Mean Functional Residual Capacity Research Articles

Perioperative Improvement in Pulmonary Function in Infants with Congenital Diaphragmatic Hernia.

The objective of this study was to compare serial changes in pulmonary function in contemporary infants with congenital diaphragmatic hernia managed with a gentle ventilation approach. Observational cohort, single-center study of infants ≥350/7weeks gestation at delivery with congenital diaphragmatic hernia. Functional residual capacity (FRC), passive respiratory compliance, and passive respiratory resistance were measured presurgical and postsurgical repair and within 2weeks of discharge. A 1-way analysis of variance for repeated measures was used to evaluate the change in FRC, passive respiratory compliance, and passive respiratory resistance over these repeated measures. Twenty-eight infants were included in the analysis with a mean gestational age of 38.3weeks and birth weight of 3139g. We found a significant increase in FRC across the 3 time points (mean in mL/kg [SD]: 10.9 [3.6] to 18.5 [5.2] to 24.2 [4.4]; P<.0001). There was also a significant increase in passive respiratory compliance and decrease in passive respiratory resistance. In contrast to a previous report, there were survivors in the current cohort with a preoperative FRC of <9mL/kg. The mean FRC measured at discharge was in the range considered within normal limits. Sixteen infants had prenatal measurements of the lung-to-head ratio, but there was no relationship between the lung-to-head ratio and preoperative or postoperative FRC measurements. Infants with congenital diaphragmatic hernia demonstrate significant increases in FRC and improvements in respiratory mechanics measured preoperatively and postoperatively and at discharge. We speculate these improvements are due to the surgical resolution of the mechanical obstruction to lung recruitment and that after achieving preoperative stability, repair should not be delayed given these demonstrable postoperative improvements.

Longitudinal changes in lung function in very prematurely born young people receiving high-frequency oscillation or conventional ventilation from birth.

ObjectiveTo examine changes in lung function over time in extremely prematurely born adolescents.Working HypothesisChanges in lung function during adolescence would vary by ventilation mode immediately after birth.Study DesignLongitudinal follow‐up study.Patient Subject SelectionParticipants from the United Kingdom Oscillation Study who were randomized at birth to high‐frequency oscillation (HFO) or conventional ventilation (CV) were assessed at 11–14 years (n = 319) and at 16–19 years (n = 159).MethodologyForced expiratory flow (FEF), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and lung volumes including functional residual capacity (FRC) were reported as z‐scores. The diffusion capacity of the lungs for carbon monoxide (DLCO) was measured. Lung function trajectories were compared by mode of ventilation using mixed models. Changes in z‐scores were scaled to 5‐year average follow‐up.ResultsThere were significant changes in the mean FEF75, FEF50, FEF25, FEV1, FVC, and DLCO z‐scores within the CV and HFO cohorts, but no significant differences in the changes between the two groups. The mean FRC z‐score increased in both groups, with an average change of greater than one z‐score. The mean FEV1/FVC z‐score increased significantly in the CV group, but not in the HFO group (difference in slopes: p = 0.02). Across the population, deterioration in lung function was associated with male sex, white ethnicity, lower gestational age at birth, postnatal corticosteroids, oxygen dependency at 36 weeks postmenstrual age, and lower birth weight, but not ventilation mode.ConclusionsThere was little evidence that the mode of ventilation affected changes in lung function over time.

Contemporary N2 and SF6 multiple breath washout in infants and toddlers with cystic fibrosis.

