Evaluation of the learning effect on the 6-min walk distance in adults with long COVID.

There was no learning effect found on 6-min walk distance (6MWD) in patients with long COVID, performing a 6-min walk test twice. However, considerable variation in the difference between the two 6MWDs was observed: only 51% showed an increase. https://bit.ly/3H70G1r.

Effects of Weight Change and Weight Cycling on Lung Function in Overweight and Obese Adults.

Rationale: Epidemiological studies have reported on the detrimental effects on lung function after natural, and thus limited, weight gain in unselected populations. Studies on bariatric surgery, on the contrary, have indicated large improvements in lung function after substantial weight loss. Objectives: To study the associations between profound weight loss or gain and pulmonary function within the same population. A second objective was to investigate the effect of weight cycling on pulmonary function. Methods: From our lung function database, we selected the records of subjects in follow-up for continuous positive airway pressure therapy for sleep apnea with a weight change of ⩾20 kg within 5 years. Lung function (N = 255) at baseline was normal except for a tendency toward mild restriction in morbid obesity. Within this sample, 73 subjects were identified with significant "weight cycling", defined as a ⩾10-kg opposite change in body weight before or after the ⩾20-kg weight change. Results: Weight change affected pulmonary function more in men than in women (P < 0.001). In men, forced vital capacity (FVC) increased an average of 1.4% predicted per unit of body mass index after weight loss and the reverse after weight gain, whereas women exhibited a smaller change of 0.9% predicted per unit of body mass index. Weight loss slightly increased the ratio of forced expiratory volume in 1 second to FVC and decreased the specific airway resistance, whereas the opposite occurred with weight gain. Greater effects of weight change on lung function were observed in leaner subjects (P = 0.02) and in older subjects (P < 0.002). Changes in total lung capacity followed the changes in FVC, with no change in residual volume, and the greatest change was observed in functional residual capacity. In subjects with weight cycling, the improvement in lung function due to weight loss was reversed by subsequent weight gain and vice versa. Conclusions: This study provides evidence that the detrimental effect of obesity on lung function is a passive and reversible process.

Randomised, controlled, open-label pragmatic trial evaluating changes in functional exercise capacity after primary care PUlmonary REhabilitation in patients with long COVID: protocol of the PuRe-COVID trial in Belgium.

INTRODUCTION: Long COVID is a prevalent condition with many multisystemic symptoms, such as fatigue, dyspnoea, muscle weakness, anxiety, depression and sleep difficulties, impacting daily life and (social and physical) functioning. Pulmonary rehabilitation (PR) may improve physical status and symptoms of patients with long COVID, yet the evidence is limited. Therefore, this trial aims to study the effect of primary care PR on exercise capacity, symptoms, physical activity and sleep in patients with long COVID. METHODS AND ANALYSIS: PuRe-COVID is a prospective, pragmatic, open-label, randomised controlled trial. A sample of 134 adult patients with long COVID will be randomised to a 12 week PR programme in primary care, supervised by a physiotherapist or to a control group, following no PR. A 3 month and 6 month follow-up period is foreseen. The primary endpoint will be the change in exercise capacity measured by 6-minute walk distance (6MWD) at 12 weeks, hypothesising a more significant improvement in the PR group. Other parameters, such as pulmonary function tests (including maximal inspiratory pressure/maximal expiratory pressure), patient-reported outcomes (COPD Assessment Test, modified Medical Research Council Dyspnoea Scale, Checklist Individual Strength, post-COVID-19 Functional Status, Nijmegen questionnaire, Hospital Anxiety and Depression Scale, Work Productivity and Activity Impairment Questionnaire and EuroQol-5D-5L), physical activity measured by an activity tracker, hand grip strength and sleep efficiency, are secondary and exploratory outcomes.The recruitment started on 19 April 2022, and 52 patients were included as of 14 December 2022. ETHICS AND DISSEMINATION: Ethical approval was obtained in Belgium from the relevant institutional review boards on 21 February 2022 (Antwerp University Hospital, approval number 2022-3067) and on 1 April 2022 (Ziekenhuis Oost-Limburg in Genk, approval number Z-2022-01). Findings from this randomised controlled trial will be disseminated in peer-reviewed publications and presentations at international scientific meetings. TRIAL REGISTRATION NUMBER: NCT05244044.

Evaluation of the Global Lung Function Initiative reference equations in Belgian adults.

