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Biomedical subjects

P H Quanjer

Publications and source records attributed to P H Quanjer.

At least 73 records · Page 4Linked to original sources
PubMed1992

Dust- and endotoxin-related respiratory effects in the animal feed industry.

A cross-sectional study of 315 animal feed workers was undertaken in 14 animal feed mills in the Netherlands. Primary aims were to explore relationships between exposure to organic dust and respiratory symptoms and chronic lung function changes. The study comprised monitoring dust and endotoxin exposure, spirometric lung function measurements (FVC, FEV1, mean midexpiratory flow, and flow-volume parameters) and a questionnaire for respiratory symptoms. The exposure was measured in two periods, during spring and autumn. The average 8-h personal inspirable dust exposure was 9 mg/m3 grain dust (range, 0.2 to 150 mg/m3) and 25 ng/m3 endotoxin (range, 0.2 to 470 ng/m3) based on 530 personal dust measurements. On the basis of these measurements and the occupational history of the workers, the number of years "worked in dust" and an estimate of the cumulative dust and endotoxin exposure were calculated. The prevalence of most chronic respiratory symptoms tended to decrease with increasing years of exposure. The "healthy worker effect" is probably responsible for this finding. In general, a strong negative association between most of the exposure variables and lung function was found. The endotoxin exposure was more strongly related to decreases in lung function than the dust exposure. The estimated effects of an average (cumulative) endotoxin exposure on lung function were greater, with a higher statistical significance, than for an exposure to dust. These results suggest that endotoxin exposure is an important factor in the development of respiratory impairment. The lung function changes occur at endotoxin levels ranging from 0.2 to 470 ng/m3.

Adult↗
PubMed1992

Lung volumes measured by the forced rebreathing technique in children with airways obstruction.

Forced rebreathings may recruit trapped gas into the mixing process. Therefore, we assessed the validity and reproducibility of measurements of residual volume (RVN2) by forced rebreathing in a closed circuit using N2 as indicator gas (N2FR) in children with airways obstruction. Validity was studied from measurements of RV obtained by N2FR, by helium dilution during resting ventilation, and by body plethysmograph at low panting frequency in young patients (8-18 yrs, 13 with asthma, forced expiratory volume in one second (FEV1) 93.0 +/- 22.8% pred; 12 with cystic fibrosis (CF), FEV1 80.4 +/- 16.4% pred). Reproducibility of RVN2 was assessed from duplicate measurements in 73 patients with asthma before and after bronchodilation (FEV1 81.4 +/- 13.7 and 99.6 +/- 11.5% pred, respectively), and in nine patients with CF; the total lung capacity (TLC) was unaffected by bronchodilation; 3,797 +/- 830 ml and 3,807 +/- 843 ml, respectively. Gas dilution methods gave comparable results in all subjects but gave lower values than plethysmography in patients with cystic fibrosis. Reproducibility was satisfactory, median differences between duplicate measurements of RVN2 and TLCN2 varying between 13 and 46 ml, respectively. We conclude that N2FR is quickly performed and well-tolerated. Lung volumes are highly reproducible and agree well with those obtained with the helium dilution method. Deep inspirations do not seem to overcome gas trapping in patients with CF.

Adolescent↗
PubMed1992

Long-term multicentre trial in chronic nonspecific lung disease: methodology and baseline assessment in adult patients. Dutch CNSLD Study Group.

Airways obstruction and airways hyperresponsiveness are two dominant features in patients with chronic nonspecific lung disease (asthma and chronic obstructive pulmonary disease (COPD)). We set up a study to determine whether long-term (3 yrs) therapeutic intervention directed at airways obstruction and hyperresponsiveness is superior to one directed at airways obstruction alone. Patients were selected on functional criteria (age, baseline forced expiratory volume in one second (FEV1), and airways hyperresponsiveness) and, furthermore, extensively characterized by history, smoking habits, allergy, reversibility of airways obstruction and quality of life. The methodology and practical problems of setting up this large multicentre study are outlined, together with an analysis of baseline data. Standardization of methods and techniques and recruitment of patients required much effort, recruitment taking about twice as long as expected. A 3 month feasibility study allowed us to eliminate minor problems in the protocol. Over a 16 month period, 274 adult patients (18-60 yrs) from the out-patient clinics of six university centres entered the study; 99 met the diagnostic criteria for asthma, 51 for COPD, 88 for asthmatic bronchitis, and 36 could not be classified. Their mean (SD) FEV1% pred was 65.1 (15.2)%. Their geometric mean provoking concentration of histamine producing a 20% fall in FEV1 (PC20 histamine) was 0.28 mg.ml-1. In a multiple regression analysis, more severe airways hyperresponsiveness was associated with lower prechallenge FEV1% pred (p less than 0.0001), higher pack-years of smoking (p = 0.0099), blood eosinophil count (p = 0.0004), skin test reactivity (p = 0.0047) and with female sex (p = 0.0302). We conclude that setting up long-term multicentre trials in chronic nonspecific lung disease (CNSLD) is feasible and that these may offer valuable information on treatment and outcome of the disease.

