Acute sodium bicarbonate administration improves ventilatory efficiency in experimental respiratory acidosis: clinical implications.

Administering sodium bicarbonate (NaHCO3) to patients with respiratory acidosis breathing spontaneously is contraindicated because it increases carbon dioxide load and depresses pulmonary ventilation. Nonetheless, several studies have reported salutary effects of NaHCO3 in patients with respiratory acidosis but the underlying mechanism remains uncertain. Considering that such reports have been ignored, we examined the ventilatory response of unanesthetized dogs with respiratory acidosis to hypertonic NaHCO3 infusion (1 N, 5 mmol/kg) and compared it with that of animals with normal acid-base status or one of the remaining acid-base disorders. Ventilatory response to NaHCO3 infusion was evaluated by examining the ensuing change in PaCO2 and the linear regression of the PaCO2 vs. pH relationship. Strikingly, PaCO2 failed to increase and the ΔPaCO2 vs. ΔpH slope was negative in respiratory acidosis, whereas PaCO2 increased consistently and the ΔPaCO2 vs. ΔpH slope was positive in the remaining study groups. These results cannot be explained by differences in buffering-induced decomposition of infused bicarbonate or baseline levels of blood pH, PaCO2, and pulmonary ventilation. We propose that NaHCO3 infusion improved the ventilatory efficiency of animals with respiratory acidosis, i.e., it decreased their ratio of total pulmonary ventilation to carbon dioxide excretion (VE/VCO2). Such exclusive effect of NaHCO3 infusion in animals with respiratory acidosis might emanate from baseline increased VD/VT (dead space/tidal volume) caused by bronchoconstriction and likely reduced pulmonary blood flow, defects that are reversed by alkali infusion. Our observations might explain the beneficial effects of NaHCO3 reported in patients with acute respiratory acidosis.

The prognostic role of cardiopulmonary exercise testing in obesity.

AIM: Poor cardiorespiratory fitness has been suggested to increase the risk of chronic diseases in obesity. We investigated the ability of key variables from cardiopulmonary exercise testing (CPET) to predict all-cause mortality in an obese cohort. METHODS: The sample included 469 participants of both sexes (mean age 40 ± 13 years) who underwent a CPET for clinical reasons between 1 March 2009 and 1 December 2023. All-cause mortality was the prognostic endpoint. A receiver operating characteristic analysis was performed to establish optimal cut-points for CPET variables. Kaplan-Meier and Cox regression analyses were used to determine the association between CPET variables and all-cause mortality. RESULTS: There were 46 deaths during a mean follow-up period of 69 ± 48 months, resulting in an annual mortality rate of 2%. Despite the sample being made up of mostly women (70%), there were more deaths in men (18 vs. 6%, p < 0.001).The optimal thresholds for discrimination of survival were as follows: (a) peak oxygen uptake (pVO2) ≤16 mL/kg/min; (b) minute ventilation/carbon dioxide production (VE/VCO2) slope ≥31; (c) ventilatory power ≤5.8 mmHg; and (d) circulatory power ≤2980 mmHg/mL O2/min. Kaplan-Meier survival plots revealed a significant positive association between lower pVO2, circulatory power and ventilatory power values and survival (log-rank, p < 0.001) and higher mortality for men than women. Adjusted Cox regression models showed that a pVO2 ≤16 mL/kg/min had a 20-fold higher risk of mortality when compared with >16 mL/kg/min. CONCLUSION: Given the strong association of VO2, ventilatory efficiency, circulatory and ventilatory power with all-cause mortality, our findings support the notion that poorer cardiorespiratory fitness is associated with a poor prognosis in patients with obesity.

Ventilatory efficiency as a prognostic factor for postoperative complications in patients undergoing elective major surgery: a systematic review.

