Effects of increasing tidal volume and end-expiratory lung volume on induced bronchoconstriction in healthy humans.

BACKGROUND: Increasing functional residual capacity (FRC) or tidal volume (VT) reduces airway resistance and attenuates the response to bronchoconstrictor stimuli in animals and humans. What is unknown is which one of the above mechanisms is more effective in modulating airway caliber and whether their combination yields additive or synergistic effects. To address this question, we investigated the effects of increased FRC and increased VT in attenuating the bronchoconstriction induced by inhaled methacholine (MCh) in healthy humans. METHODS: Nineteen healthy volunteers were challenged with a single-dose of MCh and forced oscillation was used to measure inspiratory resistance at 5 and 19 Hz (R5 and R19), their difference (R5-19), and reactance at 5 Hz (X5) during spontaneous breathing and during imposed breathing patterns with increased FRC, or VT, or both. Importantly, in our experimental design we held the product of VT and breathing frequency (BF), i.e, minute ventilation (VE) fixed so as to better isolate the effects of changes in VT alone. RESULTS: Tripling VT from baseline FRC significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Doubling VT while halving BF had insignificant effects. Increasing FRC by either one or two VT significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Increasing both VT and FRC had additive effects on R5, R19, R5-19 and X5, but the effect of increasing FRC was more consistent than increasing VT thus suggesting larger bronchodilation. When compared at iso-volume, there were no differences among breathing patterns with the exception of when VT was three times larger than during spontaneous breathing. CONCLUSIONS: These data show that increasing FRC and VT can attenuate induced bronchoconstriction in healthy humans by additive effects that are mainly related to an increase of mean operational lung volume. We suggest that static stretching as with increasing FRC is more effective than tidal stretching at constant VE, possibly through a combination of effects on airway geometry and airway smooth muscle dynamics.

Ivacaftor in cystic fibrosis with residual function: Lung function results from an N-of-1 study.

BACKGROUND: Ivacaftor shows benefit in patients with cystic fibrosis (CF) and CFTR mutations associated with residual CF transmembrane conductance regulator (CFTR) function. Here we further assess the effect of ivacaftor in such patients using an N-of-1 study design. METHODS: Patients aged ≥12 years with CF with clinical or molecular evidence of residual CFTR function were randomized to 1 of 4 treatment sequences for two 4-week, double-blind crossover cycles (each divided into 2 weeks of ivacaftor treatment and placebo) followed by 8 weeks of open-label ivacaftor treatment. The primary endpoint was absolute change from cycle baseline of percent predicted forced expiratory volume in 1 s (ppFEV1) after 2 weeks of treatment with ivacaftor relative to placebo. RESULTS: Absolute change (SD) from study baseline in ppFEV1 favored ivacaftor by 2.3 (1.0) percentage points (95% credible interval, 0.4-4.1) after 2 weeks of treatment. Absolute mean change (SD) from open-label baseline (defined as day 1 of the open-label ivacaftor treatment period) in ppFEV1 after 8 weeks of treatment was 4.7 (4.2) percentage points (P<.0001). Safety of ivacaftor was consistent with that observed in prior studies. CONCLUSIONS: Ivacaftor improved lung function during the double-blind and open-label treatment periods in patients with CF and CFTR mutations associated with residual CFTR function (ClinicalTrials.gov, NCT01685801).

High inspired oxygen fraction impairs lung volume and ventilation heterogeneity in healthy children: a double-blind randomised controlled trial.