Adult↗
PubMed1992

Changes of nebulizer output over the years.

The effects of long-term use and of cleaning on the output of 30 specimens of DeVilbiss 646 nebulizers were investigated in order to assess their influence on outcome and interpretation of inhalation provocation tests. Output was assessed in a standardized manner based on weight loss on four occasions one year apart. Output was highly reproducible (intraclass correlation greater than or equal to 0.90), and varied considerably between nebulizers, necessitating calibration at least once. Inadequate cleaning diminished nebulizer output by a factor of two (p less than 0.01), while long-term use was associated with a moderate increase in output of 0.28 mg.yr-1 (p less than 0.0001). Bronchial responsiveness can be underestimated by about one doubling dose due to inadequate cleaning, while interchanging nebulizers can lead to overestimation or underestimation by up to one doubling dose. With proper care the increase in output due to wear has no consequences for clinical practice, or for longitudinal studies.

Bronchial Provocation Tests↗
PubMed1991

Pollen deposition in intrathoracic airways.

The pathophysiological mechanisms of pollen-induced asthma have until now remained unclear, because pollen particles have generally been considered too large to penetrate into the lower respiratory tract. Such grains are therefore believed to be unable to induce an immunological response in the lower respiratory tract. There is evidence, however, that a small percentage of large particles (20-30 microns) may penetrate into the peripheral areas of the lung. It also appears that small airborne units of less than 5 microns with the same antigenic activity as pollen, may contribute to inhaled allergen burdens. Pollen asthma probably results from a gradual cumulative effect of deposition of small amounts of allergen in lower airways, and is hence poorly correlated with daily pollen counts.

Air Pollutants↗
PubMed1990

Respiratory system compliance assessed by the multiple occlusion and weighted spirometer method in non-intubated healthy newborns.

In 28 healthy newborn infants (median age 3.5 days), we compared the weighted spirometer (WS) with the multiple occlusion (MO) method for measuring respiratory system compliance (Crs). The MO method was unsuccessful in 8 infants. On average the two methods gave comparable results for compliance (Crs,ws = 40.4 +/- 13.8 and Crs,MO = 45.2 +/- 10.4 mL.kPa-1) in the remaining 20 infants; however, within-individual differences were often considerable, so that the methods did not give interchangeable results. Individual pressure-volume curves almost always intercepted the volume axis below the functional residual capacity with the MO technique, compatible with dynamic elevation of end-expiratory lung volume (EEL) due to inspiratory muscle activity during expiration. A (small) negative volume intercept occurred in less than 50% of curves with the WS method; in these cases it probably reflects alinearity of the compliance curve, an alteration in laryngeal braking or in respiratory muscle control of EEL, or all of these. Both methods provide valuable means for the non-invasive determination of respiratory system compliance in newborn infants, the differences in Crs being small and of minimal physiological significance; however, for individual follow-up they should not be used interchangeably.

Female↗
PubMed1988

Growth of lung and thorax dimensions during the pubertal growth spurt.

In the follow-up study of adolescents residual volume (RV), vital capacity (VC), closing volume (CV), thorax height and thorax width were measured at six month intervals over a six year period; 149 girls and 477 boys, whose ages ranged between 11.5 and 18.5 yr during the follow-up, were investigated. In healthy subjects and in those with respiratory symptoms the rates of change of thoracic dimensions, as calculated by a robust linear regression technique, were moderately well correlated; the growth rates of RV and VC were only slightly correlated, and both were moderately well correlated with changes in thorax dimensions. Thorax height increased relative to thorax width in boys and girls during the follow-up. In boys, thorax height continued to grow, when standing height and thorax width had attained adult values in girls. Thus the thorax attains a more elongated shape. During the adolescent growth spurt the residual volume as a percentage of total lung capacity (RV%TLC) within subjects increased on average 0.6% per yr, and closing volume as a percentage of vital capacity (CV%VC) decreased on average 0.5% per yr. Both of these changes can be accounted for by decreased thorax compliance and increased outward chest recoil at low lung volumes.

Adolescent↗
PubMed1988

Respiratory symptoms and the maximum expiratory flow-volume curve; a multivariate approach.

Information on the size and shape of about 8500 maximum expiratory flow-volume (MEFV) curves was related multivariately to respiratory symptoms to construct a sensitive measure of airflow limitation. The data were obtained in an epidemiological follow-up study of a normal population in The Netherlands. Using non-linear canonical correlation analysis, thirteen variables from each curve yielded two uncorrelated variates which were optimally related to two variates simultaneously derived from all respiratory data. Curves with different size and shape may yield the same probability for respiratory symptoms. In this context the scores of individuals on the scales of the two curve-derived variates do not have to be corrected for body or lung size. Using FEV1 and standing height about half as much of the variability in respiratory symptoms is explained as when using the whole MEFV-curve. Moreover, the distribution of the scores for the MEFV-curves allows the differentiation between three patterns of airflow limitation graphically. These three types suggest different pathophysiological mechanisms related to airways resistance and lung elastic recoil and may be used to characterize individual curves. One type relates to subjects with symptoms of 'asthma', one to airflow limitation as found among people with dyspnoea and elderly subjects and another to bronchitic symptoms. In females, the association of the MEFV-curve with 'asthma' is stronger than in males but much weaker with bronchitic symptoms. Curves found to be more related to 'asthma' or bronchitic symptoms, but not to dyspnoea, are more prevalent among current than among never smokers in males.

