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W Darlene Reid,1,2 Cristiane Yamabayashi,1 Donna Goodridge,3 Frank Chung,4 Michael A Hunt,1 Darcy D Marciniuk,5 Dina Brooks,6 Yi-Wen Chen,1 Alison Hoens,1,7 Pat Camp1,21Department of Physical Therapy, University of British Columbia, Vancouver, 2Institute of Heart and Lung Health, University of British Columbia, Vancouver, 3College of Nursing, University of Saskatchewan, 4Physiotherapy, Burnaby Hospital, Fraser Health, British Columbia, 5Division of Respirology, Critical Care and Sleep Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, 6Department of Physical Therapy, University of Toronto, Toronto, ON, 7Providence Health Care, Vancouver, BC, CanadaIntroduction: The prescription of physical activity for hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) can be complicated by the presence of comorbidities. The current research aimed to synthesize the relevant literature on the benefits of exercise for people with multimorbidities who experience an AECOPD, and ask: What are the parameters and outcomes of exercise in AECOPD and in conditions that are common comorbidities as reported by systematic reviews (SRs)?Methods: An SR was performed using the Cochrane Collaboration protocol. Nine electronic databases were searched up to July 2011. Articles were included if they (1) described participants with AECOPD, chronic obstructive pulmonary disease (COPD), or one of eleven common comorbidities, (2) were an SR, (3) examined aerobic training (AT), resistance training (RT), balance training (BT), or a combination thereof, (4) included at least one outcome of fitness, and (5) compared exercise training versus control/sham.Results: This synthesis examined 58 SRs of exercise training in people with AECOPD, COPD, or eleven chronic conditions commonly associated with COPD. Meta-analyses of endurance (aerobic or exercise capacity, 6-minute walk distance – 6MWD) were shown to significantly improve in most conditions (except osteoarthritis, osteoporosis, and depression), whereas strength was shown to improve in five of the 13 conditions searched: COPD, older adults, heart failure, ischemic heart disease, and diabetes. Several studies of different conditions also reported improvements in quality of life, function, and control or prevention outcomes. Meta-analyses also demonstrate that exercise training decreases the risk of mortality in older adults, and those with COPD or ischemic heart disease. The most common types of training were AT and RT. BT and functional training were commonly applied in older adults. The quality of the SRs for most conditions was moderate to excellent (>65%) as evaluated by AMSTAR scores.Conclusion: In summary, this synthesis showed evidence of significant benefits from exercise training in AECOPD, COPD, and conditions that are common comorbidities. A broader approach to exercise and activity prescription in pulmonary rehabilitation may induce therapeutic benefits to ameliorate clinical sequelae associated with AECOPD and comorbidities such as the inclusion of BT and functional training.Keywords: pulmonary disease, chronic obstructive, comorbidity, exercise, physical fitness

BACKGROUND AND PURPOSE: The purpose of this study was to use quantitative and qualitative research methods to evaluate quality-of-life (QOL) changes in patients with chronic obstructive pulmonary disease after pulmonary rehabilitation. SUBJECTS: Twenty-nine individuals with COPD (18 women and 11 men), with a mean age of 69 years (SD=8.6, range=53-92), participated. METHODS: Subjects were assessed before and after a 5-week control phase and after a 5-week rehabilitation phase using the Chronic Respiratory Questionnaire (CRQ), the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and spirometry. Our qualitative research was based on a subsample of 7 subjects who were interviewed after pulmonary rehabilitation. RESULTS: Pulmonary rehabilitation improved QOL, as demonstrated by increases of 22% and 14% in the physical function categories of the CRQ and the SF-36, respectively, and by an increase of 10% in the CRQ's emotional function category. The qualitative data indicated how pulmonary rehabilitation influenced QOL. CONCLUSION AND DISCUSSION: The use of both quantitative and qualitative methods illustrated the nature of improvement in QOL after pulmonary rehabilitation. Improved physical function, less dyspnea, and a heightened sense of control over the subjects' COPD resulted in increased confidence and improved emotional well-being. [ABSTRACT FROM AUTHOR]

The purpose of this article is to describe respiratory muscle training techniques and the effectiveness of this training in patients with chronic obstructive pulmonary disease (COPD). The respiratory muscles can be strengthened, but the benefit of stronger respiratory muscles in patients with COPD is not clear. Maximal sustained voluntary ventilation, inspiratory resistive breathing, and threshold loading are the three most commonly used techniques for improving the endurance of the inspiratory muscles in patients with COPD. Recent studies using inspiratory resistive breathing with targeted devices or threshold trainers have shown more consistent increases in inspiratory muscle function and exercise tolerance than studies using other techniques. Endurance exercise involving the extremities improves inspiratory muscle endurance in younger individuals with cystic fibrosis but not in older persons with COPD. Recommendations are outlined regarding the techniques to use for respiratory muscle training and which patient populations may benefit from these techniques. [ABSTRACT FROM AUTHOR]

The purpose of this review is to describe the muscles of respiration, mechanisms that lead to their dysfunction, and unique features of the respiratory muscles that should be considered when designing testing and training protocols for patients with respiratory compromise. The diaphragm's unique shape is an important determinant of its function. Respiratory pathophysiology combined with systemic abnormalities may result in inspiratory muscle weakness, fatigue, and injury. The specificity of training principle, as it applies to respiratory muscle training in patients with respiratory compromise, will be described. Precautions related to this type of training will also be outlined. In conclusion, a better understanding of the mechanisms contributing to inspiratory muscle dysfunction will assist physical therapists in designing the most appropriate training programs. This article, along with the other articles in this focus on respiratory muscle training, will provide therapists with scientifically based guidelines for rehabilitation of patients with impaired respiratory muscle function. [ABSTRACT FROM AUTHOR]

