Expiratory Flow Limitation Research Articles

Thoracic load carriage impairs the acute physiological response to hypoxia in healthy males.

To assess the impact of thoracic load carriage on the physiological response to exercise in hypoxia. Healthy males (n = 12) completed 3 trials consisting of 45 min walking in the following conditions: (1) unloaded normoxia (UN; FIO2:20.93%); (2) unloaded hypoxia (UH; FIO2:~13.0%); and (3) loaded hypoxia (LH; 29.5 kg; FIO2:~13.0%). Intensity was matched for absolute VO2 (2.0 ± 0.2 L·min-1) across conditions and relative VO2 (64.0 ± 2.6 %VO2max) across hypoxic conditions. With LH versus UH, there were increases in breathing frequency (5-11 breaths·min-1; p < 0.05) and decreases in tidal volume (10%-18%; p < 0.05) throughout exercise due to reductions in end inspiratory lung volumes (p < 0.05). Consequently, deadspace (11%-23%; p < 0.05) and minute ventilation (7%-11%; p < 0.05) were increased starting at 20 and 30 min, respectively. In addition, LH increased perceived exertion/dyspnea and induced inspiratory (~12%; p < 0.05 vs. UN) and expiratory (~10%; p < 0.05 vs. pre-exercise) respiratory muscle fatigue. Expiratory flow limitation was present in 50% of subjects during LH. Cardiac output and muscle oxygenation were maintained during LH despite reduced stroke volume (6%-8%; p < 0.05). Finally, cerebral oxygenated/total hemoglobin were elevated in the LH condition versus UH starting at 15 min (p < 0.05). Thoracic load carriage increases physiological strain and interferes with the compensatory response to hypoxic exposure.

Establishing Normative Values of Peak Expiratory Flow Rates in the Paediatric Population in Jharkhand.

Background The peak expiratory flow rate (PEFR) is the maximum flow rate (expressed as L/s) generated during a forceful exhalation, starting from full inspiration. It is an effort-dependent parameter and reflects large airway flow. It depends on lung recoil, muscular strength of patients, and voluntary effort. The PEFR is a simple and easy way to detect early changes in lung function. The PEFR can be measured by a peak flow meter or a spirometer; however, a spirometer is more accurate than a peak flow meter. The PEFR is known to vary according to age, gender, and anthropometric parameters like height, weight, BMI, ethnicity, and altitude. PEFR values for different populations are needed because they helpto determine the variable expiratory flow limitation in asthma. There is no study done to find out the normal PEFR in children in Jharkhand. Hence, this studyaimed to establish the reference values of the PEFR of children in Jharkhand. Methodology Three hundred and sixteen healthy children belonging to the age group of 6-18 years attending the OPD of Rajendra Institute of Medical Sciences, Ranchi were studied. All the children were asked to perform spirometry, and the PEFR was recorded. Patient demographic details like age, sex, height, weight, BMI, and ethnicity were documented. These factors were selectedto see how the PEFR of children in Jharkhand correlated with them and compare it with the values obtained from similar studies conducted in different parts of India. Results Three hundred and sixteen children were studied, consisting of 194 male participants and 122 female participants. The mean PEFR for maleparticipantswas 3.90±1.58L/s and for female participants, it was 4.04±1.49L/s. The correlation coefficient of the PEFR with height was 0.792, that of the PEFR with weight was 0.713 and that of the PEFR with BMI was 0.364. Hence, height is the best predictor of PEFR. The lowest correlation of BMI with PEFR shows that the recent rise in obesity in the paediatric population should not be expected to affect the lung function significantly. Conclusion The mean PEFR of children in Jharkhand is lower than that of children in northern (mean PEFR of maleparticipants=4.41 ± 1.54 L/s, mean PEFR of female participants = 4.17 ± 1.17 L/s) and southern India (mean PEFR of maleparticipants=4.88±1.29 L/s, mean PEFR of female participants = 4.25±1.29 L/s). Compared to neighbouring states in eastern India, the mean PEFR of children in Jharkhand is lower.

