Influence of inspiratory resistive loading on expiratory muscle fatigue in healthy humans

Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel co-activation of the inspiratory muscles during expiration. It is unknown whether the expiratorymuscles are similarly co-activated to the point of fatigue during inspiratory resistive loading (IRL).The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n=9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths∙min-1, 0.7 inspiratory duty cycle) to task failure. Abdominal and diaphragm contractile function was assessed at baseline and at 3, 15 and 30 min post-IRL by measuring gastric twitch pressure (Pga,tw) and transdiaphragmatic twitch pressure (Pdi,tw) in response to potentiated magnetic stimulation of the thoracic and phrenic nerves, respectively. Fatigue was defined as a significant reduction from baseline in Pga,tw or Pdi,tw. Throughout IRL, there was a time-dependent increase in cardiac frequency and mean arterial blood pressure, suggesting activation of the respiratory muscle metaboreflex. Pdi,tw was significantly lower than baseline (34.3 9.6 cmH2O) at 3min (23.2 5.7 cmH2O, P<0.001), 15 min (24.2 5.1 cmH2O, P<0.001) and 30 min post-IRL (26.3 6.0 cmH2O, P<0.001). Pga,tw was not significantly different from baseline (37.6 17.1 cmH2O) at 3min (36.5 14.6 cmH2O), 15 min (33.7 12.4 cmH2O) and 30 min post-IRL (32.9 11.3 cmH2O). IRL elicits objective evidence of diaphragm, but not abdominal, muscle fatigue. Agonist-antagonist interactions for the respiratory muscles appear to be more important during expiratory versus inspiratory loading.The Natural Sciences and Engineering Research Council (NSERC) of Canada supported this study. C.M. Peters, P.B. Dominelli, and Y. Molgat-Seon were supported by NSERC postgraduate scholarships. J.F Welch was supported by a University of British Columbia graduate fellowship

Effects of Age and Sex on Inspiratory Muscle Activation Patterns During Exercise

Purpose: Characterize the effects of age, sex, and their interaction on inspiratory muscle activation patterns during exercise. Methods: Twenty younger (20-30y, n=10 women) and twenty older (60-80y, n=10 women) subjects performed an incremental cycle exercise test. Electromyography of the scalene (EMGsca) and sternocleidomastoid (EMGscm) muscles were measured using skin surface electrodes, while diaphragm electromyography (EMGdi) and esophageal and transdiaphragmatic pressures were measured using an esophageal catheter. Electromyography data were transformed into root-mean-square with a 100ms time constant. Esophageal (PTPes) and diaphragmatic (PTPdi) pressure-time products were used as indices of total inspiratory muscle pressure production and diaphragmatic pressure production, respectively. Results: At absolute minute ventilations (V E), women and older subjects had greater EMGdi than men and younger subjects, respectively (all p<0.05), but no differences were noted when V E was expressed in relative terms (all p>0.05). Women had greater EMGsca activity than men at absolute and relative levels of V E (all p<0.05). Older subjects had greater EMGsca than younger subjects when V E was expressed relative (all p<0.05) but not absolute terms (all p>0.05). At absolute and relative levels of V E, women and older subjects had greater EMGscm than men and younger subjects, respectively (all p<0.05). Women and older subjects had a greater PTPdi/PTPes at a V E of 70 l·min-1 than men and younger subjects, respectively (both p<0.05), but no differences were noted when V E was expressed in relative terms (all p>0.05). No significant interactions between age and sex were noted (all p>0.05). Conclusion: Age and sex significantly affect inspiratory muscle activation patterns during exercise; however, the extent of the effects depends on whether comparisons are made at a solute or relative V E.This study was supported by the British Columbia Lung Association (BCLA). YMS, PBD, and AHR were supported by graduate scholarships from the Natural Sciences and Engineering Research Council of Canada (NSERC). PBD and MRS were supported by fellowships from the University of British Columbia and BCLA. JAG was supported by a Scholar Award from the Michael Smith Foundation for Health Research, a New Investigator Award from the Providence Health Care Research Institute and St. Paul’s Hospital Foundation, and a Canadian Institutes of Health Research Clinical Rehabilitation New Investigator Award

Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women

© 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society. KEY POINT SUMMARY:The perceived intensity of exertional breathlessness (i.e. dyspnoea) is higher in older women than in older men, possibly due to sex-difference respiratory system morphology. During exercise at a given absolute intensity or minute ventilation, older women have a greater degree of mechanical ventilatory constraint (i.e. work of breathing and expiratory flow limitation) than their male counterparts, which may lead to a greater perceived intensity of dyspnoea. Using a single-blind randomized study design, we experimentally manipulated the magnitude of mechanical ventilatory constraint during moderate-intensity exercise at ventilatory threshold in healthy older men and women. We found that changes in the magnitude of mechanical ventilatory constraint within the physiological range had no effect on dyspnoea in healthy older adults. When older men and women perform submaximal exercise at a moderate intensity, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea. We sought to determine the effect of manipulating mechanical ventilatory constraint during submaximal exercise on dyspnoea in older men and women. METHODS:Eighteen healthy subjects (60-80 y; 9 men, 9 women) completed two days of testing. On Day 1, subjects performed pulmonary function testing and a maximal incremental cycle exercise test. On Day 2, subjects performed three 6-min bouts of cycling at ventilatory threshold, in a single-blind randomized manner, while breathing: i) normoxic helium-oxygen (HEL) to reduce the work of breathing (Wb ) and alleviate expiratory flow limitation (EFL); ii) through an inspiratory resistance (RES) of ∼5 cmH2 O·l-1 ·s-1 to increase Wb ; and iii) ambient air as a control (CON). Oesophageal pressure, diaphragm electromyography, and sensory responses (using the category-ratio 10 Borg scale) were monitored throughout exercise. RESULTS:During the HEL condition, there was a significant decrease in Wb (men: -21 ± 6%, women: -17 ± 10%) relative to CON (both p < 0.01). Moreover, if EFL was present during CON (4 men, 5 women), it was alleviated during HEL. Conversely, during the RES condition, Wb (men: 42 ± 19%, women: 50 ± 16%) significantly increased relative to CON (both p < 0.01). There was no main effect of sex on Wb (p = 0.59). Across conditions, women reported significantly higher dyspnoea intensity than men (2.9 ± 0.9 vs. 1.9 ± 0.8 Borg scale units, p < 0.05). Despite significant differences in the degree of mechanical ventilatory constraint between conditions, dyspnoea intensity was unaffected, independent of sex (p = 0.46). CONCLUSION:When older men and women perform submaximal exercise at a moderate intensity, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea. This article is protected by copyright. All rights reserved.Natural Science and Engineering Research Council of Canada (NSERC) British Columbia Lung Association (BCLA

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty

Coordination in climbing: effect of skill, practice and constraints manipulation

BACKGROUND: Climbing is a physical activity and sport involving many subdisciplines. Minimization of prolonged pauses, use of a relatively simple path through a route and smooth transitions between movements broadly define skilled coordination in climbing. OBJECTIVES: To provide an overview of the constraints on skilled coordination in climbing and to explore future directions in this emerging field. METHODS: A systematic literature review was conducted in 2014 and retrieved studies reporting perceptual and movement data during climbing tasks. To be eligible for the qualitative synthesis, studies were required to report perceptual or movement data during climbing tasks graded for difficulty. RESULTS: Qualitative synthesis of 42 studies was carried out, showing that skilled coordination in climbing is underpinned by superior perception of climbing opportunities; optimization of spatial-temporal features pertaining to body-to-wall coordination, the climb trajectory and hand-to-hold surface contact; and minimization of exploratory behaviour. Improvements in skilled coordination due to practice are related to task novelty and the difficulty of the climbing route relative to the individual's ability level. CONCLUSION: Perceptual and motor adaptations that improve skilled coordination are highly significant for improving the climbing ability level. Elite climbers exhibit advantages in detection and use of climbing opportunities when visually inspecting a route from the ground and when physically moving though a route. However, the need to provide clear guidelines on how to improve climbing skill arises from uncertainties regarding the impacts of different practice interventions on learning and transfer

Inspiration for the Future: The Role of Inspiratory Muscle Training in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited, multi-system, life-limiting disease characterized by a progressive decline in lung function, which accounts for the majority of CF-related morbidity and mortality. Inspiratory muscle training (IMT) has been proposed as a rehabilitative strategy to treat respiratory impairments associated with CF. However, despite evidence of therapeutic benefits in healthy and other clinical populations, the routine application of IMT in CF can neither be supported nor refuted due to the paucity of methodologically rigorous research. Specifically, the interpretation of available studies regarding the efficacy of IMT in CF is hampered by methodological threats to internal and external validity. As such, it is important to highlight the inherent risk of bias that differences in patient characteristics, IMT protocols, and outcome measurements present when synthesizing this literature prior to making final clinical judgments. Future studies are required to identify the characteristics of individuals who may respond to IMT and determine whether the controlled application of IMT can elicit meaningful improvements in physiological and patient-centered clinical outcomes. Given the equivocal evidence regarding its efficacy, IMT should be utilized on a case-by-case basis with sound clinical reasoning, rather than simply dismissed, until a rigorous evidence-based consensus has been reached

Population‐based cohort study of outcomes following cholecystectomy for benign gallbladder diseases

Background The aim was to describe the management of benign gallbladder disease and identify characteristics associated with all‐cause 30‐day readmissions and complications in a prospective population‐based cohort. Methods Data were collected on consecutive patients undergoing cholecystectomy in acute UK and Irish hospitals between 1 March and 1 May 2014. Potential explanatory variables influencing all‐cause 30‐day readmissions and complications were analysed by means of multilevel, multivariable logistic regression modelling using a two‐level hierarchical structure with patients (level 1) nested within hospitals (level 2). Results Data were collected on 8909 patients undergoing cholecystectomy from 167 hospitals. Some 1451 cholecystectomies (16·3 per cent) were performed as an emergency, 4165 (46·8 per cent) as elective operations, and 3293 patients (37·0 per cent) had had at least one previous emergency admission, but had surgery on a delayed basis. The readmission and complication rates at 30 days were 7·1 per cent (633 of 8909) and 10·8 per cent (962 of 8909) respectively. Both readmissions and complications were independently associated with increasing ASA fitness grade, duration of surgery, and increasing numbers of emergency admissions with gallbladder disease before cholecystectomy. No identifiable hospital characteristics were linked to readmissions and complications. Conclusion Readmissions and complications following cholecystectomy are common and associated with patient and disease characteristics