Reduction In Functional Residual Capacity Research Articles

Respiratory function under anaesthesia

General anaesthesia can affect every aspect of ventilation. It produces dose dependent depression of control of respiration. Carbon dioxide response curve is shifted to the right. Muscle tone is reduced and the airway can get obstructed. One of the most prominent changes is reduction in functional residual capacity (FRC) with the adoption of supine function and induction of anaesthesia. The closing capacity increases with age. The atelectasis that occurs consequent to the fall in FRC and increasing age is compounded by the use of high concentrations of oxygen, cephalad movement of the diaphragm, residual effect of muscle relaxants and inadequate analgesia after thoracic or abdominal surgery. One of the important causes of ventilation perfusion mismatch during anaesthesia is atelectasis. This has been shown to contribute to hypoxia as well as increased postoperative pulmonary complications. A lot of research is being conducted as to reduce the effects of atelectasis during anaesthesia, including the best ventilator strategy during anaesthesia. Most inhalation anaesthetics are good bronchodilators. Inhalation anaesthetics depress hypoxic pulmonary vasoconstriction (HPV) beyond 1 MAC. The movement of ciliary movements is reduced with the use of dry gases. All these can increase postoperative pulmonary complications which are important causes of postoperative morbidity. Appropriate preoperative preparation has to be combined with optimal management of ventilation intraoperatively to minimise postoperative pulmonary complications. The role of lower tidal volume, use of positive end-expiratory pressure, limiting oxygen concentrations and the utility of recruitment manoeuvres are increasingly being recognised and have been the topics of recent research.

Postural changes in lung volumes in patients with heart failure and Cheyne-Stokes respiration: Relationship with sleep apnea severity

Background and aimIt has been proposed that the increased severity of sleep apnea frequently observed in heart failure (HF) patients with Cheyne-Stokes respiration (CSR) when sleeping in the supine compared to the lateral position, may be caused by the concomitant reduction in functional residual capacity (FRC). We assessed positional changes in FRC in patients with CSR and investigated the relationship between these changes in the laboratory and corresponding changes in CSR severity during sleep. MethodsAfter a diagnostic polysomnography, 18 HF patients with dominant CSR and an apnea-hypopnea index (AHI)≥15 events/h underwent a standard pulmonary function test in the sitting position. Measurements were repeated in the supine, left lateral and right lateral. The latter two measurements were averaged to obtain a single lateral measurement. ResultsThe FRC in the seated position was 3.0 ± 0.5 L (85 ± 13% of predicted), decreased to 2.3 ± 0.3 L (−21 ± 8%, p < 0.0001) in the supine position, and increased to 2.8 ± 0.4 L (+21 ± 12%, p < 0.0001) from the supine to the lateral position (−5±8% vs seated, p = 0.013). During sleep, the AHI and the apnea index (AI) decreased from 47 ± 15 events/h to 26 ± 12 events/h (−46 ± 20%, p < 0.0001) and from 29 ± 21 events/h to 12 ± 10 events/h (−61 ± 40%, p < 0.001) from the supine to the lateral position. Changes in the AI were significantly correlated with corresponding changes in FRC (ρ = −0.55, p = 0.032). ConclusionIn patients with HF and CSR, lying in the supine position causes a significant reduction in FRC in the context of a chronically reduced FRC. The negative correlation between postural changes in FRC and AI supports the hypothesis that the reduction in lung gas stores in the supine position may promote/exacerbate respiratory control instability.

This Month in Anesthesiology

This Month in Anesthesiology

Respiratory consequences of intra-abdominal hypertension.

