Ventilatory Capacity Research Articles

Immunological and respiratory changes in animal food processing workers.

A group of 35 men employed in the processing of animal food was studied to assess the relation between respiratory findings and immunological status. The most frequent positive skin prick reactions to occupational allergens were to fish flour (82.9%), followed by carotene (77.1%), corn (65.7%), four-leaf clover (62.9%), sunflower (54.3%), chicken meat (31.4%), soy (28.6%), and yeast (22.7%). Increased total IgE serum levels were found in 14/35 (40.0%) animal food workers compared to 1/39 (2.6%) in a healthy population (p less than 0.01). A significantly higher prevalence of chronic respiratory symptoms was found among the exposed workers compared to control workers. There was however, no significant difference in the prevalence of chronic respiratory symptoms between animal food workers with positive and negative skin tests to house dust or to fish flour or among those with increased or normal IgE (except for dyspnea). The frequency of acute symptoms associated with the work shift was high among the animal food workers but similar by immunological status. There were significant mean across-shift reductions for all ventilatory capacity tests, being particularly pronounced for FEF25. Workers with positive skin tests to fish flour antigen had significantly larger across-shift reductions in FEF25 than workers with negative skin reactions. An aqueous extract of animal food dust caused a dose-related contractile response of isolated guinea pig tracheal muscle in vitro. Our data suggest that, in addition to any immunological response animal food dust may produce in vivo, it probably also causes direct irritant or pharmacological reactions on the airways as suggested by our in vitro data.

Effect of Cigarette Smoking on Working Capacity

Physiological responses to exercise were measured in 39 males (19–45 years old) working as cleaners in the Faculty of Medicine, Kuwait University. There was a graded reduction in maximum oxygen intake (VO2max) of smokers. This reduction was greatest in those who smoked 20 or more cigarettes per day. A statistically significant decrease (p < 0.05) was recorded in forced expiratory volume (FEV1) and forced vital capacity (FVC) between smokers and nonsmokers. The results of this study provide quantitative evidence of the adverse effect of smoking on physical working capacity and show the impairment of ventilatory capacity caused by smoking.

Surgery for bullous disease of the lung.

Between July 1986 and December 1990, 22 patients underwent 23 operative procedures for bullous disease at Harefield Hospital. Their ages ranged from 21 to 71 years (mean 49.8 years). There were 18 males and 4 females. All patients were operated upon for symptoms of exertional dyspnoea. Four patients belonged to functional class IV, 11 to class III and 3 to class II. In 80% of patients, computed tomography was performed as part of the preoperative assessment. The bullae were dealt with in 13 patients on the right side, in 7 on the left and in 2 bilaterally. Six patients were treated by a modified Monaldi procedure and 17 by bullectomy. There was no operative mortality. Mean hospital stay was 14.8 days. Two patients required a second operative procedure during their hospital stay for persistent air leak and pneumothorax. One of these had a Monaldi procedure in the first instance but underwent bullectomy later. All patients improved symptomatically, 10 patients moving up two grades and 12, one grade. Mean FEV1, FVC and MVV were significantly improved postoperatively, but there were no significant changes in RV or TLC. A graduated exercise test was performed in 4 patients. Improvements were seen in ventilation and oxygen consumption at anaerobic threshold and maximum exercise. Surgery for bullous disease improves symptoms by reducing airway obstruction and increasing ventilatory capacity on exercise.