BACKGROUND: Although a high inspired oxygen fraction (FiO2) is commonly used in paediatric anaesthesia, the impact on postoperative lung function is unclear. We compared lung volume, ventilation heterogeneity, and respiratory mechanics in anaesthetised children randomised to receive low or high FiO2 intraoperatively. METHODS: In a double-blind randomised controlled trial, children scheduled for elective surgery were randomly assigned FiO2 100% (n=29) or FiO2 80% (n=29) during anaesthesia induction and emergence. During maintenance of anaesthesia, participants assigned FiO2=100% at induction/emergence received FiO2=80% (FiO2>0.8 group); those randomised to FiO2=80% at induction/emergence received FiO2=35% intraoperatively (FiO2 [0.8→0.35 group]). During spontaneous breathing, we measured the (i) functional residual capacity (FRC) and lung clearance index (ventilation inhomogeneity) by multiple-breath nitrogen washout; and (ii) airway resistance and respiratory tissue elastance by forced oscillations, before operation, after discharge from the recovery room, and 24 h after operation. Mean (95% confidence intervals) are reported. RESULTS: Fifty eight children (12.9 [12.3-13.5] yr) were randomised; 22/29 (high group) and 21/29 (low group) children completed serial multiple-breath nitrogen washout measurements. FRC decreased in the FiO2>0.8 group after discharge from recovery (-12.0 [-18.5 to -5.5]%; P=0.01), but normalised 24 h later. Ventilation inhomogeneity increased in both groups after discharge from recovery, but persisted in the FiO2>0.8 group 24 h after surgery (6.1 [2.5-9.8%]%; P=0.02). Airway resistance and respiratory elastance did not differ between the groups at any time point. CONCLUSIONS: FiO2>0.8 decreases lung volume in the immediate postoperative period, accompanied by persistent ventilation inhomogeneity. These data suggest that FiO2>0.8 should be avoided in anaesthetised children with normal lungs. CLINICAL TRIAL REGISTRATION: NCT02384616.

Tidal breathing flow volume profiles during sleep in wheezing infants measured by impedance pneumography.

Overnight analysis of tidal breathing flow volume (TBFV) loops, recorded by impedance pneumography (IP), has been successfully applied in the home monitoring of children with wheezing disorders. However, little is known on how sleep physiology modifies the relationship between TBFV profiles and wheeze. We studied such interactions in wheezing infants. Forty-three infants recruited because of recurrent lower airway symptoms were divided into three groups based on their risk of asthma: high (HR), intermediate (IR), or low (LR). Sedated patients underwent infant lung function testing including assessment of airway responsiveness to methacholine at the hospital and a full-night recording of TBFV profiles at home with IP during natural sleep. Overnight TBFV indexes were estimated from periods of higher and lower respiration variability, presumably belonging to active [rapid eye movement (REM)] and quiet [non-REM (NREM)] sleep, respectively. From 35 valid recordings, absolute time indexes showed intrasubject sleep phase differences. Peak flow relative to time and volume was lower in HR compared with LR only during REM, suggesting altered expiratory control. Indexes estimating the concavity/convexity of flow decrease during exhalation suggested limited flow during passive exhale in HR compared with IR and LR, similarly during NREM and REM. Moreover, during REM convexity was negatively correlated with maximal flow at functional residual capacity and methacholine responsiveness. We conclude that TBFV profiles determined from overnight IP recordings vary because of sleep phase and asthma risk. Physiological changes during REM, most likely decrease in respiratory muscle tone, accentuate the changes in TBFV profiles caused by airway obstruction. NEW & NOTEWORTHY Impedance pneumography was used to investigate overnight tidal breathing flow volume (TBFV) indexes and their interactions with sleep phase [rapid eye movement (REM) vs. non-REM] at home in wheezing infants. The study shows that TBFV indexes vary significantly because of sleep phase and asthma risk of the infant and that during REM the changes in TBFV indexes caused by airway obstruction are accentuated and better associated with lung function of the infant.

Direct and indirect effects of Growth Hormone Deficiency (GHD) on lung function in children: A mediation analysis.

BACKGROUND: Studies on pulmonary function tests (PFTs) in Growth Hormone Deficiency (GHD) children are lacking. The aims of this study were: (i) to investigate PFTs in GHD pre-pubertal children with respect to Controls, before starting Growth Hormone Therapy (GHT) (T0); (ii) to evaluate changes of PFTs in GHD vs Controls, after 1-year GHT (T1). For both aims the mediation analysis (MA) was applied to evaluate the extent to which the relationship between GHD and PFTs could be ascribed to a height-mediated (indirect) or a GH direct effect. METHODS: 47 pre-pubertal GHD children (aged 5-14 years) underwent PFTs at T0 and T1. At T0, 47 healthy children matched for age and sex were enrolled as Controls. A MA was performed to assess the relationship between GHD and PFTs and height. Statistical analyses were performed using the statistical software R (https://cran.r-project.org/mirrors.html). A p-value <0.05 was considered significant. MEASUREMENTS AND MAIN RESULTS: At T0, PFTs indices were significantly lower in GHD than in Controls. From T0 to T1 a significant improvement was found in PFTs. The percentages of the mediated effect on FVC, FEV1, FEF25-75% and TLC were <50% at T0, suggesting that the direct effect was prevalent. At T1, the percentages of the mediated effect for spirometry indices were ≥50%, indicating that the indirect (height-mediated) effect was the most relevant. CONCLUSIONS: The study shows that pre-pubertal children with GHD have an impairment of lung function not exclusively attributable to the indirect (height-mediated) effect, but also to the direct GH action which is mitigated after 1-year of GHT.