Background: Over the past decade, the Global Lung Function Initiative (GLI) Network has published all-age reference equations on spirometry, diffusing capacity of the lung for carbon monoxide (D LCO) and lung volumes. Methods: We evaluated the appropriateness of these equations in an adult Caucasian population. Retrospective lung function data on subjects who performed tests prior to a diagnostic sleep investigation were analysed. From the medical records, lung healthy, lifetime nonsmoking, nonobese subjects were selected, resulting in a population of 1311 subjects (68% male; age range 18-88 years). Results: Multiple linear regression analysis revealed that lung function z-scores did not differ between subjects with and without sleep apnoea but did depend on height and age. The average forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) z-score was 0 but exhibited an inverse association with height in both sexes (p<0.01). Values of FEV1 and FVC in both sexes were larger than predicted (mean±sd z-score +0.30±0.96 or 104±13% pred; p<0.01). Overall, static lung volumes and D LCO were adequately predicted. However, D LCO z-scores were inversely associated with height in males and age in females (p<0.01). For all lung function indices, the observed scatter was reduced compared with the prediction. Therefore, for all indices <5% of the data were below the GLI-proposed lower limit of normal (LLN) threshold. Conclusion: GLI reference equations provide an adequate fit in Belgian adults. However, the GLI-proposed LLN is too low for our Antwerp population, resulting in underdiagnosis of disease. Furthermore, airway obstruction and diffusion disorders might be misclassified due to height and age associations.

Clinical significance and applications of oscillometry.

Recently, "Technical standards for respiratory oscillometry" was published, which reviewed the physiological basis of oscillometric measures and detailed the technical factors related to equipment and test performance, quality assurance and reporting of results. Here we present a review of the clinical significance and applications of oscillometry. We briefly review the physiological principles of oscillometry and the basics of oscillometry interpretation, and then describe what is currently known about oscillometry in its role as a sensitive measure of airway resistance, bronchodilator responsiveness and bronchial challenge testing, and response to medical therapy, particularly in asthma and COPD. The technique may have unique advantages in situations where spirometry and other lung function tests are not suitable, such as in infants, neuromuscular disease, sleep apnoea and critical care. Other potential applications include detection of bronchiolitis obliterans, vocal cord dysfunction and the effects of environmental exposures. However, despite great promise as a useful clinical tool, we identify a number of areas in which more evidence of clinical utility is needed before oscillometry becomes routinely used for diagnosing or monitoring respiratory disease.

Technical standards for respiratory oscillometry.

Oscillometry (also known as the forced oscillation technique) measures the mechanical properties of the respiratory system (upper and intrathoracic airways, lung tissue and chest wall) during quiet tidal breathing, by the application of an oscillating pressure signal (input or forcing signal), most commonly at the mouth. With increased clinical and research use, it is critical that all technical details of the hardware design, signal processing and analyses, and testing protocols are transparent and clearly reported to allow standardisation, comparison and replication of clinical and research studies. Because of this need, an update of the 2003 European Respiratory Society (ERS) technical standards document was produced by an ERS task force of experts who are active in clinical oscillometry research.The aim of the task force was to provide technical recommendations regarding oscillometry measurement including hardware, software, testing protocols and quality control.The main changes in this update, compared with the 2003 ERS task force document are 1) new quality control procedures which reflect use of "within-breath" analysis, and methods of handling artefacts; 2) recommendation to disclose signal processing, quality control, artefact handling and breathing protocols (e.g. number and duration of acquisitions) in reports and publications to allow comparability and replication between devices and laboratories; 3) a summary review of new data to support threshold values for bronchodilator and bronchial challenge tests; and 4) updated list of predicted impedance values in adults and children.

Comparison of ERS'93 to the newly published GLI'17 reference values for carbon monoxide transfer factor.

BACKGROUND: The new predicted values for the carbon monoxide transfer factor (TL,CO) for Caucasians by the Global Lung Function Initiative are available since September 2017. Several authors have previously shown that the predicted values of Cotes et al. (ERS'93), overestimated TL,CO. However, the GLI'17 authors omitted to compare their predicted values with the ERS'93 equations, still in use throughout Europe. We present the differences between the two sets of predicted values, and in an attempt to improve the readability, used the contour plots instead of the classical 2-dimensional representations. METHODS: Predicted values were computed for males and females for ages between 18 and 70 years and heights between 155 and 180 cm using Matlab software with increments of one unit (1 yr, 1 cm). RESULTS: We demonstrate that GLI-'17 predicted values of TL,CO are systematically lower than those of ERS-'93, but also that the magnitude of the differences varies according to age, height and sex. More specifically, differences increase in both males and females by decreasing age and height, reaching up to 16% in males and 24% in females. CONCLUSION: The predicted values of TL,CO by Cotes at al. are systematically larger than the new GLI'17 values. Plotting all the possible differences between predicted variables using contour graphs allows to identify the groups of subjects in whom significant changes in their predicted values will occur. Our findings should prompt physicians to investigate how switching to GLI-17 equations affects the clinical interpretation of TL,CO measurements in a real-live setting.