Adolescent↗
PubMed1988

Respiratory muscle force and ventilatory function in adolescents.

In 94 girls and 90 boys, aged 12.5-20.3 yr, the relationship of respiratory pressures or forces with lung volumes and ventilatory flows was studied. There was great variability in respiratory muscle performance, which helps to explain differences in lung volumes between individuals. Respiratory muscle force increases almost proportionally with thoracic dimensions, so that inspiratory and expiratory pressures generated at the level of residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC) are approximately constant with age. In the oldest boys there is evidence that the continued increase in lung volumes when they stop growing is due to a 'muscularity effect'. Boys generate larger pressures than girls at all lung volumes. Thus boys attain a larger TLC, and in spite of narrower airways, the same peak expiratory flow and a larger FIV1/FVC ratio than girls. Effort independent flows (FEV1 and MMEF), however, are larger in girls.

Adolescent↗
PubMed1986

Changing relationships between stature and lung volumes during puberty.

In a follow-up study the relationship between growth in body dimensions and in lung volumes during the adolescent growth spurt was studied in 149 girls and 477 boys, aged 11.5-14.0 years at the start of the study. Total lung capacity (TLC), residual volume, vital capacity (VC) and series dead space were measured twice a year for 6 years. When analyzed cross-sectionally lung volumes can be described by a power function of stature, both for each set of half-yearly measurements and when all data are pooled. The powers were close to 3, increasing at each time of measurement in boys and decreasing in girls. These trends reflect that in each subject the growth spurt does not start at the same age, and that individual growth occurs non-linearly along a steeper line than found in the cross-section. Using simple allometric relationships between stature and lung volumes, volume predictions are too high in the youngest age group, and too low in the oldest adolescents. Including age in the regression equation removes this trend in the cross-sectional data, and for VC and TLC also in the longitudinal data.

Adolescent↗
PubMed1985

Effects of halothane on the ventilatory response to hypoxia and hypercapnia in cats.

The influence of halothane 0.8-1.2% inspired on the peripheral hypoxic chemoreflex was investigated in 13 cats subjected to artificial brain stem perfusion (ABP). This technique allows for an independent control of blood gas tensions and halothane concentration between blood perfusing the brain stem (central) and the systemic circulation (peripheral). In six cats the ventilatory response to isocapnic hypoxia was assessed during overall halothane anesthesia (HO) before and during ABP. Before ABP, systemic and brain stem circulations both were rendered hypoxic. During ABP, hypoxia was induced systemically while the brain stem was maintained hyperoxic. The ventilatory response in non-ABP cats (mean 698 ml . min-1 at PaO2 6.6 kPa; 50 mmHg) was about half the response in ABP cats (mean 1,194 ml . min-1 at PaO2 6.5 kPa; 49 mmHg), indicating that in the presence of halothane, central hypoxia depressed ventilation appreciably. Compared with chloralose-urethane anesthesia (CU), halothane reduced the ventilatory response to hypoxia in both perfusion conditions but never abolished it. To assess the influence of halothane on peripheral and central mediation of the CO2 response during hypoxia, each was assessed during CU anesthesia, during HO, and with halothane applied exclusively peripherally against a background of CU (CUHP). In all drug states, the periphery was kept hypoxic and brain stem hyperoxic. Compared with CU anesthesia, HO and CUHP anesthesia reduced both peripheral (Sp) and central (Sc) CO2 sensitivity but not the Sp/Sc ratio. Similarly, the extrapolated PaCO2 at zero ventilation was not detectably different among these three states.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1984

Central respiratory CO2 sensitivity at extreme hypocapnia.

In 7 cats anaesthetized with chloralose-urethane the ponto-medullary region was artificially perfused with blood having PaCO2 values (central PaCO2) in the range of 0.3-4.5 kPa. The ventilatory response to changes in central PaCO2 was measured at constant hypercapnic and hypoxic conditions in the systemic circulation. Ventilation decreased upon lowering the central PaCO2 down to values of 0.5 kPa. There was no threshold for the effect of the central PaCO2 on ventilation. The CO2 sensitivity was undiminished at extreme hypocapnia compared to eucapnia. Under extreme central hypocapnic conditions the breathing pattern became irregular. It is concluded that there is still central CO2 sensitivity related to ventilation at extreme hypocapnia. Our findings suggest that central chemosensitive structures have a neural threshold below a PaCO2 of 0.5 kPa.

Animals↗