Canadian prediction equations of spirometric lung function for Caucasian adults 20 to 90 years of age: results from the Canadian Obstructive Lung Disease (COLD) study and the Lung Health Canadian Environment (LHCE) study

Reference Values for Spirometry in Moroccan Adults

INTRODUCTION

This novel study aimed to establish spirometric reference values and prediction equations based on a sample of the adult Moroccan population, an endeavor that has not been attempted previously.

METHODS

In this cross-sectional study involving healthy Moroccan adults, data was collected through a mobile spirometry setup.

RESULTS

Our sample comprised 841 healthy adults (384 men and 457 women) aged 18-86 years who underwent spirometry. For both sexes, the Global Lung Function Initiative 2012 equations for Caucasians corresponded the best to the studied sample but were not perfectly compatible.

CONCLUSION

The spirometric prediction equations established in this study for Moroccan adults aged 18-86 years best represent the Moroccan population. More extensive future studies are needed to enrich the database of reference values and prediction equations derived from our research.

Effects of Face Masks on the Multiple Dimensions and Neurophysiological Mechanisms of Exertional Dyspnea

INTRODUCTION

During the coronavirus disease 2019 pandemic, public health officials widely adopted the use of face masks (FM) to minimize infections. Despite consistent evidence that FMs increase dyspnea, no studies have examined the multidimensional components of dyspnea or their underlying physiological mechanisms.

METHODS

In a randomized crossover design, 16 healthy individuals ( n = 9 women, 25 ± 3 yr) completed incremental cycling tests over three visits, where visits 2 and 3 were randomized to either surgical FM or no mask control. Dyspnea intensity and unpleasantness were assessed throughout exercise (0-10 Borg scale), and the Multidimensional Dyspnea Profile was administered immediately after exercise. Crural diaphragmatic EMG and esophageal pressure were measured using a catheter to estimate neural respiratory drive and respiratory muscle effort, respectively.

RESULTS

Dyspnea unpleasantness was significantly greater with the FM at the highest equivalent submaximal work rate achieved by a given participant in both conditions (iso-work; 5.9 ± 1.7 vs 3.9 ± 2.9 Borg 0-10 units, P = 0.007) and at peak exercise (7.8 ± 2.1 vs 5.9 ± 3.4 Borg 0-10 units, P = 0.01) with no differences in dyspnea intensity ratings throughout exercise compared with control. There were significant increases in the sensory quality of "smothering/air hunger" ( P = 0.01) and the emotional response of "anxiousness" ( P = 0.04) in the FM condition. There were significant increases in diaphragmatic EMG and esophageal pressure at select submaximal work rates, but no differences in heart rate, pulse oximetry-derived arterial oxygen saturation, or breathing frequency throughout exercise with FMs compared with control. FMs significantly reduced peak work rate and exercise duration (both P = 0.02).

CONCLUSIONS

FMs negatively impact the affective domain of dyspnea and increase neural respiratory drive and respiratory muscle effort during exercise, although the impact on other cardiorespiratory responses are minimal.

Abnormalities in pulmonary function and volumes in patients with CHD: a systematic review

BACKGROUND

Lung function and cardiac function are naturally correlated by sharing the thoracic cage and handling the whole cardiac output sequentially. However, lung function studies are rare in patients with CHD, although results worthy of investigation could be expected. This review summarises existing studies with the lung function parameters (spirometry and body plethysmography) in CHD patients during the last decade.

METHODS

A systematic review was performed in the relevant database (PubMed, Cochrane, and Scopus) in studies including paediatric and adult patients with CHD where lung parameters (spirometry, body plethysmography) were investigated from January 2010 to December 2020. Two independent reviewers evaluated the studies according to the Study Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies of the National Heart, Lung, and Blood Institute.

RESULTS

Eight studies investigated patients with Fontan palliation including 704 patients (306 female). Four studies included patients after repaired tetralogy of Fallot examining 219 patients (103 female), with one study using double. Further six studies included 3208 (1324 female) children and adults with various CHDs. Overall, four studies were categorised as "good", ten as "fair", and four as "poor". While the measurements were consistently standardised, references to calculate %predicted differed substantially across all studies. All evaluated studies showed reduced forced vital capacity in the majority of CHD patients.

CONCLUSIONS

Many CHD patients have a reduced forced vital capacity independent of their underlying defect. Spirometry should not only follow a standardised measure according to ATS (update 2019) but also stick to the 2012 GLI reference values.

Voluntary activation of the diaphragm after inspiratory pressure threshold loading

After a bout of isolated inspiratory work, such as inspiratory pressure threshold loading (IPTL), the human diaphragm can exhibit a reversible loss in contractile function, as evidenced by a decrease in transdiaphragmatic twitch pressure (PDI,TW ). Whether or not diaphragm fatigability after IPTL is affected by neural mechanisms, measured through voluntary activation of the diaphragm (D-VA) in addition to contractile mechanisms, is unknown. It is also unknown if changes in D-VA are similar between sexes given observed differences in diaphragm fatigability between males and females. We sought to determine whether D-VA decreases after IPTL and whether this was different between sexes. Healthy females (n = 11) and males (n = 10) completed an IPTL task with an inspired duty cycle of 0.7 and targeting an intensity of 60% maximal transdiaphragmatic pressure until task failure. PDI,TW and D-VA were measured using cervical magnetic stimulation of the phrenic nerves in combination with maximal inspiratory pressure maneuvers. At task failure, PDI,TW decreased to a lesser degree in females vs. males (87 ± 15 vs. 73 ± 12% baseline, respectively, p = 0.016). D-VA decreased after IPTL but was not different between females and males (91 ± 8 vs. 88 ± 10% baseline, respectively, p = 0.432). When all participants were pooled together, the decrease in PDI,TW correlated with both the total cumulative diaphragm pressure generation (R2  = 0.43; p = 0.021) and the time to task failure (TTF, R2 = 0.40; p = 0.30) whereas the decrease in D-VA correlated only with TTF (R2  = 0.24; p = 0.041). Our results suggest that neural mechanisms can contribute to diaphragm fatigability, and this contribution is similar between females and males following IPTL.

Changes in interpretation of spirometry by implementing the GLI 2012 reference equations: impact on patients tested in a hospital-based PFT lab in a large metropolitan city

BACKGROUND

The Global Lung Function Initiative (GLI-2012) focused on race/ethnicity as an important factor in determining reference values. This study evaluated the effects of changing from Canadian reference equations developed from an all-Caucasian cohort with European ancestry to the GLI-2012 on the interpretation of spirometry in a multiethnic population and aimed to identify the ethnic groups affected by discrepant interpretations.

METHODS

Clinically indicated spirometry in a multiethnic population (aged 20-80 years) collected from 2018 to 2021 was analysed. The predicted and lower limit of normal (LLN) values were calculated using three sets of reference equations: Canadian, GLI-race/ethnic-based (GLI-Race) and GLI-race/ethnic-neutral (GLI-Other). We compared the prevalence of concordance in the abnormal diagnoses (defined as <LLN) for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and FEV₁/FVC among the three reference values, and evaluated whether race/ethnicity was associated with discordance.

RESULTS

Data from 406 participants were evaluated (non-Caucasian 43.6%). There was 85%-87% concordance for normal/abnormal FVC and FEV₁ interpretations among the Canadian, GLI-Race and GLI-Other reference equations. In all ethnic groups, application of the Canadian references for interpretation led to a higher prevalence of abnormal (<LLN) FVC and FEV₁compared with GLI-Race and GLI-Other. This trend was more prominent in Black, South-East Asian and Mixed/other ethnic groups when comparing the Canadian to the GLI-Race equations. In contrast, the discordance rates were similar among ethnic groups when compared with the GLI-Other reference equations. Interpretation of FEV₁/FVC had a high rate of agreement among all equations.

CONCLUSION

Interpretation using Canadian reference equations was associated with a higher prevalence of restrictive physiology compared with the GLI-2012 equations, particularly if the GLI-Race were used. These observations were mostly found in non-white Caucasian groups, highlighting the need to choose reference equations that reflect closely the ethnic mix of the population being evaluated in order to optimise patient management.

