Noninvasive measurement of respiratory muscle performance after exhaustive endurance exercise. (33/2225)

The use of noninvasive techniques to measure respiratory muscle performance after different types of endurance exercise has not been entirely successful, as the results have not consistently indicated diminished performance for similar types of exercise. The aim of the present study was 1) to compare different, noninvasive methods to assess respiratory muscle performance before and after an exhaustive cycling endurance test (which has previously been shown to induce diaphragmatic fatigue) and 2) to determine which of the tests best reflect published results of measurements of diaphragmatic fatigue. Twelve healthy subjects participated in the study and performed three different test series in a random order on three different days. These tests were performed before, and 5, 40 and 75 min after an exhausting task (a cycling endurance run at 85% of maximal oxygen uptake (V'O2,max)). The tests of the three test series were 1) breathing against a constant inspiratory resistance to task failure, 2) determination of 12-min sustained ventilatory capacity, and 3) spirometric and maximal inspiratory and expiratory mouth pressure measurements. The only measurement that was affected by exhaustive cycling was the time to task failure breathing against inspiratory resistance. It was significantly reduced from (mean+/-sD) 364+/-88 s before exercise to 219+/-122 s at 5 min after cessation of exercise. It is concluded that the constant-load resistive breathing test to task failure is the only noninvasive respiratory muscle performance test evaluated in this study which shows a decrease in respiratory muscle performance after exhaustive endurance exercise.  (+info)

Dynamic hyperinflation and flow limitation during methacholine-induced bronchoconstriction in asthma. (34/2225)

Although persistent activation of the inspiratory muscles and narrowing of the glottic aperture during expiration have been indicated as relevant mechanisms leading to dynamic hyperinflation in acute asthma, expiratory flow limitation (EFL) has recently been proposed as a possible triggering factor for increasing endexpiratory lung volume (EELV). To establish whether the attainment of maximal flow rate during tidal expiration could elicit dynamic elevation of EELV, breathing pattern, change in EELV by measuring inspiratory capacity (IC) and occurrence of EFL by the negative expiratory pressure (NEP) method were monitored in 10 stable asthmatic subjects during methacholine-induced, progressive bronchoconstriction in seated position. Change in dyspnoea was scored using the Borg scale. At maximum response forced expiratory volume in one second (FEV1) fell on average by 45+/-2% (p<0.001 versus control), while IC decreased 29+/-2%, (by 0.89+/-0.07 L, (p<0.01 versus control)). Only 2 subjects exhibited EFL at the end of methacholine challenge. In 7 subjects EELV started to increase before the occurrence of EFL. Dyspnoea, which increased from 0.2+/-0.1 to 5.5+/-1.0 (Borg scale) at maximum response (p<0.001), was significantly related to the level of bronchoconstriction as assessed by change in (delta)FEV1 (r=0.72; p<0.001) and to dynamic hyperinflation as measured by deltaIC (r=0.50; p<0.001). However, for both deltaFEV1 and deltaIC the slope of the relationship with increasing dyspnoea was highly variable among the subjects. It is concluded that in acute methacholine-induced bronchoconstriction, dynamic hyperinflation may occur in the absence of expiratory flow limitation and that expiratory flow limitation does not represent the triggering factor to generate dynamic hyperinflation. In these circumstances, dyspnoea appears to be related to the increase in end-expiratory lung volume and not to the onset of expiratory flow limitation.  (+info)

Effects of weight loss on body composition and pulmonary function. (35/2225)

BACKGROUND: The relationship between obesity, impaired respiratory function and weight loss is established. OBJECTIVE: Some aspects need further elucidation: the different impact of the pathological modifications of body compartments (total and regional fat mass and lean body mass) on respiratory function, the choice of a restricted diet, the relationship between the modifications of body compartments and the variations in respiratory parameters after weight loss. METHODS: The restricted diet was elaborated according to the traditional Mediterranean diet. In a series of 16 obese patients, respiratory function was assessed by spirometry; body composition was assessed by dual-energy X-ray absorptiometry, allowing the direct estimation of total and segmental body fat and lean body mass. RESULTS: Weight loss was sustained mainly by fat mass decrease, mostly upper body fat. Total and truncal lean body mass were not affected. Lung volumes and function were improved. A correlation was observed between lean body mass and respiratory parameters, and was unmodified after weight loss. CONCLUSIONS: Mediterranean-style restricted diet was well accepted and enabled a selective decrease in fat mass, with a good improvement in lung function. Truncal fat (as well as abdominal fat) was decreased, while truncal lean body mass (i.e. respiratory muscles) were not affected, as expected in obese subjects with respiration problems.  (+info)

