Raised Volume Rapid Thoracic Compression Research Articles

Early follow-up of lung disease in infants with cystic fibrosis using the raised volume rapid thoracic compression technique and computed tomography during quiet breathing.

Among the different techniques used to monitor lung disease progression in infants with CF diagnosed by Newborn screening (NBS), raised volume-rapid thoracic compression (RVRTC) remains a promising tool. However, the need of sedation and positive pressure ventilation considerably limits its clinical use. We recently described a semi-quantitative method to evaluate air trapping by chest tomography during quite breathing without sedation (CTqb score). This parameter is the radiological sign of airway obstruction and could be also used for lung disease follow-up in infants with CF. However, its discriminative power compared with RVRTC and correlation with lung function parameters are not known. To compare the discriminative powers of the CTqb score and RVRTC parameters and to determine their correlation during the first year of life of infants with CF. In this multicenter longitudinal study, infants with CF diagnosed by NBS underwent RVRTC and CT during quite breathing at 10 ± 4 weeks (n = 30) and then at 13 ± 1 months of age (n = 28). All RVRTC parameters and the CTqb score remained stable between evaluations. The CTqb score showed a higher discriminative power than forced expiratory volume in 0.5 s (FEV0.5 ; the main RVRTC parameter) at both visits (66% and 50% of abnormal values vs 30% and 28%, respectively). No correlation was found between CTqb score and, the different RVRTC parameters or the plethysmographic functional residual capacity, indicating that they evaluate different aspect of CF lung disease.

Bronchodilator response in wheezing infants assessed by the raised volume rapid thoracic compression technique

BackgroundBronchodilator response (BDR) analyzed by the raised volume rapid thoracic compression (RVRTC) in wheezing infants is not yet well described, although bronchodilators (BD) are routine in the treatment of this population. ObjectiveTo evaluate BDR by RVRTC technique in infants with recurrent wheezing and compare to control group. MethodCross sectional study, 45 infants, age 56 weeks (38–67 weeks). Two groups: wheezing group (WG: history of recurrent wheezing) and control group (CG). RVRTC was evaluated, FVC, FEV0.5, FEF50, FEF75, FEF85, FEF25–75 were measured. Salbutamol was delivered to infants and RVRTC evaluated again. BDR was determined by the increase greater than two standard deviation from the mean change in the CG. ResultsIn WG (n = 32) lung function was worse than in CG (n = 13): FEV0.5: 0.0(−0.9–0.9z score) vs 0.8(0.2–1.4z score); FEF50: 0.2(−0.3–1.1z score) vs 0.9(0.5–1.4z score); and FEF25–75: 0.2(−0.5–1.1z score) vs 1.1(0.6–1.6z score), respectively, p < 0.05. Both groups had similar increase after BD. In WG 11 patients (34%) were responder and these had worse lung function compared to nonresponder (n = 21) (p < 0.05). The increase in lung function after BD in responder was higher than in nonresponder: FEV0.5: 6.5(2.1–7.1%) vs −0.5(−2.5–0.7%), FEF50: 5.1(2.7–11.7%) vs 0.4(−1.1–2.8%), FEF75: 20.7(4.7–23.6%) vs −1.3(−6.4–3.9%), FEF25–75: 9.9(3.8–16.4%) vs 0.0(−1.5–1.0%), respectively, p < 0.05. Conclusion34% WG showed BDR measured by the RVRTC. The best variables to detect BDR were FEF75, FEF25–75 and FEV0.5. Patients with worse lung function showed better response to BD.

Lung function over the first 3 years of life in children with congenital diaphragmatic hernia.

