How accurate is spirometry at predicting restrictive pulmonary impairment?

OBJECTIVE: To determine the accuracy with which spirometric measurements of FVC and expiratory flow rates can diagnose the presence of a restrictive impairment. DESIGN: The pulmonary function tests of 1,831 consecutive white adult patients who had undergone both spirometry and lung volume measurements on the same visit over a 2-year period were analyzed. The probability of restrictive pulmonary impairment, defined as a reduced total lung capacity (TLC) below the lower limit of the 95% confidence interval, was determined for each of several categoric classifications of the spirometric data, and additionally for each of several interval levels of the FVC and the FEV1/FVC ratio. SETTING: A large clinical laboratory in a university teaching hospital using quality-assured and standardized spirometry and lung volume measurement techniques according to American Thoracic Society standards. RESULTS: Two hundred twenty-five of 1,831 patients (12.3%) had a restrictive defect. The positive predictive value of spirometry for predicting restriction was relatively low; of 470 patients with a low FVC on spirometry, only 41% had restriction confirmed on lung volume measurements. When the analysis was confined to the 264 patients with a restrictive pattern on spirometry (ie, low FVC and normal or above normal FEV1/FVC ratio), the positive predictive value was 58%. Conversely, spirometry had a very favorable negative predictive value; only 2.4% of patients (32 of 1,361) with a normal vital capacity (VC) on spirometry had a restrictive defect by TLC measurement. The probability of a restrictive defect was directly and linearly related to the degree of reduction of FVC when the FVC was < 80% of predicted (p = 6.002). Combining the FVC and the FEV1/FVC ratio improved the predictive ability of spirometry; for all values of FVC < 80% of the predicted amount, the likelihood of restrictive disease increased as the FEV1/FVC ratio increased. CONCLUSIONS: Spirometry is very useful at excluding a restrictive defect. When the VC is within the normal range, the probability of a restrictive defect is < 3%, and unless restrictive lung disease is suspected a priori, measurement of lung volumes can be avoided. However, spirometry is not able to accurately predict lung restriction; < 60% of patients with a classical spirometric restrictive pattern had pulmonary restriction confirmed on lung volume measurements. For these patients, measurement of the TLC is needed to confirm a true restrictive defect.     

Daytime hypercapnia in adult patients with obstructive sleep apnea syndrome in France, before initiating nocturnal nasal continuous positive airway pressure therapy

CONTEXT: Daytime hypercapnia in patients with obstructive sleep apnea syndrome (OSAS) has a highly variable prevalence in the published studies, and is usually thought to be the consequence of an associated disease, COPD, or severe obesity. STUDY OBJECTIVES: To assess the prevalence of daytime hypercapnia in a very large population of adult patients with OSAS, free of associated COPD, and with a wide range of body mass index (BMI), and to evaluate the relationship between daytime hypercapnia and the severity of obesity and obesity-related impairment in lung function. DESIGN: Retrospective analysis of prospectively collected data. METHODS: The database of the observatory of a national nonprofit network for home treatment of patients with chronic respiratory insufficiency (Association Nationale pour le Traitement a Domicile de l'Insuffisance Respiratoire Chronique) was used. Collected data at treatment initiation were age, apnea-hypopnea index, BMI, FEV(1), vital capacity (VC), and arterial blood gases. The study included 1,141 adult patients with OSAS treated in France with nocturnal nasal continuous positive airway pressure (CPAP), FEV(1) >/= 80% predicted, FEV(1)/VC >/= 70%, and absence of restrictive respiratory disease other than related to obesity. RESULTS: The prevalence of daytime hypercapnia (Paco(2) >/= 45 mm Hg) before initiating CPAP therapy was 11% in the whole study population. The prevalence of daytime hypercapnia was 7.2% (27 of 377 patients) with BMI < 30, 9.8% (58 of 590 patients) with BMI from 30 to 40, and 23.6% (41 of 174 patients) with BMI > 40. Patients with daytime hypercapnia had significantly higher BMI values and significantly lower VC, FEV(1), and Pao(2) values than the normocapnic patients. Stepwise multiple regression showed that Pao(2), BMI, and either VC or FEV(1) were the best predictors of hypercapnia, but these variables explained only 9% of the variance in Paco(2) levels. CONCLUSION: Daytime hypercapnia was observed in > 1 of 10 patients with OSAS needing CPAP therapy and free of COPD, and was related to the severity of obesity and obesity-related impairment in lung function. However, other mechanisms than obesity are probably involved in the pathogenesis of daytime hypercapnia in OSAS.     

