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International audience; SETTING: Occupational asthma (OA) is most likely to develop in the very early years of exposure. OBJECTIVE: To describe the early incidence of OA among bakers/pastry-makers (BP) and hairdressers and to explore the role of atopy. DESIGN: Following a retrospective follow-up design, subjects were invited to undergo telephone interviews. Those who declared work-related respiratory or rhinitis symptoms and a sample group of others were offered a medical visit for OA investigations. Data from interviews and from medical visits were used to estimate the incidence of OA according to increasing durations of exposure. RESULTS: A total of 866 subjects were interviewed (mean age 25.3 years, 43.8% females), of whom 282 underwent a medical visit. Total estimated incidence rates of 'confirmed or probable' OA during the first 12 years of exposure were high in BP (2.63 per 100 person-years [py]) and in hairdressers (0.58/100 py), particularly in the first 4 years. Atopy is a strong risk factor for incidence among BP but, irrespective of the occupational sector, it does not influence the timing of OA symptoms. CONCLUSION: OA symptoms occur soon after the start of exposure. Our results suggest that atopy does not precipitate the occurrence of symptoms in two different allergen exposure settings.

Ventilatory and mouth occlusion pressure (P0.1) responses to progressive isocapnic-hypoxia and hyperoxic-hypercapnia were compared in eleven healthy sleeping men during the same night. Hypoxic and hypercapnic responses were determined during wakefulness, non-rapid and rapid-eye-movement sleep. The following parameters were measured: minute ventilation (VE), tidal volume (VT), 'duty cycle' (TI/TT), mean inspiratory flow rate (VT/TI) and P0.1, an index of the neuromuscular inspiratory drive. To allow a direct comparison between the two types of chemostimuli, responses were characterized by the value of the different parameters at 'equivalent' levels of hypoxia and hypercapnia, i.e., at levels which produced the same P0.1 during wakefulness: an oxyhaemoglobin saturation (Sao2) of 94% during the isocapnic-hypoxic tests (PETCO2 = 42.5 +/- 1.2 mmHg) was found to be equivalent to a PETCO2 of 47.4 +/- 3.7 mmHg during hypoxic-hypercapnic tests. For both tests, the arousal levels of the stimulus and of P0.1 were similar in all sleep stages. Sleep did not significantly modify P0.1 or breathing pattern responses to hypoxia (Sao2 = 94%). In contrast, at the 'equivalent' level of hypercapnic stimulation, P0.1 (P less than 0.05) and VE (P less than 0.01) responses were significantly impaired, particularly in REM sleep, with a decrease in VT (P less than 0.01) and VT/TI (P less than 0.05) responses. The results suggest that CO2 intracranial receptor mechanisms are more affected by sleep than the O2 peripheral receptor activity.

SummaryThe aim of the study was to evaluate the prevalence, the covariates and determinants of respiratory pauses during sleep in a sample of French middle-aged males.Study subjects were 850 active males, aged 22–66 years; 88.4% of them answered the question on breathing pauses during sleep from a structured, validated sleep questionnaire.Forty-one (=5.4%) subjects reported breathing pauses at least once a week; these “positive responders” were older, heavier and had larger neck- and waist girths as compared to subjects with negative answers. Loud habitual snoring, various sleep disturbances, excessive daytime sleepiness, a doctor diagnosis of sleep apnoea, history of stroke and hypertension were significantly more frequent among subjects with breathing pauses during sleep.The prevalence found in this survey was close to that reported from the UK (5.2%). However, by logistic regression, we identified novel determinants of breathing pauses i.e. habitual snoring, loud snoring, and excessive sleepiness, factors well known in clinical setting, but never previously reported in epidemiologic studies.

International audience; BACKGROUND: Exposure to pollutants in bakeries and hairdressing salons can cause airway syndromes varying from bronchial irritation to asthma. Workplace respiratory health surveillance aims to identify possible cases requiring further investigation. AIMS: To compare the performance of fractional exhaled nitric oxide (FE(NO)) and spirometry for health surveillance of apprentice bakers (ABs) and apprentice hairdressers (AHDs). Determinants of FE(NO) were also identified. METHODS: Symptoms and physician-diagnosed asthma were evaluated by questionnaire. FE(NO) was measured and spirometry was carried out. Subjects with elevated FE(NO) (FE(NO) > upper limit normal), airway obstruction [forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) < 95th percentile] and atopy (history of allergies) were identified. RESULTS: A total of 126 apprentices (59 ABs and 67 AHDs) participated. Twenty-nine (23%) apprentices had abnormal tests: 4 had associated high FE(NO) and airway obstruction, while 25 had either high FE(NO) (n = 15) or airway obstruction (n = 10) alone. Compared with ABs (n = 16), AHDs (n = 13) had more asthma (38 versus 0%; P < 0.05) and atopy (62 versus 6%; P < 0.05). There was no difference in symptoms, smoking FE(NO) or airways obstruction. Among 97 subjects with normal tests, no differences existed between ABs (n = 53) and AHDs (n = 44). Average FE(NO) was increased in atopic non-smokers compared with atopic smokers and non-atopic subjects (P < 0.05). Smoking, a history of allergies, FEV(1)/FVC % observed and respiratory symptoms were the main determinants of FE(NO). CONCLUSIONS: FE(NO) and spirometry were not overlapping dimensions in ABs and hairdressers, each test contributing unique information on the physiological status of the respiratory system. FE(NO) may provide added information on airway inflammation not provided by spirometry.