Intra-abdominal hypertension (IAH) is a common complication in critically ill patients that may lead to multiorgan failure and is associated to worse outcome. Respiratory failure is among the most important consequences of IAH and it is originated by different mechanisms, such as chest wall elastance increase, functional residual capacity reduction, compression atelectasis and lung edema formation through reduction in lymphatic drainage. Many experimental studies showed that total lung capacity and functional residual capacity can be decreased by 40% during abdominal hypertension, while respiratory system and chest wall pressure-volume curves can be significantly shifted downward and to the right. Moreover, the relationship between intra-abdominal volume and airway pressure has been found to be exponential, meaning that small increases in volume can translate in dramatic increases in pressure. Clinical studies confirmed relevant atelectasis in dependent lung regions during IAH, with significant reductions in functional residual capacity and compromised oxygenation. Moreover, sepsis-related capillary leak and fluid overload may aggravate IAH and respiratory failure, thus establishing a dangerous vicious circle. Respiratory management of patients with IAH is challenging and there is no univocal answer. The measurement of intra-abdominal pressure and esophageal pressure (as a surrogate of pleural pressure) may be useful in assessing the condition and guiding mechanical ventilation. Positive end-expiratory pressure (PEEP) must be carefully selected to counteract IAH-related diaphragm displacement, but too high PEEP levels are associated with hemodynamic failure. Continuous negative extra-abdominal pressure is a promising approach, but its clinical application needs more investigation.

Apnoeic oxygenation and ventilation: go with the flow

Apnoeic oxygenation and ventilation: go with the flow

The Effect of Anesthesia and Analgesia on Control of Breathing after Bariatric Surgery: A Systematic Review and Meta-Analysis of Randomized Control Trials

Abstract Background general anesthesia and mechanical ventilation impair pulmonary function, even in normal individuals, and results in decreased oxygenation in the post anesthesia period. They also cause a reduction in functional residual capacity of up to 50% of the pre anesthesia value. It has been shown that pulmonary atelectasis is a common finding in anesthetized individuals because it occurs in 85% to 90% of healthy adults. Aim of the Work: Study of the effect of anesthesia and analgesia on control of breathing after bariatric surgery. Patients and Methods study design: Systemic Review and Meta-analysis study. Published studies and abstracts concerning prevention and management of complications associated with patient positioning during surgeries were identified through a comprehensive search of electronic databases that will include PubMed (www.ncbi.nlm.nih.gov./entrez/query.fcgi), ScienceDirect (www.sciencedirect.com), Scirus (www.scirus.com/srsapp), ISI Web of Knowledge (http://www.isiwebofknowledge.com), Google Scholar (http://scholar.google. com) and CENTRAL (Cochrane Central Register of Controlled Trials (http://www. mrw.interscience.wiley.com/cochrane/cochrane_clcentral_articles_fs.htm), using a combination of the following key words: “Anesthesia”, “analgesia”, “respiratory outcome” and “morbid obese”. Results our initial search yielded 98 citations. Based on the screening criteria for titles and abstracts, 47 citations were excluded. After reviewing the full text of the remaining 52 reports, only 17 eligible RCTs fit our inclusion criteria and were selected for the study. All studies were published in English during 2000 to 2017, and the sample sizes ranged from 28 to 90 patients. Among these studies 50 obese patients were elevated and reported distinct outcome measurements. In all trials, the recruited patients were American Society of Anesthesiologists (ASA) status I–III who underwent general anesthesia with endotracheal intubation. In addition, in all trials the patients underwent elective bariatric operations. The mean BMI of the patients ranged from 37.7 to 54.0 kg/m2. Conclusion our meta-analysis indicated that recovery was significantly faster in the desflurane groups than in the sevoflurane, isoflurane, and propofol groups in obese adult patients who underwent bariatric surgery. Although no clinically relevant difference was observed in the PACU discharge time, or postoperative pain scores, patients who were given desflurane exhibited higher oxygen saturation on entry to or during stays in the PACU. Thus, in morbidly obese patients, we suggest that desflurane should be considered as the inhaled anesthetic because of its more rapid and consistent recovery profile.

Efficacity of Ventilator strategy in A.R.D.S (Acute Respiratory Distress Syndrome).

