Determination of forced expiratory volume (FEV 1) and maximal peak expiratory flow within the scope of routine diagnosis in general practice

In 5 Viennese general practice offices we investigated patients by spirometry with the following indications: differential diagnosis of dyspnea; every 3rd smoker of more than 10 cigarettes a day (including asymptomatic ones); cough and nasal disorders of more than 4 weeks duration; indicative physical findings (cyanosis or auscultation). The sample control group was matched for age and gender and did not have any symptoms characteristic of the indication group. Nevertheless a spirometric test was also carried out in these patients. A total of 212 patients were examined in 4673 consultations on 202 workdays in the 5 offices. In the group of 109 patients 62 (56.9%) had dyspnea and/or positive signs on auscultation. Of these 62 patients 39 (62.9%) had 1 or more positive findings either from PEF or FEV 1 or both. There were significantly more referrals for X-rays in case of abnormal lung function. The control group of 103 obviously healthy persons in particular showed a significantly higher number of abnormal PEF values than expected (31 persons, 30.1%).     

Wave speed during maximal expiratory flow and phase velocity from forced oscillations

We review currently known results concerning the estimation of an 'immune' or 'cured' proportion, and testing for the presence of immunes, in censored survival data, suggesting that a firm theoretical foundation now exists for analysis. Two types of estimators, parametric and non-parametric, are discussed and compared with respect to their theoretical properties, and, by simulation, with respect to their small sample behaviour. Both estimators have advantages and drawbacks, but together provide powerful tools for the perceptive analysis of survival data with, or even without, immune individuals.     

Testing bronchial hyper-responsiveness: provocation or peak expiratory flow variability?

BACKGROUND: Assessing bronchial hyper-responsiveness (BHR) is a main diagnostic criterion of asthma. Provocation testing is not readily available in general practice, but peak expiratory flow (PEF) is. Several guidelines promote the use of PEF variability as a diagnostic tool for BHR. This study tested the agreement between histamine challenge testing and PEF variability, and the consequences for diagnosing asthma. AIM: To investigate the possibility of assessing BHR by PEF variability, using a histamine provocation test as a reference. METHOD: Subjects with signs of symptoms indicating asthma (persistent or recurrent respiratory symptoms or signs of reversible bronchial obstruction) (n = 323) were studied. They had been identified in a population screening for asthma. A histamine provocation test and PEF variability were assessed over a three-week period. Asthma was defined as signs or symptoms together with a reversible airflow obstruction or BHR to the histamine challenge test. BHR was defined as a PC20 histamine of < or = 8 mg/ml or a PEF variability of > or = 15%. Overall correlation between PC20 and PEF variability was calculated using Spearman's rho. Furthermore, a decision tree was constructed to clarify the role of BHR in diagnosing asthma. RESULTS: Thirty-two patients had a reversibility in forced expiratory volume in 1 second (FEV1) of > or = 9% predicted, 131 patients showed a PC20 of < or = 8 and 11 patients had a PEF variability of > or = 15%. Overall correlation was poor at only -0.27 (P < 0.0001). One hundred and fourteen of the 131 patients diagnosed as having asthma when the histamine challenge test was used were not diagnosed by PEF variability. CONCLUSION: PEF variability cannot replace bronchial provocation testing in assessing BHR. This indicates that PEF variability and bronchial provocation do not measure the same aspects of BHR. If BHR testing is required in diagnosing asthma, a bronchial provocation test has to be used in general practice as well.     

Intrasubject variability of selected force-platform parameters in the quantification of postural control

Platform stabilometry is increasingly applied to monitor or re-educate standing balance in clinical rehabilitation. Consequently, insight is needed into the validity, reliability, and sensitivity of different force-platform parameters. This study focuses on the intrasubject variability as the major source of variance (unreliability) in the study of human motor skills. The intrasubject variability of several, commonly applied force-platform parameters was determined across ten repeated tests of quiet two-legged standing in healthy subjects to identify the most consistent and stable parameters in the quantification of postural control. The variability of the root mean square (RMS) amplitude, peak-to-peak amplitude, mean frequency, and RMS velocity of the fore-aft and lateral components of the center-of-pressure fluctuations was investigated under varying (visual and cognitive) task conditions. The results indicate that all selected parameters show considerable intrasubject variability irrespective of the task context. Nonetheless, both the RMS amplitude and RMS velocity in either direction of sway do not demonstrate a significant trend across repeated tests. Among the selected parameters, the RMS velocity in the fore-aft direction shows the greatest intrasubject consistency, as well as a high sensitivity to, for example, visual deprivation. These findings support the reliability and validity of this parameter in the clinical quantification of postural control.     

