Search

Background: A field survey used a "sleep-breathing" questionnaire to estimate the prevalence of the excessive daytime sleepiness in a sample of middle-aged males., Methods: Eight hundred and fifty men aged 22 to 66 years agreed to answer a questionnaire and have anthropometric measurements. To the question on excessive daytime sleepiness, 90 subjects (10.8%) responded "often" or "almost always"; 740 gave a negative answer., Results: The sleepy subjects were older and had a higher "central" weight. All the sleep-disturbed breathing symptoms and those suggesting sleep disturbances were more frequent in sleepy subjects. Sleepiness was significantly associated with sleep apnea and chronic bronchitis. Logistic regression identified six items independently associated with daytime sleepiness; there were three indirect indicators of sleepiness, age, a history of chronic bronchitis and disruptive movements during sleep., Conclusions: This epidemiologic study in a sample of active middle-aged males confirms the association of daytime sleepiness with a series of respiratory and non-respiratory sleep disturbances. The original findings are the role of a "central" obesity, the association with nightmares, and the role of chronic bronchitis as a determinant of daytime sleepiness., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)

Introduction: This questionnaire-based epidemiological study was aimed at identifying possible sleep disturbance in a sample of active French males., Methods: Eight hundred and fifty male subjects, aged 22 to 66 years, completed a structured sleep questionnaire supplemented by information about their life habits and medical history. The study compared the prevalence of positive responses between an "at risk" group of sedentary people (with no declared leisure exercise) and a control group of "exercising" subjects (with more than 5 hours of planned exercise weekly)., Results: Among the symptoms suggesting sleep-disordered breathing, only the question "Have you ever been told that you snore?" significantly separated the two groups. In addition, the sedentary group declared a history of treated hypertension significantly more often., Conclusions: The present survey identified only one item that differed significantly between a sedentary of men and an exercising group - a history of treated hypertension. The result may be explained by the limitations of a questionnaire survey and by the limited contrast in exercise practice: the "sedentary" subjects had an occupational labour demand (not quantified), and the control group had a relatively modest leisure physical activity., (Copyright © 2010 SPLF. Published by Elsevier Masson SAS. All rights reserved.)

Introduction: This study explored the possibility that occupational exposure to low concentrations of carbon monoxide (CO) could influence the synchronisation of upper airway and lower respiratory muscles and thus induce sleep disordered breathing., Methods: Two hundred and thirty subjects exposed to between 1 and 5 ppm (peaks up to 25 ppm) at work and one hundred and sixteen unexposed controls were studied with a protocol comprising anthropomorphic measurements and a self-completed French translation of the Wisconsin Sleep Questionnaire., Results: The two groups had similar anthropomorphic and lifestyle data with the exception that the exposed group were slightly younger (2.5 years). No differences were found in personal or family history, sleep related breathing disorder (snoring, breathing pauses etc) and disturbed sleep., Conclusions: Occupational exposure to low concentrations of CO do not seem to affect ventilatory drive and the synchronisation of upper airway and respiratory muscles during sleep. It should be recognised that these results were obtained by a relatively insensitive technique (questionnaire); a protocol including polysomnography applied to subjects exposed to higher concentrations of CO could lead to other conclusions.

Introduction: As there are important differences in the prevalence of snoring in the literature we have studied this prevalence and the risk factors in a sample of the active male population of Lorraine., Methods: 850 men, aged 22 to 66 tears, volunteered for the study and completed a questionnaire on the frequency of snoring, their lifestyle and their personal and family histories. The usual anthropomorphic measurements were made together with a non-invasive examination of the upper airways., Results: The prevalence of habitual snoring was 34.6%, increasing with age, weight and the derived indices. We identified, by logistic regression, the factors independently associated with habitual snoring in univariate analysis. These were age, weight, nocturnal nasal obstruction, a medical diagnosis of obstructive sleep apnoea, and hypertrophy of the soft palate and uvula. There was evidence that height had a protective effect but exercise activity did not appear to be significant., Conclusion: The 35% prevalence of habitual snoring in our sample of middle aged men is similar to other studies in the literature using the same methods. The present study confirmed that age, weight, girth, nasal obstruction and nasopharyngeal abnormalities are risk factors. The protective effect of height was a new finding not identified in previous studies.

