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Biomedical subjects

C Lisboa

Publications and source records attributed to C Lisboa.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Peroxide metabolism on respiratory muscles: effect of growth, maturation and aging].

BACKGROUND: Glutathione peroxidase (GSHPx) and catalase are two important cellular antioxidant enzymes involved in H2O2 and lipid-peroxide metabolism. AIM: To study the effects of growth, maturation and aging on the activity of these enzymes. MATERIAL AND METHODS: GSHPx and catalase specific activities were measured in samples of diaphragm and intercostal muscle of male Sprague-Dawley rats of different ages (21, 50, 70, 180 and 365 days), anesthetised with chloral hydrate (45 mg/100 g i.p.). RESULTS: The diaphragm and intercostal muscles did not differ in GSHPx activity at 21 days. After that, GSHPx activity increased progressively with age, but following a different pattern, in each muscle, suggesting an increase in enzyme substrates with age. In one year old animals, GSHPx activity was 5 times higher for the diaphragm and 3 times higher for the intercostal muscles, when compared with values observed at 21 days of age. Catalase activity also increased with age in the diaphragm but not in the intercostal muscles. CONCLUSIONS: GSHPx activity increases progressively with age in rat respiratory muscles, with a time course that is specific of each muscle. Catalase activity increases with age only in the diaphragm. These results support the hypothesis that antioxidants in respiratory muscles undergo specific regulatory changes with age.

Age Factors↗
PubMed1999

[Effects of inspiratory muscle training on the oxygen cost of breathing in patients with chronic obstructive pulmonary disease].

BACKGROUND: Patients with chronic obstructive pulmonary disease have an increased inspiratory work, since they must overcome high loads due to increased airway resistance. AIM: To determine if the reduction in the metabolic cost of exercise observed in patients with chronic obstructive pulmonary disease (COPD) after inspiratory muscle training, was due to a reduction in the oxygen cost of breathing. PATIENTS AND METHODS: Nine patients with COPD (FEV1 39 +/- 13%) subjected to inspiratory muscle training, using a training load of 30% of maximal inspiratory pressure, during 10 weeks; 5 patients with COPD (FEV1 44 +/- 18%) not subjected to training, and 7 healthy controls (FEV1 110 +/- 10%) were studied. The cost of breathing was calculated as the difference in VO2 measured at rest and after breathing a gas mixture containing air and 5% CO2. Exercise VO2 was measured at submaximal exercise. RESULTS: Oxygen cost of breathing was increased in patients with COPD and it was inversely correlated with FEV1 (r = -0.86 p < 0.001). Inspiratory muscle training increased maximal inspiratory pressure and decreased exercise VO2. Oxygen cost of breathing increased in six and decreased in three trained patients. Changes in this parameter after training did not correlate with the reduction in exercise VO2 or the increment in maximal inspiratory pressure. CONCLUSIONS: The reduction in exercise VO2 after inspiratory muscle training is not due to a reduction in the oxygen cost of breathing.

Aged↗
PubMed1999

[Non-invasive mechanical ventilation in patients with severe stable COPD].

BACKGROUND: The benefits of non-invasive mechanical ventilation (NIMV) in hypercapnic patients with severe stable COPD remain controversial mainly due to their unknown mechanisms. AIM: To assess the clinical and physiological benefits of a 3 weeks period of intermittent NIMV and their underlying mechanisms in COPD patients. PATIENTS AND METHODS: Twelve patients (10 male) prospectively recruited (age 65 +/- 3 years, FEV1 27 +/- 2% predicted, PaO2 46 +/- 2 mmHg, PaCO2 55 +/- 2 mmHg) were submitted to NIMV using a commercially available system (BiPAP) 3 h a day, 5 days a week for 3 weeks. Arterial blood gases, 6 min walking distance, dyspnea (Mahler's scale), breathing pattern, PIMax, ventilatory drive (P0.1) and the impedance of the respiratory system (P0.1/V1/T1) were measured before and after NIMV. RESULTS: A significant improvement in PaO2, PaCO2, PIMax, dyspnea and exercise capacity was observed in addition to a trend for VT to increase and for respiratory rate (RR) to decrease. The impedance of the respiratory system showed a significant reduction. Ventilatory drive, normalized for PaCO2 levels, did not change. Improvement in PaCO2 was related to an increase in Vp whereas a significant association between the reduction in RR and the fall in respiratory system impedance was also found. CONCLUSIONS: Our study supports previous data demonstrating that NIMV improves clinical and physiologic parameters in advanced stable COPD and suggest that the underlying mechanism is a reduction in the inspiratory load. A randomized clinical trial is needed to confirm that this mechanism is operative.