Expiratory flow limitation development index (ELDI): a novel method of assessing respiratory mechanics in COPD

BackgroundExpiratory flow limitation (EFL) can be detected using oscillometric reactance and is associated with a worse clinical presentation in chronic obstructive pulmonary disease (COPD). Reactance can show negative swings upon exhalation, which may develop at different rates between patients. We propose a new method to quantify the rate of EFL development; the EFL Development Index (ELDI).MethodsA retrospective analysis of data from 124 COPD patients was performed. Data included lung function tests, Impulse Oscillometry (IOS), St Georges Respiratory Questionnaire (SGRQ), modified Medical Research Council (mMRC) scale and COPD Assessment Test (CAT) score. Fifty four patients had repeat data after 6 months. Twenty two patients had data recorded after 5 days of treatment with long acting bronchodilator therapy. EDLI was calculated as the mean expiratory reactance divided by the minimum expiratory reactance.ResultsThe mean ELDI was used to categorise patients with rapid onset of EFL (> 0.63; n = 29) or gradual onset (≤ 0.63; n = 34). Those with rapid development had worse airflow obstruction, lower quality of life scores, and greater resting hyperinflation, compared to those with gradual development. In patients with EFL, ELDI correlated with symptoms scores, airflow obstruction, lung volumes and gas diffusion. Both EFL and ELDI were stable over 6 months. EFL and EDLI improved with bronchodilator treatment.ConclusionsCOPD patients with rapid EFL development (determined by ELDI) had worse clinical characteristics than those with gradual EFL development. The rate of EFL development appears to be associated with clinical and physiological characteristics.

Assessing the repeatability of expiratory flow limitation during incremental exercise in healthy adults.

We sought to determine the repeatability of EFL in healthy adults during incremental cycle exercise. We hypothesized that the repeatability of EFL would be "strong" when assessed as a binary variable (i.e., absent or present) but "poor" when assessed as a continuous variable (i.e., % tidal volume overlap). Thirty-two healthy adults performed spirometry and an incremental cycle exercise test to exhaustion on two occasions. Standard cardiorespiratory variables were measured at rest and throughout exercise, and EFL was assessed by overlaying tidal expiratory flow-volume and maximal expiratory flow-volume curves. The repeatability of EFL was determined using Cohen's κ for binary assessments of EFL and intraclass correlation (ICC) for continuous measures of EFL. During exercise, n = 12 participants (38%) experienced EFL. At peak exercise, the repeatability of EFL was "minimal" (κ = 0.337, p = 0.145) when assessed as a binary variable and "poor" when measured as a continuous variable (ICC = 0.338, p = 0.025). At matched levels of minute ventilation during high-intensity exercise (i.e., >75% of peak oxygen uptake), the repeatability of EFL was "weak" when measured as a binary variable (κ = 0.474, p = 0.001) and "moderate" when measured as a continuous variable (ICC = 0.603, p < 0.001). Our results highlight the day-to-day variability associated with assessing EFL during exercise in healthy adults.

Difference in expiratory flow limitations development in normoxia and hypoxia in healthy individuals

The present study investigated the maintenance/repeatability of expiratory flow limitation (EFL) between normoxia and hypoxia.Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental cycling test in both normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits.During exercise in normoxia, 28 participants exhibited EFL (55 %). In hypoxia, another cohort of 28 participants exhibited EFL. The two groups only partly overlapped.Individuals with EFL only in normoxia reported lower maximal ventilation values in hypoxia than in normoxia (n=5; −13.5 ± 7.8 %) compared to their counterparts with EFL only in hypoxia (n=5; +6.7 ± 6.3 %) or without EFL (n=18; +5.1 ± 10.3 %) (p=0.004 and p<0.001, respectively).EFL development may be induced by different mechanisms in hypoxia vs. normoxia since the individuals who exhibited flow limitation were not the same between the two environmental conditions. This change seems influenced by the magnitude of the maximal ventilation change.

Immunobiologicals in severe asthma: case report

According to the Global Initiative for Asthma (GINA), asthma is a chronic-inflammatory respiratory disease, characterized by limitation of expiratory air flow, dyspnea, wheezing and tachypnea, especially at night or in contact with allergens, climate changes or presence of environmental pollution. Among its subtypes, severe asthma stands out, where the symptomatic condition persists despite optimized treatment at advanced levels. The present study is a case report associated with a literature review on the use of immunobiologicals in the clinical treatment of severe asthma. Female patient, 53 years old, history of late-onset asthma at age 25, with frequent exacerbations, using drug therapy based on inhaled corticosteroid (ICS), long-acting β2-agonist (LABA) and a long-acting muscarinic antagonist (LAMA) in a single inhaler associated with the use of oral corticosteroids. After confirming the diagnosis of severe non-allergic eosinophilic asthma of endotype T2, GINA 5, the patient started treatment with mepolizumab and months later she showed significant improvement with the use of the immunobiological 1x/month and use of ICS associated with LABA. 12/12h, without the need for oral corticosteroids and use of rescue medications less than 2x/week.