Obstructive sleep apnoeas affect a significant proportion of the middle-aged population. They are due to the closure of upper airways during sleep and cause fragmented sleep, which leads to excessive daily drowsiness. Sleepiness due to apnoea is acknowledged by 10 to 30% of subjects in epidemiological surveys. It impairs vigilance, and therefore represents a risk factor for traffic, domestic and work-related accidents. In the case of domestic accidents, a study shows an increased number of accidents have been reported by subjects with apnoeas; a second study reports the reduction in the frequency of such accidents after receiving appropriate treatment. Subjects suffering from sleep apnoeas also have a higher frequency of accidents at work. Workers with persistent daily drowsiness were also found to have a higher rate of absenteeism as well.

The prevalence of sleep-disordered breathing (SDB) was evaluated in a male population sample of Lorraine (university staff), with a protocol including a self-completed standardized questionnaire, anthropometry (including neck, waist and hip circumferences) and non-invasive ear, nose, and throat examination. Among 357 subjects present in the institution at the moment of the survey, 334 (93.6%) accepted to participate, and 300 (84%) returned the questionnaires. The anthropometric results corresponded to the French normative values according to gender and age. We chose a value of 32 as limit of the body mass index (BMI) between weight excess and obesity; this limit was exceeded by 7.2% of the subjects. The mean age of the sample was 44.8 (SD 10.1) years; the waist-to-hip ratio was of 0.907 +/- 0.053. The ENT examination found a high prevalence of nasal septum deviations (52.6%), of soft palate (25.2%), and uvula (42%) abnormalities; 32.1% of the subjects had experienced amygdalectomy. The non-responses to the questionnaire were infrequent (less than 2%), except for the questions regarding a history of hypertension (2.6%), weight fluctuations the last 5 years (7.6%), and the number of years in school (12%). The questionnaire included, for each question, the optional answer "don't know"; this answer was chosen for the questions concerning the duration of snoring (37.1%), stopping breathing during sleep (12.7%) and the parental history of narcolepsy (18.7 and 20.7%) and sleep apnoea (33.7 and 36.4%). 5.7% of the subjects declared sleep apnoeas at least once per week: 16.1% had unrefreshing sleep; 10.6% admitted to excessive daytime sleepiness; 41.9% were habitual snorers. These results indicate a prevalence of SDB in our sample which is comparable to the figures obtained in other European studies. Further analysis of our data will indicate if, besides weight excess and its troncular distribution, cigarette smoking and respiratory symptoms, the "minor" ENT abnormalities play a role in the pathogenesis of SDB.

Sleep-disordered breathing includes snoring, upper airway resistance syndrome, sleep hypopneas and apneas, and is a borderline pathology between several disciplines (neurology, pneumology, cardiology, oto-rhino-laryngology, etc.). The common element is an abnormal increase in upper airway resistance during sleep. In mild cases, this increase accelerates airflow and induces vibrations of the pharyngeal structures (snoring); in severe cases the airway is occluded and airflow ceases (obstructive apnea). Sleep apnea syndrome (SAS) is present in 4% of males and 2% females in the general population. The risk factors are an age above 50, male sex, weight excess, presence of respiratory symptoms, tobacco smoking, alcohol consumption, use of hypnotic drugs... Snoring is much more frequent than sleep apnea, present in up to 50% of males aged 50 yr or more; most snorers do not have apneas ("simple" snorers). Apneas end with a micro-arousal; this sleep disruption explains the excess daytime sleepiness of patients with SAS. The daytime sleepiness is responsible for the increased rate of accidents (traffic, domestic, work...) in SAS patients. The second effect of apneas is desaturation, leading to heart rhythm abnormalities, coronary or cerebrovascular accidents, pulmonary vasoconstriction, systemic hypertension, etc. Screening for SAS is justified by its prevalence, by the potentially severe consequences and by the existence of an efficacious treatment: continuous positive airway pressure.