Determination of peak expiratory flow

It is still unknown whether peak expiratory flow (PEF) is determined by "wave speed" flow limitation in the airways. To investigate the influences of airway mechanical properties on PEF, five healthy adults performed maximal forced expiratory effort (MFEE) manoeuvres, in the standard manner and following breathholds at total lung capacity (TLC) of 2 s and 10 s. Oesophageal pressure (Poes) was measured as an index of respiratory effort. Subjects also performed a MFEE following a 10 s breathhold during which intrathoracic pressure was voluntarily raised by a Valsalva manoeuvre, which would increase transmural pressure and cross-sectional area of the extrathoracic airway. Additional MFEEs were performed with the neck fully flexed and extended, to change longitudinal tracheal tension. In separate studies, PEF was measured with a spirometer and with a pneumotachograph. Breathholds at TLC (2 s and 10 s), and neck flexion reduced PEF by a mean of 9.8% (SD 2.9%), 9.6% (SD 1.6%), and 8.7% (SD 2.8%), respectively, when measured with the spirometer. The same pattern of results was seen when measured with the pneumotachograph. These reductions occurred despite similar respiratory effort. Voluntarily raising intrathoracic pressure during a 10 s breathhold did not reverse a fall in PEF. MFEE manoeuvre with neck extension did not result in an increase in PEF, the group mean % changes being -3.0% (SD 5.0%). We conclude that these results do not allow the hypothesis that "wave-speed" (Vws) is reached at PEF to be rejected. A breathhold at TLC could increase airway wall compliance by allowing stress-relaxation of the airway, thus reducing the "Vws" achievable.     

Reproducibility of peak expiratory flow measurements

The ease of PEF measurement and the availability of inexpensive, portable instruments have led to its increasing use. However, relatively little literature exists addressing the testing procedure, optimal frequency, instrument precision, and virtually no epidemiologic literature exists describing the variability of repeated PEF tests within a single test session (reproducibility). A summary of data from one of the authors' own worker population studies is presented which addresses precision of PEF measurement.     

Peak expiratory flow variability, bronchial responsiveness, and susceptibility to ambient air pollution in adults

Bronchial hyperresponsiveness (BHR) and peak expiratory flow (PEF) variability are associated expressions of airway lability, yet probably reflect different underlying pathophysiologic mechanisms. We investigated whether both measures can be used interchangeably to identify subjects who are susceptible to ambient air pollution. Data on BHR (>= 20% fall in FEV1), PEF variability (ampl%mean PEF > 5% on any day during an 8-d period with low air pollution levels) and diary data on upper and lower respiratory symptoms, cough, and phlegm were collected in 189 subjects (48-73 yr). The acute effects (lag0) of particulate matter with a diameter less than 10 micrometers (PM10), black smoke, SO2 and NO2 on the prevalence of symptoms were estimated with logistic regression. In subjects with airway lability, both when expressed as PEF variability (69%) and BHR (28%), the prevalence of symptoms increased significantly with increasing levels of air pollution, especially in those with the greater PEF variability (n = 55, 29%). We found no such consistent positive associations in adults without airway lability. PEF variability, and to a smaller extent BHR, can be used to identify adults who are susceptible to air pollution. Though odds ratios were rather low (ranging from 1.13 to 1.41), the impact on public health can be substantial because it applies to large populations.     

