Ventilatory Capacity Research Articles

Airways obstruction, coal mining, and disability.

It has recently been suggested that the inhalation of coal in the absence of complicated coal workers' pneumoconiosis (CWP) or smoking can lead to disabling airways obstruction. The cause of such obstruction has been variously attributed to emphysema or bronchitis. The frequency of significant airways obstruction in a group of United States coal miners seeking compensation for occupationally induced pulmonary impairment was therefore determined. In a sample of 611 "Black Lung" claimants there was only one subject who was a non-smoker and who in the absence of other non-occupationally related diseases,--for example, asthma and bronchiectasis--had sufficient airways obstruction to render it difficult for him to carry out hard labour. An alternative explanation for his reduced ventilatory capacity other than coal dust or smoking may be available. If the inhalation of coal dust in the absence of smoking and complicated CWP ever induces sufficient ventilatory impairment to preclude a miner from working, it is indeed rare.

Impaired ventilatory capacity after recovery from Guillain-Barré syndrome

A 48-year-old woman who failed to disclose significant past medical history presented for laparoscopic-assisted vaginal hysterectomy with general anesthesia. After the uneventful induction of anesthesia, her trachea could not be intubated due to an extremely anterior larynx, and she was allowed to awaken. However, she developed upper airway obstruction and displayed marked muscle weakness with inadequate tidal volumes and marginal oxygen saturation. A history of prior Guillain-Barré syndrome was disclosed by the attending gynecologist. The patient's recovery was complicated by the development of postobstructive pulmonary edema and by respiratory insufficiency requiring the use of mask continuous positive airway pressure (CPAP). Despite vigorous diuresis, her respiratory status and muscle weakness did not significantly improve until she received a trial of aminophylline by infusion, after which she was able to be weaned from mask CPAP support. The patient was discharged home and returned 8 weeks later for surgery. She underwent awake fiberoptic intubation, after which general anesthesia was induced and maintained without complication. An aminophylline infusion was used in the perioperative period until the patient was successfully awakened and her trachea extubated. The frequency of residual muscle weakness after apparent full recovery from Guillain-Barré syndrome is discussed, along with the rationale for the use of aminophylline in this patient's clinical management.

Chest illness in infancy and chronic respiratory disease in later life: an analysis by month of birth.

Cohorts born at different times of year differ in their risk of exposure to seasonal respiratory infections in early life, but are likely to have similar socioeconomic status and lifestyle thereafter. We investigated the long-term consequences of acute chest illness in infancy for later development of chronic respiratory disease by analysing variations by month of birth in hospital admissions for respiratory illness (total n = 49,866), chronic respiratory symptoms and ventilatory function among British school children (n = 11,482) and middle-aged adults (total n = 55,829). Admission for bronchiolitis in the first year of life was three times more common for infants born September to November (autumn) than those born March to May, yet people born in the autumn experienced fewer respiratory symptoms and had better ventilatory function. In two surveys of middle-aged men, forced expiratory volume in one second/forced ventilatory capacity (FEV1/FVC) was significantly (P = 0.025) higher among autumn births. Hospital admissions for chronic bronchitis/emphysema and pneumonia varied little with season of birth. Admissions for asthma were significantly (P < 0.05) more common among children and young adults born in the autumn. These findings do not support the hypothesis of a causal link between chest illness in infancy and the later development of chronic bronchitis and emphysema. The variation in asthma admissions with month of birth deserves further investigation.

Respiratory effects of coal dust exposure: clinical effects and diagnosis.

During the past two decades, growing evidence has been reported on the role of respirable inorganic dust in the development of airflow obstruction, impaired diffusion capacity, chronic bronchitis, and emphysema, irrespective of the extent of possible pneumoconiotic abnormalities. These nonpneumoconiotic effects associated with dust exposure in miners and the relationship between dust exposure and mortality are reviewed. When pneumoconiotic changes can be visualized by different radiologic techniques, including computed tomography (CT) and high-resolution CT, assessment of the respiratory impairment in coal workers at present requires evaluation of the ventilatory and gas exchange capacity.