Background: ARDS is defined as pulmonary inflammatory process characterized by increased capillary permeability associated with acute severe hypoxemia and bilateral infiltrates on the chest radiograph. Chlinical manifestations of ARDS is associated with a reduction of functional residual capacity and static compliance of the respiratory system.Recently,after experimental models and physiological studies have just established the principles to understand the potential beneficial effects of PEEP and reduction in mortality to 22%. The benefit of PEEP has been demonstrated in terms of preventing cyclic opening and collapsing alveoli in acute respiratory distress syndrome patients (ARDS).&#x0D; Aim of study: To determine the appropriate PEEP level in-patients with ARDS.&#x0D; Objective: By using optimal PEEP:to realize the maximal alveolar recruitment.To avoid the decrease of oxygen delivery (DO2) as result of an unfavourable reduction in cardiac output.&#x0D; Material and methods:Retrospectiv study of 120 patients which only 63 of them are included in study with age 18-70 years old.(2012-2014 ) The entry criteria were clinically (severe dyspnoea, tachypnea, cyanosis); PaO2/FiO2 &lt;200mmHG, the presence of bilateral chest infiltrates. The exclusion criteria were: aged &lt; 18 yrs, COPD in history of diseases, heart attack; PEEP was set the level that provided the greatest improvement in oxygenation. The optimal PEEP came as a result of gradual increase of PEEP from 2-5 cmH2O every 6 hours, depended on gas analyses. The right PEEP level is the PEEP allowing the highest PaO2 value without causing hemodynamic compromise.&#x0D; Results: During this study we conclude that the gradual increase of PEEP improves significantly arterial oxygen tension (PaO2). Per value of PEEP 9.6-15.8, CI 95% is 145.9-191.8. The Pearson test with a significant correlation coefficient of level 0.995 and significance level 0.000 shows also a very important result. It was considered significant statistically the value of P≤ 0.05. Also the value of Chi ² of PaO2 and of PEEP, has resulted significant in 0.950 with P &lt; 0.001.&#x0D; Conclusion: Mechanical ventilation using optimal PEEP increases the value of PaO2. As a matter of fact 88% of cases with PaO2 &gt; 220 mmHg survive. The role of PEEP in clinical practice is still debated but, in selected categories of patients with a careful monitoring, it may play an important role in improving outcome.

Postoperative pulmonary complications in robot-assisted uro-oncological surgeries: Our experience in a tertiary cancer care centre.

Postoperative pulmonary complications in robot-assisted uro-oncological surgeries: Our experience in a tertiary cancer care centre.

Influence of body mass on predicted values of static hyperinflation in COPD.

IntroductionFor interpretation of body plethysmographic static hyperinflation, reference values are of crucial importance. Earliest reference values have been published by the European Coal and Steel Community (ECSC) and are based on sex, body height and age as predictors. As obesity can lead to a reduction of functional residual capacity (FRC) in lung-healthy subjects, more recent approaches included body weight or body surface area. This raises the question whether these models are appropriate in patients with COPD-induced hyperinflation.MethodSeveral FRC prediction models and their relation to body weight were analyzed in 1513 patients with stable COPD (mean [SD] age: 64.5 [8.2] years; GOLD grades 1–4: 219/722/484/88), a subset of the multicenter COPD and Systemic Consequences – Comorbidities Network cohort.ResultsAbsolute values of FRC were inversely related to body mass index (p<0.001). Applying the ECSC equations to calculate predicted values, this pattern was maintained (p<0.001). By contrast, an inverted, ie, positive, relation occurred when using equations that include body weight or surface area (p<0.001). The present analysis confirmed the inverse relation of body mass and FRC in COPD, resulting from a restrictive ventilatory pattern by diaphragm elevation and decreased chest wall compliance in obesity. The weight influence in the prediction models, as obtained from lung-healthy controls, appears to lead to an overcorrection and consequently to an inappropriate overestimation of hyperinflation as indicated by FRC %predicted in COPD.ConclusionIt is concluded that models not including body weight as predictor, like the classical ECSC equations, could be superior in the interpretation of FRC in COPD.

