Influence of respiratory loading on left-ventricular function in cervical spinal cord injury.

Cervical spinal cord injury (C-SCI) negatively impacts cardiac and respiratory function. As the heart and lungs are linked via the pulmonary circuit these systems are interdependent. Here, we utilized inspiratory and expiratory loading to assess whether augmenting the respiratory pump improves left-ventricular (LV) filling and output in individuals with motor-complete C-SCI. We hypothesized LV end-diastolic volume (LVEDV) would increase and decrease with inspiratory and expiratory loading, respectively. Participants (C-SCI: 7M/1F, 35 ± 7 years; able-bodied: 7M/1F, 32 ± 6 years) were assessed under five conditions during 45° head-up tilt; unloaded, inspiratory loading with -10 and -20 cmH2 O oesophageal pressure (Poes ) on inspiration, and expiratory loading with +10 and +20 cmH2 O Poes on expiration. An oesophageal balloon catheter monitored Poes , and LV structure and function were assessed by echocardiography. In C-SCI only, (1) +20 cmH2 O reduced LVEDV vs. unloaded (81 ± 15 vs. 88 ± 11 ml, P = 0.006); (2) heart rate was higher during +20 cmH2 O compared to unloaded (P = 0.001) and +10 cmH2 O (P = 0.002); (3) cardiac output was higher during +20 cmH2 O than unloaded (P = 0.002); and (4) end-expiratory lung volume was higher during +20 cmH2 O vs. unloaded (63 ± 10 vs. 55 ± 13% total lung capacity, P = 0.003) but was unaffected by inspiratory loading. In both groups, -10 and -20 cmH2 O had no significant effect on LVEDV. These findings suggest greater expiratory positive pressure acutely impairs LV filling in C-SCI, potentially via impaired venous return, mediastinal constraint and/or direct ventricular interaction subsequent to dynamic hyperinflation. Inspiratory loading did not significantly improve LV function in C-SCI and neither inspiratory nor expiratory loading affected cardiac function or lung volumes in able-bodied participants. KEY POINTS: Cervical spinal cord injury (C-SCI) alters both the cardiac and the respiratory system, but little is known about how these systems interact following injury. Here, we manipulated inspiratory or expiratory intrathoracic pressure (ITP) to mechanistically test the role of the respiratory pump in circulatory function in highly trained individuals with C-SCI and an able-bodied reference group. In individuals with C-SCI, greater ITP during expiratory loading caused dynamic hyperinflation that was associated with impaired left-ventricular filling. More negative ITP during inspiratory loading did not significantly alter left-ventricular volumes in either group. Interventions that prevent dynamic hyperinflation and/or enhance the ability to generate expiratory pressures may help preserve left-ventricular filling in individuals with C-SCI.

GrOup based physical Activity for oLder adults (GOAL) randomized controlled trial: study protocol.

BACKGROUND: Physical activity has health benefits across the lifespan, yet only 13 % of Canadian older adults are sufficiently active. Results from a number of observational studies indicate that adults display positive preferences for exercising with others of a similar age and same gender, and that intra-group age- and gender-similarity are associated with elevated exercise adherence. However, research has yet to experimentally examine the extent to which intra-group age- and gender-related similarity affect exercise adherence behaviors. METHODS/DESIGN: The GrOup-based physical Activity for oLder adults (GOAL) trial is a three-arm randomized control trial that will examine the efficacy of two different group-based exercise programs for older adults (informed by the tenets of self-categorization theory) in relation to a standard group-based exercise program. Within this manuscript we outline the design and proposed evaluation of the GOAL trial. The first arm is comprised of exercise groups made up of participants of a similar-age and of the same gender; the second arm consists of groups with similar-aged mixed gender participants; the control arm is comprised of mixed-aged mixed gender participants. We aim to compare the adherence rates of participants across conditions, as well as potential moderation effects and mediating mechanisms. DISCUSSION: Results from this trial will inform intervention designs to improve the exercise adherence behaviors of older adult. At a systems-level, should support be derived for the efficacy of the interventions tested in this trial, changing group composition (i.e., age, gender) represents a feasible program adaptation for physical activity centers. TRIAL REGISTRATION: ClinicalTrials.gov # NCT02023632 . Registered December 13, 2013.

Testing the effects of an expectancy-based intervention among adolescents: Can placebos be used to enhance physical health?