The effect of expiratory flow limitation on supine persistent hyperinflation in COPD: a prospective observational study.

COPD is characterised by airflow obstruction, expiratory airway collapse and closure causing expiratory flow limitation (EFL) and hyperinflation. Supine posture may worsen ventilatory function in COPD, which may cause hyperinflation to persist and contribute to symptoms of orthopnoea and sleep disturbance. Our aim was to determine the impact of supine posture on hyperinflation, dynamic elastance and EFL in COPD and healthy subjects. We hypothesised that changes in hyperinflation in supine posture are influenced by EFL and gas trapping in COPD. Clinically stable COPD patients (compatible symptoms, smoking >10 pack-years, obstructed spirometry) and healthy controls underwent oscillometry in the seated and supine positions. Hyperinflation was measured by inspiratory capacity (IC) and the ratio of IC to total lung capacity (IC/TLC) while seated and supine EFL was measured as the difference in mean inspiratory and mean expiratory oscillatory reactance at 5 Hz (X rs5). Relationships between IC, IC/TLC and X rs5, were examined by Spearman correlation. 42 COPD patients demonstrated no change in IC/TLC from seated (0.31 L) to supine (0.32 L) position (p=0.079) compared to significant increases seen in 14 control subjects (0.37 L seated versus 0.44 L supine; p<0.001). In COPD, worse dynamic elastance (X rs5 rs 0.499; p=0.001) and EFL (ΔX rs5 rs -0.413; p=0.007), along with increased age and lower body-mass-index were predictors of supine hyperinflation. Supine persistent hyperinflation occurs in COPD and is associated with increased dynamic elastance and EFL, likely the result of increased airway closure due to gravitational redistribution of lung mass.

Expiratory flow limitation during mechanical ventilation: real-time detection and physiological subtypes

BackgroundTidal expiratory flow limitation (EFLT) complicates the delivery of mechanical ventilation but is only diagnosed by performing specific manoeuvres. Instantaneous analysis of expiratory resistance (Rex) can be an alternative way to detect EFLT without changing ventilatory settings. This study aimed to determine the agreement of EFLT detection by Rex analysis and the PEEP reduction manoeuvre using contingency table and agreement coefficient. The patterns of Rex were explored.MethodsMedical patients ≥ 15-year-old receiving mechanical ventilation underwent a PEEP reduction manoeuvre from 5 cmH2O to zero for EFLT detection. Waveforms were recorded and analyzed off-line. The instantaneous Rex was calculated and was plotted against the volume axis, overlapped by the flow-volume loop for inspection. Lung mechanics, characteristics of the patients, and clinical outcomes were collected. The result of the Rex method was validated using a separate independent dataset.Results339 patients initially enrolled and underwent a PEEP reduction. The prevalence of EFLT was 16.5%. EFLT patients had higher adjusted hospital mortality than non-EFLT cases. The Rex method showed 20% prevalence of EFLT and the result was 90.3% in agreement with PEEP reduction manoeuvre. In the validation dataset, the Rex method had resulted in 91.4% agreement. Three patterns of Rex were identified: no EFLT, early EFLT, associated with airway disease, and late EFLT, associated with non-airway diseases, including obesity. In early EFLT, external PEEP was less likely to eliminate EFLT.ConclusionsThe Rex method shows an excellent agreement with the PEEP reduction manoeuvre and allows real-time detection of EFLT. Two subtypes of EFLT are identified by Rex analysis.Trial registration: Clinical trial registered with www.thaiclinicaltrials.org (TCTR20190318003). The registration date was on 18 March 2019, and the first subject enrollment was performed on 26 March 2019.

Effects of Obesity and Sex on Ventilatory Constraints during a Cardiopulmonary Exercise Test in Children.