Longitudinal changes of body mass index, spirometry and diffusion in a general population.

The aim of this study was to evaluate the effects of body mass index (BMI) changes over an 8-yr follow-up, on longitudinal changes of vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and carbon monoxide diffusing capacity of the lung (DL,CO) indices in a general population sample of North Italy. To avoid including weight changes possibly related to physical growth, only the 1,426 adults (>24 yrs, 46% males) with complete follow-up were selected. Median linear regression models were applied to estimate the medians of change (computed as follow-up minus baseline values) of VC, FVC, FEV1 and DL,CO indices, as functions of changes of BMI over the follow-up period, separately by sex, after considering several potential confounders and effect modifiers. The extent of lung function loss tended to be higher among those who, at baseline, reported greater BMI values. Males experienced larger losses than females (20 and 16 mL FEV1 median reduction for a BMI unit increase in males and females, respectively). Conversely, longitudinal changes of BMI caused a slight and nonsignificant increase in DL,CO values in both sexes. Over an 8-yr follow-up, the detrimental effect of gaining weight might be reversible for many adults as most of those who reduced their body mass index values also increased their lung function. Overweight patients with ventilatory impairment should be routinely encouraged to lose weight for improving their lung function.     

Small airways obstruction syndrome.

STUDY OBJECTIVES: To clarify the significance of a functional lung pattern characterized by a decreased vital capacity (VC) and an increased residual volume (RV), but with a normal FEV1/VC ratio. SETTING: A university teaching hospital. SUBJECTS: Patients with bronchial asthma, pulmonary emphysema, and small airways disease, and older subjects. MEASUREMENTS: Measurements of static and dynamic lung volumes, diffusing capacity of the lung for carbon monoxide (as measured by the single-breath method), nitrogen slope of the alveolar plateau, and closing volume (as measured by the single-breath O2 test). CONCLUSION: A functional pattern characterized by a decreased VC and FEV1 and increased RV, but with a normal FEV1/VC ratio and total lung capacity, reflects an obstructive impairment of small airways.     

Lung hyperinflation and its reversibility in patients with airway obstruction of varying severity

The natural history of lung hyperinflation in patients with airway obstruction is unknown. In particular, little information exists about the extent of air trapping and its reversibility to bronchodilator therapy in those with mild airway obstruction. We completed a retrospective analysis of data from individuals with airway obstruction who attended our pulmonary function laboratory and had plethysmographic lung volume measurements pre- and post-bronchodilator (salbutamol). COPD was likely the predominant diagnosis but patients with asthma may have been included. We studied 2,265 subjects (61% male), age 65 ± 9 years (mean ± SD) with a post-bronchodilator FEV(1)/FVC <0.70. We examined relationships between indices of airway obstruction and lung hyperinflation, and measured responses to bronchodilation across subgroups stratified by GOLD criteria. In GOLD stage I, vital capacity (VC) and inspiratory capacity (IC) were in the normal range; pre-bronchodilator residual volume (RV), functional residual capacity (FRC) and specific airway resistance were increased to 135%, 119% and 250% of predicted, respectively. For the group as a whole, RV and FRC increased exponentially as FEV(1) decreased, while VC and IC decreased linearly. Regardless of baseline FEV(1), the most consistent improvement following bronchodilation was RV reduction, in terms of magnitude and responder rate. In conclusion, increases (above normal) in airway resistance and plethysmographic lung volumes were found in those with only minor airway obstruction. Indices of lung hyperinflation increased exponentially as airway obstruction worsened. Those with the greatest resting lung hyperinflation showed the largest bronchodilator-induced volume deflation effects. Reduced air trapping was the predominant response to acute bronchodilation across severity subgroups.     

