Sensitivity of spirometric measurements to detect airway obstruction in infants

We evaluated the ability of forced expiratory flow volume curves from raised lung volumes to assess airway function among infants with differing severities of respiratory symptoms. Group 1 (n = 33) had previous respiratory symptoms but were currently asymptomatic; group 2 (n = 36) was symptomatic at the time of evaluation. As a control group, we used our previously published sample of 155 healthy infants. Flow volume curves were quantified by FVC, FEF50, FEF75, FEF25-75, FEV0.5, and FEV0.5/FVC, which were expressed as Z scores. All variables except FVC had Z scores that were significantly less than zero and distinguished groups 1 and 2 with progressively lower Z scores. The mean Z scores of the flow variables (FEF50%, FEF75%, and FEF25-75%) were more negative than the Z scores for the timed expired volumes (FEV0.5 or FEV0.5/FVC) for both groups. In general, measures of flow identified a greater number of infants with abnormal lung function than measures of timed volume; FEF50 had the highest performance in detecting abnormal lung function. In summary, forced expiratory maneuvers obtained by the raised volume rapid compression technique can discriminate among groups of infants with differing severity of respiratory symptoms, and measures of forced expiratory flows were better than timed expiratory volume in detecting abnormal airway function.     

A comparison of a new transtelephonic portable spirometer with a laboratory spirometer.

The Spirophone is a new, portable transtelephonic spirometer which records the slow and the forced expiratory vital capacity tests. Data can be transmitted via the telephone to a remote receiving centre, where a volume-time curve and the flow-volume curve are displayed on screen in real time. The aim of this study was to compare the newly developed transtelephonic spirometer, with a laboratory spirometer according to the American Thoracic Society (ATS) testing guidelines. Spirometry indices (slow vital capacity (SVC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), forced expiratory flow at 25, 50 and 75% of FVC (FEF25, FEF50, and FEF75, respectively)) were measured from the SVC and the FVC tests in 45 subjects (30 patients, 15 healthy volunteers) according to the ATS standards. The data obtained with the laboratory system were compared to those from the Spirophone. The Spirophone measurements of SVC, FVC, FEV1, PEF, FEF25, FEF50 and FEF75 correlated closely (r=0.91-0.98) to those from the laboratory system, whereas FEF25, FEF50, and FEF75 were significantly higher with the Spirophone. It is concluded that the Spirophone is comparable to the standard spirometry for home monitoring of slow vital capacity, forced vital capacity, forced expiratory volume in one second and peak expiratory flow. The validity of the manoeuvre can be assessed on screen in real time.     

Ratio between forced expiratory flow between 25% and 75% of vital capacity and FVC is a determinant of airway reactivity and sensitivity to methacholine

STUDY OBJECTIVE: The ratio between forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) and FVC is thought to reflect dysanapsis between airway size and lung size. A low FEF(25-75)/FVC ratio is associated with airway responsiveness to methacholine in middle-aged and older men. The current study was designed to assess this relationship in both male and female subjects over a broader range of ages. STUDY DESIGN: Data analysis of consecutive subjects who had a >or= 20% reduction in FEV(1) after 相似文献   

Discriminating measures and normal values for expiratory obstruction

OBJECTIVES: To develop mean and 95% confidence limits for the lower limit of normal (LLN) values for forced expiratory volume in 3 s (FEV3)/FVC ratio for Latin, black, and white adults; to ascertain comparative variability of the FEV1/FVC ratio, the FEV3/FVC ratio, and forced expiratory flow, midexpiratory phase (FEF(25-75)) in never-smoking adults; to evaluate their utility in measuring the effect of smoking on airflow limitation; and to develop and use the fraction of the FVC that had not been expired during the first 3 s of the FVC (1 - FEV3/FVC) to identify the growing fraction of long-time-constant lung units. DESIGN: Analysis of the Third National Health and Nutrition Examination Survey (NHANES III) database of never-smokers and current smokers. PARTICIPANTS: A total of 5,938 adult never-smokers and 3,570 current smokers from NHANES III with spirometric data meeting American Thoracic Society standards. MEASUREMENTS AND RESULTS: After establishing new databases for never-smokers and current smokers, we quantified the mean and LLN values of FEV3/FVC in never-smokers, and identified spirometric abnormalities in current smokers. When associated with older age, FEV3/FVC decreases and 1 - FEV3/FVC increases as FEV1/FVC decreases. On average, using these measurements, the condition of current smokers worsened about 20 years faster than that of never-smokers by middle age. If < 80% of the mean predicted FEF(25-75) was used to identify abnormality, over one quarter of all never-smokers would have been falsely identified as being abnormal. Using 95% confidence limits, 42% of 683 smokers with reduced FEV1/FVC and/or FEV3/FVC would have been judged as normal by FEF(25-75). CONCLUSIONS: FEV1/FVC, FEV3/FVC, and 1 - FEV3/FVC characterize expiratory obstruction well. In contrast, FEF(25-75) measurements can be misleading and can cause an unacceptably large number of probable false-negative results and probable false-positive results.     