Background: Manual breathing assist technique (MBAT) is a common physical therapy technique used to facilitate airway clearance and improve ventilation and oxygenation. The effects during and immediately after intervention in individuals with chronic obstructive pulmonary disease (COPD) are unknown. This study aimed to investigate the acute effects and potential mechanisms of MBAT on lung volume, dyspnea, and oxygenation in individuals with COPD., Methods: This non-randomized quasi-experimental pre-test/post-test study included participants from pulmonary rehabilitation programs at Tagami Hospital (COPD group) and a community exercise program (Healthy group). During a single session, MBAT was applied during the expiration of every breath for 10 minutes. Dyspnea and lung volumes (tidal volume; VT, inspiratory capacity; IC, inspiratory reserved capacity; IRV, expiratory reserve capacity; ERV) were collected at baseline and after MBAT. Pulse oximetry (SpO2), skeletal muscle oxygenation (SmO2), and oxy- and deoxy-hemoglobin (O2Hb and HHb) using near-infrared spectroscopy (NIRS) were collected at baseline, during, and after MBAT. Between-group comparisons were conducted using the Mann-Whitney U-test and chi-square analyses. Within-group changes before and after MBAT were analyzed using the Wilcoxon signed-rank test. The Kruskal-Wallis test was used to detect differences in NIRS variables in each phase and over time., Results: Thirty participants with COPD, matched for age and sex, were included, with 15 individuals per group. The difference scores of VT, IRV, and IC were significantly higher in the Healthy group than in the COPD group, but improvements in dyspnea and SpO2 were significantly higher in the COPD group. Compared to baseline, ERV decreased significantly in both groups, with dyspnea and SpO2 improving significantly only in the COPD group. Inspiratory accessory muscle ΔO2Hb and ΔHHb were significantly higher and lower (respectively) during MBAT in the COPD group compared to the Healthy group. Additionally, only the COPD group had increased SmO2 during and after MBAT compared to baseline., Conclusions: MBAT in patients with COPD had acute physiological effects in reducing dyspnea by facilitating expiration and decreasing the recruitment of accessory respiratory muscles. MBAT may help individuals with COPD reduce dyspnea before exercise therapy in a pulmonary rehabilitation program., Competing Interests: This work was conducted in accordance with ethical standards. The authors have no conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Prior studies of muscle blood flow and muscle-specific oxygen consumption have required invasive injection of dye and magnetic resonance imaging, respectively. Such measures have limited utility for continuous monitoring of the respiratory muscles. Frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy (FD-NIRS & DCS) can provide continuous surrogate measures of blood flow index (BF i ) and metabolic rate of oxygen consumption (MRO 2 ). This study aimed to validate sternocleidomastoid FD-NIRS & DCS outcomes against electromyography (EMG) and mouth pressure (Pm) during incremental inspiratory threshold loading (ITL). Six female and six male healthy adults (means ± SD; 30 ± 7 yr, maximum inspiratory pressure 118 ± 61 cmH 2 O) performed incremental ITL starting at low loads (8 ± 2 cmH 2 O) followed by 50-g increments every 2 min until task failure. FD-NIRS & DCS continuously measured sternocleidomastoid oxygenated and deoxygenated hemoglobin + myoglobin (oxy/deoxy[Hb + Mb]), tissue saturation of oxygen (StO 2 ), BF i , and MRO 2 . Ventilatory parameters including inspiratory Pm were also evaluated. Pm increased during incremental ITL ( P < 0.05), reaching -47[-74 to -34] cmH 2 O (median [IQR: 25%-75%]) at task failure. Ventilatory parameters were constant throughout ITL (all P > 0.05). Sternocleidomastoid BF i and MRO 2 increased from the start of the ITL (both P < 0.05). Deoxy[Hb + Mb] increased close to task failure, concomitantly with a constant increase in MRO 2 , and decreased StO 2 . Sternocleidomastoid deoxy[Hb + Mb], BF i , StO 2 , and MRO 2 obtained during ITL via FD-NIRS & DCS correlated with sternocleidomastoid EMG (all P < 0.05). In healthy adults, FD-NIRS & DCS can provide continuous surrogate measures of respiratory BF i and MRO 2 . Increasing sternocleidomastoid oxygen consumption near task failure was associated with increased oxygen extraction and reduced tissue saturation. NEW & NOTEWORTHY This study introduces a novel approach, frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy (FD-NIRS & DCS), for noninvasive continuous monitoring of respiratory muscle blood flow and metabolic rate of oxygen consumption. Unlike prior methods involving invasive dye injection and magnetic resonance imaging, FD-NIRS & DCS offers the advantage of continuous measurement without the need for invasive procedures. It holds promise for advancing muscle physiology understanding and opens avenues for real-time monitoring of respiratory muscles.

Topic Importance: Cognitive and physical limitations are common in individuals with chronic lung diseases, but their interactions with physical function and activities of daily living are not well characterized. Understanding these interactions and potential contributors may provide insights on disability and enable more tailored rehabilitation strategies., Review Findings: This review summarizes a 2-day meeting of patient partners, clinicians, researchers, and lung associations to discuss the interplay between cognitive and physical function in people with chronic lung diseases. This report covers four areas: (1) cognitive-physical limitations in patients with chronic lung diseases; (2) cognitive assessments; (3) strategies to optimize cognition and motor control; and (4) future research directions. Cognitive and physical impairments have multiple effects on quality of life and daily function. Meeting participants acknowledged the need for a standardized cognitive assessment to complement physical assessments in patients with chronic lung diseases. Dyspnea, fatigue, and age were recognized as important contributors to cognition that can affect motor control and daily physical function. Pulmonary rehabilitation was highlighted as a multidisciplinary strategy that may improve respiratory and limb motor control through neuroplasticity and has the potential to improve physical function and quality of life., Summary: There was consensus that cognitive function and the cognitive interference of dyspnea in people with chronic lung diseases contribute to motor control impairments that can negatively affect daily function, which may be improved with pulmonary rehabilitation. The meeting generated several key research questions related to cognitive-physical interactions in individuals with chronic lung diseases., Competing Interests: Financial/Nonfinancial Disclosures The authors have reported to CHEST the following: M. A. S. reports grants from Netherlands Lung Foundation, Stichting Astma Bestrijding, Chiesi, AstraZeneca, TEVA, and Boehringer Ingelheim, outside the submitted work; and fees from Boehringer Ingelheim, GSK, and AstraZeneca, outside the submitted work. (All grants and fees were paid to the institution of M. A. S.) A. G. K. reports funding for advisory board or speakers bureau roles for AstraZeneca, Belus, Boehringer Ingelheim, Eisai, GSK, Idorsia, Merck Frosst, Moderna, Novo Nordisk, Pfizer, Respiplus, Sanofi, Teva, Trudel, and Valeo. None declared (D. R., W. D. R., P. C., J. L. C., G. D., P. W. D., H. E., J. H. F., J. A. G., D. Gold, R. S. G., D. Goodridge, T. J.-F., D. L., D. D. M., B. M., A. O.-C., J. O.-A., V. P., P. R., S. R., C. R., M. B. S., M. K. S., J. T., K. W.)., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Exercise training post-transplant has been shown to improve physical function and quality of life in solid organ transplant (SOT) recipients. Online resources in the form of websites and videos are commonly used to provide education and instruction on exercise and physical activity in SOT; however, the content and quality of these online resources has not been evaluated., Methods: The first 200 websites and videos identified on Google and YouTube using the English search term "exercise and physical activity in solid organ transplantation" were analyzed. Website and video content was evaluated based on 25 key components of exercise and physical activity in SOT as described in established exercise program recommendations. Website and video quality was determined using DISCERN, Global Quality Scale (GQS), and Patient Education Materials and Assessment Tool (PEMAT; threshold for which material is deemed understandable or actionable is >70%). Parametric and non-parametric tests were used to assess website and video characteristics, content, and quality metrics., Results: Forty-nine unique SOT websites ( n  = 15) and videos ( n  = 34) were identified, with the two most common categories being foundation/advocacy organizations and scientific resources. The average reading grade level of websites was 13 ± 3. Website and video content scores varied significantly (websites 11.3 ± 6.4; videos 8.4 ± 5.3). DISCERN total score and GQS score were low (median range for DISCERN 2.5-3.0; median for GQS 2.0 for both websites and videos, out of 5). PEMAT understandability and actionability scores were also low across websites and videos (mean range 57%-67% and 47%-65%, respectively). Foundation/advocacy websites had higher content and quality scores compared to scientific organizations and news/media articles., Conclusions: To our knowledge, this is the first comprehensive assessment of online content and quality of website and video resources on physical activity and exercise in adult SOT recipients. There were a limited number of online English patient-directed resources related to physical activity in SOT, most of which only partly captured items outlined in consensus exercise program recommendations and were of low quality and understandability and actionability. This work provides important insight to the English-speaking transplant community on the current state of online exercise health information and provides future direction for resource development., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (© 2024 Da Silva, Momen, Al Kaabi, Masrur, Holdsworth, Prevost, Logan, Santa Mina, Mucsi, Bhat, Alba, Reid, Ferreira, Mathur, Janaudis-Ferreira, Wickerson and Rozenberg.)