It has been suggested that the well-known health benefits associated with exercise can be explained by a placebo effect, and that greater effort should be given to convince people that their current behaviors have desirable health consequences. The overall purpose of this study was to test the efficacy of this "mind-set matters" hypothesis through the use of an expectancy-based intervention with adolescents. The study involved a four week randomized controlled trial with 348 Grade 9 adolescents (M (age) = 14.07 yrs, SD = 0.30), from four high schools, taking part in either a placebo-intervention condition (n = 188) or a control condition (n = 160). Participants in the placebo-intervention condition were informed that what they are already doing in school physical education lessons fulfills current recommendations for an active lifestyle. Participants in the control condition were not given this information. Four weeks after the intervention, adolescents in the placebo-intervention condition did not demonstrate significant changes in physiological health-related measures (diet, weight, body mass index, percentage body fat, heart rate, mean arterial pressure). The findings question the external validity of the "mind-set matters" hypothesis with adolescents, and suggest that simply encouraging adolescents to believe that they are healthy may not enable them to respond with improved indicators of physical health.

Fiber optic endoscopic optical coherence tomography (OCT) to assess human airways: The relationship between anatomy and physiological function during dynamic exercise.

Airway luminal area (Ai ) influences respiratory mechanics during dynamic exercise; however, previous studies have investigated the relationship between airway anatomy and physiological function in different groups of individuals. The purpose of this study was to determine the effect of Ai on respiratory mechanics by making in vivo measures of airway dimensions and work of breathing (Wb) in the same individuals. Healthy participants (3F/2M; 23-45 years) completed a cycle exercise test to exhaustion. During exercise, Wb was assessed using an esophageal balloon catheter, while simultaneously assessing minute ventilation ( V˙E ). On a separate day, subjects underwent a bronchoscopy procedure to capture optical coherence tomography (OCT) measures of three airways in the right lung. Each participant's Wb- V˙E data were fit to a non-linear regression equation (Wb = a V˙E3  + b V˙E2 ) that partitions Wb into its turbulent resistive (a) and viscoelastic (b) components. Measures of Ai and luminal diameter were made for the 4th-6th airway generations. A composite index of airway size was calculated as the sum of the Ai for each generation and the total area of the 4th-6th generation was calculated based on Weibel's model. Constant a was significantly correlated to the Weibel model total airway area (r = -0.94, p = 0.017) and index of airway size (r = -0.929, p = 0.023), whereas constant b was not associated with either measure (both p > 0.05). We found that individuals who had the smallest Ai had the highest resistive Wb and our findings provide the basis for further study of the relationship between airway size and respiratory mechanics during exercise.

Myocardial Infarction Injury in Patients with Chronic Lung Disease Entering Pulmonary Rehabilitation: Frequency and Association with Heart Rate Parameters.

BACKGROUND: Myocardial infarction (MI) remains under-recognized in chronic lung disease (CLD) patients. Rehabilitation health professionals need accessible clinical measurements to identify the presence of prior MI in order to determine appropriate training prescription. OBJECTIVES: To estimate prior MI in CLD patients entering a pulmonary rehabilitation program, as well as its association with heart rate parameters such as resting heart rate and chronotropic response index. DESIGN: Retrospective cohort design. SETTING: Pulmonary rehabilitation outpatient clinic in a tertiary care university-affiliated hospital. PATIENTS: Eighty-five CLD patients were studied. METHODS: Electrocardiograms at rest and peak cardiopulmonary exercise testing, performed before pulmonary rehabilitation, were analyzed. Electrocardiographic evidence of prior MI, quantified by the Cardiac Infarction Injury Score (CIIS), was contrasted with reported myocardial events and then correlated with resting heart rate and chronotropic response index parameters. MAIN OUTCOME MEASUREMENTS: CIIS, resting heart rate, and chronotropic response index. RESULTS: Sixteen CLD patients (19%) demonstrated electrocardiographic evidence of prior MI, but less than half (8%) had a reported MI history (P < .05). The Cohen's kappa test revealed poor level of agreement between CIIS and medical records (kappa = 0.165), indicating that prior MI diagnosis was under-reported in the medical records. Simple and multiple regression analyses showed that resting heart rate but not chronotropic response index was positively associated with CIIS in our population (R2 = 0.29, P < .001). CLD patients with a resting heart rate higher than 80 beats/min had approximately 5 times higher odds of having prior MI, as evidenced by a CIIS ≥ 20. CONCLUSIONS: CLD patients entering pulmonary rehabilitation are at risk of unreported prior MI. Elevated resting heart rate appears to be an indicator of prior MI in CLD patients; therefore, careful adjustment of training intensity is recommended under these circumstances. LEVEL OF EVIDENCE: III.