Multiple breath washout (MBW) is used for early detection of cystic fibrosis (CF) lung disease, with SF6 MBW commonly viewed as the reference method. The use of N2 MBW in infants and toddlers has been questioned for technical and physiological reasons, but a new correction of the N2 signal has minimized the technical part. The present study aimed to assess the remaining differences and the contributing mechanisms for the differences between SF6 and N2 MBW,corrected-such as tidal volume reduction during N2 washout with pure O2 . This was a longitudinal multicenter cohort study. SF6 MBW and N2 MBW were performed prospectively at three CF centers in the same visits on 154 test occasions across 62 children with CF (mean age: 22.7 months). Offline analysis using identical algorithms to the commercially available program provided outcomes of N2,original and N2,corrected for comparison with SF6 MBW. Mean functional residual capacity, FRCN2,corrected was 14.3% lower than FRCN2, original , and 1.0% different from FRCSF6 . Lung clearance index, LCIN2,corrected was 25.2% lower than LCIN2,original , and 7.3% higher than LCISF6 . Mean (SD) tidal volume decreased significantly during N2 MBWcorrected , compared to SF6 MBW (-13.1 ml [-30.7; 4.6], p < 0.0001, equal to -12.0% [-25.7; 1.73]), but this tidal volume reduction did not correlate to the differences between LCIN2,corrected and LCISF6 . The absolute differences in LCI increased significantly with higher LCISF6 (0.63/LCISF6 ) and (0.23/LCISF6 ), respectively, for N2,original and N2,corrected , but the relative differences were stable across disease severity for N2,corrected , but not for N2,original . Only minor residual differences between FRCN2,corrected and FRCSF6 remained to show that the two methods measure gas volumes very similar in this age range. Small differences in LCI were found. Tidal volume reduction during N2 MBW did not affect differences. The corrected N2 MBW can now be used with confidence in young children with CF, although not interchangeably with SF6 .

Lifestyle modification for weight loss: Effects on cardiorespiratory capacity in patients with class II and class III obesity.

BackgroundThe prevalence of obesity has increased worldwide. Obesity affects the lungs and airways, limits peak oxygen uptake, and hampers physical performance; however, objective data are scarce. Does lifestyle modification for weight loss (LM) have an impact on cardiorespiratory capacity (CRC) in patients with class II and class III obesity?MethodThis was a single‐center prospective 2‐year follow‐up pilot study. Four separated stays in the inpatient specialized medical center Muritunet with an integrated approach to LM, including an individual plan on diet and physical activity (PA) goals. Furthermore, it included lectures and counseling on human anatomy and physiology, nutrition, physical exercise, and motivation, as well as daily PA. Cardiopulmonary and blood chemistry tests were conducted.ResultsSeventy‐seven participants were included; however, 47% (n = 36) dropped out during follow‐up. Forty‐one participants completed the study. At baseline (BL), the mean age was 45.4 (SD 10.2, range 23–62) years, with a mean body mass index (BMI) of 41.3 (SD 5.4) kg/m2, and 85% (n = 35) had one or more comorbidities, such as obstructive pulmonary disease (n = 15, 37%), obstructive sleep apnea (n = 19, 46%), type 2 diabetes (n = 20, 49%), and hypertension (n = 17, 41%). The mean functional residual capacity increased, significantly the second year (p = 0,037). CRC increased significantly the first year (p = 0.032). Weight and BMI declined, reaching statistical significance at 2 years for both males and females (p = 0.033 and p = 0.003, respectively). At BL, the participants reported lower health‐related quality of life compared to the general Norwegian population. Across time the physical component summary score (quality of life) for both males and females (p = 0.011 and p = 0.049, respectively) increased significantly.ConclusionLifestyle modification for weight loss improves CRC in patients with class II and class III obesity.

Hyperinflation is associated with increased respiratory rate and is a more sensitive measure of cystic fibrosis lung disease during infancy compared to forced expiratory measures.