Immunological and respiratory findings in swine farmers

The prevalence of respiratory symptoms and ventilatory capacity abnormalities in relation to immunological status was studied in 32 swine farmers and in 39 controls. A large number of swine farmers reacted to swine confinement building antigens (swine hair, 34%, swine confinement agents, 28%) but also to other extracts such as animal food (78%) and corn flour (37%). Control workers also reacted to these antigens in similar frequencies. Increased serum IgE levels were found in 3 swine farmers (9.4%) and all 3 had positive skin tests to at least one of the swine antigens. Among control workers one (2.6%) had an increased serum IgE level; this worker exhibited a positive skin reaction to swine food antigen. Swine farmers with positive skin reactions had across-shift reductions of FEF50 and FEF25 significantly larger than those with negative skin tests (P less than 0.01). Preshift measured ventilatory capacity data (FEV1, FEF50, FEF25) in swine farmers with positive skin tests were significantly lower (compared to predicted) than in those with negative skin tests. Additionally, we showed that a water-soluble swine confinement building antigen causes a dose-related contraction of nonsensitized guinea pig trachea smooth muscle studied in vitro. Our data indicate significant differences in lung function between swine workers with positive and negative skin tests. We suggest that skin testing may be helpful in identifying workers at risk for developing lung disease.

Evaluation of a New Weaning Index Based on Ventilatory Endurance and the Efficiency of Gas Exchange

We hypothesized that the ventilatory capacity needed to wean from mechanical ventilation (mv) depends on two variables: ventilatory endurance and the efficiency of gas exchange. We also hypothesized that these variables could be assessed from data readily available at the bedside, including tidal volume (VT) on mv and during spontaneous breathing (sb), ventilator peak inspiratory pressure (Ppk), and patient negative inspiratory pressure (NIP). Ventilatory endurance was evaluated using a modified pressure-time index: PTI = TI/Ttot x Pbreath/NIP, where Pbreath = Ppk x VTsb/VTmv. Defining VE40 as the minute ventilation needed to bring PaCO2 to 40 mm Hg, the efficiency of gas exchange was evaluated by calculating VE40/VTsb = (VE x PaCO2)mv/VTsb x 40. Because high levels of inspiratory effort might cause patients to reduce VTsb and thereby compromise CO2 elimination, we devised a weaning index (WI) that combines ventilatory endurance and the efficiency of gas exchange: WI = PTI x (VE40/VTsb). The study population comprised 38 patients with chronic obstructive pulmonary disease, adult respiratory distress syndrome, pneumonia, neuromuscular disease, and miscellaneous other conditions. They had been mechanically ventilated more than 3 days and were considered by clinical criteria to be ready for weaning. Of 46 weaning trials, 19 were successful, 2 were partially successful, and 25 failed. PTI and VE40/VTsb were higher in patients who failed (p less than 0.05), but neither variable alone had sufficient sensitivity or specificity to predict the outcome of weaning trials accurately.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory Muscle Conditioning and the Work of Breathing: A Critical Balance in the Weaning Patient

Normal ventilatory function depends on a balance between ventilatory demand and ventilatory capacity. The respiratory muscles play a critical role in achieving this balance. For patients experiencing ventilatory dysfunction, interventions that improve respiratory muscle function and therefore increase ventilatory capacity may be one way of restoring the balance and promoting ventilatory function. Respiratory muscle conditioning, or training the muscles to improve their strength and endurance, may be a useful clinical intervention in the weaning patient. Results of research show that muscle training may increase the ability of some patients to resume spontaneous ventilation. Continued research is needed to identify the appropriate training protocols for patients experiencing an acute imbalance between ventilatory demand and capacity.

Lung function in adult idiopathic scoliosis: a 20 year follow up.

Severe idiopathic scoliosis may lead to respiratory failure, which can be treated by assisted ventilation. Twenty four patients with surgically untreated idiopathic scoliosis who had been examined in 1968 were re-examined in 1988 to assess changes in lung function and risk factors for respiratory failure. The patients were aged 15-67 years in 1968 and had a scoliotic angle of 10-190 degrees and a vital capacity of 1.0-6.0 litres. Spirometric values and scoliotic angles were determined in 1968 and 1988, and arterial blood gas tensions in 1988. The decline in spirometric values over the 20 years was of the same magnitude as the predicted decline due to aging. Arterial blood gas tensions in 1988 were strongly correlated with the scoliotic angles and spirometric indices recorded in 1968. Hypoxaemia and hypercapnia was seen in four patients in 1988 (then aged 43-67 years) and these were the four patients who had a vital capacity below 43% predicted in 1968. The remaining 20 patients had blood gas values within normal limits. Two further patients had died from respiratory failure before 1988, so a total of six patients had developed respiratory failure. In a multiple logistic analysis vital capacity expressed as % predicted in 1968 was the strongest predictor of the development of respiratory failure, followed by the scoliotic angle. Respiratory failure occurred only in patients who had a vital capacity below 45% predicted in 1968 and an angle greater than 110 degrees. Thus respiratory failure develops in adults with scoliosis with a large angle and a low vital capacity when normal aging reduces the ventilatory capacity further. Such individuals merit close follow up.