Ventilatory constraints are common during exercise in children, but the effects of obesity and sex are unclear. The purpose of this study was to investigate the effects of obesity and sex on ventilatory constraints (i.e., expiratory flow limitation (EFL) and dynamic hyperinflation) during a maximal exercise test in children. Thirty-four 8- to 12-yr-old children without obesity (18 females) and 54 with obesity (23 females) completed pulmonary function testing and maximal cardiopulmonary exercise tests. EFL was calculated as the overlap between tidal flow-volume loops during exercise and maximal expiratory flow-volume loops. Dynamic hyperinflation was calculated as the change in inspiratory capacity from rest to exercise. Maximal minute ventilation was not different between children with and without obesity. Average end-inspiratory lung volumes (EILV) and end-expiratory lung volumes (EELV) were significantly lower during exercise in children with obesity (EILV: 68.8% ± 0.7% TLC; EELV: 41.2% ± 0.5% TLC) compared with children without obesity (EILV: 73.7% ± 0.8% TLC; EELV: 44.8% ± 0.6% TLC; P < 0.001). Throughout exercise, children with obesity experienced more EFL and dynamic hyperinflation compared with those without obesity ( P < 0.001). Also, males experienced more EFL and dynamic hyperinflation throughout exercise compared with females ( P < 0.001). At maximal exercise, the prevalence of EFL was similar in males with and without obesity; however, the prevalence of EFL in females was significantly different, with 57% of females with obesity experiencing EFL compared with 17% of females without obesity ( P < 0.05). At maximal exercise, 44% of children with obesity experienced dynamic hyperinflation compared with 12% of children without obesity ( P = 0.002). Obesity in children increases the risk of developing mechanical ventilatory constraints such as dynamic hyperinflation and EFL. Sex differences were apparent with males experiencing more ventilatory constraints compared with females.

A switching lung mechanics model for detection of expiratory flow limitation

Abstract Expiratory flow limitation (EFL) is an often unrecognized clinical condition with a multitude of negative implications. A mathematical EFL model is proposed to detect flow limitations automatically. The EFL model is a switching one-compartment lung mechanics model with a volume-dependent airway resistance to simulate the dynamic behavior during expiration. The EFL detection is based on a breath-by-breath model parameter identification and validated on clinical data of mechanically ventilated patients. In the severe flow limitation group 93.9 % ± 5 % and in the no limitation group 10.2 % ± 13.7 % of the breaths are detected as EFL. Based on the high detection rate of EFL, these results support the usefulness of the EFL detection. It is a first step toward an automated detection of EFL in clinical applications and may help to reduce underdiagnosis of EFL.

Averaging Tidal Flow-volume Loops: A tale of two methods

Introduction: A standard practice in cardiopulmonary exercise testing (CPET) is calculating the average flow and volume data across multiple breaths. Currently, many laboratories find average flow-volume loops by taking equal increments of the tidal volume and averaging the respective increments of flow for each breath. However, it has been proposed that using equal increments of total time to find an average flow-volume loop could more accurately capture the shape of the loop, which could be critical to determining expiratory flow limitation (EFL) when placed within a maximal flow-volume loop. Purpose: To compare the use of time vs. volume bins on producing averaged flow-volume loops and evaluate whether the results could affect the interpretation of EFL. Methods: Time, volume, and flow data of consecutive breaths at rest and during exercise were obtained for four individuals: one younger healthy man, one older healthy woman, one older man with heart failure, and one child with obesity. The data were separated into individual breaths using zero flow points, then total time and tidal volume were calculated for each full breath. For the time bin method as proposed by M. Younes, equal intervals of time were calculated for both the inspiratory and expiratory phases of each breath. Linear interpolation between surrounding data points was performed to obtain volume and flow values at these intervals. Volume data were then normalized to the tidal volume of the breath by taking the value as a percentage of the total tidal volume. From here, the volume and flow data at the corresponding intervals for each breath were averaged to create the final average flow-volume loop. For the volume bin method, equal intervals of volume were determined based on the tidal volume. Linear interpolation was then used to calculate the respective flow values at these intervals. The volume and flow data at the corresponding intervals for each breath were then averaged to generate the average flow-volume loop data. Standard deviation at each averaged point was also calculated for both methods. Results: Minimal difference was visible between the time bin and volume bin methods at 20 intervals. As the number of intervals used increased, the difference became less apparent. At 250 intervals, the volume bin method depicted the average flow-volume loop as effectively as the time bin method. Addition of standard deviations gave a better view of the variability of flow at any volume. Conclusion: Despite the inherent incrementation associated with the use of time bins vs. volume bins the average flow-volume loops looked very similar. However, the addition of the standard deviations of flow and volume at each data point could yield different results for determining EFL. Also, the time bin method may yield more resolution at rapid transition points at the beginning of inspiration and expiration. Overall, the observed similarities between time bin and volume bin methods are likely due to increased computer capabilities and the ability to create more intervals (i.e., 20 vs. 250), making a constant unit of measurement less necessary. Funding: NIH R01 HL136643, NIH R01 AG070262, NIH P01 HL137630, King Charitable Foundation Trust, Susan Lay Atwell Annuity Trust for Pulmonary Research, Cain Foundation, and Texas Health Presbyterian Hospital Dallas. Dr. Daniel Wilhite was funded by an NIH Administrative Supplement to Promote Diversity in Health-Related Research (HL136643-01S1). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Tidal expiratory flow limitation during exercise is unrelated to peripheral hypercapnic chemosensitivity