The effects of electronic cigarette aerosol exposure on inflammation and lung function in mice.

Electronic cigarette usage is increasing worldwide, yet there is a paucity of information on the respiratory health effects of electronic cigarette aerosol exposure. This study aimed to assess whether exposure to electronic cigarette (e-cigarette) aerosol would alter lung function and pulmonary inflammation in mice and to compare the severity of any alterations with mice exposed to mainstream tobacco smoke. Female BALB/c mice were exposed for 8 wk to tobacco smoke, medical air (control), or one of four different types of e-cigarette aerosol. E-cigarette aerosols varied depending on nicotine content (0 or 12 mg/ml) and the main excipient (propylene glycol or glycerin). Twenty-four hours after the final exposure, we measured pulmonary inflammation, lung volume, lung mechanics, and responsiveness to methacholine. Mice exposed to tobacco cigarette smoke had increased pulmonary inflammation and responsiveness to methacholine compared with air controls. Mice exposed to e-cigarette aerosol did not have increased inflammation but did display decrements in parenchymal lung function at both functional residual capacity and high transrespiratory pressures. Mice exposed to glycerin-based e-cigarette aerosols were also hyperresponsive to methacholine regardless of the presence or absence of nicotine. This study shows, for the first time, that exposure to e-cigarette aerosol during adolescence and early adulthood is not harmless to the lungs and can result in significant impairments in lung function.

Pulmonary Function at Hospital Discharge in Preterm Infants Randomized to a Single Rescue Course of Antenatal Steroids.

OBJECTIVE: To compare the pulmonary function, measured at birth and at hospital discharge, of infants whose mothers had been randomized to a single rescue course of antenatal steroids versus those whose mothers had been randomized to placebo. STUDY DESIGN: This study involved follow-up at hospital discharge of subjects of a randomized, double-blinded trial. In the original trial, pregnant women at ≥14 days after their initial course of antenatal steroids and <34 weeks' gestation were randomized to rescue antenatal steroids (44 mothers, 56 infants) or placebo (41 mothers, 57 infants). Passive respiratory compliance (Crs), passive respiratory resistance, and functional residual capacity were measured in all infants at birth and again at discharge to evaluate changes in pulmonary mechanics over time. Statistical analyses were based on intention to treat. RESULTS: We previously reported that compared with infants in the placebo group, infants in the rescue antenatal steroids group had a higher mean Crs value measured within 72 hours of birth (1.21 vs 1.01 mL/cm H2O/kg; P < .05). Here we show that the Crs benefit in the antenatal steroids group was sustained until discharge. Infants in the placebo group demonstrated improvement in Crs such that by discharge, there was no difference in mean Crs between the rescue antenatal steroids and placebo groups (1.18 vs 1.22 mL/cm H2O/kg). CONCLUSIONS: Rescue antenatal steroids significantly increased Crs measured within 72 hours of birth, and this increase was sustained until hospital discharge. Preterm infants in the placebo group demonstrated a decreased initial Crs compared with the rescue antenatal steroids group, but achieved a comparable Crs by the time of discharge. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00669383.

Measurement of intraindividual airway tone heterogeneity and its importance in asthma.