This questionnaire-based epidemiological study was aimed at identifying possible sleep disturbance in a sample of active French males.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).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.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.

BackgroundOccupational asthma is a common type of asthma caused by a specific agent in the workplace. The basic alteration of occupational asthma is airways inflammation. Although most patients with occupational asthma are mature adults, there is evidence that airways inflammation starts soon after inception of exposure, including during apprenticeship. Airways hyper responsiveness to methacholine is a valid surrogate marker of airways inflammation, which has proved useful in occupational epidemiology. But it is time-consuming, requires active subject's cooperation and is not readily feasible. Other non-invasive and potentially more useful tests include the forced oscillation technique, measurement of fraction exhaled nitric oxide, and eosinophils count in nasal lavage fluid.Methods and designThis study aims to investigate early development of airways inflammation and asthma-like symptoms in apprentice bakers, pastry-makers and hairdressers, three populations at risk of occupational asthma whose work-related exposures involve agents of different nature. The objectives are to (i) examine the performance of the non-invasive tests cited above in detecting early airways inflammation that might eventually develop into occupational asthma; and (ii) evaluate whether, and how, constitutional (e.g. atopy) and behavioural (e.g. smoking) risk factors for occupational asthma modulate the effects of allergenic and/or irritative substances involved in these occupations. This paper presents the study rationale and detailed protocol.DiscussionAmong 441 volunteers included at the first visit, 354 attended the fourth one. Drop outs were investigated and showed unrelated to the study outcome. Sample size and follow-up participation rates suggest that the data collected in this study will allow it to meet its objectives.

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.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.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.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.

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.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.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.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.

The aim of the present study was to test the hypothesis that unmarried (single) men have more sleep-disordered breathing symptoms due to a higher prevalence of obesity and a less healthy lifestyle than men living with a partner. Men (499) aged 23–66 years completed a structured questionnaire, had standard anthropometric measurements and a simple, noninvasive nose-throat examination. Of the 499, 496 subjects answered the question concerning their marital status; 86% of them were married or lived with a partner (reference group) and the other 14% had never been married, divorced, or widowed (“single” group, considered at risk). Single subjects were younger, included slightly more smokers (30 vs. 23%) and more subjects with a history of chronic bronchitis, and less frequently had a large soft palate. The prevalence of sleep-disordered symptoms was not significantly different between the two groups. However, a study involving a larger number of subjects with information regarding alcoholic consumption may be needed to further evaluate this question.

Background: Most studies on habitual snoring have focused on its prevalence. However, from the clinical point of view, the intensity of snoring is of upmost importance, as it suggests the existence of sleep apnoeas. Objectives: The aim of the study was to assess the prevalence of loud snoring using a standard questionnaire and to evaluate the anthropometric and sleep characteristic differences between loud and light snorers in a sample of middle-aged males. Methods: The subjects were middle-aged active male employees. They completed a structured sleep questionnaire and had standard anthropometric measurements. Subjects reporting habitual snoring (≧3 nights/week) were further classified as loud or light snorers. Results: Of the 850 male subjects volunteering, 149 (17.5%) were habitual loud snorers. Loud snorers were older and had a greater waist-to-hip ratio as compared with light snorers. In univariate analysis, loud snoring was associated with gasping/snorting during sleep, breathing stops during sleep, waking up too early, excessive daytime sleepiness and falling asleep while watching TV. Logistic regression identified four independent associates of loud snoring: gasping during sleep, excessive daytime sleepiness, falling asleep watching TV and age. Conclusions: Loud snoring is present in a significant proportion of middle-aged men and is associated with central obesity and age. It disturbs sleep and elicits significant daytime sleepiness. Its association with breathing pauses (univariate) and its independent association with gasping during sleep suggests that loud snoring could be considered a clinical correlate of obstructive sleep apnoeas.

Study objectives: To assess the prevalence of occasional snoring in a group of middle-aged men, and to compare anthropometric variables and prevalence of sleep-related symptoms of subjects who occasionally snore with those of other snoring categories. Design: A field survey of a sample of middle-aged men in France. Participants: Male employees of a local university and subjects from the community attending a preventive medicine center. Participation rate was 93.5%. Measurements: Anthropometric variables were recorded in 499 subjects aged 23 to 66 years (mean, 44.3 years). The subjects completed a standard sleep questionnaire and were classified according to the snoring frequency as never, rarely, sometimes, occasional, several nights per week, and every night. The subjects who snore occasionally represented 8.6% of the total. Results: The anthropometric data of subjects who snore occasionally were similar to those of subjects who habitually snore. When compared with subjects who do not snore, older age and a larger neck girth were significant. Subjects who snore occasionally were also significantly more often subjects who snore loudly, and tended more frequently to have breathing stops during sleep. Conclusions: Our epidemiologic study shows that approximately 9% of a sample of middle-aged men snore occasionally. Subjects who snore occasionally have anthropometric characteristics close to those of subjects who snore habitually. The prevalence of the main sleep-related symptoms is between that of subjects who do not snore and of subjects who snore habitually. In an epidemiologic setting, inclusion of subjects who snore occasionally as subjects who do not snore or subjects who snore habitually will lead to bias. The present results suggest they should be identified and considered as a separate category. (CHEST 2002; 122:562–568)

Asthma has a tendency, to destabilize and get worse at night, probably due to a nocturnal increase in airiway inflammation and bronchial responsiveness. Nocturnal airway narrowing in asthma is often associated with sleep disorders, such as episodes of nocturnal and early morning awakening, difficulty in maintaining sleep, and day time sleepiness. On the other hand, an association has been documented between nocturnal sleep-disordered breathing and asthma. This review highlights the causes of nocturnal worsening of asthma and examines the evidence pointing toward a causal relationship between nocturnal asthma and sleep-disordered breathing.

