Airway Closure and Expiratory Flow Limitation in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is mostly characterized by the loss of aerated lung volume associated with an increase in lung tissue and intense and complex lung inflammation. ARDS has long been associated with the histological pattern of diffuse alveolar damage (DAD). However, DAD is not the unique pathological figure in ARDS and it can also be observed in settings other than ARDS. In the coronavirus disease 2019 (COVID-19) related ARDS, the impairment of lung microvasculature has been pointed out. The airways, and of notice the small peripheral airways, may contribute to the loss of aeration observed in ARDS. High-resolution lung imaging techniques found that in specific experimental conditions small airway closure was a reality. Furthermore, low-volume ventilator-induced lung injury, also called as atelectrauma, should involve the airways. Atelectrauma is one of the basic tenet subtending the use of positive end-expiratory pressure (PEEP) set at the ventilator in ARDS. Recent data revisited the role of airways in humans with ARDS and provided findings consistent with the expiratory flow limitation and airway closure in a substantial number of patients with ARDS. We discussed the pattern of airway opening pressure disclosed in the inspiratory volume-pressure curves in COVID-19 and in non-COVID-19 related ARDS. In addition, we discussed the functional interplay between airway opening pressure and expiratory flow limitation displayed in the flow-volume curves. We discussed the individualization of the PEEP setting based on these findings.

Small Airway Dysfunction in Cough Variant Asthma: Prevalence, Clinical, and Pathophysiological Features

Introduction: Small airway dysfunction (SAD) commonly presents in patients with classic asthma, which is associated with airway inflammation, disease severity, and asthma control. However, the prevalence of SAD, its relationship with cough severity and airway inflammation, and its development after antiasthmatic treatment in patients with cough variant asthma (CVA) need to be clarified. This study aimed to investigate the prevalence of SAD and its relationship with clinical and pathophysiological characteristics in patients with CVA and the change in small airway function after antiasthmatic treatment.Methods: We retrospectively analyzed 120 corticosteroid-naïve patients with CVA who had finished a standard questionnaire and relevant tests in a specialist cough clinic, such as cough visual analog scale (VAS), differential cells in induced sputum, fractional exhaled nitric oxide (FeNO) measurement, spirometry, and airway hyper-responsiveness. Information of 1-year follow-up was recorded in a part of patients who received complete cough relief after 2 months of treatment. SAD was defined as any two parameters of maximal mid-expiratory flow (MMEF)% pred, forced expiratory flow at 50% of forced vital capacity (FEF50%) pred, and forced expiratory flow at 75% of forced vital capacity (FEF75%) pred measuring <65%.Results: SAD occurred in 73 (60.8%) patients with CVA before treatment. The patients with SAD showed a significantly longer cough duration (24.0 vs. 6.0, p = 0.031), a higher proportion of women (78.1 vs. 59.6%, p = 0.029), older mean age (41.9 vs. 35.4, p = 0.005), and significantly lower forced expiratory volume in 1 s (FEV1%) pred, FEV1/FVC, MMEF% pred, FEF50% pred, FEF75% pred, PEF% pred, and PD20 (all p < 0.01) as compared with patients without SAD. There were no significant differences in cough VAS, sputum eosinophils count, FeNO, and TIgE level between patients with SAD and those without SAD. Among 105 patients who completed 2 months of antiasthmatic treatment and repeatedly experienced spirometry measurement, 57 (54.3%) patients still had SAD, despite a significant improvement in cough VAS, sputum eosinophils, FeNO, FEF50% pred, and PEF% pred (all p < 0.01). As compared with patients without SAD, patients with SAD showed no significant differences in the relapse rate (50.0 vs. 41.9%, p = 0.483) and wheeze development rate (10.4 vs. 0%, p = 0.063) during the follow-up.Conclusions: Small airway dysfunction occurred in over half of patients with CVA and persisted after short-term antiasthmatic treatment, which showed distinctive clinical and pathophysiological features.