Peak expiratory flow rate of jute mill workers in Calcutta.

Ventilatory capacity of 32 control and 318 asymptomatic male jute mill workers of the Calcutta area, India was measured by Wright's Peak Flowmeter. Mean values of peak expiratory flow rate (PEFR) was 514 +/- 66.41 l/min in Control and 475 +/- 66.02 l/min and 462 +/- 67.42 l/min in exposed non-smoker and smoker workers respectively. The relationship of PEFR with age, height, duration of exposure and smoking habit were studied. Multiple regression techniques were used to determine the form of the relationship of age, height, exposure and smoking habit with PEFR. The findings have been compared with those of Indian and foreign authors. The possible reasons of difference includes smoking habit, occupational exposure, physical background and residence in polluted area etc.

Long-term intramuscular electrical activation of the phrenic nerve: efficacy as a ventilatory prosthesis.

The efficacy of a system for long-term intramuscular activation of the phrenic nerve as a ventilatory prosthesis was evaluated in seven dogs. (The safety and reliability of this system is addressed in a companion paper.) Five dogs underwent chronic bilateral intramuscular diaphragm stimulation (IDS) for 61 to 183 days at stimulus parameters selected to evoke at least 120% of the animal's basal ventilation. Two dogs maintained as controls did not undergo chronic stimulation. The ability of IDS to provide long-term ventilation without diaphragm fatigue was evaluated in terms of the ventilatory capacity of IDS, the effects of chronic IDS on diaphragm contractile properties, and the phrenic nerve recruitment properties of chronic IDS electrodes. Hemidiaphragms with electrodes placed within 2 cm of the phrenic nerve trunk could be completely activated by 25 mA pulses having a 100 microsecond pulse width. The tidal volume evoked by IDS in this study was 167% (+/- 48 s.d.) of that required for full-time basal ventilation without diaphragm fatigue. Evoked tidal volume increased after 8 to 9 weeks of chronic IDS for stimulus pulse intervals longer than 50 mS. Electrode recruitment properties were stable for both active and passive implanted electrodes. We conclude from these studies that with properly placed electrodes IDS is capable of providing reliable full-time ventilatory support without fatiguing the diaphragm.

Training‐induced modifications in cardiorespiratory and ventilatory measurements in Thoroughbred horses

The effects of training and detraining on ventilation during a standardised exercise test were investigated. Ten healthy Thoroughbred horses underwent 5 standardised treadmill exercise tests (SET): SET1, at the start of the experimental period; SET2, after 3 weeks acclimatisation; SET3, after 3 week of aerobic training; SET4 after 3 weeks of anaerobic (i.e. interval) training; and SET5, after 3 weeks of detraining. The SETs were carried out in an air-conditioned laboratory on a treadmill inclined at 6 degrees. Respiratory airflow, tidal volume (VT), respiratory frequency (RF) and expired minute volume (VE) were obtained using a face mask and 2 ultrasonic pneumotachographs. Peak oxygen uptake (VO2 peak) and carbon dioxide production (VCO2 peak) values were calculated on a breath-by-breath basis, using a mass spectrometer. Heart rate (HR) was continuously measured with a polar horse tester. Oxygen pulse (VO2/HR) and ventilatory equivalent for O2 were calculated from the collected data. Venous blood was sampled before and after the SET for lactate, pH and haemoglobin determinations. The results indicated that trained horses showed significant modifications of all values, except VT, RF and VE. This study suggests that, in horses, the increase in VO2 induced by training seems to be mainly due to cardiovascular and haematological changes rather than to ventilatory changes. Consequently, while all the other systems implicated in exercise physiology can be efficiently improved and trained, the ventilatory capacity has only limited ability to adapt to training.

Organic dust disease of airways.