BACKGROUND: Major surgery is associated with high complication rates. Several risk scores exist to assess individual patient risk before surgery but have limited precision. Novel prognostic factors can be included as additional building blocks in existing prediction models. A candidate prognostic factor, measured by cardiopulmonary exercise testing, is ventilatory efficiency (VE/VCO2). The aim of this systematic review was to summarise evidence regarding VE/VCO2 as a prognostic factor for postoperative complications in patients undergoing major surgery. METHODS: A medical library specialist developed the search strategy. No database-provided limits, considering study types, languages, publication years, or any other formal criteria were applied to any of the sources. Two reviewers assessed eligibility of each record and rated risk of bias in included studies. RESULTS: From 10,082 screened records, 65 studies were identified as eligible. We extracted adjusted associations from 32 studies and unadjusted from 33 studies. Risk of bias was a concern in the domains 'study confounding' and 'statistical analysis'. VE/VCO2 was reported as a prognostic factor for short-term complications after thoracic and abdominal surgery. VE/VCO2 was also reported as a prognostic factor for mid- to long-term mortality. Data-driven covariable selection was applied in 31 studies. Eighteen studies excluded VE/VCO2 from the final multivariable regression owing to data-driven model-building approaches. CONCLUSIONS: This systematic review identifies VE/VCO2 as a predictor for short-term complications after thoracic and abdominal surgery. However, the available data do not allow conclusions about clinical decision-making. Future studies should select covariables for adjustment a priori based on external knowledge. SYSTEMATIC REVIEW PROTOCOL: PROSPERO (CRD42022369944).

Effects of a telerehabilitation program and detraining on cardiorespiratory fitness in patients with post-COVID-19 sequelae: A randomized controlled trial.

BACKGROUND: This study aimed to evaluate the effects of a 15-week telerehabilitation program and a detraining period on cardiorespiratory fitness and mechanical efficiency in patients with post-COVID-19 sequelae. METHODS: 131 patients with post-COVID-19 sequelae were randomly assigned to one of two groups: patients who carried out the supervised telerehabilitation program (TRG, n = 66) and a control group (CG, n = 65). An incremental cardiopulmonary exercise testing (CPET) was performed on cycle ergometer to compare cardioventilatory responses between experimental groups. RESULTS: A significant increase in the CPET duration, peak power output, and mechanical efficiency was observed in TRG compared to CG after the telerehabilitation program (p ≤ 0.001). A significant increase in the CPET duration, peak power output, and mechanical efficiency was verified at 3 months compared to the pretest and after detraining in TRG (p < 0.001). A significant increase in peak oxygen uptake (V̇O2peak ) was identified after the intervention and in the detraining period compared to the pretest in both experimental groups (p < 0.001). A higher ventilatory efficiency was observed after the telerehabilitation program (p = 0.021) than in pretest only in TRG. CONCLUSIONS: A 15-week supervised home telerehabilitation program improved exercise capacity, power output, and mechanical efficiency in TRG compared to a CG. The telerehabilitation program was not more effective in improving V̇O2peak than the activities of the CG. However, ventilatory efficiency was improved only after the telerehabilitation program. The reported results after the detraining period highlight the need to maintain the rehabilitation program over time.

Hospital and intensive care unit stay associated with body mass index affect cardiorespiratory fitness in patients with COVID-19.

BACKGROUND: The effects of coronavirus disease 2019 (COVID-19) on the cardiorespiratory fitness of hospitalized and obese patients are of utmost relevance. This study aimed to analyze how hospital and intensive care unit (ICU) stay together with body mass index affect cardiorespiratory fitness in patients with COVID-19. METHODS: 251 participants (males, n = 118; females, n = 133) were assigned to four groups: non-hospitalized COVID-19 patients (n = 65, age: 45.3 years), hospitalized COVID-19 patients (n = 63, age: 57.6 years), COVID-19 patients admitted to the ICU (n = 61, age: 56.9 years), and control group (n = 62, age: 49.8 years). An incremental cardiopulmonary exercise test was performed between 3 and 6 weeks after medical discharge from hospital. RESULTS: Higher peak oxygen uptake (VO2peak), ventilatory efficiency and power output were found in ICU patients with normal weight (NW) than in overweight (OW) (Mean difference: 0.1 L·min-1, -5.5, 29.0 W, respectively) and obese (OB) ICU patients (Mean difference: 0.1 L·min-1, -5.0, 26.2 W, respectively) (p < .05). In NW, OW and OB participants, higher VO2peak and power output were observed in control group compared with non-hospitalized (Mean difference: NW: 0.2 L·min-1, 83.3 W; OW: 0.2 L·min-1, 60.0 W; OB: 0.2 L·min-1, 70.9 W, respectively), hospitalized (Mean difference: NW: 0.2 L·min-1, 72.9 W; OW: 0.1 L·min-1, 58.3 W; OB: 0.2 L•min-1, 91.1 W, respectively) and ICU patients (Mean difference: NW: 0.1 L·min-1, 70.9 W; OW: 0.2 L·min-1, 91.1 W; OB: 0.3 L·min-1; 65.0 W, respectively) (p < .05). CONCLUSIONS: The degree of severity of COVID-19, especially identified by hospitalization and ICU stay, together with obesity and overweight were key factors in reducing cardiorespiratory fitness in patients with COVID-19.