The goal of this study was to identify clinical features associated with abnormal infant pulmonary function tests (iPFTs), specifically functional residual capacity (FRC), in infants with cystic fibrosis (CF) diagnosed via newborn screen (NBS). We hypothesized that poor nutritional status in the first 6-12 months would be associated with increased FRC at 12-24 months. This study utilized a combination of retrospectively and prospectively collected data from ongoing research studies and iPFTs performed for clinical indications. Demographic and clinical features were obtained from the electronic medical record. Forced expiratory flows and volumes were obtained using the raised volume rapid thoracoabdominal technique (RVRTC) and FRC was measured via plethysmography. A total of 45 CF NBS infants had iPFTs performed between 12 and 24 months. Mean forced vital capacity, forced expiratory volume in 0.5 s, and forced expiratory flows were all within normal limits. In contrast, the mean FRC z-score was 2.18 (95% confidence interval [CI] = 1.48, 2.88) and the mean respiratory rate (RR) z-score was 1.42 (95% CI = 0.95, 1.89). There was no significant association between poor nutritional status and abnormal lung function. However, there was a significant association between higher RR and increased FRC, and a RR cutoff of 36 breaths/min resulted in 92% sensitivity to detect hyperinflation with 32% specificity. These results suggest that FRC is a more sensitive measure of early CF lung disease than RVRTC measurements and that RR may be a simple, noninvasive clinical marker to identify CF NBS infants with hyperinflation.

Dramatic impact of morbid obesity on child lung development

ObjectiveTo assess the respiratory function and sleep characteristics of obese adults and children. MethodsAll patients with non-syndromic, severe obesity (BMI ≥3 z-scores for children and ≥40.00kg/m2 for adults), referred for pulmonary function tests at Lille University Hospital, were retrospectively included. ResultsA total of 69 children (mean±SD BMI 36.8±6.7 and mean BMI z-score 4.7±1.0) and 70 adults were included (mean BMI 45.7±6.2). Metabolic syndrome was diagnosed in 13 children (26%) and 40 adults (80%). Reduced lung volumes were observed in 34 children (50.0%) and 16 adults (24.0%) and both the mean functional residual capacity (FRC) and the mean residual volume (RV) were lower in children than in adults (FRC: −1.7±2.1 z-score in children vs. −1.0±1.1 in adults, P=0.026; and RV: −0.8±1.2 z-score in children vs. −0.1±1.1 in adults, P=0.002). The prevalence of severe obstructive sleep apnea syndrome was greater in adults (40.7% vs. 18.8%, P=0.007). Children had a higher average oxygen saturation (median of 96.0% [91.0–98.0] vs. 93.0% [76.0–97.0] in adults, P<0.0001). ConclusionObesity has consequences for lung volumes in children; however, a longitudinal study is needed to determine the impact on pulmonary expansion and growth.

Feasibility and challenges of using multiple breath washout in COPD.

BackgroundLung clearance index (LCI), derived from multiple-breath washout (MBW), is a well-established assessment of ventilation inhomogeneity in cystic fibrosis but has not been widely applied in other conditions characterized by heterogeneous airways disease, such as COPD. The aim of this study was to evaluate the sensitivity, repeatability, and practicality of LCI in patients with COPD.MethodsFifty-four COPD patients completed MBW using nitrogen as the washout tracer gas (MBWN2, measured using an Exhalyzer™ device), spirometry, and plethysmography. Twenty patients repeated MBWN2, MBWSF6 (using a separate Innocor™ gas analyzer to measure washout of the exogenous trace sulphur hexafluoride), and spirometry at a second visit ≥24 hours later.ResultsMean (SD) COPD LCI measured by nitrogen washout (LCIN2) was 12.1 (2.2); mean (SD) LCI Z-score 5.8 (2.0). LCIN2 increased across Global Initiative for Obstructive Lung Disease stages 1 to 3 and was abnormal (Z-score >1.65) in all COPD patients, including those with forced expiratory volume in 1 second (FEV1) ≥80% predicted. LCI was repeatable (median intra-test coefficient of variation 4.1%) and reproducible (limits of agreement −1.8 to 1.6) after mean of 16 days. Functional residual capacity (FRC) measurements were significantly greater using nitrogen than SF6 or plethysmography: mean FRC measured by nitrogen washout (FRCN2) 139% predicted versus FRC measured by plethysmography 125% predicted, p<0.0001.ConclusionLCI is most suitable as a measure of early airways disease in COPD in those with well-preserved FEV1, with similar repeatability and limitations to that observed in cystic fibrosis. Using the Exhalyzer system to perform MBWN2, however, appeared to substantially over-read FRC. This discrepancy needs addressing before FRCN2 measurements made using this device can be reliably deployed.