Diaphragm Recruitment Increases during a Bout of Targeted Inspiratory Muscle Training.

PURPOSE: The extent to which the diaphragm is targeted during a bout of inspiratory muscle training (IMT) is unknown. The purpose of this study was to characterize the relative activation patterns of the diaphragm and extradiaphragmatic inspiratory muscles during a bout of IMT and to determine whether diaphragmatic recruitment can be increased by giving subjects specific diaphragmatic breathing instructions (IMTdi). METHODS: Ten healthy men were instrumented with surface EMG electrodes on the sternocleidomastoid (EMGscm), scalenes (EMGsca), parasternal intercostals (EMGpic), and seventh intercostal space (EMG7ic). A multipair esophageal electrode catheter measured crural diaphragmatic EMG (EMGdi) and transdiaphragmatic pressure (Pdi). Trial 1 of IMT involved 25 dynamic inspiratory maneuvers at 40% of maximal inspiratory mouth pressure using a variable flow resistive loading device where subjects were free to choose their own inspiratory muscle recruitment strategy. Trial 2 involved the same procedures, but subjects were given specific instructions to actively recruit their diaphragm. Cervical magnetic stimulation of the phrenic nerves verified the absence of diaphragmatic fatigue before commencing the second trial. RESULTS: Compared with IMT, IMTdi resulted in a significant increase in EMGdi (56 ± 12 vs 73 ± 10%max, P = 0.002) and Pdi swings (39 ± 14 vs 64 ± 17 cm H2O, P < 0.0001) and a decrease in EMGsca (52 ± 21 vs 36 ± 22%max, P = 0.04). There was no difference in EMG7ic (26 ± 19 vs 33 ± 21%max, P = 0.36), EMGpic (31 ± 24 vs 25 ± 15%max, P = 0.22), and EMGscm (58 ± 21 vs 45 ± 24%max, P = 0.08) when comparing IMT versus IMTdi, respectively. CONCLUSIONS: Simple diaphragmatic breathing instructions can significantly increase the recruitment of the diaphragm during IMT compared with a bout of IMT where individuals are free to choose their own inspiratory muscle recruitment strategy.

Administration of intrapulmonary sodium polyacrylate to induce lung injury for the development of a porcine model of early acute respiratory distress syndrome.

BACKGROUND: The loss of alveolar epithelial and endothelial integrity is a central component in acute respiratory distress syndrome (ARDS); however, experimental models investigating the mechanisms of epithelial injury are lacking. The purpose of the present study was to design and develop an experimental porcine model of ARDS by inducing lung injury with intrapulmonary administration of sodium polyacrylate (SPA). METHODS: The present study was performed at the Centre for Comparative Medicine, University of British Columbia, Vancouver, British Columbia. Human alveolar epithelial cells were cultured with several different concentrations of SPA; a bioluminescence technique was used to assess cell death associated with each concentration. In the anesthetized pig model (female Yorkshire X pigs (n = 14)), lung injury was caused in 11 animals (SPA group) by injecting sequential aliquots (5 mL) of 1% SPA gel in aqueous solution into the distal airway via a rubber catheter through an endotracheal tube. The SPA was dispersed throughout the lungs by manual bag ventilation. Three control animals (CON group) underwent all experimental procedures and measurements with the exception of SPA administration. RESULTS: The mean (± SD) ATP concentration after incubation of human alveolar epithelial cells with 0.1% SPA (0.92 ± 0.27 µM/well) was approximately 15% of the value found for the background control (6.30 ± 0.37 µM/well; p < 0.001). Elastance of the respiratory system (E RS) and the lung (E L) increased in SPA-treated animals after injury (p = 0.003 and p < 0.001, respectively). Chest wall elastance (E CW) did not change in SPA-treated animals. There were no differences in E RS, E L, or E CW in the CON group when pre- and post-injury values were compared. Analysis of bronchoalveolar lavage fluid showed a significant shift toward neutrophil predominance from before to after injury in SPA-treated animals (p < 0.001) but not in the CON group (p = 0.38). Necropsy revealed marked consolidation and congestion of the dorsal lung lobes in SPA-treated animals, with light-microscopy evidence of bronchiolar and alveolar spaces filled with neutrophilic infiltrate, proteinaceous debris, and fibrin deposition. These findings were absent in animals in the CON group. Electron microscopy of lung tissue from SPA-treated animals revealed injury to the alveolar epithelium and basement membranes, including intra-alveolar neutrophils and fibrin on the alveolar surface and intravascular fibrin (microthrombosis). CONCLUSIONS: In this particular porcine model, the nonimmunogenic polymer SPA caused a rapid exudative lung injury. This model may be useful to study ARDS caused by epithelial injury and inflammation.