Exposure to aerosols of organic dusts such as coffee, tea, spices, soy, fur, and animal food in an occupational setting can affect the respiratory health of industrial workers. Based on our experience with workers from many small industries processing organic materials, we discuss the clinical features and possible mechanisms responsible for the respiratory impairment associated with these types of dust exposure. Significantly higher prevalences for most chronic respiratory symptoms were found among exposed workers than among control workers. Smoking appears to aggravate these symptoms. A large number of exposed workers complained of acute symptoms which developed during the work shift. In exposed workers, significant across-shift reductions in lung function were recorded for all spirometric tests, but particularly for the flow rates at 50% and 25% of vital capacity on maximum expiratory flow-volume curves. Comparison of preshift measured ventilatory capacity tests with predicted normal values indicates that these workers demonstrate obstructive changes affecting primarily flow rate at low lung volumes. The data suggest that exposure to organic aerosols in industrial settings, particularly in conjunction with smoking, may be associated with the development of chronic obstructive lung disease.

Factors influencing work capacity in adolescent idiopathic thoracic scoliosis.

The factors contributing to reduced work capacity (disability) in adolescent idiopathic thoracic scoliosis are poorly understood. We performed a cross-sectional study using multivariate analysis to identify the individual and additive influence of spinal deformity, pulmonary impairment, and muscular function on work capacity in 79 subjects with idiopathic scoliosis (angle of scoliosis 45 +/- 18.5 degrees, SD). Work capacity was measured using an incremental cycle test, and the cardiorespiratory response to exercise was compared with that of normal subjects. Work capacity was reduced (% Wcap, 86%; 95% CI 81.9 to 89.7), indicating significant disability. The % Wcap was unrelated to the nature and extent of spinal deformity (p > 0.05). Leg muscularity and pulmonary impairment had an additive influence on work capacity, the relationship with muscularity being the stronger of the two. Independently of muscularity and pulmonary impairment, a high heart rate response at submaximal work rates was also associated with a reduced work capacity. Ventilation was normal for metabolic demands. During exercise, the tidal volumes of scoliotic subjects were reduced in proportion to the vital capacity. We conclude that disability occurs with mild to moderate idiopathic scoliosis and appears to be related to a combination of reduced ventilatory capacity, reduced muscularity, and cardiovascular deconditioning. These findings suggest that physical activity should be encouraged in subjects with idiopathic scoliosis to maintain peripheral muscle and cardiovascular conditioning, thereby minimizing disability.

Respiratory function in sewage workers.

Respiratory symptoms and ventilatory capacity were studied in a group of 74 sewage workers employed in cleaning the city sewage system of Zagreb, Croatia. Workers were studied by their work stations: closed channels (N = 26), drainage (N = 31), and other sewage workers (N = 17). The prevalence of chronic respiratory symptoms was higher in closed channel and drainage workers than in controls, particularly for chronic cough (range: 41.9-46.2% vs. 14.3%), chronic phlegm (range: 38.7-46.2% vs. 14.3%), chronic bronchitis (range: 32.3-42.3% vs. 8.6%), and chest tightness (range: 29.0-53.8% vs. 0%). In the first two groups of sewage workers there was a high prevalence of acute symptoms which developed during the work shift, being particularly pronounced for eye irritation (range: 16.1-26.9%), dyspnea (16.1-23.1%), dizziness (range: 6.5-23.1%), throat burning (9.7-19.2%), and skin irritation (range: 22.6-26.9%). Baseline ventilatory capacity was significantly decreased compared to predicted values in sewage workers; in particular, values for FEF50 and FEF25 were reduced, suggesting obstructive changes in smaller airways. Our data indicate that sewage workers experience frequent acute and chronic respiratory symptoms and exhibit objective evidence of respiratory dysfunction.

Estimation of ventilatory capacity during submaximal exercise.