Formoterol and salmeterol in partially reversible chronic obstructive pulmonary disease: A crossover, placebo-controlled comparison of onset and duration of action. (36/2225)

BACKGROUND: In contrast to the well-known activity profile in asthma, the precise efficacy and optimum dose schedules of long-acting beta(2)-agonists in chronic obstructive pulmonary disease (COPD) are not clear. OBJECTIVE: In this study, we aimed to compare the onset and the duration of action of a single inhalation of formoterol and salmeterol in COPD patients having partially reversible airway obstruction. METHODS: In a double-blind, randomized, crossover and placebo-controlled study design, the respiratory functions of 22 patients (mean age 57.3+/-5.4 years) having mild to severe COPD (5 mild, 8 moderate and 9 severe) and partially reversible airway obstruction [mean baseline reversibility of forced expiratory volume in 1 s (FEV(1)) 19.3+/-3.1%] were evaluated after inhalation of 12 microg formoterol and 50 microg salmeterol. RESULTS: Regarding the onset of bronchodilator action, the mean absolute increase of 0.20 liters in FEV(1) 10 min after inhalation of formoterol was significantly higher than baseline and that of placebo (0.04 liters), whereas that of salmeterol (0.11 liters) did not reach statistical significance. At 20 min, both formoterol (0.25 liters) and salmeterol (0.20 liters) produced a significant increase in FEV(1) compared with baseline and with that of placebo (0.04 liters). The peak bronchodilator effects occurring at 60 and 120 min following formoterol (0.39 liters) and salmeterol (0.40 liters) inhalation, respectively, were significantly higher than the corresponding levels of placebo (0.02 and -0.12 liters, respectively). Concerning the duration of action, the 12-hour values of both formoterol (0.25 liters) and salmeterol (0.22 liters) were significantly higher than that of placebo (-0.12 liters). The area under the curve values of FEV(1) of formoterol (3.5+/-1.3 l.h) and salmeterol (3.2+/-1.2 l x h) averaged over 12 h were comparable and higher than placebo values (1.2+/-0.5 l x h). After formoterol inhalation 2 patients experienced tremor and 1 had palpitation; 1 tremor and 1 headache attack were noted after salmeterol. For the pharmacologically predictable side effects, there was no difference between the drugs. CONCLUSIONS: In conclusion, this study revealed that a single dose of 12 microg formoterol and 50 microg salmeterol provided comparable bronchodilation within 12 h and had tolerable side effects in patients with mild to severe COPD having partially reversible airway obstruction.  (+info)

Pulmonary gas exchange in cystic fibrosis: basal status and the effect of i.v. antibiotics and inhaled amiloride. (37/2225)

In order to evaluate the degree and type of gas exchange impairment in cystic fibrosis, ventilation/perfusion relationships in ten patients (mean age 26 yrs, mean Shwachman score 86) were examined. Pulmonary gas exchange was studied using the multiple inert gas elimination technique. High-resolution computed tomography (HRCT) and spirometry, including diffusing capacity, were performed after each gas exchange study for comparison. Examinations were done before and after home i.v. antibiotic treatment (HIVAT, 14 days) and after inhaled amiloride and placebo (14 days), in crossover fashion, clinical status after HIVAT serving as the baseline for the crossover study. Before HIVAT, the mean residual volume was 182% of the predicted value, the mean vital capacity 72% pred and the mean forced expiratory volume in one second 53% pred (p<0.001). The dispersion of pulmonary blood flow at different ventilation/perfusion ratios (V'/Q') ((logarithmic SD of the perfusion distribution (log SDQ)), used as an index for gas exchange impairment, was increased to a mean of 0.72. No linear correlation was seen between ventilation/perfusion inequality, spirometry and HRCT (p>0.05). After HIVAT, log SDQ was significantly improved to 0.66 (p<0.05). After placebo, but not after amiloride, log SDQ, arterial oxygen tension, alveolar-arterial oxygen tension difference and maximal expiratory flows when 50% and 25% of the forced vital capacity tension remain to be exhaled were significantly worse (p<0.05, respectively). Areas with a low V'/Q' were significantly lower after amiloride compared to after the placebo period (p<0.05). Moderate ventilation/perfusion inequality was present in the majority of the studied cystic fibrosis patients. The degree of ventilation/perfusion inequality cannot be estimated from spirometry or high-resolution computed tomography. The low proportion of low ventilation/perfusion ratios indicates that the regular treatment directed towards mucus plugging of small airways is beneficial. An improvement in the ventilation/perfusion relationship was seen after home i.v. antibiotic treatment and inhaled amiloride may possibly have a further positive effect on gas exchange.  (+info)

