Search

Spirometric lung function is partly determined by sex, age and height (Ht). Commonly, lung function is expressed as a percentage of the predicted value (PP) in order to account for these effects. Since the PP method retains sex, age and Ht bias, forced expiratory volume in 1 s (FEV(1)) standardised by powers of Ht and by a new sex-specific lower limit (FEV(1) quotient (FEV(1)Q)) were investigated to determine which method best predicted all-cause mortality in >26,967 patients and normal subjects. On multivariate analysis, FEV(1)Q was the best predictor, with a hazard ratio for the worst decile of 6.9 compared to 4.1 for FEV(1)PP. On univariate analysis, the hazard ratios were 18.8 compared to 6.1, respectively; FEV(1) x Ht(-3) was the next-best predictor of survival. Median survival was calculated for simple cut-off values of FEV(1)Q and FEV(1) x Ht(-3). These survival curves were accurately fitted (r(2) = 1.0) by both FEV(1)Q and FEV(1) x Ht(-3) values expressed polynomially, and so an individual's test result could be used to estimate survival (with sd for median survival of 0.22 and 0.61 yrs, respectively). It is concluded that lung function impairment should be expressed in a new way, here termed the FEV(1)Q, or, alternatively, as FEV(1) x Ht(-3), since these indices best relate spirometric lung function to all-cause mortality and survival.

Conventional measures of bronchial hyperresponsiveness (BHR) are only weakly associated with respiratory symptoms in epidemiological studies. Partial and maximal forced expiratory manoeuvres were recorded during histamine challenge testing in 1,959 young male farmers. Analysis was performed to test whether novel measures of BHR, using alternative flow and time domain indices, are more closely associated with asthma symptoms, smoking status and atopy than forced expiratory volume in one second (FEV1) and conventional measures of BHR. The first moments to 75% and 90% of the forced vital capacity (FVC) were calculated from full (F) and partial (P) forced expiratory manoeuvres (i.e. alpha1 75%F, alpha1 75%P), together with the instantaneous flows when 40% and 30% of the FVC remained to be expired (MEF40 and MEF30). BHR was measured by the provocative dose causing a 20% change (PD20) in the FEV1 and alpha1 75%, and also by the method of log dose slopes (LDS). Asthma was diagnosed from symptoms associated with asthma in 158 (8.1%) of the subjects. PD20 FEV1 could only be recorded in 190 subjects (9.7%), of whom only 48 had asthma, whereas LDSFEV1 was recorded in 1,725 (88%) subjects. From the prechallenge data, alpha1 75%, expressed as standardised residuals, showed the largest difference between smokers with and without asthma symptoms, and no indices showed significant differences between nonsmokers with and without asthma symptoms. From BHR data in both smokers and nonsmokers, LDSFEV1 showed one of the largest differences between those with and without asthma symptoms. With smoking status and atopy accounted for, the greatest partial correlation with asthma diagnosis was found for LDSMEF40P, and then for LDSFEV1, but LDSMEF40P was measurable in only just over one-half of the subjects. The authors conclude that time-domain indices are promising measures for longitudinal epidemiological studies concerning the relationship between bronchial hyperresonsiveness and environmental exposures. However, indices from the partial flow-volume loop suffer from censored data.

Several studies have found an association between the rare Pi-alleles and asthma or bronchial hyperresponsiveness (BHR). This study deals with the effect of Pi-type on BHR among 2,308 young Danish people living in rural areas with a mean +/- SD age of 19.7+/-2.4 yrs. Interviews, pulmonary function testing, bronchial histamine provocation and skin-prick tests were performed. Serum alpha1-antitrypsin levels were determined and phenotyping was performed by means of isoelectric focusing and the subjects categorized into four groups: 1) MM and MX; 2) MS; 3) MZ; and 4) rare, i.e. SZ, SS and ZZ. Among the farmers, a significant positive trend for sensitization towards house dust mites was found, ranging from 12% in the MM group to 22% in the rare Pi-group. A positive test for trend was found within the Pi-groups in a one-sided test for doctor-diagnosed asthma with a peak prevalence of 40% for these symptoms among smokers in the rare Pi-group. On multiple logistic regression analysis, an increased odds ratio (OR) for BHR was found among farming school attendants with the rare Pi-alleles. The OR (95% confidence interval) was 1.71 (0.84-3.49) for MS, 1.93 (1.10-3.39) for MZ and 4.34 (1.19-15.8) for the rare Pi-group. Such a relationship was not found among the conscripts. These results show that a gene/environment interaction may exist between the farming occupation and the rare Pi-alleles, leading to a higher proportion of bronchial hyperresponsiveness related to the rare Pi-alleles in farming school attendants, in contrast to what is found among other young people living in rural areas.

The aim of this study was to assess the cytokine response after nasal exposure to organic dusts. In a double blinded, crossover study five garbage workers with occupational airway symptoms and five healthy garbage workers were intranasally exposed to endotoxin (lipopolysaccharide LPS), beta-1,3-D-glucan (GLU), Aspergillus sp., compost or the saline dilute for 15 min. Nasal cavity volume and nasal lavage (NAL) were performed at baseline and 3, 6, 11 h postexposure. NAL was analysed with differential cell counts, cysteinyl-leukotrienes, tumour necrosis factor alpha, interleukin (IL)-1beta, IL-6 and IL-8. A whole blood assay on cytokine-release was performed with LPS and GLU. NAL cytokines neutrophils, lymphocytes and albumin increased significantly at 6 h after LPS exposure. GLU induced an increase in albumin and a slight increase in IL-1beta 6-11 h post exposure. In the WBA a significant increase in all cytokines after exposure to LPS as well as GLU was found. Significantly more cells were seen in NAL of the control group 6 h post LPS exposure. In conclusion lipopolysaccharide is the most potent inducer of inflammation in the nasal mucosa whereas compost and beta-1,3-D-glucan only induce minor changes. This reaction to lipopolysaccharide is attenuated in workers with occupational airway symptoms. In whole blood assay, however, beta-1,3-D-glucan also induces cytokine release, indicating a different protective effect of the nasal mucosa towards lipopolysaccharide and beta-1,3-D-glucan.

