Supplemental oxygen for COPD patients with nocturnal desaturations?
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Humans↗
Biomedical subjects
H Folgering
Publications and source records attributed to H Folgering.
The pathophysiology of hyperventilation syndrome.
Hyperventilation is defined as breathing in excess of the metabolic needs of the body, eliminating more carbon dioxide than is produced, and, consequently, resulting in respiratory alkalosis and an elevated blood pH. The traditional definition of hyperventilation syndrome describes "a syndrome, characterized by a variety of somatic symptoms induced by physiologically inappropriate hyperventilation and usually reproduced by voluntary hyperventilation". The spectrum of symptoms ascribed to hyperventilation syndrome is extremely broad, aspecific and varying. They stem from virtually every tract, and can be caused by physiological mechanisms such as low Pa,CO2, or the increased sympathetic adrenergic tone. Psychological mechanisms also contribute to the symptomatology, or even generate some of the symptoms. Taking the traditional definition of hyperventilation syndrome as a starting point, there should be three elements to the diagnostic criterion: 1) the patient should hyperventilate and have low Pa,CO2, 2) somatic diseases causing hyperventilation should have been excluded, and 3) the patient should have a number of complaints which are, or have been, related to the hypocapnia. Recent studies have questioned the tight relationship between hypocapnia and complaints. However, the latter can be maintained and/or elicited when situations in the absence of hypocapnia in which the first hyperventilation and hypocapnia was present recur. Thus, the main approach to diagnosis is the detection of signs of (possible) dysregulation of breathing leading to hypocapnia. The therapeutic approach to hyperventilation syndrome has several stages and/or degrees of intervention: psychological counselling, physiotherapy and relaxation, and finally drug therapy. Depending on the severity of the problem, one or more therapeutic strategies can be chosen.
Breathing Exercises↗
Longitudinal changes in lung function associated with aspects of swine-confinement exposure.
Several aspects of swine-confinement farming appear to be leading to adverse respiratory effects. This study was set up in a longitudinal design to study the association between certain characteristics of farms or the way they are run and a decline in lung function. A cohort of 171 pig farmers was observed for 3 years. Lung function was measured. Exposure to farm characteristics was determined at the start of the observation period, using data from standardized farm surveys and from diaries kept by the participants. Mean decline in lung function was 73 mL/year for forced expiratory volume in 1 second (FEV1) and 55 mL/year for forced vital capacity (FVC). A longitudinal decline in FEV1 was significantly associated with the use of quaternary ammonium compounds as disinfectants (an additional 43 mL/year) and also with the use of an automated dry feeding system (an additional 28 mL/year). The association with the use of wood shavings as bedding material was not statistically significant. The impact of these characteristics in a longitudinal study provides stronger evidence for causal inference than that shown in previous cross-sectional designs. This may be useful in promoting preventive measures.
Adult↗
Long-term effects of clenbuterol on diaphragm morphology and contractile properties in emphysematous hamsters.
The aim of the present study was to investigate the effect of chronic long-term clenbuterol treatment (1 mg/kg subcutaneously twice a day for 12 wk) on diaphragm morphology and function in emphysematous (EH) and normal hamsters (NH). Clenbuterol increased body weight, diaphragm weight, and skeletal muscle weight in both EH and NH to a similar extent. In the diaphragm, clenbuterol significantly increased myosin heavy chain type I, IIa, and IIx muscle fiber cross-sectional areas by approximately 35-55% in both EH and NH. This response to clenbuterol treatment was not significantly different between EH and NH diaphragm. In EH, twitch force (Pt), maximal tetanic force, and force-frequency curve were significantly reduced compared with NH. In EH, clenbuterol increased Pt by approximately 10%, restoring Pt to NH level. A similar improvement was observed in the force-frequency characteristics. Clenbuterol did not alter contractile properties in NH. In conclusion, long-term clenbuterol treatment resulted in an increased size of all diaphragm muscle fiber types in both NH and EH. Clenbuterol completely abolished the reduced force generation induced by emphysema.
Adrenergic beta-Agonists↗
Endotoxin exposure as a major determinant of lung function decline in pig farmers.
