Closing volume: a reappraisal (1967-2007)

Beyond the Spirometry: New Diagnostic Modalities in Chronic Obstructive Pulmonary Disease

Spirometry can play a critical role as a gold standard in the diagnosis and treatment of patients with chronic obstructive pulmonary disease (COPD). While the criteria for diagnosis have advanced over time, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) standard of the forced expiratory volume in 1 second/forced vital capacity ratio <0.7 remains the most universally employed metric. However, spirometry cannot be utilized in all situations, and test execution can be difficult for some patients, often showing normal values in the early diagnosis of COPD. Therefore, research on new diagnostic methods is underway. Techniques include whole-body plethysmography for measurement of residual volume and inspiratory capacity and airway resistance, diffusing capacity of carbon monoxide or nitric oxide, impulse oscillometry, infrared time-offlight depth image sensor, diaphragm ultrasonography, which can enable early diagnosis and multifaceted assessment of patients with COPD.

Single breath nitrogen test as predictor of lung function decline and COPD over an 8-year follow-up

BACKGROUND

The single breath nitrogen (SBN2) test was proposed for early detection of "small airways disease" in the seventies. Few longitudinal studies have subsequently evaluated the relationships between SBN2 test measurements and lung function decline or COPD incidence.

AIM

This study evaluates whether SBN2 test abnormalities may be significant predictors of lung function decline and COPD incidence over an 8-year follow-up.

STUDY DESIGN AND METHODS

In this longitudinal study, 907 adults (20+ years old; 56% males) from the prospective Po River Delta epidemiological study underwent SBN2 test at baseline and spirometry testing at both baseline and follow-up 8-year apart. Multinomial and multiple regression models were used to assess associations of SBN2 indexes and rates of FEV1 decline or risk of COPD incidence over time, after adjusting for sex, height and baseline age, FEV1 and smoking status. COPD was defined according to either GOLD or ATS-ERS criteria.

RESULTS

Among SBN2 indexes, only the slope of alveolar plateau (N2-slope) was significantly associated with rates of FEV1 decline (7.93 mL/year for a one-unit change in N2-slope, p<0.0001), and with an increased risk of developing COPD as defined by GOLD (RR 1.81, 95%CI 1.29-2.52, mild; RR 2.78, 95%CI 1.70-4.53, moderate or severe obstruction) and ATS-ERS criteria (RR 1.62, 95%CI 1.14-2.29, mild; RR 3.40, 95%CI 1.72-6.73, moderate or severe obstruction).

CONCLUSION

In this population-based study, N2-slope from SBN2 test is a significant predictor of lung function decline and COPD incidence over an 8-year follow-up, confirming the role of the "small airways disease" in the natural history of COPD.

Small Airways Dysfunction and Lung Hyperinflation in Long COVID-19 Patients as Potential Mechanisms of Persistent Dyspnoea

BACKGROUND

Reticulation, ground glass opacities and post-infection bronchiectasis are present three months following hospitalisation in patients recovering from SARS-CoV-2 infection and are associated with the severity of acute infection. However, scarce data exist on small airways impairment and lung hyperinflation in patients with long COVID-19.

AIM

To evaluate small airways function and lung hyperinflation in previously hospitalised patients with long COVID-19 and their association with post-COVID-19 breathlessness.

METHODS

In total, 33 patients (mean ± SD, 53 ± 11 years) with long COVID-19 were recruited 149 ± 90 days following hospital discharge. Pulmonary function tests were performed and lung hyperinflation was defined as RV/TLC ≥ 40%. Small airways function was evaluated by measuring the closing volume (CV) and closing capacity (CC) using the single-breath nitrogen washout technique (SBN2W).

RESULTS

CC was 115 ± 28% pred. and open capacity (OC) was 90 ± 19. CC was abnormal in 13 patients (39%), CV in 2 patients (6.1%) and OC in 9 patients (27%). Lung hyperinflation was present in 15 patients, whilst the mean mMRC score was 2.2 ± 1.0. Lung hyperinflation was associated with CC (r = 0.772, p = 0.001), OC (r = 0.895, p = 0.001) and mMRC (r = 0.444, p = 0.010).

CONCLUSIONS

Long COVID-19 patients present with small airways dysfunction and lung hyperinflation, which is associated with persistent dyspnoea, following hospitalisation.

Small airways disease in chronic obstructive pulmonary disease

INTRODUCTION

Small airway disease (SAD) represents a common and critical feature of Chronic Obstructive Pulmonary Disease (COPD). Introduced in the '60s, SAD has gradually gained increasing interest as assessment methodologies have improved. Chronic exposure to smoking and noxious particles or gases induces inflammation and remodeling, leading to airway obstruction and SAD, eventually resulting in complete airway loss.

AREAS COVERED

A literature search up to June 2024 was performed in PubMed to identify articles on SAD and airway diseases mainly COPD, but also to the extent that it seemed relevant in the uncontrolled/severe asthma field, where SAD is better studied. We provide clinicians and translational scientists with a comprehensive analysis of the existing literature on SAD in COPD, concentrating on the underlying pathophysiological mechanisms, diagnostic techniques, and current pharmacological approaches targeting airflow obstruction in small airways.

EXPERT OPINION

Small airways are the primary site for the onset and progression of airflow obstruction in patients with COPD, with significant clinical consequences associated with poor lung function, hyperinflation, and impaired quality of life. The early identification of individuals with subclinical SAD may allow us to prevent its further progress from airway loss and potential development of emphysema and choose the appropriate therapeutic approach.

Airway opening pressure maneuver to detect airway closure in mechanically ventilated pediatric patients

Background

Airway closure, which refers to the complete collapse of the airway, has been described under mechanical ventilation during anesthesia and more recently in adult patients with acute respiratory distress syndrome (ARDS). A ventilator maneuver can be used to identify airway closure and measure the pressure required for the airway to reopen, known as the airway opening pressure (AOP). Without that maneuver, AOP is unknown to clinicians.

Objective

This study aims to demonstrate the technical adaptation of the adult maneuver for children and illustrate its application in two cases of pediatric ARDS (p-ARDS).

Methods

A bench study was performed to adapt the maneuver for 3-50 kg patients. Four maneuvers were performed for each simulated patient, with 1, 2, 3, and 4 s of insufflation time to deliver a tidal volume (Vt) of 6 ml/kg by a continuous flow.

Results

Airway closure was simulated, and AOP was visible at 15 cmH2O with a clear inflection point, except for the 3 kg simulated patient. Regarding insufflation time, a 4 s maneuver exhibited a better performance in 30 and 50 kg simulated patients since shorter insufflation times had excessive flowrates (>10 L/min). Below 20 kg, the difference in resistive pressure between a 3 s and a 4 sec maneuver was negligible; therefore, prolonging the maneuver beyond 3 s was not useful. Airway closure was identified in two p-ARDS patients, with the pediatric maneuver being employed in the 28 kg patient.