Purpose: To compare deoxygenation of the sternocleidomastoid, scalenes, and diaphragm/intercostals (Dia/IC) during submaximal intermittent neck flexion (INF) versus submaximal inspiratory threshold loading (ITL) in healthy adults., Methods: Fourteen participants performed a randomized, cross-over, repeated measures design. After evaluation of maximal inspiratory pressures (MIP) and maximum voluntary contraction (MVC) for isometric neck flexion, participants were randomly assigned to submaximal ITL or INF until task failure. At least 2 days later, they performed the submaximal exercises in the opposite order. ITL or INF targeted 50 ± 5% of the MIP or MVC, respectively, until task failure. Near-infrared spectroscopy (NIRS) was applied to evaluate changes of deoxy-hemoglobin (ΔHHb), oxy-hemoglobin (ΔO 2 Hb), total hemoglobin (ΔtHb), and tissue saturation of oxygen (StO 2 ) of the sternocleidomastoid, scalenes, and Dia/IC. Breathlessness and perceived exertion were evaluated using Borg scales., Results: Initially during INF, sternocleidomastoid HHb slope was greatest compared to the scalenes and Dia/IC. At isotime (6.5-7 min), ΔtHb (a marker of blood volume) and ΔO 2 Hb of the sternocleidomastoid were higher during INF than ITL. Sternocleidomastoid HHb, O 2 Hb, and tHb during INF also increased at quartile and task failure timepoints. In contrast, scalene ΔO 2 Hb was higher during ITL than INF at isotime. Further, Dia/IC O 2 Hb and tHb increased during ITL at the third quartile and at task failure. Borg scores were lower at task failure during INF compared to ITL., Conclusion: Intermittent INF induces significant metabolic activity of the sternocleidomastoid and a lower perception of effort, which may provide an alternative inspiratory muscle training approach for mechanically ventilated patients., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Significance: Mechanical ventilation (MV) is a cornerstone technology in the intensive care unit as it assists with the delivery of oxygen in critically ill patients. The process of weaning patients from MV can be long and arduous and can lead to serious complications for many patients. Despite the known importance of inspiratory muscle function in the success of weaning, current clinical standards do not include direct monitoring of these muscles., Aim: The goal of this project was to develop and validate a combined frequency domain near-infrared spectroscopy (FD-NIRS) and diffuse correlation spectroscopy (DCS) system for the noninvasive characterization of inspiratory muscle response to a load., Approach: The system was fabricated by combining a custom digital FD-NIRS and DCS system. It was validated via liquid phantom titrations and a healthy volunteer study. The sternocleidomastoid (SCM), an accessory muscle of inspiration, was monitored during a short loading period in fourteen young, healthy volunteers. Volunteers performed two different respiratory exercises, a moderate load and a high load, which consisted of a one-minute baseline, a one-minute load, and a six-minute recovery period., Results: The system has low crosstalk between absorption, reduced scattering, and flow when tested in a set of liquid titrations. Faster dynamics were observed for changes in blood flow index ( BF i ), and metabolic rate of oxygen ( MRO 2 ) compared with hemoglobin + myoglobin (Hb+Mb) based parameters after the onset of loads in males. Additionally, larger percent changes in BF i , and MRO 2 were observed compared with Hb+Mb parameters in both males and females. There were also sex differences in baseline values of oxygenated Hb+Mb, total Hb+Mb, and tissue saturation., Conclusions: The dynamic characteristics of Hb+Mb concentration and blood flow were distinct during loading of the SCM, suggesting that the combination of FD-NIRS and DCS may provide a more complete picture of inspiratory muscle dynamics., (© 2024 The Authors.)