The spleen

The spleen

Operational Lung Volumes While Seated, Supine, and During Exercise in Obese and Nonobese Children

PURPOSE: The effects of adult obesity on lung function at rest, such as reductions in functional residual capacity and expiratory reserve volume, are well recognized. However, the effects of obesity on operational lung volumes at rest, while lying supine, and during exercise in obese children are unknown but could create meaningful respiratory limitations. METHODS: 11 nonobese (Ht: 143.3±5.2 cm; Wt: 35.8±3.8 kg; BMI percentile: 50±21; Body fat: 27±6%) and 12 obese (Ht: 149.7±6.7 cm; Wt: 65.8±14.4 kg; BMI percentile: 97.5±1.4; Body fat: 46±3%) children underwent dual energy x-ray absorptiometry, pulmonary function testing, and measurement of operational lung volumes when seated upright, while supine, during constant load cycling at 40 W, and during maximal exercise testing. RESULTS: Ratio of forced expiratory volume in the first second and forced vital capacity (FEV1/FVC) was lower in obese compared with nonobese children (83.6±4.1 vs. 88.6±4.1%; P=0.004). Functional residual capacity (FRC) was lower in obese compared with nonobese children when seated upright (38.5±4.8 vs. 49.3±4.0%TLC; P < 0.001) and while supine (35.0±6.4 vs. 45.4±6.5%TLC; P < 0.001). Three children (2 obese) experienced expiratory flow limitation (EFL) while supine. Both end expiratory lung volume (EELV) and end inspiratory lung volumes (EILV) were lower during exercise at 40 W (P < 0.01) and EILV was lower at peak exercise (P=0.048) in obese compared with nonobese children. EELV did not change from rest to exercise at 40 W or peak exercise in nonobese children. In obese children, EELV was higher at peak exercise (44.4±4.7%TLC) compared with rest and exercise at 40 W (40.5±4.1 and 38.7±3.1%TLC, respectively; P < 0.05). None of the nonobese children experienced EFL during exercise. In obese children, one experienced EFL during exercise at 40 W (44%tidal volume; VT) and seven experienced EFL at peak exercise (37±22%VT). Higher levels of fat mass were associated with lower levels of FRC when seated (r=-0.88; P < 0.001) and while supine (r=-0.65; P=0.003), and EELV during exercise at 40 W (r=-0.68; P=0.001). CONCLUSIONS: Obese children demonstrate low lung volume breathing when seated, while supine, and during exercise, which may contribute to an obstructive breathing pattern at rest as well as EFL and dynamic hyperinflation during peak exercise.