Infants with congenital diaphragmatic hernia (CDH) have variable degrees of pulmonary hypoplasia at birth. Few reports of lung function over the first years of life exist in this group of children. Pulmonary function abnormalities correlate with severity of neonatal disease and intensity of neonatal therapies needed. We also hypothesized that longitudinal measurements of lung function over the usual period of rapid lung growth would lend some insight into how the lung remodels in CDH infants. Ninety-eight infants with CDH between 11 days and 44 months of age underwent pulmonary function testing (PFT) on 1-5 occasions using the raised volume rapid thoracic compression technique. Demographic data were also collected. Forced expiratory flows were below normal. Total lung capacity was normal, but residual volume and functional residual capacity were elevated. Children requiring patch closure, ECMO, or pulmonary vasodilators generally had lower lung functions at follow up. Additionally, longer duration of mechanical ventilation correlated with worse lung function. Lung functions of survivors of CDH remain abnormal throughout the first 3 years of life. The degree of pulmonary function impairment correlated both with markers of the initial degree of pulmonary hypoplasia and the duration of mechanical ventilation. Understanding the relationship between the phenotypic presentation of CDH and the potential for subsequent lung growth could help refine both pre- and postnatal therapies to optimize lung growth in CDH infants.

Assessment of bronchodilator response in preschool children by pulmonary function tests

We performed pulmonary function test to document bronchodilator response by using tidal breathing flow volume loop (TBFVL), rapid thoracic compression (RTC), and raised volume rapid thoracic compression (RVRTC) techniques. Thirty-nine children (mean age 45.2 months) were evaluated. The parameters that showed significant improvement after bronchodilator administration included TEF10/ PTEF ratio in TBFVL, and FEF25-75%, FEV1 and PEF in RVRTC. None of the parameters measured in RTC showed significant improvement. We conclude FEV1, PEF and FEF 25-75% in RVRTC have greater sensitivity for detection of airways changes.

An Official American Thoracic Society Workshop Report: Optimal Lung Function Tests for Monitoring Cystic Fibrosis, Bronchopulmonary Dysplasia, and Recurrent Wheezing in Children Less Than 6 Years of Age

Although pulmonary function testing plays a key role in the diagnosis and management of chronic pulmonary conditions in children under 6 years of age, objective physiologic assessment is limited in the clinical care of infants and children less than 6 years old, due to the challenges of measuring lung function in this age range. Ongoing research in lung function testing in infants, toddlers, and preschoolers has resulted in techniques that show promise as safe, feasible, and potentially clinically useful tests. Official American Thoracic Society workshops were convened in 2009 and 2010 to review six lung function tests based on a comprehensive review of the literature (infant raised-volume rapid thoracic compression and plethysmography, preschool spirometry, specific airway resistance, forced oscillation, the interrupter technique, and multiple-breath washout). In these proceedings, the current state of the art for each of these tests is reviewed as it applies to the clinical management of infants and children under 6 years of age with cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheeze, using a standardized format that allows easy comparison between the measures. Although insufficient evidence exists to recommend incorporation of these tests into the routine diagnostic evaluation and clinical monitoring of infants and young children with cystic fibrosis, bronchopulmonary dysplasia, or recurrent wheeze, they may be valuable tools with which to address specific concerns, such as ongoing symptoms or monitoring response to treatment, and as outcome measures in clinical research studies.

Assessment of early pulmonary function abnormalities in giant omphalocele survivors

PurposeInfants with giant omphalocele (GO) are at increased risk for persistent respiratory insufficiency, yet information regarding the systematic assessment of their lung function is limited. We performed a group of pulmonary function tests (PFTs) including spirometry, fractional lung volume measurements, assessment of bronchodilator responsiveness, and passive respiratory mechanics in GO survivors during infancy and early childhood to evaluate the nature and degree of pulmonary dysfunction. Material and MethodsBetween July 2004 and June 2008, 30 consecutive GO survivors were enrolled in our interdisciplinary follow-up program. Forty-seven percent (14/30) underwent PFT during follow-up evaluation using the raised volume rapid thoracic compression technique to measure forced expiratory flows and bronchodilator responsiveness, body plethysmography to calculate lung volumes, and the single breath occlusion technique to measure passive mechanics of the respiratory system. ResultsThe mean age at PFT assessment was 19.3 ± 19.7 months (range, 1.0-58). Mean forced vital capacity and mean forced expiratory volume in the first 0.5 second were significantly reduced compared with published normative values (P = .03 and P < .01, respectively). Total lung capacity was significantly reduced (P < .001), whereas functional residual capacity, residual volume, and residual volume to total lung capacity ratio were within the normative range (P = .21, P = .34, and P = .48, respectively). Among the 46% who demonstrated significant bronchodilator responsiveness, there were greater increases in the mean percentage changes in flow at 25% to 75% (P = .01), flow at 75% (P < .001), and flow at 85% (P < .001) compared with those participants that did not respond. Specific compliance was reduced, whereas specific conductance increased, compared with published normal results. ConclusionsAbnormalities of pulmonary function in GO survivors include lung volume restriction without airway obstruction, an increased likelihood of airway hyperresponsivness, and reduced respiratory system specific compliance. Early recognition of pulmonary functional impairment in GO survivors could help to develop targeted treatment strategies to reduce the risk of subsequent pulmonary morbidity.