Pulmonary function and resting breathing pattern in myotonic dystrophy

In 17 patients with myotonic dystrophy, spirometric, flow-volume, and maximal mouth occlusion variables were obtained and compared with 8 normal subjects. Ventilatory CO₂, response was measured by the estimation of the steady-state effect of a sufficiently large serial dead space. Variability of resting breathing pattern was expressed by the variation coefficients of respiratory cycle time and tidal volume.The group means of the total lung capacity (TLC), vital capacity (VC), forced expiratory volume in 1 sec (FEV)₁, and forced inspiratory volume in 1 sec (FIV)₁, showed a restrictive pattern. Only maximal static mouth pressure (Pi,max), measured at residual volume (RV) level, showed a significant positive correlation with both VC (p = 0.03) and FIV₁, (p = 0.02), suggesting inspiratory muscle weakness as a determinant of the restriction.Although the differences were just not significant, both variation coefficients of the respiratory cycle time and tidal volume were larger in the group with a CO, sensitivity below the lower limit of normal compared to those with a normal ventilatory response to CO₂. In 3 patients, fluctuations in FRC were also present. We hypothesize that, in addition to the already documented FRC fluctuations by uncoordinated spontaneous intercostal muscle action, a defect of integration of afferent neural input and chemical drive in the medullary region may also be present in these patients.     

LUNG FUNCTION AND RESPIRATORY MUSCLE STRENGTH AFTER PROPRANOLOL IN THYROTOXICOSIS

Thirty-five thyrotoxic patients were assessed before treatment, after treatment with propranolol, and after antithyroid drugs. The first group of patients ( n = 17) performed the following tests at all three assessment points: forced expiratory volume in the first second (FEV,), vital capacity (VC), functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), maximal mid-expiratory flow rate (MMFR), diffusing capacity for carbon monoxide (DLCO), and maximum static inspiratory and expiratory mouth pressures (Plmax and PEmax). Arterial blood gas analysis was also performed for the first group of patients. No significant changes were seen either after propranolol or after antithyroid drugs in the FRC, RV, TLC, MMFR, DLCO, or blood gases. The remaining 18 patients, group 2, performed only the FEV₁, VC, Plmax, and PEmax tests at each assessment. The only index of respiratory function that improved significantly after propranolol was Plmax (from 46.5 ± 16.5 to 53.2 ± 22 cmH₂O, p < 0.01). This suggests that adrenergic excess may play a role in thyrotoxic inspiratory muscle weakness. After antithyroid drugs, Plmax, PEmax, FEV₁, and VC all increased significantly as expected. (Aust NZ J Med 1986; 16: 496–500.)     

Bronchodilator response in residual volume in irreversible airway obstruction

BACKGROUND: Although airway obstruction, as defined by improvement of forced expiratory volume in one second (FEV1) and/or forced vital capacity (FVC), is irreversible in patients with COPD, they clearly seem to benefit from treatment with inhaled bronchodilators. AIMS: To assess the response pattern of residual volume (RV) compared to FEV1 after bronchodilation in patients with reversible and irreversible airway obstruction. METHODS: Changes in static lung volumes were compared with improvement in dynamic lung volumes in 396 consecutive patients undergoing reversibility testing with repeat bodyplethysmography. Reversibility was defined as improvement of FEV1 >200 ml and >12% after inhalation of fenoterol hydrobromide. RESULTS: Irreversibility was found in 297 out of 396 patients with airway obstruction. Except for total lung capacity (TLC), all parameters (residual volume [RV], vital capacity [VC], forced inspiratory vital capacity [IVC], forced vital capacity [FVC], forced expiratory volume in one second [FEV1] and the FEV1/VC ratio) showed statistically significant changes after bronchodilation in 396 patients. The multiple linear regression model adjusted for age, sex and BMI showed a non-linear relationship between DeltaFEV1 or DeltaVC compared to DeltaRV after bronchodilation. If the increase in DeltaFEV1 is lower than 0.1 L, DeltaRV remains constant. However, if the increase in DeltaFEV1 is more than 0.1 L, DeltaRV decreases too. The same is found at an increase in VC of 0.3 L. CONCLUSION: In summary, in patients with irreversible airway obstruction DeltaRV cannot be predicted by DeltaFEV1 or DeltaVC after bronchodilation. Therefore, spirometric assessment should be complemented by bodyplethysmography.     