Exposure-response relationships for endotoxin as measured in dust and longitudinal decline in lung function were studied. A cohort of 171 pig farmers was followed over a 3-yr period. Long-term average exposure to dust and endotoxin was determined by personal monitoring in summer and winter, using data on farm characteristics and activities. Mean decline in FEV1 was 73 ml/yr and in FVC 55 ml/ yr. Long-term average exposure to dust was 2.63 mg/m3 (geometric SD [GSD] 1.30), and to endotoxin, 105 ng/m3 (GSD 1.5). Annual decline in FEV1 was significantly associated with endotoxin exposure. An increase in exposure with a factor 2 was associated with an extra decline of FEV1 of 19 ml/yr.
Adult↗
Association between health-related quality of life and consultation for respiratory symptoms: results from the DIMCA programme.
In general practice, diagnosis of chronic obstructive pulmonary disease (COPD) is hampered by underpresentation. A substantial proportion of subjects experiencing respiratory complaints do not consult their general practitioner (GP). In this study, the relationship between disease-specific quality of life and presentation of respiratory symptoms to a GP is investigated. A random sample from the general population (undiagnosed subjects) was screened for symptoms and objective signs of COPD (n=1,155). The lung function of subjects with symptoms of COPD was monitored for 6 months. During this period, 48 new COPD patients with a persistently reduced lung function (forced expiratory volume in one second (FEV1) less than or equal to the predicted value minus 2 SD) were detected. A disease-specific quality-of-life questionnaire (chronic respiratory questionnaire (CRQ)) was administered and clinical and GP consultation data were collected. Multivariate analysis showed that quality-of-life impairments due to dyspnoea and fatigue and variability in lung function (bronchial hyperresponsiveness, reversibility and peak expiratory flow rate variability) were related to medical consultation. Only 31% of the newly detected patients reported that they had ever visited their GP for respiratory complaints. A similarly low percentage was found in the rest of the sample (26%). It is concluded that the mere presence of respiratory symptoms or a (gradually) reduced lung function is insufficient reason for patients to seek medical help. Subjects are more likely to consult their general practitioner once their quality of everyday life is affected or they experience variability in lung function.
Adult↗
Eleven peak flow meters: a clinical evaluation.
Peak flow meters are essential tools in the management of asthma. Many types are on the market. A computer-driven piston pump is normally not available for evaluation of the various meters. Comparison with values from a pneumotachograph is an accepted way of testing peak flow meters. This study aims at comparing 11 peak flow meters, for accuracy and linearity. Seven adult peak flow meters were tested: Miniwright with an equidistant scale (Clement Clarke); Personal Best (Healthscan); Wright Pocket fdE (Ferraris); Vitalograph (Vitalograph); Assess (Healthscan); Pocket Peak flow meter (Micro Medical); and Truzone (Monaghan). Furthermore, four low-range (LR) peak flow meters were tested: LR Miniwright with equidistant scale (Clement Clarke); LR Personal Best (Healthscan); LR Wright Pocket (LR Ferraris); and LR Pocket peak flow meter (LR Micro Medical). Two test series were performed: in the first one, a peak flow meter was connected downstream in series with a Fleisch #4 pneumotachograph. One subject performed 50 partial forced expiratory manoeuvres through this ensemble. In the second series, 50 adult patients and 25 healthy children performed sequential maximal forced expiratory manoeuvres on each peak flow meter, and on the pneumotachograph. A ranking system was devised for the various parameters of agreement of the meters with the pneumotachograph. Substantial differences in the quality of the adult meters were found. The adult peak flow meters with the closest agreement to the pneumotachograph were Personal Best and Micro Medical. In the low-range peak flow meters, the lowest differences were seen in the LR Personal Best and LR Micro Medical.
Adult↗
Effect of low-dose acetazolamide on the ventilatory CO2 response during hypoxia in the anaesthetized cat.
Acetazolamide, a carbonic anhydrase inhibitor, is used in patients with chronic obstructive pulmonary diseases and central sleep apnoea syndrome and in the prevention and treatment of the symptoms of acute mountain sickness. In these patients, the drug increases minute ventilation (V'E), resulting in an improvement in arterial oxygen saturation. However, the mechanism by which it stimulates ventilation is still under debate. Since hypoxaemia is a frequently observed phenomenon in these patients, the effect of 4 mg x kg(-1) acetazolamide (i.v.) on the ventilatory response to hypercapnia during hypoxaemia (arterial oxygen tension (Pa,O2)=6.8+/-0.8 kPa, mean+/-SD) was investigated in seven anaesthetized cats. The dynamic end-tidal forcing (DEF) technique was used, enabling the relative contributions of the peripheral and central chemoreflex loops to the ventilatory response to a step change in end-tidal carbon dioxide tension, (PET,CO2) to be separated. Acetazolamide reduced the CO2 sensitivities of the peripheral (Sp) and central (Sc) chemoreflex loops from 0.22+/-0.08 to 0.11+/-0.03 L x min(-1) x kPa(-1) (mean+/-SD) (p<0.01) and from 0.74+/-0.32 to 0.40+/-0.10 L x min(-1) x kPa(-1) (p<0.01), respectively. The apnoeic threshold B (x-intercept of the ventilatory CO2 response curve) decreased from 2.88+/-0.97 to 0.95+/-0.92 kPa (p<0.01). The net result was a stimulation of ventilation at PET,CO2 <5 kPa. The effect of acetazolamide is possibly due to a direct effect on the peripheral chemoreceptors as well as to an effect on the cerebral blood flow regulation. Possible clinical implications of these results are discussed.
