Small Airway Resistance Research Articles

Impulse oscillometry in patients with persistent post-COVID-19 symptoms: A retrospective study.

Impaired lung function has been observed in patients following COVID-19 infection, with studies reporting persistent lung volume and diffusing capacity impairments. Some studies have demonstrated significantly higher small airway resistance in COVID-19 positive cases. This retrospective study aims to examine impulse oscillometry (IOS) data of patients with persistent symptoms after COVID-19 infection, focusing on the relationship between time and symptoms. The study analyzed data from adult patients with persistent symptoms who underwent IOS testing within and after 84 days from the diagnosis date. The results showed that patients within 84 days and those between 31 and 84 days had higher small airway resistance values, indicating peripheral airway disease. Patients with dyspnea exhibited higher IOS values compared to those with cough symptoms, suggesting more significant impairment in the peripheral airways. The study highlights the importance of using comprehensive diagnostic tools like IOS to assess respiratory impairments in post-COVID-19 patients, particularly in the small airways. Understanding the relationship between time and symptoms can provide valuable insights for the treatment of peripheral airway dysfunction in post-COVID-19 patients.

Small airway resistance in obese and nonobese patients with obstructive sleep apnea syndrome using impulse oscillometry.

There is limited information on the pathologic changes in the small airways among obese and nonobese patients with obstructive sleep apnea syndrome (OSAS). Impulse oscillometry (IOS) measures airway resistance and reactance independently of patient effort. This study aimed to compare airway resistance in small airways using IOS between obese and nonobese patients with OSAS. In this real-life cross-sectional study, demographic information was collected from obese and nonobese subjects diagnosed with moderate and severe OSAS without any other underlying diseases. Spirometry and IOS measurements were conducted, and the values of both groups were statistically analyzed. The nonobese group had a mean age of 45.6 ± 11.7 years (median 45), while the obese group had a mean age of 48.4 ± 9.5 years (median 47.5). The mean body mass index (BMI) for the nonobese group was 26.2 ± 2.1 kg/m2 (median 27 kg/m2), and for the obese group, it was 35.6 ± 6.4 kg/m2 (median 33 kg/m2). Statistically significant differences were observed between the two groups in R5 - R20 percentage, reactance area (AX), and resonant frequency (Fres) values (p < 0.05). Among obese OSAS patients, there is an increase in resistance in small airways as indicated by IOS values. IOS shows promise as a potential screening tool for diagnosing OSAS.

Respiratory function after 30+ years following sulfur mustard exposure in survivors in Sweden.

Sulfur mustard (SM) exposure causes acute and chronic respiratory diseases. The extent of small airway dysfunction (SAD) in individuals exposed to SM is unclear. This study evaluated and compared SAD in SM-exposed and SM-unexposed participants using noninvasive lung function tests assessing small airway function. This retrospective cohort study involved SM-exposed (n = 15, mean age: 53 ± 8 years) and SM-unexposed (n = 15, mean age: 53 ± 7 years) Kurdish-Swedish individuals in Sweden. Small airway resistance and reactance were assessed using impulse oscillometry (IOS). Nitrogen (N2) multiple breath washout (MBW) was employed to assess lung ventilation heterogeneity. The gas-exchanging capacity of the lungs was assessed using the diffusing capacity of the lungs for the carbon monoxide (DLCO) test. Lung function outcomes were reported as absolute values and z-scores. Group comparisons were performed using the Mann-Whitney U test. No statistically significant differences in age, height, or body mass index were observed between the two groups. IOS showed significantly increased small airway resistance, while N2MBW exhibited significantly increased global and acinar ventilation heterogeneity in SM-exposed individuals compared to that in unexposed individuals. SAD was identified in 14 of 15 SM-exposed individuals, defined as at least one abnormal IOS difference between resistance at 5 and 20 Hz (R5-R20) and/or area of reactance (AX) or N2MBW lung's acinar zone (Sacin), and DLCO adjusted to the alveolar volume (DLCO/VA) outcome. Of these 14 individuals, only 5 demonstrated concordant findings across the IOS and N2MBW tests. Exposure to SM was positively associated with long-term impairment of respiratory tract function in the small airways in the majority of the previously SM-exposed individuals in the present study. Furthermore, both IOS and N2MBW should be employed to detect SAD in SM-exposed survivors as they provide complementary information. Identifying and characterizing the remaining pathology of the small airways in survivors of SM exposure is a first step toward improved treatment and follow-up.