Sleep-disordered breathing (SDB) and lower socio-professional status have in common a series of risk factors for ill health such as sedentary lifestyle, weight excess, heavy alcohol and tobacco consumption. We hypothesised that SDB will be more prevalent in lower socio-professional groups. A total of 496 male middle aged subjects (23-66 years) were tested with a protocol including a self-completed structured sleep questionnaire (translation of the Madison sleep cohort study form), anthropometry (including neck, waist and hip girth) and a simple, non-invasive nose-throat examination by a specialist physician. The subjects were classified according to the 10 major groups of the ISCO-88 classification (International Labour Office). Our sampling base did not contain subjects in the major groups 1 (senior officials, legislators), 6 (fishery and agricultural workers), and zero (armed forces), thus these groups were not represented in the analysis. To improve the power of the statistical analysis, groups 3 and 4, 5 and 7, 8 and 9 were merged, the analysis thus including four categories. The differences in demographic data were negligible; as expected, smoking was more prevalent in low socio-occupational groups (difference non-significant). A history of chronic bronchitis was more frequent in low socio-occupational groups, while a low physical job labour was more frequent in higher occupational groups. We did not find any differences in the prevalence of sleep-related respiratory disturbances (snoring, sleep apnoeas). This first study of the possible association between socio-occupational factors and sleep disordered breathing was negative, but we believe further studies, on larger samples, with a more homogeneous distribution of social groups are warranted.

In patients with obstructive sleep apnoea (OSA) anatomic and functional upper airway abnormalities are frequent and severe. Invasive methods are used to identify and quantitate the obstruction, to precisely locate its site, etc. as part of pre-treatment or of preoperative evaluations. These methods (lateral skull radiographs, computerized tomography, MRI, fibroscopies, etc) are too expensive and too invasive to be utilized in field surveys. To the classical sleep questionnaires and anthropometric measurements, some simple nose-throat examinations, easily accepted by the volunteers in a population study, could add useful information for the identification of the subjects at risk for sleep-disordered breathing. The present paper is a review of these examinations and of their utility.

The accuracy and precision of transcutaneous pressure measurements of oxygen (Ptc,O2) and carbon dioxide (Ptc,CO2) in the monitoring of nocturnal assisted ventilation in adult patients were evaluated. Transcutaneous measurements obtained with two analysers, Radiometer TINATCM3 (R) and Kontron MicroGas-7650 (K), were compared with arterial blood gases analysed in blood samples withdrawn simultaneously in 10 patients. Sensors were heated to 43 degrees C. Measurements of transcutaneous blood gases and arterial blood gases were collected six times at 1-h intervals. The data obtained with both instruments were similar and did not significantly change over the 5 h test period. Measurement of Ptc,O2 underestimated arterial oxygen tension (Pa,O2) and this underestimation increased with the level of Pa,O2 (p

Summary We compared the effects of the laryngeal mask and tracheal tube on total respiratory resistance in 10 anaesthetised, mechanically ventilated patients undergoing otological microsurgery. The subjects were randomly divided into two groups. In the first group, the tracheal tube (Rusch) was inserted for the first series of measurements. This was then replaced by a laryngeal mask (Intavent) and a second series of measurements was made during the first hour of operation. In the second group, the same protocol was applied with inverse order in the use of the devices. From the measurement of respiratory flow and pressure at the airway opening, total respiratory resistance was calculated by multiple linear regression. The data were corrected to eliminate the previously determined nonlinear resistance of the two devices. Arterial blood pressure, electrocardiogram, oxygen saturation and end-tidal carbon dioxide concentration were continuously monitored. With the laryngeal mask and the tracheal tube, mean (SE) minute ventilation was 9.4(0.9)l.min-1 and 8.1 (0.9)l.min-l, respectively for end-tidal carbon dioxide concentrations between 3.6 and 4.1%. Although the glottic resistance was included in the measurement performed with the laryngeal mask but not with the tracheal tube, mean (SE) total respiratory resistance was not significantly different with the two devices (0.61(0.32) and 0.69(0.35) kPa.l-1.s, respectively). Leakage was avoided with the laryngeal mask because the insufflation pressure never exceeded 1.7 kPa except in one patient suffering from severe chronic obstructive pulmonary disease who had a total respiratory resistance of 1.45kPa.l-1.s. During the first hour of the operation all respiratory variables remained stable irrespective of the device used.

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.