Effect of Body Mass Index in Acute Respiratory Distress Syndrome

Abstract Background Obesity is associated in healthy subjects with a great reduction in functional residual capacity and with a stiffening of lung and chest wall elastance, which promote alveolar collapse and hypoxaemia. Likewise, obese patients with acute respiratory distress syndrome (ARDS) could present greater derangements of respiratory mechanics than patients of normal weight. Methods One hundred and one ARDS patients were enrolled. Partitioned respiratory mechanics and gas exchange were measured at 5 and 15 cm H2O of PEEP with a tidal volume of 6–8 ml kg−1 of predicted body weight. At 5 and 45 cm H2O of PEEP, two lung computed tomography scans were performed. Results Patients were divided as follows according to BMI: normal weight (BMI≤25 kg m−2), overweight (BMI between 25 and 30 kg m−2), and obese (BMI>30 kg m−2). Obese, overweight, and normal-weight groups presented a similar lung elastance (median [interquartile range], respectively: 17.7 [14.2–24.8], 20.9 [16.1–30.2], and 20.5 [15.2–23.6] cm H2O litre−1 at 5 cm H2O of PEEP and 19.3 [15.5–26.3], 21.1 [17.4–29.2], and 17.1 [13.4–20.4] cm H2O litre−1 at 15 cm H2O of PEEP) and chest elastance (respectively: 4.9 [3.1–8.8], 5.9 [3.8–8.7], and 7.8 [3.9–9.8] cm H2O litre−1 at 5 cm H2O of PEEP and 6.5 [4.5–9.6], 6.6 [4.2–9.2], and 4.9 [2.4–7.6] cm H2O litre−1 at 15 cm H2O of PEEP). Lung recruitability was not affected by the body weight (15.6 [6.3–23.4], 15.7 [9.8–22.2], and 11.3 [6.2–15.6]% for normal-weight, overweight, and obese groups, respectively). Lung gas volume was significantly lower whereas total superimposed pressure was significantly higher in the obese compared with the normal-weight group (1148 [680–1815] vs 827 [686–1213] ml and 17.4 [15.8–19.3] vs 19.3 [18.6–21.7] cm H2O, respectively). Conclusions Obese ARDS patients do not present higher chest wall elastance and lung recruitability.

Influence of heart failure on resting lung volumes in patients with COPD.

ABSTRACTObjective: To evaluate the influence of chronic heart failure (CHF) on resting lung volumes in patients with COPD, i.e., inspiratory fraction-inspiratory capacity (IC)/TLC-and relative inspiratory reserve-[1 − (end-inspiratory lung volume/TLC)]. Methods: This was a prospective study involving 56 patients with COPD-24 (23 males/1 female) with COPD+CHF and 32 (28 males/4 females) with COPD only-who, after careful clinical stabilization, underwent spirometry (with forced and slow maneuvers) and whole-body plethysmography. Results: Although FEV1, as well as the FEV1/FVC and FEV1/slow vital capacity ratios, were higher in the COPD+CHF group than in the COPD group, all major "static" volumes-RV, functional residual capacity (FRC), and TLC-were lower in the former group (p < 0.05). There was a greater reduction in FRC than in RV, resulting in the expiratory reserve volume being lower in the COPD+CHF group than in the COPD group. There were relatively proportional reductions in FRC and TLC in the two groups; therefore, IC was also comparable. Consequently, the inspiratory fraction was higher in the COPD+CHF group than in the COPD group (0.42 ± 0.10 vs. 0.36 ± 0.10; p < 0.05). Although the tidal volume/IC ratio was higher in the COPD+CHF group, the relative inspiratory reserve was remarkably similar between the two groups (0.35 ± 0.09 vs. 0.44 ± 0.14; p < 0.05). Conclusions: Despite the restrictive effects of CHF, patients with COPD+CHF have relatively higher inspiratory limits (a greater inspiratory fraction). However, those patients use only a part of those limits, probably in order to avoid critical reductions in inspiratory reserve and increases in elastic recoil.

Effects of different levels of end-expiratory pressure on hemodynamic, respiratory mechanics and systemic stress response during laparoscopic cholecystectomy

