients; none received supplemental oxygen during the 6MWT; and none of the tests were interrupted. The six-minute walk distance did not differ significantly between the groups. The SpO2 values were lowest in the sevCOPD group. There was no difference between the groups regarding RT. In 71% and 63% of the sevCOPD and modCOPD group patients, respectively, a ≥ 4% decrease in SpO2 occurred within the first minute. We found that FEV1% correlated significantly with the SpO2 (r = −0.398; p < 0.001), Tmin (r = −0.449; p < 0.001), and minimum SpO2 (r = 0.356; p < 0.005). Conclusions: In the sevCOPD group, in comparison with the modCOPD group, SpO2 was lower and the Tmin was greater, suggesting a worse prognosis in the former.

Keywords: Pulmonary disease, chronic obstructive; Exercise test; Blood gas monitoring, transcutaneous.