Effectiveness of pulmonary rehabilitation on pulmonary function parameters and dyspnea in patients with stable chronic obstructive pulmonary disease

BackgroundChronic obstructive pulmonary disease (COPD) is a common preventable and treatable disease characterized by persistent airflow limitation that is usually progressive. The characteristic symptoms of COPD are chronic and progressive dyspnea, cough, and sputum production. Breathing exercises aim to reduce hyperinflation, improve respiratory muscle performance, and reduce dyspnea.AimThe aim of the study was to assess the effectiveness of breathing exercises among patients with stable COPD in improvement of pulmonary function parameters, 6-min walk distance, and dyspnea score.Patients and methodsRandomized controlled design was used in this study. Patients recruited for this study were enrolled from the outpatient clinic of Department of Chest Diseases and Tuberculosis. Overall, 15 patients with stable COPD were enrolled in pulmonary rehabilitation group and underwent breathing exercises for 12 weeks. Moreover, 15 patients were enrolled in the control group. Statistical package for the social sciences (SPSS version 20) software was used for statistical analysis.ResultsIn the breathing exercise group, there was a significant increase in the mean forced expiratory volume in first second (P=0.001), forced vital capacity (P=0.001), and inspiratory capacity (P=0.015). There was a significant decrease in the mean functional residual capacity (P=0.005), residual volume (P=0.001), and total lung capacity (P=0.001). There was no significant difference between the values of the previous parameters in the control group.ConclusionIn stable COPD, breathing exercises improved pulmonary function parameters, 6-min walk distance, and dyspnea score.

Effect of position and positive pressure ventilation on functional residual capacity in morbidly obese patients: a randomized trial.

In morbidly obese patients, the position and ventilation strategy used during pre-oxygenation influence the safe non-hypoxic apnea time and the functional residual capacity (FRC). In awake morbidly obese volunteers, we hypothesized that the FRC would be higher after a five-minute period of positive pressure ventilation compared with spontaneous ventilation at zero inspiratory pressure. Using a prospective crossover randomized trial design, obese subjects underwent, in a randomized order, a combination of one of three positions, supine (S), beach chair (BC), and reverse Trendelenburg (RT), and one of two ventilation strategies, spontaneous ventilation at zero inspiratory pressure (ZEEP-SV) or with positive pressure (PP-SV) set to an inspiratory pressure of 8 cmH2O, positive end-expiratory pressure of 10 cmH2O, and fraction of inspired oxygen of 0.21. Seventeen obese volunteers with a mean (standard deviation; SD) body mass index of 50 (8) kg·m-2 were included. Mean (SD) FRC in the three positions (S, BC, RT) was significantly higher using PP-SV compared with ZEEP-SV [2571 (477) vs 2215 (481) mL, respectively; mean difference, 356; 95% confidence interval (CI), 209 to 502; P < 0.001]. Mean (SD) FRC was significantly higher in the RT compared with BC position [2483 (521) vs 2338 (469) mL, respectively; mean difference, 145; 95% CI, 31 to 404; P = 0.01], while there was no difference between S and BC [2359 (519) mL vs 2338 (469) mL, respectively; mean difference, 21; 95% CI, -93 to 135; P = 0.89]. In awake morbidly obese volunteers, an increase in the FRC is observed when spontaneous ventilation at zero inspiratory pressure is switched to positive pressure. Compared with S positioning, the BC position had no measurable impact on the FRC. The RT position resulted in an optimal FRC. clinicaltrials.gov (NCT02121808). Registered 24 April 2014.

The effect of inert gas choice on multiple breath washout in healthy infants: differences in lung function outcomes and breathing pattern.