Aged↗
PubMed1998

Effect of inspiratory muscle training with an intermediate load on inspiratory power output in COPD.

There is very little information about the effect of inspiratory muscle training on inspiratory flow (V'I) and thus on power output (PO) in patients with chronic obstructive pulmonary disease (COPD). In this study we aimed to evaluate the changes induced by training on the determinants of PO. Thirty one patients with severe COPD were randomly divided into: Group 1, trained with 30% maximal inspiratory pressure (PI,max); Group 2, with 10% PI,max; and Group 3 also trained with 30% PI,max, but the breathing pattern was evaluated while performing the training manoeuvres along inspiratory muscle training (IMT). All groups used a threshold device for 10 weeks. The PO for each of the loads during an incremental threshold test was evaluated prior to and after training. Maximal PO (POmax) increased in all groups, but the increment was higher in groups trained with 30% PI,max (p<0.005), mainly due to an increase in V'I. Group 3 showed a progressive increase in V'I (p<0.001) during the training manoeuvres in spite of an increase in load along IMT. In addition, the load after IMT was overcome with a shorter inspiratory time (tI) (p<0.02), a smaller tI/total duration of the respiratory cycle (t(tot)), (p<0.001) with no change in tidal volume or t(tot). The increment in POmax in this group correlated with the V'I generated while training (r=0.85; p<0.0001). We conclude that in patients with chronic obstructive pulmonary disease, the use of an intermediate threshold load for training improves power output mainly by increasing inspiratory flow, an effect consistent with an increase in shortening velocity of inspiratory muscles.

Aged↗
PubMed1998

[Experimental pulmonary emphysema in rats. Inflammatory phenomena and progression of lung damage].

BACKGROUND: Although the hamster model of elastase induced emphysema is well characterized, the rat model has received less attention. AIM: To evaluate the effect of a single intratracheal elastase dose on lung pathological changes of Sprague-Dawley rats. MATERIAL AND METHODS: Rats were injected with a single intratracheal elastase dose of 28 U/100 g body weight or saline and studied 7, 15, 30 and 365 days after injection. RESULTS: Forty percent of rats died in the first 48 hours after injection, six were sacrificed at 7 days, 6 at 15 days, 7 at 30 days and 12 at 365 days. Progressive centroacinar emphysema was found from day 7 after elastase, with a persistent inflammatory reaction in the vicinity of emphysematous areas. CONCLUSIONS: Present findings differ from the panacinar emphysema described in the hamster using a similar elastase dose.

Animals↗
PubMed1998

[Inspiratory muscle training in patients with chronic obstructive pulmonary disease].

We analyze the effect of inspiratory muscle training (IMT) in patients with chronic obstructive pulmonary disease (COPD), with special emphasis on its effects on inspiratory muscle function and clinical outcomes. We reviewed only randomized, controlled studies that have either controlled both the load and the breathing pattern when using resistive training or have employed a threshold trainer in which the load is independent of the pattern of breathing, since methodological aspects may explain inconsistent results in the literature. In these circumstances, most of the studies demonstrated positive effects on inspiratory muscle function. Clinical effects were seldom evaluated; limited available data showed a reduction in dyspnea that was related to an increase in maximal inspiratory pressures (PIMax). When exercise capacity was evaluated through the distance the patients were able to walk in 6 or 12 minutes, most studies demonstrated a significant increase. Other reported positive effects were improvement in nocturnal SaO2, inspiratory muscle power output and maximal inspiratory flow rate. Based in this review, a recommended training regime appears to be an intermediate load (30-40% PIMax) using a threshold device for 30 minutes daily for at least 5 weeks. Although in the literature the criteria for selecting patients are not always well defined, we consider IMT as a helpful procedure for pulmonar rehabilitation in those patients with a moderately severe inspiratory muscle dysfunction presenting dyspnea during daily living activities despite optimal therapy.