Aerodynamic Simulation of Small Airway Resistance: A New Imaging Biomarker for Chronic Obstructive Pulmonary Disease.

To develop a novel method for calculating small airway resistance using computational fluid dynamics (CFD) based on CT data and evaluate its value to identify COPD. 24 subjects who underwent chest CT scans and pulmonary function tests between August 2020 and December 2020 were enrolled retrospectively. Subjects were divided into three groups: normal (10), high-risk (6), and COPD (8). The airway from the trachea down to the sixth generation of bronchioles was reconstructed by a 3D slicer. The small airway resistance (RSA) and RSA as a percentage of total airway resistance (RSA%) were calculated by CFD combined with airway resistance and FEV1 measured by pulmonary function test. A correlation analysis was conducted between RSA and pulmonary function parameters, including FEV1/FVC, FEV1% predicted, MEF50% predicted, MEF75% predicted and MMEF75/25% predicted. The RSA and RSA% were significantly different among the three groups (p<0.05) and related to FEV1/FVC (r = -0.70, p < 0.001; r = -0.67, p < 0.001), FEV1% predicted (r = -0.60, p = 0.002; r = -0.57, p = 0.004), MEF50% predicted (r = -0.64, p = 0.001; r = -0.64, p = 0.001), MEF75% predicted (r = -0.71, p < 0.001; r = -0.60, p = 0.002) and MMEF 75/25% predicted (r = -0.64, p = 0.001; r = -0.64, p = 0.001). Airway CFD is a valuable method for estimating the small airway resistance, where the derived RSA will aid in the early diagnosis of COPD.

Total airway mechanics and fractional exhaled nitric oxide levels of children living in banjihas (semi-basements).

The ISAAC phase III study in Korea found a higher incidence of wheezing illnesses among residents in basements or semi-basements. This study investigates the link between living in banjihas (semi-basements) and airway resistance and Th2 airway inflammation in Korean children, compared to those on higher floors. We assessed 575 fifth- and sixth-grade students (aged 10-12) in an inner-city area of South Korea. The study utilized impulse oscillometry to measure small and total airway resistance (Rrs20-5 and Rrs0, respectively) and Fractional Exhaled Nitric Oxide (FeNO) measurements to evaluate airway inflammation. We also considered a range of biological and environmental factors, including allergen sensitization, serum 25-hydroxyvitamin D levels, and urinary metabolites like VOCs, bisphenol, and triclosan. Participants were categorized by living floors: banjihas, first-fifth floors, and sixth floors or higher. Twenty-five children (4.3%) lived in banjihas, 311 (54.1%) on the first to fifth floor, and 239 (41.6%) on the sixth floor or above. Despite similar levels of allergen sensitization and urinary pollutant metabolite levels across all groups, banjiha dwellers showed significantly higher total airway resistance (adjusted &1: 0.633, 95%CI: 0.156, 1.109; P = 0.009) and a greater prevalence of elevated FeNO levels (> 35 ppb) (P = 0.033). These findings persisted after adjusting for critical factors like height, gender, BMI z-score, and birth conditions. Children in banjihas exhibit elevated airway resistance and FeNO levels independently of allergen sensitization or pollution exposure, underscoring the necessity for enhanced focus on their respiratory health in such living conditions.

Pulmonary functions, nasal symptoms, and quality of life in patients with primary ciliary dyskinesia (PCD).