Acetazolamide↗
Pulmonary rehabilitation in chronic obstructive pulmonary disease.
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Activities of Daily Living↗
Bronchial hyperresponsiveness and exposure in pig farmers.
OBJECTIVE: To study the effect of exposure on bronchial responsiveness in pig farmers. METHOD: A group of 196 pig farmers were tested for lung function and bronchial responsiveness to histamine in the summer of 1992. To achieve sufficient contrast in respiratory morbidity and exposure, 96 of the farmers were selected because they had chronic respiratory symptoms and the remaining 100 because they were free from any respiratory symptoms. Personal exposure to dust, endotoxins and ammonia was measured during 1 working day in the summer of 1991 and 1 day in the winter of 1992. Data on farm characteristics were gathered in the same period. RESULTS: After adjusting for age and smoking behaviour, mild bronchial responsiveness, defined as PC10 < or = 16 mg/ml, was associated with the use of quaternary ammonium compounds as disinfectant [prevalence odds ratio (POR) 6.7, 95% confidence interval (CI) 1.4-32.8], use of wood-shavings as bedding (POR 13.3, CI 1.3-136.7), use of automated dry feeding (POR 2.8, CI 1.0-7.8), use of pellets as feeding material (POR 4.8, CI 1.1-21.1) and location of air exhaust via pit or roof in the confinement units (POR 2.7, CI 1.2-6.3). The association with the use of disinfectants other than quaternary ammonium compounds was not significant (POR 2.4, CI 0.7-8.4). No associations between bronchial responsiveness and measured exposure to dust, endotoxins or ammonia were discernible. CONCLUSION: Protective measures, designed to prevent airway disease in confinement farming, should be based on information about the operational and other characteristics of farms that are related to high exposure and health effects. Specifically, the use of quaternary ammonium compounds as disinfectant, the use of wood-shavings as bedding and the use of automated dry feeding should be discouraged.
Adult↗
The chronic fatigue syndrome and hyperventilation.
Chronic fatigue syndrome (CFS) is characterized by severe fatigue, lasting for at least 6 months, for which no somatic explanation can be found. Because hyperventilation can produce substantial fatigue, it seems worthwhile to investigate the relationship between it and CFS. It might be hypothesized that hyperventilation plays a causal or perpetuating role in CFS. CFS patients, non-CFS patients known to experience hyperventilation, and healthy controls were compared on complaints of fatigue and hyperventilation. CFS patients and non-CFS patients known to experience hyperventilation offered substantial complaints of fatigue and hyperventilation, both to a similar degree. Physiological evidence of hyperventilation was found significantly more often in CFS patients than in healthy controls. However, no significant differences between CFS patients with and CFS patients without hyperventilation were found on severity of fatigue, impairment, number of complaints, activity level, psychopathology, and depression. It is concluded that hyperventilation in CFS should probably be regarded as an epiphenomenon.
Adult↗
Inotropic effects of salbutamol on rat diaphragm contractility are potentiated by foreshortening.