The authors presents an pathologic entity whose importance has been outlined in the last few years: sleep apnea syndromes. They insisted on the level of study of this syndrome in western countries. They presents the etiology, the pathophysiology and the main complication and they emphasizes the risks of traffic accidents due to the fall asleep and the cardiovascular complication. The therapeutical possibilities depending on the evolutive stage has been surveyed.

Urinary cotinine was assessed by a radioimmune assay (RIA) in a random subsample of 63 (out of 285) children aged 5 to 6 from 10 kindergartens in Nancy (N-E France). The result was adjusted for urine concentration by expressing cotinine per mg creatinine. The correlation between two successive determinations was excellent (r = 0.989) and the difference between the two mean values was minimal and non-significant (121.4 +/- 25.9 vs 121.0 +/- 25.0). Expressed in percentage of their mean, the difference between two determinations was on average 8.2%. The urinary cotinine determinations allowed a satisfactory separation of children exposed vs unexposed to parental tobacco smoke.

Respiratory symptoms and lung function of 80 coal workers suspected of pneumoconiosis (pulmonary X-rays classified 0/1 or 1/0 according to International Labour Organisation classification) who worked for at least 10 years at face work (Ts) were studied in comparison with two control groups matched by age (+/- 2 years), height (+/- 5 cm), weight (+/- 10 kg) and smoking habits: the Tn group constituted by 80 coal workers who worked for at least 10 years at face work with normal pulmonary X-rays, and the HTn group constituted by 80 underground miners who worked mainly out of face work with normal pulmonary X-rays. The frequencies of cough, expectoration, chronic bronchitis or dyspnoea were significantly higher in Ts group than in the two others. The one-second forced expiratory volume to vital capacity ratio (FEV1/VC) was lower, closing volume to vital capacity (CV/VC) or to total lung capacity ratios (CV/TLC) were higher in Ts group than in the control groups. Unexpectedly, vital capacity (VC), one-second forced expiratory volume (FEV1), total lung capacity (TLC), compliance, diffusing capacity (DLCO) referred to alveolar volume (VA) were higher. In Ts group, the small rounded opacities were noted in the top part of the lung (56.9%), the irregular ones were distributed on the entire lung (65.5%). There were no relation between the category of small opacities and respiratory symptoms or lung function.

Total lung capacity (TLC) and residual volume (RV) estimations were obtained from single-breath nitrogen washouts in 96 male and 77 female healthy never-smokers with normal spirometry from a non-polluted rural area in north-east France. TLC depended on height (both sexes) and diminished slightly with age in males, with the body-mass index (kg/m2) in females. RV increased with age in both sexes and with weight in males. The RV/TLC ratio was related only to age. When compared with values obtained using multiple-breath helium dilution, our results yielded lower predicted values. The test depends heavily on the subject's co-operation, and errors are frequent if a standard procedure is not observed. This method cannot thus be recommended for routine use in patients with respiratory diseases.

Important divergences in the definition of bronchial asthma, chronic bronchitis and pulmonary emphysema have persisted until the middle 1950's. Definitions were first standardized in 1958 by a group of British experts (CIBA symposium) and made clearer by the WHO Experts Group on Cor Pulmonale in 1961 and by the American Thoracic Society in 1962. The standardized questionnaire proposed by the British Medical Research Council has been widely adopted. For pulmonary emphysema, a precise definition based on anatomical data (dilatation of terminal air spaces with destruction of their walls) has been accepted. Chronic bronchitis is defined in clinical terms (almost daily productive cough 3 months each year, at least on 2 consecutive years; the terms "chronic cough" and "recurrent bronchitis" are still controversial. The greatest difficulties have been encountered in the definition of bronchial asthma; despite a second CIBA symposium (1971) devoted to this problem, it has not been possible to improve on the fairly wide physiological definition put forward in 1958 (bronchial obstruction that varies either spontaneously or under the influence of treatment). For about 15 years peripheral airways obstruction (PAO), sometimes called "small airways disease" has been recognized as a special anatomical and functional syndrome.