While airways have some degree of baseline tone, the level and variability of this tone is not known. It is also unclear whether there is a difference in airway tone or in the variability of airway tone between asthmatic and healthy individuals. This study examined airway tone and intraindividual airway tone heterogeneity (variance of airway tone) in vivo in 19 individuals with asthma compared with 9 healthy adults. All participants underwent spirometry, body plethysmography, and high-resolution computed tomography at baseline and after maximum bronchodilation with albuterol. Airway tone was defined as the percent difference in airway diameter after albuterol at total lung capacity compared with baseline. The amount of airway tone in each airway varied both within and between subjects. The average airway tone did not differ significantly between the two groups (P = 0.09), but the intraindividual airway tone heterogeneity did (P = 0.016). Intraindividual airway tone heterogeneity was strongly correlated with airway tone (r = 0.78, P < 0.0001). Also, it was negatively correlated with the magnitude of the distension of the airways from functional residual capacity to total lung capacity at both baseline (r = -0.49, P = 0.03) and after maximum bronchodilation (r = -0.51, P = 0.02) in the asthma, but not the healthy group. However, we did not find any relationship between intraindividual airway tone heterogeneity and conventional lung function outcomes. Intraindividual airway tone heterogeneity appears to be an important characteristic of airway pathophysiology in asthma.

Incomplete Spontaneous Recovery from Airway Obstruction During Inhaled Anesthesia Induction: A Computational Simulation.

BACKGROUND: Inhaled induction with spontaneous respiration is a technique used for difficult airways. One of the proposed advantages is if airway patency is lost, the anesthetic agent will spontaneously redistribute until anesthetic depth is reduced and airway patency can be recovered. There are little and conflicting clinical or experimental data regarding the kinetics of this anesthetic technique. We used computer simulation to investigate this situation. METHODS: We used GasMan, a computer simulation of inhaled anesthetic kinetics. For each simulation, alveolar ventilation was initiated with a set anesthetic induction concentration. When the vessel-rich group level reached the simulation specified airway obstruction threshold, alveolar ventilation was set at 0 to simulate complete airway obstruction. The time until the vessel-rich group anesthetic level decreased below the airway obstruction threshold was designated time to spontaneous recovery. We varied the parameters for each simulation, exploring the use of sevoflurane and halothane, airway obstruction threshold from 0.5 to 2 minimum alveolar concentration (MAC), anesthetic induction concentration 2 to 4 MAC sevoflurane and 4 to 6 MAC halothane, cardiac output 2.5 to 10 L/min, functional residual capacity 1.5 to 3.5 L, and relative vessel-rich group perfusion 67% to 85%. RESULTS: In each simulation, there were 3 general phases: anesthetic wash-in, obstruction and overshoot, and then slow redistribution. During the first 2 phases, there was a large gradient between the alveolar and vessel-rich group. Alveolar do not reflect vessel-rich group anesthetic levels until the late third phase. Time to spontaneous recovery varied between 35 and 749 seconds for sevoflurane and 13 and 222 seconds for halothane depending on the simulation parameters. Halothane had a faster time to spontaneous recovery because of the lower alveolar gradient and less overshoot of the vessel-rich group, not faster redistribution. Higher airway obstruction thresholds, decreased anesthetic induction, and higher cardiac output reduced time to spontaneous recovery. To a lesser effect, decreased functional residual capacity and the decreased relative vessel-rich groups' perfusion also reduced the time to spontaneous recovery. CONCLUSIONS: Spontaneous recovery after complete airway obstruction during inhaled induction is plausible, but the recovery time is highly variable and depends on the clinical and physiologic situation. These results emphasize that induction is a non-steady-state situation, thus effect-site anesthetic levels should be modeled in future research, not alveolar concentration. Finally, this study provides an example of using computer simulation to explore situations that are difficult to investigate clinically.

Benefits of maltodextrin intake 2 hours before cholecystectomy by laparotomy in respiratory function and functional capacity: a prospective randomized clinical trial.

OBJECTIVE: To evaluate the change in respiratory function and functional capacity according to the type of preoperative fasting. METHODS: Randomized prospective clinical trial, with 92 female patients undergoing cholecystectomy by laparotomy with conventional or 2 hours shortened fasting. The variables measured were the peak expiratory flow, forced expiratory volume in the first second, forced vital capacity, dominant handgrip strength, and non-dominant handgrip strength. Evaluations were performed 2 hours before induction of anesthesia and 24 hours after the operation. RESULTS: The two groups were similar in preoperative evaluations regarding demographic and clinical characteristics, as well as for all variables. However, postoperatively the group with shortened fasting had higher values than the group with conventional fasting for lung function tests peak expiratory flow (128.7±62.5 versus 115.7±59.9; p=0.040), forced expiratory volume in the first second (1.5±0.6 versus 1.2±0.5; p=0.040), forced vital capacity (2.3±1.1 versus 1.8±0.9; p=0.021), and for muscle function tests dominant handgrip strength (24.9±6.8 versus 18.4±7.7; p=0.001) and non-dominant handgrip strength (22.9±6.3 versus 17.0±7.8; p=0.0002). In the intragroup evaluation, there was a decrease in preoperative compared with postoperative values, except for dominant handgrip strength (25.2±6.7 versus 24.9±6.8; p=0.692), in the shortened fasting group. CONCLUSION: Abbreviation of preoperative fasting time with ingestion of maltodextrin solution is beneficial to pulmonary function and preserves dominant handgrip strength.