ObjectiveGeneral anesthesia causes reduction of functional residual capacity. And this decrease can lead to atelectasis and intrapulmonary shunting in the lung. In this study we want to evaluate the effects of 5 and 10cmH2O PEEP levels on gas exchange, hemodynamic, respiratory mechanics and systemic stress response in laparoscopic cholecystectomy. MethodsAmerican Society of Anesthesiologist I–II physical status 43 patients scheduled for laparoscopic cholecystectomy were randomly selected to receive external PEEP of 5cmH2O (PEEP 5 group) or 10cmH2O PEEP (PEEP 10 group) during pneumoperitoneum. Basal hemodynamic parameters were recorded, and arterial blood gases (ABG) and blood sampling were done for cortisol, insulin and glucose level estimations to assess the systemic stress response before induction of anesthesia. Thirty minutes after the pneumoperitoneum, the respiratory and hemodynamic parameters were recorded again and ABG and sampling for cortisol, insulin, and glucose levels were repeated. Lastly hemodynamic parameters were recorded; ABG analysis and sampling for stress response levels were taken after 60minutes from extubation. ResultsThere were no statistical differences between the two groups about hemodynamic and respiratory parameters except mean airway pressure (Pmean). Pmean, compliance and PaO2; pH values were higher in ‘PEEP 10 group’. Also, PaCO2 values were lower in ‘PEEP 10 group’. No differences were observed between insulin and lactic acid levels in the two groups. But postoperative cortisol level was significantly lower in ‘PEEP 10 group’. ConclusionVentilation with 10cmH2O PEEP increases compliance and oxygenation, does not cause hemodynamic and respiratory complications and reduces the postoperative stress response.

Pulmonary Vascular Congestion: A Mechanism for Distal Lung Unit Dysfunction in Obesity.

RationaleObesity is characterized by increased systemic and pulmonary blood volumes (pulmonary vascular congestion). Concomitant abnormal alveolar membrane diffusion suggests subclinical interstitial edema. In this setting, functional abnormalities should encompass the entire distal lung including the airways.ObjectivesWe hypothesize that in obesity: 1) pulmonary vascular congestion will affect the distal lung unit with concordant alveolar membrane and distal airway abnormalities; and 2) the degree of pulmonary congestion and membrane dysfunction will relate to the cardiac response.Methods54 non-smoking obese subjects underwent spirometry, impulse oscillometry (IOS), diffusion capacity (DLCO) with partition into membrane diffusion (DM) and capillary blood volume (VC), and cardiac MRI (n = 24). Alveolar-capillary membrane efficiency was assessed by calculation of DM/VC.Measurements and Main ResultsMean age was 45±12 years; mean BMI was 44.8±7 kg/m2. Vital capacity was 88±13% predicted with reduction in functional residual capacity (58±12% predicted). Despite normal DLCO (98±18% predicted), VC was elevated (135±31% predicted) while DM averaged 94±22% predicted. DM/VC varied from 0.4 to 1.4 with high values reflecting recruitment of alveolar membrane and low values indicating alveolar membrane dysfunction. The most abnormal IOS (R5 and X5) occurred in subjects with lowest DM/VC (r2 = 0.31, p<0.001; r2 = 0.34, p<0.001). Cardiac output and index (cardiac output / body surface area) were directly related to DM/VC (r2 = 0.41, p<0.001; r2 = 0.19, p = 0.03). Subjects with lower DM/VC demonstrated a cardiac output that remained in the normal range despite presence of obesity.ConclusionsGlobal dysfunction of the distal lung (alveolar membrane and distal airway) is associated with pulmonary vascular congestion and failure to achieve the high output state of obesity. Pulmonary vascular congestion and consequent fluid transudation and/or alterations in the structure of the alveolar capillary membrane may be considered often unrecognized causes of airway dysfunction in obesity.