The change in maximal expiratory flows after inhalation of gases of various physical properties is studied since 1963. The Montreal team proposed in 1972 the helium-to-air difference in maximal expiratory flows at low lung volumes (delta He) and the volume at which the flows breathing air and the helium-oxygen mixture (the "volume isoflow" - Viso V) as "sensitive tests" for the detection of peripheral airway obstruction. "Density-dependence" (DD) has been widely used subsequently in the study of the site of bronchial obstruction in asthmatics in smokers, in subjects with early chronic bronchitis, subjects with occupational exposures to respiratory irritants, etc. The site of action of bronchodilators according to their nature or route of administration (atropine derivates acting on "central airways", "global" bronchodilation obtained by parenteral administration) was studied using DD. However, the interpretation of these studies was always based on Mead's "equal pressure point" concept minimizing the role played by bronchial wall compliance as put forward by Pride and coll. (1967). The results of certain experimental or clinical studies was found not to agree with the original explanations. Finally, the model of flow limitation recently described by Dawson and Elliott (1977) takes into account gas density and bronchial wall elasticity which determine the speed of waves propagating against flow in elastic tubes, the site of "choke points" and the cross-sectional airway area at this level. Besides methodological problems, the complex nature of mechanisms controlling bronchial flow with gases of different densities and the unavoidable influence of bronchodilators or bronchial wall compliance are major limiting factors for the use of DD in the study of the site of airflow obstruction, and effect of bronchodilator action.

Important divergences in the definition of bronchial asthma, chronic bronchitis and pulmonary emphysema have persisted until the middle 1950's. Definitions were first standardized in 1958 by a group of British specialists (CIBA symposium) and made more accurate by the WHO Experts Group on Cor Pulmonale in 1961 and by the American Thoracic Society in 1962. The standardized questionnaire proposed by the British Medical Research Council has been widely adopted. As regards pulmonary emphysema, a precise definition based on anatomical data (dilatation of terminal air spaces with destruction of their walls) has been accepted. For lack of a better basis, chronic bronchitis is defined in clinical terms (almost daily productive cough 3 months each year, at least on 2 consecutive years); the terms "chronic cough" and "recurrent bronchitis" are still controverted. The greatest difficulties have been encountered in the definition of bronchial asthma; despite a second CIBA symposium (1971) devoted to this problem, it has not been possible to improve on the fairly wide physiological definition put forward in 1958 (bronchial obstruction that varies either spontaneously or under the influence of treatment). For about 15 years peripheral airways obstruction (PAO), sometimes called "small airways disease" has been recognized as a special anatomical and functional syndrome.

Respiratory function (forced vital capacity-FVC; forced expired volume in one second-FEV1; maximal mid-expiratory flow-DEMM; peak flow-DP; maximal expiratory flow at 75-50-25% of vital capacity CV-DEMx) was studied in children of comparable age, sex and height (9 to 12 years) in a polluted zone (the exposed group n = 223) and a neighboring non-polluted zone (the control group n = 211) in the north of Lorraine. There was no significant difference in ventilatory function between the two groups. Amongst other factors capable of influencing the ventilatory function in the children we found an influence of parental smoking habits (particularly the mothers) identifiable in the non-exposed zone, above all in boys. A sub-segment analysis identified that in the absence of parental smoking, there was a negative influence of open coal fires. The discordance between the results of the measures of respiratory function and the prevalence of different respiratory symptoms, of acute infections and absenteeism from school, is probably explained by the interference of other factors which were not controlled in this study (e.g., ethnic factors and physical activity) and by the moderate level of the pollution; an over-reporting of respiratory symptoms by parents in the exposed zone could not be excluded.