Sex Differences in Diaphragm Voluntary Activation after Exercise

INTRODUCTION

The female diaphragm develops less fatigue after high-intensity exercise compared with males. Diaphragm fatigability is typically defined as a decrease in transdiaphragmatic twitch pressure (Pdi,TW) and represents the contractile function of the muscle. However, it is unclear whether this sex difference persists when examining changes in voluntary activation, which represents a neural mechanism contributing to fatigability.

PURPOSE

This study aimed to determine if high-intensity cycling results in a decrease in diaphragm voluntary activation (D-VA) and to explore if the decrease in D-VA is different between sexes.

METHODS

Twenty-five participants (15 females) completed a single bout of high-intensity constant load cycling. D-VA and Pdi,TW were measured before and after exercise using cervical magnetic stimulation of the phrenic nerves to assess diaphragm fatigability.

RESULTS

Participants were of similar aerobic fitness when expressed relative to predicted values (females: 114% ± 25% predicted, males: 111% ± 11% predicted; P = 0.769). Pdi,TW decreased relative to baseline to 85.2% ± 16.7% and 70.3% ± 12.4% baseline (P = 0.012) in females and males, respectively, immediately after exercise. D-VA also decreased in both females and males immediately after exercise. The decrease in D-VA was less in females compared with males (95.4% ± 4.9% baseline vs 87.4% ± 10.8% baseline, respectively; P = 0.018).

CONCLUSIONS

D-VA decreases after whole-body exercise in both females and males, although the magnitude of the decrease is not as large in females compared with males. The findings of this study suggest that the female diaphragm is more resistant to both contractile and neural mechanisms of fatigability after whole-body exercise.

Early COPD Risk Decision for Adults Aged From 40 to 79 Years Based on Lung Radiomics Features

Background

Chronic obstructive pulmonary disease (COPD), a preventable lung disease, has the highest prevalence in the elderly and deserves special consideration regarding earlier warnings in this fragile population. The impact of age on COPD is well known, but the COPD risk of the aging process in the lungs remains unclear. Therefore, it is necessary to understand the COPD risk of the aging process in the lungs, providing an early COPD risk decision for adults.

Methods

COPD risk is evaluated for adults to make an early COPD risk decision from the perspective of lung radiomics features. First, the subjects are divided into four groups according to the COPD stages. Their ages are divided into eight equal age intervals in each group. Second, four survival Cox models are established based on the lung radiomics features to evaluate the risk probability from COPD stage 0 to suffering COPD and COPD stages. Finally, four risk ranks are defined by equally dividing the COPD risk probability from 0 to 1. Subsequently, the COPD risk at different stages is evaluated with varying age intervals to provide an early COPD risk decision.

Results

The evaluation metrics area under the curve (AUC)/C index of four survival Cox models are 0.87/0.94, 0.84/0.83, 0.94/0.89, and 0.97/0.86, respectively, showing the effectiveness of the models. The risk rank levels up every 5 years for the subjects who had suffered COPD after 60. For the subjects with COPD stage 0, the risk rank of suffering COPD stage I levels up every 5 years after the age of 65 years, and the risk rank of suffering COPD stages II and III &amp; IV levels up every 5 years after the age of 70 years.

Conclusion

Once the age is above 60 years, the patients with COPD need to take action to prevent the progress and deterioration of COPD. Once the age is above 65 years, the patients with COPD stage 0 need to take precautions against COPD.

Sex, gender and the pulmonary physiology of exercise

In this review, we detail how the pulmonary system's response to exercise is impacted by both sex and gender in healthy humans across the lifespan. First, the rationale for why sex and gender differences should be considered is explored, and then anatomical differences are highlighted, namely that females typically have smaller lungs and airways than males. Thereafter, we describe how these anatomical differences can impact functional aspects such as respiratory muscle energetics and activation, mechanical ventilatory constraints, diaphragm fatigue, and pulmonary gas exchange in healthy adults and children. Finally, we detail how gender can impact the pulmonary response to exercise.

Biological sex can influence the pulmonary response to exercise in healthy individuals across the lifespanhttps://bit.ly/3ejMDrv

Airway luminal area and the resistive work of breathing during exercise in healthy young females and males

We examined the relationship between the work of breathing (W_b) during exercise and in vivo measures of airway size in healthy females and males. We hypothesized that sex differences in airway luminal area would explain the larger resistive W_b during exercise in females. Healthy participants (n = 11 females and n = 11 males; 19-30 yr) completed a cycle exercise test to exhaustion where W_b was assessed using an esophageal balloon catheter. On a separate day, each participant underwent a bronchoscopy procedure for optical coherence tomography measures of seven airways. In vivo measures of luminal area were made for the fourth to eighth airway generations. A composite index of airway size was calculated as the sum of the luminal area for each generation, and the total area was calculated based on Weibel's model. We found that index of airway size (males: 37.4 ± 6.3 mm² vs. females: 27.5 ± 7.4 mm²) and airway area calculated based on Weibel's model (males: 2,274 ± 557 mm² vs. females: 1,594 ± 389 mm²) were significantly larger in males (both P = 0.003). When minute ventilation was greater than ∼60 L·min^-1, the resistive W_b was higher in females. At the highest equivalent flow achieved by all subjects, resistance to inspired flow was larger in females and significantly associated with two measures of airway size in all subjects: index of airway size (r = 0.524, P = 0.012) and Weibel area (r = 0.525, P = 0.012). Our findings suggest that innate sex differences in luminal area result in a greater resistive W_b during exercise in females compared with males.NEW & NOTEWORTHY We hypothesized that the higher resistive work of breathing in females compared with males during high-intensity exercise is due to smaller airways. In vivo measures of the fourth to eighth airway generations made using optical coherence tomography show that females tend to have smaller airway luminal areas of the fourth to sixth airway generations. Sex differences in airway luminal area result in a greater resistive work of breathing during exercise in females compared with males.

Short-Term Acute Exposure to Wildfire Smoke and Lung Function among Royal Canadian Mounted Police (RCMP) Officers

The increasing incidence of extreme wildfire is becoming a concern for public health. Although long-term exposure to wildfire smoke is associated with respiratory illnesses, reports on the association between short-term occupational exposure to wildfire smoke and lung function remain scarce. In this cross-sectional study, we analyzed data from 218 Royal Canadian Mounted Police officers (mean age: 38 ± 9 years) deployed at the Fort McMurray wildfires in 2016. Individual exposure to air pollutants was calculated by integrating the duration of exposure with the air quality parameters obtained from the nearest air quality monitoring station during the phase of deployment. Lung function was measured using spirometry and body plethysmography. Association between exposure and lung function was examined using principal component linear regression analysis, adjusting for potential confounders. In our findings, the participants were predominantly male (71%). Mean forced expiratory volume in 1 s (FEV₁), and residual volume (RV) were 76.5 ± 5.9 and 80.1 ± 19.5 (% predicted). A marginal association was observed between air pollution and higher RV [β: 1.55; 95% CI: -0.28 to 3.37 per interquartile change of air pollution index], but not with other lung function indices. The association between air pollution index and RV was significantly higher in participants who were screened within the first three months of deployment (2.80; 0.91 to 4.70) than those screened later (-0.28; -2.58 to 2.03), indicating a stronger effect of air pollution on peripheral airways. Acute short-term exposure to wildfire-associated air pollutants may impose subtle but clinically important deleterious respiratory effects, particularly in the peripheral airways.