Several factors may influence quality of life (QOL) for patients with primary ciliary dyskinesia (PCD). We aimed to evaluate the association between pulmonary functions, nasal symptoms and QOL in PCD patients. A prospective single center study. Patients performed spirometry, whole body plethysmography, forced oscillation technique (FOT), lung clearance index (LCI), 6-min walk test (6MWT), and filled two questionnaires: a specific PCD QOL questionnaire (PCD-QOL) and Sino-nasal outcome test (SNOT-22) questionnaire, assessing symptoms of chronic rhinosinusitis and health related QOL. Twenty-seven patients (56% females), age 19.4 ± 10.5 years were included; their, FEV1 was 74.6 ± 22.7%, and RV/TLC was (157.3 ± 39.3% predicted). Health perception and lower respiratory symptoms domains of PCD-QOL had the lowest score (median [IQR]: 50 [33.3-64.6] and 57.1 [38.9-72.2], respectively). FOT parameters correlated with several PCD-QOL domains. R5 z-score (indicating total airway resistance) and AX z-score (indicating airway reactance) correlated negatively with physical domain (r = -0.598, p = .001, and r = -0.42, p = .03, respectively); R5 z-score also correlated negatively with hearing domain (r = -0.57, p = .002). R5-20 z-score (indicating small airway resistance) correlated negatively with role domain (r = -0.49, p = .03). SNOT-22 score correlated negatively with several PCD-QOL domains (lower respiratory symptoms r = -0.77, p < .001; physical r = -0.72, p < .001; upper respiratory symptoms r = -0.66, p < .001). No correlations were found between spirometry values, LCI, 6MWT, and PCD-QOL. FOT suggested small airway dysfunction, and correlated negatively with several PCD-QOL domains. Nasal symptoms had strong negative correlations with PCD-QOL. Larger longitudinal studies will further elucidate factors affecting QOL in PCD.

Does Mild Coronavirus Disease 2019 Pneumonia in Healthy Adults Cause Permanent Small Airway Injury?

Impulse oscillometry (IOS) is a type of oscillation technique that measures the input impedance (Z) of the respiratory system and can be used to detect pathological changes in the small airways at an early stage. Although coronavirus disease 2019 (COVID-19) affects the vascular and parenchymal structures in the lung, chronic postinfection coughs also may be attributed to small airway pathologies. Our research aimed to use IOS for the assessment of the presence of small airway resistance (R) in patients who have had COVID-19. Thirty-eight patients with past COVID-19 infections and without any presence or medical treatment of an airway disease who presented to the post-COVID outpatient clinic with coughing symptoms were included in the study. The control group consisted of 17 patients with no past COVID-19 infection and without an airway disease. IOS and spirometry were performed twice in the case group, at 3 and 6 months after COVID-19. The mean age of the case group was 44.7 ± 12.3 years, whereas the mean age of the control group was 49.4 ± 11.8 years. The case group consisted of 38 patients, whereas 17 patients constituted the control group. No statistically significant difference was found between the two groups in the first and second test measurements, performed 3 months apart (P > 0.05). The fact that there was no difference between respiratory system impedance, airway resistance, and spirometry values between groups with and without past COVID-19 infections supported the hypothesis that small airways were not affected 3 months after COVID-19.

Household Air Pollution and Child Lung Function: The Ghana Randomized Air Pollution and Health Study.

Rationale: The impact of a household air pollution (HAP) stove intervention on child lung function has been poorly described. Objectives: To assess the effect of a HAP stove intervention for infants prenatally to age 1 on, and exposure-response associations with, lung function at child age 4. Methods: The Ghana Randomized Air Pollution and Health Study randomized pregnant women to liquefied petroleum gas (LPG), improved biomass, or open-fire (control) stove conditions through child age 1. We quantified HAP exposure by repeated maternal and child personal carbon monoxide (CO) exposure measurements. Children performed oscillometry, an effort-independent lung function measurement, at age 4. We examined associations between Ghana Randomized Air Pollution and Health Study stove assignment and prenatal and infant CO measurements and oscillometry using generalized linear regression models. We used reverse distributed lag models to examine time-varying associations between prenatal CO and oscillometry. Measurements and Main Results: The primary oscillometry measure was reactance at 5 Hz, X5, a measure of elastic and inertial lung properties. Secondary measures included total, large airway, and small airway resistance at 5 Hz, 20 Hz, and the difference in resistance at 5 Hz and 20 Hz (R5, R20, and R5-20, respectively); area of reactance (AX); and resonant frequency. Of the 683 children who attended the lung function visit, 567 (83%) performed acceptable oscillometry. A total of 221, 106, and 240 children were from the LPG, improved biomass, and control arms, respectively. Compared with control, the improved biomass stove condition was associated with lower reactance at 5 Hz (X5 z-score: β = -0.25; 95% confidence interval [CI] = -0.39, -0.11), higher large airway resistance (R20 z-score: β = 0.34; 95% CI = 0.23, 0.44), and higher AX (AX z-score: β = 0.16; 95% CI = 0.06, 0.26), which is suggestive of overall worse lung function. The LPG stove condition was associated with higher X5 (X5 score: β = 0.16; 95% CI = 0.01, 0.31) and lower small airway resistance (R5-20 z-score: β = -0.15; 95% CI = -0.30, 0.0), which is suggestive of better small airway function. Higher average prenatal CO exposure was associated with higher R5 and R20, and distributed lag models identified sensitive windows of exposure between CO and X5, R5, R20, and R5-20. Conclusions: These data support the importance of prenatal HAP exposure on child lung function. Clinical trial registered with www.clinicaltrials.gov (NCT01335490).