We sought to determine if peripheral hypercapnic chemosensitivity is related to expiratory flow limitation (EFL) during exercise. Twenty participants completed one testing day which consisted of peripheral hypercapnic chemosensitivity testing and a maximal exercise test to exhaustion. The chemosensitivity testing consisting of two breaths of 10% CO2 (O2∼21%) repeated 5 times during seated rest and the first 2 exercise intensities during the maximal exercise test. Following chemosensitivity testing, participants continued cycling with the intensity increasing 20 W every 1.5 minutes till exhaustion. Maximal expiratory flow-volume curves were derived from forced expiratory capacity maneuvers performed before and after exercise at varying efforts. Inspiratory capacity maneuvers were performed during each exercise stage to determine EFL. There was no difference between the EFL and non-EFL hypercapnic chemoresponse (mean response during exercise 0.96 ± 0.46 and 0.91 ± 0.33 l min−1 mmHg−1, p=0.783). Peripheral hypercapnic chemosensitivity during mild exercise does not appear to be related to the development of EFL during exercise.

Fitness Level- and Sex-Related Differences in Pulmonary Limitations to Maximal Exercise in Normoxia and Hypoxia.

Both maximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach its maximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations during maximal-intensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia. Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit. EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different ( P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio ( P = 0.029), higher ventilation (V̇ E ) ( P < 0.001), larger ΔVO 2max ( P = 0.019), and lower hypoxia-related V̇ E increase ( P < 0.001). Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions.

Persistence of expiratory flow limitations between normoxia and hypoxia

Introduction&#x0D; Expiratory flow limitation (EFL) refers to the inability to generate higher airflow despite greater respiratory effort and is common in both men and women. In normoxic condition, EFL is contingent upon an imbalance between ventilatory demands and capacity. Since hypoxia is known to alter ventilatory drive and pattern, it may influence the development of EFL. Therefore, the aim of this study was to investigate the origin of EFL in hypoxia and its repeatability and persistence during exercise in hypoxia.&#x0D; Method&#x0D; Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental exercise test on a cycle-ergometer in normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits. Ventilatory capacity, assessed using the slope ratio (SR), were evaluated from maximal flow volume curve analyses.&#x0D; Results&#x0D; During exercise in normoxia, 28 participants exhibited EFL (55%). Another set of 28 participants exhibited EFL in hypoxia but they were not all the same individuals as those in normoxia. In normoxia, both SR and maximum minute ventilation (V̇E) were higher in the EFL group than the non-EFL group (p = 0.029 and p &lt;0.001; respectively). However, in hypoxia, only maximum V̇E was higher in the EFL group compared to non-EFL group (p = 0.006).&#x0D; Participants were then classified into 4 groups according to the occurrence of EFL in both normoxia and hypoxia: non-EFL in both conditions (non-EFLN/H, n = 18), EFL in both conditions (EFLN/H, n = 23), EFL developed only in normoxia (EFLN+/H-, n = 5), EFL developed only in hypoxia (EFLN-/H+, n = 5).&#x0D; The EFLN+/H- group showed different V̇E changes between normoxia and hypoxia (-13.5 ± 7.8%) compared to the EFLN-/H+ (+6.7 ± 6.3%) and the non-EFLN/H groups (+5.1 ± 10.3%; p = 0.004 and p &lt; 0.001, respectively). The difference with the EFLN/H (-1.7 ± 8.0%) did not reach significance (p = 0.057). Breathing frequency changes between normoxia and hypoxia were different between the EFLN-/H+ group (+4.6 ± 12.9%) and the EFLN+/H- group (-11.7 ± 13.1%) (p = 0.039). Normoxia to hypoxia decrease in maximal oxygen uptake was not significantly larger in the EFL N+/H- group (-18.4 ± 3.4%) than in the EFL EFLN-/H+ group (-10.3 ± 5.4%; p = 0.087).&#x0D; Discussion/Conclusion&#x0D; Hypoxia altered EFL development since there was a shift in the individuals who exhibited flow limitation between normoxia and hypoxia. This can be attributed to the extent of ventilatory reserve utilization. Specifically, those who developed EFL exclusively in hypoxia exhibited a significant increase in V̇E whereas those with EFL only in normoxia experienced a significant decrease in V̇E. Notably in hypoxia, the ventilatory capacity did not differ between individuals with EFL and those without. This observation suggests that in hypoxia, the development of EFL relied more on ventilatory demands than on ventilatory capacity.