Conclusions

We propose a pediatric AOP maneuver delivering 6 ml/kg of Vt at a continuous low-flow inflation for 3 s for patients weighing up to 20 kg and for 4 s for patients weighing beyond 20 kg.

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

Airway pressure release ventilation for lung protection in acute respiratory distress syndrome: an alternative way to recruit the lungs

PURPOSE OF REVIEW

Airway pressure release ventilation (APRV) is a modality of ventilation in which high inspiratory continuous positive airway pressure (CPAP) alternates with brief releases. In this review, we will discuss the rationale for APRV as a lung protective strategy and then provide a practical introduction to initiating APRV using the time-controlled adaptive ventilation (TCAV) method.

RECENT FINDINGS

APRV using the TCAV method uses an extended inspiratory time and brief expiratory release to first stabilize and then gradually recruit collapsed lung (over hours/days), by progressively 'ratcheting' open a small volume of collapsed tissue with each breath. The brief expiratory release acts as a 'brake' preventing newly recruited units from re-collapsing, reversing the main drivers of ventilator-induced lung injury (VILI). The precise timing of each release is based on analysis of expiratory flow and is set to achieve termination of expiratory flow at 75% of the peak expiratory flow. Optimization of the release time reflects the changes in elastance and, therefore, is personalized (i.e. conforms to individual patient pathophysiology), and adaptive (i.e. responds to changes in elastance over time).

SUMMARY

APRV using the TCAV method is a paradigm shift in protective lung ventilation, which primarily aims to stabilize the lung and gradually reopen collapsed tissue to achieve lung homogeneity eliminating the main mechanistic drivers of VILI.

Pulmonary function testing in patients with liver cirrhosis (Review)

Liver cirrhosis is a common long-term outcome of chronic hepatic inflammation. Patients with liver cirrhosis may also have pulmonary complications. There are several reasons for pulmonary dysfunction in liver cirrhosis, including intrinsic cardiopulmonary dysfunction unrelated to liver disease and specific disorders related to the presence of liver cirrhosis and/or portal hypertension. The most prevalent and clinically significant pulmonary complications are hepatic hydrothorax, hepatopulmonary syndrome, spontaneous pulmonary empyema and portopulmonary hypertension. Pulmonary function tests (PFTs) have traditionally been used to assess the lung function of patients with liver cirrhosis. To the best of our knowledge, the present review is the first to detail all types of PFTs performed in patients with liver cirrhosis and discuss their clinical significance. Patients with liver cirrhosis have reduced values of spirometric parameters, diffusion capacity for carbon monoxide (DLCO), lung volumes, maximal inspiratory pressure and maximal expiratory pressure. Furthermore, they have a higher closing volume, a greater airway occlusion pressure 0.1 sec after the onset of inspiratory flow and greater exhaled nitric oxide values. In order to improve pulmonary function, patients with ascites may require therapeutic paracentesis. Such findings should be considered when evaluating individuals with liver disease, particularly those who may require surgery. Poor lung function, particularly restrictive lung disease, can have an impact on post-transplant outcomes, such as ventilator time, length of hospital duration and post-operative pulmonary complications; thus, the transplant care team needs to be aware of its prevalence and relevance.

Discordant Spirometry and Impulse Oscillometry Assessments in the Diagnosis of Small Airway Dysfunction

Background and objective: Spirometry is commonly used to assess small airway dysfunction (SAD). Impulse oscillometry (IOS) can complement spirometry. However, discordant spirometry and IOS in the diagnosis of SAD were not uncommon. We examined the association between spirometry and IOS within a large cohort of subjects to identify variables that may explain discordant spirometry and IOS findings. Methods: 1,836 subjects from the ECOPD cohort underwent questionnaires, symptom scores, spirometry, and IOS, and 1,318 subjects were examined by CT. We assessed SAD with R₅-R₂₀ > the upper limit of normal (ULN) by IOS and two of the three spirometry indexes (maximal mid-expiratory flow (MMEF), forced expiratory flow (FEF)_50%, and FEF_75%) < 65% predicted. Multivariate regression analysis was used to analyze factors associated with SAD diagnosed by only spirometry but not IOS (spirometry-only SAD) and only IOS but not spirometry (IOS-only SAD), and line regression was used to assess CT imaging differences. Results: There was a slight agreement between spirometry and IOS in the diagnosis of SAD (kappa 0.322, p < 0.001). Smoking status, phlegm, drug treatment, and family history of respiratory disease were factors leading to spirometry-only SAD. Spirometry-only SAD had more severe emphysema and gas-trapping than IOS-only SAD in abnormal lung function. However, in normal lung function subjects, there was no statistical difference in emphysema and gas-trapping between discordant groups. The number of IOS-only SAD was nearly twice than that of spirometry. Conclusion: IOS may be more sensitive than spirometry in the diagnosis of SAD in normal lung function subjects. But in patients with abnormal lung function, spirometry may be more sensitive than IOS to detect SAD patients with clinical symptoms and CT lesions.

Energy cost of walking and body composition changes during a 9-month multidisciplinary weight reduction program and 4-month follow-up in adolescents with obesity

The purpose of the present study was to investigate changes in the energy cost of locomotion during walking (Cw) related to changes in body mass (BM, kg) and body composition in adolescents with obesity. Twenty-six (12 boys and 14 girls) obese adolescents (mean: body mass index, 33.6 ± 3.7 kg·m-2; 42.7 ± 4.5% fat mass (FM)) followed a 9-month multidisciplinary inpatient weight-reduction program consisting of lifestyle education, moderate energy restriction, and regular physical activity in a specialised institution. At baseline (M0), the end of the 9-month program (M9), and after the 4-month follow-up (M13), oxygen consumption and carbon dioxide production of the standardised activity program were assessed by whole-body indirect calorimetry over 24 hours, and body composition was assessed by dual-energy X-ray absorptiometry. At M9, adolescents showed an 18% reduction in BM (p < 0.001) and 40% in total FM, while fat-free mass (kg) remained stable in boys but decreased by ∼6% in girls (p = 0.001). Similarly, the mean Cw decreased by 20% (p < 0.001). At M13, BM, FM, and Cw were slightly higher compared with at M9. In conclusion, moderate energy restriction and regular moderate physical activities improved walking economy, improved exercise tolerance, and induced beneficial changes in the body composition of adolescents with obesity. Novelty: Reduction of FM in the trunk region, and consequently reducing the work carried out by respiratory muscles, contributes to reducing Cw in adolescents with obesity. A lower walking cost can be effective in improving exercise tolerance and quality of life in obese adolescents.