Assessment of Peak Expiratory Flow Rate in Spice Mill Workers - A Cross-Sectional Study

Background: Numerous industries have researched the effects of occupational dust and particles on respiratory function. The continuous exposure to dispersed particles causes respiratory ailments in spice mill workers. Spice dust exposure is linked to a systemic inflammatory response, including respiratory irritation. Spice dust is finely divided solid particles and a form of respirable dust this is the leading cause of occupational disease. Allergies and asthma have been linked to spice mill workers. Objective: To study the effect of spice dust exposure on expiratory function and to compare the peak expiratory flow rate of spice mill workers and normal adults across age groups and gender Method: 186 subjects in Mumbai region, 93 spice mill workers and 93 normal adults were selected as per inclusion and exclusion criteria. PEFR was measured in all the participants using a mini Wright peak flow meter. Result: The statistical analysis showed that there is a significant difference in the peak expiratory flow rates of spice mill workers. However, intergroup analysis between age groups showed that there was not much difference in the PEFR values for the age group 40-50 when compared with normal. The reason could be less number of participants available for the study. Also, the gender-wise comparison showed statistically significant difference in male and female PEFR values. Conclusion: The present study concluded that peak expiratory flow rate was significantly reduced in spice mill workers when compared to normal adults of same age. Key words: PEFR, spice mill workers, spice dust, allergies.

Association Between Blood Pressure And Lung Function In Chinese Children: The Seven Northeastern Cities Study

Background: A global increase in asthma and COPD incidence has occurred, the cause is unknown. One potential relationship that has yet to be explored is the interaction between blood pressure (BP) and lung function in children 5-17 years old. Our purpose is to assess the relationship between hypotension, hypertension, and lung function in children 5 to 17 years old. Methods: Participants were recruited from elementary and middle schools from 7 cities in northeastern China (N=6,797). BP was categorized into 3 groups: hypotensive (<5th percentile or <90mmHg if children >10 years), normotensive and hypertensive (>95th percentile) based on American Academy of Pediatrics standards. Spirometry measured lung function in forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow (PEF), and maximum mid expiratory flow (MMEF). Associations were assessed using logistic regression analysis. Results: Decreases in FVC , FEV1, PEF, and MMEF were noted in hypotensive children. Higher FVC, FEV1, PEF, and MMEF were noted among children ³ 10 with hypertension, while children <10 years, only had increased FVC compared to normotensive children. Statistically significant interactions between hypotension and PEF < 75% (OR:2.31; 95% CI: 1.17-4.23), were seen for children < 10 years. Conclusions: Our findings suggest that, in this study population, hypotension may be associated with decreased lung function, and the increased lung function may be associated with hypertension in children. Future studies are needed to confirm temporality as this is the first study to explore these relationships in children which requires in depth investigation.

Effects of Physical Exercises on Pulmonary Rehabilitation, Exercise Capacity, and Quality of Life in Children with Asthma: A Meta-Analysis

Objective. This study aimed to systematically evaluate the effect of exercise on pulmonary function, exercise capacity, and quality of life in children with bronchial asthma. Methods. A comprehensive search was performed using PubMed, Cochrane Library, Web of Science, EBSCO, CNKI, and Wanfang Data Knowledge Service platform to identify any relevant randomized controlled trials (RCTs) published from inception to April 2021. The Cochrane risk of the bias tool was utilized to evaluate the methodological quality of the included studies, and RevMan 5.3 was applied to perform data analyses. Results. A total of 22 RCTs involving 1346 patients were included. The results of the meta-analysis showed that exercise had significant advantages in improving lung function and exercising capacity and quality of life in children with asthma compared with conventional treatment, such as the forced vital capacity to predicted value ratio (SMD = 0.27; 95% CI: 0.13, 0.40, and P < 0.0001 ), the peak expiratory flow to predicted value ratio (MD = 4.53; 95% CI: 1.27, 7.80, and P = 0.007 ), the 6-minute walk test (MD = 110.65; 95% CI: 31.95, 189.34, and P = 0.006 ), rating of perceived effort (MD = −2.28; 95% CI: −3.21, −1.36, and P < 0.0001 ), and peak power (MD = 0.94; 95% CI: 0.37, 1.52, and P = 0.001 ) on exercise capacity and pediatric asthma quality of life questionnaire (MD = 1.28; 95% CI: 0.60, 1.95, and P = 0.0002 ) on quality of life. However, no significant difference was observed in the forced expiratory flow between 25% and 75% of vital capacity P = 0.25 and the forced expiratory volume at 1 second to predicted value ratio P = 0.07 . Conclusions. Current evidence shows that exercise has a certain effect on improving pulmonary function recovery, exercise capacity, and quality of life in children with bronchial asthma. Given the limitation of the number and quality of included studies, further research and verification are needed to guide clinical application.