Effect of body mass index in acute respiratory distress syndrome

BackgroundObesity is associated in healthy subjects with a great reduction in functional residual capacity and with a stiffening of lung and chest wall elastance, which promote alveolar collapse and hypoxaemia. Likewise, obese patients with acute respiratory distress syndrome (ARDS) could present greater derangements of respiratory mechanics than patients of normal weight. MethodsOne hundred and one ARDS patients were enrolled. Partitioned respiratory mechanics and gas exchange were measured at 5 and 15 cm H2O of PEEP with a tidal volume of 6–8 ml kg−1 of predicted body weight. At 5 and 45 cm H2O of PEEP, two lung computed tomography scans were performed. ResultsPatients were divided as follows according to BMI: normal weight (BMI≤25 kg m−2), overweight (BMI between 25 and 30 kg m−2), and obese (BMI>30 kg m−2). Obese, overweight, and normal-weight groups presented a similar lung elastance (median [interquartile range], respectively: 17.7 [14.2–24.8], 20.9 [16.1–30.2], and 20.5 [15.2–23.6] cm H2O litre−1 at 5 cm H2O of PEEP and 19.3 [15.5–26.3], 21.1 [17.4–29.2], and 17.1 [13.4–20.4] cm H2O litre−1 at 15 cm H2O of PEEP) and chest elastance (respectively: 4.9 [3.1–8.8], 5.9 [3.8–8.7], and 7.8 [3.9–9.8] cm H2O litre−1 at 5 cm H2O of PEEP and 6.5 [4.5–9.6], 6.6 [4.2–9.2], and 4.9 [2.4–7.6] cm H2O litre−1 at 15 cm H2O of PEEP). Lung recruitability was not affected by the body weight (15.6 [6.3–23.4], 15.7 [9.8–22.2], and 11.3 [6.2–15.6]% for normal-weight, overweight, and obese groups, respectively). Lung gas volume was significantly lower whereas total superimposed pressure was significantly higher in the obese compared with the normal-weight group (1148 [680–1815] vs 827 [686–1213] ml and 17.4 [15.8–19.3] vs 19.3 [18.6–21.7] cm H2O, respectively). ConclusionsObese ARDS patients do not present higher chest wall elastance and lung recruitability.

Prevalence and reversibility of lung hyperinflation in adult asthmatics with poorly controlled disease or significant dyspnea.

In asthma, inflammation affects both the proximal and distal airways and may induce significant hyperinflation (HI). This study sought to evaluate the prevalence of HI in asthmatic patients with poorly controlled disease and/or dyspnea. Poor asthma control was defined by an Asthma Control Test (ACT) score <20 (n = 287), and dyspnea was defined as a modified Medical Research Council score ≥1 (n = 18). HI was defined as either a residual volume/total lung capacity (RV/TLC) above the upper limit of normal (RV-HI) or a functional residual capacity (FRC) >120% predicted (FRC-HI). HI reversibility after administration of salbutamol (400 μg) was defined as a decrease in RV >20% or a reduction in FRC >10%. Changes in dyspnea and chest tightness were evaluated on a visual analogue scale. Both RV-HI and FRC-HI were observed in 48% of the 305 patients (mean ± SD age: 49 ± 17; FEV1 : 75 ± 18% predicted) included in the study. The prevalence of HI was higher in patients with a FEV1 <60% predicted (93% for RV-HI and 71% for FRC-HI, vs 21% and 41% in patients with a FEV1 > 80%). In patients with HI, the ACT score was lower and chest tightness higher. HI reversibility was obtained in 38% of the asthmatics with FRC-HI and 29% of the asthmatics with RV-HI, whereas FEV1 reversibility was obtained in half of these patients. HI is highly prevalent in poorly controlled asthmatics suggesting small airway dysfunction and may represent an additional criteria for evaluating responsiveness to bronchodilators.

Changes in multiple breath washout measures after raised volume rapid thoracoabdominal compression maneuvers in infants

Multiple breath inert gas washout (MBW) measurements in infants are performed supine and often obtained under sedation and thus are combined with other lung function tests such as raised volume rapid thoracoabdominal compression (RVRTC). In this study, we sought to determine the effects of RVRTC maneuvers on MBW measures. Compared with tests performed prior to RVRTC, MBW measured after RVRTC was associated with a small reduction in functional residual capacity and a more pronounced decrease in cumulative expired volume in both healthy children and children with obstructive lung disease (cystic fibrosis or recurrent wheeze) indicating a more efficient washout after the raised volume maneuvers. Lung Clearance Index (LCI) decreased significantly in infants with respiratory disease (change in LCI of -0.24 units post RVRTC; standard error (SE) ± 0.07 units; P = 0.0004), but not in healthy infants (change in LCI of -0.08 units; SE ± 0.11 units; P = 0.44). As the RVRTC maneuver affects MBW measurements in infants, the timing of testing procedures needs to be standardized in longitudinal studies.

