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.     

Trapped gas and airflow limitation in children with cystic fibrosis and asthma

Trapped gas (TG) has been shown to be present in cystic fibrosis (CF) and asthma, but its relationship with airflow limitation (AL) has not been explored. TG was defined as the difference between the functional residual capacity measured by body plethysmography [FRC(BP)] and that measured by helium dilution [FRC(He)] expressed as a percentage of total lung capacity (TLC). We studied 21 children with CF and 15 with asthma who had a similar degree of AL and hyperinflation, however the children with CF had greater amounts of TG compared with asthma [15% +/- 2 (mean +/- 1 SE) vs 8 +/- 2, P less than 0.05]. Mixing efficiency (ME), an index of the distribution of ventilation, was found to be lower in the CF children than in those with asthma (34 +/- 4 vs 54 +/- 4). In CF, TG correlated with forced expiratory flow between 25 and 75% of vital capacity (FEF25-75), ME, RV/TLC, and maximal expiratory flow rates at 25 and 50% of vital capacity (Vmax25 and 50, respectively; r = -0.66, -0.61, 0.72, -0.71, -0.74). ME also correlated with the above measures. In asthma, TG did not correlate with the FEF25-75, ME, RV/TLC, Vmax25, or Vmax50. Furthermore, TG was frequently found in patients with asthma with moderate AL while it was often absent in patients with severe AL. For both CF and asthma, neither the severity of AL nor the magnitude of the TG could be predicted from the increase in Vmax50 with helium (delta V50).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of airway inflation pressure on forced expiratory maneuvers from raised lung volume in infants.

The raised lung volume technique is increasingly used to measure forced expiratory maneuvers in infants. However, there is no consensus regarding the optimal airway inflation pressure (P(inf)) required for such maneuvers, or the influence of small changes in P(inf) within and between infants. The aim of this study was to assess the effect of small differences (0.2-0.3 kPa) in P(inf) on forced vital capacity (FVC), forced expired volume in 0.5 sec (FEV(0.5)), and forced expired flow at 75% of vital capacity (FEF(75)), all derived from the raised volume rapid thoraco-abdominal compression (RVRTC) technique. Randomized paired forced expiratory maneuvers were obtained in 32 healthy infants ( 3.9-39.3 weeks old, 3.8-9.9 kg) with the safety pressure relief valve for P(inf) set to 2.7 kPa or 3.0 kPa (27 or 30 cm H(2)0). When mean (SD) P(inf) was increased by 8.4 (2.8)%, there was a significant (P < 0.01) increase in mean (SD) FVC, FEV(0.5), and FEF(75) by 5.8 (5.7)%, 6.1 (6)%, and 8.3 (16.2)%, respectively. In conclusion, relatively small differences in P(inf) will result in significant differences in FVC, FEV(0.5), and FEF(75) by RVRTC technique. Precision in setting and reporting the applied P(inf) is therefore essential, particularly if data are to be compared between centers.     

Quantitative computed tomography detects peripheral airway disease in asthmatic children

The aim of this study was to compare air-trapping as quantified by high-resolution computed tomography (HRCT) of the chest with measures of lung function and airway inflammation in children with mild to moderate asthma. Plethysmography indices, respiratory resistance, and reactance before and after bronchodilator with impulse oscillation (IOS), exhaled nitric oxide (eNO), total eosinophil count (TEC), and serum eosinophil cationic protein (ECP) levels were measured in 21 subjects. A single-cut HRCT image at end-expiration was obtained. Air-trapping was quantified and expressed in terms of the pixel index (PI) by determining the percentage of pixels in lung fields below -856 and -910 Hounsfeld units (HU). Pairwise linear correlations between PI and other parameters were evaluated. Subjects had only mild airflow limitation based on prebronchodilator forced expiratory volume in 1 sec (FEV(1)), but were hyperinflated and had air-trapping based on elevated total lung capacity (TLC) and residual volume (RV)/TLC ratio, respectively. The PI at -856 HU was positively correlated with % predicted TLC, total gas volume (TGV), and ECP level, and was inversely correlated with FEV(1)/forced vital capacity (FVC) and % predicted forced expiratory flow between 25-75% FVC (FEF(25-75)). The PI at -910 HU correlated similarly with these variables, and also correlated positively with IOS bronchodilator reversibility. This data suggest that quantitative HRCT may be a useful tool in the evaluation of peripheral airflow obstruction in children with asthma.     