Case Studies in Physiology: Cardiopulmonary exercise testing and inspiratory muscle training in a 59-year-old, four years after an extra-pleural pneumonectomy

This case report characterizes the physiological responses to incremental cycling and determines the effects of 12 weeks of inspiratory muscle training (IMT) on respiratory muscle strength, exercise capacity and dyspnea in a physically active 59-year-old female, four years after a left-sided extra-pleural pneumonectomy (EPP). On separate days, a symptom limited incremental exercise test and a constant work rate (CWR) test at 75% of peak work rate (WR) were completed, followed by 12 weeks of IMT and another CWR test. IMT consisted of two sessions of 30 repetitions twice daily for 5 days per week. Physiological and perceptual variables were measured throughout each exercise test. The participant had a total lung capacity that was 43% predicted post-EPP. A rapid and shallow breathing pattern was adopted throughout exercise, and the ratio of minute ventilation to carbon dioxide output was elevated for a given work rate. Oxygen uptake was 74%predicted and WR was 88%predicted. Following IMT, maximal inspiratory pressure improved by 36% (-27.1 cmH₂O) and endurance time by 31s, with no observable changes in any submaximal or peak cardiorespiratory variables during exercise. The intensity and unpleasantness of dyspnea increased by 2 and 3 Borg 0-10 units, respectively, at the highest equivalent submaximal exercise time achieved on both tests. Despite having undergone a significant reduction in lung volume post-EPP, the participant achieved a relatively normal peak incremental WR, which may reflect a high level of physical conditioning. This case report also demonstrates that IMT can effectively increase respiratory muscle strength several years following EPP.

Screening for COPD in primary care, involving dentists, pharmacists, physiotherapists, nurses and general practitioners (the UNANIME pilot study)

BACKGROUND

COPD is underdiagnosed and is projected to be the third cause of death in 2030. However, recent reviews do not recommend screening for COPD in the general population.

METHODS

We conducted a prospective study to assess the feasibility of implementing COPD screening in a high-risk COPD population, with the help of various healthcare professionals (General practitioners, pharmacists, dentists, physiotherapists, and nurses). Participants filled out a questionnaire, performed a spirometry (COPD6™) and counselling was performed, including smoking cessation and chest physician referral. Participants were contacted at two months to evaluate the effect of the intervention.

RESULTS

Between April 7th, 2017 and July 30th, 2018, 157 participants filled out the questionnaires, performed spirometry and were contacted at two months. Thirty-five out of 157 (22% [95% CI, 15.8-28.8]) participants were detected with an airflow obstruction (FEV1/FEV6 < 0.7), using COPD6™ device. At the two-month-contact, 68 participants (43%, [95%CI 35.5-51.1]) were engaged in a smoking cessation program and 22 (14% [95 % CI, 8.6-19.4]) reported having quit smoking.

CONCLUSION

This pilot study suggested that a predefined screening of COPD by different healthcare professionals could be implemented in primary care and might be part of counselling for smoking cessation (NCT03104348 on ClinicalTrials.gov).

Research and Healthcare Priorities of Individuals Living with COPD

This study describes the research and healthcare priorities of individuals living with COPD. On an online survey, individuals living with COPD assigned a percentage of funding to 22 research priorities and a percentage of time spent communicating with a healthcare provider to 24 healthcare priorities, indicating which topics were most important. For each research and healthcare priority, we examined the selection frequency of the priority and used chi-square analyses to examine differences in priority selection by quartiles of airflow obstruction (percent predicted forced expiratory volume in 1-sec (FEV₁%predicted)) and breathlessness burden and exacerbation risk. Based on participants' responses (N = 148, 47% women; Mean ± Standard Deviation age = 68 ± 9 yrs) relief of breathlessness was the most often selected research (76% of respondents) and healthcare priority (61% of respondents). It was selected most often, regardless of disease severity or breathlessness burden and exacerbation risk. We found differences for disease severity and breathlessness burden and exacerbation risk in some research priorities (e.g., to improve the maximal amount of exercise of adults living with COPD in and out of the home (χ²₍₃₎ = 9.97, Cramer's V =.28) and healthcare priorities (e.g., increase your ability to exercise (χ²₍₃₎ = 9.72, Cramer's V =.27)). This study provides empirical evidence that relief of breathlessness is a top research and healthcare priority for individuals living with COPD. Future healthcare and research activities should align with the priorities of individuals with COPD to improve their care by minimizing disease/symptom burden and optimizing health-related quality of life.

Graded exercise test with or without load carriage similarly measures maximal oxygen uptake in young males and females

The aim of this was to compare the effects of the graded exercise test (GXT) with or without load carriage on maximal oxygen uptake ([Formula: see text]) heart rate (HR), and expired ventilation ([Formula: see text]) and blood lactate in young healthy males and females. The study included ten females (age:20.2±0.7 yrs) and ten males (age:19.5±0.7 yrs) who performed the modified Bruce protocol at five load conditions; unloaded, 5, 10, 15, and 20% of body weight (BW) (kg). All the tests were performed in random order, at least 48 hours apart. During the GXTs, HR, [Formula: see text], [Formula: see text], workload and test duration were recorded and blood lactate concentration was measured before and immediately after the GXTs. [Formula: see text] remained unchanged during the GXTs in load and unloaded conditions for both sexes (p>0.05). Test duration was significantly less in females during the GXT with 15% BW (15.9±0.51 min vs. 18.1±1.14 min; p = 0.014) and 20% BW load carriage (15.2±0.75 min vs. 18.1±1.14 min; p = 0.020), compared to the unloaded GXT. Males showed significant decrease in the test duration during the GXT with load 15% BW (20.5±0.53 min vs. 22.8±0.61 min; p = 0.047) and with 20% BW (19.6±0.42 min vs. 22.8±0.71 min; p = 0.004), compared to the GXT with 5% BW. [Formula: see text] statistically decreased in female subjects only at 15% BW compared to 20% BW (15% BW = 77.9 ± 10.5 L/min vs. 15% BW = 72.0 ± 10.9 L/min; p = 0.045). There was no difference observed in maximal HR and blood lactate concentration between the GXTs in load and unloaded conditions. This study indicates that no matter the load % used during the GXT, [Formula: see text], but not total exercise time, remains the same in young males and females.

Effects of the Turbine™ on Ventilatory and Sensory Responses to Incremental Cycling

INTRODUCTION

The Turbine™ is a nasal dilator marketed to athletes to increase airflow, which may serve to reduce dyspnea and improve exercise performance, presumably via reductions in the work of breathing (WOB). However, the unpublished data supporting these claims were collected in individuals at rest that were exclusively nasal breathing. These data are not indicative of how the device influences breathing during exercise at higher ventilations when a larger proportion of breathing is through the mouth. Accordingly, the purpose of this study was to empirically test the efficacy of the Turbine™ during exercise. We hypothesized that the Turbine™ would modestly reduce the WOB at rest and very low exercise intensities but would have no effect on the WOB at moderate to high exercise intensities.

METHODS

We conducted a randomized crossover study in young, healthy individuals (7M:1F; age = 27 ± 5 yr) with normal lung function. Each participant performed two incremental cycle exercise tests to exhaustion with the Turbine™ device or under a sham control condition. For the sham control condition, participants were told they were breathing a low-density gas to reduce the WOB, but they were actually breathing room air. The WOB was determined through the integration of ensemble averaged esophageal pressure-volume loops. Standard cardiorespiratory measures were recorded using a commercially available metabolic cart. Dyspnea was assessed throughout exercise using the 0-10 Borg scale.

RESULTS

Peak V˙O2 and work rate were not different between conditions (P = 0.70 and P = 0.35, respectively). In addition, there was no interaction or main effect of condition on dyspnea, ventilation, or WOB throughout the exercise (all P > 0.05).

CONCLUSION

These findings suggest that the Turbine™ does not reduce the WOB and has no effect on dyspnea or exercise capacity.