Lung function from infancy to preschool in a cohort of children with cystic fibrosis

This study aimed to describe lung function in a cohort of children with cystic fibrosis (CF) who underwent infant pulmonary function tests (IPFTs) and preschool spirometry. Children performed up to four IPFTs (raised volume rapid thoracic compression technique) over 1 yr and five preschool spirometry tests over up to 2 yrs during participation in prospective, multicentre studies of infant and preschool lung function. All lung function data were reviewed centrally for measurement acceptability. 45 children had 252 acceptable measurements (137 IPFTs and 115 preschool spirometries) at ages 0.3-6.5 yrs. The median number of measurements per participant was 6 (range 3-9). Recent Pseudomonas aeruginosa infection was associated with 5.1% (95% CI 0.01-9.9%) lower forced expiratory volume in 0.5 s (FEV(0.5)) and 16.4% (95% CI 7.0-24.9%) lower forced expiratory flow at 25-25% of forced vital capacity (FEF(25-75%)), after adjustment for length, test type and centre. Recent cough was associated with 5.7% (95% CI 1.1-10.1%) lower FEV(0.5) and 10.1% (95% CI 0.6-18.7%) lower FEF(25-75%). Even after accounting for infection status, cough, sex, length, test type and centre, there was significant inter-individual variability in lung function (p<0.01 for each of FEV(0.5), FEF(25-75%) and forced vital capacity). Recent P. aeruginosa infection and cough are associated with lower lung function in children with CF. Significant inter-individual variability in lung function remains to be explained.

Structure-Respiration Function Relationships Before and After Surgical Treatment of Early-onset Scoliosis

Spine and chest wall deformities in children with early onset scoliosis (EOS) frequently impair respiratory function and postnatal growth of the lung. While a relationship between deformity and such impairment has been reported in children with adolescent idiopathic scoliosis it is not well understood in children with early-onset scoliosis (EOS). We therefore describe (1) the preoperative relation between Cobb angle and forced vital capacity (FVC) in infants with EOS; (2) how changes in Cobb angle before and after surgery relate to changes in lung ventilation and perfusion in the right and left lungs. We measured FVC in 10 children with EOS<3years old using the raised volume rapid thoracic compression (RVRTC) technique and correlated them with Cobb angles. We then measured right lung contributions to total lung ventilation and perfusion using lung scans before and 4 to 57months after placement of vertical expandable prosthetic titanium ribs (VEPTRs) in 15 children with EOS and correlated changes in right lung function with postoperative changes in Cobb angles. In children 4 to 57months of age, preoperative FVC (mean value, 83%; range, 63%-109% of predicted values) did not correlate with Cobb angles (mean value, 56º; range, 14°-120º). In children 1.8 to 11.5years old, right lung ventilation and perfusion were abnormal in eight and seven children, respectively, but neither ventilation nor perfusion predictably normalized despite reductions in Cobb angle postoperatively. The data extend the age range of children with EOS whose Cobb angles correlate poorly with FVC preoperatively. The data are also consistent with reports that reduced Cobb angles after VEPTR insertion do not correlate with postoperative changes in respiratory function.