Determinants of baseline lung function and bronchodilator response in 4-year-old children.

The prolonged period required for maturation of the respiratory system makes it vulnerable to environmental exposure. This study aimed to investigate the association between early-life factors and lung function in preschool children. Children aged 4 years, who were included in a prospective birth cohort, underwent lung function testing at baseline (n=535) and after bronchodilation (n=498) by forced oscillations. Information on symptoms and exposures was collected through half-yearly questionnaires. Allergen-specific serum IgE was quantified at 1 and 4 years. Multiple linear regression analysis showed that the baseline respiratory resistance and reactance area were larger in the children with previous wheeze, those with early-onset sensitisation to inhalant allergens and those who were smaller. Furthermore, children with previous lower respiratory tract infections exhibited higher baseline resistance values. The baseline resistance was the only independent determinant of the bronchodilator-induced change in resistance, whereas current height and baseline reactance area were independently associated with the change in reactance area. In conclusion, previous lower respiratory tract infections, the timing of previous wheeze, inhalant sensitisation and current height independently influence the baseline lung function of 4-year-old children, whereas baseline lung function is the principal determinant of the bronchodilator response.

An official American Thoracic Society workshop report: optimal lung function tests for monitoring cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheezing in children less than 6 years of age.

Although pulmonary function testing plays a key role in the diagnosis and management of chronic pulmonary conditions in children under 6 years of age, objective physiologic assessment is limited in the clinical care of infants and children less than 6 years old, due to the challenges of measuring lung function in this age range. Ongoing research in lung function testing in infants, toddlers, and preschoolers has resulted in techniques that show promise as safe, feasible, and potentially clinically useful tests. Official American Thoracic Society workshops were convened in 2009 and 2010 to review six lung function tests based on a comprehensive review of the literature (infant raised-volume rapid thoracic compression and plethysmography, preschool spirometry, specific airway resistance, forced oscillation, the interrupter technique, and multiple-breath washout). In these proceedings, the current state of the art for each of these tests is reviewed as it applies to the clinical management of infants and children under 6 years of age with cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheeze, using a standardized format that allows easy comparison between the measures. Although insufficient evidence exists to recommend incorporation of these tests into the routine diagnostic evaluation and clinical monitoring of infants and young children with cystic fibrosis, bronchopulmonary dysplasia, or recurrent wheeze, they may be valuable tools with which to address specific concerns, such as ongoing symptoms or monitoring response to treatment, and as outcome measures in clinical research studies.

Respiratory impedance in healthy subjects: baseline values and bronchodilator response.

Because of the minimal demand for cooperation by the subject, the forced oscillation technique is increasingly employed in routine lung function testing. However, comprehensive and device-independent values of respiratory impedance at baseline and after bronchodilation have not been established for healthy adults. The aim of this multicentre study was to collect impedance data from 4 to 26 Hz in healthy Caucasian subjects between 18 and 80 years of age. Five different devices were employed to assess baseline values and the bronchodilator response. Altogether, 368 subjects were examined. Despite adjustment for anthropometry, the impedance spectra differed in frequency dependence between the centres, and hence could not be pooled. However, resistance at all frequencies except 20 and 25 Hz, and the low-frequency (≤14 Hz) values of reactance did not exhibit a centre dependence. The regression equations for resistance reflected a greater height dependence in males and a greater weight dependence in both males and females than those published previously. Bronchodilation resulted in a statistically significant decrease (11%) in resistance and a 95th percentile equal to a 32% decrease in resistance at low frequency. We conclude that rigorous calibration procedures should be developed to ensure data compatibility. Furthermore, new reference equations based on different setups are recommended to replace those established with a single device.

Triggering for submaximal exercise level in gastric exercise tonometry: serial lactate, heart rate, or respiratory quotient?

Gastric exercise tonometry is a functional diagnostic test in chronic gastrointestinal ischemia. As maximal exercise can cause false-positive tests, exercise buildup should be controlled to remain submaximal. We evaluated three parameters for monitoring and adjusting exercise levels (heart rate [HR], respiratory quotient [RQ], and serial lactate measurements) in 178 tests in both healthy volunteers and patients suspected of gastrointestinal ischemia. Exercise levels above submaximal occurred in 20% of HR-, 2% of RQ-, and 5% of lactate-monitored tests (P<0.05 for HR vs. RQ and lactate). Low levels were seen in 5% of HR-, 10% of RQ-, and 41% of lactate-monitored tests (P<0.01 for lactate vs. HR and RQ). High levels resulted in 43% false-positive tonometry results compared to 19% of all tests (P<0.001); low levels did not result in more false negatives (5% vs. 6%). Although RQ monitoring yielded the greatest proportion of optimal exercise tests, serial lactate monitoring is our method of choice, combining optimal diagnostic accuracy, low cost, and simplicity.