Non-Malignant Respiratory Illnesses in Association with Occupational Exposure to Asbestos and Other Insulating Materials: Findings from the Alberta Insulator Cohort

Many insulating materials are used in construction, although few have been reported to cause non-malignant respiratory illnesses. We aimed to investigate associations between exposures to insulating materials and non-malignant respiratory illnesses in insulators. In this cross-sectional study, 990 insulators (45 ± 14 years) were screened from 2011-2017 in Alberta. All participants underwent pulmonary function tests and chest radiography. Demographics, work history, and history of chest infections were obtained through questionnaires. Chronic obstructive pulmonary disease (COPD) was diagnosed according to established guidelines. Associations between exposures and respiratory illnesses were assessed by modified Poisson regression. Of those screened, 875 (88%) were males. 457 (46%) participants reported having ≥ 1 chest infection in the past 3 years, while 156 (16%) were diagnosed with COPD. In multivariate models, all materials (asbestos, calcium silicate, carbon fibers, fiberglass, and refractory ceramic fibers) except aerogels and mineral fibers were associated with recurrent chest infections (prevalence ratio [PR] range: 1.18-1.42). Only asbestos was associated with COPD (PR: 1.44; 95% confidence interval [CI]: 1.01, 2.05). Therefore, occupational exposure to insulating materials was associated with non-malignant respiratory illnesses, specifically, recurrent chest infections and COPD. Longitudinal studies are urgently needed to assess the risk of exposure to these newly implemented insulation materials.

Peripheral chemoresponsiveness during exercise in male athletes with exercise-induced arterial hypoxaemia

NEW FINDINGS

What is the central question of this study? Do highly trained male endurance athletes who develop exercise-induced arterial hypoxaemia (EIAH) demonstrate reduced peripheral chemoresponsiveness during exercise? What is the main finding and its importance? Those with the lowest arterial saturation during exercise have a smaller ventilatory response to hypercapnia during exercise. There was no significant relationship between the hyperoxic ventilatory response and EIAH. The findings suggest that peripheral chemoresponsiveness to hypercapnia during exercise could play a role in the development of EIAH. The findings improve our understanding of the mechanisms that contribute to EIAH.

ABSTRACT

Exercise-induced arterial hypoxaemia (EIAH) is characterized by a decrease in arterial oxygen tension and/or saturation during whole-body exercise, which may in part result from inadequate alveolar ventilation. However, the role of peripheral chemoresponsiveness in the development of EIAH is not well established. We hypothesized that those with the most severe EIAH would have an attenuated ventilatory response to hyperoxia and hypercapnia during exercise. To evaluate this, on separate days, we measured ventilatory sensitivity to hyperoxia and separately hypercapnia at rest and during three different exercise intensities (25, 50% of V ̇ O 2 max and ventilatory threshold (∼67% of V ̇ O 2 max )) in 12 males cyclists ( V ̇ O 2 max  = 66.6 ± 4.7 ml kg^-1  min^-1 ). Subjects were divided into two groups based on their end-exercise arterial oxygen saturation (ear oximetry, S p O 2 ): a normal oxyhaemoglobin saturation group (NOS, S p O 2  = 93.4 ± 0.4%, n = 5) and a low oxyhaemoglobin saturation group (LOS, S p O 2  = 89.9 ± 0.9%, n = 7). There was no difference in V ̇ O 2 max (66.4 ± 2.9 vs. 66.8 ± 6.0 ml kg^-1  min^-1 , respectively, P = 0.9), peak ventilation during maximal exercise (182 ± 15 vs. 197 ± 32 l min^-1 , respectively, P = 0.36) or ventilatory response to hyperoxia (P = 0.98) at any exercise intensity between NOS and LOS groups. However, those in the LOS group had a significantly lower ventilatory response to hypercapnia (P = 0.004, (η²  = 0.18). There was also a significant relationship between the mean hypercapnic response and end-exercise S p O 2 (r = 0.75, P = 0.009) but not between the mean hyperoxic response and end-exercise S p O 2 (r = 0.21, P = 0.51). A blunted hypercapnic ventilatory response may contribute to EIAH in highly trained men due to a failure to increase ventilation sufficiently to offset exercise-induced gas exchange impairments.

Reliability of diaphragm voluntary activation measurements in healthy adults

Voluntary activation can be used to assess central fatigue of the diaphragm after tasks such as exercise or inspiratory muscle loading. Cervical magnetic stimulation (CMS) of the phrenic nerves elicits an involuntary contraction, or twitch, of the diaphragm. This twitch is quantified based on a measure of transdiaphragmatic pressure and can be used to evaluate diaphragm contractile function and diaphragm voluntary activation (diaphragm-VA). The test-retest reliability of diaphragm-VA using CMS is currently unknown. Thirteen participants (4 male, 9 female; aged 25 ± 3 years) performed a series of interpolated twitch manoeuvres, which included a maximal inspiratory effort against a semi-occluded mouthpiece and 2 CMS-stimuli, 1 during the inspiratory manoeuvre and 1 after when the participant returned to functional residual capacity to quantify diaphragm-VA. Intraclass correlation coefficients (ICCs) and standard error of measurement (SEM) measured between-day and within-session reliability of diaphragm-VA, respectively. Maximal diaphragm-VA values were 91% (SD: 6; SEM: 3.9) and 92% (SD: 5; SEM: 2.2) during visits 1 and 2 (p = 0.68), respectively, and displayed "good" between-day reliability (ICC: 0.88; 95% confidence interval: 0.67-0.95; SEM: 2.7). Our results suggest that assessing diaphragm-VA using CMS is reliable in young healthy adults. Measuring diaphragm-VA may provide additional insight into the consequences and mechanisms of diaphragm fatigue. Novelty: Magnetic stimulation of the phrenic nerves can reliably measure voluntary activation of the diaphragm. Diaphragm voluntary activation can be used to provide additional insight into fatigability of the diaphragm.

Description of Participation in Daily and Social Activities for Individuals with COPD

This study described the participation in daily and social activities and the perceived barriers and facilitators to participation of individuals with chronic obstructive pulmonary disease (COPD). Individuals, recruited from outpatient clinics, responded to a survey on their participation in, and barriers and facilitators towards, 26 daily and social activities, divided into 3 categories: (1) physical activity and movement (PAM); (2) self-care; and (3) social engagement. For each activity, chi-square analyses were used to examine participation differences by individuals': quartiles of airflow obstruction [percent predicted forced expiratory volume in 1 second (FEV1%predicted)] and breathlessness burden and exacerbation risk. Of the 200 participants (47% women; mean ± standard deviation age = 68 ± 9 years), most wanted to increase their participation in PAM activities (range 21-75%) and significant differences were found in 5/10 PAM activities for individuals' breathlessness burden and exacerbation risk (e.g., more individuals than expected in group A (modified Medical Research Council breathlessness score <2 and 0-1 exacerbations in past 12 months) participated in regular exercise as much as they wanted (χ₍₉₎²=20.43, Cramer's V=.23)). Regardless of the degree of airflow obstruction or breathlessness burden and exacerbation risk, the most common barrier to participation was breathlessness (p<.001, η²_p=.86) and the most common facilitator was engaging as part of their routine (p<.001, η²_p=.75). Individuals with COPD want to increase their participation in daily and social activities but are limited by breathlessness. Strategies to alleviate breathlessness should be identified/prioritized and incorporated into individuals' daily routines to meet their self-reported participation objectives in daily and social activities.

"Bayis Ilh Tus - a strong breath" a community-based research project to estimate the prevalence of chronic obstructive pulmonary disease in remote and rural first nations communities in Canada: research protocol

Background

Respiratory health conditions appear to be more common among First Nations people versus non-First Nations people in Canada. However, the prevalence of chronic obstructive pulmonary disease (COPD) and its associated risk factors in First Nations communities are unknown. This project aims to estimate the prevalence of COPD in several First Nations communities in British Columbia, Canada and to characterize respiratory symptoms, COPD risk factors, and healthcare utilization.

Methods

This project is approved by both the University of British Columbia and Carrier Sekani Family Services Research Ethics Boards. We will randomly sample 220 adults, 30 years and older, from 11 participating First Nations. Each participant will complete pre- and post-bronchodilator spirometry tests and the adapted American Thoracic Society Epidemiological Questionnaire with items about smoking history, respiratory symptoms, co-morbidities, and exposures, in order to identify the presence of COPD and its associated individual, occupational, and community risk factors. Homes will be assessed for air quality measures including particulate matter, carbon monoxide and carbon dioxide, and humidity. Health care utilization will be abstracted from the electronic medical record.