A Ten-Year Follow-up Study of Cotton Textile Workers

A follow-up study of respiratory function in cotton textile workers was performed 10 yr after the original cross-sectional study (1975 to 1985). There were 35 nonsmoking female and 31 smoking male textile workers restudied from the original group of 116. The majority of those lost to follow-up had left the industry. The prevalence of byssinosis among the female workers at the time of follow-up was 15/35 (42.9%) compared with 8/35 (22.9%) at the time of the initial study (p = 0.063). For men the byssinosis prevalence at follow-up was 16/31 (51.6%) compared with 8/31 (22.9%) at the time of the initial study (p = 0.03). Similarly, the prevalence of almost all other respiratory symptoms was significantly higher at the follow-up than at the time of the initial study. Significant across-shift decrements in FEV1 and FVC were documented at both surveys. The mean annual decline in ventilatory capacity was greater than expected for both female (FVC: -0.036 +/- 0.005 L/yr; FEV1: -0.059 +/- 0.009 L/yr) and male workers (FVC: -0.059 +/- 0.008 L/yr; FEV1: -0.068 +/- 0.006 L/yr) (Mean +/- SE). The mean total airborne dust concentration measured at the time of the follow-up study was 3.95 mg/m3 with an average respirable dust concentration of 0.97 mg/m3. We conclude that continued exposure to high dust concentrations in the cotton textile industry is associated with an increasing prevalence of respiratory symptoms and progressive impairment of lung function. The increase in respiratory impairment was seen both in smokers and nonsmokers.

Effect of respiratory training with a mouth-nose-mask in tetraplegics

Ten tetraplegics, 8 males and 2 females, with a median age of 32 years participated in a scheduled 6 weeks training programme with a respiratory muscle training mouth-nose-mask (RMT-mask) with a fixed expiratory and an increasing inspiratory resistance set by the tetraplegic in accordance to his/her increasing ability during the training period. During the 6 weeks the tetraplegics required to use the RMT-mask for 15 minutes three times a day. Before and after each training session they measured peak flow (PEF). Lung volumes, ventilatory and diffusion capacity were measured before and after the 6 weeks training period. The training resulted only in a significant change in the PEF, which increased with 11% from 371 l/min before to 412 l/min in average after the 6 weeks of training (p less than 0.025). This statistically significant increase was confirmed by the measurements of PEF performed by the tetraplegics themselves during the training period. In addition there was an increase in PEF from before to immediately after each 15 minutes training session, this trend reached statistically significance (p less than 0.025) in the third '2 weeks period'. These results might indicate a possibility of improving the tetraplegics ability to cough by use of a simple RMT-mask, which in turn might prevent certain lung complications including pneumonia, and atelectasia.

Improved Respiratory Muscle Endurance of Highly Trained Cyclists and the Effects on Maximal Exercise Performance