Spirometric reference values for the 6-s FVC maneuver

STUDY OBJECTIVES: The guidelines of the National Lung Health Education Program for COPD screening proposed a shorter FVC maneuver (forced expiratory volume at 6 s of exhalation [FEV(6)]). Although reference values for FEV(6) are available from the third National Health and Nutrition Examination Survey, forced expiratory flow between 25% and 75% of FVC (FEF(25-75%)) reference values for the shorter 6-s maneuver are not available and are needed. In particular, calculation of largest observed volume during the first 6 s of an FVC maneuver (FVC(6)), from a shortened FVC maneuver, is necessary because the FEF(25-75%) measurement is based on a percentage of FVC or, for a shorter maneuver, FVC(6). DESIGN: We reanalyzed the raw volume-time curves from the third National Health and Nutrition Examination Survey to calculate FVC(6), forced expiratory volume at 0.5 s of exhalation, forced expiratory volume at 3 s of exhalation, ratio of the FEV(1) to largest observed volume during the first 6 s of an FVC maneuver expressed as a percentage (FEV(1)/FEV(6)%), and forced expiratory flow between 25% and 75% of the largest observed volume during the first 6 s of an FVC maneuver (FEF(25-75%6)) in addition to the previously reported values for FEV(1), FEV(6), and FEV(1)/FEV(6)%. PATIENTS OR PARTICIPANTS: Using the same normal, asymptomatic, nonsmoking reference population from a previous study, reference values for these parameters were derived from best values. RESULTS: A total of 2,261 white, 2,564 African-American, and 2,666 Mexican-American subjects aged 8 to 80 years were included in the analysis. Fifty-four subjects from the previous study were not included due to missing raw volume-time curves. CONCLUSIONS: These reference values, utilizing the FVC(6), provide investigators with the means of evaluating the relative merits of using the shorter FVC maneuver as a surrogate for the traditional FVC. They are needed particularly for calculating FEF(25-75%), as statistically significant differences were observed between the FEF(25-75%) and FEF(25-75%6).     

Pulmonary function characteristics in patients with different patterns of methacholine airway hyperresponsiveness

STUDY OBJECTIVES: The American Thoracic Society guidelines for methacholine-induced airway hyperresponsiveness include a > or = 20% reduction in FEV(1) or a > or = 40% reduction in specific airway conductance (sGaw). The objectives of the current study are to assess the concordance between these two criteria and to characterize the pulmonary function and respiratory symptoms of patients with different patterns of methacholine hyperresponsiveness. STUDY DESIGN: A prospective study of 248 consecutive patients referred for methacholine bronchoprovocation testing. RESULTS: Positive methacholine hyperresponsiveness was noted in 179 patients; 139 patients (78%) had a > or = 20% reduction in FEV(1), whereas 40 patients (22%) had a > or = 40% reduction in sGaw alone without a significant change in FEV(1). The former group had the following: (1) higher baseline lung volumes, (2) lower baseline values of FEV(1) and sGaw, (3) forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75))/FVC ratios compared to patients with a reduction in sGaw alone (0.72 +/- 0.26 vs 0.97 +/- 0.28, mean +/- SD; p < 0.0001), and (4) more frequent presence of wheezing and chest tightness (p < 0.05). CONCLUSIONS: First, a substantial number of patients have a reduction in SGaw alone in response to methacholine, and secondly, this response is seen in patients with a higher FEF(25-75)/FVC ratio. Since the FEF(25-75)/FVC ratio is thought to be an index of airway size relative to lung size, we speculate that the larger intrinsic airway size relative to lung size may explain the differences in baseline parameters and patterns of methacholine hyperresponsiveness.     