Background: Approximately 50% of patients with interstitial lung disease (ILD) experience frailty, which remains unexplored in acute exacerbations of ILD (AE-ILD). A better understanding may help with prognostication and resource planning. We evaluated the association of frailty with clinical characteristics, physical function, hospital outcomes, and post-AE-ILD recovery., Methods: Retrospective cohort study of AE-ILD patients (01/2015-10/2019) with frailty (proportion ≥0.25) on a 30-item cumulative-deficits index. Frail and non-frail patients were compared for pre- and post-hospitalization clinical characteristics, adjusted for age, sex, and ILD diagnosis. One-year mortality, considering transplantation as a competing risk, was analysed adjusting for age, frailty, and Charlson Comorbidity Index (CCI)., Results: 89 AE-ILD patients were admitted (median: 67 years, 63% idiopathic pulmonary fibrosis). 31 were frail, which was associated with older age, greater CCI, lower 6-min walk distance, and decreased independence pre-hospitalization. Frail patients had more major complications (32% vs 10%, p = .01) and required more multidisciplinary support during hospitalization. Frailty was not associated with 1-year mortality (HR: 0.97, 95%CI: [0.45-2.10]) factoring transplantation as a competing risk., Conclusions: Frailty was associated with reduced exercise capacity, increased comorbidities and hospital complications. Identifying frailty may highlight those requiring additional multidisciplinary support, but further study is needed to explore whether frailty is modifiable with AE-ILD., Competing Interests: Declaration of conflicting interestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Lee Fidler has received a grant from the Canadian Pulmonary Fibrosis Foundation and honoraria for speaking/lecturing from Boehringer Ingelheim, AstraZeneca, and Pfizer. Jolene Fisher acknowledges grants from Boehringer Ingelheim (for the Canadian Registry for Pulmonary Fibrosis) and payments made to the University of British Columbia, with subsequent support for the University of Toronto. She has received consulting fees and honoraria from AstraZeneca and Boehringer Ingelheim, as well as honoraria from Boehringer Ingelheim for a presentation. She serves as an unpaid Medical Advisory Board Member for the Canadian Pulmonary Fibrosis Foundation. W. Darlene Reid and Dmitry Rozenberg received a grant from the Canadian Institutes of Health Research for their project “Translating the interplay of cognition and physical performance to daily activities in COPD and ILD: Identifying Needs and Advancing Research Priorities. “Shane Shapera acknowledges a grant from Boehringer Ingelheim Canada and honoraria for speaking at CME events from AstraZeneca, Boehringer Ingelheim, and Hoffman La-Roche. All other authors have no conflicts of interest to declare.

Joint moment is the resultant force of limb movements. However, estimation methods for joint moments using surface electromyography frequently use joint angles instead of limb angles. The limb angle in joint moment estimation using electromyography could clarify the effects of muscle activity on the limbs: acceleration, deceleration, or stabilization. No study has quantified the comprehensive relationship between limb movement, muscle activity, and joint moment. This study aimed to determine the influencing factors for ankle-joint moment and knee-joint moment in the sagittal plane among muscle activities and parameters related to limb movements during half squat and gait. This study included 29 healthy adults (16 female participants, 21.1 ± 2.09 years). Using inertial measurement units, thigh, shank, and foot inclination angles and angular accelerations were calculated as the parameters of limb movements. Muscle activations of the biceps femoris long head, rectus femoris, gastrocnemius, and tibialis anterior were measured. Ankle joint moment and knee-joint moment were measured using a three-dimensional motion capture system and two force plates. Regression models showed high accuracy in measuring ankle-joint moment during a half squat and gait (R 2 f  = 0.92, 0.97, respectively) and knee-joint moment during a half squat (R 2 f  = 0.98), but not knee-joint moment during gait (R 2 f  = 0.63). However, only a maximum of five parameters were selected from muscle activities and limb angular information. Tibialis anterior and gastrocnemius activity were the largest contributors to ankle-joint moment during a half squat and gait, respectively, while muscle activities were not directly reflected in the knee-joint moment during either movement. Consideration of the interrelationships among limb movement, muscle activity, and joint moment is required when adjusting joint movements according to the target and aim of the therapeutic interventions., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Umi Matsumura reports writing assistance was provided by editage., (© 2023 The Authors.)

Background and Objective: Interstitial lung disease (ILD) encompasses several diverse pulmonary pathologies that result in abnormal diffuse parenchymal changes. When prescribing rehabilitation, several additional factors need to be considered as a result of aging, polypharmacy, and comorbidities manifested in ILD patients. This review aims to discuss issues related to frailty, skeletal muscle and cognitive function that limit physical activities in ILD patients. It will also highlight exercise training and propose complementary strategies for pulmonary rehabilitation., Methods: A literature search was performed in MEDLINE, CINAHL (inception to October 19th, 2022) using search terms based on concepts of: idiopathic pulmonary fibrosis or interstitial lung disease; frailty; muscular atrophy; skeletal muscle dysfunction; cognitive dysfunction; sleep quality; sleep disorders; anxiety disorders; or depressive disorders. After eligible texts were screened, additional references were included from references cited in the screened articles., Key Content and Findings: Frailty and skeletal muscle dysfunction are common in ILD. Weight loss, exhaustion, and anti-fibrotic medications can impact frailty, whereas physical inactivity, aging, corticosteroids and hypoxemia can contribute to sarcopenia (loss of muscle mass and function). Frailty is associated with worse clinical status, exercise intolerance, skeletal muscle dysfunction, and decreased quality of life in ILD. Sarcopenia appears to influence wellbeing and can potentially affect overall physical conditioning, cognitive function and the progression of ILD. Optimal assessment tools and effective strategies to prevent and counter frailty and sarcopenia need to be determined in ILD patients. Even though cognitive impairment is evident in ILD, its prevalence and underlying neurobiological model of contributing factors (i.e., inflammation, disease severity, cardiopulmonary status) requires further investigation. How ILD affects cognitive interference, motor control and consequently physical daily activities is not well defined. Strategies such as pulmonary rehabilitation, which primarily focuses on strength and aerobic conditioning have demonstrated improvements in ILD patient outcomes. Future incorporation of interval training and the integration of motor learning could improve transfer of rehabilitation strategies to daily activities., Conclusions: Numerous underlying etiologies of ILD contribute to frailty, skeletal muscle and cognitive function, but their respective neurobiologic mechanisms require further investigation. Exercise training increases physical measures, but complementary approaches may improve their applicability to improve daily activities., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-209/coif). The authors have no conflicts of interest to declare., (2023 Journal of Thoracic Disease. All rights reserved.)