Dynamic airway function during exercise in COPD assessed via impulse oscillometry before and after inhaled bronchodilators

Assessing airway function during exercise provides useful information regarding mechanical properties of the airways and the extent of ventilatory limitation in COPD. The primary aim of this study was to use impulse oscillometry (IOS) to assess dynamic changes in airway impedance across a range of exercise intensities in patients with GOLD 1-4, before and after albuterol administration. A secondary aim was to assess the reproducibility of IOS measures during exercise. Fifteen patients with COPD (8 males/7 females; age = 66 ± 8 yr; prebronchodilator FEV1 = 54.3 ± 23.6%Pred) performed incremental cycle ergometry before and 90 min after inhaled albuterol. Pulmonary ventilation and gas exchange were measured continuously, and IOS-derived indices of airway impedance were measured every 2 min immediately preceding inspiratory capacity maneuvers. Test-retest reproducibility of exercise IOS was assessed as mean difference between replicate tests in five healthy subjects (3 males/2 females). At rest and during incremental exercise, albuterol significantly increased airway reactance (X5) and decreased airway resistance (R5, R5-R20), impedance (Z5), and end-expiratory lung volume (60% ± 12% vs. 58% ± 12% TLC, main effect P = 0.003). At peak exercise, there were moderate-to-strong associations between IOS variables and IC, and between IOS variables and concavity in the expiratory limb of the spontaneous flow-volume curve. Exercise IOS exhibited moderate reproducibility in healthy subjects which was strongest with R5 (mean diff. = -0.01 ± 0.05 kPa/L/s; ICC = 0.68), R5-R20 (mean diff. = -0.004 ± 0.028 kPa/L/s; ICC = 0.65), and Z5 (mean diff. = -0.006 ± 0.021 kPa/L/s; ICC = 0.69). In patients with COPD, exercise evoked increases in airway resistance and decreases in reactance that were ameliorated by inhaled bronchodilators. The technique of exercise IOS may aid in the clinical assessment of dynamic airway function during exercise.NEW & NOTEWORTHY This study provides a novel, mechanistic insight into dynamic airway function during exercise in COPD, before and after inhaled bronchodilators. The use of impulse oscillometry (IOS) to evaluate airway function is unique among exercise studies. We show strong correlations among IOS variables, dynamic hyperinflation, and shape-changes in the spontaneous expiratory flow-volume curve. This approach may aid in the clinical assessment of airway function during exercise.

Current smoking alters phospholipid- and surfactant protein A levels in small airway lining fluid: An explorative study on exhaled breath

Small airways are difficult to access. Exhaled droplets, also referred to as particles, provide a sample of small airway lining fluid and may reflect inflammatory responses. We aimed to explore the effect of smoking on the composition and number of exhaled particles in a smoker-enriched study population. We collected and chemically analyzed exhaled particles from 102 subjects (29 never smokers, 36 former smokers and 37 current smokers) aged 39 to 83 years (median 63). A breathing maneuver maximized the number exhaled particles, which were quantified with a particle counter. The contents of surfactant protein A and albumin in exhaled particles was quantified with immunoassays and the contents of the phospholipids dipalmitoyl- and palmitoyl-oleoyl- phosphatidylcholine with mass spectrometry. Subjects also performed spirometry and nitrogen single breath washout. Associations between smoking status and the distribution of contents in exhaled particles and particle number concentration were tested with quantile regression, after adjusting for potential confounders. Current smokers, compared to never smokers, had higher number exhaled particles and more surfactant protein A in the particles. The magnitude of the effects of current smoking varied along the distribution of each PEx-variable. Among subjects with normal lung function, phospholipid levels were elevated in current smokers, in comparison to no effect of smoking on these lipids at abnormal lung function. Smoking increased exhaled number of particles and the contents of lipids and surfactant protein A in the particles. These findings might reflect early inflammatory responses to smoking in small airway lining fluid, also when lung function is within normal limits.

Asthma Phenotypes as a Guide for Current and Future Biologic Therapies

Asthma has been increasingly recognized as being a heterogeneous disease with multiple distinct mechanisms and pathophysiologies. Evidence continues to build regarding the existence of different cell types, environmental exposures, pathogens, and other factors that produce a similar set of symptoms known collectively as asthma. This has led to a movement from a "one size fits all" symptom-based methodology to a more patient-centered, individualized approach to asthma treatment targeting the underlying disease process. A significant contributor to this shift to more personalized asthma therapy has been the increasing availability of numerous biologic therapies in recent years, providing the opportunity for more targeted treatments. When targeted biologics began to be developed for treatment of asthma, the hope was that distinct biomarkers would become available, allowing the clinician to determine which biologic therapy was best suited for which patients. Presence of certain biomarkers, like eosinophilia or antigen-specific IgE, is important features of specific asthma phenotypes. Currently available biomarkers can help with decision making about biologics, but are generally too broad and non-specific to clearly identify an asthma phenotype or the single biologic best suited to an asthmatic. Identification of further biomarkers is the subject of intense research. Yet, identifying a patient's asthma phenotype can help in predicting disease course, response to treatment, and biologic therapies to consider. In this review, major asthma phenotypes are reviewed, and the evidence for the utility of various biologics, both those currently on the market and those in the development process, in each of these phenotypes is explored.

Impact of obesity on pulmonary function: current understanding and knowledge gaps

PURPOSE OF REVIEW

Obesity is an increasing world-wide public health concern. Obesity both causes respiratory symptoms and contributes to many cardiorespiratory diseases. The effects of obesity on commonly used lung function tests are reviewed.

RECENT FINDINGS

The effects of obesity on lung function are attributed both to mechanical factors and to complex metabolic effects that contribute to a pro-inflammatory state. The effects of obesity on lung function correlate with BMI and correlate even better when the distribution of excess adipose tissue is taken into account, with central obesity associated with more prominent abnormalities. Obesity is associated with marked decreases in expiratory reserve volume and functional residual capacity. Total lung capacity, residual volume, and spirometry are less affected by obesity and are generally within the normal range except with severe obesity. Obesity decreases total respiratory system compliance primarily because of decreased lung compliance, with only mild effects on chest wall compliance. Obesity is associated with impaired gas transfer with decreases in oxygenation and varied but usually mild effects on diffusing capacity for carbon monoxide, while the carbon monoxide transfer coefficient is often increased.

SUMMARY

Obesity has significant effects on lung function. The relative contribution of the mechanical effects of obesity and the production of inflammatory cytokines by adipose tissue on lung function needs further study.