Exhaled nitric oxide, lung function, and exacerbations in wheezy infants and toddlers

There are limited data assessing the relationship between fraction of exhaled nitric oxide and lung function or exacerbations in infants with recurrent wheezing. In a longitudinal pilot study of children less than 2 years old, we assessed whether baseline fraction of exhaled nitric oxide was associated with lung function, bronchodilator responsiveness, changes in lung function, or subsequent exacerbations of wheezing. Forced expiratory flows and volumes using the raised-volume rapid thoracic compression method were measured in 44 infants and toddlers (mean age, 15.7 months) with recurrent wheezing. Single-breath exhaled nitric oxide (SB-eNO) was measured at 50 mL/s. Lung function was again measured 6 months after enrollment. At enrollment, forced expiratory volume in 0.5 seconds (FEV(0.5)), forced expiratory flow at 25% to 75% of expiration (FEF(25-75)), and forced expiratory flow at 75% of expiration (FEF(75)) z scores for the cohort were significantly less than zero. There was no correlation between enrollment SB-eNO levels and enrollment lung function measures. SB-eNO levels were higher in infants with bronchodilator responsiveness (46.1 vs 23.6 ppb, P < .001) and was associated with a decrease in FEV(0.5) (r = -0.54, P = .001), FEF(25-75) (r = -0.6, P < .001), and FEF(75) (r = -0.55, P = .001) over 6 months. A 10-ppb increase in SB-eNO level was associated with a 0.4-point z score decrease in FEV(0.5), a 0.4-point z score decrease in FEF(25-75), and a 0.42-point z score decrease in FEF(75). SB-eNO level was superior to lung function and bronchodilator responsiveness in predicting subsequent wheezing treated with systemic steroids. SB-eNO level might predict changes in lung function and risk of future wheezing and holds promise as a biomarker to predict asthma in wheezy infants and toddlers.

Effect of inhaled fluticasone on lung function in infants with recurrent wheezing: a randomised controlled trial

BackgroundInhaled corticosteroids are used to treat infants with troublesome asthma-like symptoms but their effect on the lung function of these young patients is controversial. Material and MethodsForty-four infants with recurrent wheezing (more than 3 episodes) and family history of asthma completed this randomised, parallel, double-blind, controlled trial to compare the effect on lung function (main endpoint) of once-daily inhaled fluticasone (375μg) versus placebo for 3 months. Pulmonary function was measured while infants were asymptomatic, using the raised volume rapid thoracic compression technique (spirometry-like), and values were converted to z-scores. ResultsThe fluticasone group showed a significant increase in forced flows, (p<0.001), a lower number of physician diagnosed wheezing episodes (p<0.002), and a significant decrease in the parent-reported number of wheezing episodes per month (p<0.03), as compared to placebo. One third of parents in the placebo group reported a clinical improvement in their infants. There was no significant difference in morning plasma cortisol between groups at entry or discharge. ConclusionsWe conclude that once-daily treatment with 375μg fluticasone increased forced flows and controlled symptoms in infants with recurrent wheezing without altering plasma cortisol levels. The spirometry-like technique is a useful tool to objectively assess the efficacy of anti-asthma medications in infants with repeated troublesome asthma-like symptoms.

Influence of sighs in the raised volume rapid thoracic compression technique (RVRTC) in infants

The raised volume rapid thoracic compression (RVRTC) technique has shown to be very promising in the evaluation of infant's lung function. In this technique lungs are inflated several times to a preset pressure prior to the thoracic compression. Many infants made a spontaneous inspiration (sigh) at the end of these inflations. Our hypothesis was that such sighs could change the major variables derived by this technique and the objective of this study was to evaluate the influence of these sighs during lung inflation in the RVRTC technique in infants. Pairs of maneuvers with and without sighs during lung inflation were obtained in 33 of 48 consecutive tests. Curves with sighs showed significantly higher values of FVC (median: 456 x 437 ml; P < 0.001) and FEV0.5 compared to those without, whereas FEF75 and FEF85 were significantly lower (median: 417 x 439 ml/sec, P = 0.008 and 251 x 273 ml/sec, P = 0.01; respectively). The mean percent change between maneuvers for FVC, FEV0.5, FEF75, and FEF85 was respectively: 6.4%, 3.8%, -3.1%, and -3.5%. These differences represent a mean change of 0.38 z score for FVC and of 0.12 z score for FEF75 and FEF85. In conclusion, the presence of sighs during lung inflation significantly changes RVRTC values in infants. We suggest that the presence or the absence of sighs should be registered for each maneuver and that it should be considered for within and between subject comparisons.