Intravenous augmentation treatment and lung density in severe α1 antitrypsin deficiency (RAPID): a randomised, double-blind, placebo-controlled trial.

BACKGROUND: The efficacy of α1 proteinase inhibitor (A1PI) augmentation treatment for α1 antitrypsin deficiency has not been substantiated by a randomised, placebo-controlled trial. CT-measured lung density is a more sensitive measure of disease progression in α1 antitrypsin deficiency emphysema than spirometry is, so we aimed to assess the efficacy of augmentation treatment with this measure. METHODS: The RAPID study was a multicentre, double-blind, randomised, parallel-group, placebo-controlled trial of A1PI treatment in patients with α1 antitrypsin deficiency. We recruited eligible non-smokers (aged 18-65 years) in 28 international study centres in 13 countries if they had severe α1 antitrypsin deficiency (serum concentration <11 µM) with a forced expiratory volume in 1 s of 35-70% (predicted). We excluded patients if they had undergone, or were on the waiting list to undergo, lung transplantation, lobectomy, or lung volume-reduction surgery, or had selective IgA deficiency. We randomly assigned patients (1:1; done by Accovion) using a computerised pseudorandom number generator (block size of four) with centre stratification to receive A1PI intravenously 60 mg/kg per week or placebo for 24 months. All patients and study investigators (including those assessing outcomes) were unaware of treatment allocation throughout the study. Primary endpoints were CT lung density at total lung capacity (TLC) and functional residual capacity (FRC) combined, and the two separately, at 0, 3, 12, 21, and 24 months, analysed by modified intention to treat (patients needed at least one evaluable lung density measurement). This study is registered with ClinicalTrials.gov, number NCT00261833. A 2-year open-label extension study was also completed (NCT00670007). FINDINGS: Between March 1, 2006, and Nov 3, 2010, we randomly allocated 93 (52%) patients A1PI and 87 (48%) placebo, analysing 92 in the A1PI group and 85 in the placebo group. The annual rate of lung density loss at TLC and FRC combined did not differ between groups (A1PI -1·50 g/L per year [SE 0·22]; placebo -2·12 g/L per year [0·24]; difference 0·62 g/L per year [95% CI -0·02 to 1·26], p=0·06). However, the annual rate of lung density loss at TLC alone was significantly less in patients in the A1PI group (-1·45 g/L per year [SE 0·23]) than in the placebo group (-2·19 g/L per year [0·25]; difference 0·74 g/L per year [95% CI 0·06-1·42], p=0·03), but was not at FRC alone (A1PI -1·54 g/L per year [0·24]; placebo -2·02 g/L per year [0·26]; difference 0·48 g/L per year [-0·22 to 1·18], p=0·18). Treatment-emergent adverse events were similar between groups, with 1298 occurring in 92 (99%) patients in the A1PI group and 1068 occuring in 86 (99%) in the placebo group. 71 severe treatment-emergent adverse events occurred in 25 (27%) patients in the A1PI group and 58 occurred in 27 (31%) in the placebo group. One treatment-emergent adverse event leading to withdrawal from the study occurred in one patient (1%) in the A1PI group and ten occurred in four (5%) in the placebo group. One death occurred in the A1PI group (respiratory failure) and three occurred in the placebo group (sepsis, pneumonia, and metastatic breast cancer). INTERPRETATION: Measurement of lung density with CT at TLC alone provides evidence that purified A1PI augmentation slows progression of emphysema, a finding that could not be substantiated by lung density measurement at FRC alone or by the two measurements combined. These findings should prompt consideration of augmentation treatment to preserve lung parenchyma in individuals with emphysema secondary to severe α1 antitrypsin deficiency. FUNDING: CSL Behring.