Evaluation of the effect of environmental exposure to tobacco smoke on variability of peak expiratory flow rate in children

A panel study was conducted in autumn (116 children) and repeated in spring (66 children) to test the hypothesis that the individual variability of peak expiratory flow rate (PEFR) depends on the environmental exposure to tobacco smoke (ETS). PEFR was measured twice a day (morning: PEFR-M; evening: PEFR-E), using individual meters at homes, in children exposed (ETS+) and not exposed (ETS-) to tobacco smoke at home. In examined groups the individual variability of PEFR-M was--on average--8.0% (ETS+; autumn), 8.1% (ETS+; spring), 10.5% (ETS-; autumn) and 7.7% (ETS-; spring). The individual variability of PEFR-E was 8.0% (ETS+; autumn), 7.9% (ETS+; spring), 9.5% (ETS-; autumn) and 7.4% (ETS-; spring). The results of multivariate analysis of within- and between-subject variability showed the presence of statistically significant within-subject variability only in ETS+ group (PEFR-M in autumn; PEFR-M and PEFR-E in spring). With all the limitations of a panel study design the findings suggest that environmental exposure to tobacco smoke in children affects the degree of within-subject variability of PEFR in children.     

Peak expiratory flow rate in school-going children

Two members of a unique class of natural antibodies have been identified in all of a large cohort of sera from clinically normal humans of broad age distribution. By means of a series of 10-12 mer peptides the epitope for each of those antibodies was characterized with regard to amino acid identity and conformation. Similar epitope specificity was revealed for the IgM isotopes of cord blood and early post natal sera and for IgM and IgG of adult sera, suggesting that the class of natural antibodies represented by the two identified in this study includes those genomically coded for at their effector level of maturation in the B cells of the neonate. Assay of series of specimens from each of four clinically normal adults revealed that those two natural antibodies are present at relatively constant titer, unique to each individual, over four to five and a half year periods. Those observations imply that the primary function of that class of natural antibodies may be related to maintenance of homeostasis and the molecular identity of each of the two epitopes suggests a role, for each, as monitor or control in intracellular traffic. The previous identification of those epitopes in a conserved protein of HIV also provides support for the proposition that a secondary function of natural antibodies, arising from fortuitous coincidence of the identity of the epitopes, may be that of early defense against infectious invaders.     

Peak expiratory flow in healthy Turkish children

This study was conducted on 1359 healthy, non-smoking Turkish children (727M, 632F) with a mean age of 11.7 +/- 3.4 (6-17) years, in order to determine the normal values of peak expiratory flow (PEF) in Turkish children and to compare various peak-flow meters (PEFMs). PEF values increased with age and height in boys and girls. The relative increase in boys was significantly higher at puberty (p < 0.01). The values of Turkish children were found to be similar to those of Europeans. The results obtained from the three PEFMs were closely correlated.     

Characteristics associated with rapid decline in forced expiratory volume

Though the mechanism of tissue damage induced by colonic inflammation in ulcerative colitis is unknown, it has been established that the inflammatory mediator and potent neutrophil (PMN) chemotaxin, leukotriene B4(LTB4), is present in elevated amounts in the inflamed mucosa. The unique role of 5-lipoxygenase in the production of leukotrienes has made it a target for inhibition. This study used a rat model of acute colonic inflammation induced by a single IP injection of Mitomycin-C to test the efficacy of a specific and potent 5-lipoxygenase inhibitor zileuton in the treatment of colonic inflammation. We hypothesized that after inducing colitis in rats with mitomycin-C, the administration of oral zileuton would inhibit leukotriene production, thus preventing PMN infiltration and subsequent tissue damage. Zileuton decreased colonic tissue damage as measured by Histological score. However, zileuton did not significantly decrease neutrophil infiltration measured by mucosal PMN or myeloperoxidase (MPO) levels. Although zileuton was successful in significantly decreasing the frequency of severe colitis in our model, the fact that the decrease in PMN count and MPO level was not statistically significant suggests that another mechanism may be involved in its anti-inflammatory effect.     

Peak expiratory flow and the resistance of the mini-wright peak flow meter

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.     

Peak expiratory flow rate in Nigerian school children

Peak expiratory flow rate (PEFR) was measured using the Wright's peak flow meter in 263 school boys and 275 school girls living in Lagos, Nigeria. Their ages ranged from 6.0 years to 19.0 years (mean 11.9 +/- 3.8 yrs. for boys and 11.8 +/- 3.9 yrs. for girls). Mean PEFR was 359.2 +/- 102.0 L/min (range 160.0-610.0 L/min) in boys and 327.7 +/- 81.3 L/min (range 160.0-500.0 L/min) in girls. Apart from ages 17, 18 and 19, peak expiratory flow rates were similar in both boys and girls. In both sexes, PEFR correlated positively and significantly with age, height, weight and body surface area. Also in both sexes and in all age groups studied, PEFR was significantly higher than predicted values obtained from previous Nigerian and caucasian prediction equations. When compared with values obtained from a second caucasian prediction equation, observed values were significantly higher in the 6-10 years and 16-19 years age groups in boys and 11-15 years and 16-19 years age groups in girls. New prediction equations for calculating PEFR in Nigerian boys and girls are presented. Observed PEFR may be due to enhanced stature in Nigerian children resulting from improved environment and genetic factors.     