Lung growth and function in children and adolescents with idiopathic pectus excavatum

Patterns of lung growth and function were studied retrospectively in 103 patients (73 male and 30 female) with idiopathic pectus excavatum in order to determine: 1) the prevalence of restrictive lung defect and/or other lung function abnormalities; 2) the possible association between type of lung function abnormalities and age of the patient; and 3) whether the type of lung function is associated with other clinical conditions. Forty-three patients (42%) were between 5-9 years of age; 36 (35%) were between 10-14 years; and 24 (23%) were between 15-19 years. Restrictive lung disease was detected only in 5 patients (5%), whereas 42 patients (41%) had evidence of obstructive pattern, and the remaining 56 patients (54%) had a normal pattern. The mean values for lung volume (total lung capacity (TLC) and/or forced vital capacity (FVC)) were lowest in the 10-14-year group, whereas the mean values of the indices of lower airway function (forced expiratory volume at 1 sec (FEV(1)), FEV(1)/FVC, forced expiratory flow at 25-75% of forced vital capacity (FEF(25-75)), and FEF(25-75)/FVC) were higher in the younger group. Residual volume (RV) and RV/TLC were elevated in all age groups, but they declined toward normalization with increasing age. There were no significant differences between groups (stratified either by pattern of lung function or by age) with regard to their demographics or clinical characteristics (scoliosis, direction of sternal rotation, history of asthma/reactive airways disease, or exercise intolerance). We conclude that idiopathic pectus excavatum may be associated with a variety of lung function abnormalities (in particular, lower airway obstruction) even in the absence of overt clinical symptoms. There was no evidence of significant worsening of lung function with increasing age.     

Lower airway obstruction, bronchial hyperresponsiveness, and primary pulmonary hypertension in children

We investigated the prevalence and reversibility of lower airway obstruction (LAO) and its correlation with pulmonary artery pressure in children with primary pulmonary hypertension (PPH). The analysis was performed retrospectively in a cohort of children with PPH between 5-18 years of age. PPH was defined as mean pulmonary artery pressure (PAPm) >25 mmHg at rest, or >30 mmHg during exercise, with normal pulmonary capillary wedge pressure in the absence of other causes. Lower airway function was assessed by spirometry and maximal expiratory flow-volume curves. Lung volumes were measured by body plethysmography. Patients were assigned according to their pattern of lung function into "normal," "obstructive," and "restrictive" groups. The reversibility of LAO was defined as an increase of > or = 15% from baseline in forced expiratory volume at 1 sec (FEV1) and/or > or =20% in forced expiratory flow at 25-75% of forced vital capacity (FEF25-75%) in response to nebulized albuterol. An "obstructive" pattern was found in 23 children (59%), a "restrictive" pattern in 2 children (5%), and a "normal" pattern in 14 children (36%). Response to bronchodilator was documented in 78% of children with an "obstructive" pattern and in 22% of those with a "normal" pattern. The PAPm showed a significant positive correlation with the TLC, RV, and RV/TLC, but a negative one with the ratio FEV1/FVC. Our findings suggest that reversible LAO is the most common lung function abnormality among pediatric patients with PPH. Whether airway reactivity is a cause of or the result of PPH remains to be determined.     