Inhaled ß2-Agonist Therapy Increases Functional Residual Capacity in Mechanically Ventilated Children With Respiratory Failure.

OBJECTIVES: To test the hypothesis that in mechanically ventilated children with respiratory failure, aerosolized albuterol modifies functional residual capacity, lung mechanics, oxygen consumption, and hemodynamics. DESIGN: Prospective, self-control clinical trial. SETTING: A 24-bed PICU in a quaternary care, academic children's hospital. PATIENTS: 25 children (age range, 1-18 yr) undergoing mechanical ventilation to treat respiratory failure. Entry criteria included previously prescribed inhaled ß2 agonists. Physiologic measurements were performed prior to and 20 minutes after administration of aerosolized albuterol solution. Functional residual capacity was determined via nitrogen washout. INTERVENTIONS: Functional residual capacity, oxygen consumption, respiratory mechanics, and vital signs were measured were measured prior to and 20 minutes after administration of aerosolized albuterol solution. Functional residual capacity was determined via nitrogen washout. MEASUREMENT AND MAIN RESULTS: At baseline, functional residual capacity is only 53% of predicted. After aerosolized albuterol, functional residual capacity increased by 18.3% (p = 0.008). Overall, aerosolized albuterol had no effect on airway resistance. However, in patients with an endotracheal tube size of more than or equal to 4.0 mm, resistance decreased from 33 ± 3 to 25 ± 3 (p < 0.02). Inhaled albuterol administration had no effect on oxygen consumption despite an increase in heart rate from 116 ± 2 to 128 ± 2 beats/min (p < 0.0001). CONCLUSIONS: In pediatric patients with respiratory failure, aerosolized albuterol increases functional residual capacity without a decrease in resistance. In infants and children, aerosolized albuterol might favorably enhance pulmonary mechanics and thereby represent a novel strategy for lung recruitment in children with respiratory failure.

Sustained inflation at birth did not alter lung injury from mechanical ventilation in surfactant-treated fetal lambs.

BACKGROUND: Sustained inflations (SI) are used with the initiation of ventilation at birth to rapidly recruit functional residual capacity and may decrease lung injury and the need for mechanical ventilation in preterm infants. However, a 20 second SI in surfactant-deficient preterm lambs caused an acute phase injury response without decreasing lung injury from subsequent mechanical ventilation. HYPOTHESIS: A 20 second SI at birth will decrease lung injury from mechanical ventilation in surfactant-treated preterm fetal lambs. METHODS: The head and chest of fetal sheep at 126±1 day GA were exteriorized, with tracheostomy and removal of fetal lung fluid prior to treatment with surfactant (300 mg in 15 ml saline). Fetal lambs were randomized to one of four 15 minute interventions: 1) PEEP 8 cmH2O; 2) 20 sec SI at 40 cmH2O, then PEEP 8 cmH2O; 3) mechanical ventilation with 7 ml/kg tidal volume; or 4) 20 sec SI then mechanical ventilation at 7 ml/kg. Fetal lambs remained on placental support for the intervention and for 30 min after the intervention. RESULTS: SI recruited a mean volume of 6.8±0.8 mL/kg. SI did not alter respiratory physiology during mechanical ventilation. Heat shock protein (HSP) 70, HSP60, and total protein in lung fluid similarly increased in both ventilation groups. Modest pro-inflammatory cytokine and acute phase responses, with or without SI, were similar with ventilation. SI alone did not increase markers of injury. CONCLUSION: In surfactant treated fetal lambs, a 20 sec SI did not alter ventilation physiology or markers of lung injury from mechanical ventilation.

Higher fraction of inspired oxygen in anesthesia induction does not affect functional residual capacity reduction after intubation: a comparative study of higher and lower oxygen concentration.