Emerging evidence of the physical activity transition in Kenya.

BACKGROUND: Comparable data to examine the physical activity (PA) transition in African countries such as Kenya are lacking. METHODS: We assessed PA levels from urban (UKEN) and rural (RKEN) environments to examine any evidence of a PA transition. Nine- to twelve-year-old children participated in the study: n = 96 and n = 73 children from UKEN and RKEN, respectively. Pedometers were used to estimate children's daily step count. Parental perception regarding their child's PA patterns was collected via questionnaire (n = 172). RESULTS: RKEN children were more physically active than their UKEN counterparts with a mean average steps per day (± SE) of 14,700 ± 521 vs. 11,717 ± 561 (P < .0001) for RKEN vs. UKEN children respectively. 62.5% of the UKEN children spent 0 hours per week playing screen games compared with 13.1% of UKEN children who spent more than 11 hours per week playing screen games. Seventy percent of UKEN and 34% of RKEN parents reported being more active during childhood than their children respectively. CONCLUSIONS: Results of this study are indicative of a PA transition in Kenya. Further research is needed to gather national data on the PA patterns of Kenyan children to minimize the likelihood of a public health problem due to physical inactivity.

Optimizing pulmonary rehabilitation in chronic obstructive pulmonary disease--practical issues: a Canadian Thoracic Society Clinical Practice Guideline.

Pulmonary rehabilitation (PR) participation is the standard of care for patients with chronic obstructive pulmonary disease (COPD) who remain symptomatic despite bronchodilator therapies. However, there are questions about specific aspects of PR programming including optimal site of rehabilitation delivery, components of rehabilitation programming, duration of rehabilitation, target populations and timing of rehabilitation. The present document was compiled to specifically address these important clinical issues, using an evidence-based, systematic review process led by a representative interprofessional panel of experts. The evidence reveals there are no differences in major patient-related outcomes of PR between nonhospital- (community or home sites) or hospital-based sites. There is strong support to recommend that COPD patients initiate PR within one month following an acute exacerbation due to benefits of improved dyspnea, exercise tolerance and health-related quality of life relative to usual care. Moreover, the benefits of PR are evident in both men and women, and in patients with moderate, severe and very severe COPD. The current review also suggests that longer PR programs, beyond six to eight weeks duration, be provided for COPD patients, and that while aerobic training is the foundation of PR, endurance and functional ability may be further improved with both aerobic and resistance training.

Inhaled salbutamol and doping control: effects of dose on urine concentrations.

OBJECTIVE: The present study was designed to examine the dose-response relationship of inhaled salbutamol and its concentration in the urine while resting at various times after inhalation, and to compare these values against the current World Anti-Doping Code limits. DESIGN: An interventional, repeated-measures design. SETTING: Sport Medicine Clinic, University of British Columbia (Vancouver, Canada). PARTICIPANTS: Eight healthy, nonasthmatic males participated in this study (age = 28 +/- 6 years, height = 179.4 +/- 5.1 cm, and weight = 77.4 +/- 5.4 kg). INTERVENTION: Administration of three different doses of inhaled salbutamol (800, 400, and 200 microg) in a randomized fashion separated by at least 72 hours. MAIN OUTCOME MEASUREMENT: Urine concentration of nonsulphated salbutamol RESULTS: Urine concentrations were highly variable between subjects and increased as dose increased, with a significant difference noted between 800 and 200 microg at 30, 60, and 120 minutes after inhalation. Urine concentrations of salbutamol peaked at 60 minutes for all doses. No samples exceeded the doping criterion of 1000 ng/mL, and the maximum value observed was 904 ng/mL. CONCLUSION: These results indicate that after inhalation of doses up to 800 microg, urinary concentrations of salbutamol are well below the limits used in doping control.