Anaerobic Threshold↗
PubMed1997

Inspiratory muscle training in chronic airflow limitation: effect on exercise performance.

The effect of inspiratory muscle training (IMT) on exercise capacity in patients with chronic airflow limitation (CAL) has been debated. The present study was planned to further investigate the effects of IMT on exercise performance. Twenty patients (aged 62+/-1 yrs; forced expiratory volume in one second/forced vital capacity (FEV1/FVC) 36+/-2%) were trained 30 min daily for 6 days a week during 10 weeks, with either 30% (Group 1) or 10% (Group 2) of peak maximal inspiratory pressure (PI,max) as a training load. Exercise performance was evaluated by the distance walked in 6 min (6MWD) and by changes in oxygen consumption (V'O2) and minute ventilation (V'E) during a progressive exercise test. Changes in PI,max and dyspnoea were also measured. Results showed a significant increment in peak PI,max in both groups, whereas dyspnoea and 6MWD improved only in Group 1 (p<0.05 and p<0.01, respectively). No increment in maximal workload or in peak V'O2 was observed in either group. Patients in Group 1, however, showed a reduction in V'E and V'O2 for the same exercise. A correlation between changes in V'E and V'O2 during a workload of 75 kpm x min(-1) was observed in Group 1 (r=0.92; p<0.001). We conclude that inspiratory muscle training using a load of 30% peak maximal inspiratory pressure, improves dyspnoea, increases walking capacity and reduces the metabolic cost of exercise.

Breathing Exercises↗
PubMed1995

[Acute altitude sickness and ventilatory function in subjects intermittently exposed to hypobaric hypoxia].

Aiming to assess the magnitude of acute mountain sickness symptoms and ventilatory function in subjects intermittently exposed to hypobaric hypoxia, we studied 48 healthy men aged 32.6 +/- 8.2 years old who worked in a gold mine at a altitude of 4600 m, using a schedule of 8-12 days of work at the mine followed by 4 days of rest at the sea level. Studies were performed at the sea level (A), during the first two days of ascension (B) and after three or four days of stay at 4600 m (C). Mountain sickness symptoms were evaluated with a questionnaire devised in the 1991 International Hypoxia Symposium and respiratory function was assessed with a Collins Eagle II respirometer, following American Thoracic Society recommendations. Subjects reported mild to moderate symptoms during the first 24 hours of ascending (mean score of 6.4 +/- 3.1 for a maximum of 15). Forced vital capacity fell significantly in period B and returned to normal in period C and forced expiratory volume in 1 s did not change in any period. However, maximal expiratory flow and maximal midexpiratory flow rate significantly increased and remained elevated during the four days stay at the mine. No correlation was found between acute mountain sickness symptoms and changes in ventilatory function.

Adult↗
PubMed1995

[Clinical effects of inspiratory muscle training in patients with chronic airflow limitation].

The clinical role of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) has not been established, because data on its clinical effect is scarce and controversial. To further investigate these aspects we studied 20 COPD patients (FEV1 37 +/- 3% P) who were randomly and double blindly trained for 30 minutes a day during 10 weeks using a threshold inspiratory trainer with either 30% (group 1) or 10% (group 2) of PIMax as a training load. The training load was crossed after each patient completed 10 weeks of training. Effects were assessed through changes in PIMax, dyspnea through the transition dyspnea index (ITD) and the respiratory effort with Borg's score. Walking capacity was measured with the six minutes walking distance test (6WD) and depression symptoms with Beck's score. Daily life activities were also assessed. Results showed that after 10 weeks of IMT, PIMax increased in both groups (p < 0.05), dyspnea improved in group 1 as compared to group 2 (p < 0.04), 6WD increased significantly in patients of group 1, who also complained of less dyspnea (p < 0.05). Depression scores fell significantly in group 2. Daily activities improved more in group 1. After the crossover patients in group 1 disclosed a significant deterioration in PIMax whereas group 2 disclosed significant improvements in PIMax, dyspnea and 6WD. We conclude that IMT using a threshold device with 30% PIMax is a useful procedure for the treatment of severe COPD patients.