BACKGROUND: Low fraction of inspired oxygen (FIO2) reduces the atelectasis area during anesthesia induction. However, atelectasis may occur during laryngoscopy and endotracheal intubation because lungs can collapse within a fraction of a second. We assessed the effects of ventilation with 100 and 40 % oxygen on functional residual capacity (FRC) in patients undergoing general anesthesia. METHODS: Twenty patients scheduled for elective open abdominal surgery were randomized into 40 % oxygen (GI, n = 10) and 100 % oxygen (GII, n = 10) groups and FRC was measured. Preoxygenation and mask ventilation with 40 and 100 % oxygen were used in GI and GII, respectively. In both groups, 40 % oxygen was used for anesthesia maintenance after intubation. Bilateral lung ventilation was performed with volume guarantee and low tidal volume (7 ml/kg predicted body weight) using bilevel airway pressure. We measured FRC and blood gas in all patients during preoxygenation, after intubation, and during surgery. RESULTS: FRC decreased from during preoxygenation (GI 2380 ml, GII 2313 ml) to after intubation (GI 1569 ml, GII 1586 ml) and significantly decreased during surgery (GI 1338 ml, GII 1417 ml) (P < 0.05). PaO2/FIO2 decreased from during preoxygenation (GI 419 mmHg, GII 427 mmHg) to after intubation (GI 381 mmHg, GII 351 mmHg) and significantly decreased during surgery (GI 333 mmHg, GII 291 mmHg) (P < 0.05). No significant differences were found between the groups in both parameters. CONCLUSIONS: FRC significantly decreased from the awake state to surgery in both groups. FRC was not influenced by FIO2 elevation at anesthesia induction.

Cardio-respiratory response to moderate chloral hydrate sedation in young lambs.

AIM: Chloral hydrate (CH) is the most commonly used sedative for medical procedures and lung function tests in infancy. The aim was to determine whether moderate CH sedation affects airway function, lung volume and ventilation. METHODS: Thirteen chronically instrumented 7- to 8-week-old lambs were studied both before and after CH sedation (50 mg/kg as intravenous bolus followed by 25 mg/kg/hour as continuous infusion). Nitrogen washout technique and lung mechanics analysis were used to assess functional residual capacity (FRC) and airway function. Moment analysis and lung clearance index were calculated as measures of gas mixing efficiency in distal airways. Respiratory rate, tidal volume, minute ventilation and indices of inspiratory drive were determined together with heart rate, blood pressure and oxygenation. RESULTS: No significant CH-induced changes were found for gas mixing efficiency, FRC or lung mechanics. Minute ventilation decreased slightly, but significantly, while indices of inspiratory drive remained unchanged. Heart rate increased significantly, but mean arterial blood pressure was unaffected. CONCLUSION: Moderate CH sedation did not significantly affect airway function or FRC. Although indices of inspiratory drive were not affected, minute ventilation decreased slightly. These findings indicate that reliable results can be obtained from lung function testing when CH is used for sedation.

Surfactant increases the uniformity of lung aeration at birth in ventilated preterm rabbits.

Surfactant deficiency is a major cause of respiratory failure in newborns. We have investigated the roles of surfactant and positive end-expiratory pressure (PEEP) in the development of a functional residual capacity (FRC) and the distribution of ventilation at birth. Preterm rabbit pups (28 d GA) were delivered and received either saline or surfactant and then ventilated with (3PEEP) or without (0PEEP) 3 cm H2O PEEP (groups: saline/0PEEP, surfactant/0PEEP, saline/3PEEP, surfactant/3PEEP). Lung gas volumes were measured using plethysmography, and the uniformity of ventilation was analyzed using phase contrast (PC) x-ray imaging. Surfactant/0PEEP pups had greater FRCs and the lungs were more uniformly ventilated than saline/0PEEP pups; FRC at inflation 19-21 was 2.46 ± 0.52 mL/kg versus 0.91 ± 0.95 mL/kg (p < 0.05). Saline/3PEEP pups developed an FRC of 7.54 ± 1.68 mL/kg at inflation 19-21 (p < 0.05), but the distribution of ventilation was initially nonuniform. Surfactant/3PEEP pups had an FRC of 8.50 ± 0.80 mL/kg (at inflation 19-21), and the distribution of ventilation was more uniform than with saline/3PEEP (p < 0.05). In ventilated preterm newborn rabbits, PEEP has a greater effect on FRC than surfactant, although the two are additive. Surfactant, administered at birth, markedly improved the uniformity of ventilation irrespective of whether PEEP was applied.