The aim of this study was to assess the prevalence of asthma (self-reported) and relate this to lung function and factors associated with asthma in young farmers. Two hundred and ten female and 1,691 male farming students together with 407 males controls were studied. Each subject underwent a medical interview; forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were recorded using a dry wedge spirometer. Histamine bronchial reactivity was measured using the Yan method. Skin prick testing was performed using inhalant allergens. Nonsmokers had lower prevalence of asthma (5.4-10.8%) than smokers (11.3-21.0%) (p<0.05). Females reported symptoms of asthma nearly twice as often as males. Sex, smoking and a family history of asthma/allergy were significantly associated with asthma. Controls had higher standardized FEV1 and FVC residuals than male students, both nonsmokers (0.21 and 0.24) versus (-0.06 and -0.05) and smokers (0.29 and 0.33) versus (-0.11 and 0.13) (p<0.032). Bronchial hyperresponsiveness, asthma, siblings with allergy and working with cattle (controls only) were significantly associated with reduced lung function. In conclusion, the prevalence of asthma was significantly related to smoking, female sex, family history of asthma and allergy. Whilst bronchial hyperresponsiveness was associated with reduced lung function and lung function was slightly reduced in the male farming students, there was no association found between occupational farming exposure and either lung symptoms or lung function.

The purpose of this study was to examine whether the resistance of the peak flow meter influences its recordings. One hundred and twelve subjects, (healthy nonsmokers and smokers and subjects with lung diseases) performed three or more peak expiratory flow (PEF) manoeuvres through a Fleisch pneumotachograph with and without a mini-Wright peak flow meter added in random order as a resistance in series. The results were as follows. In comparison with a pneumotachograph alone, peak flow measured with an added mini-Wright meter had a smaller within-test variation, defined as the difference between the highest and second highest values of PEF in a series of blows. The mean (SE) variation was 14 (1.3) L.min-1 and 19 (1.5) L.min-1 with and without meter added, respectively. In comparison with the pneumotachograph alone, the addition of the mini-Wright meter caused PEF to be underread, especially at high flows. The difference (PEF with meter minus PEF without meter) = -0.064 (average PEF) -8 L.min-1; R2 = 0.13. The mean difference was -7.8 (1.1) %, and increased numerically for a given PEF, when maximal expiratory flow when 75% forced vital capacity remains to be exhaled (MEF75%FVC) decreased. The reproducibility criteria for repeated measurements of peak flow are more appropriately set at 30 L.min-1 than the commonly used 20 L.min-1, because a within-test variation of less than 30 L.min-1 was achieved in 76% of the subjects without PEF meter inserted and in 88% with meter inserted, with no difference between healthy untrained subjects and patients. The resistance of the peak expiratory flow meter causes less variation in recordings but reduces peak expiratory flow, especially at high values and when the peak is large as compared with the rest of the maximal expiratory flow-volume curve.

Little is known about the response of variable orifice peak flow meters to high frequency flow input. The purpose of this study was to define and test dynamic requirements for such peak flow meters. In a population sample we measured peak expiratory flow (PEF), rise time (tr), from 10-90% PEF and the duration of the flow in excess of 97.5, 95 and 90% of PEF, by use of a carefully calibrated Fleisch pneumotachograph with known and adequate frequency response. Three peak flow meters (Mini Wright, Vitalograph and Ferraris) were tested with an explosive decompression calibrator adjusted to values for PEF and tr as close as possible to the 95th and 5th percentile values, respectively, both for males and females, and with peak durations between 5 and more than 100 ms. The 95th percentile values of PEF were 597 L.min-1 for females and 894 L.min-1 for males. The 5th percentile values of tr were, respectively 55 and 45 ms. The duration of flow in excess of 95% PEF was longer than 10 ms in 99% of the subjects. For all meters, the deviation of PEF corrected for alinearity were less than 5% at a peak duration of 10 ms. We conclude that PEF, rise time, and peak duration can be used for description of dynamic properties of variable orifice meters, and that the tested meters had a satisfactory frequency response for recording PEF in mostly normal subjects.

Little is known about the linearity of portable peak flow meters, or about physical gas factors affecting peak expiratory flow (PEF) readings. We therefore tested five portable peak flow meters of three types in an altitude chamber (sea level to 5,500 m) and in a climate chamber at sea level (7-37 degrees C) to determine the influence of the physical conditions of the gas on the reading of the meters. The nonlinear response of the variable orifice meters was confirmed and, when this was corrected for, the readings of these meters were found to be significantly reduced by higher altitude and lower temperature. The readings from a turbine type of peak flow meter were not affected by altitude but were reduced at low temperature. A mathematical model for the variable orifice meters could correct for both their nonlinear behaviour and the effect of gas density (altitude, temperature and humidity). The model showed that correction is not necessary for the differences in gas conditions between calibration and taking of measurements under normal laboratory conditions. All the meters tested had impedances higher than recommended (0.05 kPa.l-1.s) and this may influence PEF at high flows. The mean uncorrected PEF of six healthy subjects when measured with a Mini Wright peak flow meter at sea level and at 3,000 m fell by 5%, but the mean corrected PEF increased by 12%. This increase in PEF was about 60% of that predicted for fully density-dependent flow and agreed with the findings of other similar studies.(ABSTRACT TRUNCATED AT 250 WORDS)