Effect of twice daily inhaled albuterol on cardiopulmonary exercise outcomes, dynamic hyperinflation, and symptoms in secondhand tobacco-exposed persons with preserved spirometry and air trapping: a randomized controlled trial

BackgroundIn tobacco-exposed persons with preserved spirometry (active smoking or secondhand smoke [SHS] exposure), air trapping can identify a subset with worse symptoms and exercise capacity. The physiologic nature of air trapping in the absence of spirometric airflow obstruction remains unclear. The aim of this study was to examine the underlying pathophysiology of air trapping in the context of preserved spirometry and to determine the utility of bronchodilators in SHS tobacco-exposed persons with preserved spirometry and air trapping.MethodsWe performed a double-blinded placebo-controlled crossover randomized clinical trial in nonsmoking individuals at risk for COPD due to exposure to occupational SHS who had preserved spirometry and air trapping defined as either a residual volume-to-total lung capacity ratio (RV/TLC) > 0.35 or presence of expiratory flow limitation (EFL, overlap of tidal breathing on maximum expiratory flow-volume loop) on spirometry at rest or during cardiopulmonary exercise testing (CPET). Those with asthma or obesity were excluded. Participants underwent CPET at baseline and after 4-week trials of twice daily inhalation of 180 mcg of albuterol or placebo separated by a 2-week washout period. The primary outcome was peak oxygen consumption (VO2) on CPET. Data was analyzed by both intention-to-treat and per-protocol based on adherence to treatment prescribed.ResultsOverall, 42 participants completed the entire study (66 ± 8 years old, 91% female; forced expiratory volume in 1 s [FEV1] = 103 ± 16% predicted; FEV1 to forced vital capacity [FVC] ratio = 0.75 ± 0.05; RV/TLC = 0.39 ± 0.07; 85.7% with EFL). Adherence was high with 87% and 93% of prescribed doses taken in the treatment and placebo arms of the study, respectively (P = 0.349 for comparison between the two arms). There was no significant improvement in the primary or secondary outcomes by intention-to-treat or per-protocol analysis. In per-protocol subgroup analysis of those with RV/TLC > 0.35 and ≥ 90% adherence (n = 27), albuterol caused an improvement in peak VO2 (parameter estimate [95% confidence interval] = 0.108 [0.014, 0.202]; P = 0.037), tidal volume, minute ventilation, dynamic hyperinflation, and oxygen-pulse (all P < 0.05), but no change in symptoms or physical activity.ConclusionsAlbuterol may improve exercise capacity in the subgroup of SHS tobacco-exposed persons with preserved spirometry and substantial air trapping. These findings suggest that air trapping in pre-COPD may be related to small airway disease that is not considered significant by spirometric indices of airflow obstruction.

Oscillometry-Defined Small Airway Dysfunction in Patients with Chronic Obstructive Pulmonary Disease.