Background: Chronic obstructive pulmonary disease (COPD) is a progressive condition associated with physical and cognitive impairments contributing to difficulty in performing activities of daily living (ADLs) that require dual tasking (eg, walking and talking). Despite evidence showing that cognitive decline occurs among patients with COPD and may contribute to functional limitations and decreased health-related quality of life (HRQL), pulmonary rehabilitation continues to focus mainly on physical training (ie, aerobic and strength exercises). An integrated cognitive and physical training program compared to physical training alone may be more effective in increasing dual-tasking ability among people living with COPD, leading to greater improvements in performance of ADLs and HRQL., Objective: The aims of this study are to evaluate the feasibility of an 8-week randomized controlled trial of home-based, cognitive-physical training versus physical training for patients with moderate to severe COPD and derive preliminary estimates of cognitive-physical training intervention efficacy on measures of physical and cognitive function, dual task performance, ADLs, and HRQL., Methods: A total of 24 participants with moderate to severe COPD will be recruited and randomized into cognitive-physical training or physical training. All participants will be prescribed an individualized home physical exercise program comprising 5 days of moderate-intensity aerobic exercise (30-50 minutes/session) and 2 days of whole-body strength training per week. The cognitive-physical training group will also perform cognitive training for approximately 60 minutes, 5 days per week via the BrainHQ platform (Posit Science Corporation). Participants will meet once weekly with an exercise professional (via videoconference) who will provide support by reviewing the progression of their training and addressing any queries. Feasibility will be assessed through the recruitment rate, program adherence, satisfaction, attrition, and safety. The intervention efficacy regarding dual task performance, physical function, ADLs, and HRQL will be evaluated at baseline and at 4 and 8 weeks. Descriptive statistics will be used to summarize intervention feasibility. Paired 2-tailed t tests and 2-tailed t tests will be used to compare the changes in the outcome measures over the 8-week study period within and between the 2 randomized groups, respectively., Results: Enrollment started in January 2022. It is estimated that the enrollment period will be 24 months long, with data collection to be completed by December 2023., Conclusions: A supervised home-based cognitive-physical training program may be an accessible intervention to improve dual-tasking ability in people living with COPD. Evaluating the feasibility and effect estimates is a critical first step to inform future clinical trials evaluating this approach and its effects on physical and cognitive function, ADL performance, and HRQL., Trial Registration: ClinicalTrials.gov NCT05140226; https://clinicaltrials.gov/ct2/show/NCT05140226., International Registered Report Identifier (irrid): DERR1-10.2196/48666., (©Dmitry Rozenberg, Josh Shore, Encarna Camacho Perez, Sahar Nourouzpour, Megha Ibrahim Masthan, Daniel Santa Mina, Jennifer L Campos, Ella Huszti, Robin Green, Mohammad Hashim Khan, Ambrose Lau, David Gold, Matthew B Stanbrook, W Darlene Reid. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 12.07.2023.)

Objectives: Dyspnea is a common and multidimensional experience of healthy adults and those with respiratory disorders. Due to its neural processing, it may limit or interfere with cognition, which may be examined with a dual-task paradigm. The aim of this study was to compare single-task performance of Stroop Colour and Word Test (SCWT) or inspiratory threshold loading (ITL) to their combined dual-task performance. Secondly, whether mood was related to dyspnea or cognitive performance was also evaluated., Materials & Methods: A virtual pre-post design examined single (SCWT and ITL) and dual-task (SCWT+ITL) performance. For ITL, a Threshold Trainer™ was used to elicit a "somewhat severe" rating of dyspnea. The SCWT required participants to indicate whether a colour-word was congruent or incongruent with its semantic meaning. The Depression, Anxiety and Stress Scale-21 (DASS-21) was completed to assess mood. Breathing frequency, Borg dyspnea rating, and breathing endurance time were ascertained., Results: Thirty young healthy adults (15F, 15M; median age = 24, IQR [23-26] years) completed the study. SCWT+ITL had lower SCWT accuracy compared to SCWT alone (98.6%, [97.1-100.0] vs 99.5%, [98.6-100.0]; p = 0.009). Endurance time was not different between ITL and SCWT+ITL (14.5 minutes, [6.9-15.0]) vs 13.7 minutes, [6.1-15.0]; p = 0.59). DASS-21 scores positively correlated with dyspnea scores during ITL (rho = 0.583, p<0.001) and SCWT+ITL (rho = 0.592, p<0.001)., Conclusions: ITL significantly reduced dual-task performance in healthy young adults. Lower mood was associated with greater perceived dyspnea during single and dual-task ITL. Considering the prevalence of dyspnea in respiratory disorders, the findings of this dual task paradigm warrant further exploration to inform dyspnea management during daily activities., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Chauvin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Dyspnea is a prevalent symptom in individuals with hypermobile Ehlers-Danlos Syndrome (hEDS) and generalized hypermobility spectrum disorder (G-HSD), yet its contributors have not been identified. One known contributor to dyspnea is respiratory muscle weakness. The feasibility and effectiveness of inspiratory muscle training (IMT) in combination with standard-of-care rehabilitation (aerobic, resistance, neuromuscular stabilization, and balance and proprioception exercises) in improving respiratory muscle strength and patient-reported outcomes in patients with hEDS or G-HSD have not been evaluated., Objective: This study aims to evaluate dyspnea, respiratory muscle strength, and patient-reported outcome measures (PROMs) in hEDS or G-HSD compared with healthy controls and to assess the feasibility of a randomized controlled trial of IMT and standard-of-care rehabilitation for improving respiratory muscle strength, exercise capacity, and PROMs compared with standard-of-care rehabilitation in hEDS and G-HSD., Methods: The study will include 34 participants with hEDS or G-HSD and 17 healthy, age- and sex-matched controls to compare respiratory muscle structure and function and PROMs. After baseline assessments, participants with hEDS or G-HSD will be randomized into the intervention group and provided IMT combined with Ehlers-Danlos Syndrome standard-of-care rehabilitation or into the usual care group, and provided only standard-of-care rehabilitation for 8 weeks. The intervention group will be prescribed IMT in their home environment using the POWERbreathe K5 IMT device (POWERbreathe International Ltd). IMT will comprise 2 daily sessions of 30 breaths for 5 days per week, with IMT progressing from 20% to 60% of the baseline maximal inspiratory pressure (MIP) over an 8-week period. Feasibility will be assessed through rates of recruitment, attrition, adherence, adverse events, and participant satisfaction. The primary pilot outcome is MIP change over an 8-week period in hEDS or G-HSD. Secondary outcomes will include the evaluation of dyspnea using Medical Research Council Scale and 18-point qualitative dyspnea descriptors; diaphragmatic thickening fraction using ultrasound; respiratory muscle endurance; pulmonary function; prefrontal cortical activity using functional near-infrared spectroscopy; aerobic capacity during cardiopulmonary exercise testing; quality of life using Short Form-36; and scores from the Depression, Anxiety, and Stress scale-21. These measures will also be performed once in healthy controls to compare normative values. Multivariable regression will be used to assess the contributors to dyspnea. Paired 2-tailed t tests will be used to assess the changes in MIP and secondary measures after 8 weeks of IMT., Results: Study recruitment began in August 2021 and, with several disruptions owing to COVID-19, is expected to be completed by December 2023., Conclusions: This study will provide a better understanding of the factors associated with dyspnea and the feasibility and effectiveness of IMT combined with standard-of-care rehabilitation. IMT may be a novel therapeutic strategy for improving respiratory muscle function and patient-reported outcomes in individuals with hEDS or G-HSD., Trial Registration: ClinicalTrials.gov NCT04972565; https://clinicaltrials.gov/ct2/show/NCT04972565., International Registered Report Identifier (irrid): DERR1-10.2196/44832., (©Dmitry Rozenberg, Noor Al Kaabi, Encarna Camacho Perez, Sahar Nourouzpour, Laura Lopez-Hernandez, Laura McGillis, Ewan Goligher, W Darlene Reid, Chung-Wai Chow, Clodagh M Ryan, Dinesh Kumbhare, Ella Huszti, Kateri Champagne, Satish Raj, Susanna Mak, Daniel Santa Mina, Hance Clarke, Nimish Mittal. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 20.03.2023.)