Insufficient respiratory muscle endurance (RME) may be one of the factors limiting ventilation during peak athletic performance. Our purpose was to determine whether the RME of highly trained cyclists could be enhanced and if so, to determine the effects of improved RME on their maximal exercise performance. Ten male cyclists (maximal oxygen consumption (VO2max) greater than 60 ml/kg-1) began the study by performing 3 tests. These were VO2max, RME measured as maximal sustainable ventilatory capacity (MSVC) and maximal exercise endurance (tlim) measured by an endurance cycling test to exhaustion at 90% of their maximal power output. Five subjects then completed 4 weeks of isocapnic hyperpnea training (16 session) and 5 subjects were controls. Following this training interval, each subject repeated the initial tests. After the RME training, the MSVC increased from 155 +/- 11 to 174 +/- 12 l/min (p = 0.004) for the training subjects while there was no change in the controls (155 +/- 26 and 150 +/- 34 l/min). There were no changes for any of the 10 subjects in either the maximal exercise performance (VO2max = 66.1 +/- 4.7 to 66.5 +/- 4.8 ml.kg-1) or the maximal exercise endurance (tlim = 335 +/- 79 to 385 +/- 158 sec). In conclusion, 4 weeks of respiratory muscle endurance training increased respiratory muscle endurance but had no effect on the maximal cycling performance of highly trained cyclists.

Contribution of quasi-static tissue hysteresis to the dynamic alveolar pressure-volume loop

We obtained dynamic and flow-interrupted (quasi-static) pressure-volume loops from the lungs of anesthetized paralyzed open-chest mongrel dogs by measuring tracheal flow and pressure and alveolar pressure (PA) in three different regions using alveolar capsules. We used continuous tidal ventilation to obtain dynamic PA-volume loops and used the single-breath-interrupter technique to construct quasi-static pressure-volume loops for the same tidal volume (VT). We used three different VT's (15 and 20 ml/kg and inspiratory capacity) under control conditions and a VT of 15 ml/kg after methacholine-induced bronchoconstriction. We found that quasi-static hysteresis was negligible under control conditions for VT of 15 and 20 ml/kg. Quasi-static hysteresis became more important (36 +/- 11% of the corresponding dynamic PA-volume loop) during inspiratory capacity ventilation and after induced bronchoconstriction (27 +/- 12% of the corresponding dynamic PA-volume loop). We conclude that during tidal breathing near functional residual capacity "true" static hysteresis is negligible and that purely viscoelastic processes can explain lung mechanical behavior. For higher volume ventilation and after methacholine-induced constriction, quasi-static hysteresis accounted for a more important portion of dynamic tissue hysteresis. This suggests either that a more complex model, e.g., one including plastic processes, should be invoked or that the lung exhibits longer viscoelastic time constants as peak distending stresses become greater.

Respiratory Effects of Occupational Exposure to Tobacco Dust

The ventilatory capacities of 195 tobacco factory workers exposed to tobacco dust and 190 Libyan men not exposed to tobacco dust were measured. In both groups, the forced vital capacity (FVC) and forced expiratory volume in 1 s were found to be correlated with age, stature, sitting height and body surface area. Those exposed to tobacco dust have decreased ventilatory capacity values as compared with age-matched unexposed workers. The duration of exposure to tobacco dust does not appear to have any significant effect on the ventilatory function. There was no significant difference in the lung function test values between the smokers and nonsmokers in both groups. The flow-volume curves were constructed for the unexposed and exposed groups of workers. At 25% FVC, in the group exposed to tobacco dust, there was a decrease in air flow by 20.8% as compared to age-matched normal unexposed Libyans. This indicates that the small airways are affected by exposure to tobacco dust. Flow-volume curves are useful in the assessment of lung function status.

Exercise performance and breathing patterns in cystic fibrosis: Male‐female differences and influence of resting pulmonary function

Despite improved prognosis for patients with cystic fibrosis (CF), they continue to suffer from progressive decline in pulmonary function and exercise tolerance. Beyond puberty, female patients have greater loss of pulmonary function and higher mortality than males, yet no one has studied male-female differences in exercise tolerance among patients. We therefore compared the responses to progressive exercise in 58 male and 52 female patients with CF and analyzed the influence of resting pulmonary function and gender on these responses and on breathing patterns during exercise. Within each of three pulmonary function groups (group 1: FEV1 greater than or equal to 65% predicted; group 2: FEV1 = 50-64% predicted; and group 3: FEV1 less than 50% predicted), female patients had lower exercise tolerance than males. This was reflected in the overall group for each gender: males' peak work load was 130 +/- 64 W, females' 111 +/- 32 W (P = 0.04); males' peak oxygen consumption, 36.9 +/- 11.4 mL/kg/min and females', 31.0 +/- 7.4 mL/kg/min (P = 0.0006). There was no interactive effect between gender and pulmonary function. Neither respiratory rate nor tidal volume differed between sexes. Male and female patients, irrespective of disease severity, employed similar proportions of their ventilatory capacity at exhaustion; group mean minute ventilation to maximum voluntary ventilation ratio ranged from 62.9 to 78.3%, with no apparent relationship to disease severity.