Impact of Heated Tobacco Products, E-Cigarettes, and Combustible Cigarettes on Small Airways and Arterial Stiffness.

Smoking cessation is difficult but maintaining smoke-free without nicotine replacement therapy is even harder. During the last few years, several different alternative products, including heated tobacco products (HTP), have been introduced to the market. In this study, we investigated the acute effects of IQOSTM and gloTM (two HTP) consumption on small airway function and arterial stiffness in a head-to-head design, comparing them to combustible cigarettes, nicotine-free e-cigarettes and a sham smoking group. Seventeen healthy occasional smokers were included in a single-center, five-arm, crossover study. The parameters of small airway function and hemodynamics were collected at several time points before and after consumption using Mobil-O-Graph™ (I.E.M., Stolberg, Germany) and TremoFlo® c-100 (THORASYS Thoracic Medical Systems Inc., Montreal, QC, Canada). Small airway obstruction and resistance were both significantly increased after the consumption of cigarettes and substitute products. All products containing nicotine led to similar significant increases in blood pressure and arterial stiffness. Hemodynamic parameters were also increased after the consumption of e-cigarettes without nicotine, but compared to nicotine-containing products, the increase was shorter and weaker. We conclude that, although it has yet to be determined why, HTP have acute harmful effects on small airway function, possibly even exceeding the effects of combustible cigarettes. Like other nicotine-containing products, HTP leads to a nicotine-related acute increase in arterial stiffness and cardiovascular stress, similar to combustible cigarettes, which associates these products with an increased cardiovascular risk.

Small airways in asthma: Pathophysiology, identification and management.

The aim of this review is to summarize the current evidence regarding small airway disease in asthma, focusing on recent advances in small airway pathophysiology, assessment and therapeutic implications. A search in Medline was performed, using the keywords "small airways", "asthma", "oscillometry", "nitrogen washout" and "imaging". Our review was based on studies from adult asthmatic patients, although evidence from pediatric populations is also discussed. In asthma, inflammation in small airways, increased mucus production and airway wall remodelling are the main pathogenetic mechanisms of small airway disease. Small airway dysfunction is a key component of asthma pathophysiology, leading to increased small airway resistance and airway closure, with subsequent ventilation inhomogeneities, hyperresponsiveness and airflow limitation. Classic tests of lung function, such as spirometry and body plethysmography are insensitive to detect small airway disease, providing only indirect measurements. As discussed in our review, both functional and imaging techniques that are more specific for small airways, such as oscillometry and the multiple breath nitrogen washout have delineated the role of small airways in asthma. Small airways disease is prevalent across all asthma disease stages and especially in severe disease, correlating with important clinical outcomes, such as asthma control and exacerbation frequency. Moreover, markers of small airways dysfunction have been used to guide asthma treatment and monitor response to therapy. Assessment of small airway disease provides unique information for asthma diagnosis and monitoring, with potential therapeutic implications.

In symptomatic patients on as-needed inhaled corticosteroids-formoterol, VAS asthma is associated with small airways resistance