Impaired Cardiorespiratory Fitness of Elite Athletes after Asymptomatic or Mild SARS-CoV-2 Infection.

Background and Objectives: The aim of the study was to evaluate the health status of professional athletes after recovering from COVID-19 and the impact that SARS-CoV-2 had on their overall cardiorespiratory fitness, which was done by conducting cardiopulmonary exercise testing (CPET). Materials and Methods: A total of twenty-seven professional basketball players (Euroleague Basketball and the ABA League) participated in the study. CPET was performed before (as part of their regular preparticipation exam, during the pre-season period), as well as after SARS-CoV-2 infection (after two weeks of home isolation, during the competitive part of the season). CPET was performed on a treadmill, while cardiovascular, respiratory, and metabolic functions were evaluated by using a breath-by-breath analysis technique (Quark CPET system manufactured by Cosmed, Rome, Italy). Results: Maximal oxygen consumption and aerobic efficiency were significantly reduced after SARS-CoV-2 infection (p = 0.000). An obvious decrease in oxygen pulse was observed during CPET after recovering from COVID-19 (p = 0.001), as was deterioration of ventilatory efficiency. Internal respiration was the most negatively affected. An early transition from aerobic to anaerobic mechanisms of creating energy for work and intensive metabolic fatigue were obvious after SARS-CoV-2 infection. Conclusions: Although it was believed that SARS-CoV-2 only affects the cardiopulmonary status of the elderly population and people with associated comorbidities, it is clear from this research that professional athletes can also be at certain risk. Even though no pathological cardiovascular and respiratory changes were found in athletes after COVID-19, results showed significantly decreased cardiorespiratory fitness, with an emphasis on internal respiration.

Effects of an asymmetrical high flow nasal cannula interface in hypoxemic patients.

BACKGROUND: Optimal noninvasive respiratory support for patients with hypoxemic respiratory failure should minimize work of breathing without increasing the transpulmonary pressure. Recently, an asymmetrical high flow nasal cannula (HFNC) interface (Duet, Fisher & Paykel Healthcare Ltd), in which the caliber of each nasal prong is different, was approved for clinical use. This system might reduce work of breathing by lowering minute ventilation and improving respiratory mechanics. METHODS: We enrolled 10 patients ≥ 18 years of age who were admitted to the Ospedale Maggiore Policlinico ICU in Milan, Italy, and had a PaO2/FiO2 < 300 mmHg during HFNC support with a conventional cannula. We investigated whether the asymmetrical interface, compared to a conventional high flow nasal cannula, reduces minute ventilation and work of breathing. Each patient underwent support with the asymmetrical interface and the conventional interface, applied in a randomized sequence. Each interface was provided at a flow rate of 40 l/min followed by 60 l/min. Patients were continuously monitored with esophageal manometry and electrical impedance tomography. RESULTS: Application of the asymmetrical interface resulted in a -13.5 [-19.4 to (-4.5)] % change in minute ventilation at a flow rate of 40 l/min, p = 0.006 and a -19.6 [-28.0 to (-7.5)] % change at 60 l/min, p = 0.002, that occurred despite no change in PaCO2 (35 [33-42] versus 35 [33-43] mmHg at 40 l/min and 35 [32-41] versus 36 [32-43] mmHg at 60 l/min). Correspondingly, the asymmetrical interface lowered the inspiratory esophageal pressure-time product from 163 [118-210] to 140 [84-159] (cmH2O*s)/min at a flow rate of 40 l/min, p = 0.02 and from 142 [123-178] to 117 [90-137] (cmH2O*s)/min at a flow rate of 60 l/min, p = 0.04. The asymmetrical cannula did not have any impact on oxygenation, the dorsal fraction of ventilation, dynamic lung compliance, or end-expiratory lung impedance, suggesting no major effect on PEEP, lung mechanics, or alveolar recruitment. CONCLUSIONS: An asymmetrical HFNC interface reduces minute ventilation and work of breathing in patients with mild-to-moderate hypoxemic respiratory failure supported with a conventional interface. This appears to be primarily driven by increased ventilatory efficiency due to enhanced CO2 clearance from the upper airway.