Pulmonary function in bronchopulmonary dysplasia

The purpose of this study was to examine lung function and bronchodilator responsiveness in infants with a history of prematurity and bronchopulmonary dysplasia (BPD), using the raised volume rapid thoracoabdominal compression technique as well as with whole-body plethysmography. Spirometric measurements were obtained in 28 infants with a history of BPD, defined as preterm birth with O2 requirement at 36 weeks postmenstrual age (gestational age at birth, 26.4 +/- 2.1 weeks, mean +/- SD; birthweight, 898 +/- 353 g; age at study, 68.0 +/- 35.6 weeks). Fractional lung volumes were measured in 27 subjects. Values were expressed as percentage of predicted normal values. Compared to normal infants, those with a history of BPD exhibited decreases in forced expiratory flows including forced expiratory volume in 0.5 sec (76.3 +/- 19.6%), forced expiratory flow at 75% of expired forced vital capacity (FEF75; 59.5 +/- 30.7%), and FEF(25-75) (74.0 +/- 26.8%; P<0.01 for all). Functional residual capacity (107.9 +/- 25.3%), residual volume (RV, 124.5 +/- 42.7%), and RV/total lung capacity (RV/TLC, 128.2 +/- 35.3%) were increased in infants with a history of BPD (P<0.05 for each). There was no difference in TLC between groups. Seventeen infants were studied both pre- and postalbuterol, and 6 (35%) demonstrated significant bronchodilator responsiveness. Infants with recurrent wheezing showed greater expiratory flow limitation, hyperinflation, and airways responsiveness, whereas those without wheezing showed only modest airway dysfunction. We conclude that infants with a history of BPD have pulmonary function abnormalities characterized by mild to moderate airflow obstruction and air trapping.     

Ventilatory defect in coal workers with simple pneumoconiosis: early detection of functional abnormalities

Airway obstruction is a prominent feature in coal workers' pneumoconiosis (CWP). However, many patients with CWP have even demonstrated a normal forced vital capacity (FVC) and forced expiratory volume in 1s (FEV1). The purpose of this study was to evaluate the ventilatory defect by spirometry and search for parameters, other than FVC and FEV1, suitable for early detection of pulmonary impairment in CWP. A sample of 227 coal miners was selected from the medical clinics of two teaching hospitals. Maximal expiratory flow volume measurement and determination of functional residual capacity (FRC) and residual volume (RV) were carried out with an automated plethysmograph. The prevalence of airway obstruction (FEV1/FVC < 70%) in this sample of miners was 52.9% (120/227). There was a progression of functional impairment with the transition from category 0 to categories 2 and 3, no matter what the miners smoking habits. All of the 107 non-obstructed miners had a normal FVC and FEV1. However, the mean values for FEF25-75% (mean forced expiratory flow during the middle half of FVC) and Vmax50 (maximal expiratory flow rate at 50% FVC) were abnormally low, and RV was already elevated, in those non-obstructed subjects with category 1 simple pneumoconiosis. A borderline abnormally elevated FRC in the miners with radiological category 3 of CWP was also noted. We conclude that the Vmax50, FEF25-75%, and RV appeared to be the discriminative indices for detecting early ventilatory defect in non-obstructed patients with simple CWP. Further studies is still needed to clarify the cause of small airway dysfunction.     

Maximum inspiratory muscle endurance capacity during resistive loading in chronic obstructive pulmonary disease

In 10 patients with stable severe chronic obstructive pulmonary disease (COPD) we evaluated the relationship between the degree of airway obstruction and hyperinflation, and the maximum inspiratory muscle endurance capacity during added inspiratory resistive loading. We measured the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) and airway resistance (Raw) as indices of airway obstruction, and the ratio of functional residual capacity to total lung capacity (FRC/TLC) as an index of hyperinflation. The mean resting transdiaphragmatic pressure to its maximum (Pdi/Pdimax), the tension time index of the diaphragm, and the maximum transdiaphragmatic pressure (Pdimax) were also determined. Following 15 min of resting breathing, the patients breathed through added inspiratory resistances which were progressively increased every 3 min until exhaustion. Maximum endurance capacity (ECmax) was defined as the product of the esophageal pressure - time integral and frequency at the maximum load sustainable for 3 min. ECmax correlated significantly with Raw (r = -0.67, p less than 0.04). The addition of FRC/TLC to the analysis resulted in a significant increase in the correlation coefficient (r = 0.86, p less than 0.01). ECmax did not correlate with FEV1/FVC. Both resting Pdi/Pdimax and Pdimax independently influenced ECmax. In addition, Pdimax correlated significantly with FRC/TLC, and resting Pdi/Pdimax with Raw. We conclude that in stable patients with severe COPD, both airway obstruction and hyperinflation affect maximum inspiratory muscle endurance capacity during inspiratory resistive loading.     