Objectives Impulse oscillometry (IOS) can demonstrate small airways disease even when spirometry values are normal. However, it is unknown if the absence of symptoms excludes increased small airways resistance in asthma patients. We aimed to correlate symptoms (assessed through visual analogue scales) with measures of small airways resistance in patients with asthma and to determine whether less symptomatic patients have increased small airways resistance. Methods We conducted a single center, prospective cohort study. We included controlled asthma patients on as-needed inhaled corticosteroids-formoterol. Patients were evaluated on their symptom VASs, Spirometry and IOS (with R5-R20% measuring small airways resistance) which were measured both in periods when they were less symptomatic and symptomatic. Symptoms were assessed using MASK-air®, an mHealth app that includes a daily monitoring questionnaire with validated VASs. We correlated MASK-air VASs with small airways resistance. Results We assessed 29 patients. There was a significant correlation between VAS asthma and R5-R20% in symptomatic periods (r = 0.43; 95% CI = 0.13;0.68, p = 0.019), but not in less symptomatic periods (0.04; 95% CI-0.40;0.46; p = 0.825). In less symptomatic periods, patients presenting with low VAS asthma (VAS < 30) displayed a lower median R5-R20% than the remainder (0.26 versus 0.35), as well as a lower R5% (0.13 versus 0.15) (p < 0.001). In 68.9% of less symptomatic patients, R5-R20 values remained higher than normal values. Conclusion In symptomatic patients on as-needed inhaled corticosteroids-formoterol, VAS asthma was associated with small airways resistance. However, even if these patients are less symptomatic, small airways resistance may be higher than normal. Since SAD significantly affects asthma control, patients should be carefully followed-up, even in less symptomatic periods.

Lifestyle practices that reduce seasonal PM2.5 exposure and their impact on COPD

Particulate matter (PM) is a major air pollutant that has led to global health concerns and can cause and exacerbate chronic obstructive pulmonary disease (COPD). We asked patients with COPD to complete a detailed questionnaire about their lifestyle practices to reduce PM2.5 exposure and analyzed the relationship between ambient PM2.5 concentrations and lifestyle practices. We prospectively enrolled 104 COPD patients from four hospitals in different areas of Korea. They completed detailed questionnaires twice (at enrollment and the end of the study) and Internet of Things-based sensors were installed in their homes to continuously measure PM2.5 for 1 year. The relationship between PM2.5 concentrations, lifestyle practices, and COPD exacerbations were analyzed in each season. The PM2.5 concentration was higher outdoors than indoors in all seasons except summer, and the difference was largest in winter. The six lifestyle practices that significantly lowered the annual indoor PM2.5 concentration compared with the outdoors. The higher the economic status and educational level of patients, the lower the indoor PM2.5 concentration. Some lifestyle practices were associated with reduced small airway resistance, presented as R5–R20 determined by impulse oscillometry, and scores of the St. George’s Respiratory Questionnaire. Some lifestyle practices are associated with reduced indoor PM2.5 concentrations and can even affect clinical outcomes, including small airway resistance and quality of life of COPD patients.

Effectiveness of sublingual immunotherapy with house dust mite drops in asthmatic children at different ages.

Respiratory allergies in children, such as asthma and rhinitis, are becoming progressively common every year. Recent studies found that pediatric patients with asthma receiving regular medication and specific immunotherapy (SIT) had improved therapeutic outcomes in a wide age range. However, there are few studies that have examined the effectiveness of SIT treatment in children with allergic asthma at different ages in terms of the degree of asthma control, improvements in lung function, and changes in exhaled nitric oxide (FeNO). A total of 200 asthmatic pediatric patients who had been receiving regular treatment for at least a year were split into the observation and the control groups, which depended on whether sublingual immunotherapy was added based on conventional treatment medicines. The children who were divided by an age cut-off of 6 years old in these two groups were compared before and after therapy based on the exhaled levels of FeNO, pulmonary function, visual analog scale, medication scores, daytime and nighttime ratings of asthma symptom, and rhinitis symptom scores. Before treatment, there was no significant difference between the observation group and the control group in various indicators of the patients under 6 years old; and in the older children (6-16 years old) group, the scores of FVC, FEV1, and FEF25 in the observation group were significantly lower than those in the control group (P < 0.05). The FEF75, FEF50, FEF25, and MMEF75/MMEF25 indexes in the observation group were significantly higher than those in the control group after treatment (P < 0.05), but there was no statistical significance in other indexes (P > 0.05). The scores of ACT, FEF75, FEF50, MMEF72/MMEF25, and FeNO in the observation group were all higher than those in the control group after treatment (P < 0.05), and the differences in other indexes were not statistically significant (P > 0.05). Between the young-age group and the elder group, there was no significant difference in all indexes in the observation group before and after treatment (P > 0.05). Children with asthma of all ages can considerably benefit from sublingual immunotherapy. Specifically, younger patients showed greater tendency on the improvement of small airway resistance, whereas school-age children with asthma significantly improved their small airway resistance as well as their asthma control and inflammation alleviation.