The aim of this study was to investigate whether the positive inotropic effects of the beta 2-adrenoceptor agonist salbutamol are increased by foreshortening of the diaphragm, and to determine the mechanism of action of these effects. Diaphragm strips were studied either at optimal resting length (Lo) or at approximately 70% Lo. In an initial experiment (Experiment I) salbutamol was added to the tissue baths in concentrations of 10 micrograms/L or 80 micrograms/L. In a second experiment (Experiment II), the effect of salbutamol (80 micrograms/L) was measured in the presence of 1 microM ryanodine, a sarcoplasmatic reticulum (SR) Ca(2+)-release inhibitor. Each experiment had a time-matched control group. Foreshortening reduced twitch force (Pt), maximal tetanic force (Po), and force-frequency curves. Salbutamol increased Pt and Po both at Lo and approximately 70% Lo. These inotropic effects were significantly greater after foreshortening. The force-frequency curve was shifted upward by salbutamol at both lengths. Force-frequency curves relative to maximal percent of Po were depressed by salbutamol at stimulation frequencies of 80 to 160 Hz. Ryanodine blocked the inotropic effect of salbutamol at both muscle lengths, indicating that these inotropic effects are probably mediated by increased SR Ca2+ release.
Adrenergic beta-Agonists↗
Asymptomatic bronchial hyperresponsiveness in adolescents and young adults.
The clinical significance of asymptomatic bronchial hyperresponsiveness (BHR) is not well-known. The aim of this study was to explore, in a cross-sectional analysis, the characteristics of adolescent subjects with asymptomatic BHR, as compared to nonhyperresponsive subjects and those with symptomatic BHR. The subjects were selected by date of birth from the register of general practitioners. The hypothesis that both asymptomatic and symptomatic BHR are related to early childhood lower respiratory tract infections was also tested, in a historical cohort analysis. Respiratory morbidity was studied in early childhood and BHR in adolescence and young adulthood, in a population of 551 subjects aged 10-23 yrs. Morbidity had been recorded prospectively since birth in the general practice. Data on chronic respiratory symptoms, smoking behaviour, airways obstruction, BHR and allergy were collected during this investigation. BHR was present in 42% of the subjects, of which 70% were asymptomatic. The occurrence of symptomatic BHR was related to acute bronchitis in early childhood, allergy, airways obstruction and recent asthma, acute bronchitis and hay fever; whereas, asymptomatic BHR was not. Characteristics of subjects with asymptomatic BHR did not differ significantly from those without BHR, with respect to these factors. We conclude that asymptomatic bronchial hyperresponsiveness in adolescence and young adulthood is not related to lower respiratory infections in early childhood. Furthermore, subjects with asymptomatic bronchial hyperresponsiveness have similar characteristics to those without bronchial hyperresponsiveness, but differ strongly from subjects with symptomatic hyperresponsiveness. Asymptomatic bronchial hyperresponsiveness may not be the link between early childhood lower respiratory morbidity and asthma in later life, nor a risk factor for later asthma.
Acute Disease↗
The effect of low-dose acetazolamide on the ventilatory CO2 response curve in the anaesthetized cat.
1. The effect of 4 mg kg-1 acetazolamide (I.V.) on the slope (S) and intercept on the Pa,CO2 axis (B) of the ventilatory CO2 response curve of anaesthetized cats with intact or denervated carotid bodies was studied using the technique of dynamic end-tidal forcing. 2. This dose did not induce an arterial-to-end-tidal PCO2 (P(a-ET),CO2) gradient, indicating that erythrocytic carbonic anhydrase was not completely inhibited. Within the first 2 h after administration, this small dose caused only a slight decrease in mean standard bicarbonate of 1.8 and 1.7 mmol l-1 in intact (n = 7) and denervated animals (n = 7), respectively. Doses of acetazolamide larger than 4 mg kg-1 (up to 32 mg kg-1) caused a significant increase in the P(a-ET),CO2 gradient. 3. In carotid body-denervated cats, 4 mg kg-1 acetazolamide caused a decrease in the CO2 sensitivity of the central chemoreflex loop (Sc) from 1.52 +/- 0.42 to 0.96 +/- 0.32 l min-1 kPa-1 (mean +/- S.D.) while the intercept on the Pa,CO2 axis (B) decreased from 4.5 +/- 0.5 to 4.2 +/- 0.7 kPa. 4. In carotid body-intact animals, 4 mg kg-1 acetazolamide caused a decrease in the CO2 sensitivity of the peripheral chemoreflex loop (Sp) from 0.28 +/- 0.18 to 0.19 +/- 0.12 l min-1 kPa-1. Se and B decreased from 1.52 +/- 0.55 to 0.84 +/- 0.21 l min-1 kPa-1, and from 4.0 +/- 0.5 to 3.0 +/- 0.6 kPa, respectively, not significantly different from the changes encountered in the denervated animals. 5. It is argued that the effect of acetazolamide on the CO2 sensitivity of the peripheral chemoreflex loop in intact cats may be caused by a direct effect on the carotid bodies. Both in intact and in denervated animals the effects of the drug on Sc and B may not be due to a direct action on the central nervous system, but rather to an effect on cerebral vessels resulting in an altered relationship between brain blood flow and brain tissue PCO2.
