Comparison of the bronchial response to running and cycling in asthma using an improved definition of the response to work.
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The bronchial responses to treadmill running and ergometer cycling have been compared in 13 adults with asthma. The exercises were performed on separate days with an interval ranging from three days to six months. The study was designed to ensure that the time course of oxygen consumption during running was replicated during cycling. The response to exercise was estimated by taking serial measurements of the maximum forced expiratory flow rate and forced expiratory volume in one second before and after work. Indices used to describe the response were (b-a)/b and a/b, where b and a were the average lung function before and the lowest value after exercise respectively. There was no significant difference in the lung function of the subjects before running and cycling nor did the duration of exercise or oxygen consumption differ between the two exercises. Eleven of the 13 patients showed a reduction in ventilatory capacity after both forms of exercise. Differences in the lung function responses to the two forms of standard work were trivial and not statistically significant, amounting to only about 1%. It is suggested that previous reports of larger responses to running than cycling were probably due to higher energy expenditures during running. General problems regarding the description and comparison of the responses to exercise are discussed. (+info)
Heart rate as a predictor of mortality: the MATISS project.
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OBJECTIVES: This study sought to verify the independent role of heart rate in the prediction of all-cause, cardiovascular, and noncardiovascular mortality in a low-risk male population. METHODS: In an Italian population-based observational study, heart rate was measured in 2533 men, aged 40 to 69 years, between 1984 and 1993. Data on cardiovascular risk factors were collected according to standardized procedures. Vital status was updated to December 1997. RESULTS: Of 2533 men followed up (representing 24,457 person-years), 393 men died. Age-adjusted death rates for 5 heart rate levels showed increasing trends. The adjusted hazard rate ratios for each heart rate increment were 1.52 (95% confidence interval [CI] = 1.29, 1.78) for all-cause mortality, 1.63 (95% CI = 1.26, 2.10) for cardiovascular mortality, and 1.47 (95% CI = 1.19, 1.80) for noncardiovascular mortality. Relative risks between extreme levels were more than 2-fold for all endpoints considered. CONCLUSIONS: Heart rate is an independent predictor of cardiovascular, noncardiovascular, and total mortality in this Italian middle-aged male population. (+info)
Overdistension in ventilated children.
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Ventilating patients with acute respiratory failure according to standardized recommendations can lead to varying volume-pressure (V-P) relationships and overdistension. Young children may be more susceptible than adults to overdistension, and individual evaluation of the effects of ventilator settings is therefore required. Three studies have applied indices for the detection of overdistension to dynamic V-P curves in ventilated children. Two of those studies compared these indices to those obtained using a reference technique ([quasi]-static V-P curves), and suggested that the c coefficient of a second order polynomial equation (SOPE) and the ratio of the volume-dependent elastance to total dynamic elastance (%E2) were suitable indices for estimating overdistension. (+info)
Ability of single-breath nitrogen closing volume to detect early airway obstruction.
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In order to determine the ability of single-breath nitrogen closing volume (CV) to detect early airway obstruction, the CV was measured in patients with either minimal obstruction of spirometry or with increased residual volume (RV). A total of 39 subjects was included in this study. The mean CV was largest in patients who had reduced maximum mid-expiratory flow rates (MMF). There was no difference in mean CV between smokers and the patients who had large RV but no airway obstruction, although both groups had higher mean CV than ex-smokers. Normal CV was seen in four of 11 patients who had reduced MMF and in four of seven who had large RV but no airway obstruction. All ex-smokers had normal CV while five of 12 smokers had adnormal CV. The results indicate that the closing volume should be used to complement spirometry, rather than to replace it, for screening of early airway obstruction. (+info)
Comparison of peak flow gauge and peak flow meter.
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A comparison has been made of the new peak flow gauge and the Wright peak flow meter. Close correlation was found between measurements made with the two instruments both in normal subjects and in patients. The peak flow gauge is as consistent as the peak flow meter but is cheaper and more portable. It should be useful in survey work in general practice and for loan from hospital outpatient departments where serial measurements are used to monitor patients' progress. (+info)
Exercise hyperpnea in chronic heart failure: relationships to lung stiffness and expiratory flow limitation.