Closing volume detection by single-breath gas washout and forced oscillation technique

Closing volume (CV) is commonly measured by single-breath nitrogen washout (CV_SBW). A method based on the forced oscillation technique was recently introduced to detect a surrogate CV (CV_FOT). As the two approaches are based on different physiological mechanisms, we aim to investigate CV_FOT and CV_SBW relationship at different degrees and patterns of airway obstruction. A mathematical model was developed to evaluate the CV_SBW and CV_FOT sensitivity to different patterns of airway obstruction, either located in a specific lung region or equally distributed throughout the lung. The two CVs were also assessed during slow vital capacity (VC) maneuvers in triplicate in 13 healthy subjects and pre- and postmethacholine challenge (Mch) in 12 subjects with mild-moderate asthma. Model simulations suggest that CV_SBW is more sensitive than CV_FOT to the presence of few flow-limited or closed airways that modify the contribution of tracer-poor and tracer-rich lung regions to the overall exhaled gas. Conversely, CV_FOT occurs only when at least ∼65% of lung units are flow limited or closed, regardless of their regional distribution. CV_SBW did not differ between healthy subjects and those with asthma (17 ± 9% VC vs. 22 ± 10% VC), whereas CV_FOT did (16 ± 5% VC vs. 23 ± 6% VC, P < 0.01). In patients with asthma, both CV_SBW and CV_FOT increased post-Mch (33 ± 7% VC P < 0.001 and 43 ± 12% VC P < 0.001, respectively). CV_SBW weakly correlated with CV_FOT (r = 0.45, P < 0.01). The closing capacities (CV + residual volume) were correlated (r = 0.74, P < 0.001), but the changes with Mch in both CVs and closing capacities did not correlate. CV_FOT is easy to measure and provides a reproducible parameter useful for describing airway impairment in obstructive respiratory diseases.NEW & NOTEWORTHY The forced oscillation technique can identify a surrogate of closing volume (CV_FOT). We investigated its relationship with the one measured by single-breath washout (CV_SBW). CV_FOT weakly correlates with CV_SBW. The respective closing capacities were correlated, but their increases after methacholine challenge in asthmatics did not. Our results suggest that CV_FOT is less sensitive than CV_SBW to few flow-limited/closed airways but more specific in detecting increases in flow-limited/closed airways involving the majority of the lung.

Perioperative Lung Protection: Clinical Implications

In the past, it was common practice to use a high tidal volume (VT) during intraoperative ventilation, because this reduced the need for high oxygen fractions to compensate for the ventilation-perfusion mismatches due to atelectasis in a time when it was uncommon to use positive end-expiratory pressure (PEEP) in the operating room. Convincing and increasing evidence for harm induced by ventilation with a high VT has emerged over recent decades, also in the operating room, and by now intraoperative ventilation with a low VT is a well-adopted approach. There is less certainty about the level of PEEP during intraoperative ventilation. Evidence for benefit and harm of higher PEEP during intraoperative ventilation is at least contradicting. While some PEEP may prevent lung injury through reduction of atelectasis, higher PEEP is undeniably associated with an increased risk of intraoperative hypotension that frequently requires administration of vasoactive drugs. The optimal level of inspired oxygen fraction (FIO2) during surgery is even more uncertain. The suggestion that hyperoxemia prevents against surgical site infections has not been confirmed in recent research. In addition, gas absorption-induced atelectasis and its association with adverse outcomes like postoperative pulmonary complications actually makes use of a high FIO2 less attractive. Based on the available evidence, we recommend the use of a low VT of 6-8 mL/kg predicted body weight in all surgery patients, and to restrict use of a high PEEP and high FIO2 during intraoperative ventilation to cases in which hypoxemia develops. Here, we prefer to first increase FIO2 before using high PEEP.

Effect of a preoperative single-dose steroid on pulmonary function and postoperative symptoms after modified radical mastectomy: results of a randomized clinical trial

Background

Evidence suggests that a preoperative single-dose steroid improves lung function and decreases the incidence of postoperative symptoms; however, this has not been sufficiently proved in modified radical mastectomy for cancer. This study aimed to evaluate the efficacy of preoperative single-dose steroid administration for postoperative lung function and postoperative symptoms in women undergoing modified radical mastectomy for breast cancer.

Methods

In this controlled clinical trial, conducted between June 2014 and October 2018, we examined 81 patients. Patients received a preoperative single dose of 8 mg dexamethasone (n=41; treatment group) or placebo (sterile injectable water; n=40; control group). We obtained data on postoperative nausea and vomiting and pain intensity and performed spirometry 1 h before and 1, 6, 12, and 24 h after surgery. The use of additional analgesic or antiemetic drugs was recorded. We followed up patients 30 days after discharge and recorded any surgical or medical complications.

Results

The age distribution and anthropometric variables of the two groups were similar. Almost 50% of the patients in each group also underwent breast reconstruction. In the treatment group, pain intensity was always lower, the incidence of postoperative nausea and vomiting was lower at 6, 12, and 24 h, and additional analgesics or antiemetics were required less frequently (P<0.05 for all). Both treatment and control groups demonstrated a restrictive ventilatory pattern immediately after surgery, which in the treatment group was reversed after 24 h. However, the reconstructed patients had a more intense and prolonged restrictive pattern (P<0.05). Surgical morbidity included one seroma observed in the control group. No infections occurred at the surgical site or at any other level, and no patient developed any metabolic disorder. No mortality was observed in either group.

Conclusions

This study establishes that a single preoperative dose of dexamethasone markedly decreased the incidence of postoperative nausea and vomiting and pain, improved respiratory parameters, and decreased the need for additional postoperative analgesic or antiemetic drugs.

Clinical Trial Registration

ClinicalTrials.gov (ID NCT02305173).

<p>Evaluation of the Small Airways in Patients with Chronic Obstructive Pulmonary Disease and Alpha-1 Antitrypsin Deficiency</p>

Introduction

Small airways are not evaluated with traditional pulmonary function tests. The aim of this study was to evaluate the small airways in patients with chronic obstructive pulmonary disease (COPD) with a nitrogen washout test and to verify whether there is a difference between patients with COPD due to smoking and those with COPD due to alpha-1 antitrypsin mutation.

Methods

Sixteen patients with mutation in the SERPINA1 gene and 45 patients with no mutation were included in this cross-sectional study. All pulmonary function tests, including the single breath nitrogen washout test, were performed for all patients and alpha-1 antitrypsin dosage was assessed with immunonephelometry.

Results

A comparison of patients with COPD due to smoking and those with COPD due to smoking and mutation revealed a significant difference in closure volume (%), which was the poorest in the mutation group. In the group with COPD and mutation, there was an inverse correlation between smoking and closure volume (%). We also verified that similar to forced expiratory volume in the first second (FEV1), the phase III slope (%) and ΔN2 750–1250 mL (%) could be used to differentiate the severity of airflow limitation.

Conclusion

Our results suggest that both variables, phase III slope and the ΔN2 750–1250 mL (%), could be related to COPD severity. Therefore, alterations at the distribution of the location of the emphysema could alter the results of closer volume and that the nitrogen washout test is more sensitive when compared to traditional pulmonary function test in evaluating COPD patients.