The classical assembly used for the single breath nitrogen washout implies the manipulation of valves by the operator, a perfect coordination of respiratory maneuvers by the subject and a rigid standardization of the interpretation of the tracings by the technicians doing the calculations. We present a computerized analysis of the single breath nitrogen test, based on a microcomputer (Apple II 48K) solving most of the problems above. The opening of the valves is operated by the computer program recorded on disk; the tidal volume and expiratory flow are displayed on the screen on line allowing the subject to comply with the requested limits; the nitrogram is displayed at the end of the test, allowing the technician to explain the errors (if any). The program then goes on computing the slope of phase III, the closing volume, total lung capacity and its subdivisions for each trial, and the average values for two or three trials accepted by the operator. The system worked satisfactorily during a pilot study in healthy adults (variability and reproducibility) and was particularly useful in a field survey of children and adolescents.

Peripheral airways obstruction (PAO) is a pathophysiologic syndrome combining normal values of the usual tests (one-second forced expiratory volume, airway resistance) and abnormalities of "sensitive" tests (dynamic compliance, closing volume, forced expiratory flows, response to helium-oxygen mixtures). Clinical data are scarce, and the radiological aspects nonspecific. The natural history of the PAO is not fully understood. Therapeutic measures could be useful, but their efficacy was not yet systematically evaluated. From the theoretic point of view, the notion of bronchiolar obstruction is important in as much as it represents the initial phase of any obstructive process. In practice, the detection of a PAO identifies the "at risk" subject allowing the application of efficient preventive measures.

A patient with pronounced dyspnoea and cyanosis was found to have severe hypoxaemia with normal spirographic values. His past history included arterial hypertension, myocardial infarction and phlebitis of the lower limb. Airways resistance was normal, but maximal expiratory flow rates at low lung volume (Flow-volume curves) were reduced, suggesting "peripheral" airways obstruction. This was confirmed by the presence of pulmonary hyperinflation and mechanical non-homogeneity accompanied by unevenly distributed ventilation, as shown by alveolar nitrogen gradient. There was marked hyperventilation with hypocapnia. Since transfer values (measured by the CO single-breath method) and lung distensibility values were normal, emphysema could be ruled out as a cause of obstruction. Analysis of pressure-flow relationship confirmed that the obstruction of peripheral airways was "intrinsic" in character. It could be due to an increase in lung extravascular fluid (interstitial oedema due to left cardiac failure), or to repeated micro-emboli in the lungs, or to hypocapnia, these three mechanisms possibly being associated.

At the request of its inhabitants, an epidemiological survey was conducted among the children of Carling, a particularly polluted industrialized town in the department of the Moselle in North-East France. Contrary to all expectations, no major toxic effect of industrial pollution on the respiratory health of the children was found. There was some correlation between the fact of living in a polluted area and a claimed respiratory morbidity. However, the potentially harmful effect of atmospheric pollution could not be translated in terms of abnormalities of respiratory function. In contrast, a significant effect of the smoking habits of the parents, and particularly of the mothers, on respiratory symptoms and spirographic data of their children was observed.

The effect of incomplete inspiration and of preceding lung volume history on the different parameters of the expired nitrogen curve after inhaling pure oxygen were studied in 12 healthy non-smokers, aged 21 to 35. The equipment used was attached to a mini-computer enabling the regulation of the measurements and the performance of the tests with immediate calculations on the different indices derived from the curve (VC, RV, TLC, delta N2, CV-closing volume, CV/VC). With each subject three measurements were made: measurements in the normal way (N) after incomplete inspiration (I) and finally after 5 forced inspirations and expirations (previous history - P). The procedure (I) gave values of VC and TLC which were lower than those observed with the other methods and the slope of delta N2 and the CV/VC were higher. After the previous lung volume history (P) VC and TLC were significantly higher, the CV/VC ratio was lower (due to the increase of CV). The measurement technique was not influenced either within sessions or between sessions a week apart.