Interpleural analgesia improves pulmonary function after cholecystectomy

The purpose of this study was to examine the effects of interpleural bupivacaine on analgesia and ventilatory capacity after cholecystectomy. Forty-two patients undergoing elective cholecystectomy were randomly assigned to two groups: one to receive interpleural administration of bupivacaine-adrenaline mixture (Group 1 = 22 patients) and the other standard administration of intramuscular meperidine (Group 2 = 20 patients) for postoperative pain relief. The intensity of pain was evaluated by a visual analogue scale (VAS) preoperatively as well as at 2, 8, 24 and 48 hr postoperatively. At the same time, FVC and FEV1.0 measurements were obtained for all patients. The group given interpleural bupivacaine had better pain relief with mean VAS of 0.6 +/- 0.9 (mean +/- SD) 1.1 +/- 1.4, 0.6 +/- 0.9 and 0.8 +/- 1.2 compared with 5.2 +/- 2.2, 5.8 +/- 2.7, 5.5 +/- 2.2 and 4.5 +/- 1.8 for patients receiving meperidine (P less than 0.001). The patients in Group 1 also had larger FVC and FEV than those in Group 2: FVC 22 +/- 14.5 per cent vs 32 +/- 15.2 per cent (P less than 0.005), FEV1.0 25 +/- 15.5 vs 38 +/- 14.8 per cent (P less than 0.001) (mean +/- SD). We conclude that the interpleural analgesia can achieve better pain relief with greater ventilatory capacity than a standard analgesic regimen in the first two days after cholecystectomy.

Cervico-Oculo-Acousticus Syndrome with Pregnancy

Cervico-oculo-acousticus syndrome is a very rare entity with only 21 cases described in the world literature. A study of a case of this syndrome with pregnancy is presented. This primigravida, in addition to the classical triad of the syndrome, had other dysmorphic features such as short stature (141 cm), and marked thoracic kyphosis with restricted ventilatory capacity. Her physical activity during pregnancy was guided according to her respiratory status. In spite of marked thoracic kyphosis the cephalo-pelvic relationship was found to be adequate for a vaginal delivery. A healthy male baby weighing 3.8 kg was delivered by an outlet forceps at term. Puerperium was uneventful. The child was clinically normal at the age of 2 years.

Respiratory adaptations to dead space loading during maximal incremental exercise

We examined the effects of dead space (VD) loading on breathing pattern during maximal incremental exercise in eight normal subjects. Addition of external VD was associated with a significant increase in tidal volume (VT) and decrease in respiratory frequency (f) at moderate and high levels of ventilation (VI); at a VI of 120 l/min, VT and f with added VD were 3.31 +/- 0.33 liters and 36.7 +/- 6.7 breaths/min, respectively, compared with 2.90 +/- 0.29 liters and 41.8 +/- 7.3 breaths/min without added VD. Because breathing pattern does not change with CO2 inhalation during heavy exercise (Gallagher et al. J. Appl. Physiol. 63: 238-244, 1987), the breathing pattern response to added VD is probably a consequence of alteration in the PCO2 time profile, possibly sensed by the carotid body and/or airway-pulmonary chemoreceptors. The increase in VT during heavy exercise with VD loading indicates that the tachypneic breathing pattern of heavy exercise is not due to mechanical limitation of maximum ventilatory capacity at high levels of VT.