Genome-wide linkage of forced mid-expiratory flow in chronic obstructive pulmonary disease

Familial aggregation of forced expiratory flow during the middle half of the FVC (FEF(25-75%)) and FEF(25-75%)/FVC has been observed in the Boston Early-Onset Chronic Obstructive Pulmonary Disease Study, but linkage results have not been reported for these phenotypes. An autosomal whole genome-wide linkage scan was performed in 72 pedigrees ascertained through a proband with severe, early-onset chronic obstructive pulmonary disease, and linkage analyses of FEF(25-75%) and FEF(25-75%)/FVC were performed using Sequential Oligogenic Linkage Analysis Routines. There was suggestive evidence for linkage of FEF(25-75%)/FVC with chromosome 2 (LOD 2.60 at 216 cM). In a smokers-only analysis, evidence for linkage was observed for postbronchodilator FEF(25-75%) with chromosome 12 (LOD 5.03 at 35 cM) and chromosomes 2 and 12 for FEF(25-75%)/FVC (LOD 4.12 at 221 cM and LOD 3.46 at 35 cM, respectively); in the smokers-only model, evidence for linkage also was robust for FEV(1)/FVC on chromosome 2 (LOD 4.13 at 229 cM) and FEV(1) on chromosome 12 (LOD 3.26 at 36 cM). Our analyses provide evidence for linkage of FEF(25-75%) and FEF(25-75%)/FVC on chromosomes 2q and 12p. LOD scores of greater than two were also observed for chromosomes 16, 20, and 22 with the smokers-only analysis, which may suggest gene-by-smoking interactions in these regions.     

Measurement of reversibility of airways obstruction: which parameters to use?

Maximum expiratory flow-volume (MEFV) curves recorded before and after salbutamol inhalation on 100 patients with various lung diseases were studied. Improvement was found to occur more frequently in MEF50, FEF25-75, FVC and MEF25, than in FEV1, FEV1/FVC%, or MTT. If improvement in only one of the first four parameters was taken as a measure of reversibility of airways obstruction, many cases showing improvement in the others were missed. Improvement in any of the last three parameters was rarely missed if improvement in any of the first four was present. It was concluded that there is no single best measurement for assessment of bronchodilator response. FVC, FEF25-75, MEF50 and MEF25 should all be measured. A flow-volume record of forced expiration from which all these measurements can be derived would therefore be preferable for this purpose to the time-volume spirometer record from which only FVC and FEF25-75 can be determined.     

Forced expiratory parameters in healthy preschool children (3-6 years of age)

In a group of 173 healthy preschool children 3-6 years of age (body height, 90-130 cm; 102 boys and 71 girls) out of total 279 children examined, maximum expiratory flow-volume (MEFV) curves were recorded in cross-sectional measurements. The majority (62%) of preschool children were able to generate an MEFV curve as correctly as older children. From the curves, maximum expiratory flows at 25%, 50%, and 75 % of vital capacity (MEF(25), MEF(50), and MEF(75)), peak expiratory flow (PEF), forced expiratory volume in 1 sec (FEV(1)), forced vital capacity (FVC), and area delineated by MEFV curve (A(ex)) were obtained. The purpose of the study was to establish reference values of forced expiratory parameters in preschool children suitable for assessment of lung function abnormalities in respiratory preschool children. The values of the studied parameters increased nonlinearly and correlated significantly with body height (P < 0.0001); the correlation was much lower with age. A simple power regression equation was calculated for the relationship between each parameter and body height. A best-fit regression equation relating functional parameters and body height was a power function. Based on the obtained regression equations with upper and lower limits, we prepared tables listing reference values of forced expiratory parameters in healthy Caucasian preschool children, against which patients can be compared. No statistically significant gender differences were observed for MEF(25), MEF(50), MEF(75), PEF, FEV(1), FVC, and A(ex) by extrapolation. The reference values were close to those obtained in our older children. A decline of the ratios PEF/FVC, FEV(1)/FVC and MEF/FVC with increasing body height suggested more patent airways in younger and smaller preschool children.     