Background: Lung transplant (LTx) candidates experience significant respiratory symptoms often necessitating palliative care (PC) support. We aimed to describe symptoms experienced by interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD) LTx candidates referred for PC using the Edmonton Symptom Assessment System (ESAS) and to assess the change in ESAS in relation to pre-LTx exercise capacity, oxygen requirements, and respiratory exacerbations. Understanding symptom trajectory of these two patient groups will help inform PC management., Methods: Single centre, retrospective cohort of 102 ILD and 24 COPD LTx candidates who were assessed in the Toronto Transplant PC Clinic (TPCC) from 2014-2017. Chi-square and t-tests were used to compare clinical characteristics, physiological parameters, and ESAS scores., Results: The most common symptom in ILD and COPD patients was dyspnea (median score of 8, cough 7, fatigue 6). ILD patients reported higher cough scores (7 vs. 4, P<0.001). There was no association between the change in ESAS domains and six-minute walk distance (6MWD), oxygen requirements, or respiratory exacerbations, despite increased oxygen requirements and a greater decline in 6MWD in ILD compared to COPD pre-LTx (-47 vs. -8 meters, P=0.01). ILD candidates who were delisted/died compared to those transplanted, experienced worse depression (median ESAS; 4.5 vs. 1), anxiety (5.5 vs. 2) and dyspnea (9.5 vs. 8); P<0.05., Conclusions: ILD patients had similar symptoms as COPD patients, despite increased oxygen requirements and decreasing 6MWD pre-LTx. This study highlights the importance of symptom management of LTx candidates co-managed with PC, independent of traditional measures of disease severity.

Purpose: This study aimed to estimate the intra- and inter-rater reliability of the JTECH computerized, wireless apparatus and its validity (compared to established devices) for measurements of maximal shoulder isometric strength and handgrip strength among healthy adults with no shoulder pathology. Methods: Twenty healthy young adults had shoulder strength tested with JTECH and Micro-FET2 hand-held dynamometers, and the handgrip strength was tested using JTECH and Jamar handgrip dynamometers. Assessments were performed by the same rater to determine intra-rater reliability and convergent validity, at least two days apart, while on a third visit, the other rater performed measures to determine inter-rater reliability. Results: The JTECH computerized, wireless devices demonstrated good to excellent intra-rater reliability (ICCs (2,1) = 0.78-0.97) and inter-rater reliability for strength measures (ICCs (2,1) = 0.76-0.95). The JTECH computerized device compared to the Micro-FET2 hand-held dynamometer showed substantial concurrent validity for shoulder flexion ( R 2  = 0.87), extension ( R 2  = 0.87), abduction ( R 2  = 0.88), and adduction ( R 2  = 0.85). Substantial concurrent validity was shown for the JTECH computerized device and Jamar handgrip dynamometers ( R 2  = 0.92). Conclusions: The JTECH computerized, wireless devices demonstrated high intra- and inter-rater reliability and substantial concurrent validity for shoulder isometric strength and handgrip strength in healthy adults., (© Canadian Physiotherapy Association.)

Respiratory muscle training (RMT) improves physical performance, although it is still debated whether this effect depends on the type of training. The purpose of this study was to compare the effects of two different types of RMT, i.e., voluntary isocapnic hyperpnea (VIH) and inspiratory threshold loading (ITL), on the deoxygenation of intercostal (ΔSmO 2 - m. intercostales ) and vastus lateralis (ΔSmO 2 - m. vastus lateralis ) muscles during exercise. Twenty-four participants performed eight weeks of RMT by: (i) VIH (3 days·week -1 for 12 min at 60% maximal voluntary ventilation) or (ii) ITL (5 sets·week -1 of 30 breaths·minute -1 at 60% maximal inspiratory pressure). Cardiopulmonary exercise testing (CPET) included ΔSmO 2 (the change from baseline to end of test) of intercostal and vastus lateralis muscles. After RMT, both groups showed decreased ΔSmO 2 - m. intercostales (VIH = 12.8 ± 14.6%, p = 0.04 (effect size, ES = 0.59), and ITL = 8.4 ± 9.8%, p = 0.04 (ES = 0.48)), without a coincident change of ∆SmO 2- m. vastus lateralis . ITL training induced higher V˙O 2-peak absolute values than VIH (mean Δ post-pre, ITL = 229 ± 254 mL·min -1 [95% CI 67-391] vs. VIH, 39 ± 153 mL·min -1 [95% CI -58-136.0], p = 0.01). In conclusion, both RMT improved the balance between supply and oxygen consumption levels of m. intercostales during CPET, with ITL also inducing an increase of aerobic capacity.