Pulmonary function in adolescents with ataxia telangiectasia

INTRODUCTION: Pulmonary complications are common in adolescents with ataxia telangiectasia (A-T), however objective measurements of lung function may be difficult to obtain because of underlying bulbar weakness, tremors, and difficulty coordinating voluntary respiratory maneuvers. To increase the reliability of pulmonary testing, minor adjustments were made to stabilize the head and to minimize leaks in the system. Fifteen A-T adolescents completed lung volume measurements by helium dilution. To assess for reproducibility of spirometry testing, 10 A-T adolescents performed spirometry on three separate occasions. RESULTS: Total lung capacity (TLC) was normal or just mildly decreased in 12/15 adolescents tested. TLC correlated positively with functional residual capacity (FRC), a measurement independent of patient effort (R2=0.71). The majority of individuals had residual volumes (RV) greater than 120% predicted (10/15) and slow vital capacities (VC) less than 70% predicted (9/15). By spirometry, force vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1) values were reproducible in the 10 individuals who underwent testing on three separate occasions (R=0.97 and 0.96 respectively). Seven of the 10 adolescents had FEV1/FVC ratios>90%. CONCLUSION: Lung volume measurements from A-T adolescents revealed near normal TLC values with increased RV and decreased VC values. These findings indicate a decreased ability to expire to residual volume rather then a restrictive defect. Spirometry was also found to be reproducible in A-T adolescents suggesting that spirometry testing may be useful for tracking changes in pulmonary function over time in this population.     

A normal FEV1/VC ratio does not exclude airway obstruction

BACKGROUND: A decreased forced expiratory volume in 1 s/vital capacity (FEV(1)/VC) ratio is the hallmark of the definition of airway obstruction. We recently suggested that a lung function pattern, we called small airways syndrome (SAOS), has a normal FEV(1)/VC and total lung capacity (TLC) and reflects obstruction of small airways. OBJECTIVES: To substantiate our hypothesis we measured and compared lung function tests including maximal expiratory flow rates (MEFR), sensitive indicators of airway obstruction, in SAOS subjects and in matched controls. METHODS: We selected 12 subjects with the pattern of SAOS, but without chronic lung or heart disease (average age: 40.7 +/- 7.8 years) and 36 age-matched subjects with normal lung function (42.8 +/- 6.3 years). We measured static and dynamic lung volumes, MEFR and lung diffusing capacity (DL(CO)). RESULTS: SAOS subjects were heavier smokers (p < 0.05) and body mass index was less than in control subjects (p < 0.01). Both FEV(1)/VC ratio and TLC were comparable in the two groups. However, FEV(1), VC, DL(CO), and MEFR were lower and residual volume (RV) and RV/TLC ratio were higher (p < 0.05) in the SAOS group than in the control one. Furthermore, the MEFR curve of the SAOS group was displaced to the left without any change in slope, suggesting premature airway closure. CONCLUSION: Our results suggest that a normal FEV(1)/VC ratio does not exclude airway obstruction. A decrease of FEV(1), provided TLC is normal, reflects small airway obstruction.     

Lung volumes in healthy Afro-Caribbean children aged 4-17 years

Lung volumes in healthy children differ according to their ethnic origin. We wished to determine if any differences in the lung volumes of Afro-Caribbean (AC) children from those predicted by Caucasian reference values disappeared if the results were related to sitting height or to 90% or 77% of lung volumes predicted for height from Caucasian reference values based on standing height. We took, as our working hypothesis, that it is inappropriate to use Caucasian reference values to interpret data from Afro-Caribbean children, and that ethnic-specific reference values are required. This was a prospective, observational study. Subjects included 80 AC children with a median age of 9 (range, 4.3-17.8) years. Standing and sitting height were measured. Lung volumes were measured by body plethysmography (total lung capacity, TLC(pleth); functional residual capacity, FRC(pleth); and vital capacity, VC(pleth)), helium gas dilution (functional residual capacity, (FRC(He)), spirometry (forced expiratory volume in 1 sec, FEV(1)), and forced vital capacity (FVC). The lung volumes of AC children correlated significantly with standing height, but differed significantly from values predicted from Caucasian reference values based on standing height (P < 0.05). Significant differences remained for TLC(pleth), FRC(pleth), FRC(He), RV(pleth), VC(pleth), FEV(1), and FVC when the results were related to sitting height or 90% or 77% of values predicted from Caucasian reference values based on height (P < 0.05). Lung volumes in Afro-Caribbean children should be compared to ethnic-specific reference values.     

Respiratory function in children undergoing bone marrow transplantation.