Discussion

This is the first project in Canada to estimate the prevalence of COPD in First Nations communities using a random-sampling approach to recruitment. Additionally, although this study will collect detailed information on smoking history, we will also characterize past and current risk factors beyond cigarette smoking. Finally, our methodology ensures that the benefits to the communities are realized during the study period. Individual results will be shared with individuals and health providers to facilitate care. Air quality results will be sent to each Nation’s governing council to facilitate remediation where necessary.

Trial registration

The study has been retrospectively registered at clinicaltrials.gov (NCT04105088).

The Lung Function Laboratory to Assist Clinical Decision-making in Pulmonology: Evolving Challenges to an Old Issue

The lung function laboratory frequently provides relevant information to the practice of pulmonology. Clinical interpretation of pulmonary function and exercise tests, however, has been complicated more recently by temporal changes in demographic characteristics (higher life expectancy), anthropometric attributes (increased obesity prevalence), and the surge of polypharmacy in a sedentary population with multiple chronic degenerative diseases. In this narrative review, we concisely discuss some key challenges to test interpretation that have been affected by these epidemiologic shifts: (a) the confounding effects of advanced age and severe obesity, (b) the contemporary controversies in the diagnosis of obstruction (including asthma and/or COPD), (c) the importance of considering the diffusing capacity of the lung for carbon monoxide (Dlco)/"accessible" alveolar volume (carbon monoxide transfer coefficient) in association with Dlco to uncover the causes of impaired gas exchange, and (d) the modern role of the pulmonary function laboratory (including cardiopulmonary exercise testing) in the investigation of undetermined dyspnea. Following a Bayesian perspective, we suggest interpretative algorithms that consider the pretest probability of abnormalities as indicated by additional clinical information. We, therefore, adopt a pragmatic approach to help the practicing pulmonologist to apply the information provided by the lung function laboratory to the care of individual patients.

The Impact of Cycling Cadence on Respiratory and Hemodynamic Responses to Exercise

PURPOSE

The physiological consequences of freely chosen cadence during cycling remains poorly understood. We sought to determine the effect of cadence on the respiratory and hemodynamic response to cycling exercise.

METHODS

Eleven cyclists (10 males, 1 female; age, 27 ± 6 yr; V˙O2max = 60.8 ± 3.7 mL·kg·min) completed four, 6-min constant-load cycling trials at 10% below their previously determined gas exchange threshold (i.e., 63% ± 5% peak power) while pedaling at 60, 90, and 120 rpm, and a freely chosen cadence (94.3 ± 6.9 rpm) in randomized order. Standard cardiorespiratory parameters were measured and an esophageal electrode balloon catheter was used to assess electromyography of the diaphragm (EMGdi) and the work of breathing (Wb). Leg blood flow index (BFI) was determined on four muscles using near-infrared spectroscopy with indocyanine green dye injections.

RESULTS

Oxygen uptake (V˙O2) increased as a function of increasing cadence (all pairwise comparisons, P < 0.05). The EMGdi and Wb were significantly greater at 120 rpm compared with all other conditions (all P < 0.01). Vastus medialis and semitendinosus BFI were significantly greater at 120 rpm compared with 60 and 90 rpm (all P < 0.05). Gastrocnemius BFI was higher at 120 rpm compared with all other cadences (all P < 0.01). No difference in BFI was found in the vastus lateralis (P = 0.06). Blood flow index was significantly correlated with the increase in V˙O2 with increasing cadence in the medial gastrocnemius (P < 0.001) and approached significance in the vastus lateralis (P = 0.09), vastus medialis (P = 0.06), and semitendinosus (P = 0.09). There was no effect of cadence on Borg 0-10 breathing or leg discomfort ratings (P > 0.05).

CONCLUSIONS

High cadence cycling at submaximal exercise intensities is metabolically inefficient and increases EMGdi, Wb, and leg muscle blood flow relative to slower cadences.

Establishment of Reference Norms for Lung Function Parameters of Healthy Sri Lankan Tamils

Spirometry and Peak Expiratory Flow Rate (PEFR) are important measurements in diagnosing and monitoring of COPD and asthma. Ethnic specific reference equations are necessary in interpretation of these parameters. However, equations for Sri Lankan Tamil adults are not available. This study aims to establish reference equations for lung function parameters of Sri Lankan Tamils. A descriptive cross sectional study was carried out in all 5 districts of Northern Sri Lanka. Participants were selected by cluster sampling. Base line data were obtained by a questionnaire. Height, sitting height, weight, arm span, mid arm circumference, and chest expansion were measured. Respiratory functions were assessed by a calibrated spirometer (Cosmed Micro Quark, Italy) and Wright compatible peak expiratory flow meter. Means, and standard deviations for Vital Capacity (VC), Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), FEV1%, Peak Expiratory Flow Rate (PEFR) and for other forced expiratory parameters of 775 males and 687 females were determined. Lung function parameters have significant (p < 0.05) positive correlations with most of the anthropometric measures. Age had a significant (p < 0.05) negative correlation with lung function parameters in adults >20 years and positive correlation (p < 0.05) in 14-20 years group. Step wise multiple regression analysis was used to determine the prediction equations. Also equations based on age, height and age, arm span were derived. Age, height based equations were retested in the same population. Predicted values by the developed equations had better agreement than that of GLI 2012 equations. This can be useful in assessing the respiratory function in Sri Lankan Tamil population as there are no already existing equations.

Qualitative dimensions of exertional dyspnea in fibrotic interstitial lung disease

Unsatisfied inspiration is commonly reported during exercise by patients with interstitial lung disease (ILD). However, the physiological basis of perceived dyspnea quality in this population has not been evaluated. We examined the relationship between dyspnea quality and indices of ventilatory-mechanical limitations during exercise in patients with fibrotic ILD. Sixteen fibrotic ILD patients (12 male) with a median age of 64 years (range 49-81), FVC 71%-predicted (51-100), and DL_CO 47%-predicted (27-77) performed incremental and constant work-rate cycle exercise tests to exhaustion. Ventilatory responses were recorded at rest, throughout exercise, and at peak exercise. Dyspnea quality was serially assessed using a 4-item list from which participants selected the phrase that best described their breathing compared to rest. Increased work/effort was the dominant descriptor of dyspnea throughout exercise, but with increased selection of unsatisfied inspiration following the inflection point of tidal volume relative to ventilation. Delaying or preventing ILD patients from reaching a critically reduced IRV may have implications for symptom management.

Ventilatory and sensory responses to incremental exercise in adults with a Fontan circulation

Many adults with single-ventricle congenital heart disease who have undergone a Fontan procedure have abnormal pulmonary function resembling restrictive lung disease. Whether this contributes to ventilatory limitations and increased dyspnea has not been comprehensively studied. We recruited 17 Fontan participants and 17 healthy age- and sex-matched sedentary controls. All participants underwent complete pulmonary function testing followed by a symptom-limited incremental cardiopulmonary cycle exercise test with detailed assessments of dyspnea and operating lung volumes. Fontan participants and controls were well matched for age, sex, body mass index, height, and self-reported physical activity levels (all P > 0.05), although Fontan participants had markedly reduced cardiorespiratory fitness and peak work rates ( P < 0.001). Fontan participants had lower values for most pulmonary function measurements relative to controls with 65% of Fontan participants showing evidence of a restrictive ventilatory defect. Relative to controls, Fontan participants had significantly higher breathing frequency, end-inspiratory lung volume (% total lung capacity), ventilatory inefficiency (high ventilatory equivalent for CO2), and dyspnea intensity ratings at standardized absolute submaximal work rates. There were no between-group differences in qualitative descriptors of dyspnea. The restrictive ventilatory defect in Fontan participants likely contributes to their increased breathing frequency and end-inspiratory lung volume during exercise. This abnormal ventilatory response coupled with greater ventilatory inefficiency may explain the increased dyspnea intensity ratings in those with a Fontan circulation. Interventions that enhance the ventilatory response to exercise in Fontan patients may help optimize exercise rehabilitation interventions, resulting in improved exercise tolerance and exertional symptoms.