Clinical impact of gastric exercise tonometry on diagnosis and management of chronic gastrointestinal ischemia.

BACKGROUND & AIMS: Chronic gastrointestinal ischemia or chronic splanchnic syndrome is a difficult diagnosis. The use of a physiologic test, combined with clinical and anatomic data, should improve diagnostic accuracy. This study evaluates the diagnostic accuracy and clinical impact of gastric tonometry during exercise (GET) in a patient cohort suspected of chronic splanchnic syndrome. METHODS: From 1997 to 2000, 102 patients with chronic abdominal pain were analyzed. The workup included GET and selective biplane angiography. The diagnosis of gastrointestinal ischemia was based on consensus in a multidisciplinary working group and sustained on follow-up. RESULTS: Gastrointestinal ischemia was diagnosed in 38 patients. In 33 patients chronic splanchnic syndrome was found, with single vessel involvement in 20 (17 celiac artery, 3 mesenteric superior) and multivessel disease in 13. In 5 patients nonocclusive ischemia was found. By using receiver operator curve analysis, the difference between gastric and arterial partial pressure of carbon dioxide (PCO2 gradient) proved to be the best GET parameter. The criteria for diagnosing ischemia in GET were Pco2 gradient > 0.8 kPa and increase gastric PCO2, with base excess decrease <8 mmol/L during exercise. GET had 78% sensitivity and 92% specificity. Twenty-five patients underwent vascular treatment (19 operative, 6 stent/percutaneous transluminal angioplasty). After 4 years of follow-up 83% of patients were alive and free of symptoms. CONCLUSIONS: GET is an accurate diagnostic tool to show gastrointestinal ischemia. Including GET into clinical decision making enabled selecting patients with ischemia, who benefited from vascular and medical treatment. These benefits were sustained during 4-year follow-up. GET should be considered in the workup of patients with a suspected diagnosis, of gastrointestinal ischemia.

Time-dependent effect of nitrate-rich meals on exhaled nitric oxide in healthy subjects.

BACKGROUND: Exhaled nitric oxide (eNO) is a convenient noninvasive marker for airway inflammation in several pulmonary diseases. However, external factors such as nitrate-rich nutrition can affect the levels of eNO and thus compromise its diagnostic value. STUDY OBJECTIVES: The objective of this investigation was to have a better understanding of the time-dependent effect of nitrate-rich meals on eNO in healthy subjects. STUDY DESIGN: Forty-two healthy, nonsmoking volunteers (age range, 25 to 62 years) were recruited for the study. They had no recent respiratory tract infections and were free of pulmonary history, rhinitis, and atopic disorders. eNO was measured before, and 0.5, 2, 4, 12, 15, and 20 h after the intake of a nitrate-rich meal equivalent to 230 mg of nitrate. RESULTS: The intake of a nitrate-rich meal increased eNO by 60% 2 h after the meal. Even after 15 h, the mean eNO value was still 22% higher than the baseline value. Only after 20 h did eNO return to the normal baseline level. CONCLUSION: This finding stresses the importance of advising patients to avoid nitrate-rich nutrition at least 20 h before a scheduled measurement of eNO.

Quantification of pharyngeal patency in patients with sleep-disordered breathing.

Many techniques are available for the assessment of pharyngeal characteristics in sleep-disordered breathing (SDB). However, most of the reported techniques are invasive to some extent and/or hard to perform during sleep studies. The focus of this concept paper is on the forced oscillation technique (FOT) to quantify pharyngeal patency in patients with SDB. In a pilot study, the potential of FOT for non-invasive and continuous assessment of pharyngeal patency during different types of respiratory events was studied in 8 patients with an established diagnosis of a sleep apnea-hypopnea syndrome. During polysomnography, FOT was applied using a 5-Hz pressure oscillation signal. The respiratory impedance was determined and considered as a marker for pharyngeal patency. The results demonstrate that FOT allows detection of the complete pharyngeal occlusion during obstructive sleep apnea. In addition, we found that central sleep apnea can be associated with pharyngeal closure. We also demonstrated that during the flow-limited breath preceding obstructive apnea, almost complete upper airway closure can occur during either the expiratory or the inspiratory phase. FOT is a suitable method to assess pharyngeal patency continuously and non-invasively during sleep. Furthermore, this technique has the potential to contribute substantially to our knowledge of upper airway physiology in SDB.