Impact of Aerobika® oscillating positive expiratory pressure in improving small airway resistance, lung function, symptoms and exercise capacity in chronic obstructive pulmonary disease.

Aerobika® oscillating positive expiratory pressure (OPEP) device promotes airway clearance in many respiratory diseases. However, studies have yet to focus on its effectiveness in improving small airway resistance via impulse oscillometry (IOS) measurement in COPD subjects. We aim to evaluate the improvement of small airway resistance (via IOS), lung function (spirometry), exercise capacity [via 6-min walking test (6MWT)], symptoms [COPD assessment test (CAT)] and severe exacerbation events among COPD subjects using Aerobika® OPEP. This was a prospective, single-arm interventional study among COPD subjects with small airway disease. Subjects were instructed to use twice daily Aerobika® OPEP (10 min each session); for 24 weeks; as an additional to standard therapy. IOS, spirometry, 6MWT, CAT score and severe exacerbation events were evaluated at baseline, 12 weeks and 24 weeks. Fifty-three subjects completed the study. Aerobika® usage showed improvement of IOS parameters; e.g. measurement of airway resistance at 5 Hz (R5), cmH20/L/s, (12-week p = 0.008, 24-week p < 0.001), R5% predicted (12-week p = 0.007, 24-week p < 0.001) and small airway resistance (R5-R20), cmH20/L/s, (12-week p = 0.021, 24-week p < 0.001). There were improvement of lung function; e.g. FEV1, L (12-week p = 0.018, 24-week p = 0.001), FEV1% predicted (12-week p = 0.025, 24-week p = 0.001), FEF25-75, L (12-week p = 0.023, 24-week p = 0.002), and FEF25-75% predicted (12-week p = 0.024, 24-week p < 0.001). CAT score improved at 12 weeks (p < 0.001) and 24 weeks (p < 0.001). Subjects had improved exercise capacity (6MWT, metres) after 24 weeks (p = 0.016). However, there was no significant difference in severe exacerbation events 24 weeks before and after Aerobika® usage. Aerobika® OPEP demonstrated significant improvement in small airway resistance as early as 12 weeks of usage, with sustained improvement at 24 weeks. Aerobika® OPEP administration had significantly improved lung function, 6MWT, and CAT scores over 24 weeks. There was no difference in severe exacerbation events.

Assessment of small airway dysfunction by impulse oscillometry (IOS) in COPD and IPF patients.

Small airway dysfunction is a pathological component of chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), and impulse oscillometry is an easy-to-administer, effort-independent non-invasive test reflecting small airway dysfunction. We aimed to compare the impulse oscillometry (IOS) measurements between COPD and IPF patients and investigate their correlation with severity of both diseases and other conventional parameters. This was a prospective, longitudinal study. We longitudinally evaluated the baseline demographic characteristics, COPD Assessment Test (CAT) and modified Medical Research Council (mMRC) dyspnea scale, Pulmonary Function Test (PFT), Carbon Monoxide Diffusing Capacity (DLCO), Hemogram and Impulse Oscillometry measurements of the patients diagnosed with COPD and IPF. The study included 60 IPF patients and 48 COPD patients. The CAT and mMRC scores were higher in COPD patients. The majority of COPD patients were classified into Category B (46%), while 68% of IPF patients had Stage 1 GAP. The mean FEF 25-75%, which is typically considered to reflect small airway disease, was 93% in IPF patients, while it was significantly lower in COPD patients (29%). Impulse oscillometry measurements were consistent with spirometry parameters. IOS resistance and reactance values were significantly higher in COPD patients than in IPF patients. IOS is advantageous in COPD and IPF patients who cannot exhale due to severe dyspnea, as it is easy to administer and reflects small airway resistance better. Diagnosis of small airway dysfunction may be beneficial in the management of patients with IPF and COPD.

The impact of adenoid hypertrophy on pulmonary functions measured using impulse oscillometry in preschool-age children.