There is presently no precise way to determine ventilatory capacity for a given individual during exercise; however, this information would be helpful in evaluating ventilatory reserve during exercise. Using schematic representations of maximal expiratory flow-volume curves and individual maximal expiratory flow-volume curves from four subjects, we describe a technique for estimating ventilatory capacity. In these subjects, we measured maximal expiratory flow-volume loops at rest and tidal flow-volume loops and inspiratory capacity (IC) during submaximal cycle ergometry. We also compared minute ventilation (VE) during submaximal exercise with calculated ventilatory maxima (VEmaxCal) and with maximal voluntary ventilation (MVV) to estimate ventilatory reserve. Using the schematic flow-volume curves, we demonstrated the theoretical effect of maximal expiratory flow and lung volume on ventilatory capacity and breathing pattern. In the subjects, we observed that the estimation of ventilatory reserve with use of VE/VEmaxCal was most helpful in indicating when subjects were approaching maximal expiratory flow over a large portion of tidal volume, especially at submaximal exercise levels where VE/VEmaxCal and VE/MVV differed the most. These data suggest that this technique may be useful in estimating ventilatory capacity, which could then be used to evaluate ventilatory reserve during exercise.

Respiratory function in greenhouse workers.

Respiratory findings were studied in a group of 135 female and 32 male workers employed in greenhouses. In addition 51 women and 30 men were studied as a control group. Exposed women had significantly higher prevalences of chronic cough, dyspnea, chest tightness, and rhinitis (P < 0.01) than the controls. Among the men, only rhinitis was more prevalent in greenhouse workers (P < 0.01) than in controls. Smokers had higher prevalences of all chronic respiratory symptoms than nonsmokers, but the differences were statistically significant only for chronic cough and rhinitis in women and for chronic phlegm in men. There was a high prevalence of acute symptoms during work. A large number of greenhouse workers complained of skin reactions to plants and pesticides (women: 37.8%; men: 34.4%). Workers had significantly lower mean ventilatory capacity measurements (except in the case of forced vital capacity) when compared to standard predicted values. Smokers and nonsmokers had similar values of lung function expressed as percentages of the predicted values. Greenhouse workers exposed for more than 10 years had a significantly lower FEF25, measured as a percentage of the predicted value, than workers exposed for less than 10 years. Our data indicate that occupational exposure to greenhouses may be associated with the development of acute and chronic respiratory symptoms and impairment of ventilatory capacity.

Respiratory symptoms and ventilatory capacity in workers in a vegetable pickling and mustard production facility

A group of 117 women occupationally exposed in a pickling factory were studied for the prevalence of acute and chronic respiratory symptoms and lung function changes. Workers were studied by task which included (1) pickling, (2) mustard making, and (3) packing. Similar prevalences for all respiratory symptoms were seen for the three workers groups, with all groups having significantly higher prevalences of chronic cough (P < 0.05), chest tightness, nasal catarrh, and sinusitis (P < 0.01) than a nonexposed control group from a bottling plant. Prevalences of acute symptoms were greater for pickling than for mustard or packing workers. Measured forced expiratory volume in 1 s and maximum flow rates at 50% and the last 25% of the control vital capacity were in general significantly lower than predicted values for the worker subgroups. Pickling workers exposed for more than 1 year in the industry had greater across-shift reductions for all spirometric parameters tested than those workers exposed for 1 year or less. Our data suggest that extended occupational exposure in the pickling industry results in acute exposure-related respiratory effects and ultimately may lead to the development of chronic respiratory symptoms and changes in baseline lung function.

Bilateral Carotid Body Paraganglioma and Central Alveolar Hypoventilation

A 62-year-old woman with a bilateral carotid body paraganglioma presented, 2 years after the removal of the right one, with signs of right-heart failure. Hypoxemia, hypercapnia, polycythemia and pulmonary hypertension with normal ventilatory capacity were found. Central alveolar hypoventilation was diagnosed on the basis of absence of ventilatory response and sensation to provoked hypercapnia, prolonged breath-holding time and correction of hypercapnia by voluntary hyperventilation.