Two mini-peak flow meters, the Airmed (mini-Wright) and the Medicheck (Pulmonary Monitor), were assessed against a reference electronic spirometer (Spiromatic, based on a pneumotachograph, integrator and an Apple II computer) in a series of 10 healthy subjects and 20 patients with chronic obstructive lung disease. The devices to be tested were mounted in series with the reference instrument; each subject did five trials. It was found that the Airmed instrument overestimated the flows up to 9 l X s-1 (i.e. in patients, average difference 0.86 l X s-1, p less than 0.001; in healthy subjects, average difference 0.35 l X s-1, p less than 0.001). The correlation with the results of the reference instrument was high (r = 0.992) in healthy subjects, whose regression slope was less than unity (0.763). In patients the correlation was satisfactory (r = 0.974), and the slope close to 1 (1.05). The Medicheck overestimated slightly the results of patients (difference 0.17 l X s-1, p less than 0.01); in normal subjects the overestimation was present only below 10 l X s-1 and the difference with the reference instrument nonsignificant (average 0.19 l X s-1). The results were closely related to those of the reference spirometer in both healthy subjects (r = 0.960) and patients (r = 0.936). As for the first instrument the slope of the regression was below 1 in healthy subjects (0.751) and practically one (1.01) in patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A quality control of spirographic examinations in a health centre was carried out by repeating, after a fortnight's interval, measures of vital capacity (CV) and FEV1 (VEMS) in 629 subject of both sexes, aged 18 to 62. Water spirometers were used and their cylinders were regularly calibrated. The first series of spirographic measurements were made during a routine health check (which included other examinations) by 7 technicians who usually do the work, while the second series of measurements was made of fortnight later by the most experienced three. The overall mean values show a significant difference for vital capacity between the first and second measurement; this difference was so for young male subjects (less than 30 years). The scatter was greater for subjects over 50 years of age. The varied results observed for the same subjects obtained by two different technicians, or the same technician, underlines the fact that the scatter of the results depends largely on the technician even though spirographic tests are classically considered easy to perform.

Ageing of the lung function in 5 years was studied in a group of 140 iron-ore miners, aged initially from 36 to 55 years. These men had no respiratory symptom and no pulmonary radiological abnormality. The sample was stratified on age and smoking. These factors were studied by a two-way analysis of variance. Lung function testing was performed twice, at 5 years of interval, in the same conditions. It consisted in: spirometry (for measuring FVC, FEV1, FEV1/FVC); a bronchial challenge test with acetylcholine (measurement of the fall of FEV1 after the test); measurement of total lung capacity (TLC) and residual volume (RV) by the open-circuit helium dilution method, and measurement of the transfer factor of the lung for CO, by the steady-state method (TCO/V). The only indices, whose values significantly changed in 5 years were: FVC, FEV1 and TCO/V. Their decrease rate did not appear to be significantly linked to age nor to smoking. According to these results, it seems that the decline of the pulmonary function is relatively constant during the middle period of life and that it is not strongly influenced by smoking, but only among subjects who remain without any respiratory symptom.

The determination of total lung capacity (TLC) by either the plethysmographic (pleth) or closed-circuit foreign gas (dil) method requires expensive and sophisticated equipment. Since hospitals usually have the facilities to perform chest roentgenograms, we wanted to ascertain if the radiologic method (rad) of BARNHARD et al. [1] could be used in lieu of the more sophisticated methods. Sixty-two men ranging from 21 to 67 years had TLC determined by the plethysmographic method, the closed-circuit foreign gas method in which rebreathing was continued until helium was uniformly distributed throughout the lungs, and the radiologic method. There were 21 normal men, 30 with a clinical diagnosis of chronic bronchitis and 11 with a radiologic diagnosis of emphysema plus chronic bronchitis. The mean value of TLC in the normal men showed no significant differences between the three methods and an excellent correlation between the pleth-rad and dil-rad. In the men with chronic bronchitis, there were no significant differences between the mean TLC of rad (7.166 +/- 1.217 1) and dil (6.704 +/- 1.067 1) of rad and pleth (7.545 +/- 1.165 1). The correlations (p < 0.001) were: dil-rad (r = 0.78) and pleth-rad (r = 0.77). In the men with emphysema, there were also no significant differences between the mean TLC of rad (7.166 +/- 1.217 1) and dil (6.704 +/- 1.067 1) or rad and pleth (7.545 +/- 1.165 1). The correlations (p < 0.001) were: dil-rad (r = 0.78) and pleth-rad (r = 0.77). In the men with emphysema, there were also no significant differences between the mean TLC of rad (8.789 +/- 1.207 1) and dil (7.831 +/- 1.041 1) or rad and pleth (9.403 +/- 1.735 1). The correlations were: dil-rad (r = 0.81, p < 0.01) and pleth-rad (r = 0.91, p < 0.001). This study suggests that in normal individuals and patients with chronic bronchitis or emphysema the radiographic method is a useful and reliable technique for determining TLC when elaborate equipment for measuring lung volumes is not available.