Activities of Daily Living↗
PubMed1995

[Non-invasive intermittent mechanical ventilation: usefulness in treatment of chronic severe heart failure].

BACKGROUND: The higher respiratory work and less inspiratory muscle strength of patients with cardiac failure may contribute to decrease their functional capacity. AIM: To assess the effects of non invasive intermittent mechanical ventilation on clinical parameters, peripheral perfusion, cardiac and inspiratory muscle function. PATIENTS AND METHODS: Patients with chronic cardiac failure, functional capacity III-IV were subjected to 6 sessions of nasal non invasive intermittent ventilation during 4 hours or to simulated ventilation (controls). RESULTS: Fifteen ventilated patients and six controls completed the protocol. Ventilated patients improved the Mahler transition score for dyspnea by 4 +/- 1.6 points. They also improved their aerobic capacity, increasing the exercise duration from 10.9 +/- 4 to 12.7 +/- 5 min and their maximal oxygen consumption from 14.6 +/- 4 to 16.4 +/- 5.7 ml/kg/min. These patients also decreased their O2 and CO2 ventilatory equivalents. Maximal inspiratory pressure increased from 67.9 +/- 23.6 to 80.19 +/- 21.4 cm H2O, sustained maximal inspiratory pressure increased from 101.4 +/- 48 to 133 +/- 53 cm H2O and maximal endurance increased from 132 +/- 52 to 162 +/- 58 g in ventilated patients. None of these variables was modified in control patients. No changes were observed in renal function, blood volume, arterial gases, spirometry or plasma catecholamine levels in any group. CONCLUSIONS: Intermittent nasal ventilation or other measures to improve inspiratory muscle function may be beneficial for patients with severe cardiac failure.

Adult↗
PubMed1994

Contact dermatitis from textile dyes.

6 female patients with allergic contact dermatitis from textile dyes are described. Lesions were confined to areas in direct contact with the offending garment, mainly where friction and/or pressure occurred. Patch tests were positive to 2 or more disperse dyes. Thin-layer chromatography was carried out on the dyes extracted from fabrics of 3 patients, for the identification of textile dyes.

Adolescent↗
PubMed1994

Inspiratory muscle training in chronic airflow limitation: comparison of two different training loads with a threshold device.

The usefulness of inspiratory muscle training (IMT) in chronic airflow limitation (CAL) patients is a controversial issue, mainly due to differences in the training load. To further evaluate this aspect, we studied the effect of the magnitude of the load using a threshold pressure trainer. Ten CAL patients (5 males, 5 females) 67 +/- 2 yrs (mean +/- SEM) and forced expiratory volume in one second (FEV1) 36 +/- 2% pred, were trained for 30 min a day using a load of 30% of their maximal inspiratory mouth pressure (PImax) (Group 1). Another 10 CAL patients (5 males, 5 females), 73 +/- 2 yrs and FEV1 37 +/- 2% pred), were trained using only 12% of their PImax (Group 2). Training was assessed by PImax, inspiratory muscle power output (IMPO), sustainable inspiratory pressure (SIP), maximal inspiratory flow rate (VImax), pattern of breathing during loaded breathing, Mahler's dyspnoea score, and the 6 min walking distance (6MWD). After 5 weeks of training, Group 1 exhibited significant increments in: PImax (34 +/- 11%); IMPO (92 +/- 16%); SIP (36 +/- 9%); and VImax (34 +/- 13%). Dyspnoea was also reduced, and the 6MWD increased by 48 +/- 22 m. We observed no significant changes in Group 2. During loaded breathing, Group 1 showed a significant increment in tidal volume (VT) and mean inspiratory flow (VT/TI), and a reduction in inspiratory time (TI). In Group 2, VT and VT/TI also increased significantly, but the breathing frequency increased with a reduction of expiratory time.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Limitation of airway smooth muscle shortening by cartilage stiffness and lung elastic recoil in rabbits.