We conducted a prospective study of respiratory function in children undergoing bone marrow transplantation (BMT) for onco-hematological disorders. Each child was evaluated before and 100 days after BMT. The investigations included clinical examination, chest X-ray, and pulmonary function tests (PFT) to determine: slow vital capacity (VC), functional residual capacity (FRC), total lung capacity (TLC), forced expiratory volume in 1 s (FEV1), carbon monoxide diffusing capacity (DLCO), ratio of residual volume (RV) to TLC, and FEV1/VC. The values obtained before and after BMT were compared to predicted values, and the post-BMT values were compared to the pre-BMT values (Student's t-test). From 1986 to 1995, 77 children underwent BMT, of whom 39 were available for testing. The pre-BMT VC (P = 0.0234) and DLCO (P < 0.0001) were lower and FRC higher (P < 0.0001) than predicted values. After BMT, the VC (P = 0.004), TLC (P = 0.044), and FEV1 (P = 0.012) were lower, and the RV/TLC ratio was higher (P = 0.043), compared with pre-BMT data. The observed respiratory abnormalities were not clinically relevant. The only identifiable risk factor for a decrease in lung function was age at BMT. This study shows that some lung dysfunction may be present before BMT and be further altered by BMT. This stresses the need for longitudinal respiratory monitoring and follow up to detect such dysfunctions and to insure an optimal treatment program for these children.     

50例健康老年人肺功能10年随访观察

目的为临床和基础研究提供健康老年人肺功能各项指标随增龄改变的参考资料。方法采用日本Ｃｈｅｓｔａｃ６５型肺功能检查仪,按常规方法进行肺功能检查。结果用力肺活量（ＦＶＣ）每年下降００３２Ｌ,第１秒用力呼气量（ＦＥＶ１）每年下降００３Ｌ,ＦＥＶ１占用力肺活量比值（ＦＥＶ１％）每年下降０１５１％,呼气流量峰值（ＰＥＦＲ）每年下降０１１８Ｌ／ｓ,最大呼气中段流量（ＭＭＥＦ）每年下降００４Ｌ／ｓ,最大通气量（ＭＶＶ）每年下降０８７６Ｌ,肺活量（ＶＣ）每年下降００４Ｌ,残气容积（ＲＶ）每年升高００３３Ｌ,功能残气量（ＦＲＣ）每年升高００３３Ｌ,残气容积／肺总量（ＲＶ／ＴＬＣ）每年升高０５９６％。戒烟组的健康老年人ＶＣ、ＦＶＣ、ＦＥＶ１、ＲＶ、ＲＶ／ＴＬＣ与从不吸烟健康老年人比较差异有显著性;不同年龄组的健康老年人肺功能下降不明显。结论肺功能各项指标随增龄而改变,健康老年人各年龄组肺功能改变不明显,吸烟对健康老年人肺功能改变有一定影响。     

Relevance of dyspnoea and respiratory function measurements in monitoring of asthma: a factor analysis

Previous studies in patients with stable chronic obstructive pulmonary disease have demonstrated that objective measures (lung volumes and respiratory muscle force) and clinical or subjective measures (symptoms of breathlessness and exercise tolerance) are quantities that independently characterize the conditions of these patients. Such an evaluation has not been previously applied in patients with stable bronchial asthma. Sixty-nine patients with stable chronic asthma underwent evaluation of static (functional residual capacity, FRC) and dynamic [forced expiratory volume in 1 sec (FEV1) and forced vital capacity, FVC] lung volumes; respiratory muscle strength (RMS), by measuring maximal inspiratory and expiratory pressures, and exercise capacity by means of the 6-min walking distance (6MWD). Chronic exertional dyspnoea was assessed by the Baseline Dyspnoea Index (BDI) focal score and by the Medical Research Council (MRC) scale. Statistical evaluation was performed by applying factor analysis. Three factors accounted for 78% of the total variance in the data: FEV1, FVC loaded on a factor I; RMS, FRC and 6MWD loaded on a factor II; dyspnoea ratings loaded on a factor III. Post-hoc analysis by randomly dividing the patients into two subgroups gave the same results. In asthmatic patients, airway obstruction appeared as an independent dimension or factor. Dyspnoea independently characterized the condition of asthma. Submaximal exercise tolerance could not be associated with the symptom of breathlessness. Evidence of independent factors support the validity of routine, multi-factorial assessment and the primary goal of treatment to alleviate symptoms and improve functional capacity in stable asthmatics.     

Acute and chronic pulmonary function changes in allergic bronchopulmonary aspergillosis.