There is no lack of data in the literature reporting on the efficacy of different bronchodilators. However, the discussion concerning the superiority of one bronchodilator over another in patients with chronic bronchitis and airflow obstruction is, and remains, a controversial subject. This has been particularly so since the perfection of synthetic anticholinergics delivered by inhalation without any side-effects. The aim of the present work is to compare the bronchodilator effects of a sympathomimetic, fenoterol (Berotec), and of an anticholinergic, ipratropium bromide (Atrovent), compared to a placebo in twelve unselected chronic bronchitics who had airflow obstruction and were in a stable clinical state. The bronchodilator effect of the two drugs was judged at the same time by variations on forced expired volume (FEV1) which was taken as a reference value, and of the maximum mid-expiratory flow (MEF) measured by spirography and also the variations of pulmonary resistance (delta Rrs) measured by the forced oscillatory method. The comparison of these indices enables the site of action of these agents to be specified. The dose response curve and the duration of action over six hours was assessed for each of the three agents. These were administered in succession and at random over three days by inhalation using an inhalation chamber. All the patients who were included were capable of producing a bronchodilator response but two of them responded only to one agent. The change in the FEV1 was comparable with the two active products. The change in MEF (an index of peripheral airways) was significantly greater following ipratropium.(ABSTRACT TRUNCATED AT 250 WORDS)

The respiratory effects of analgesia with nalbuphine were studied in 9 patients after thoracotomy. The pain score was measured by a visual analogue scale. Ventilatory pattern and occlusion pressure (P0.1) were studied during spontaneous breathing and during CO2 rebreathing, before and 0.5, 1, 2.5, 3.5 and 6 h after a 0.3-mg.kg-1 dose of intravenous nalbuphine. Compared to baseline values obtained before the injection, nalbuphine produced a decrease in the pain score (p0.001) during the 6-hour experiment period. In spontaneous breathing, P.01 was reduced by 15% in 1 h and remained decreased during 3.5 h (p0.05), whilst PaCO2 and ventilation (VE) remained unchanged. The P0.1 responsiveness to CO2 was decreased from 0.5 to 2.5 h after the nalbuphine injection (p0.05), but the VE responsiveness to CO2 was reduced only after 1 h (p0.01). This study shows that, while post-thoracotomy pain was reduced by analgesia, neuromuscular inspiratory drive and chemosensitivity to CO2 were weakened, without any change in spontaneous ventilation. A partial improvement in the thoracopulmonary mechanics induced by the reduction in chest pain could explain the maintenance of ventilatory level in spite of a decreased neuromuscular inspiratory drive.

Six pulse oximeters with finger probes were studied in three groups of 17 hypoxemic patients with COPD aged 50 to 75 years. Transcutaneous arterial oxygen saturation (SpO 2 ) was measured with the Nellcor N101 (oximeter 1a), the Ohmeda Biox III (oximeter 1b), the Nellcor N200 (oximeter 2a), the Critikon Oxyshuttle (oximeter 2b), the Radiometer Oxi100 (oximeter 3a), and the Ohmeda Biox 3700 (oximeter 3b). The SpO 2 was compared with SaO 2 measured in simultaneously withdrawn samples of arterial blood (Radiometer OSM2) at three 20-minute steady-state levels of Flo 2 ranging from 0.21 to 0.40 (SaO 2 , 62 to 100 percent). The bias (mean SpO 2 -SaO 2 difference) and the error in precision (SD of the differences) were both below 4 percent for instruments 1a and 1b and remained below 1.2 and 3 percent, respectively, for the others. A good agreement between SpO 2 and SaO 2 , as reflected by the Bartko intraclass correlation coefficient, was observed in instruments 2a, 3a, and 3b. The individual relationships between SpO 2 -SaO 2 differences and SaO 2 appeared to be linear and parallel. With four instruments (1a, 1b, 2a, and 2b), the mean slope of this relationship was negative, showing a systematic instrumental error: the lower the SaO 2 , the larger the overestimation of SaO 2 . The scattering of the data (precision) principally reflects a subject source of error. In most instruments a technical adjustment could greatly improve instrumental errors and accuracy. The correction of the errors due to between-subject variation would require a system of calibration adjustable by the users to each individual.

Two sets of seven pulse oximeters (Criticare CSI-502; Nellcor-N200; Datex-Satlite; Physio-Control-Lifestat 1600; Critikon-Oxyshuttle; Ohmeda-Biox 3700; Ohmeda-Biox 3740; Radiometer-Oxi; Spectramed-Pulsat; Kontron-7840; Biochem-Ox2000; Invivo-4500; Engström-EOS; Novametrix-505) were studied in two groups of eight healthy subjects, aged 26-50 yrs. The transcutaneous oxygen saturation (SpO2) was compared with arterial oxygen saturation (SaO2) measured in simultaneously with drawn blood samples (OSM2 Radiometer) at four 20 min steady-state levels of inspired oxygen fraction (FIO2) (0.21, 0.10, 0.08 and 0.07; SaO2 99-55%) in a conditioned chamber. Both the error in accuracy (mean SpO2-SaO2 difference), and the error in precision (SD of the differences) remained less than 3% for the two highest FIO2 levels (SaO2 greater than 83%) but, during deeper hypoxia, they were increased to 8% and 5%, respectively. An instrumental systematic bias affected accuracy in particular. We concluded that a good agreement between SpO2 and SaO2, as reflected by the Bartko's intraclass coefficient, was observed in nine instruments.