Airway hyperreactivity in subjects with tetraplegia is associated with reduced baseline airway caliber

OBJECTIVES: We administered aerosolized histamine to 32 subjects with tetraplegia to determine whether there were differences in spirometric and/or lung volume parameters between responders and nonresponders. RESULTS: Baseline pulmonary function parameters revealed mild to moderate restrictive dysfunction. We found that 25 subjects (78%) were hyperreactive to histamine (mean provocative concentration of a substance causing a 20% fall in FEV(1) [PC(20)], 1.77 mg/mL). Responders (PC(20), < 8 mg/mL) had significantly lower values for forced expiratory flow between 25% and 75% of the outflow curve (FEF(25-75)), FEF(25-75) percent predicted, and FEF(25-75)/FVC ratio. Among all 32 subjects, the natural logarithmic transformation performed on PC(20) values (lnPC(20)) correlated with FEF(25-75) percent predicted, FEV(1) percent predicted, and FEF(25-75)/FVC ratio but not with FVC percent predicted. Responders with PC(20) values < 2 mg/mL (n = 13) had significantly reduced values for FVC, FVC percent predicted, FEV(1), and FEV(1) percent predicted compared to those with PC(20) values between 2 mg/mL and 8 mg/mL. In addition, among responders, there was a significant correlation between lnPC(20) and FVC percent predicted. A significant relationship was found between maximal inspiratory pressure (PImax) and both FEV(1) percent predicted and FEF(25-75) percent predicted, but not between lnPC(20) and either PImax or maximal expiratory pressure (PEmax). CONCLUSIONS: These findings demonstrate that subjects with tetraplegia who exhibit airway hyperreactivity (AHR) have reduced baseline airway caliber and that lower values for lnPC(20) are associated with parallel reductions in surrogate spirometric indexes of airway size (FEV(1) percent predicted and FEF(25-75) percent predicted) and airway size relative to lung size (FEF(25-75)/FVC ratio). The absence of an association between lnPC(20) and FVC percent predicted for the entire group or between lnPC(20) and either PImax or PEmax indicates that reduced lung volumes secondary to respiratory muscle weakness cannot explain the mechanism(s) underlying AHR. Among responders, however, a possible role for reduction in lung volume, as it pertains to increasing AHR, cannot be excluded. Proposed mechanisms for reduced baseline airway caliber relative to lung size in subjects with tetraplegia include unopposed parasympathetic activity secondary to the loss of sympathetic innervation to the lungs and/or the inability to stretch airway smooth muscle with deep inhalation.     

Body composition analysis and changes in airways function in obese adults after hypocaloric diet

STUDY OBJECTIVES: To determine the relationship between weight-loss and pulmonary function indexes, focusing on forced expiratory flows (ie, FEV(1), forced expiratory flow at 50% of vital capacity [FEF(50)], forced expiratory flow at 75% of vital capacity, and forced expiratory flow at 25 to 75% of vital capacity [FEF(25--75)]). Specifically, to determine the effect of losses in total and segmental fat mass (FM) and of modifications in lean body mass, after restricted hypocaloric diet, on pulmonary function among obese adults. DESIGN: Cross-sectional, observational. SETTINGS: Human Physiology Division, Faculty of Medicine and Surgery, "Tor Vergata" University, Rome, Italy. PATIENTS: Thirty obese adults (mean [+/- SD] baseline body mass index [BMI], 32.25 +/- 3.99 kg/m(2)), without significant obstructive airway disease, were selected from among participants in a weight-loss program. MEASUREMENTS AND RESULTS: Anthropometric, body composition (BC), and respiratory parameters of all participants were measured before and after weight loss. Total and segmental lean body and FM were obtained by dual-energy x-ray absorptiometry. Dynamic spirometric tests and maximum voluntary ventilation (MVV) were performed. The BC parameters (ie, body weight [BW], BMI, the sum skinfold thicknesses, thoracic inhalation circumference, thoracic expiration circumference, total FM, and trunk FM [FMtrunk]) were significantly decreased (p < or = .0001) after a hypocaloric diet. The mean vital capacity, FEV(1), FEF(50), FEF(25-75), expiratory reserve volume, and MVV significantly increased (p < or = 0.05) with weight loss. The correlation coefficient for Delta FEF(25--75) (r = 0.20) was numerically higher than Delta FEF(50) and Delta FEV(1) (r = 0.14 and r = 0.08, respectively) for the BW loss. Moreover, the correlation coefficient for Delta FEF(25--75) (r = 0.45) was significantly higher (p < or = 0.02) than those for Delta FEF(50) and Delta FEV(1) (r = 0.38 and r = 0.15, respectively) for FMtrunk loss. CONCLUSIONS: This study shows that a decrease in total and upper body fat obtained by restricted diet was not accompanied by a decrease in ventilatory muscle mass. FMtrunk loss was found to have improved airflow limitation, which can be correlated to peripheral airways function.     