The prevalence of small airway dysfunction (SAD) in patients with chronic obstructive pulmonary disease (COPD) across different ethnicities is poorly understood. This study aimed to estimate the prevalence of SAD in stable COPD patients. We conducted a cross-sectional study of 196 consecutive stable COPD patients. We measured pre- and post-bronchodilator (BD) lung function and respiratory impedance. The severity of COPD and lung function abnormalities was graded in accordance with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. SAD was defined as either difference in whole-breath resistance at 5 and 19 Hz &gt; upper limit of normal or respiratory system reactance at 5 Hz &lt; lower limit of normal. The cohort consisted of 95.9% men, with an average age of 66.3 years. The mean forced expiratory volume 1 second (FEV1) % predicted was 56.4%. The median COPD assessment test (CAT) scores were 14. The prevalence of post-BD SAD across the GOLD grades 1 to 4 was 14.3%, 51.1%, 91%, and 100%, respectively. The post-BD SAD and expiratory flow limitation at tidal breath (EFLT) were present in 62.8% (95% confidence interval [CI], 56.1 to 69.9) and 28.1% (95% CI, 21.9 to 34.2), respectively. COPD patients with SAD had higher CAT scores (15.5 vs. 12.8, p&lt;0.01); poor lung function (FEV1% predicted 46.6% vs. 72.8%, p&lt;0.01); lower diffusion capacity for CO (4.8 mmol/min/kPa vs. 5.6 mmol/min/kPa, p&lt;0.01); hyperinflation (ratio of residual volume to total lung capacity % predicted: 159.7% vs. 129%, p&lt;0.01), and shorter 6-minute walk distance (367.5 m vs. 390 m, p=0.02). SAD is present across all severities of COPD. The prevalence of SAD increases with disease severity. SAD is associated with poor lung function and higher symptom burden. Severe SAD is indicated by the presence of EFLT.

Bronchial obstruction in osteogenesis imperfecta can be detected by forced oscillation technique.

Respiratory insufficiency is a leading cause of death in individuals with osteogenesis imperfecta (OI). However, evaluating pulmonary function in OI presents challenges. Commonly used pulmonary function tests such as spirometry and body plethysmography are sometimes difficult to perform for OI patients, and reference intervals are not always applicable. The forced oscillation technique (FOT) is a patient-friendly method for detecting respiratory abnormalities that requires no effort from the patient. This study investigates the feasibility of FOT in the evaluation of respiratory function in the clinical management of OI patients. Twelve OI patients, comprising eight with Sillence OI I, two with OI IV, and two with OI III, underwent spirometry, body plethysmography, and FOT, both pre-and post-administration of salbutamol. FOT measurements exhibited consistent trends that aligned with spirometry and body plethysmography findings. The resistance at 8 Hz decreased after the administration of salbutamol, indicating that FOT is able to detect bronchial obstruction and its alleviation by medication (p < 0.05). The resonant frequency during expiration was higher than during inspiration in nearly all patients, suggesting obstructive disease. The technique gives insight into both inspiratory and expiratory impairment of pulmonary ventilation. The main FOT parameters showed a relatively high repeatability in duplicate measurements. Bronchial obstruction can be detected by FOT in patients with OI during quiet breathing, making it an easily executable alternative to other lung function measurements. The technique can detect the bronchodilator effect of sympathomimetic medication. It has the potential to provide information on expiratory flow limitation, pulmonary restriction, and reduced lung compliance.

Using intra-breath oscillometry in obesity hypoventilation syndrome to detect tidal expiratory flow limitation: a potential marker to optimize CPAP therapy

BackgroundContinuous positive airway pressure (CPAP) therapy has profound effects in obesity hypoventilation syndrome (OHS). Current therapy initiation focuses on upper airway patency rather than the assessment of altered respiratory mechanics due to increased extrapulmonary mechanical load.MethodsWe aimed to examine the viability of intra-breath oscillometry in optimizing CPAP therapy for OHS. We performed intra-breath oscillometry at 10 Hz in the sitting and supine positions, followed by measurements at increasing CPAP levels (none-5-10-15-20 cmH2O) in awake OHS patients. We plotted intra-breath resistance and reactance (Xrs) values against flow (V’) and volume (V) to identify tidal expiratory flow limitation (tEFL).ResultsThirty-five patients (65.7% male) completed the study. We found a characteristic looping of the Xrs vs V’ plot in all patients in the supine position revealing tEFL: Xrs fell with decreasing flow at end-expiration. Intra-breath variables representing expiratory decrease of Xrs became more negative in the supine position [end-expiratory Xrs (mean ± SD): -1.9 ± 1.8 cmH2O·s·L− 1 sitting vs. -4.2 ± 2.2 cmH2O·s·L− 1 supine; difference between end-expiratory and end-inspiratory Xrs: -1.3 ± 1.7 cmH2O·s·L− 1 sitting vs. -3.6 ± 2.0 cmH2O·s·L− 1 supine, p < 0.001]. Increasing CPAP altered expiratory Xrs values and loop areas, suggesting diminished tEFL (p < 0.001). ‘Optimal CPAP’ value (able to cease tEFL) was 14.8 ± 4.1 cmH2O in our cohort, close to the long-term support average of 13.01(± 2.97) cmH2O but not correlated. We found no correlation between forced spirometry values, patient characteristics, apnea-hypopnea index and intra-breath oscillometry variables.ConclusionstEFL, worsened by the supine position, can be diminished by stepwise CPAP application in most patients. Intra-breath oscillometry is a viable method to detect tEFL during CPAP initiation in OHS patients and tEFL is a possible target for optimizing therapy in OHS patients.