Respiratory Symptoms and Ventilatory Capacity in Metal Polishers

To evaluate the long-term effects of metal dusts on the bronchopulmonary system and the synergistic effect of cigarette smoke, a comparative study of spirometric measurements in 104 polishers and 90 unexposed controls was carried out in 25 brass and steelware polishing industries at Moradabad in northern India. The two groups were comparable in terms of age, height, smoking habit and socio-economic status. A total of 58.6% of the polishers had one or more respiratory symptoms, compared to only 25.5% of the controls (P < 0.05). Chronic cough was present in 21 polishers (20.2%) as compared to 11.1% of the controls. However, this difference was insignificant. Chronic phlegm was nearly three times as frequent among the polishers as among the controls (17.5% vs 4.4%) (P < 0.005). The prevalence of dyspnoea of varying grades was also significantly higher (16.3% as opposed to 4.4%) among the exposed groups. Chronic bronchitis (6.7%) and occupational asthma (4.8%) were found to be confined to polishers. The polishers also experienced acute respiratory symptoms during the work shift. The prevalence of acute respiratory symptoms was recorded for cough in 19 workers (44.1%) followed by dyspnoea in 14 workers (32.5%) and throat irritation in 11 workers (25.5%). Comparison of the mean values of pulmonary function parameters in the polishers and the controls showed significant differences in the smoking and non-smoking groups (P < 0.001). The polishers exhibited significantly greater acute reductions in various lung functions over the work shift, particularly for forced expiratory flow over the 25-75% portion of the spirogram (FEF25-75%) FEF25% and FEF50%, than did the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced tidal volume increases ‘air hunger’ at fixed P CO 2 in ventilated quadriplegics

The act of breathing diminishes the discomfort associated with hypercapnia and breath-holding. To investigate the mechanisms involved in this effect, we studied the effect of tidal volume (V T) on CO 2-evoked air hunger in 5 high-level quadriplegic subjects whose ventilatory capacity was negligible, and who lacked sensory information from the chest wall. Subjects were ventilated at constant frequency with a hyperoxic gas mixture, and end-tidal P CO 2 was maintained at a constant but elevated level. V T was varied between the subjects' normal V T and a smaller V T. Subjects used a category scale to rate their respiratory discomfort or ‘air hunger’ at 30–40 sec intervals. In 4 of 5 subjects there was a strong inverse relationship between breath size and air hunger ratings. The quality of the sensation associated with reduced V T was nearly identical to that previously experienced with CO 2 alone. We conclude that afferent information from the lungs and upper airways is sufficient to modify the sensation of air hunger.

Analysis of factors limiting maximal exercise performance in cystic fibrosis.

1. Maximal exercise capacity in cystic fibrosis is influenced by both pulmonary and nutritional factors: lung disease by limiting maximal achievable ventilation, and malnutrition through a loss of muscle mass. The associated reduction in everyday activities may result in peripheral muscle deconditioning. 2. We studied 14 stable patients with cystic fibrosis (six males, eight females) and 14 healthy control subjects (seven males, seven females) in order to assess the influence of these factors on exercise performance. Subjects underwent anthropometry to estimate muscle mass, spirometry to assess ventilatory capacity, a 30 s sprint on an isokinetic cycle ergometer to assess maximal leg muscle performance, and progressive cycle ergometry to assess overall exercise capacity. 3. Compared with control subjects, the patients with cystic fibrosis were of similar age and height but weighed proportionately less [% ideal weight (mean +/- SD): 94.3 +/- 9.64 versus 109.5 +/- 11.82] and showed evidence of airflow limitation [forced expiratory volume in 1.0 s (FEV1.0) 72.5 +/- 24.78 versus 112.6 +/- 14.25% of predicted]. 4. The patients with cystic fibrosis did less absolute (5.1 +/- 1.89 versus 7.3 +/- 1.97 kJ) but similar relative maximal (11.5 +/- 3.41 versus 13.1 +/- 3.55 kJ/kg lean body mass) sprint work. During progressive exercise, the group with cystic fibrosis achieved lower absolute [maximal O2 consumption (VO2max.) 1.8 +/- 0.527 versus 3.0 +/- 0.655 litres/min] and relative (VO2max./kg lean body mass: 40.5 +/- 9.23 versus 53.0 +/- 11.62 ml min-1 kg-1) work levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory symptoms and ventilatory capacity in swine confinement workers.