Lung function in children and adolescents with tetralogy of Fallot after intracardiac repair

We studied lung function in 41 patients, aged 6–27 years, 1–5 years after intracardiac surgical repair (ICR) of tetralogy of Fallot (TOF) and about 5 years after the establishment of the Pediatric Cardiac Center in Prague. The measurements included vital capacity (VC). total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), forced expiratory flows (FEF), specific airway conductance (SGaw), lung recoil pressure (Pst), and specific static lung compliance (S_1st). Single or mutiple abnormal lung function parameters were found in 83% of patients. Lung function was not related to shunting operations prior to ICR, hemoglobin concentration, and hematocrit, and had no specific pattern. Pst at 100% TLC and 90% TLC declined with increasing age at ICR and at lung function testing, while SC, rose, as did the ratio FRC/TLC. Fifteen patients were studied before and after surgery. Single or multiple lung function tests were abnormal in 93% before and in 84% after ICR. After ICR the ratios FRC/TLC and also RV/TLC, FEF at 25% VC, and FEF at 60% TLC were less frequently abnormal, while Pst at 100% TLC and at 90% TLC, as well as SGaw and TLC, were more frequently abnormal after ICR. The results indicated a regression of smaller airway obstruction and lung hyperinflation after ICR. The evolution of abnormally compliant (emphysematous) lungs with growth of the patients might be a sign of permanent sequelae of early lung damage from abnormal pulmonary hemodynamics. Pediatr Pulmonol. 1993; 16:23–30. © 1993 Wiley-Liss, Inc.     

Timing and driving components of the breathing strategy in children with cystic fibrosis during exercise

The aim of this study was twofold: first, to determine the breathing strategies of children with cystic fibrosis (CF) during exercise, and secondly, to see if there was a correlation with lung function parameters. We determined the tension-time index of the inspiratory muscles (T(T0.1)) during exercise in nine children with CF, who were compared with nine healthy children with a similar age distribution. T(T0.1) was determined as followed T(T0.1) = P0.1/PImax . T(I)/T(TOT), where P0.1 is mouth occlusion pressure, PImax is maximal inspiratory pressure, and T(I)/T(TOT) is the duty cycle. CF children showed a significant decrease of their forced expiratory volume in 1 sec (FEV1), forced vital capacity (FCV), and FEV1/FVC, whereas the residual volume to total lung capacity ratio (RV/TLC) ratio and functional residual capacity (FRC) were significantly increased (P < 0.001). Children with CF showed mild malnutrition assessed by actual weight expressed by percentage of ideal weight for height, age, and gender (weight/height ratio; 82.3 +/- 3.6%). Children with CF showed a significant reduction in their PImax (69.3 +/- 4.2 vs. 93.8 +/- 7 cmH2O). We found a negative linear correlation between PImax and weight/height only in children with CF (r = 0.9, P < 0.001). During exercise, P(0.1), P0.1/PImax, and T(T0.1) were significantly higher, for a same percent maximal oxygen uptake in children with CF. On the contrary, T(I)/T(TOT) ratio was significantly lower in children with CF compared with healthy children. At maximal exercise, children with CF showed a T(T0.1) = 0.16 vs. 0.14 in healthy children (P < 0.001). We observed at maximal exercise that P0.1/PImax increased as FEV1/FVC decreased (r = -0.90, P < 0.001), and increased as RV/TLC increased (r = 0.92, P < 0.001) only in children with CF. Inversely, T(I)/T(TOT) decreased as FEV1/FVC decreased (r = 0.89, P < 0.001), and T(I)/T(TOT) decreased as RV/TLC increased (r = -0.94, P < 0.001). These results suggest that children with CF adopted a breathing strategy during exercise in limiting the increase of the duty cycle. Two determinants of this strategy were degrees of airway obstruction and hyperinflation.     

Pulmonary function test before and after operation of coronary artery by-pass surgery