Airway smooth muscle can contract to 20% of its starting length when stimulated maximally and allowed to contract isotonically in vitro. In vivo airway smooth muscle contraction of this degree would result in widespread airway closure. We hypothesized that elastic loads related to cartilage stiffness and lung parenchyma-airway interdependence limit in vivo airway smooth muscle shortening. We measured pulmonary resistance in anesthetized tracheostomized New Zealand White rabbits before and after intravenous treatment with papain in a concentration that produced generalized cartilage softening. Papain treatment caused a significant increase in pulmonary resistance that was completely reversed by application of 4 cmH2O positive end-expiratory pressure and that was partially reversed by vagotomy. Papain pretreatment also resulted in a substantial alteration in the pulmonary resistance-dose relationship to intravenously administered acetylcholine. In addition, maximal resistance after the highest concentration of acetylcholine was greater in papain-treated animals than in the control animals, but the position of the dose-response relationship was not shifted (i.e., there was no change in the effective dose causing 50% maximal response). Application of 4 cmH2O positive end-expiratory pressure in untreated animals resulted in a marked decrease in the bronchoconstriction produced by an effective dose of acetylcholine causing 50% of maximal response, whereas application of 4 cmH2O negative end-expiratory pressure resulted in a marked enhancement of the bronchoconstrictor response to the same intravenous dose of acetylcholine. We conclude that cartilage elasticity and lung recoil are important determinants of the ability of airway smooth muscle to shorten and produce airway narrowing in vivo.

Acetylcholine↗
PubMed1992

[Intermittent negative pressure ventilation in patients with chronic air flow limitation: criteria for selection of patients].

To determine clinical and functional predictive criteria for use of intermittent negative pressure ventilation we evaluated 9 patients with severe chronic air flow limitation. Arterial blood gases, lung volumes, maximal inspiratory pressures and transdiaphragmatic pressure during quiet breathing were measured. patients were then ventilated once or twice a week for 3 to 10 weeks and improvement was evaluated through changes in quality of life, dyspnea, PaO2, PaCO2 and maximal inspiratory mouth pressure (PRMAX). Result was considered good when 4 or more of these indices improved. 5 patients benefitted from intermittent negative pressure ventilation. Compared to non responders, patients who improved had significantly lower PRMAX (39.4 +/- 11.6 VS 73.5 +/- 13.8 CMh20, p < 0.025), and higher percentage of their maximal inspiratory pressure during quiet breathing (31.2 +/- 7 vs 12.2 +/- 5%, p < 0.025>). Other indices were not different between groups. We conclude that a severe impairment of inspiratory muscle function characterizes patients with chronic air flow limitation who may benefit from intermittent negative pressure ventilation.

Adult↗
PubMed1991

Ventilatory drive and respiratory muscle function in pregnancy.