Sublobar resection: functional evaluation and pathophysiological considerations

To date, pulmonary function tests (PFTs) are part of consolidated standard operating procedures in thoracic surgery. PFTs are usually used to assess the pre-operative risk, post-operative outcomes and complications after pulmonary resections. The only functional parameter used in common practice is the forced expiratory volume in one second (FEV₁). However, the FEV₁ alone poorly reflects lung pathophysiology, especially in patients with pre-operative emphysema and airflow obstruction; moreover, the predictive power of spirometric parameters in guiding the surgical approach in terms of the extension of the excision is currently unknown. In the present critical overview, we report and discuss the results of four studies that compared pre and post-surgery FEV₁ and forced vital capacity (FVC) in patients undergoing lobectomy or segmentectomy, highlighting the critical aspects of spirometry in lung surgery and suggesting new approaches for the interpretation of pulmonary mechanics in patients undergoing major or minor parenchymal resections. Overall, the literature on the topic is limited to spirometric parameters, and post-surgical function loss and the consequent recovery are often analysed in inhomogeneous study samples, with varying respiratory comorbidities and functional phenotypes. We underline the role of static lung volumes in the patients’ initial assessment. In fact, they tend to decrease in patients with emphysema that undergo a lobectomy, followed by a decrease in lung compliance; some of these patients experience also an increase in closing volume, a condition that worsens the stresses implicated in lung ventilation and promotes the damage to the remaining airways. Spirometric data should be therefore always associated to body-plethysmography and indexes of ventilation distribution, to improve the evaluation of the functional characteristics in patients undergoing lung surgery. Prospective studies are needed to establish the relationship and long-term consequences of different surgical approaches in terms of lung mechanics and functional loss.

Efficacy and Safety of a Pressurized Metered-Dose Inhaler in Older Asthmatics: Comparison to a Dry Powder Inhaler in a 12-Week Randomized Trial

Purpose

Asthma control in older asthmatics is often less effective, which may be attributed to small airway dysfunction and poor inhalation technique. We compared the efficacy of 2 inhalers (fluticasone propionate/formoterol treatment using a pressurized metered-dose inhaler [p-MDI group] vs. fluticasone propionate/salmeterol treatment using a dry powder inhaler [DPI group]) in older asthmatics.

Methods

We conducted a 12-week, randomized, open-label, parallel-designed trial in older patients (over 55 years old) with moderate-to-severe asthma, and compared the efficacy and safety for asthma control between the 2 groups. Subgroup analyses on disease duration and air trapping were performed. Clinical parameters, including changes in lung function parameters, inhaler technique and adherence, were compared with monitoring adverse reactions between the 2 groups.

Results

A total of 68 patients underwent randomization, and 63 (30 in the p-MDI group and 33 in the DPI group) completed this study. The p-MDI group was non-inferior to the DPI group with regard to the rate of well-controlled asthma (53.3% vs. 45.5%, P < 0.001; a predefined non-inferiority limit of 17%). In subgroup analyses, the proportion of patients who did not reach well-controlled asthma in the p-MDI group was non-inferior to that in the DPI group; the difference was 12.7% among those with a longer disease duration (≥ 15 years) and 17.5% among those with higher air-trapping (RV/TLC ≥ 45%), respectively (a predefined non-inferiority limit of 17%, P < 0.001). No significant differences were observed in lung function parameters, inhalation techniques, adherence and adverse reactions between the 2 groups.

Conclusion

These results suggest that the p-MDI group may be comparable to the DPI group in the management of older asthmatics in aspects of efficacy and safety.

Respiratory system reactance reflects communicating lung volume in chronic obstructive pulmonary disease

Respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) is theoretically and experimentally related to lung volume. In chronic obstructive pulmonary disease (COPD), the absolute volume measured by body plethysmography includes a proportion that is inaccessible to pressure oscillations applied via the mouth, that is, a "noncommunicating" lung volume. We hypothesized that in COPD the presence of noncommunicating lung would disrupt the expected Xrs-volume relationship compared with plethysmographic functional residual capacity (FRC_pleth). Instead, Xrs would relate to estimates of communicating volume, namely, expiratory reserve volume (ERV) and single-breath alveolar volume (Va_SB). We examined FOT and lung function data from people with COPD (n = 51) and from healthy volunteers (n = 40). In healthy volunteers, we observed an expected inverse relationship between reactance at 5 Hz (X5) and FRC_pleth. In contrast, there was no such relationship between X5 and FRC_pleth in COPD subjects. However, there was an inverse relationship between X5 and both ERV and Va_SB. Hence the theoretical Xrs-volume relationship is present in COPD but only when considering the communicating volume rather than the absolute lung volume. These findings confirm the role of reduced communicating lung volume as an important determinant of Xrs and therefore advance our understanding and interpretation of FOT measurements in COPD. NEW & NOTEWORTHY To investigate the determinants of respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) in chronic obstructive pulmonary disease (COPD), we examine the relationship between Xrs and lung volume. We show that Xrs does not relate to absolute lung volume (functional residual capacity) in COPD but instead relates only to the volume of lung in communication with the airway opening. This communicating volume may therefore be fundamental to our interpretation of FOT measurements in COPD and other pulmonary diseases.

Early onset of airway derecruitment assessed using the forced oscillation technique in subjects with asthma

Derecruitment of air spaces in the lung occurs when airways close during exhalation and is related to ventilation heterogeneity and symptoms in asthma. The forced oscillation technique has been used to identify surrogate measures of airway closure via the reactance (Xrs) versus lung volume relationship. This study used a new algorithm to identify derecruitment from the Xrs versus lung volume relationship from a slow vital capacity maneuver. We aimed to compare two derecruitment markers on the Xrs versus volume curve, the onset reduction of Xrs (DR1_vol) and the onset of more rapid reduction of Xrs (DR2_vol), between control and asthmatic subjects. We hypothesized that the onset of DR1_vol and DR2_vol occurred at higher lung volume in asthmatic subjects. DR1_vol and DR2_vol were measured in 18 subjects with asthma and 18 healthy controls, and their relationships with age and height were examined using linear regression. In the control group, DR1_vol and DR2_vol increased with age (r² = 0.68, P < 0.001 and r² = 0.71, P < 0.001, respectively). DR1_vol and DR2_vol in subjects with asthma [76.58% of total lung capacity (TLC) and 56.79%TLC, respectively] were at higher lung volume compared with control subjects (46.1 and 37.69%TLC, respectively) (P < 0.001). DR2_vol correlated with predicted values of closing capacity (r = 0.94, P < 0.001). This study demonstrates that derecruitment occurs at two points along the Xrs-volume relationship. Both derecruitment points occurred at significantly higher lung volumes in subjects with asthma compared with healthy control subjects. This technique offers a novel way to measure the effects of changes in airways/lung mechanics. NEW & NOTEWORTHY This study demonstrates that the forced oscillation technique can be used to identify two lung volume points where lung derecruitment occurs: 1) where derecruitment is initiated and 2) where onset of rapid derecruitment commences. Measurements of derecruitment increase with age. The onset of rapid derecruitment was highly correlated with predicted closing capacity. Also, the initiation and rate of derecruitment are significantly altered in subjects with asthma.

Exhaled particles and small airways

BACKGROUND

Originally, studies on exhaled droplets explored properties of airborne transmission of infectious diseases. More recently, the interest focuses on properties of exhaled droplets as biomarkers, enabled by the development of technical equipment and methods for chemical analysis. Because exhaled droplets contain nonvolatile substances, particles is the physical designation. This review aims to outline the development in the area of exhaled particles, particularly regarding biomarkers and the connection with small airways, i e airways with an internal diameter < 2 mm.