A group of 59 workers (41 men and 18 women) employed in swine confinement areas was studied to assess the presence of acute and chronic respiratory symptoms and the prevalence of abnormalities in ventilatory function. A control group of 46 (31 men and 15 women) unexposed workers was studied for the prevalence of chronic respiratory symptoms. For both male and female swine confinement workers complaints of chronic cough, dyspnoea, and chest tightness were significantly more frequent than among control workers. Male workers also complained more of chronic phlegm. Male swine confinement workers who were smokers had significantly higher prevalences of chronic cough, chronic phlegm, and chronic bronchitis than male non-smoking swine confinement workers. The frequency of acute symptoms associated with the workshift was high among the swine confinement workers with more than half of the workers complaining of cough and dyspnoea associated with work. Significant acute across shift reductions in lung function occurred in swine confinement workers, being largest for FEF25. All Monday preshift ventilatory capacity measurements in male confinement workers were significantly lower than predicted values; FVC and FEV1 were found to be lower than predicted values for women. The data indicate that exposure in swine confinement buildings is associated with the development of acute and chronic respiratory symptoms and impairment of lung function. Smoking appears to aggravate these changes.

Ventilatory capacity and exercise-induced arterial desaturation of highly trained endurance athletes.

Recent evidence suggested that exercise-induced arterial O2 desaturation may occur in highly trained endurance athletes. So, Dempsey brought the hypothesis that the pulmonary capacity for oxygen transport cannot meet superior demands imposed by cardiovascular system in highly trained endurance athletes, and endurance training primarily causes adaptation in the skeletal muscles and in the systemic cardiovascular system, with little change in the pulmonary system. In the present study, we determined the propriety of the hypothesis due to measure the ventilatory capacity of endurance athletes. Sixteen highly trained endurance athletes (ET) and thirteen untrained subjects (UT) volunteered to participate in these experiments. All subjects performed the four experiments, 1) the highest oxygen uptake (peak VO2) during incremental cycle exercise and ventilation (VE), ventilatory equivalent for O2 (VE/VO2) and arterial O2 saturation (SaO2) at which peak VO2 was observed, 2) the maximal voluntary ventilation for 30 sec at rest (MVV), 3) the pulmonary diffusing capacity for CO (DLCO) and expressed per unit of alveolar lung volume (KCO) at rest by the single breath method, and 4) the ventilatory response to hypercapnia (S) at rest by rebreathing method, were measured. The peak VO2 of ET (66.7 ml.min-1.kg-1) was significantly (30.8%) higher than UT (52.4 ml.min-1.kg-1), and VE/VO2 and SaO2 of ET (29.3 and 93.7%, respectively) were significantly lower than UT (34.6 and 95.8%). There were no differences in VE, MVV, DLCO, and S between two groups.

Immunological status and respiratory findings in furriers.

We studied 42 women occupationally exposed in the fur manufacturing industry (mean age: 34 years, mean duration of exposure: 11 years). The highest prevalence of positive immediate skin reactions to antigen of animal hair was found for marten (10%), followed by fox and lamb (7%), mink (5%), and Chinese lamb, domestic fox, and Chinese calf (2%). Precipitating antibodies were demonstrated for lamb (17%), astrakhan (14%), mink, domestic fox and skunk (12%), Chinese lamb (10%), and Chinese calf (7%). Increased total IgE was found in 9.5% of subjects. Chronic symptoms were consistently more prevalent among workers with positive skin tests and positive precipitins than among workers with negative tests. A high prevalence of acute symptoms during the work shift was found among furriers. The prevalence of these symptoms was higher among workers with positive precipitating antibodies than among those with negative studies but not for workers with positive skin tests. Mean acute reductions in ventilatory capacity over the work shift were recorded for most ventilatory parameters. In general, greater drops in respiratory parameters occurred in individuals with positive precipitins (e.g., FEV1: -6.5% vs. -2.8%; positive vs. negative precipitins) but not in those with positive skin tests. Our study suggests that workers in the fur manufacturing industry develop acute and chronic respiratory problems often associated with specific indicators of atopy.