Assessment of partial pressure of carbon dioxide during incremental exercise test, in patients with chronic obstructive pulmonary disease

Abstract: Purpose: Respiratory pump failure in COPD patients can lead to CO2 retention during exercise, but little is known about the factors determining CO2-levels during exercise in COPD patients. The aim of this study is to investigate the pattern of TcPCO2 in COPD patients during exercise and factors driving this CO2 response. Patients and methods: 24 COPD patients (age 66(8) y, FEV1 43(18) %pred, TcPCO2 at rest 37(4) mmHg, oxygen users 6/24) performed lung function and cardiopulmonary exercise test (CPET). During CPET TcPCO2 was measured continuously and in O2 users the CPET was performed with supplemental oxygen. Results: At baseline, 16 patients were normocapnic (TcPCO2 35-45 mmHg) and 8 hypocapnic (TcPCO24mmHg) was observed in 18 patients. 06TcPCO2 correlated significantly with VeMax (r=-.64; p=.004), FEV1 %predicted (r = -.53; p = .008), RV %predicted (r = .54; p = .007), RV/TLC (r = .56; p = .005), sRAW (r =.61; p = .005), sGAW (r = -.60; p = .002), and maximal TcPCO2 (r=.63; p<.001), but did not correlate with baseline TcPCO2 (r = -.08; p = .728). Furthermore, baseline TcPCO2 correlated with the maximal TcPCO2 (r = 0.67; p < .001). Conclusion: The CO2-response of COPD-patients during CPET is heterogeneous with 10/24 developing hypercapnia. This study revealed that the lung mechanics are the most important factor correlating with CO2 retention during exercise while 06TcPCO2 was not associated with baseline TcPCO2

Unraveling pathophysiologic mechanisms contributing to symptoms in patients with post‐acute sequelae of COVID‐19 (PASC): A retrospective study

Abstract Patients with post‐acute sequelae of COVID‐19 (PASC) present with a decrease in physical fitness. The aim of this paper is to reveal the relations between the remaining symptoms, blood volume distribution, exercise tolerance, static and dynamic lung volumes, and overall functioning. Patients with PASC were retrospectively studied. Pulmonary function tests (PFT), 6‐minute walk test (6MWT), and cardiopulmonary exercise test were performed. Chest CT was taken and quantified. Patients were divided into two groups: minor functional limitations (MFL) and severe functional limitations (SFL) based on the completed Post‐COVID‐19 Functional Status scale (PCFS). Twenty one patients (3 M; 18 FM), mean age 44 (IQR 21) were studied. Eighteen completed the PCFS (8 MFL; 10 SFL). VO2max was suboptimal in both groups (not significant). 6MWT was significantly higher in MFL‐group (p = 0.043). Subjects with SFL, had significant lower TLC (p = 0.029). The MFL‐group had more air trapping (p = 0.036). Throughout the sample, air trapping correlated significantly with residual volume (RV) in L (p < 0.001). An increase in air trapping was related to an increase in BV5 (p < 0.001). Mean BV5 was 65% (IQR 5%). BV5% in patients with PASC was higher than in patients with acute COVID‐19 infection. This increase in BV5% in patients with PASC is thought to be driven by the air trapping in the lobes. This study reveals that symptoms are more driven by occlusion of the small airways. Patients with more physical complaints have significantly lower TLC. All subjects encounter physical limitations as indicated by suboptimal VO2max. Treatment should focus on opening or re‐opening of small airways by recruiting alveoli

Personalized pulmonary rehabilitation program for patients with post\u2010acute sequelae of COVID\u201019 : a proof\u2010of\u2010concept retrospective study

Abstract: Long\u2010COVID patients present with a decline in physical fitness. The aim of this study is to reveal the impact of pulmonary rehabilitation (PR) on physical fitness, quality of life (QoL), and parameters of quantified thorax CT. Long\u2010COVID patients enrolled in a 3\u2010month PR program were retrospectively studied. PR included endurance and resistance training three times a week. Assessments pre\u2010 and post\u2010rehabilitation included quantified chest CT, pulmonary function tests (PFT), six\u2010minute walk test (6MWT), cardiopulmonary exercise test, and questionnaires: Hospital Anxiety and Depression Scale, post\u2010COVID\u201019 Functional Status scale, Borg score, and EuroQol. Seventeen subjects (5M/12F), mean age 42\u2009\ub1\u200913\u2009years, were included. PR improved all questionnaires' results significantly. Only significant difference in PFT parameters was correlation between baseline total lung capacity (TLC) and difference in TLC pre\u2010 and post\u2010rehabilitation ( p \u2009=\u20090.002). 6MWT increased from 329 to 365\u2009m ( p \u2009<\u20090.001), VO2max changed from 21 to 24\u2009mL/kg/min ( p \u2009=\u20090.007), peak load increased from 116 to 141\u2009Watt ( p \u2009<\u20090.001). Blood volume in small pulmonary vessels of 1.25 to 5\u2009mm 2 in cross\u2010sectional area (BV5%) was higher than observed in patients with acute COVID\u201019 infection. After rehabilitation, BV5% decreased from 65% to 62% ( p \u2009=\u20090.020). These changes correlated directly with changes in TLC ( p \u2009=\u20090.039). Quantified CT airway volume increased after rehabilitation ( p \u2009=\u20090.013). After rehabilitation, TLC tended to normalize due to (re)opening of small airways, with decline in air trapping and recruitment of alveoli. Furthermore, this study revealed that pulmonary rehabilitation can improve QoL and physical fitness in long\u2010COVID patients

Exploring the link between a novel approach for computer aided lung sound analysis and imaging biomarkers: a cross-sectional study

Abstract Background Computer Aided Lung Sound Analysis (CALSA) aims to overcome limitations associated with standard lung auscultation by removing the subjective component and allowing quantification of sound characteristics. In this proof-of-concept study, a novel automated approach was evaluated in real patient data by comparing lung sound characteristics to structural and functional imaging biomarkers. Methods Patients with cystic fibrosis (CF) aged > 5y were recruited in a prospective cross-sectional study. CT scans were analyzed by the CF-CT scoring method and Functional Respiratory Imaging (FRI). A digital stethoscope was used to record lung sounds at six chest locations. Following sound characteristics were determined: expiration-to-inspiration (E/I) signal power ratios within different frequency ranges, number of crackles per respiratory phase and wheeze parameters. Linear mixed-effects models were computed to relate CALSA parameters to imaging biomarkers on a lobar level. Results 222 recordings from 25 CF patients were included. Significant associations were found between E/I ratios and structural abnormalities, of which the ratio between 200 and 400 Hz appeared to be most clinically relevant due to its relation with bronchiectasis, mucus plugging, bronchial wall thickening and air trapping on CT. The number of crackles was also associated with multiple structural abnormalities as well as regional airway resistance determined by FRI. Wheeze parameters were not considered in the statistical analysis, since wheezing was detected in only one recording. Conclusions The present study is the first to investigate associations between auscultatory findings and imaging biomarkers, which are considered the gold standard to evaluate the respiratory system. Despite the exploratory nature of this study, the results showed various meaningful associations that highlight the potential value of automated CALSA as a novel non-invasive outcome measure in future research and clinical practice