Role of forced expiratory flow at 25-75% as an early marker of small airways impairment in subjects with allergic rhinitis.

A close link exists between allergic rhinitis and asthma. Small airway disease (SAD), defined by a reduction in forced expiratory flow at 25-75% of the pulmonary volume (FEF25-75) and normal spirometry (normal forced expiratory volume at 1 second [FEV1], forced vital capacity [FVC], and FEV1/FVC ratio), may be a marker for early allergic or inflammatory involvement of the small airways in subjects with allergic diseases and no asthma. The aim of this study was to determine if there is a relationship between SAD, the outcome variable, and several allergic predictors in patients without asthma but with allergic rhinitis. A cross-sectional study was performed. Two hundred eleven midshipmen attending the third and fifth course of the Navy Academy of Livorno were screened. Fifty-eight midshipmen showed slight spirometric anomalies. Thus, they were referred to the Navy Hospital of La Spezia for standardized tests: skin-prick test, nasal cytology, spirometry, and methacholine bronchial challenge. A reduced FEF(25-75) was arbitrarily defined as < 80% of predicted. All 58 subjects had a normal FEV1, FVC, and FEV1/FVC ratio. Twenty subjects had a reduced FEF(25-75), consistent with the definition of SAD. A mean value of FEF(25-75) of 70.3 (SD, 8.5) was measured in patients with a reduced FEF, and it was 108.0 (SD, 14.3) in patients with preserved FEF(25-75). All the candidate allergic predictors appeared to be strongly associated with a reduced FEF(25-75). The proportion of subjects with reduced FEF(25-75) appeared to increase with increasing severity of the allergic predictors, and, correspondingly, the mean value of FEF(25-75) appeared to decrease. This study provides evidence that there is a relationship between SAD and allergic parameters such as nasal symptoms and eosinophils.     

Correlation between inhalant allergen-specific IgE and pulmonary function in children with asthma

Sensitization to aeroallergens is associated with diminished lung function in adults. Little has been studied on the relationship between the inhalant allergen-specific IgE and pulmonary function in asthmatic children. This study was focused on four major inhalant allergens found in Korea, including Dermatophagoides pteronyssinus (Der p.), Dermatophagoides farinae (Der f.), and Alternaria- and German cockroach-specific IgEs, with evaluation of pulmonary function in relation to the amount of allergens. The parents or legal guardians of participants enrolled in this study gave informed consent. Fifty-five asthmatic patients and 48 nonasthmatic children were included. The amounts of specific IgE for the four specified inhalant allergens were determined by employing the CAP system FEIA. Forced expiratory volume in 1 sec (FEV(1))/forced vital capacity (FVC), FEV(1), and forced expiratory flow between 25% and 75% of FVC (FEF(25-75)) of subjects were evaluated through pulmonary function tests. In the asthmatic group, FEV(1), FEV(1)/FVC, and FEF(25-75) were significantly reduced (P < 0.05): reduction in FEV(1) (r = -0.44) and FEF(25-75) (r = -0.33) in association with the Der f.-specific allergen, and reduction in FEV(1) (r = -0.37) and FEF(25-75) (r = -0.34) in association with the Der p.-specific allergen, were observed. However, there was no significant correlation with German cockroach and Alternaria allergen. In the control group, no significant correlation was detectable between the allergen-specific IgE titers and the results of pulmonary function tests. In asthmatic patients, Der p.- and Der f.-specific IgEs, and not German cockroach and Alternaria, seem to play a considerable role in reduced pulmonary function among asthmatic children.     