MAIN BODY

Generation mechanisms, sites of origin, number concentrations of exhaled particles and the content of nonvolatile substances are studied. Exhaled particles range in diameter from 0.01 and 1000 μm depending on generation mechanism and site of origin. Airway reopening is one scientifically substantiated particle generation mechanism. During deep expirations, small airways close and the reopening process produces minute particles. When exhaled, these particles have a diameter of < 4 μm. A size discriminating sampling of particles < 4 μm and determination of the size distribution, allows exhaled particle mass to be estimated. The median mass is represented by particles in the size range of 0.7 to 1.0 μm. Half an hour of repeated deep expirations result in samples in the order of nanogram to microgram. The source of these samples is the respiratory tract ling fluid of small airways and consists of lipids and proteins, similarly to surfactant. Early clinical studies of e g chronic obstructive pulmonary disease and asthma, reported altered particle formation and particle composition.

CONCLUSION

The physical properties and content of exhaled particles generated by the airway reopening mechanism offers an exciting noninvasive way to obtain samples from the respiratory tract lining fluid of small airways. The biomarker potential is only at the beginning to be explored.

The effect of obesity on lung function

INTRODUCTION

There is a major epidemic of obesity, and many obese patients suffer with respiratory symptoms and disease. The overall impact of obesity on lung function is multifactorial, related to mechanical and inflammatory aspects of obesity. Areas covered: Obesity causes substantial changes to the mechanics of the lungs and chest wall, and these mechanical changes cause asthma and asthma-like symptoms such as dyspnea, wheeze, and airway hyperresponsiveness. Excess adiposity is also associated with increased production of inflammatory cytokines and immune cells that may also lead to disease. This article reviews the literature addressing the relationship between obesity and lung function, and studies addressing how the mechanical and inflammatory effects of obesity might lead to changes in lung mechanics and pulmonary function in obese adults and children. Expert commentary: Obesity has significant effects on respiratory function, which contribute significantly to the burden of respiratory disease. These mechanical effects are not readily quantified with conventional pulmonary function testing and measurement of body mass index. Changes in mediators produced by adipose tissue likely also contribute to altered lung function, though as of yet this is poorly understood.

Comparison of two methods of determining lung de-recruitment, using the forced oscillation technique

Airway closure has proved to be important in a number of respiratory diseases and may be the primary functional defect in asthma. A surrogate measure of closing volume can be identified using the forced oscillation technique (FOT), by performing a deflation maneuver and examining the resultant reactance (Xrs) lung volume relationship. This study aims to determine if a slow vital capacity maneuver can be used instead of this deflation maneuver and compare it to existing more complex techniques. Three subject groups were included in the study; healthy (n = 29), asthmatic (n = 18), and COPD (n = 10) for a total of 57 subjects. Reactance lung volume curves were generated via FOT recordings during two different breathing manoeuvres (both pre and post bronchodilator). The correlation and agreement between surrogate closing volume (Vol_crit) and reactance (Xrs_crit) at this volume was analysed. The changes in Vol_crit and Xrs_crit pre and post bronchodilator were also analysed. Across all three subject groups, the two different measures of Vol_crit were shown to be statistically equivalent (p > 0.05) and demonstrated a strong fit to the data (R² = 0.49, 0.78, 0.59, for asthmatic, COPD and healthy subject groups, respectively). A bias was evident between the two measurements of Xrs_crit with statistically different means (p < 0.05). However, the two measurements of Xrs_crit displayed the same trends. In conclusion, we have developed an alternative technique for measuring airway closure from FOT recordings. The technique delivers equivalent and possibly more sensitive results to previous methods while being simple and easily performed by the patient.

The impact of aging on outpatients with asthma in a real-world setting

BACKGROUND

Asthma is characterized by airway inflammation and bronchial hyperreactivity. It is conceived that aging may affect asthma characteristics, but this issue is still not completely clarified in clinical practice.

OBJECTIVE

The present study investigated whether aging may affect some clinical and functional factors in outpatients with asthma visited in a real-world setting, such as clinical practice.

METHODS

Globally, 391 outpatients (163 males, median age 47 years) with asthma were consecutively evaluated. The following parameters were assessed: history, including, smoking, comorbidity, and inhaled corticosteroids (ICS) use, physical examination, body mass index (BMI), lung function, level of asthma control, asthma control test (ACT), and fractional exhaled NO (FeNO).

RESULTS

The elderly with asthma had: more frequently not controlled asthma, higher BMI, higher ICS dosages, more impaired lung function, including plethysmographic parameters, than adult asthmatics (p < 0.001 for all, but p = 0.002 for RV and p = 0.008 for FRC). Elderly asthmatics were also less frequently allergic (p < 0.001) and had less rhinitis comorbidity (p < 0.001) and less nasal symptoms (p < 0.05) than younger asthmatics.

CONCLUSIONS

The present study conducted in a real-world setting shows that aging significantly affects asthma, mainly concerning asthma control, lung function, and steroid-sensitivity.

Chronic obstructive pulmonary disease with mild airflow limitation: current knowledge and proposal for future research - a consensus document from six scientific societies

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity worldwide, with high and growing prevalence. Its underdiagnosis and hence under-treatment is a general feature across all countries. This is particularly true for the mild or early stages of the disease, when symptoms do not yet interfere with daily living activities and both patients and doctors are likely to underestimate the presence of the disease. A diagnosis of COPD requires spirometry in subjects with a history of exposure to known risk factors and symptoms. Postbronchodilator forced expiratory volume in 1 second (FEV₁)/forced vital capacity <0.7 or less than the lower limit of normal confirms the presence of airflow limitation, the severity of which can be measured by FEV₁% predicted: stage 1 defines COPD with mild airflow limitation, which means postbronchodilator FEV₁ ≥80% predicted. In recent years, an elegant series of studies has shown that "exclusive reliance on spirometry, in patients with mild airflow limitation, may result in underestimation of clinically important physiologic impairment". In fact, exercise tolerance, diffusing capacity, and gas exchange can be impaired in subjects at a mild stage of airflow limitation. Furthermore, growing evidence indicates that smokers without overt abnormal spirometry have respiratory symptoms and undergo therapy. This is an essential issue in COPD. In fact, on one hand, airflow limitation, even mild, can unduly limit the patient's physical activity, with deleterious consequences on quality of life and even survival; on the other hand, particularly in younger subjects, mild airflow limitation might coincide with the early stage of the disease. Therefore, we thought that it was worthwhile to analyze further and discuss this stage of "mild COPD". To this end, representatives of scientific societies from five European countries have met and developed this document to stimulate the attention of the scientific community on COPD with "mild" airflow limitation. The aim of this document is to highlight some key features of this important concept and help the practicing physician to understand better what is behind "mild" COPD. Future research should address two major issues: first, whether mild airflow limitation represents an early stage of COPD and what the mechanisms underlying the evolution to more severe stages of the disease are; and second, not far removed from the first, whether regular treatment should be considered for COPD patients with mild airflow limitation, either to prevent progression of the disease or to encourage and improve physical activity or both.