To assess pulmonary impedance [resistance (zR5, zR20, R5-20, Fres, and AX) and reactance (zX5 and zX20)] using impulse oscillometry (IOS) in children with adenoid hypertrophy (AH) and its association with the degree of AH, and to evaluate subsequent changes in pulmonary function 3 months after adenoidectomy. This prospective cross-sectional study was conducted with 170 preschool-age children [110 with AH and 60 sex- and age-matched healthy controls (HCs)]. Pulmonary function was analyzed using IOS at baseline (1st visit) in all participants and 3 months after adenoidectomy (2nd visit) in patients who underwent the operation. The IOS parameters of zR5, zR20, R5-20, Fres, and AX were higher, but zX20 was lower, in children with AH compared to the HCs (p < 0.05 for all). The parameters of zR5, Fres, and AX were higher in children with grade IV AH than in those with grade I (p < 0.001). zR5, zR20, R5-20, Fres, and AX decreased, but zX20 increased, after adenoidectomy (2nd visit) compared to baseline (1st visit) (p < 0.05). Post-adenoidectomy (2nd visit) zR5, AX, Fres values were higher in children with AH compared to baseline values in the HCs (1st visit) (p < 0.05). The area under the ROC curve (AUC) value for estimating adenoidectomy was 0.741 forzX20 (CI 0.648-0.834,p < 0.001) with a cut-off value of ≤ -3.21, sensitivity of 68.8%, and specificity of 70%. This study shows that IOS is a useful method for demonstrating subclinical bronchial obstruction in preschool-age children with AH with greater pulmonary impedance (resistance and reactance). Pulmonary impedance decreased 3 months after adenoidectomy, but remained higher than in the HCs. The IOS parameter of X20 may be predictive of adenoidectomy. This study evaluated the pulmonary functions of children with adenoid hypertrophy (AH) using impulse oscillometry (IOS) and the association with the scale of AH. Pulmonary functions were analyzed using IOS. The main IOS parameters include resistances (zR5 and zR20), reactance (zX5 and zX20), R5-20 (resistance at 5 Hz minus resistance at 20 Hz), resonant frequency (Fres), and AX. Fres is the point at which reactance is zero and is measured in Hz (1/s). The Reactance Area (AX - "Goldman Triangle") represents the integrated low-frequency respiratory reactance magnitude between 5 Hz and Fres. Faster frequencies of R (~ 20 Hz) reflect larger airways, regarded as resistance around the central airways. Lower frequencies of R (~ 5 Hz) providing information around the entire (small and large) airways. Peripheral (small) airway resistance is defined by R5-20. IOS parameters of zR5, zX20, Fres, and AX differed among AH grades I-IV and compared to the HCs (p < 0.001 for all).

Determinants of asthma control and exacerbations in moderate to severe asthma

Determinants of asthma control and exacerbations in moderate to severe asthma

A LONGITUDINAL STUDY OF IMPULSE OSCILLOMETRY AND RESPIRATORY MECHANICS IN PREGNANCY: IMPLICATIONS FOR RESPIRATORY DISORDERS

TYPE: Late Breaking Abstract TOPIC: Pulmonary Physiology PURPOSE: Examine positional and longitudinal changes in airway resistance and reactance during early and late pregnancy. METHODS: A longitudinal observational study enrolled pregnant women in the first trimester. Impedance oscillometry was performed in the seated, supine, and most comfortable sleeping positions in early and late pregnancy. Airway resistance was measured at 5 and 20Hz, reactance at 5Hz. Lung volumes were simultaneously measured in the seated and supine positions. Progesterone and estradiol were measured at two time points. RESULTS: 242 women (59% White) were enrolled with mean BMI 34.4 Kg/m2, 135 with longitudinal measurements. Airway resistance and reactance significantly increased with the change from the seated to the supine, and to the most comfortable sleeping position, in early and late pregnancy (p<0.00001). Most comfortable sleeping position was associated with lower resistive load than supine position (p<0.0006). Airway resistance significantly increased with pregnancy progression (p<0.004) and related to increased small airway resistance (R5-R20Hz P=0.009). Increased airway resistance did not correlate with changes in serum progesterone. Airway reactance increased with pregnancy progression (P<0.00001). FRC dropped with position change at both time points (p<0.00001) but not with pregnancy progression. ERV dropped (13.3%) with pregnancy progression (p<0.00001). CONCLUSIONS: Resistive and elastic loads increase in the supine position in early and late pregnancy and with pregnancy progression. Resistive load increases with pregnancy progression relate mostly to increased small airway resistance, which may be due to reduced ERV. CLINICAL IMPLICATIONS: Increased resistive loads may contribute to asthma exacerbations, while increased elastic loads may contribute to respiratory complications in women with obesity or chest wall abnormalities. DISCLOSURE: No significant relationships. KEYWORD: airway resistance