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve

The slope of phase 3 and three noninvasively determined dead space estimates derived from the expiratory carbon dioxide tension (PCO2) versus volume curve, including the Bohr dead space (VD,Bohr), the Fowler dead space (VD,Fowler) and pre-interface expirate (PIE), were investigated in 28 healthy control subjects, 12 asthma and 29 emphysema patients (20 severely obstructed and nine moderately obstructed) with the aim to establish diagnostic value. Because breath volume and frequency are closely related to CO2 elimination, the recording procedures included varying breath volumes in all subjects during self-chosen/natural breathing frequency, and fixed frequencies of 10, 15 and 20 breaths x min(-1) with varying breath volumes only in the healthy controls. From the relationships of the variables with tidal volume (VT), the values at 1 L were estimated to compare the groups. The slopes of phase 3 and VD,Bohr at 1 L VT showed the most significant difference between controls and patients with asthma or emphysema, compared to the other two dead space estimates, and were related to the degree of airways obstruction. Discrimination between no-emphysema (asthma and controls) and emphysema patients was possible on the basis of a plot of intercept and slope of the relationship between VD,Bohr and VT. A combination of both the slope of phase 3 and VD,Bohr of a breath of 1 L was equally discriminating. The influence of fixed frequencies in the controls did not change the results. The conclusion is that Bohr dead space in relation to tidal volume seems to have diagnostic properties separating patients with asthma from patients with emphysema with the same degree of airways obstruction. Equally discriminating was a combination of both phase 3 and Bohr dead space of a breath of 1 L. The different pathophysiological mechanisms in asthma and emphysema leading to airways obstruction are probably responsible for these results.     

Individual variability in the diurnal intraocular pressure curve

BACKGROUND: Reduction of intraocular pressure (IOP) is a primary goal of most glaucoma treatments. However, because the IOP varies during the day, single measurements performed in an ophthalmologist's office do not necessarily provide information on the peak level and fluctuation of the IOP. METHODS: Home tonometry was performed to gain more information on the nature of the diurnal IOP curves and on their variability. One hundred seventy-six patients with open-angle glaucoma (OAG), 55 subjects with ocular hypertension (OHT), and 18 control individuals measured their IOP five times daily at home for 4 to 8 consecutive days using a self-tonometer. RESULTS: Well-defined diurnal IOP variations were observed in all three groups with a predominance of curves with morning or mid-day maxima. Erratic IOP curves without a diurnal rhythm were present in OHT (22%) and OAG (16%) patients but not in control subjects. Differences between the curves of the two eyes of an individual were frequent in OHT (33%) and OAG (36%) patients but not in control subjects (6%). Finally, the majority of OHT (72%) and OAG (66%) patients showed a difference in their diurnal curve patterns on repeat home tonometry performed months apart. CONCLUSION: The authors indicate that it is difficult to rely on one eye as a control for the other. They also indicate that changes in IOP observed in the office at different visits often may be due to a shift in the type of diurnal curve rather than to a true change in the mean IOP. Monitoring of the diurnal IOP may be necessary in some cases if the clinician relies, even partially, on the level of IOP when making a decision on patient management.     

Density dependence of expiratory flow and bronchodilator response in asthma

Change in the magnitude of density dependence of the maximal expiratory flow (D/MEF) following inhalation of isoproterenol was used as a test for predicting the long term response to isoproterenol vs atropine in 24 adult patients with longstanding asthma. Eleven subjects showed a decrease in D/MEF manifested by increase in volume of isoflow (VisoV) and/or decrease in Vmax50 Helox/air following isoproterenol inhalation (group 1). Thirteen subjects manifested an opposite response (group 2). Atropine sulphate (0.08 mg/kg) and isoproterenol hydrochloride (2.5 mg) were then administered by inhalation, each four times a day for seven days in a randomized double-blind cross over fashion to all subjects. One of group 1 but ten of group 2 subjects had a greater subjective and objective improvement with atropine than with isoproterenol (P less than .005). An increase in D/MEF following isoproterenol can be used as a test to predict a better response to atropine than to isoproterenol over a one week period. Such a response occurs in almost half of the adult chronic asthmatic patients. The results are consistent with a preferential dilatation of the large airways by atropine.     