Background and Objective: Reference values of physical activity to interpret longitudinal changes are not available in patients with idiopathic pulmonary fibrosis (IPF). This study aimed to define the minimal clinical important difference (MCID) of longitudinal changes in physical activity in patients with IPF., Methods: Using accelerometry, physical activity (steps per day) was measured and compared at baseline and 6-months follow-up in patients with IPF. We calculated MCID of daily step count using multiple anchor-based and distribution-based methods. Forced vital capacity and 6-minute walk distance were applied as anchors in anchor-based methods. Effect size and standard error of measurement were used to calculate MCID in distribution-based methods., Results: One-hundred and five patients were enrolled in the study (mean age: 68.5 ± 7.5 years). Step count significantly decreased from baseline to 6-months follow-up (-461 ± 2402, p = .031). MCID calculated by anchor-based and distribution-based methods ranged from 570-1358 steps., Conclusion: Daily step count significantly declined over 6-months in patients with IPF. MCID calculated by multiple anchor-based and distribution-based methods was 570 to 1358 steps/day. These findings contribute to interpretation of the longitudinal changes of physical activity that will assist its use as a clinical and research outcome in patients with IPF., Competing Interests: Declaration Of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Yasuhiro Kondoh reports advisory board fees and personal fees from Asahi Kasei Pharma Corp., Shionogi & Co.Ltd., and Boehringer Ingelheim Co., Ltd., advisory board fees from Janssen Pharmaceutical K.K., Healios K.K., Chugai Pharmaceutical Co., Ltd., and Taiho Pharmaceutical Co., Ltd., and personal fees from AstraZeneca K.K., Eisai inc., KYORIN Pharmaceutical Co., Ltd., Mitsubishi Tanabe Pharma, and Novartis Pharma K.K., outside the presentation work. Kensuke Kataoka and Yasuhiko Yamano received lecture fees from Nippon Boehringer, Ingelheim Co., Ltd., outside the submitted work. All other authors declared no conflict of interest.

Background: Chronic obstructive pulmonary disease (COPD) is often accompanied by impaired cognitive and physical function. However, the role of cognitive function on motor control and purposeful movement is not well studied. The aim of the review was to determine the impact of cognition on physical performance in COPD. Methods: Scoping review methods were performed including searches of the databases: MEDLINE, EMBASE, Cochrane Systematic Reviews, Cochrane (CENTRAL), APA PsycINFO, and CINAHL. Two reviewers independently assessed articles for inclusion, data abstraction, and quality assessment. Results: Of 11,252 identified articles, 44 met the inclusion criteria. The review included 5743 individuals with COPD (68% male) with the forced expiratory volume in one second range of 24-69% predicted. Cognitive scores correlated with strength, balance, and hand dexterity, while 6-min walk distance ( n = 9) was usually similar among COPD patients with and without cognitive impairment. In 2 reports, regression analyses showed that delayed recall and the trail making test were associated with balance and handgrip strength, respectively. Dual task studies ( n = 5) reported impaired balance or gait in COPD patients compared to healthy adults. Cognitive or physical Interventions ( n = 20) showed variable improvements in cognition and exercise capacity. Conclusions: Cognition in COPD appears to be more related to balance, hand, and dual task function, than exercise capacity.

Background: Individuals with lung disease commonly use the internet as a source of health information on pulmonary rehabilitation (PR). The objective of this study was to characterize internet resources on PR, and to assess the content, readability, and quality of patient-directed PR resources., Methods: The first 200 websites for the search term 'pulmonary rehabilitation resources and exercise' were analyzed on Google, Yahoo, and Bing. Website content was assessed based on 30 key components of PR from the 2013 and 2021 international consensus statements. Website quality was determined using DISCERN, JAMA benchmarks, and Global Quality Scale (GQS)., Results: 66 unique PR websites were identified with the two most common categories being scientific resources (39%) and foundation/advocacy organizations (33%). The average reading level of websites was 11 ± 3. PR content varied significantly across websites (mean range 13.4-21.5). Median DISCERN total score and GQS score were 4 (IQR 3-4) and 3.5 (IQR 2-4), respectively, representing moderate-good quality. Foundation/advocacy websites had higher DISCERN and GQS scores compared to other websites., Conclusion: Foundation/advocacy websites had the highest quality and reliability metrics; however, the higher-than-recommended reading levels may compromise patient comprehension and utilization. This study provides critical insight on the current state of online PR health-related information.

The purpose of this narrative review is to highlight the oxidative stress induced in COVID-19 patients (SARS-CoV-2 infection), describe longstanding functional impairments, and provide the pathophysiologic rationale that supports aerobic eccentric (ECC) exercise as a novel alternative to conventional concentric (CONC) exercise for post-COVID-19 patients. Patients who recovered from moderate-to-severe COVID-19 respiratory distress demonstrate long-term functional impairment. During the acute phase, SARS-CoV-2 induces the generation of reactive oxygen species that can be amplified to a "cytokine storm". The resultant inflammatory and oxidative stress process causes organ damage, particularly in the respiratory system, with the lungs as the tissues most susceptible to injury. The acute illness often requires a long-term hospital stay and consequent sarcopenia. Upon discharge, muscle weakness compounded by limited lung and cardiac function is often accompanied by dyspnea, myalgia, anxiety, depression, and sleep disturbance. Consequently, these patients could benefit from pulmonary rehabilitation (PR), with exercise as a critical intervention (including sessions of strength and endurance or aerobic exercises). Unfortunately, conventional CONC exercises induce significant cardiopulmonary stress and increase inflammatory and oxidative stress (OS) when performed at moderate/high intensity, which can exacerbate debilitating dyspnoea and muscle fatigue post-COVID-19. Eccentric training (ECC) is a well-tolerated alternative that improves muscle mass while mitigating cardiopulmonary stress in patients with COPD and other chronic diseases. Similar benefits could be realized in post-COVID-19 patients. Consequently, these patients could benefit from PR with exercise as a critical intervention.