Acute effects of long-acting bronchodilators on small airways detected in COPD patients by single-breath N2 test and lung P-V curve

Small airways represent the key factor of chronic obstructive pulmonary disease (COPD) pathophysiology. The effect of different classes of bronchodilators on small airways is still poorly understood and difficult to assess. Hence the acute effects of tiotropium (18 µg) and indacaterol (150 µg) on closing volume (CV) and ventilation inhomogeneity were investigated and compared in 51 stable patients (aged 70 ± 7 yr, mean ± SD; 82% men) with moderate to very severe COPD. Patients underwent body plethysmography, arterial blood gas analysis, tidal expiratory flow limitation (EFL), dyspnea assessment, and simultaneous recording of single-breath N₂ test and transpulmonary pressure-volume curve (P_L-V), before and 1 h after drug administration. The effects produced by indacaterol on each variable did not differ from those caused by tiotropium, independent of the severity of disease, assessed according to the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) scale and the presence of EFL. Bronchodilators significantly decreased the slope of phase III and CV (-5 ± 4 and -2.5 ± 2.1%, respectively, both P < 0.001), with an increase in both slope and height of phase IV and of the anatomical dead space. Arterial oxygen pressure and saturation significantly improved (3 ± 3 mmHg and 2 ± 2%, respectively, both P < 0.001); their changes negatively correlated with those of phase III slope (r = -0.659 and r = -0.454, respectively, both P < 0.01). The vital capacity (VC) increased substantially, but the P_L-V/VC curve above CV was unaffected. In conclusion, bronchodilators reduce the heterogeneity of peripheral airway mechanical properties and the extent of their closure, with minor effects on critical closing pressure. This should lessen the risk of small-airway damage and positively affect gas exchange.NEW & NOTEWORTHY This is the first study investigating in stable chronic obstructive pulmonary disease patients the acute effects of two long-acting bronchodilators, a β-agonist and a muscarinic antagonist, on peripheral airways using simultaneous lung pressure-volume curve and single-breath N₂ test. By lessening airway mechanical property heterogeneity, both drugs similarly reduced ventilation inhomogeneity and extent of small-airway closure, as indicated by the decrease of phase III slope, increased oxygen saturation, and fall of closing volume, often below expiratory reserve volume.

Effects of preoperative dexamethasone on postoperative pain, nausea, vomiting and respiratory function in women undergoing conservative breast surgery for cancer: Results of a controlled clinical trial

The objective was to evaluate whether preoperative administration of dexamethasone improved postoperative nausea and vomiting (PONV), pain and respiratory function tests in women undergoing conservative surgery for breast cancer. This was a controlled clinical trial conducted between June 2013 and October 2014. Eighty patients were evaluated. Patients received a preoperative dose of 8 mg of dexamethasone (n = 40) or placebo (n = 40). The data on PONV and pain intensity was obtained and forced spirometry tests were performed, 1 hr before and at 1, 6, 12 and 24 hr after surgery. Any use of additional analgesic/antiemetic drugs was recorded. Patients were followed until 30 days after surgery for any surgical or medical complications. The pain intensity was lower in the treatment group for all periods; PONV was lower at 6, 12 and 24 hr; Additional analgesics/antiemetics were required less frequently (all p < .05). Both groups exhibited a restrictive ventilatory pattern immediately after surgery, which was reversed in the following hours. However, spirometric values were higher in the dexamethasone group. There were no pulmonary or metabolic complications after surgery. Our conclusions were that dexamethasone significantly reduced the incidences of PONV, pain and improved respiratory parameters, and reduced the need for additional postoperative analgesic and antiemetic drugs.

Controlled invasive mechanical ventilation strategies in obese patients undergoing surgery

INTRODUCTION

The obesity prevalence is increasing in surgical population. As the number of obese surgical patients increases, so does the demand for mechanical ventilation. Nevertheless, ventilatory strategies in this population are challenging, since obesity results in pathophysiological changes in respiratory function. Areas covered: We reviewed the impact of obesity on respiratory system and the effects of controlled invasive mechanical ventilation strategies in obese patients undergoing surgery. To date, there is no consensus regarding the optimal invasive mechanical ventilation strategy for obese surgical patients, and no evidence that possible intraoperative beneficial effects on oxygenation and mechanics translate into better postoperative pulmonary function or improved outcomes. Expert commentary: Before determining the ideal intraoperative ventilation strategy, it is important to analyze the pathophysiology and comorbidities of each obese patient. Protective ventilation with low tidal volume, driving pressure, energy, and mechanical power should be employed during surgery; however, further studies are required to clarify the most effective ventilation strategies, such as the optimal positive end-expiratory pressure and whether recruitment maneuvers minimize lung injury. In this context, an ongoing trial of intraoperative ventilation in obese patients (PROBESE) should help determine the mechanical ventilation strategy that best improves clinical outcome in patients with body mass index≥35kg/m².

The physiological basis and clinical significance of lung volume measurements

From a physiological standpoint, the lung volumes are either dynamic or static. Both subclasses are measured at different degrees of inspiration or expiration; however, dynamic lung volumes are characteristically dependent on the rate of air flow. The static lung volumes/capacities are further subdivided into four standard volumes (tidal, inspiratory reserve, expiratory reserve, and residual volumes) and four standard capacities (inspiratory, functional residual, vital and total lung capacities). The dynamic lung volumes are mostly derived from vital capacity. While dynamic lung volumes are essential for diagnosis and follow up of obstructive lung diseases, static lung volumes are equally important for evaluation of obstructive as well as restrictive ventilatory defects. This review intends to update the reader with the physiological basis, clinical significance and interpretative approaches of the standard static lung volumes and capacities.

Airway occlusion assessed by single breath N2 test and lung P-V curve in healthy subjects and COPD patients

PURPOSE

To determine whether the analysis of the slow expiratory transpulmonary pressure-volume (P_L-V) curve provides an alternative to the single-breath nitrogen test (SBN) for the assessment of the closing volume (CV).

METHODS

SBN test and slow deflation P_L-V curve were simultaneously recorded in 40 healthy subjects and 43 COPD patients. Onset of phase IV identified CV in SBN test (CV_SBN), whereas in the P_L-V curve CV was identified by: a) deviation from the exponential fit (CV_exp), and b) inflection point of the interpolating sigmoid function (CV_sig).

RESULTS

In the absence of phase IV, COPD patients exhibited a clearly discernible inflection in the P_L-V curve. In the presence of phase IV, CV_SBN and CV_exp coincided (CV_SBN/CV_exp=1.04±0.04 SD), whereas CV_sig was systematically larger (CV_sig/CV_exp=2.1±0.86).