It has been demonstrated that during pregnancy expiratory reserve volume (ERV) decreases and minute ventilation (VE) increases initially and then stabilizes. In order to determine the role of thoracoabdominal mechanics, control of breathing, and inspiratory muscle function in these alterations, we studied inspiratory pressures, lung volumes, thoracic configuration, and respiratory drive in 18 normal pregnant women at Weeks 13, 21, 30, and 37 of pregnancy. Ten of them were studied 6 months after delivery. Transdiaphragmatic pressure (Pdi) was measured at Week 37 and 3 months after delivery in an additional group of seven women. VE as well as VT/TI increased early during gestation and remained unchanged thereafter. In contrast, mouth occlusion pressure (P0.1) increased progressively during pregnancy, from 1.53 +/- 0.16 (mean +/- SE) to 2.02 +/- 0.18 cm H2O, and fell significantly to 1.1 +/- 0.15 cm H2O after delivery, indicating that effective respiratory impedance increases during pregnancy. Mean P0.1 correlated with progesterone plasma levels (r = 0.918 p less than 0.05). No changes in Plmax, PEmax, and Pdimax, were observed. End-expiratory gastric pressure (Pga) increases significantly during pregnancy: 11.8 +/- 0.8 versus 8.4 +/- 1.12 cm H2O after delivery (p less than 0.012). This increment was correlated with the fall in ERV observed in late pregnancy (r = 0.74 p less than 0.05). Our results demonstrate that during pregnancy ventilatory drive and respiratory impedance increase with the consequent stabilization of VE, but our data do not permit us to differentiate whether the increment in P0.1 is secondary to the increase in impedance or to the rise in progesterone. Respiratory muscle function remains normal despite the alteration of thoracic configuration.

Adult↗
PubMed1988

Weekly cuirass ventilation improves blood gases and inspiratory muscle strength in patients with chronic air-flow limitation and hypercarbia.

We studied the effects of an 8-h, once-a-week schedule of cuirass ventilation (CV) in 5 patients with advanced chronic air-flow limitation and chronic hypercarbia (PaCO2, 58.6 +/- 10.1 mm Hg; mean +/- SD). Repeated measurements of arterial blood gases, maximal inspiratory mouth pressure (P1max), 12-min walking distance, and respiratory cycle were performed during a 1-month run-in period. Quality of life and transdiaphragmatic pressure were measured once. All patients completed the planned 4-month study. Four of them were ventilated for longer periods because CV could not be discontinued at the end of the study. PaCO2 showed a significant fall starting during the first month; PaO2 significantly increased from the second month, whereas P1max significantly rose from the third month on. Maximal transdiaphragmatic pressure increased in the 2 patients with abnormal baseline values. The fall in PaCO2 was associated with an increase in tidal volume because of a longer inspiratory time. Significant improvements in quality of life and in the 12-min walking distance were observed. We conclude that weekly CV improves blood gases, inspiratory muscle strength, and clinical conditions of patients with chronic air-flow limitation and chronic hypercarbia, probably because of correction of chronic inspiratory muscle fatigue.

Blood Gas Analysis↗
PubMed1986

Inspiratory muscle function in unilateral diaphragmatic paralysis.

Pulmonary function has been extensively studied in unilateral diaphragmatic paralysis (UDP), but there is scarce information regarding inspiratory muscle function in this condition. We therefore studied inspiratory muscle function in 8 patients with UDP (Group 1: age 48.3 +/- 2.1 yr of age, means +/- SD) as well as in 7 patients with UDP and concomitant cardiopulmonary disease (Group 2: 60.6 +/- 13 yr of age). Twelve young normal subjects were also studied (32.3 +/- 7.7 yr of age). Maximal static transdiaphragmatic and inspiratory mouth pressure were measured at FRC. Gastric (Pga), esophageal (Pes), and transdiaphragmatic (Pdi) pressure swings were measured during quiet breathing. There was no difference in inspiratory muscle function in left-sided versus right-sided UDP. Paradoxical gastric pressure swings were observed in 4 patients from Group 1 and in 5 from Group 2. In 2 patients from Group 1 and 1 from Group 2, Pga did not change during quiet breathing. In the remaining 3 patients, Pga swings were similar to those observed in the normal subjects. Maximal Pdi was reduced in half of the patients from Group 1 and in all of the patients from Group 2. Maximal inspiratory pressure was below normal values in 2 patients from Group 1 and in all patients from Group 2. We conclude that unilateral diaphragmatic paralysis is associated with an abnormal pattern of use of respiratory muscles during quiet breathing, characterized by the use of intercostal and accessory inspiratory muscle or compensatory use of abdominal expiratory muscles. Inspiratory muscle strength was impaired in some of the patients, and it worsened when cardiopulmonary disease was present.

Adult↗