The detrimental effects on breathing pattern during multiple breath inert gas washout (MBW) have been described with different inhaled gases [100% oxygen (O2) and sulfur hexafluoride (SF6)] but detailed comparisons are lacking. N2- and SF6-based tests were performed during spontaneous quiet sleep in 10 healthy infants aged 0.7-1.3 yr using identical hardware. Differences in breathing pattern pre and post 100% O2 and 4% SF6 exposure were investigated, and the results obtained were compared [functional residual capacity (FRC) and lung clearance index (LCI)]. During 100% O2 exposure. mean inspiratory flow ("respiratory drive") decreased transiently by mean (SD) 28 (9)% ( P < 0.001), and end-tidal CO2 (carbon dioxide) increased by mean (SD) 0.3 (0.4)% units ( P < 0.05) vs. air breathing prephase. During subsequent N2 washin (i.e., recovery phase), the pattern of change reversed. No significant effect on breathing pattern was observed during SF6 testing. In vitro testing confirmed that technical artifacts did not explain these changes. Mean (SD) FRC and LCI in vivo were significantly higher with N2 vs. SF6 washout: 216 (33) vs. 186 (22) ml ( P < 0.001) and 8.25 (0.85) vs. 7.55 (0.57) turnovers ( P = 0.021). Based on these results, SF6 based MBW is the preferred methodology for tests in this age range. NEW & NOTEWORTHY Inert gas choice for multiple breath inert gas washout (MBW) in infants has important consequences on both breathing pattern during test performance and the functional residual capacity and lung clearance index values obtained. Data suggest the detrimental effect of breathing pattern of 100% O2 and movement of O2 across the alveolar capillary membrane, with direct effects on MBW outcomes. SF6 MBW during infancy avoids this and can be further optimized by addressing the sources of technical artifact identified in this work.

Pulmonary function and outcomes in infants randomized to a rescue course of antenatal steroids

Our objective was to obtain follow-up pulmonary function testing and assessment of clinical respiratory outcomes, at 1-2 years, in preterm infants whose mothers were randomized to a single rescue course of antenatal steroids (AS) versus placebo. Follow-up of a randomized, double-blinded trial. In the original trial pregnant women ≥14 days after initial course of AS were randomized to rescue AS or placebo. Pulmonary function testing and a standardized respiratory questionnaire were obtained at 1-2 years of corrected age. Respiratory compliance (Crs) was measured with the single-breath occlusion and functional residual capacity (FRC) with the nitrogen washout method. Analysis was by intention-to-treat. A total of 96 (87%) of available survivors were administered a respiratory questionnaire. Seventy-seven percent of available patients had pulmonary function testing performed. There was no significant difference between groups in incidence of wheezing, asthma, respiratory syncytial virus infection, respiratory readmissions, use of bronchodilators or other medications, or in measurements of pulmonary function. There was also no significant difference in corrected age at study, race, gender, or length at the time of pulmonary function testing. Infants in the rescue group had a comparable mean FRC (249.4 mL vs 246.2 mL; adjusted 95%CI for difference -15.45, 38.20; P = 0.37) versus placebo. There were no differences in tidal volume or Crs. A rescue course of AS significantly increases Crs within 72 h of age and decreases oxygen need in newborn infants, without an adverse impact on pulmonary function or clinical respiratory outcomes at 1-2 years of age [NCT00669383].

EPS04.2 Infant lung function: First report of a novel infant multiple breath washout apparatus

Objectives The value of lung clearance index (LCI) is well recognised in children and adults and has also been shown to be elevated in infants with CF. At present, there are considerable technical challenges in measuring LCI in infants. There is no simple method of assessing lung function in this population. The Innocor photoacoustic gas analyser measures very low concentrations of the inert tracer gas SF6. This has been developed into a novel mixed open–closed circuit system: expired gas is collected during washout to measure Functional Residual Capacity (FRC) and cumulative expired volume. This permits a low deadspace and ability to perform at rapid ventilation rates. Methods A prototype system was assessed using a lung model based on a mechanically driven 100 ml syringe and ventilation tank. The model delivered FRC's of 100–250 ml, with corresponding tidal volumes of 30–90 ml and respiratory rates of 20–40 min −1 . Improvements to hardware and washin protocol were made following initial testing. Results Following modification, overall mean error of FRC measurement was 0.04%. Actual mean FRC (ml) are shown in Table 1. Of 21 repeats, only 1 measurement was outside ±5% error range for FRC. Table 1Model FRC a (ml)Measured FRC (95% CI) (ml)Mean (SD) % error10299.2 (97.0–101.5)−1.76 (1.8)202203.3 (199.4–207.3)1.17 (2.34)252250.6 (247.4–253.8)−0.18 (1.63)aIncludes deadspace. Conclusion This system is capable of highly accurate measurement of FRC at volumes down to 100 ml in a realistic infant lung simulation. Accuracy is superior to previously described systems at higher FRC, and within the targets set by guidelines. In vivo testing is due to commence in 2015.