The modification of maximum expiratory flows with low gas density breathing was proposed a decade ago as a test of small airway obstruction. This short review discusses the theoretical bases of the method. Three kinds of approaches have been proposed to interpret the findings: the "equal pressure point" concept of Mead et al. has stressed the role of the resistance upstream and of elastic recoil; the "flow limiting segment" concept of Pride et al. has underlined the role of central airways compliance (the compressed segment acting as a resistor); recently, the "choke point theory" proposed by Dawson and Eliott discusses the role of wave speed propagation in the walls of elastic tubes. All these three interpretations take into account the influence of the density of the gas breathed--a factor governing the drop in transmural pressure between the alveoli and the central airways, and a determinant of the speed of pressure wave propagation. In principle, every reduction in gas density should lead to an increase in maximal flow; this modification would be less marked if the flow in the upstream segment is essentially laminar due to obstruction in the peripheral airways. Several points complicating the interpretation are discussed: a) the flow in the small airways is never strictly laminar; b) the change in gas density (usually-breathing a He-O2 mixture) also influences the length of the upstream segment and the pressure wave speed; c) the influence of the cross sectional area and compliance of central airways cannot be neglected.(ABSTRACT TRUNCATED AT 250 WORDS)

The impact on the respiratory system of complex industrial pollution (dust, sulphur dioxide, nitrogen oxides, hydrocarbons) was assessed by an analytical epidemiological study in a population of school children in the northeast of France. The parents of 375 children aged from 9-12 (middle school course 1 and 2) from the polluted zone and 523 children of the same age in a neighboring zone which was not polluted have filled in standardised questionnaires (respiratory symptoms, previous infections and allergies, frequency of infection in infancy; tobacco habits, professional and educational attainments of the parents, domestic environment). In the exposed children the majority of respiratory symptoms were more frequent (e.g., respiratory sounds in the boys, 15.6% against 7.9% p less than 0.01) and the absenteeism from school was more numerous (66.9% against 59.1% p less than 0.01). However, the interpretation of the results had to take into account the existence of confusing factors: parental smoking habits and the use of coal fires increased the prevalence of symptoms in the polluted zone, whereas a less crowded population worked in the inverse direction; likewise the educational level of the parents was higher in the polluted zone. After adjusting for these confusing factors, the frequency of rhinitis and absenteeism from school was significantly higher in exposed children.

The variability and reproducibility of maximal static respiratory pressure measurements was evaluated in 22 healthy subjects and 17 patients with chronic respiratory disease. The difference between consecutive measurements represented 4 to 8 per cent of the result in healthy subjects and 10 to 11 per cent in patients. The difference between the first and the second measurement was not significant and the two values were highly correlated. At 1 to 3 days interval, the results may differ by 10 to 15 per cent in healthy subjects and 20 to 22 per cent in patients. These differences tend to be greater for expiratory (as compared to inspiratory) pressures and for females (as compared to males). A preliminary assessment of the variability and reproducibility of maximal respiratory pressures is compulsory for a valid interpretation of their change in clinical studies.