CONCLUSION

The coincidence between CV_SBN and CV_exp, and the presence of the inflection in the absence of phase IV indicate that the deviation of the P_L-V curve from the exponential fit reliably assesses CV.

Effect of weight loss on operational lung volumes and oxygen cost of breathing in obese women

BACKGROUND

The effects of moderate weight loss on operational lung volumes during exercise and the oxygen (O2) cost of breathing are unknown in obese women but could have important implications regarding exercise endurance.

METHODS

In 29 obese women (33±8 years, 97±14 kg, body mass index: 36±4 kg m(-2), body fat: 45.6±4.5%; means±s.d.), body composition, fat distribution (by magnetic resonance imaging), pulmonary function, operational lung volumes during exercise and the O2 cost of breathing during eucapnic voluntary hyperpnea (([Vdot ]O2) vs ([Vdot ]E) slope) were studied before and after a 12-week diet and resistance exercise weight loss program.

RESULTS

Participants lost 7.5±3.1 kg or ≈8% of body weight (P<0.001), but fat distribution remained unchanged. After weight loss, lung volume subdivisions at rest were increased (P<0.05) and were moderately associated (P<0.05) with changes in weight. End-expiratory lung volume (percentage of total lung capacity) increased at rest and during constant load exercise (P<0.05). O2 cost of breathing was reduced by 16% (2.52±1.02-2.11±0.72 ml l(-1); P=0.003). As a result, O2 uptake of the respiratory muscles ([Vdot ]O2Resp), estimated as the product of O2 cost of breathing and exercise ([Vdot ]E) during cycling at 60 W, was significantly reduced by 27±31 ml (P<0.001), accounting for 46% of the reduction in total body ([Vdot ]O2) during cycling at 60 W.

CONCLUSIONS

Moderate weight loss yields important improvements in respiratory function at rest and during submaximal exercise in otherwise healthy obese women. These changes in breathing load could have positive effects on the exercise endurance and adherence to physical activity.

Bronchial involvement in advanced stage lymphangioleiomyomatosis: histopathologic and molecular analyses

Lymphangioleiomyomatosis (LAM), a rare progressive disease that almost exclusively affects women, is characterized by pulmonary cysts and neoplastic proliferation of smooth muscle-like cells (LAM cells). Airflow obstruction is a physiologic consequence that is commonly observed in LAM and has been attributed to narrowing of peripheral airways. However, histopathologic examinations of the entire airway have been precluded by the limited availability of such specimens. Here, we used explanted lung tissues from 30 LAM patients for a thorough histologic analysis with a special emphasis on the bronchi. We found bronchial involvement by LAM cells and lymphatics in all patients examined. Furthermore, a moderate to severe degree of chronic inflammation (73%), goblet cell hyperplasia (97%), squamous cell metaplasia (83%) of the epithelium, and thickening of basal lamina (93%) were identified in the bronchi. Because LAM cells are transformed by the functional loss of the TSC genes leading to a hyperactivated mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, we confirmed the expression of phospho-p70S6K, phospho-S6, phospho-4E-BP1, and vascular endothelial growth factor (VEGF)-D in LAM cells from all of the patients examined. In contrast, no protein expression of hypoxia-inducible factor 1α, a downstream molecule indicative of mTORC1 activation and leading to VEGF production, was detected in any patient. Our study indicates that late-stage LAM patients commonly have bronchi involved by the proliferation of both LAM cells and lymphatics and that chronic inflammation complicated their disease. Furthermore, the up-regulation of hypoxia-inducible factor 1α, a common event in mTORC1-driven tumor cells, does not occur in LAM cells and plays no role in VEGF-D expression in LAM cells.

Intraoperative protective mechanical ventilation for prevention of postoperative pulmonary complications: a comprehensive review of the role of tidal volume, positive end-expiratory pressure, and lung recruitment maneuvers

Postoperative pulmonary complications are associated with increased morbidity, length of hospital stay, and mortality after major surgery. Intraoperative lung-protective mechanical ventilation has the potential to reduce the incidence of postoperative pulmonary complications. This review discusses the relevant literature on definition and methods to predict the occurrence of postoperative pulmonary complication, the pathophysiology of ventilator-induced lung injury with emphasis on the noninjured lung, and protective ventilation strategies, including the respective roles of tidal volumes, positive end-expiratory pressure, and recruitment maneuvers. The authors propose an algorithm for protective intraoperative mechanical ventilation based on evidence from recent randomized controlled trials.

Obesity and Pulmonary Function in African Americans

Background

Obesity prevalence in United States (US) adults exceeds 30% with highest prevalence being among blacks. Obesity is known to have significant effects on respiratory function and obese patients commonly report respiratory complaints requiring pulmonary function tests (PFTs). However, there is no large study showing the relationship between body mass index (BMI) and PFTs in healthy African Americans (AA).

Objective

To determine the effect of BMI on PFTs in AA patients who did not have evidence of underlying diseases of the respiratory system.

Methods

We reviewed PFTs of 339 individuals sent for lung function testing who had normal spirometry and lung diffusion capacity for carbon monoxide (DLCO) with wide range of BMI.

Results

Functional residual capacity (FRC) and expiratory reserve volume (ERV) decreased exponentially with increasing BMI, such that morbid obesity resulted in patients breathing near their residual volume (RV). However, the effects on the extremes of lung volumes, at total lung capacity (TLC) and residual volume (RV) were modest. There was a significant linear inverse relationship between BMI and DLCO, but the group means values remained within the normal ranges even for morbidly obese patients.

Conclusions

We showed that BMI has significant effects on lung function in AA adults and the greatest effects were on FRC and ERV, which occurred at BMI values < 30 kg/m2. These physiological effects of weight gain should be considered when interpreting PFTs and their effects on respiratory symptoms even in the absence of disease and may also exaggerate existing lung diseases.

Asthma Is More Severe in Older Adults

Background

Severe asthma occurs more often in older adult patients. We hypothesized that the greater risk for severe asthma in older individuals is due to aging, and is independent of asthma duration.

Methods

This is a cross-sectional study of prospectively collected data from adult participants (N=1130; 454 with severe asthma) enrolled from 2002 – 2011 in the Severe Asthma Research Program.

Results

The association between age and the probability of severe asthma, which was performed by applying a Locally Weighted Scatterplot Smoother, revealed an inflection point at age 45 for risk of severe asthma. The probability of severe asthma increased with each year of life until 45 years and thereafter increased at a much slower rate. Asthma duration also increased the probability of severe asthma but had less effect than aging. After adjustment for most comorbidities of aging and for asthma duration using logistic regression, asthmatics older than 45 maintained the greater probability of severe asthma [OR: 2.73 (95 CI: 1.96; 3.81)]. After 45, the age-related risk of severe asthma continued to increase in men, but not in women.

Conclusions

Overall, the impact of age and asthma duration on risk for asthma severity in men and women is greatest over times of 18-45 years of age; age has a greater effect than asthma duration on risk of severe asthma.