Sustained inflation at birth did not protect preterm fetal sheep from lung injury

Sustained lung inflations (SI) at birth may recruit functional residual capacity (FRC). Clinically, SI increase oxygenation and decrease need for intubation in preterm infants. We tested whether a SI to recruit FRC would decrease lung injury from subsequent ventilation of fetal, preterm lambs. The preterm fetus (128±1 day gestation) was exteriorized from the uterus, a tracheostomy was performed, and fetal lung fluid was removed. While maintaining placental circulation, fetuses were randomized to one of four 15-min interventions: 1) positive end-expiratory pressure (PEEP) 8 cmH2O (n=4), 2) 20 s SI to 50 cmH2O then PEEP 8 cmH2O (n=10), 3) mechanical ventilation at tidal volume (VT) 7 ml/kg (n=13), or 4) 20 s SI then ventilation at VT 7 ml/kg (n=13). Lambs were ventilated with 95% N2/5% CO2 and PEEP 8 cmH2O. Volume recruitment was measured during SI, and fetal tissues were collected after an additional 30 min on placental support. SI achieved a mean FRC recruitment of 15 ml/kg (range 8-27). Fifty percent of final FRC was achieved by 2 s, 65% by 5 s, and 90% by 15 s, demonstrating prolonged SI times are needed to recruit FRC. SI alone released acute-phase proteins into the fetal lung fluid and increased mRNA expression of proinflammatory cytokines and acute-phase response genes in the lung. Mechanical ventilation further increased all markers of lung injury. SI before ventilation, regardless of the volume of FRC recruited, did not alter the acute-phase and proinflammatory responses to mechanical ventilation at birth.

Experimental intra-abdominal hypertension attenuates the benefit of positive end-expiratory pressure in ventilating effusion-compressed lungs*

To test the ability of positive end-expiratory pressure to offset the reduction of resting lung volume caused by intra abdominal hypertension, unilateral pleural effusion, and their combination. : Controlled application of intrapleural fluid, raised abdominal pressure and their combination before and after positive end-expiratory pressure in an anesthetized porcine model of controlled ventilation. Large animal laboratory of a university-affiliated hospital. Fourteen deeply anesthetized swine (weight 30-35 kg). Unilateral pleural effusion instillation (13 mL/kg), intra-abdominal hypertension (15 mm Hg), and simultaneous pleural effusion/intra abdominal hypertension. Tidal compliance, end-expiratory lung aeration by gas dilution functional residual capacity, and quantitative analyses of computerized tomograms of the lungs at the extremes of the tidal cycle. Positive end-expiratory pressure of 10 cm H2O (positive end-expiratory pressure 10) increased mean functional residual capacity by 368 mL when pleural effusion was present and by 184 mL when intra-abdominal hypertension was present. When pleural effusion and intra-abdominal hypertension were simultaneously applied, positive end-expiratory pressure 10 failed to improve tidal compliance and increased functional residual capacity by only 77 mL, whereastidal recruitment during ventilation remained substantial. The presence of intra-abdominal hypertension negates most of the positive end-expiratory pressure 10 benefit in reversing pleural effusion-induced de-recruitment. Relief of intra-abdominal hypertension may be instrumental to the treatment of pleural effusion-associated lung restriction and cyclical tidal collapse and reopening.