Growth Rate of Lung Function in Healthy Preterm Infants

It remains unclear whether premature birth, in the absence of neonatal respiratory disease, results in abnormal growth and development of the lung. We previously reported that a group of healthy infants born at 32-34 weeks' gestation and without respiratory complications had decreased forced expiratory flows and normal forced vital capacities at 2 months of age. Our current study evaluated whether these healthy infants born prematurely exhibited improvement or "catch-up" in their lung function during the second year of life. Longitudinal measurements of forced expiratory flows by the raised volume rapid thoracic compression technique were obtained in the first and the second years of life for infants born prematurely at 32.7 (range, 30-34) weeks' gestation (n = 26) and infants born at full term (n = 24). Healthy infants born prematurely demonstrate decreased forced expiratory flows and normal forced vital capacities in the first and second years of life. In addition, the increases in lung function with growth were similar to full-term infants. Persistently reduced flows in the presence of normal forced vital capacity and the absence of catch-up growth in airway function suggest that premature birth is associated with altered lung development.

Reduced Lung Function in Healthy Preterm Infants in the First Months of Life

Preterm delivery has been associated with a higher incidence of respiratory morbidity even in infants that do not have significant respiratory disease during the neonatal period. Reduced flows have been reported in children and adolescents born prematurely. The aim of this study was to assess lung function in healthy preterm infants in the first months of life. Preterm infants with less than 48 h of supplemental oxygen were recruited. Lung function was assessed by the raised-volume rapid thoracic compression in the first months of life. The control group consisted of full-term infants without a history of respiratory diseases. Sixty-two preterm (29 male) and 27 full-term (10 male) infants were tested. Adjusting for length, age, and sex, we found a mean significant reduction of 92 ml/s (22%) in FEF(50), 73 ml/s (21%) in FEF(25-75), and 19 ml (28%) in FEV(0.5) in the preterm group. These differences in expiratory flows remained significant using another model that adjusts for lung volume (p < 0.01 for FEF(50), FEF(25-75), and FEV(0.5), and p < 0.05 for FEF(75)). In the preterm group, after adjusting for length, male sex, lower gestational age, and increased weight were significantly and independently associated with reduced flows. Our findings confirm that prematurity is independently associated with reduced lung function and that this is detectable in the first months of life. Male sex, lower gestational age, and weight are important predictors for reduced expiratory flows in this group.

The effect of montelukast on lung function and exhaled nitric oxide in infants with early childhood asthma

Effective treatment of respiratory symptoms, airway inflammation and impairment of lung function is the goal of any asthma therapy. Although montelukast has been shown to be a possible add-on therapy for anti-inflammatory treatment in older children, its efficacy in infants and young children is not well known. The aim of this study was to investigate its effect in infants and young children with early childhood asthma. In a prospective randomised double-blind placebo-controlled study, 24 young children (10-26 months) with wheeze, allergy and a positive family history of asthma consistent with the diagnosis of early childhood asthma were randomised to receive montelukast 4 mg or placebo. The forced expiratory volume in 0.5 seconds (FEV0.5) was measured using the raised volume rapid thoracic compression technique, and fractional exhaled nitric oxide (FeNO) and symptom scores were determined. No change was noted in FEV0.5, FeNO or symptom score in the placebo group following the treatment period. In contrast, significant improvements in mean+/-SD FEV0.5 (189.0+/-37.8 and 214.4+/-44.9 mL before and after treatment, respectively), FeNO (29.8+/-10.0 and 19.0+/-8.5 ppb) and median symptom score (5.5 and 1.5) were noted following treatment with montelukast. In conclusion, montelukast has a positive effect on lung function, airway inflammation and symptom scores in very young children with early childhood asthma.

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 FEF 25-75 = 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.