NEW & NOTEWORTHY This is the first study to comprehensively characterize both ventilatory and sensory responses to exercise in adults that have undergone the Fontan procedure. The majority of Fontan participants had a restrictive ventilatory defect. Compared with well-matched controls, Fontan participants had increased breathing frequency, end-inspiratory lung volume, and ventilatory inefficiency. These abnormal ventilatory responses likely form the mechanistic basis for the increased dyspnea intensity ratings observed in our Fontan participants during exercise.

Sex differences in large conducting airway anatomy

Airway luminal area is the major determinant of resistance to airflow in the tracheobronchial tree. Women may have smaller central conducting airways than men; however, previous evidence is confounded by an indirect assessment of airway geometry and by subjects with prior smoking history. The purpose of this study was to examine the effect of sex on airway size in healthy nonsmokers. Using low-dose high-resolution computed tomography, we retrospectively assessed airway luminal area in healthy men ( n = 51) and women ( n = 73) of varying ages (19-86 yr). Subjects with a positive smoking history, cardiopulmonary disease, or a body mass index > 40 kg/m² were excluded. Luminal areas of the trachea, right and left main bronchus, bronchus intermediate, left and right upper lobes, and the left lower lobe were analyzed at three discrete points. The luminal areas of the conducting airways were ~26%-35% smaller in women. The trachea had the largest differences in luminal area between men and women (298 ± 47 vs. 195 ± 28 mm² or 35% smaller for men and women, respectively), whereas the left lower lobe had the smallest differences (57 ± 15 vs. 42 ± 9 mm² or 26% smaller for men and women, respectively). When a subset of subjects was matched for height, the sex differences in airway luminal area persisted, with women being ~20%-30% smaller. With all subjects, there were modest relationships between height and airway luminal area ( r = 0.73-0.53, P < 0.05). Although there was considerable overlap between sexes, the luminal areas of the large conducting airways were smaller in healthy women than in men. NEW & NOTEWORTHY Previous evidence for sex differences in airway size has been confounded by indirect measures and/or cohorts with significant smoking histories or pathologies. We found that central airways in healthy women were significantly smaller (~26%-35%) than men. The significant sex-difference in airway size was attenuated (20%-30% smaller) but preserved in a subset of subjects matched for height. Over a range of ages, healthy women have smaller central airways than men.

Movement behaviours are associated with lung function in middle-aged and older adults: a cross-sectional analysis of the Canadian longitudinal study on aging

Background

Physical activity has been shown to attenuate the age-associated decline in lung function; however, there is little research evaluating different movement behaviours as potential correlates of lung function. Modifiable determinants need to be identified, as the prevalence of chronic respiratory disease is on the rise. The purpose of this study was to investigate associations of self-reported movement behaviours (i.e., sitting time, walking, different intensities of physical activity, and strengthening activities), with lung function in middle-aged and older adults without a respiratory disease, according to their smoking history.

Methods

Data from participants of the Canadian Longitudinal Study on Aging were used for analysis (n = 16,839). Lung function was assessed using spirometry. A modified version of the Physical Activity Scale for the Elderly was used to assess sitting time and physical activity levels. Smoking status was classified as non-smoking, < 10 pack years smoking, and 10 or more pack years of smoking. The association between movement behaviours and lung function was assessed using hierarchical linear regression models with all covariates (age, sex, smoking status, body mass index, education, retirement status, and sleep duration) entered into block 1, and all movement behaviours entered into block 2.

Results

All movement behaviours were associated with Forced Expiratory Volume in 1 s (FEV₁) and Forced Vital Capacity (FVC) % predicted in crude and adjusted models, regardless of smoking status. Sitting time was negatively associated with both FEV_1%pred (β: -0.094, CI: -0.140, − 0.047) and FVC_%pred (β: -0.087, CI: -0.128, -0.045) among those who never smoked, and strength activity was positively associated with both FEV_1%pred (β: 0.272, CI: 0.048, 0.496) and FVC_%pred (β: 0.253, CI: 0.063,0.442) among those who smoked < 10 pack years, as well as with FVC_%pred among those who smoked 10 or more pack years (β: 0.309, CI: 0.064, 0.554).

Conclusions

This is the first study to assess the association of different movement behaviours with lung function among middle-aged and older adults without a respiratory disease. These findings indicate that movement behaviours are correlates of lung function, and that they may be modifiable determinants of the age-associated decline in lung function.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-5739-4) contains supplementary material, which is available to authorized users.

Sex differences in diaphragmatic fatigue: the cardiovascular response to inspiratory resistance

KEY POINTS

Diaphragmatic fatigue (DF) elicits a sympathetically mediated metaboreflex resulting in increased heart rate, blood pressure and limb vascular resistance. Women may be more resistant to DF compared to men, and therefore it was hypothesised that women would experience an attenuated inspiratory muscle metaboreflex during inspiratory pressure-threshold loading (PTL) performed to task failure. At the time of PTL task failure, the severity of DF was not different between sexes; however, inspiratory muscle endurance time was significantly longer in women than in men. For a given cumulative diaphragmatic force output, the severity of DF was less in women than in men. Women exhibited a blunted cardiovascular response to inspiratory resistance (i.e. metaboreflex) that may have implications for exercise tolerance.

ABSTRACT

Diaphragmatic fatigue (DF) elicits reflexive increases in sympathetic vasomotor outflow (i.e. metaboreflex). There is some evidence suggesting women may be more resistant to DF compared to men, and therefore may experience an attenuated inspiratory muscle metaboreflex. To this end, we sought to examine the cardiovascular response to inspiratory resistance in healthy young men (n = 9, age = 24 ± 3 years) and women (n = 9, age = 24 ± 3 years). Subjects performed isocapnic inspiratory pressure-threshold loading (PTL, 60% maximal inspiratory mouth pressure) to task failure. Diaphragmatic fatigue was assessed by measuring transdiaphragmatic twitch pressure (P_di,tw ) using cervical magnetic stimulation. Heart rate (HR) and mean arterial pressure (MAP) were measured beat-by-beat throughout PTL via photoplethysmography, and low-frequency systolic pressure (LF_SBP ; a surrogate for sympathetic vasomotor tone) calculated from arterial waveforms using power spectrum analysis. At PTL task failure, the degree of DF was similar between sexes (∼23% reduction in P_di,tw ; P = 0.33). However, time to task failure was significantly longer in women than in men (27 ± 11 vs. 16 ± 11 min, respectively; P = 0.02). Women exhibited less of an increase in HR (13 ± 8 vs. 19 ± 12 bpm; P = 0.02) and MAP (10 ± 8 vs. 14 ± 9 mmHg; P = 0.01), and significantly lower LF_SBP (23 ± 11 vs. 34 ± 8 mmHg² ; P = 0.04) during PTL compared to men. An attenuation of the inspiratory muscle metaboreflex may influence limb and respiratory muscle haemodynamics with implications for exercise performance.

Physical activity and sedentary time are related to clinically relevant health outcomes among adults with obstructive lung disease

Background

The purpose of the current study was to determine the association between sedentary time and physical activity with clinically relevant health outcomes among adults with impaired spirometry and those with or without self-reported obstructive lung disease (asthma or COPD).

Methods

Data from participants of the Canadian Longitudinal Study on Aging were used for analysis (n = 4156). Lung function was assessed using spirometry. Adults were said to have impaired spirometry if their Forced Expiratory Volume in 1 s was <5th percentile lower limit of normal (LLN). A modified version of the Physical Activity Scale for the Elderly was used to assess sitting time and physical activity levels. Healthcare use and quality of life outcomes were assessed using self report.

Results

Among those with asthma, participating in strengthening activities was associated with lower odds of reporting poor perceived health (OR = 0.65, CI: 0.53, 0.79), poor perceived mental-health (OR = 0.73, CI: 0.60, 0.88), unhealthy aging (OR = 0.68, CI: 0.56, 0.83), and reporting an emergency department visit in the past 12 months (OR = 0.76, CI: 0.60, 0.95). Among those with COPD, those who reported highest weekly sedentary time had higher odds of reporting poor perceived health (OR = 2.70, CI: 1.72, 4.24), poor perceived mental-health (OR = 1.99, CI: 1.29, 3.06), and unhealthy aging (OR = 3.04, CI: 1.96, 4.72). Among those below the LLN, sitting time (OR = 2.57, CI: 1.40, 4.72) and moderate intensity physical activity (OR = 0.23, CI: 0.09, 0.63) were associated with overnight hospital stays.