Pulmonary functions of patients with allergic bronchopulmonary aspergillosis were studied during an acute episode (n = 6); during a mean follow-up period of 44 months (range four months--14.8 years) (n = 16); and for any correlation between duration of ABPA and asthma with the total lung capacity (helium dilution), 1 second forced expiratory volume (FEV1), vital capacity, 1 second forced expiratory volume-forced vital capacity ratio (FEV1:FVC per cent) and diffusing capacity of carbon monoxide (DL:CO) (single breath) for the entire group (n = 22). All patients were treated with corticosteroids (intermittent or continuous) and bronchodilators. For the 16 patients, slopes using linear regression analysis were determined from the function as per cent predicted versus time in months from diagnosis and then analyzed for significance. Significant functional loss was shown in three of 16 patients for FEV1, two of 16 patients for vital capacity, one of 16 patients for FEV1:FVC per cent, none of 10 patients for DL:CO and one of 10 patients for total lung cital capacity, FEV1:FVC per cent and the duration of asthma or allergic bronchopulmonary aspergillosis was found by multiple regression analysis correcting for age and smoking (mean 4.24 years; range 0.3 to 14.8 years). Roentgenographic criteria and blood eosinophilia were used to define a "flare" of allergic bronchopulmonary aspergillosis. The six patients during a flare showed a significant reduction in total lung capacity (P less than 0.001), vital capacity (P less than 0.05), FEV1 (P less than 0.01) and DL:CO (P less than 0.001) which uniformly returned to baseline values during steroid therapy. The FEV1:FVC per cent remained unaltered. These findings, contrary to suggestions in the literature, indicate that in the majority of our patients there was no significant progressive functional deterioration after diagnosis. However, during acute episodes of allergic bronchopulmonary aspergillosis, transient reduction of volumes and DL:CO were uniformly present.     

Effects of bracing on lung function in idiopathic juvenile kyphosis

Although considerable information is available on the effects of bracing on lung function in kyphoscoliosis, there is a paucity of data on idiopathic juvenile kyphosis (IJK). The present study was designed to investigate the immediate effect of bracing on lung function in children and adolescents with mild-to-moderate IJK. Spirometry, measurement of lung volumes, and arterial oxyhemoglobin saturation (SaO(2)) were performed in 24 patients, 9-17 years of age, who were treated with a corrective brace for mild-to-moderate IJK (Cobb angle, 46-75 degrees ). Children were studied when braced and unbraced.When children were unbraced, mean percent predicted values (+/-standard deviation) for total lung capacity (TLC), vital capacity (VC), functional residual capacity (FRC), and forced expiratory volume in 1 sec (FEV(1)) were 100.0% (+/-13.0%), 92.7% (+/-14.2%), 108.2% (+/-20.4%), and 95.0% (+/-16.3%), respectively. With the brace on, significant reductions occurred in all lung function measurements: TLC decreased by 9.5% (P < 0.001), VC by 9.3% (P = 0.001), FRC by 14.2% (P = 0.005), and FEV(1) by 8.9% (P = 0.009). SaO(2) decreased from 96.2% (+/-1.6%) to 95.2% (+/-1.4%) (P = 0.027). An inverse relationship was observed between pre- and postbracing change in TLC and Cobb angle children (P = 0.021).Our findings indicate that corrective bracing in mild-to-moderate IJK results in mild lung restriction and a clinically insignificant drop in SaO(2). The effect of bracing on TLC decreases as the severity of kyphosis increases in these patients.     

Pulmonary function tests in children with beta-thalassemia major

Lung function abnormality is a known complication of thalassemia, but the results of studies in pulmonary function have been inconsistent. This study was conducted to describe the type of lung impairment in thalassemic children. Pulmonary function tests were conducted in 40 children with beta-thalassemia major, 23 males and 17 females. Tests included spirometry, total lung capacity (TLC), single breath diffusing capacity of the lung for carbon monoxide (DL(CO)) and arterial blood gases. Serum ferritin level was measured in all children to study its relationship to lung function impairment. A predominantly restrictive pattern was seen in 14 patients (35%). These patients had a significant reduction in RV, FVC, TLC and PEF with an FEV1/FVC ratio of more than 75%. Obstructive airway disease was found in six patients (15%), with an FEV1/FVC ratio less than 75%, increased RV and reduced FEF(25%-75%). Impairment of diffusion was found in 10 patients (25%), with DL(CO) reduced to less than 80% of the predicted value. Arterial blood gases results showed that no patient was hypoxic. No correlation was found between the severity of restrictive or obstructive disease and the serum ferritin level. There was a significant linear correlation between age and serum ferritin level (P < 0.019). Patients with thalassemia have a predominantly restrictive lung dysfunction pattern. This may be due to pulmonary parenchymal pathology, although the reason for the obstructive pattern seen in a small proportion of patients remains obscure.     