Parental Smoking and Airway Reactivity in Healthy Infants

Parental tobacco smoking is associated with lower airway function and an increased incidence of wheezy respiratory illnesses in infants. We evaluated in 76 healthy infants whether exposure to parental tobacco smoking was associated with airway hyperreactivity, which could contribute to lower airway function and the increased wheezy illnesses. Airway function was measured using the raised-volume rapid thoracic compression technique, and airway reactivity was assessed by methacholine challenge (0.015-10 mg/ml), which was stopped for a more than 30% decrease in forced expiratory flow (FEF)(75) or the final dose with a less than 30% decrease. Parental tobacco smoking was associated with lower baseline airway function (FEF(50), 600 vs. 676 ml/second, p < 0.04; FEF(25-75), 531 vs. 597 ml/second, p < 0.05). Infants exposed to tobacco smoking were approximately half as likely to develop a more than 30% decline in FEF(75) at any given methacholine dose (hazard ratio = 0.4, p = 0.001). In addition, a history of asthma in an extended family member increased the likelihood that an infant would develop a more than 30% decline in FEF(75) (hazard ratio = 1.7, p = 0.04). We conclude that exposure to parental smoking is associated with lower airway function but not increased airway reactivity; however, family history of asthma is associated with heightened airway reactivity.

Measurement of Forced Expiratory Flows and Lung Volumes

After completing this article, readers should be able to: 1. Describe the information that measurements of forced expiratory flow can provide in spontaneously breathing and mechanically ventilated infants. 2. Delineate how lung volume can be measured. The measurements of forced expiratory flows and lung volumes are important to the evaluation of patients who have respiratory symptoms. Until recently, measurements have been restricted to adults and children old enough to cooperate with testing maneuvers. Newer techniques have enabled such measurements to be made in infants and led to improved understanding of normal lung and airway growth during infancy and early childhood, when dramatic changes occur. The measurements have had important clinical uses in the evaluation and treatment of infants who have respiratory disease, but their use has been limited because they require specialized equipment and expertise as well as sedation of the infant. In this article, we discuss the techniques required for measurement of forced expiratory flows and lung volumes, their limitations, and applications in clinical practice. Detection of airflow obstruction, by physical examination or by quantitative measurement techniques, is facilitated by increasing expiratory flow rates. Measurement of forced expiratory flows is useful because flow rates are inversely proportional to the fourth power of the radius of the airway and, therefore, are indicative of airway size when flow is limited. Disease states affecting the airways, including asthma, bronchopulmonary dysplasia (BPD), or congenital lesions such as pulmonary hypoplasia or vascular airway compression, are expected to decrease expiratory flow. Infants typically are sedated for testing to maintain relaxed breathing with a face mask placed over the mouth and nose. This sedation often is perceived by parents and physicians as one of the barriers to such testing. (1) However, sedation can be achieved safely using oral chloral hydrate at a dose of 80 to 100 mg/kg. …

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 v̇_maxFRC) 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 v̇_maxFRC by the tidal volume rapid thoracic compression technique (TVRTC). Results: Mean FEV_t but not mean v̇_maxFRC were significantly lower at visit 2 compared to visit 3 (FEV_0.5: p = 0.005, and FEV_0.75: p = 0.002; v̇_maxFRC: 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 v̇_maxFRC 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.

Methacholine responsiveness in infants assessed with low frequency forced oscillation and forced expiration techniques

BACKGROUNDThe contribution of the pulmonary tissues to the mechanical behaviour of the respiratory system is well recognised. This study was undertaken to detect airway and lung tissue responses to inhaled...

Airway and respiratory tissue mechanics in normal infants.

Low-frequency respiratory impedance (Zrs) was measured by applying a forcing signal, between 0.5 and 21 Hz at a transrespiratory pressure of 20 cm H(2)O, in a cross-sectional study of 37 normal infants. A model containing an airway resistance (Raw) and inertance (Iaw) and a tissue damping (G) and elastance (H) was fitted to the individual Zrs. Forced expiratory volume in 0.5 second (FEV(0.5)) was determined using the raised volume rapid thoracic compression technique. Multivariate regression analysis was used to analyze the relationships between the lung function parameters and length. Both airway and tissue parameters showed a decreasing quadratic relationship with increasing length. FEV(0.5) showed an increasing cubic relationship with length. A family history of asthma was found to have a negative effect on Raw, H, and FEV(0.5).