Mechanical properties of the lung were studied in nine healthy lowlanders during a 6-day sojourn at an altitude of 3,457 m. In comparison to sea-level values, it was found at altitude that 1) lung volumes measured by plethysmography including total lung capacity, vital capacity, and functional residual capacity (FRC) presented small changes not exceeding 300 ml; 2) static and dynamic lung compliances were not modified but static pressure-volume curves of lungs were shifted progressively to the left (the decrease in lung elastic recoil averaged about 2 cmH2O on days 4–6); and 3) maximal midexpiratory flow, forced expiratory volume in 1 s, and maximal expiratory and inspiratory flows were increased and, conversely, airways and pulmonary flow resistances were decreased on most days at altitude. The unchanged FRC in the face of a decreased lung recoil may be explained by an increase in thoracic blood volume at altitude, but other possible mechanisms are discussed. The decrease in resistances and increase in maximal flows may be partly explained by the decreased air density at altitude, but another contributing factor such as a bronchodilatation is also suggested. It is proposed that changes in lung mechanics at altitude may account for some of the changes in the pattern of breathing and mouth occlusion pressure (P0.1) observed during acclimatization of lowlanders to altitude.

The validity of a new method for measuring thoracic gas volume (Vtg) was studied in 18 bronchitic patients with mild to severe airway obstruction. The method entailed submitting the subject to very slow sinusoidal variations of ambient pressure (delta Pam) and studying the relationship between delta Pam and the resulting gas displacement at the mouth (delta Vaw): Vtgapc = PB.delta Vaw/delta Pam.cos phi, where PB is barometric minus alveolar water vapor pressure, and phi is the phase angle between Pam and Vaw. delta Pam of 40 cm H2O at 0.05 Hz were achieved by placing the subject in a 410-I body chamber connected to a large stroke volume reciprocating pump. Pam and Vaw were processed digitally by Fourier transform to obtain their amplitude ratio and phase angle at the frequency of interest. Vtg was also measured by body plethysmography (Vtgplet) during slow panting maneuvers (0.79 +/- 0.19 Hz) and also in order to detect any artifactual frequency dependence at a higher panting frequency (1.71 +/- 0.27 Hz); the agreement between the 2 estimates in all subjects (r = 0.975) suggested that Vtgplet could be taken as a valid reference. Functional residual capacities derived from Vtgapc and Vtgplet were not significantly different (5.113 +/- 1.198 versus 5.260 +/- 1.328 L) and were highly correlated (r = 0.915). Intermethod differences averaged 1.7 +/- 10.5% and were not significantly correlated to functional indices. We conclude that the new method provides accurate Vtg values in patients with chronic airway obstruction.

The effects of hypotension induced by trimetaphan on ventilatory control were assessed in sixteen normal subjects under halothane anaesthesia. The breathing pattern, mouth occlusion pressures, lung mechanics, acid-base balance, and arterial blood gases were analysed before and during trimetaphan infusion. During induced hypotension, the only significant change in the ventilatory variables was an increase in the ratio of inspiratory duration to total cycle duration from 0.39 +/- 0.05 (SD) to 0.42 +/- 0.03; P less than 0.01. The average minute ventilation remained unchanged. No modification in lung mechanics was observed, but all subjects developed a slight but significant hypocapnic alkalosis: PaCO2 was reduced from 5.5 +/- 0.4 to 5.2 +/- 0.4 kPa (P less than 0.001) and pH increased from 7.34 to 7.36 (P less than 0.05), without change in standard bicarbonate concentration. Our data indicate that the reduction in sympathetic nervous system activity induced by trimetaphan infusion in spontaneously breathing man causes only a minor alveolar hyperventilation. The weak respiratory response to hypotension suggests that changing peripheral afferent activity has little influence on the typically rapid breathing pattern induced by halothane.

We studied the correlation between density-dependence parameters (delta He, volume of isoflow) and age, body build, spirography and forced expiratory fows in 69 healthy non-smokers (16 females) aged 18 to 51 years. Density dependence variables showed no significant differences between young (less than 35 years) males and females. Volume of isoflow per cent of forced vital capacity (Viso V % FVC) was poorly significantly related to age (r = +0.25 P less than 0.05) and weight (r = +0.27 P less than 0.05). Significant correlations were found between density dependence at low lung volume and the FEV1/VC ratio (r = 0.31, P = 0.01 for delta He 25%; r = -0.40, P less than 0.001 for Viso V% FVC) or the forced expiratory flows with air (Viso V% FVC vs. FEF 25% r = -0.42, P less than 0.001). These correlations were closer in females as compared to males. Volume of isoflow was well related to delta He 25% (r = -0.64, P less than 0.001), but the relationship with delta He 50% was weaker (r = -0.38; P less than 0.01).