Impaired Ventilatory Efficiency, Dyspnea, and Exercise Intolerance in Chronic Obstructive Pulmonary Disease: Results from the CanCOLD Study.

Rationale: Impaired exercise ventilatory efficiency (high ventilatory requirements for CO2 [[Formula: see text]e/[Formula: see text]co2]) provides an indication of pulmonary gas exchange abnormalities in chronic obstructive pulmonary disease (COPD). Objectives: To determine 1) the association between high [Formula: see text]e/[Formula: see text]co2 and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and 2) its prevalence in a large population-based cohort. Methods: Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing, and chest computed tomography. Impaired exercise ventilatory efficiency was defined by a nadir [Formula: see text]e/[Formula: see text]co2 above the upper limit of normal (ULN), using population-based normative values. Measurements and Main Results: Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 COPD, and 200 with GOLD 2-4 COPD. Participants with [Formula: see text]e/[Formula: see text]co2 above the ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale ⩾ 2; odds ratio [5-95% confidence intervals], 1.77 [1.31 to 2.39]) and abnormally low peak [Formula: see text]o2 ([Formula: see text]o2peak below the lower limit of normal; odds ratio, 4.58 [3.06 to 6.86]). The Kco had a stronger correlation with nadir [Formula: see text]e/[Formula: see text]co2 (r = -0.38; P < 0.001) than other relevant lung function and computed tomography metrics. The prevalence of [Formula: see text]e/[Formula: see text]co2 above the ULN was 24% in COPD (similar in GOLD 1 and 2 through 4), which was greater than in never-smokers (13%) and ever-smokers (12%). Conclusions: [Formula: see text]e/[Formula: see text]co2 above the ULN was associated with greater dyspnea and low [Formula: see text]o2peak and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.

Left Atrial Myopathy is Associated With Exercise Incapacity and Ventilatory Inefficiency in Hypertrophic Cardiomyopathy.

BACKGROUND: Left atrial (LA) myopathy is an established component of hypertrophic cardiomyopathy (HCM); however, the data about its association with exercise incapacity or ventilatory inefficiency that may be seen in HCM patients are limited. This study aimed to explore the association between LA myopathy, evaluated by echocardiography LA strain, and exercise capacity and ventilatory efficiency, evaluated by cardiopulmonary exercise testing (CPET), in HCM patients. METHODS: This study included 241 consecutive HCM patients (aged 51.2±15.7 years 67.2% male) in sinus rhythm who underwent CPET and transthoracic echocardiography at the same visit. Exercise incapacity (maximal/predicted oxygen consumption [%peakVO2] <80%) and ventilatory inefficiency (ventilation/carbon dioxide output [VE/VCO2] slope >34) were assessed by CPET. Left atrial myopathy was examined by speckle-tracking myocardial deformation parameters: LA reservoir, conduit and booster strain. RESULTS: All three LA strain values were univariate predictors of exercise capacity and ventilatory efficiency. Among them, LA reservoir strain had the higher r correlation coefficient for predicting both %peakVO2 and VE/VCO2 slope. Left atrial reservoir strain, presence of angina and family history of HCM were independent predictors of exercise capacity. Left atrial reservoir strain, male gender and non-sustained ventricular tachycardia were independent predictors of ventilatory efficiency. Left atrial reservoir strain was a significant predictor of %peakVO2<80% with an optimal cut-off value of 27% (sensitivity 87% and specificity 31%) and VE/VCO2>34 with an optimal cut-off value of 18% (sensitivity 71% and specificity 83%). CONCLUSION: Left atrial myopathy, as reflected by the LA strain values, was associated with exercise incapacity and ventilatory inefficiency in HCM individuals. Left atrial reservoir strain was the only common independent predictor of %peakVO2 and VE/VCO2 slope.