Background: Insufficient or excessive respiratory effort during acute hypoxemic respiratory failure (AHRF) increases the risk of lung and diaphragm injury. We sought to establish whether respiratory effort can be optimized to achieve lung- and diaphragm-protective (LDP) targets (esophageal pressure swing - 3 to - 8 cm H 2 O; dynamic transpulmonary driving pressure ≤ 15 cm H 2 O) during AHRF., Methods: In patients with early AHRF, spontaneous breathing was initiated as soon as passive ventilation was not deemed mandatory. Inspiratory pressure, sedation, positive end-expiratory pressure (PEEP), and sweep gas flow (in patients receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO)) were systematically titrated to achieve LDP targets. Additionally, partial neuromuscular blockade (pNMBA) was administered in patients with refractory excessive respiratory effort., Results: Of 30 patients enrolled, most had severe AHRF; 16 required VV-ECMO. Respiratory effort was absent in all at enrolment. After initiating spontaneous breathing, most exhibited high respiratory effort and only 6/30 met LDP targets. After titrating ventilation, sedation, and sweep gas flow, LDP targets were achieved in 20/30. LDP targets were more likely to be achieved in patients on VV-ECMO (median OR 10, 95% CrI 2, 81) and at the PEEP level associated with improved dynamic compliance (median OR 33, 95% CrI 5, 898). Administration of pNMBA to patients with refractory excessive effort was well-tolerated and effectively achieved LDP targets., Conclusion: Respiratory effort is frequently absent  under deep sedation but becomes excessive when spontaneous breathing is permitted in patients with moderate or severe AHRF. Systematically titrating ventilation and sedation can optimize respiratory effort for lung and diaphragm protection in most patients. VV-ECMO can greatly facilitate the delivery of a LDP strategy., Trial Registration: This trial was registered in Clinicaltrials.gov in August 2018 (NCT03612583)., (© 2022. The Author(s).)

The physical impairments (e.g., slower walking speed) in patients with chronic obstructive pulmonary disease (COPD) have been attributed to peripheral characteristics (e.g., muscle atrophy). However, cognitive impairment may compromise motor control including walking automaticity. The objective of this study was to investigate PFC neural activity, evaluated using changes in oxygenated hemoglobin (ΔO 2 Hb), during preferred paced walking (PPW) in COPD patients and age-matched controls. The ΔO 2 Hb from the left and right dorsolateral PFC was measured using functional near-infrared spectroscopy. Fifteen COPD patients (age: 71 ± 8) and twenty age-matched controls (69 ± 7 years) participated. Two-way mixed ANOVA demonstrated that O 2 Hb in both groups decreased during PPW from the start (quintile 1; Q1) to the end (quintile 5; Q5) in the left dorsolateral and medial PFC. Q1 was comprised of the data during the first 20% of the task, while Q5 included data collected in the last 20% of the task duration. PPW duration ranged between 30.0 and 61.4 s in the control group and between 28.6 and 73.0 s in COPD patients. COPD patients demonstrated a higher O 2 Hb in Q5 compared to the negative O 2 Hb in controls in the right medial and dorsolateral PFC during PPW. PPW velocity was lower in COPD patients compared to controls (1.02 ± 0.22 vs. 1.22 ± 0.14 m/s, p = 0.005). Healthy older controls exhibited automaticity during walking unlike patients with COPD. The lesser decrease in O 2 Hb in COPD patients may be attributed to increased executive demands or affect-related cues (e.g., pain or dyspnea) during walking.

Purpose: To contrast older and younger adults' prefrontal cortex (PFC) neural activity (through changes in oxygenated hemoglobin) during single and dual tasks, and to compare decrements in task performance., Methods: Changes in oxygenated hemoglobin of dorsolateral PFC were monitored using functional near-infrared spectroscopy during single tasks of spelling backwards (cognitive task) and 30 m preferred paced walk; and a dual task combining both. Gait velocity was measured by a pressure sensitive mat., Results: Twenty sex-matched younger (27.6 ± 3.5 years) and 17 older adults (71.2 ± 4.9 years) were recruited. The left PFC oxygenated hemoglobin decreased from start (1st quintile) to the end (5th quintile) of the walking task in younger adults ( - 0.03 ± 0.03 to - 0.72 ± 0.20 µM; p < .05) unlike the non-significant change in older adults (0.03 ± 0.06 to  -  0.41 ± 0.32 µM, p > .05). Overall, oxygenation increased bilaterally during dual versus single walk task in older adults (Left PFC: 0.22 ± 0.16 vs. - 0.23 ± 0.21 µM, respectively; Right PFC: 0.17 ± 0.18 vs. - 0.33 ± 0.22 µM, respectively), but only in right PFC in younger adults ( - 0.02 ± 0.15 vs.  -  0.47 ± 0.13 µM). Older adults exhibited lower velocity during the dual task compared to younger adults (1.03 ± 0.16 vs. 1.20 ± 0.17 m/s, respectively). Older age was associated with dual task cost on velocity during walking after adjusting for confounding variables., Conclusions: Age-related cognitive decline in older adults may increase neural activity for cognitive tasks and diminish walking automaticity that may lead to decrements during dual tasking; the greater PFC increases in the oxygenated hemoglobin and lower velocity may be due to increased cognitive load and limited attentional resources., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Rationale: Reverse triggering dyssynchrony (RT) is a patient-ventilator interaction where a respiratory muscle contraction is triggered by a passive mechanical insufflation. Its impact on diaphragm structure and function is unknown. Objectives: To establish an animal model of RT with lung injury receiving lung-protective ventilation and to assess its impact on the structure and function of the diaphragm. Methods: Lung injury was induced by surfactant depletion and high-stress ventilation in 32 ventilated pigs. Animals were allocated to receive passive mechanical ventilation (Vt: 10 ml/kg; respiratory rate [RR]: 30-35 breaths/min; n  = 8) or a more lung-protective strategy (Vt: 6-8 ml/kg; n  = 24) with adjustments in RR to facilitate the occurrence of RT for 3 hours. Diaphragm function (transdiaphragmatic pressure [Pdi] during phrenic nerve stimulation [force/frequency curve]) and structure (biopsies) were assessed. The impact of RT on diaphragm function was analyzed according to the breathing effort assessed by the pressure-time product. Measurements and Main Results: Compared with passive ventilation, the protective ventilation group with RT received significantly lower Vt (7 vs. 10 ml/kg) and higher RR (45 vs. 31 breaths/min). An entrainment pattern of 1:1 was the most frequently occurring in 83% of the animals. Breathing effort induced by RT was highly variable across animals. RT with the lowest tercile of breathing effort was associated with 23% higher twitch Pdi compared with passive ventilation, whereas RT with high breathing effort was associated with a 10% lower twitch Pdi and a higher proportion of abnormal muscle fibers. Conclusions: In a reproducible animal model of RT with variable levels of breathing effort and entrainment patterns, RT with high effort is associated with impaired diaphragm function, whereas RT with low effort is associated with preserved diaphragm force.