Prospective longitudinal evaluation of lung function during the first year of life after repair of congenital diaphragmatic hernia

To evaluate lung function and respiratory morbidity prospectively during the first year of life in patients with congenital diaphragmatic hernia and to study the effect of extracorporeal membrane oxygenation therapy. Prospective longitudinal cohort study. Outpatient clinic of a tertiary-level pediatric hospital. The cohort of 43 infants included 12 patients treated with extracorporeal membrane oxygenation. Evaluation was at 6 and 12 months; 33 infants were evaluated at both time points. None. Maximal expiratory flow at functional residual capacity and functional residual capacity were measured with Masterscreen Babybody. Z-scores were calculated for maximal expiratory flow at functional residual capacity. Mean maximal expiratory flow at functional residual capacity values at 6 and 12 months were significantly below the expected values (mean z-score -1.4 and -1.5, respectively) without a significant change between both time points. Values did not significantly differ between extracorporeal membrane oxygenation and nonextracorporeal membrane oxygenation-treated patients. Functional residual capacity values were generally high, 47% were above the suggested normal range, and did not change significantly over time. Mean functional residual capacity values in extracorporeal membrane oxygenation-treated patients were significantly higher than in nonextracorporeal membrane oxygenation-treated patients (p = .006). The difference (5.1 mL/kg ± 1.8 SE) did not change significantly between the two time points. Higher mean airway pressure and longer duration of ventilation were associated with higher functional residual capacity. None of the perinatal characteristics was associated with maximal expiratory flow at functional residual capacity. Mean weight z-scores were significantly below zero at both time points (p < .001). Mean weight z-score in extracorporeal membrane oxygenation-treated patients were lower than in nonextracorporeal membrane oxygenation-treated patients (p = .046). Infants with congenital diaphragmatic hernia have decreased expiratory flows and increased functional residual capacity within the first year of life. Extracorporeal membrane oxygenation-treated patients with congenital diaphragmatic hernia may have more respiratory morbidity and concomitant growth impairment. Close follow-up beyond the neonatal period is therefore required.

Effect of Peep and Tidal Volume on Aeration of the Preterm Neonatal Lung

Previous studies suggest that positive end expiratory pressure (PEEP) promotes aeration of the preterm lung. The role of tidal volume has been less clear. We aimed to study the effects of different PEEPs (0, 5, 8 and 10 cm H2O) and VTs (4, 8, and 12 mL/kg) on the establishment of functional residual capacity (FRC). 27d preterm rabbit pups (equivalent to a surfactant deficient extremely preterm infant) were anaesthetised and surgically intubated. Volume targeted intermittent positive pressure ventilation (IPPV) was provided at each permutations of the above PEEPs and VTs. The primary outcome was FRC after 160 inflations, measured by plethysmography. Secondary outcomes included static compliance and homogeneity of tidal ventilation assessed using synchrotron based techniques (Spring8, Japan). Mean (SE) FRC and static compliance after 160 inflations are shown below: Table Linear regression of both FRC and compliance was statistically significant against both VT and PEEP separately (p≤0.01). No pup developed a pneumothorax. Video imaging demonstrates more homogeneous tidal ventilation in pups with better established FRC. PEEP and VT both played a role in the establishment of FRC in fully ventilated infants. Future studies should assess which strategies promote aeration at birth whilst minimising lung injury.