Respiratory complications after successful CABG operation continuous to have on influence on the immediate recovery of a patient. It was reported that the mortality risk of the CABG patients increased, proportional to the reduction of pulmonary function tests (PFT). In the present study we aimed to investigate PFT values (vital capacity: VC, total lung capacity: TLC, residual volume: RV, functional residual capacity: FRC, force expiratory volume first second: FEV1, force mid expiratory flow: FEF25-75, duration force expiratory flow in vital capacity 25%: FEF25, duration force expiratory flow in vital capacity 50%: FEF50, duration force expiratory flow in vital capacity 75%: FEF75, peak expiratory flow: PEF, RV/TLC, FEF/FIF, FEV1/FVC) and arterial blood gases (pH, PaCO2, PaO2, SaO2) pre- and postoperatively which undergo CABG. The PFT and arterial blood gases values of 20 patients, age between 39-74 years, were measured that were undergo CABG operation before a week and three months after.The measured PFT values of 20 patients were recorded by system 2400 computerized and sensor medix 6200 and arterial blood gases analysed by radiometer ABL 300. The results were compared by the time and periods of before and after CABG operation, statistically evaluated the pearson's correlation and Student's t-test. In the results the postoperative PFT values were significantly decreased (p< 0.05, p< 0.001). But the RV, RV% and RV/TLC values were not changed significantly. In arterial blood gases values were not significantly changes. To avoid the postoperative complications we suggested that should be done the PFT and arterial blood gases measurement preoperatively.     

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.     

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.     

Exploring the relationship between forced maximal flow at functional residual capacity and parameters of forced expiration from raised lung volume in healthy infants

The raised volume rapid thoraco-abdominal compression technique (RVRTC) is being increasingly used to assess airway function in infants, but as yet no consensus exists regarding the equipment, methods, or analysis of recorded data. The aim of this study was to explore the relationship between maximal flow at functional residual capacity (V'(maxFRC)) and parameters derived from raised lung volumes, and to address analytical aspects of the latter technique in an attempt to assist with future standardization initiatives. Forced vital capacity (FVC) from lung volume raised to 3 kPa, timed forced expiratory volumes (FEV(t)), and forced expiratory flow parameters at different percentages of expired FVC (FEF(%)) were measured in 98 healthy infants (1-69 weeks of age). V'(maxFRC) using the tidal rapid thoraco-abdominal compression (RTC) technique was also measured. The within-subject relationships and within-subject variability of the various parameters were assessed.Duration of forced expiration was < 0.5 sec in 5 infants, meaning that FEV(0.3) and FEV(0.4) were the only timed volume parameters that could be calculated in all infants during the first months of life, and even when it could be calculated, FEV(0.5) approached FVC in many of these infants. It is recommended that FEV(0.4) be routinely reported in infants less than 3 months of age. Contrary to previous reports, within subject variability of V'(maxFRC) was less than that of FEF(75) (mean CV = 6.3% and 8.9%, respectively).A more standardized protocol when analyzing data from the RVRTC would facilitate comparisons of results between centers in the future.     

Kurtosis and skewness of density histograms on inspiratory and expiratory CT scans in smokers

The aim of this study is to evaluate the relationship between lung function and kurtosis or skewness of lung density histograms on computed tomography (CT) in smokers. Forty-six smokers (age range 46?81 years), enrolled in the Lung Tissue Research Consortium, underwent pulmonary function tests (PFT) and chest CT at full inspiration and full expiration. On both inspiratory and expiratory scans, kurtosis and skewness of the density histograms were automatically measured by open-source software. Correlations between CT measurements and lung function were evaluated by the linear regression analysis. Although no significant correlations were found between inspiratory kurtosis or skewness and PFT results, expiratory kurtosis significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV(1)%predicted, R = -0.581, p < 0.001; FEV(1)/FVC, R = -0.612, p < 0.001; RV/TLC, R = 0.613, p < 0.001, respectively). Similarly, expiratory skewness showed significant correlations with PFT results (FEV(1)%predicted, R = -0.584, p < 0.001; FEV(1)/FVC, R = -0.619, p < 0.001; RV/TLC, R = 0.585, p < 0.001, respectively). Also, the expiratory/inspiratory (E/I) ratios of kurtosis and skewness significantly correlated with FEV(1)%predicted (p < 0.001), FEV(1)/FVC (p < 0.001), RV/TLC (p < 0.001), and the percentage of predicted value of diffusing capacity for carbon monoxide (kurtosis E/I ratio, p = 0.001; skewness E/I ratio, p = 0.03, respectively). We conclude therefore that expiratory values and the E/I ratios of kurtosis and skewness of CT densitometry reflect airflow limitation and air-trapping. Higher kurtosis or skewness on expiratory CT scan indicates more severe conditions in smokers.     