Breathing a low-density gas reduces respiratory muscle force development and marginally improves exercise performance in master athletes.

We tested the hypothesis that breathing heliox, to attenuate the mechanical constraints accompanying the decline in pulmonary function with aging, improves exercise performance. Fourteen endurance-trained older men (67.9 ± 5.9 year, [Formula: see text]O2max: 50.8 ± 5.8ml/kg/min; 151% predicted) completed two cycling 5-km time trials while breathing room air (i.e., 21% O2-79% N2) or heliox (i.e., 21% O2-79% He). Maximal flow-volume curves (MFVC) were determined pre-exercise to characterize expiratory flow limitation (EFL, % tidal volume intersecting the MFVC). Respiratory muscle force development was indirectly determined as the product of the time integral of inspiratory and expiratory mouth pressure (∫Pmouth) and breathing frequency. Maximal inspiratory and expiratory pressure maneuvers were performed pre-exercise and post-exercise to estimate respiratory muscle fatigue. Exercise performance time improved (527.6 ± 38 vs. 531.3 ± 36.9s; P = 0.017), and respiratory muscle force development decreased during inspiration (-22.8 ± 11.6%, P < 0.001) and expiration (-10.8 ± 11.4%, P = 0.003) with heliox compared with room air. EFL tended to be lower with heliox (22 ± 23 vs. 30 ± 23% tidal volume; P = 0.054). Minute ventilation normalized to CO2 production ([Formula: see text]E/[Formula: see text]CO2) increased with heliox (28.6 ± 2.7 vs. 25.1 ± 1.8; P < 0.001). A reduction in MIP and MEP was observed post-exercise vs. pre-exercise but was not different between conditions. Breathing heliox has a limited effect on performance during a 5-km time trial in master athletes despite a reduction in respiratory muscle force development.

Diagnostic Potential of Oscillometry: A Population-based Approach.

Rationale: Respiratory resistance (Rrs) and reactance (Xrs) as measured by oscillometry and their intrabreath changes have emerged as sensitive parameters for detecting early pathological impairments during tidal breathing. Objectives: This study evaluates the prevalence and association of abnormal oscillometry parameters with respiratory symptoms and respiratory diseases in a general adult population. Methods: A total of 7,560 subjects in the Austrian LEAD (Lung, hEart, sociAl, boDy) Study with oscillometry measurements (computed with the Resmon Pro FULL; Restech Srl) were included in this study. The presence of respiratory symptoms and doctor-diagnosed respiratory diseases was assessed using an interview-based questionnaire. Rrs and Xrs at 5 Hz, their inspiratory and expiratory components, the area above the Xrs curve, and the presence of tidal expiratory flow limitation were analyzed. Normality ranges for oscillometry parameters were defined. Measurements and Main Results: The overall prevalence of abnormal oscillometry parameters was 20%. The incidence of abnormal oscillometry increased in the presence of symptoms or diagnoses: 17% (16-18%) versus 27% (25-29%), P < 0.0001. All abnormal oscillometry parameters except Rrs at 5 Hz were significantly associated with respiratory symptoms/diseases. Significant associations were found, even in subjects with normal spirometry, with abnormal oscillometry incidence rates increasing by 6% (4-8%; P < 0.0001) in subjects with symptoms or diagnoses. Conclusions: Abnormal oscillometry parameters are present in one-fifth of this adult population and are significantly associated with respiratory symptoms and disease. Our findings underscore the potential of oscillometry as a tool for detecting and evaluating respiratory impairments, even in individuals with normal spirometry.