Voluntary Cough Effectiveness and Airway Clearance in Neurodegenerative Disease

Purpose: Voluntary cough dysfunction is highly prevalent across multiple patient populations. Voluntary cough has been utilized as a screening tool for swallowing safety deficits and as a target for compensatory and exercise-based dysphagia management. However, it remains unclear whether voluntary cough dysfunction is associated with the ability to effectively clear the airway. Method: Individuals with neurodegenerative disorders performed same-day voluntary cough testing and flexible endoscopic evaluations of swallowing (FEES). Participants who were cued to cough after exhibiting penetration to the vocal folds and/or aspiration with thin liquids during FEES met inclusion criteria. One-hundred and twenty-three trials were blinded, and the amount of residue before and after a cued cough on FEES was measured with a visual analog scale. Linear and binomial mixed-effects models examined the relationship between cough airflow during voluntary cough testing and the proportion of residue expelled. Results: Peak expiratory flow rate ( p = .004) and cough expired volume from the entire epoch ( p = .029) were significantly associated with the proportion of aspiration expelled from the subglottis. Peak expiratory flow rate values of 3.00 L/s, 3.50 L/s, and 5.30 L/s provided high predicted probabilities that ≥ 25%, ≥ 50%, and ≥ 80% aspirate was expelled. Accounting for depth of aspiration significantly improved model fit ( p < .001). Conclusions: These findings suggest that voluntary cough airflow is associated with cough effectiveness to clear aspiration from the subglottis, although aspiration amount and depth may play an important role in this relationship. These findings provide further support for the clinical utility of voluntary cough in the management of dysphagia.

Value of Peak Expiratory Flow Rate in Evaluating Cough Ability in Patients Undergoing Lung Surgery

Introduction. Postoperative ineffective cough is easy to occur after thoracic surgery, and it is also a risk factor for postoperative pulmonary complications (PPCs). Objectives. To explore the value of peak expiratory flow rate (PEF) in evaluating cough ability in patients undergoing lung surgery and evaluate the effectiveness of chest wall compression during the expiratory phase by PEF. Methods. From September 2020 to May 2021, the researchers collected the data of patients who underwent lung surgery. Eventually, 153 patients who met the criteria were included, 102 cases were included in the effective cough group and 51 cases were included in the ineffective cough group. The receiver working curve (ROC curve) was used to analyze whether PEF could evaluate cough ability. At the same time, the researchers collected the pulmonary function data of the first 30 patients of the ineffective cough group while compressing the chest wall during the expiratory phase to evaluate the effectiveness of chest wall compression. Results. The area under the curve (AUC) of postoperative PEF to evaluate the postoperative cough ability was 0.955 (95% CI: 0.927–0.983, P < 0.001 ). The values of PEF (127.17 ± 34.72 L/min vs. 100.70 ± 29.98 L/min, P < 0.001 , 95% CI: 18.34–34.59) and FEV1 (0.72 (0.68–0.97) L vs. 0.64 (0.56–0.82) L, P < 0.001 ) measured while compressing the chest wall were higher than those without compression. Conclusions. PEF can be used as a quantitative indicator of cough ability. Chest wall compression could improve cough ability for patients who have ineffective cough.

Obesity Indices for Predicting Functional Fitness in Children and Adolescents With Obesity