Effects of Ventilatory Capacity on FES-Induced Lower Extremity Ergometry in Individuals with Spinal Cord Injury

Effects of Ventilatory Capacity on FES-Induced Lower Extremity Ergometry in Individuals with Spinal Cord Injury

Exposure to hydrogen sulphide and respiratory function.

A study was carried out to assess possible effects of low concentrations of hydrogen sulphide on respiratory function. The cohort comprised 26 male pulp mill workers (mean age 40.3, range 22-60 years) with a daily exposure to hydrogen sulphide in the workplace, and 10 volunteers, who had asthma (three men, mean age 40.7, range 33 to 50 years, and seven women, mean age 44.1, range 31 to 61 years). The respiratory function of the pulp mill workers was monitored by measuring forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and bronchial responsiveness after at least one day off work and at the end of a workday. Bronchial responsiveness was tested by challenge with histamine. The 10 asthmatic subjects were exposed in laboratory conditions to 2 ppm of hydrogen sulphide for 30 minutes in an exposure chamber. Airway resistance (Raw) and specific airway conductance (SGaw) were assessed by a body plethysmograph, and the ventilatory capacities were measured with a flow volume spirometer. No significant changes in respiratory function or bronchial responsiveness related to exposure to hydrogen sulphide in the pulp mill workers were found. In the asthmatic subjects, Raw was increased by 26.3% and SGaw was decreased by 8.4% on average after exposure to hydrogen sulphide. These changes were not statistically significant. In two subjects, however, changes were greater than 30% in both Raw and SGaw, indicating bronchial obstruction. It is concluded that exposure for a relatively short time to hydrogen sulphide concentrations appreciably higher than those existing in ambient air do not cause noticeable effects on respiratory function.

Peak inspiratory flow and inspiratory vital capacity of patients with asthma measured with and without a new dry-powder inhaler device (Turbuhaler)

In 101 asthmatic adults with varying degrees of bronchial obstruction, lung function tests including peak inspiratory flow (PIF), inspiratory vital capacity (IVC), peak expiratory flow (PEF), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1) measurements were made. Significant correlations between inspiratory and expiratory volumes were found. In most patients, PIF was less reduced than the expiratory parameters of pulmonary function. When inhalation was performed through the new multi-dose, dry-powder inhalation device, Turbuhaler (PIF-TBH), it was significantly lower than PIF measured without Turbuhaler. In previous studies, PIF-TBH of 30 l.min-1 or more has proven sufficient to produce a therapeutic dose of terbutaline, and to produce significant bronchodilatation. Of 101 asthmatics in the present study, only four had PIF-TBH of less than 30 l.min-1. Although no parameters of spirometry could accurately predict PIF-TBH, there was a tendency for patients with severely impaired ventilatory capacity to produce lower PIF-TBH than patients with normal or near-normal ventilatory capacity. If patients with severely impaired ventilatory capacity are to receive inhalation therapy through Turbuhaler, either PIF or PIF-TBH should be measured, or the effect should be carefully monitored.

INTERPLEURAL CATHETER FOR ANALGESIA AFTER CHOLECYSTECTOMY: THE SURGICAL PERSPECTIVE

Sixteen otherwise healthy women undergoing cholecystectomy were randomized to receive postoperative analgesia either by continuous infusion of papaveretum (n = 8), or by continuous interpleural infusion of bupivacaine (n = 8). Postoperative pain was assessed by linear analogue and ventilatory capacity. Changes in body protein were measured by in vivo neutron activation analysis. Clinical course was also noted. Pain scores were significantly lower in the interpleural group over the first 48 h (P less than 0.02). Ventilatory capacity was also significantly better for the first 24 h (P less than 0.025). There was no evidence of shortened postoperative ileus; hospital stay and postoperative fatigue were similar for the two groups. Weight and protein losses over a 2 week period were similar in the two groups. It is concluded that the apparent advantages in patient comfort and mobility offered by interpleural infusion are most marked in the first 48 h postoperatively, with an advantage in ventilatory capacity over the first 24 h.