Effect of Weight Loss on Postural Changes in Pulmonary Function in Obese Subjects: A Longitudinal Study.

Postural changes are known to affect normal lung volumes. A reduction in sitting to supine functional residual capacity (FRC) is well-described in non-obese subjects adopting a supine position. However, postural changes in lung volumes in the obese require further exploration. We aimed to longitudinally address the effects of weight loss on postural changes in lung volumes and pulmonary function in obese subjects. We tested the hypothesis that supine reduction in FRC would be absent in morbid obesity and recovered upon weight loss. This was a prospective, observational, longitudinal study. Consecutive morbidly obese adults (N = 12, age: 44 ± 14 y, body mass index: 45 ± 5 kg/m(2)) enrolled in a bariatric surgery program were included. Standard pulmonary function tests and blood gas analysis were performed both before and 1 y after surgery. Pulmonary function was assessed in both the sitting and supine position using spirometry and multi-breath helium dilution. Parameters recorded before and after weight loss were compared. The main outcome measure was FRC. Ten subjects were retested 1 y after surgery (body mass index: 31 ± 5 kg/m(2)). FRC was not affected by change in posture before surgery. Supine reduction in FRC was observed after weight loss (ΔFRC: -0.6 ± 0.4 L, sitting vs supine, P = .002). Pulmonary gas exchange improved (alveolar-to-arterial oxygen partial pressure difference: -8 ± 11 mm Hg, P = .035). Although postural change in FRC is absent when the morbidly obese adopt a supine position, supine reduction in FRC can be recovered following gastroplasty-induced weight loss, despite residual mild to moderate obesity. This also shows that mild to moderate obesity may affect supine FRC more than morbid obesity. (ClinicalTrials.gov registration NCT02207192.).

Pulmonary function changes in rats with taurocholate‐induced pancreatitis are attenuated by pretreatment with melatonin

Melatonin is a free radical scavenger and broad-spectrum antioxidant with immunomodulatory effects. We studied the effects of melatonin on changes in lung function, oxidative/nitrosative stress, and inflammatory cell sequestration in an acute pancreatitis (AP)-associated lung inflammation model. Acute pancreatitis was induced by injection of 5% sodium taurocholate into the pancreatic duct of rats. Animals were randomized into control, AP, and a melatonin pretreatment (10mg/kg)/AP group. Functional residual capacity (FRC), lung compliance (Cchord), expiratory flow rate at 50% (FEF50), airway resistance index (RI), and peak expiratory flow rate (PEF) were evaluated. White blood cell count (WBC) and hydrogen peroxide, lung lavage fluid WBC, methylguanidine, protein, lactic dehydrogenase (LDH), nitric oxide (NO), and leukotriene B4 (LTB4) levels were determined. Lung wet-to-dry weight ratio, peroxynitrite, and inducible nitric oxide synthase (NOS) mRNA and protein were measured. AP induction resulted in reductions in FRC, Cchord, FEF50, and PEF, and increase in RI and lung wet-to-dry weight ratio. Blood and lung lavage fluid WBC, lavage fluid LDH, protein, and blood hydrogen peroxide also increased. Levels of hydroxyl radicals, nitric oxide, and LTB4 in lung lavage fluid, inducible NOS mRNA, protein expression, and peroxynitrite in lung tissue also were significantly elevated. Pretreatment with melatonin attenuated obstructive and restrictive ventilatory insufficiency induced by AP. Blood and lavage WBC, lavage LDH and protein, lung edema, oxidative/nitrosative stress, and lipoxygenase pathway derivatives were also significantly attenuated by melatonin. We conclude that melatonin decreases AP-induced obstructive and restrictive lung function changes via its antioxidant and anti-inflammatory properties.