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The changes in breathing pattern and lung mechanics in response to incremental exercise were compared in 14 subjects with chronic heart failure and 15 normal subjects. In chronic heart failure subjects, exercise hyperpnea was achieved by increasing breathing frequency more than tidal volume. The rate of increase in breathing frequency with carbon dioxide output was inversely correlated (r = -0.61, P < 0.05) with dynamic lung compliance measured at rest, but not with static lung compliance either at rest or at maximum exercise. Although decrease in expiratory flow reserve near functional residual capacity in chronic heart failure occurred earlier with exercise than in the normal subjects (P < 0.01), it was not correlated with changes in breathing pattern or occurrence of tachypnea. Tachypnea was achieved in chronic heart failure subjects with an increase in duty cycle because of a greater than normal decrease in expiratory time with exercise. We conclude that in chronic heart failure preexisting increase in lung stiffness plays a significant role in causing tachypnea during exercise. The results of the present study do not support the hypothesis that dynamic compression of the airways downstream from the flow-limiting segment occurring during exercise contributes to hyperpnea. (+info)
Tidal expiratory flow limitation and chronic dyspnoea in patients with cystic fibrosis.
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Cystic fibrosis (CF) eventually leads to hyperinflation linked to tidal expiratory flow limitation (FL) and ventilatory failure. Presence of FL was assessed at rest in 22 seated children and adults with CF (forced expiratory volume in one second (FEV1) range: 16-92% predicted), using both the negative expiratory pressure (NEP) technique and the "conventional" method based on comparison of tidal and maximal expiratory flow/volume curves. In addition, chronic dyspnoea was scored with the modified Medical Research Council (MRC) scale. Measurements were made before and 15 min after inhalation of salbutamol. With NEP, FL was present in only three malnourished patients, who had the lowest FEV1 values (16-27% pred) and claimed very severe dyspnoea (MRC score 5). By contrast, an additional seven patients were classified as FL with the conventional method. Six of these patients had little or no dyspnoea (MRC scores 0-1). Salbutamol administration had no effect on the extent of FL, and the concomitant decrease in functional residual capacity (FRC) was too small to play any clinically significant role. This study concluded that in seated patients with cystic fibrosis, expiratory flow limitation is absent at rest, unless the forced expiratory volume in one second is <30% predicted. If present, expiratory flow limitation is associated with severe chronic dyspnoea. The conventional method for assessing expiratory flow limitation is not reliable and bronchodilator administration has little effect on expiratory flow limitation. (+info)
Determinants of exercise performance in normal men with externally imposed expiratory flow limitation.
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To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at approximately 1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W(max)) and the difference (Delta) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (VL). From Campbell diagrams, we measured alveolar (PA) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W(di)). Four subjects hyperinflated and two did not. EFL limited performance equally to 65% W(max) with Borg = 9-10 in both. At EFL W(max), inspiratory time (TI) was 0.66s +/- 0.08, expiratory time (TE) 2.12 +/- 0.26 s, Pmus approximately 40 cmH2O and DeltaVL-DeltaVm = 488.7 +/- 74.1 ml. From PA and VL, we calculated compressed gas volume (VC) = 163.0 +/- 4.6 ml. The difference, DeltaVL-DeltaVm-VC (estimated blood volume shift) was 326 ml +/- 66 or 7.2 ml/cmH2O PA. The high Pmus and long TE mimicked a Valsalva maneuver from which the short TI did not allow recovery. Multiple stepwise linear regression revealed that the difference between C and EFL Pmus accounted for 70.3% of the variance in DeltaBorg. DeltaW(di) added 12.5%. We conclude that high expiratory pressures cause severe dyspnea and the possibility of adverse circulatory events, both of which would impair exercise performance. (+info)