Conclusions

Higher physical activity levels and lower sedentary time may be associated with lower healthcare use and better quality of life. This research may have implications related to the use of physical activity for improving health outcomes and quality of life among adults with obstructive lung disease or impaired spirometry.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0659-8) contains supplementary material, which is available to authorized users.

Neurophysiological mechanisms of exertional dyspnoea in fibrotic interstitial lung disease

Our understanding of the mechanisms of dyspnoea in fibrotic interstitial lung disease (ILD) is incomplete. The aims of this study were two-fold: 1) to determine whether dyspnoea intensity is better predicted by neural respiratory drive (NRD) or neuromechanical uncoupling (NMU) of the respiratory system in fibrotic ILD, and 2) to examine the effect of breathing 60% oxygen on NRD, NMU and dyspnoea ratings.Fourteen patients with fibrotic ILD were included. Visit 1 comprised a familiarisation incremental cycle exercise test, Visit 2 comprised a normoxic incremental cycling test to address Aim 1, and Visits 3 and 4 consisted of constant-load cycling while breathing room air or 60% oxygen to address Aim 2. Diaphragmatic electromyography (EMGdi) was used as a surrogate of NRD. NMU was calculated as the ratio between EMGdi (%max) and tidal volume (%vital capacity).On adjusted analysis, NMU and its constituents were all significantly associated with dyspnoea ratings during incremental cycling, with EMGdi having the strongest correlation. The between-treatment change in dyspnoea ratings during constant load cycling was only correlated with change in exercise endurance time and NMU.Dyspnoea more strongly reflected the level of EMGdi than NMU in fibrotic ILD. However, the improvement in dyspnoea with 60% oxygen was better predicted by improvements in NMU.

Respiratory Mechanical and Cardiorespiratory Consequences of Cycling with Aerobars

PURPOSE

Aerobars place a cyclist in a position where the trunk is flexed forward and the elbows are close to the midline of the body. This position is known to improve cycling aerodynamics and time trial race performance compared with upright cycling positions. However, the aggressive nature of this position may have important cardiorespiratory and metabolic consequences. The purpose of this investigation was to examine the respiratory mechanical, ventilatory, metabolic, and sensory consequences of cycling while using aerobars during laboratory-based cycling.

METHODS

Eleven endurance-trained male cyclists (age, 26 ± 9 yr; V˙O2peak, 55 ± 5 mL·kg·min) were recruited. Visit 1 consisted of an incremental cycling test to determine peak power output. Visit 2 consisted of 6-min bouts of constant load cycling at 70% of peak incremental power output in the aerobar position, drop position, and upright position while grasping the brake hoods. Metabolic and ventilatory responses were measured using a commercially available metabolic cart, and respiratory pressures were measured using an esophageal catheter.

RESULTS

Cycling in the aerobar position significantly increased the work of breathing (Wb), power of breathing (Pb), minute ventilation, ventilatory equivalent for oxygen and carbon dioxide, and transdiaphragmatic pressure compared with the upright position. Increases in the Wb and Pb in the aerobars relative to the upright position were strongly correlated with the degree of thoracic restriction, measured as the shoulder-to-aerobar width ratio (Wb: r = 0.80, P = 0.01; Pb: r = 0.69, P = 0.04).

CONCLUSIONS

Aerobars significantly increase the mechanical cost of breathing and leads to greater ventilatory inefficiency compared with upright cycling. Future work is needed to optimize aerobar width to minimize the respiratory mechanical consequences while optimizing aerodynamics.

Exercise-induced quadriceps muscle fatigue in men and women: effects of arterial oxygen content and respiratory muscle work

KEY POINTS

High work of breathing and exercise-induced arterial hypoxaemia (EIAH) can decrease O₂ delivery and exacerbate exercise-induced quadriceps fatigue in healthy men. Women have a higher work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles and develop EIAH. Despite a greater reduction in men's work of breathing, the attenuation of quadriceps fatigue was similar between the sexes. The degree of EIAH was similar between sexes, and regardless of sex, those who developed the greatest hypoxaemia during exercise demonstrated the most attenuation of quadriceps fatigue. Based on our previous finding that women have a greater relative oxygen cost of breathing, women appear to be especially susceptible to work of breathing-related changes in quadriceps muscle fatigue.

ABSTRACT

Reducing the work of breathing or eliminating exercise-induced arterial hypoxaemia (EIAH) during exercise decreases the severity of quadriceps fatigue in men. Women have a greater work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles, and demonstrate EIAH, suggesting women may be especially susceptible to quadriceps fatigue. Healthy subjects (8 male, 8 female) completed three constant load exercise tests over 4 days. During the first (control) test, subjects exercised at ∼85% of maximum while arterial blood gases and work of breathing were assessed. Subsequent constant load exercise tests were iso-time and iso-work rate, but with EIAH prevented by inspiring hyperoxic gas or work of breathing reduced via a proportional assist ventilator (PAV). Quadriceps fatigue was assessed by measuring force in response to femoral nerve stimulation. For both sexes, quadriceps force was equally reduced after the control trial (-27 ± 2% baseline) and was attenuated with hyperoxia and PAV (-18 ± 1 and -17 ± 2% baseline, P < 0.01, respectively), with no sex difference. EIAH was similar between the sexes, and regardless of sex, subjects with the lowest oxyhaemoglobin saturation during the control test had the greatest quadriceps fatigue attenuation with hyperoxia (r²  = 0.79, P < 0.0001). For the PAV trial, despite reducing the work of breathing to a greater degree in men (men: 60 ± 5, women: 75 ± 6% control, P < 0.05), the attenuation of quadriceps fatigue was similar between the sexes (36 ± 4 vs. 37 ± 7%). Owing to a greater relative V̇O2 of the respiratory muscles in women, less of a change in work of breathing is needed to reduce quadriceps fatigue.

Abdominal Binding Improves Neuromuscular Efficiency of the Human Diaphragm during Exercise

We tested the hypothesis that elastic binding of the abdomen (AB) would enhance neuromuscular efficiency of the human diaphragm during exercise. Twelve healthy non-obese men aged 24.8 ± 1.7 years (mean ± SE) completed a symptom-limited constant-load cycle endurance exercise test at 85% of their peak incremental power output with diaphragmatic electromyography (EMGdi) and respiratory pressure measurements under two randomly assigned conditions: unbound control (CTRL) and AB sufficient to increase end-expiratory gastric pressure (Pga,ee) by 5-8 cmH₂O at rest. By design, AB increased Pga,ee by 6.6 ± 0.6 cmH₂O at rest. Compared to CTRL, AB significantly increased the transdiaphragmatic pressure swing-to-EMGdi ratio by 85-95% during exercise, reflecting enhanced neuromuscular efficiency of the diaphragm. By contrast, AB had no effect on spirometric parameters at rest, exercise endurance time or an effect on cardiac, metabolic, ventilatory, breathing pattern, dynamic operating lung volume, and perceptual responses during exercise. In conclusion, AB was associated with isolated and acute improvements in neuromuscular efficiency of the diaphragm during exercise in healthy men. The implications of our results are that AB may be an effective means of enhancing neuromuscular efficiency of the diaphragm in clinical populations with diaphragmatic weakness/dysfunction.