Adult-type pulmonary function tests in infants without respiratory disease

A new method that permits the measurement of adult-type maximal expiratory flow-volume curves and fractional lung volumes in sedated infants was recently described. The purpose of this study was to define the normal range for these new measures of pulmonary function in infants and young children. Measurements of forced expiratory flows and fractional lung volume were made on 35 occasions in 22 children (ages 3-120 weeks) without respiratory disease. Maximal expiratory flow-volume curves were measured by the raised lung volume, thoracoabdominal compression technique. Functional residual capacity (FRC) was measured plethysmographically. Measurements of total lung capacity (TLC), residual volume (RV), FRC, forced vital capacity (FVC), and forced expiratory flows at 25, 50, 75, 85, and between 25% and 75% of expired FVC (FEF(25), FEF(50), FEF(75), FEF(85), and FEF(25-75), respectively) all increased in relation to infant length (P<0.001). RV/TLC, FRC/TLC, and FEF(25-75)/FVC declined in relation to increasing length (P<0.001). The forced expiratory flow and fractional lung volume measurements using this method were similar to previously reported estimates using other methods. These estimates represent a reasonable reference standard for infants and young children with respiratory problems.     

老年过敏性鼻炎患者肺功能研究

目的探讨老年常年性过敏性鼻炎患者肺功能的变化。方法检测30例过敏性鼻炎（老年前期及老年期患者）及30例健康对照者的肺功能,包括第1秒用力呼气容积（FEV1）、用力肺活量（FVC）、用力呼气中期流速（FEF25-75）、最大呼气流量（PEF）。结果老年过敏性鼻炎组的FEV1、FVC、FEF25-75、PEF均减少,与健康对照组比较差异有统计学意义（P〈0.01）。结论本研究提示上下气道的密切相关性,老年过敏性鼻炎患者肺功能有明显改变。     

Comparison of normal infants and infants with cystic fibrosis using forced expiratory flows breathing air and heliox

SUMMARY. The detection of early airway disease in infants with cystic fibrosis (CF) may lead to earlier intervention and an improved prognosis. We hypothesized that the ratio of maximal expiratory flows while breathing a mixture of helium and oxygen (heliox) and air, referred to as density dependence (DD), would identify early airway disease in infants with CF who have normal lung function. We also hypothesized that these infants with CF might be better differentiated from normal infants when the flows breathing heliox are compared instead of room air flows. We evaluated 10 infants with CF and 21 infants without CF and with normal lung function, defined as a forced vital capacity (FVC) and forced expiratory flows between 25-75% of expired volume (FEF(25-75)) of greater than 70% predicted (z-score > -2.0). Full forced expiratory maneuvers by the rapid thoracic compression technique were obtained while breathing room air and then heliox. Flow at 50% and 75% of expired volume (FEF(50), FEF(75)), FEF(25-75), and FVC were calculated from the flow volume curve with patients and control subjects breathing each gas mixture. The ratio of heliox to air flow at FEF(50) and FEF(75) was calculated (DD(50), DD(75)), and the point where the two flow-volume curves crossed (V(iso) V') was also measured. DD parameters did not distinguish the infants with CF from the infants without CF; length-adjusted FEF(50) breathing air was significantly lower in the infants with CF compared to the infants without CF (P < 0.05). Length-adjusted flows breathing heliox did not distinguish the two groups. We conclude that the lower FEF(50) value may reflect early airway obstruction in healthy infants with CF, and that measurements obtained with the less dense gas mixture did not improve detection of airway disease in this age group.     

Airway hyperreactivity detected by methacholine challenge in children with sickle cell disease

Recent studies have emphasized the presence of airway hyperreactivity (AHR) in children with sickle cell disease (SCD). However, various tests for the detection of AHR have yielded distinctly different results in these patients. This study identified AHR via a methacholine challenge test (MCT) in a group of children with SCD (31 patients; age range, 6-16 years). The results of pulmonary function tests (PFTs) in patients with SCD and age-matched controls (30 healthy children) were investigated and compared. A positive methacholine challenge result was noted in 25 patients (77.5%). We found that when compared with controls, the children with SCD had lower forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV(1)) and that both their forced expiratory flow at 25-75% of the FVC (FEF(25-75)) and their FEV(1)/FVC ratio were not statistically significantly different from those of the controls. The statistically significant differences remained after treatment with a bronchodilator agent, but the changes in the FVC, FEV(1), and FEF(25-75) in response to bronchodilator treatment did not differ with statistical significance between the two groups. There was a negative correlation between the number of ACS attacks and the percent predicted of the FEV(1) and the FEV(1)/FVC ratio. We found that the MCT reveals a high incidence of AHR in patients with SCD, regardless of whether those individuals have ACS.     