Pulmonary function and oxidative stress in workers exposed to styrene in plastic factory: occupational hazards in styrene-exposed plastic factory workers.

Styrene is a volatile organic compound used in factories for synthesis of plastic products. The pneumotoxicity of styrene in experimental animals is known. The aim of the present study was to study the effect of styrene on lung function and oxidative stress in occupationally exposed workers in plastic factory. Thirty-four male workers, between 18 and 40 years of age, exposed to styrene for atleast 8 hours a day for more than a year were studied, while 30 age- and sex-matched healthy subjects not exposed to styrene served as controls. Assessment of lung functions showed a statistically significant reduction (p < 0.05) in most of the lung volumes, capacities (FVC, FEV(1), VC, ERV, IRV, and IC) and flow rates (PEFR, MEF(75%), and MVV) in the study group (workers) as compared to controls. Malondialdehyde (MDA) was observed to be significantly high (p < 0.05) while ferric-reducing ability of plasma (FRAP) was significantly low (p < 0.05) in styrene-exposed subjects. Reduced glutathione (GSH) level was significantly depleted in exposed subjects as compared to control group. The mean value of serum cytochrome c in styrene-exposed subjects was found to be 1.1 ng/ml (0.89-1.89) while in control its levels were under detection limit (0.05 ng/ml). It shows that styrene inhalation by workers leads to increased level of oxidative stress, which is supposed to be the cause of lung damage.

Dynamic surface tension of natural surfactant extract under superimposed oscillations.

Surfactant dysfunction plays a major role in respiratory distress syndrome (RDS). This research seeks to determine whether the use of natural surfactant, Curosurf™ (Cheisi Farmaceutici, Parma, Italy), accompanied with pressure oscillations at the level of the alveoli can reduce the surface tension in the lung, thereby making it easier for infants with RDS to maintain the required level of functional residual capacity (FRC) without collapse. To simulate the alveolar environment, dynamic surface tension measurements were performed on a modified pulsating bubble surfactometer (PBS) type device and showed that introducing superimposed oscillations about the tidal volume excursion between 10 and 70 Hz in a surfactant bubble lowers interfacial surface tension below values observed using tidal volume excursion alone. The specific mechanisms responsible for this improvement are yet to be established; however it is believed that one mechanism may be the rapid transient changes in the interfacial area increase the number of interfacial binding sites for surfactant molecules, increasing adsorption and diffusion to the interface, thereby decreasing interfacial surface tension. Existing mathematical models in the literature reproduce trends noticed in experiments in the range of breathing frequencies only. Thus, a modification is introduced to an existing model to both incorporate superimposed pressure oscillations and demonstrate that these may improve the dynamic surface tension in the alveoli.

In utero smoke exposure and impaired response to inhaled corticosteroids in children with asthma.

BACKGROUND: Few studies have examined the effects of in utero smoke exposure (IUS) on lung function in children with asthma, and there are no published data on the impact of IUS on treatment outcomes in children with asthma. OBJECTIVES: To explore whether IUS exposure is associated with increased airway responsiveness among children with asthma and whether IUS modifies the response to treatment with inhaled corticosteroids (ICSs). METHODS: To assess the impact of parent-reported IUS exposure on airway responsiveness in childhood asthma, we performed a repeated-measures analysis of methacholine PC(20) data from the Childhood Asthma Management Program, a 4-year, multicenter, randomized, double-masked, placebo-controlled trial of 1041 children age 5 to 12 years comparing the long-term efficacy of ICS with mast cell stabilizing agents or placebo. RESULTS: Although improvement was seen in both groups, children with asthma and IUS exposure had on average 26% less of an improvement in airway responsiveness over time compared with unexposed children (P = .01). Moreover, while children who were not exposed to IUS who received budesonide experienced substantial improvement in PC(20) compared with untreated children (1.25-fold increase; 95% CI, 1.03-1.50; P = .02), the beneficial effects of budesonide were attenuated among children with a history of IUS exposure (1.04-fold increase, 95% CI, 0.65-1.68; P = .88). CONCLUSION: In utero smoke exposure reduces age-related improvements in airway responsiveness among children with asthma. Moreover, IUS appears to blunt the beneficial effects of ICS use on airways responsiveness. These results emphasize the importance of preventing this exposure through smoking cessation counseling efforts with pregnant women.