Quantitative versus qualitative analysis of peak expiratory flow in occupational asthma

BACKGROUND: Peak expiratory flow rates (PEF) are often used to confirm the diagnosis of occupational asthma. The records are usually analysed qualitatively, and this may lead to interobserver disagreement. In this study the diagnostic value of a qualitative assessment of change in PEF was compared with objective measures of change in PEF and the results of a specific inhalation challenge test with plicatic acid. METHODS: Twenty five patients with possible red cedar asthma recorded PEF six times a day for three weeks at work and for two weeks away from work and underwent a challenge test with plicatic acid at the end of the recording period. Patients were considered to have cedar asthma if the FEV1 after inhalation of plicatic acid was 15% or more below that on the control day. PEF was plotted against time and assessed qualitatively by three physicians. The graph was considered positive for cedar asthma if two of the three physicians agreed that PEF was lower at work than away from work. The 95% confidence interval for variation in PEF between periods at work and away from work was also obtained from 15 asthmatic patients without occupational asthma. Differences in PEF between periods at work and away from work were considered positive for occupational asthma in the patients exposed to cedar when they were outside the 95% confidence interval for variations in PEF in the 15 patients whose asthma was nonoccupational. RESULTS: Of the 25 men studied, 15 had a positive response to plicatic acid. The qualitative PEF analysis had a sensitivity of 87% and a specificity of 90% in confirming red cedar asthma as diagnosed by the specific challenge test. Among the objective methods tested, only the difference in mean PEF between the maximum PEF at weekends and the minimum PEF on working days had a sensitivity (93%) greater than that of the qualitative method and a similar specificity. CONCLUSIONS: The qualitative assessment of PEF is a good diagnostic test for cedar asthma. Only one objective method of PEF analysis proved to be slightly more sensitive than the qualitative method and similar in specificity.     

Relationship of daytime asthma symptom frequency to morning peak expiratory flow

This study examined appraisal of self and others, as measured by semantic differential ratings of Police, State, Society, Family, Friend, Myself as a Man/Woman, and Myself as a Political Person, in 55 tortured political activists in Turkey, 55 nontortured political activists, and 55 nontortured, politically noninvolved controls. There were no remarkable differences between tortured and nontortured political activists; both groups differed from controls in having a more negative appraisal of the police and the state and stronger perceptions of danger, mistrust, and injustice in relation to state authority. Lack of beliefs concerning a "benevolent state" may have protected the survivors from the traumatic effects of state-perpetrated torture. Further research into the possible protective role of belief systems in posttraumatic stress disorder is needed.     

Management of asthma based on their peak expiratory flow rate monitoring

SCN1B, the human gene encoding the beta1-subunit of the voltage-gated sodium channel has previously been cloned and mapped to Chr 19q13.1. The sequence of the homologous mouse gene, Scn1b, has now been determined from cDNA. The mouse gene is highly conserved, encoding a predicted protein with 99%, 98% and 96% amino acid identity to the rat, rabbit, and human homologs, respectively. DNA sequence conservation is also striking in the 3' untranslated region which shows 67% and 98% to human and rat, respectively. Unlike the human and rat homologs, high expression of mRNA from the mouse gene is confined to adult skeletal muscle and brain, and is not observed in heart. As Scnlb maps to Chr 7, in close genetic proximity to the quivering gene (qv), the coding region of Scnlb was also cloned from a qvJ/qvJ homozygous mouse and assessed as a candidate for the site of this genetic defect. Comparison of qv and wild-type cDNAs showed no changes in the predicted amino acid sequence that could cause the qv phenotype. However, three silent polymorphisms in the DNA coding region indicate that Scn1b is close to qv, and is within a region of genetic identity with DBA/2J, the inbred background on which the qvJ allele arose.