When the whole body is exposed to sinusoidal variations of ambient pressure (delta Pam) at very low frequencies (f), the resulting compression and expansion of alveolar gas is almost entirely achieved by gas flow through the airways (Vaw). As a consequence thoracic gas volume (TGV) may be computed from the imaginary part (Im) of the delta Pam/Vaw relationship: TGV = PB/[2 pi f X Im(delta Pam/Vaw)], where PB is barometric minus alveolar water vapor pressure. The method was tested in 35 normal subjects and compared with body plethysmography. The subjects sat in a chamber connected to a large-stroke-volume reciprocating pump that brought about pressure swings of 40 cmH2O at 0.05 Hz. delta Pam and Vaw were digitally processed by fast Fourier transform to extract the low-frequency component from the much larger respiratory flow. Total lung capacities (TLC) obtained by ambient pressure changes and by plethylsmography were highly correlated (r = 0.959, p less than 0.001) and not significantly different (6.96 +/- 1.38 l vs. 6.99 +/- 1.38). TLC obtained by ambient pressure changes were not influenced by lowering the frequency to 0.03 Hz, adding an external resistance at the mouth, or increasing abdominal gas volume. We conclude that the method is practical and in agreement with body plethysmography in normal subjects.

"Sensitive" and "conventional" lung function tests were compared in a group of 114 males, aged 35-55 years, including healthy non-smokers, asymptomatic smokers with normal spirometry, and smokers with chronic bronchitis with or without mild airflow limitation. In non-smokers, with the exception of a MEF vs. FEV1 correlation, "sensitive" and "conventional" tests were independent of each other. In asymptomatic smokers the phase III slope and the closing volume were significantly related to FEV1, RV/TLC and CO transfer factor. In smokers with chronic bronchitis all the "sensitive" tests were related to the "conventional" tests (with the exception of the total lung capacity). Hyperinflation and CO transfer impairment suggest that early emphysema may accompany mucus hypersecretion in smokers.

'Conventional' (lung volumes, airway conductance, CO transfer factor) and 'small-airway dysfunction' (single-breath N2 washout, maximal expiratory flows with air and a helium-oxygen mixture) tests were performed in a group of asymptomatic male ex-smokers (n = 20) with normal spirometry and compared to those of a similar group of middle-aged nonsmokers (n = 41). The study group had a mean life-long consumption of 13.2 +/- (SD) 8.8 pack-years and had stopped smoking 1-21 years ago, mean 7.3 +/- (SD) 5.8 years. Among the conventional tests, a minimal increase in residual volume and residual volume/total lung capacity ratio was found. Ex-smokers had a steeper phase III slope, a higher closing volume/vital capacity ratio, lower forced flows with air and a higher volume of isoflow, but neither difference between the group means was significant. There was a trend to more abnormal small-airway tests as a function of increased smoking, but only the correlation between percent of predicted closing volume and pack-years reached significance (r = +0.51, p less than 0.05). We conclude that small-airway function normalizes in the long term in most ex-smokers if they become asymptomatic, with less than 10% still having abnormal results years after they stopped smoking.

Mechanical impedance of the respiratory system was measured at 5, 10, 15 and 20 Hz in 47 healthy non-smokers, 20 ex-smokers and 51 current smokers. Besides the resistance and its frequency dependence, the compliance, the inertance and the resonant frequency of the respiratory system were computed using the assumption of a second order linear system. The data were normalized for sex, age and body height on the basis of correlations observed in non-smokers. No significant difference was found in ex-smokers. In smokers the resistance was significantly increased at all frequencies. However, it was normal in a number of subjects with abnormally low maximal expiratory flows. unlike maximal flows, forced oscillations indices were not correlated to tobacco consumption expressed in pack-years. The results do not indicate that impedance measurements breathing air may be specially useful for early detection of airway abnormalities.

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)

To assess the actual sensitivity of forced expiration indices to changes in the resistance of peripheral airways, maximal expiratory flow-volume curves were obtained in 30 normal subjects breathing air and breathing an O2-Ne-SF6 gas mixture having the same density as air but a 45% larger viscosity. The measurements were made using a bag-in-box system to circumvent calibration problems, and the data were processed digitally. Besides the usual forced expiration indices, slope ratios, as described by Mead (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 156-165, 1978), and transit time indices were also computed. Breathing the viscous mixture, the largest changes were seen with the slope ratio measured at 60% forced vital capacity, followed by other slope ratios, the standard deviation of transit times, and maximal flows at low lung volumes. However, when the data were compared using the t test for paired measurements, the most significant changes were found with the forced expiratory volumes at 1 and 2 s, due to their low within-subject variability. These indices may therefore by considered as the most suitable for detecting changes in individuals.

In order to define the minimal frequency response requirements for spirometric measurements, the harmonic content of forced expiratory flow has been assessed in 63 healthy subjects. The amplitude of the harmonics has been found to decrease almost exponentially with increasing frequency. On the average, the cumulated frequency content beyond 10 Hz represented less than 5% of the total frequency content in men, and less than 3% in women. No significant difference has been observed between male smokers and non-smokers. The harmonic content per unit frequency has been found to be correlated to maximal flows at middle and low lung volumes and to maximal mid-expiratory flow up to 4 Hz. For FEV1, maximal flow at 75% of the vital capacity and, particularly, peak expiratory flow rate (PEFR), the correlations were still significant at quite higher frequencies. The data suggest that, except for PEFR, all these indices may be obtained with a good accuracy when the frequency response of the equipment is flat up to 5-7 Hz.