Effects of inspiratory muscle training on respiratory muscle electromyography and dyspnea during exercise in healthy men

Inspiratory muscle training (IMT) has consistently been shown to reduce exertional dyspnea in health and disease; however, the physiological mechanisms remain poorly understood. A growing body of literature suggests that dyspnea intensity can be explained largely by an awareness of increased neural respiratory drive, as measured indirectly using diaphragmatic electromyography (EMGdi). Accordingly, we sought to determine whether improvements in dyspnea following IMT can be explained by decreases in inspiratory muscle electromyography (EMG) activity. Twenty-five young, healthy, recreationally active men completed a detailed familiarization visit followed by two maximal incremental cycle exercise tests separated by 5 wk of randomly assigned pressure threshold IMT or sham control (SC) training. The IMT group (n = 12) performed 30 inspiratory efforts twice daily against a 30-repetition maximum intensity. The SC group (n = 13) performed a daily bout of 60 inspiratory efforts against 10% maximal inspiratory pressure (MIP), with no weekly adjustments. Dyspnea intensity was measured throughout exercise using the modified 0-10 Borg scale. Sternocleidomastoid and scalene EMG was measured using surface electrodes, whereas EMGdi was measured using a multipair esophageal electrode catheter. IMT significantly improved MIP (pre: -138 ± 45 vs. post: -160 ± 43 cmH₂O, P < 0.01), whereas the SC intervention did not. Dyspnea was significantly reduced at the highest equivalent work rate (pre: 7.6 ± 2.5 vs. post: 6.8 ± 2.9 Borg units, P < 0.05), but not in the SC group, with no between-group interaction effects. There were no significant differences in respiratory muscle EMG during exercise in either group. Improvements in dyspnea intensity ratings following IMT in healthy humans cannot be explained by changes in the electrical activity of the inspiratory muscles.NEW & NOTEWORTHY Exertional dyspnea intensity is thought to reflect an increased awareness of neural respiratory drive, which is measured indirectly using diaphragmatic electromyography (EMGdi). We examined the effects of inspiratory muscle training (IMT) on dyspnea, EMGdi, and EMG of accessory inspiratory muscles. IMT significantly reduced submaximal dyspnea intensity ratings but did not change EMG of any inspiratory muscles. Improvements in exertional dyspnea following IMT may be the result of nonphysiological factors or physiological adaptations unrelated to neural respiratory drive.

Quantifying the shape of maximal expiratory flow-volume curves in healthy humans and asthmatic patients

Differences in the absolute flow and volume of maximal expiratory flow-volume (MEFV) curves have been studied extensively in health and disease. However, the shapes of MEFV curves have received less attention. We questioned if the MEFV curve shape was associated with (i) expiratory flow limitation (EFL) in health and (ii) changes in bronchial caliber in asthmatics. Using the slope-ratio (SR) index, we quantified MEFV curve shape in 84 healthy subjects and 8 matched asthmatics. Healthy subjects performed a maximal exercise test to assess EFL. Those with EFL during had a greater SR (1.15 ± 0.20 vs. 0.85 ± 0.20, p<0.05) yet, there was no association between maximal oxygen consumption and SR (r=0.14, p>0.05). Asthmatics average SR was greater than the healthy subjects (1.35 ± 0.03 vs. 0.90 ± 0.11, p<0.05), but there were no differences when bronchial caliber was manipulated. In conclusion, a greater SR is related to EFL and this metric could aid in discriminating between groups known to differ in the absolute size of MEFV curves.

Oxygen cost of exercise hyperpnoea is greater in women compared with men

KEY POINTS

The oxygen cost of breathing represents a significant fraction of total oxygen uptake during intense exercise. At a given ventilation, women have a greater work of breathing compared with men, and because work is linearly related to oxygen uptake we hypothesized that their oxygen cost of breathing would also be greater. For a given ventilation, women had a greater absolute oxygen cost of breathing, and this represented a greater fraction of total oxygen uptake. Regardless of sex, those who developed expiratory flow limitation had a greater oxygen cost of breathing at maximal exercise. The greater oxygen cost of breathing in women indicates that a greater fraction of total oxygen uptake (and possibly cardiac output) is directed to the respiratory muscles, which may influence blood flow distribution during exercise.

ABSTRACT

We compared the oxygen cost of breathing (V̇O2 RM ) in healthy men and women over a wide range of exercise ventilations (V̇E). Eighteen subjects (nine women) completed 4 days of testing. First, a step-wise maximal cycle exercise test was completed for the assessment of spontaneous breathing patterns. Next, subjects were familiarized with the voluntary hyperpnoea protocol used to estimate V̇O2 RM . During the final two visits, subjects mimicked multiple times (four to six) the breathing patterns associated with five or six different exercise stages. Each trial lasted 5 min, and on-line pressure-volume and flow-volume loops were superimposed on target loops obtained during exercise to replicate the work of breathing accurately. At ∼55 l min(-1) V̇E, V̇O2 RM was significantly greater in women. At maximal ventilation, the absolute V̇O2 RM was not different (P > 0.05) between the sexes, but represented a significantly greater fraction of whole-body V̇O2 in women (13.8 ± 1.5 vs. 9.4 ± 1.1% V̇O2). During heavy exercise at 92 and 100% V̇O2max, the unit cost of V̇E was +0.7 and +1.1 ml O2 l(-1) greater in women (P < 0.05). At V̇O2max, men and women who developed expiratory flow limitation had a significantly greater V̇O2 RM than those who did not (435 ± 44 vs. 331 ± 30 ml O2  min(-1) ). In conclusion, women have a greater V̇O2 RM for a given V̇E, and this represents a greater fraction of whole-body V̇O2. The greater V̇O2 RM in women may have implications for the integrated physiological response to exercise.

Predictive models and spatial variations of vital capacity in healthy people from 6 to 84 years old in China based on geographical factors

The aim of this study was to provide a scientific basic for a unified standard of the reference value of vital capacity (VC) of healthy subjects from 6 and 84 years old in China. The normal reference value of VC was correlated to seven geographical factors, including altitude (X1), annual duration of sunshine (X2), annual mean air temperature (X3), annual mean relative humidity (X4), annual precipitation amount (X5), annual air temperature range (X6) and annual mean wind speed (X7). Predictive models were established by five different linear and nonlinear methods. The best models were selected by t-test. The geographical distribution map of VC in different age groups can be interpolated by Kriging's method using ArcGIS software. It was found that the correlation of VC and geographical factors in China was quite significant, especially for both males and females aged from 6 to 45. The best models were built for different age groups. The geographical distribution map shows the spatial variations of VC in China precisely. The VC of healthy subjects can be simulated by the best model or acquired from the geographical distribution map provided the geographical factors for that city or county of China are known.

Precise mimicking of exercise hyperpnea to investigate the oxygen cost of breathing

The oxygen cost of exercise hyperpnea (V˙(O2 RM)) has been quantified using a variety of techniques with inconsistent findings. Between-study variation relates to poor control of breathing patterns and lung mechanics. We developed a methodology allowing precise matching of exercising WOB in order to estimate V˙(O2 RM). Thirteen healthy young subjects (7 male) completed an incremental cycle exercise test, familiarization and experimental days where exercise hyperpnea was mimicked. On experimental days, feedback of exercise flow, volume and the respiratory pressures were provided while end-tidal CO2 was kept at exercise levels during each 5-min trial. Minute ventilation levels between 50 and 100% maximum were mimicked 3-5 times. The r(2) between exercise and mimic trails was 0.99 for frequency, tidal volume and minute ventilation; 0.86 for esophageal pressure swings and 0.93 for WOB. The coefficient of variation for (V˙(O2) averaged 4.3, 4.4 and 5.7% for 50, 75 and 100% ventilation trials. When WOB and other respiratory parameters are tightly controlled, the V˙(O2 RM) can be consistently estimated.

Spirometry in primary care

Canadian Thoracic Society (CTS) clinical guidelines for asthma and chronic obstructive pulmonary disease (COPD) specify that spirometry should be used to diagnose these diseases. Given the burden of asthma and COPD, most people with these diseases will be diagnosed in the primary care setting. The present CTS position statement was developed to provide guidance on key factors affecting the quality of spirometry testing in the primary care setting. The present statement may also be used to inform and guide the accreditation process for spirometry in each province. Although many of the principles discussed are equally applicable to pulmonary function laboratories and interpretation of tests by respirologists, they are held to a higher standard and are outside the scope of the present statement.