High-flow nasal cannula improves respiratory impedance evaluated by impulse oscillometry in chronic obstructive pulmonary disease patients: a randomised controlled trial

Non-pharmacological treatment with high-flow nasal cannula (HFNC) may play a vital role in treatment of patients with chronic obstructive pulmonary disease (COPD). To evaluate the efficacy of HFNC, impulse oscillation system (IOS) is a new noninvasive technique in measuring the impedance of different portions of lungs. It shows higher sensitivity in contrast to conventional pulmonary function tests (PFT). However, whether IOS is an appropriate technique to evaluate the efficacy of HFNC in improving the impedance of small airways or peripheral lung in patients with COPD is still unclear. We enrolled 26 stable COPD participants randomised into two groups receiving HFNC or nasal cannula (NC) for 10 min followed by a 4-week washout period and crossover alternatively. IOS was used to detect the difference of respiratory impedance after HFNC or NC interventions. IOS parameters, PFT results, transcutaneous partial pressure of carbon dioxide, peripheral oxygen saturation, body temperature, respiratory rate, pulse rate, and blood pressure at the time of pre-HFNC, post-HFNC, pre-NC, and post-NC, were collected and analysed using SPSS (version 25.0, IBM, Armonk, NY, USA). The IOS measurement indicated that HFNC significantly improved R5, R5% predicted, R5–R20, X5-predicted, and Fres compared with NC, whereas no significant difference was observed through the PFT measurement. The beneficial effect of HFNC in improving small airway resistance and peripheral lung reactance compared with that of NC in patients with stable COPD was confirmed through IOS measurement.Trial registration: ClinicalTrials.gov NCT05130112 22/11/2021.

Chronic Lung Allograft Dysfunction with Expiratory Flow Limitation: A Novel Sub-Phenotype Associated with Increasing Small Airway Resistance and CLAD Severity

<h3>Purpose</h3> Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation, dyspnoea and exercise limitation in obstructive lung disease. Within breath respiratory system reactance, measured by oscillometry, accurately detects EFL. The aim of this study is to assess predictors of EFL in recipients with chronic lung allograft dysfunction (CLAD). <h3>Methods</h3> A cross-sectional study was performed on bilateral lung transplant (LTx) recipients with persistent lung allograft dysfunction at 2 Australian centres between Jan-20 and Jun-21. Spirometry and oscillometry (TremoFlo C-100) were performed to obtain FEV₁, FVC and X_rs at 5Hz, R_5-19 respectively. EFL was defined as [mean inspiratory - mean expiratory X_rs (∆Xrs)] > 2.53. Patients with CLAD, based on 2019 Consensus criteria and phenotyping, were included. Recipients with non-CLAD causes of lung allograft dysfunction were excluded. Logistic regression measured the association between demographic and physiologic predictors and risk of EFL. <h3>Results</h3> A total of 110 bilateral lung transplant recipients with persistent lung allograft dysfunction were enrolled. 20 patients were excluded and 90 with confirmed CLAD were included for final analysis. EFL was observed in 16 (17.8%) patients. The median (IQR) ∆Xrs in recipients with EFL was 3.40 (2.10) compared to -0.14 (1.37) in those without. In univariable analysis, reduced concurrent FEV₁/FVC (OR 0.01 95%CI 0.00-0.43, p=0.018), reduced concurrent FEV₁ as %-baseline (OR 0.02 95%CI 0.00-0.72, p=0.03) and increased R_5-19 Z-Score (OR 1.30 95%CI 1.11-1.52, p=0.001) were associated with an increased risk of EFL. Recipient BMI (OR 1.07 95%CI 0.99-1.16, p=0.09) was positively correlated with EFL with a weak association. CLAD BOS phenotype (BOS OR 0.82 95%CI 0.25-2.64, p=0.73) was not associated with an increased risk of EFL compared to other phenotypes. <h3>Conclusion</h3> EFL occurs in a minority of patients with CLAD, and occurs both in BOS and non-BOS phenotypes. Increasing airflow obstruction, CLAD severity and small airway resistance (R_5-19) are associated with an increased risk of EFL. Advanced fibroproliferative small airway obstruction likely explains these associations. CLAD with EFL may be associated with poor outcomes and routine monitoring with oscillometry may be beneficial.