Variability of the raised volume rapid thoracic compression technique in infants with recurrent wheezing

Measuring forced expiratory flows from raised lung volume in infants represents a significant advance in the assessment of pulmonary function early in life. However, variability in the main parameters obtained with raised volume rapid thoracic compression (RVRTC), FVC, FEV(0.5), FEF(50), FEF(75), and FEF(25-75), has not been completely evaluated. This study was performed to determine the intra-subject variability of spirometric-like parameters in infants with recurrent wheezing obtained with RVRTC. One hundred and two infants with recurrent wheezing (mean age 62 +/- 22 weeks) who were asymptomatic at the moment of measuring lung function participated in this study. For the variability analysis, three to five technically acceptable curves at flow-limitation jacket pressure were employed. The mean coefficient of variation (95 % CI) of spirometric parameters was as follows: FVC = 2.9 % (2.6-3.2); FEV(0.5) = 2.2 % (1.9-2.5); FEF(50) = 3.7 % (3.3-4.1); FEF(75) = 5.9 % (5.2-6.6) and FEF25-75 = 3.3 % (2.9-3.7). This study demonstrates the high reproducibility of the spirometric parameters measured with the technique of raised lung volume in infants.     

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.     

Longitudinal pulmonary status of cystic fibrosis children with meconium ileus

Although meconium ileus (MI) is the earliest manifestation of cystic fibrosis (CF), and is associated with poorer growth, the longitudinal pulmonary progression of CF children with MI is not clear. To test the hypothesis that MI is associated with worse pulmonary outcomes, we prospectively compared from diagnosis to 12 years of age 32 CF children with MI to 50 CF children without MI who were diagnosed during early infancy through neonatal screening. Pulmonary outcome measures included respiratory symptoms, respiratory infections, pathogens, antibiotic usage, hospitalizations, quantitative chest radiology, spirometry, and lung volume determinations. Obstructive lung disease was defined as percent predicted spirometry values below the lower limits of normal. Longitudinal analyses revealed no significant differences in cough, wheezing, respiratory infections, prevalence of and median times to acquisition of Pseudomonas aeruginosa or Staphylococcus aureus, antibiotic usage, and chest radiograph scores between the two groups. However, MI children showed significantly worse forced expiratory volume in 1 sec (FEV(1)), forced vital capacity (FVC), forced expiratory flow between 25-75% of FVC (FEF(25-75)), % predicted FEV(1), % predicted FEF(25-75), and total lung capacity (TLC). These differences were particularly apparent beginning at age 8-10 years. MI children also had higher rates of and shorter median times to obstructive lung disease. Subgroup analyses showed MI children treated surgically and those treated medically had similar pulmonary outcomes. In conclusion, MI children have worse lung function and more obstructive lung disease than those without MI. Such abnormalities are accompanied by reduced lung volume. MI is a distinct CF phenotype with more severe pulmonary dysfunction.     

Correlation between standing height,sitting height,and arm span as an index of pulmonary function in 6-10-year-old children

The present study evaluates the relationships of pulmonary volumes and flows and the anthropometric variables of standing height, sitting height, and arm span in 100 6-10-year-old children. To be included in the study, all children were required to be healthy and above the 3rd percentile of the curve of Tanner et al. (Arch Dis Child 1966;41:454-471; Arch Dis Child 1966;41:613-635) for height and weight. Standing height, sitting height, and arm span were measured according to standard protocol. The pulmonary function measurements were: tidal volume, minute respiratory volume, respiratory rate, expiratory reserve volume, inspiratory capacity, vital capacity, residual volume (RV), functional residual capacity, total lung capacity (TLC), forced vital capacity (FVC), forced expiratory volume in 1 sec of FVC (FEV(1)), forced expiratory flow measured between 25-75% of FVC, and FEV(1)/FVC and RV/TLC ratios. Simple linear regression best expressed the correlation between pulmonary function and the anthropometric variables. Significant correlations between anthropometric and pulmonary function measurements were observed, with FVC and FEV(1) showing the highest and RV the lowest r(2) values. There was a significant positive correlation between standing height and arm span according to linear regression and Bland-Altman comparison (Bland and Altman, Lancet 1968;8:307-310). Our results suggest that when an accurate determination of standing height cannot be obtained, arm span could be used interchangeably, using the same regression equation. However, for patients with limb deformities, regression equations of pulmonary function measurements in relation to sitting height may be a better choice for estimating pulmonary function.