Pleural effusion complicates monitoring of respiratory mechanics*

Although pleural effusion reduces respiratory system compliance by restricting the lungs, the effusion volume is partially accommodated by chest wall expansion. The implications for these opposing volume changes on airway pressure monitoring in ventilated patients with pleural effusion are unreported. We investigated the interactions among pleural effusion, positive end-expiratory pressure, and indices of respiratory mechanics in a swine model. Interventional animal model. Hospital animal research facility. Nine deeply anesthetized swine. The preparation included tracheostomy, arterial/venous catheter placement, and chest tube insertion. Animals were ventilated throughout the study at 9 mL/kg, and frequency was adjusted to maintain normocapnia (inspiratory:expiratory=1:2, FIO2=0.5) and positive end-expiratory pressure of 1 cm H2O and 10 cm H2O. Fluid was instilled into the right pleural space to simulate effusions of 13 mL/kg (pleural effusion 1) and 26 mL/kg (pleural effusion 2). Quantitative computerized tomography studies (in five animals) and functional residual capacity volumes (wash-in/wash-out technique) were obtained for each pleural effusion/positive end-expiratory pressure combination. Mean functional residual capacity compared to baseline at positive end-expiratory pressure of 1 cm H2O was decreased by pleural effusion 1 and pleural effusion 2 (-42%, -64%) and restored by positive end-expiratory pressure of 10 cm H2O (moderate) to +23% of baseline for pleural effusion 1 and +1% for pleural effusion 2. Plateau pressure increased and compliance decreased in response to pleural effusion 1 and pleural effusion 2. Moderate positive end-expiratory pressure applied during both pleural effusion quantities restored plateau pressure and tidal compliance to prepleural effusion values. Computed tomography studies revealed lung compression and tidal derecruitment cycles occurring with pleural effusion at positive end-expiratory pressure of 1 cm H2O, whereas a moderate positive end-expiratory pressure restored prepleural effusion functional residual capacity and prevented lung and intratidal derecruitment. When pleural effusion is present, respiratory mechanics must be interpreted cautiously and sufficient positive end-expiratory pressure should be applied to prevent extensive collapse and intratidal cycles of recruitment/derecruitment.

Lung function abnormalities in infants developing bronchopulmonary dysplasia

ObjectiveTo determine if infants developing bronchopulmonary dysplasia (BPD), particularly mild BPD, initially had minimal lung function abnormalities, which then worsened throughout the neonatal period.DesignProspective observational study.SettingTertiary neonatal intensive care unit.Patients74...

Age-specific association between percent body fat and pulmonary function in apparently normal children in Ogbomoso, Oyo state, Nigeria

This study describes the association between percent body fat and pulmonary function among apparently normal twenty male children tidal volume aged 4 years and twenty male children aged 10 years in Ogbomoso. The mean functional residual capacity of the lung in male children aged 10 years was significantly higher than in male children aged 4 years (P 0.05). The mean percent body fat were 11.74% and 6.76% in male children age 4 years and 10 years, respectively. The mean percent body fat was significantly higher in male children aged 4 years than male children aged 10 years (P

The Impact of Oral Premedication with Midazolam on Respiratory Function in Children

Premedication with midazolam is commonly used in children to reduce anxiety and improve cooperation before anesthesia. However, it has the potential to alter respiratory function because of its muscle relaxant properties. We assessed functional residual capacity (FRC), ventilation homogeneity, using a lung clearance index (LCI), and respiratory mechanics in children awake and 20 min after oral premedication with midazolam (0.3 mg/kg). FRC and LCI were measured using a SF(6) multibreath washout technique while respiratory resistance and elastance were extracted from the input impedance obtained by forced oscillation technique in 18 children (3-8 yr) before and after oral premedication with midazolam. Premedication led to a small (6.5%) but statistically significant decrease in group mean FRC from 25.0 (SD 1.4) to 23.4 (1.9) mL/kg and an associated increase in LCI by 7.8% from 6.4 (0.4) to 6.9 (0.4), indicating increased ventilation inhomogeneities. Furthermore, midazolam resulted in a statistically significant increase in respiratory resistance by 7.4% from 3.38 (0.6) to 3.62 (0.6) cm H(2)O s/L (P < 0.001) and in respiratory elastance by 9.2% from 48.8 to 52.9 cm H(2)O s/L (P < 0.001). The changes in FRC, LCI, resistance and elastance were significantly correlated (P < 0.001). In children with normal lungs, premedication with a relatively small-dose of midazolam led to mild changes in respiratory variables shortly after its administration. However, the anesthesiologist should be aware that using midazolam in children at high risk of respiratory complications under anesthesia might lead to a greater decrease in respiratory function.