Predicting arterial oxygen tension from maximum expiratory flow volume curves in cystic fibrosis

Measurements of arterial oxygen tension (PaO2) while breathing room air, and maximum expiratory flow volume curves were performed in 34 patients with cystic fibrosis (age range 7-27 years, 24 males and 10 females). Logistic regression was performed using forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEFR), and forced expiratory flow at 75% of expired vital capacity (FEF75) to model an equation for predicting when PaO2 would be less than 55 mmHg (severe hypoxemia). Equations were modelled using one, two, three, or all four of the variables. For the univariate logistic regression, each of the four variables was a significant (P less than 0.001) predictor for severe hypoxemia. FVC was the best predictor with an R2 = 0.56, sensitivity of 100% (false negative rate = 0%), and a specificity of 88.5% (false positive rate = 27%). The model predicted that patients with an FVC less than 35% of the predicted normal were at risk of having PaO2 less than or equal to 55 mmHg. Adding FEV1, FEF75, or PEFR in various combinations to FVC made the model equation more complicated but did not add significantly to the ability to predict severe hypoxemia.     

Assessment of mid flow rate measurements in patients undergoing methacholine challenge.

The objective of this study is to assess the FEF(25-75) and FEF(25-75)/FVC in relation to the FEV1 in patients who have had a methacholine inhalation challenge study for a variety of clinical indications. The study is a retrospective review of methacholine challenge results at the university medical center. One hundred twenty-one consecutive patients who had a methacholine challenge performed for clinical indications were included in the study with no intervention. Methacholine was administered in successively increasing twofold concentrations in doses from 0.62 mg to a final concentration of 10 mg. A 20% drop in FEV1 compared to the prechallenge value was considered a positive test. We considered > or = 25% decrease in FEF(25-75) as a significant change. The > or = 25% decrease in FEF(25-75) occurred sooner than the 20% drop in FEV1 with a positive response occurring at least one full dose sooner in 23 of the 55 subjects. Thirty two subjects reacted at the same dose. The dose at which the FEF(25-75) decreased by > or = 25% was significantly different from the corresponding dose causing a 20% decrease in FEV1. The FEF(25-75) decreases more per mg methacholine. There were no subjects in whom there was > or = 20% decrease in FEV1 without a > or = 25% decrease in FEF(25-75). The mean FEF(25-75)/FVC after diluent inhalation = 0.87 +/- 0.27 standard deviation with a range of 0.23 to 1.67. The doses at which the FEF(25-75)/FVC decreased by > or = 20% and by > or = 30% was significantly lower than the corresponding doses causing a 20% decrease in FEV1. FEF(25-75) and the FEF(25-75)/FVC are more sensitive but less specific than the FEV1 as indicators of a positive response to a methacholine challenge. The FEF(25-75)/FVC does not provide additional information to that provided by the FEF(25-75).     

Spirometry and maximal expiratory flow-volume curve reference standards for Polynesian, European, and Chinese teenagers

Lung function was compared and reference standards were determined in 1,007 Polynesian, European, and Chinese teenagers attending school in Tahiti (517 boys, 490 girls; mean age, 14.4 years). Spirometric study results and maximal expiratory flow-volume curves were measured using techniques recommended by the American Thoracic Society. Age, standing height, and weight were chosen as the independent variables for males, and age and standing height for females. Regression equations constructed with logarithmically transformed dependent variables provided accurate predictions. We observed significant racial differences: in the Europeans, forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were higher than the mean values predicted for the whole study population, while forced expiratory flow during the middle half of the FVC (FEF25-75%) and maximal expiratory flows after 25, 50, and 75 percent of FVC had been exhaled (V max 25, 50, and 75, respectively) were about equal to the mean values; in the Polynesians, volumes and flows were mostly lower than the mean; in the Chinese, FVC in boys and girls, and FEV1 in girls only, were lower, while the other flows were higher. The FEV1/FVC, FEF25-75%/FVC, Vmax25/FVC, Vmax50/FVC, and Vmax75/FVC were significantly higher than the mean in the Chinese boys and girls and often lower in the Europeans.