The effect of the nitric oxide synthase inhibitor, L-NMMA, on sodium metabisulphite-induced bronchoconstriction and refractoriness in asthma. (38/2225)

Refractoriness to indirect bronchoconstrictor stimuli, is a feature of asthma but the mechanism is poorly understood. This study tested the hypothesis that endogenous nitric oxide (NO) produced during a first bronchoconstrictor challenge protects against subsequent challenge and therefore has a role in the refractory process. The effect of an NO synthase inhibitor, N(G)-mono-methyl-L-arginine (L-NMMA), on refractoriness to sodium metabisulphite (MBS) was investigated in 20 subjects with mild asthma. On visit one, the dose of MBS which caused a 20% fall in forced expiratory volume in one second (FEV1) (PD20) was determined. On visit two, the refractory index (RI) to MBS was determined by challenging the subjects twice with their PD20 of MBS, the second challenge proceeding after recovery from the first. Those showing a refractory index of approximately 30% (10 subjects) inhaled either L-NMMA or placebo followed 5 min later by two challenges with their PD20 of MBS in a double-blind cross over study at two further visits. The dose of L-NMMA used was shown to reduce exhaled NO for a duration sufficient to cover the second MBS challenge However, no significant difference was found between L-NMMA and placebo in maximum fall in FEV1% and area under the curve (AUC) during first or second MBS challenges or in RI on the two study days. It is concluded that subjects with mild asthma show refractoriness to sodium metabisulphite, but that endogenous nitric oxide is unlikely to be involved either in the refractory process or in the response to sodium metabisulphite per se.  (+info)

Short-term effect of ozone on the pulmonary function of children in primary school. (39/2225)

The objective of this study was to evaluate the short-term effect of ambient air pollution on the pulmonary function of schoolchildren. We sampled 941 children in primary school in three communities in Taiwan (Sanchun, Taihsi, and Linyuan). The nearby stations of the Taiwan air quality monitoring network provided the hourly ambient concentrations of sulfur dioxide, carbon monoxide, ozone, particulate matter < or = to 10 microm in aerodynamic diameter, and nitrogen dioxide. Spirometry was performed once for each sampled child. We also obtained the status of indoor air pollution and chronic respiratory disease history by using a structured questionnaire. Multivariate linear model analysis was used to evaluate pulmonary function effects of each pollutant in addition to determinants of indoor air pollution and meteorologic conditions. We found a significantly negative association of peak O(3) concentration on the day before spirometry with individual forced vital capacity and forced expiratory volume in 1 sec. The decrease in children's lung function can occur at peak hourly O(3) concentrations < 80 ppb. The slope of lung function decrease for Taiwanese children is approximately 1 mL/ppb for peak hourly O(3) exposure.  (+info)

Prospective assessment of the risk of postoperative pulmonary complications in patients submitted to upper abdominal surgery. (40/2225)

OBJECTIVE: To investigate associations between preoperative variables and postoperative pulmonary complications (PPC) in elective upper abdominal surgery. DESIGN: Prospective clinical trial. SETTING: A tertiary university hospital. PATIENTS: 408 patients were prospectively analyzed during the preoperative period and followed up postoperatively for pulmonary complications. MEASUREMENTS: Patient characteristics, with clinical and physical evaluation, related diseases, smoking habits, and duration of surgery. Preoperative pulmonary function tests (PFT) were performed on 247 patients. RESULTS: The postoperative pulmonary complication rate was 14 percent. The significant predictors in univariate analyses of postoperative pulmonary complications were: age >50, smoking habits, presence of chronic pulmonary disease or respiratory symptoms at the time of evaluation, duration of surgery >210 minutes and comorbidity (p <0.04). In a logistic regression analysis, the statistically significant predictors were: presence of chronic pulmonary disease, surgery lasting >210 and comorbidity (p <0.009). CONCLUSIONS: There were three major clinical risk factors for pulmonary complications following upper abdominal surgery: chronic pulmonary disease, comorbidity, and surgery lasting more than 210 minutes. Those patients with three risk factors were three times more likely to develop a PPC compared to patients without any of these risk factors (p <0.001). PFT is indicated when there are uncertainties regarding the patient's pulmonary status.  (+info)