Using an integrated flow pressure-corrected body plethysmograph we obtained total lung capacities (TLC) derived from thoracic gas volumes measured at low, medium, and high panting frequencies in 10 healthy men and in 13 patients with chronic airflow obstruction before and after an aerosol of albuterol. Using a gastric balloon we also assessed gastric-to-mouth pressure ratios (delta Pga/delta Pm). In patients before albuterol, estimated TLC remained unchanged from low to medium and increased (not significantly) from medium to high frequency. Healthy subjects and patients after albuterol showed a significant decrease in TLC from low to medium panting frequencies, which persisted after correcting the data for abdominal gas compression using observed delta Pga/delta Pm. In patients after albuterol the results may be explained, at least in part, by intrathoracic airway compliance and mechanical inhomogeneity of the lung. In healthy subjects a remote possibility is the association of mechanical inhomogeneity and nonuniform pleural pressure.

We investigated two methods of decreasing the error on plethysmographic determinations of thoracic gas volume (TGV) related to cheeks movements during panting maneuvers: lowering gas density in the airways with an 80% He-20% O2 mixture and computing TGV from the in-phase component of the plethysmographic signal (TGVr). The methods were tested by measuring how TGV estimates varied when panting frequency was raised from 0.8 to 2.5 Hz during the same occlusion. The measurements were performed in 6 normal subjects and 12 patients with chronic bronchitis with and without cheeks support and when the airway was connected to an external device simulating an increased cheeks compliance. A small negative frequency dependence of TGV (delta TGV/delta f = -1.2 +/- 0.8%/Hz with cheeks support), most probably unrelated to upper airway walls, was found in normal subjects. Delta TGV/delta f was positive and algebraically larger in patients than in normals, reaching 2.2 +/- 3.4%/Hz without cheeks support and 11.8 +/- 8.0%/Hz with the additional cheeks. The latter value was only 20% smaller when computed on the basis of TGVr, demonstrating the limited usefulness of the phase-based correction. In contrast, breathing He-O2 decreased delta TGV/delta f to approximately 50% of its air value (P less than 0.01) and appears as an effective way to diminish the error in obstructive patients.

Deliberately lowering blood pressure facilitates middle ear surgery. However, bleeding can persist in spite of hypotension in some tachypneic patients. Fentanyl is a powerful morphinomimetic which decreases ventilatory frequency. This work studies the respiratory effects of fentanyl during spontaneous ventilation in 16 anesthetized patients. Their systemic blood pressure was decreased 40 per cent by trimetaphan. One single injection of fentanyl (0.0125 mg) reduced minute ventilation by 26 per cent, mean inspiratory flow rate (VT/T1) and T1/TTOT, but did not modify the pulmonary dynamic compliance. The acid-base balance parameters changed little toward respiratory alkalosis by trimetaphan and returned to their control values after the injection of fentanyl. Thus, a small dose of fentanyl can be combined with controlled hypotension during anesthesia and spontaneous ventilation without respiratory risk or an acid-base inbalance. With this dose, it has an efficient central influence to reduce the breathing frequency and can be used to lessen bleeding.

A model was developed to interpret the difference between volume variations at the mouth and at the chest observed by body plethysmography during inspiration in normal subjects breathing ambient air. The mechanical phenomena were characterized, as usual, by a time constant alpha, the product of airway resistance and alveolar gas compressibility. In contrast to other models, the change in temperature and water vapor pressure of the inspired gaswas not considered to be instantaneous but rather a first-order process characterized by a thermal time constant tau. Experimental curves obtained in eight subjects were analyzed by use of parameter estimation techniques. Thevalues of alpha were in agreement with those obtained by conventional plethysmography and tau averaged 63+/-24 ms. The results of additional experiments devised to test the physical meaning of the coefficients and the influence of neglected factors support the validity of the model. It was shown that tau cannot be neglected when breathing air at room temperature.

This study was aimed at determining the haemodynamic effects of various flow resistances in the anaesthetic breathing system in 15 patients under induced hypotension. The breathing pattern, arterial blood gases and haemodynamics were analysed during spontaneous breathing with three systems with different flow resistance as compared with a low-resistance control system. One was made up of a Digby-Leigh valve with an inspiratory resistance of 7 cmH2O l-1s and a high expiratory resistance of 25 cmH2O l-1s (DLS); the other two had an added inspiratory resistive load of 12 cmH2O l-1s (IRS1) and 25 cmH2O l-1s (IRS2) respectively. Whichever system was used, blood gases did not change. With DLS, pulmonary arterial and wedge pressures increased. With the two high inspiratory resistance systems, stroke volume (SV) increased and heart rate (HR) decreased. In six patients, SV was increased only with IRS2, whereas the increase seen with IRS1 in the other nine subjects disappeared with IRS2. It is concluded that the expiratory resistance should be as low as possible in order to avoid pulmonary haemodynamic consequences. An inspiratory resistive load, carefully adapted to each individual case, produced an increase in SV probably by enhancing the venous return. This latter effect could be beneficial in reducing bleeding during middle ear micro-surgery.