Objectives: We aimed to determine the obesity indices that affect 6-min walk test (6-MWT) distance in children and adolescents with obesity and to compare the 6-MWT distance of obese subjects with that of normal-weight subjects.Methods: Obese children and adolescents aged 8–15 years and normal-weight age- and gender-matched controls were enrolled. All participants performed the 6-MWT; respiratory muscle strength (RMS), including maximal inspiratory pressure and maximal expiratory pressure; and spirometry. Data between groups were compared. In the obesity group, correlation between obesity indices and pulmonary function testing (6-MWT, RMS, and spirometry) was analyzed.Results: The study included 37 obese and 31 normal-weight participants. The following parameters were all significantly lower in the obesity group than in the normal-weight group: 6-MWT distance (472.1 ± 66.2 vs. 513.7 ± 72.9 m; p = 0.02), forced expiratory volume in one second/forced vital capacity (FEV1/FVC) (85.3 ± 6.7 vs. 90.8 ± 4.5%; p &lt; 0.001), forced expiratory flow rate within 25–75% of vital capacity (FEF25−75%) (89.8 ± 23.1 vs. 100.4 ± 17.3 %predicted; p = 0.04), and peak expiratory flow (PEF) (81.2 ± 15 vs. 92.5 ± 19.6 %predicted; p = 0.01). The obesity indices that significantly correlated with 6-MWT distance in obese children and adolescents were waist circumference-to-height ratio (WC/Ht) (r = −0.51; p = 0.001), waist circumference (r = −0.39; p = 0.002), body mass index (BMI) (r = −0.36; p = 0.03), and chest circumference (r = −0.35; p = 0.04). WC/Ht was the only independent predictor of 6-MWT distance by multiple linear regression.Conclusions: Children and adolescents with obesity had a significantly shorter 6-MWT distance compared with normal-weight subjects. WC/Ht was the only independent predictor of 6-MWT distance in the obesity group.

Quantifying tidal expiratory flow limitation using a vector-based analysis technique

Objective: Tidal expiratory flow limitation (EFLT) is commonly identified by tidal breaths exceeding the forced vital capacity (FVC) loop. This technique, known as the Hyatt method, is limited by the difficulties in defining the FVC and tidal flow-volume (TV) loops. The vector-based analysis (VBA) technique described and piloted in this manuscript identifies and quantifies EFLT as tidal breaths that conform to the contour of the FVC loop. Approach: The FVC and TV loops are interpolated to generate uniformly spaced plots. VBA is performed to determine the smallest vector difference between each point on the FVC and TV curves, termed the flow reserve vector (FRV). From the FVC point yielding the lowest FRV, the tangential angles of the FVC and TV segments are recorded. If the TV and FVC loops become parallel, the difference between the tangential angles tends towards zero. We infer EFLT as parallel TV and FVC segments where the FRV is <0.1 and the tangential angle is within ±18 degrees for ≥5% of TV. EFLT is quantified by the percent of TV loop fulfilling these criteria. We compared the presence and degree of EFLT at rest and during peak exercise using the Hyatt method and our VBA technique in 25 healthy subjects and 20 subjects with moderate-severe airflow obstruction. Main results: Compared to the Hyatt method, our VBA technique reported a significantly lower degree of EFLT in healthy subjects during peak exercise, and in obstructed subjects at rest and during peak exercise. In contrast to the Hyatt method, our VBA technique re-classified five subjects (one in the healthy group and four in the obstructed group) as demonstrating EFLT. Significance: Our VBA technique provides an alternative approach to determine and quantify EFLT which may reduce the overestimation of the degree EFLT and more accurately identify subjects experiencing EFLT.

Overnight variation in tidal expiratory flow limitation in COPD patients and its correction: an observational study

Background Tidal expiratory flow limitation (EFLT) is common among COPD patients. Whether EFLT changes during sleep and can be abolished during home ventilation is not known. Methods COPD patients considered for noninvasive ventilation used a ventilator which measured within-breath reactance change at 5 Hz (∆Xrs) and adjusted EPAP settings to abolish EFLT. Participants flow limited (∆Xrs > 2.8) when supine underwent polysomnography (PSG) and were offered home ventilation for 2 weeks. The EPAP pressure that abolished EFLT was measured and compared to that during supine wakefulness. Ventilator adherence and subjective patient perceptions were obtained after home use. Results Of 26 patients with supine EFLT, 15 completed overnight PSG and 10 the home study. In single night and 2-week home studies, EFLT within and between participants was highly variable. This was unrelated to sleep stage or body position with only 14.6% of sleep time spent within 1 cmH2O of the awake screening pressure. Over 2 weeks, mean EPAP was almost half the mean maximum EPAP (11.7 vs 6.4 cmH2O respectively). Group mean ∆Xrs was ≤ 2.8 for 77.3% of their home use with a mean time to abolish new EFLT of 5.91 min. Adherence to the ventilator varied between 71 and 100% in prior NIV users and 36–100% for naïve users with most users rating therapy as comfortable. Conclusions Tidal expiratory flow limitation varies significant during sleep in COPD patients. This can be controlled by auto-titrating the amount of EPAP delivered. This approach appears to be practical and well tolerated by patients. Trial registration: The trial was retrospectively registered at CT.gov NCT04725500.