Nutritional depletion in patients on long-term oxygen therapy and/or home mechanical ventilation.

The purpose of this study was to estimate the prevalence of malnutrition in outpatients on long-term oxygen therapy or home mechanical ventilation, to determine the relationships between malnutrition and impairment/disability and smoking and also to identify relevant tools for routine nutritional assessment. In 744 patients (M:F 1.68, aged 65+/-15 yrs) with chronic obstructive pulmonary disease (COPD, 40%), restrictive disorders (27%), mixed respiratory failure (15%), neuromuscular diseases (13%) and bronchiectasis (5%), body mass index (BMI), fat-free mass (FFM), serum albumin, transthyretin, 6-min walking test, forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and blood gases were recorded. FFM was the most sensitive parameter for detecting malnutrition, being abnormal in 53.6% of patients, while BMI was <20 in 23.2%, serum albumin <35 g x L(-1) in 20.7%, and serum transthyretin <200 mg x L(-1) in 20%. FFM depletion predominated in neuromuscular, bronchiectasis and restrictive disorders. BMI and FFM were correlated with FEV1, FVC and 6-min walking test. In multivariate analysis a BMI<20 was related to FEV1 and smoking habits, and a low FFM to smoking, FEV1 and female sex. Malnutrition is highly prevalent in home-assisted respiratory patients and is related to causal disease, forced expiratory volume in one second, smoking and disability. Fat-free mass appeared to be the most sensitive and relevant nutritional parameter according to impairment and disability.     

Comparison of subjective and objective measures in recurrently wheezy infants

OBJECTIVES: The aim of this study was to compare subjective measures (overall health assessment both by the study physician and the child's mother) with objective measurements of forced expiratory volumes (FEV(t)) and maximal flow at functional residual capacity V(max)FRC) in recurrently wheezy infants. METHODS: Sixteen wheezy infants (12 boys) aged 8-26 months were studied. A clinical assessment at visit 1 was followed by the run-in period during which day- and nighttime asthma symptom scores were obtained. The actual study period consisted of 2 visits when patient's lung function was assessed. The first of which was during an acute exacerbation (visit 2), while the second was when the infant was asymptomatic (visit 3). FEV(t) were obtained by the raised volume rapid thoracic compression technique (RVRTC) and V(max)FRC by the tidal volume rapid thoracic compression technique (TVRTC). RESULTS: Mean FEV(t) but not mean V(max)FRC were significantly lower at visit 2 compared to visit 3 (FEV(0.5): p = 0.005, and FEV(0.75): p = 0.002; V(max)FRC: p = 0.15) and correlated well with overall health assessment by the study physician (FEV(0.5): r = 0.82, and FEV(0.75): r = 0.84), but not with the overall health assessment by the mother. CONCLUSIONS: We have shown in the present study that objective measurements of FEV(t) from a raised lung volume correlate well with the overall health assessment by the study physician; this was in contrast to measurements of V(max)FRC in the tidal volume range. We therefore conclude that the RVRTC technique is a feasible method to assess and monitor obstructive lung disease in infancy.     

Pulmonary capillary blood volume in hyperpnea-induced bronchospasm

Reactive hyperemia of the bronchial circulation has been postulated to contribute to the airway narrowing that occurs following exercise or hyperpnea in subjects with asthma with hyperpnea-induced bronchospasm (HIB). Changes in lung parenchymal mechanics also occur in HIB, including increases in peripheral airway resistance. Since the peripheral airways and lung parenchyma are supplied by the pulmonary circulation, and changes in the pulmonary circulation could alter airway resistance or tissue mechanics, we hypothesized that pulmonary capillary blood flow would increase in association with HIB, resulting in increases in pulmonary capillary blood volume (VC). We measured VC by using two test gases of varying oxygen concentration to determine the diffusing capacity of the lung for carbon monoxide (DL(CO)) before and after a period of hyperpnea in 13 subjects with asthma with HIB and 10 control subjects without asthma. Despite subjects with asthma having a significant fall in FEV(1) following hyperpnea compared with control subjects (DeltaFEV(1) = -26 +/- 12 versus -4 +/- 4%, mean +/- SD, p < 0.001), there was no change in the DL(CO) or VC from baseline values. We conclude that pulmonary capillary blood volume does not change following hyperpnea, and therefore that changes in pulmonary blood flow are not associated with HIB.