The clinical usefulness of lung compliance calculated indirectly was reassessed in a large number of healthy subjects and patients with chronic airflow obstruction or restrictive lung disorders. Indirect compliance was calculated from maximal expiratory flow-volume (MEFV) curve and airway resistance measured plethysmographically according to two approaches. In the first (approach A) all calculations were done at the functional residual capacity, whereas in the second (approach B) they were obtained over the 50-75% volume range of the forced vital capacity; values were compared to those of direct compliance measured concurrently. For the group as a whole, the correlations between indirect and direct values were poor regardless of the approach. Examined separately, the best correlations were found for the healthy group using approach A (r = 0.501) and for the obstructive group using approach B (r = 0.312). Failure to derive a valuable indirect compliance is due to the fact that there is a very poor correlation between upstream resistance and airway resistance measured by body plethysmography.U

Summary. The variability, short-term (1 hour) and long-term (2 weeks) reproducibility of the variables derived from the single-breath N2 test were evaluated in a group of 56 healthy children aged 10 to 16 years with a computerized system. The variability was low for vital capacity and total lung capacity (coefficient of variation less than 3%), moderate for residual volume and phase III N2 slope (9 and 13%) and very high for closing volume (more than 50%). A closing volume could not be identified by the computer algorithm in 18.3% of the trials. The reproducibility of the variables was satisfactory both at 1 hour and at 2 weeks, with the exception of the closing volume, whose increase at 2 weeks seemed to be due to methodological factors. We conclude that reliable results of static lung volumes and phase III N2 slope, but not of closing volume, may be obtained in children by a computerized system in epidemiological studies.

To determine the best procedure for reading maximal expiratory flow-volume curves 2 sets of 5 curves were obtained one hour apart in 89 subjects and processed digitally according to 8 different methods. Four indices were considered: the forced expiratory flows at 25, 50, and 75 per cent of the forced vital capacity, and the maximal mid-expiratory flow. When selecting the curve yielding the largest forced vital capacity or the largest sum of forced vital capacity and forced expiratory volume in 1 sec, flow values were significantly lower (P less than 0.001) and were often less reproducible than those obtained with most of the other methods. Computing the mean of the indices among the curves with the 2 largest forced vital capacities also provided comparatively low values, but with with better reproducibility. In contrast, maximal flows were probably overestimated by using the highest values among the curves having forced vital capacity or a surface area within 5 per cent of the largest, or when reading the indices on a composite curve obtained by superimposing individual breaths at residual volume. More reproducible and, probably, unbiased data may be drawn from the composite curves obtained by superimposing the breaths either at total lung capacity or on the descending limb.

The relationship between diurnal pulmonary arterial pressure (Ppa) measured in steady state and nocturnal level of oxyhaemoglobin saturation (Sao2) measured continuously was studied in fourteen patients with chronic obstructive lung disease. A right heart catheterization was carried out in the morning in each patient. The nocturnal polygraphic study included a continuous recording of transcutaneous Sao2. The behaviour of oxygenation state during sleep was closely linked with the mean level of Sao2 during nocturnal wakefulness. Whatever the nocturnal period (wakefulness, non-rapid-eye-movement sleep, rapid-eye-movement sleep), the mean value of Sao2, which is an integration of variations of the oxygenation state, was more closely linked with diurnal Ppa than a single measure of Sao2 carried out during the catheterization. Ppa seemed independent of the amplitude and frequency of desaturation episodes. In patients with chronic obstructive lung disease, the measurement of mean Sao2 at rest is an easier investigation to carry out during diurnal wakefulness than during nocturnal wakefulness. Thus, this might allow the evaluation of the risk of developing permanent arterial hypertension in chronic obstructive patients.

The purpose of this study was to assess the relationship between the breathing pattern response to CO2 and the severity of mechanical impairment in twenty patients with COLD. The CO2 response was compared to that of a control group of twelve normal subjects. All patients had airway obstruction (FEV1 = 40 +/- 14% of predicted; means +/- SD) and hyperinflation (FRC = 154 +/- 23% of predicted). Tidal volume (VT), inspiratory and total cycle duration (TI, TT), occlusion pressure (P0.1) and endtidal PCO2 were measured at rest and during hyperoxic CO2 rebreathing. On the same day, in all patients, arterial blood gas analysis, spirometric and plethysmographic measurements were made. The slope (S) of the P0.1 response (SP 0.1) to increasing endtidal PCO2 was negatively correlated with airway resistance (r = -0.59; p less than 0.01). Although the flow response, S(VT/TI), was positively and closely correlated with SP 0.1 (r = 0.88; p less than 0.001), it also appeared to be independently influenced by obstruction (p less than 0.01). The tidal volume response, SVT, was principally correlated with inspiratory capacity (r = 0.90; p less than 0.001) and also, independently, with Vmax50 (p less than 0.01). SVT was diminished in seventeen patients, ten of whom only had a decreased S(VT/TI). The shortening in TI during hypercapnia was most marked in patients with the greatest S(P0.1), who did not have arterial hypercapnia at rest. These results suggest: that the poor VT response to CO2 in COLD patients is principally caused by a limitation in inspiratory volume expansion.(ABSTRACT TRUNCATED AT 250 WORDS)

During light slow-wave sleep, ventilation is principally regulated by automatic metabolic control system. An instability in the respiratory control may be the predominant disturbance leading to very irregular or periodic breathing. During deep sleep, ventilation is progressively more stable. During REM sleep, automatic regulation is abolished and ventilation is particularly dependent on the compartmental control system. The reduction in airways and respiratory muscles tone favors the occurrence of obstructive apneas. The elevation in arousal threshold leads prolongation of the obstructive events.