Acetazolamide↗
Pharmacotherapy of respiratory muscles in chronic obstructive pulmonary disease.
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Adrenergic beta-Agonists↗
Treatment of mild asthma with inhaled corticosteroids: is discontinuation of therapy possible?
BACKGROUND: This study investigated if long-term therapy with inhaled corticosteroids could be discontinued in mild asthma when patients are in a clinically stable phase of the disease. Data were derived from a 2-year randomized, controlled, bronchodilator intervention study in family practice. METHODS: The experimental (stop-steroid) group consisted of 19 asthmatic patients who had used inhaled corticosteroids daily during at least the year preceding this study and who stopped using these drugs because of participation in the bronchodilator intervention study. The control (no-steroid) group consisted of 70 patients with asthma who had not used corticosteroids in the year preceding the study. At the start of the study (8 weeks after stopping steroids), the two groups were completely comparable in all other relevant characteristics. During the 2-year study, patients were treated only with a bronchodilator (salbutamol or ipratropium bromide). Outcome measures were: exacerbations, symptoms, annual decline in forced expiratory volume in 1 second (FEV1), annual change in nonspecific bronchial responsiveness (PC20-histamine), and the need for additional corticosteroid therapy because of symptoms of increased airway obstruction. RESULTS: In the stop-steroid group, 12 of 19 patients (63%) dropped out during the study period because of a deterioration of their clinical condition and need for additional (inhaled) corticosteroid treatment. In the no-steroid group, only eight patients dropped out for this reason (11%). In the stop-steroid group, who did not use steroids for at least 1 year, the annual FEV1 decline was much larger than in the comparison subjects (165 vs 40 ml/yr). CONCLUSIONS: Stopping maintenance treatment with inhaled corticosteroids may not be advisable in all patients with mild asthma. Instead of stopping or interrupting treatment, family physicians are advised to determine the minimal effective daily dose of inhaled corticosteroids for each individual patient that provides adequate control of the disease.
Administration, Inhalation↗
Evaluation of the suitability of weekly peak expiratory flow rate measurements in monitoring annual decline in lung function among patients with asthma and chronic bronchitis.
BACKGROUND: Early detection and treatment of patients with asthma or chronic bronchitis who have a rapid annual decline in lung function is essential in order to improve their long-term prognosis. This annual rate of decline can be assessed accurately by monitoring the forced expiratory volume in one second (FEV1) which is a routine procedure in hospital respiratory laboratories but not in general practice. General practitioners usually measure patients' peak expiratory flow rate (peak flow) to evaluate lung function. If annual decline in lung function can be assessed by monitoring peak flow, this method could be used in general practice for detecting patients at an early stage who have a rapid decline. AIM: A study aimed to investigate the long-term correlation between FEV1 and peak flow among a group of patients in Nijmegen, the Netherlands. METHOD: FEV1 and peak flow were monitored in 53 patients with moderate asthma and 78 patients with moderate chronic bronchitis over four years. FEV1 was measured in a laboratory once every six months and peak flow was measured by patients once a week. The correlation between the two sets of measurements was studied for each patient. RESULTS: Four-year data for 83 of the 131 patients were analysed; the other 48 patients received inhaled steroids during the second half of the study period so their data were not considered for all the analyses. Of the 83 patients, 35 (42%) showed a decrease in both FEV1 and peak flow. Thirty six patients (43%) showed a decrease in FEV1 and an increase in peak flow. Four patients (5%) showed an increase in FEV1 and a decrease in peak flow and eight patients (10%) showed an increase in both rates. Approximately similar results were seen in a separate analysis of all 131 patients during the first two years of the study. CONCLUSION: No long-term correlation was found between FEV1 and peak flow. Peak flow is not capable of detecting annual decline in lung function. Therefore it cannot be used to detect patients with asthma or chronic bronchitis who have a rapid annual decline in lung function. Spirometers, which measure peak flow and FEV1, could be used in general practice. These would allow general practitioners to continue measuring peak flow in order to assess short-term changes in lung function while providing an important means for monitoring FEV1 to assess long-term changes in lung function.
Adult↗
[High-resolution computerized tomography of the lungs: current diagnostic possibilities].
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Costs and Cost Analysis↗