Reduced Forced Vital Capacity and the Number of Chest Wall Surgeries are Associated with Decreased Exercise Capacity in Children with Congenital Heart Disease.

Low forced vital capacity (FVC) is associated with decreased exercise capacity in CHD. Multiple prior cardiac surgeries have been associated with low FVC. We seek to understand the relationship between low FVC, number of cardiac surgeries and cardiopulmonary response leading to decreased exercise capacity. Retrospective chart review of demographics, surgical history and exercise testing including spirometry was performed in patients with CHD. Single ventricle patients were excluded. Low FVC was defined as a Z-score below the lower limit of normal. Exercise parameters were expressed as a percent of predicted. There were 93 patients with 2 ventricle CHD identified over 34 months with cardiopulmonary exercise testing. The FVC Z-score directly correlated with peak V̇O2% (R2 = 0.07, p < 0.05), and the O2 pulse% (R2 = 0.25, p < 0.0001). The VE/VCO2 was inversely related to the FVC Z-score (R2 = 0.11, p < 0.01). Patients with minimum three prior surgeries had decreased peak VO2% (63.7 vs. 72.8, p < 0.05), decreased peak O2 pulse% (80.8 vs. 97.9, p < 0.01) and a lower mean FVC Z-score (- 1.9 vs - 0.38, p < 0.01). The FVC Z-score and number of surgeries both predicted peak V̇O2% in multivariate analysis. Our study demonstrated that low FVC and three or more prior cardiac surgeries were associated with lower exercise capacity and lower stroke volume response. More cardiac surgeries were also associated with low FVC. However, both low FVC and the number of surgeries were independent predictors of exercise capacity.

Impact of closed loop stimulation on prognostic cardiopulmonary variables in patients with chronic heart failure and severe chronotropic incompetence: a pilot, randomized, crossover study.

AIMS: Clinical effects of rate-adaptive pacing in heart failure patients with chronotropic incompetence (CI) undergoing cardiac resynchronization therapy (CRT) remain unclear. Closed loop stimulation (CLS) is a new rate-adaptive sensor in CRT devices. We evaluated the effectiveness of CLS in CRT patients with severe CI, focusing primarily on key prognostic variables assessed by cardiopulmonary exercise (CPX) testing. METHODS AND RESULTS: In the randomized, crossover, multicentre BIO|CREATE study, 20 CRT patients with severe CI and NYHA Class II/III (60%/40%) were randomized 1:1 to the sequence DDD-40 mode to DDD-CLS mode, or the sequence DDD-CLS mode to DDD-40 mode (1 month in each mode). Patients underwent symptom-limited treadmill-based CPX test in each mode. An improvement (decrease) of the ventilatory efficiency (VE) slope of ≥5% during CLS was regarded as positive response to CLS. Seventeen patients with full data sets had a mean intra-individual VE slope change of -1.8 ± 3.0 (-4.1%) with CLS (P = 0.23). Eight patients (47%) were CLS responders, with a -6.1 ± 2.7 (-16.4%) slope change (P = 0.029). Compared to non-responders, CLS responders had a higher left ventricular (LV) ejection fraction (46 ± 3 vs. 36 ± 9%; P = 0.0070), smaller end-diastolic LV volume (121 ± 34 vs. 181 ± 41 mL; P = 0.0085), smaller end-systolic LV volume (65 ± 23 vs. 114 ± 39 mL; P = 0.0076), and were predominantly in NYHA Class II (P = 0.0498). CONCLUSION: The data of the present pilot study are compatible with the notion that CLS activation may improve VE slope in CRT patients with severe CI and less advanced heart failure. Further research is needed to determine the long-term clinical outcomes of CLS.

Examination of the Relationship and Dissociation Between Minimum Minute Ventilation/Carbon Dioxide Production and Minute Ventilation vs. Carbon Dioxide Production Slope.

BACKGROUND: Minute ventilation/carbon dioxide production (V̇E/V̇CO2) is a variable of cardiopulmonary exercise testing (CPET), which is evaluated by arterial CO2pressure and ventilation-perfusion mismatch via invasive methods. This study evaluated substitute non-invasively obtained variables for minimum V̇E/V̇CO2(Min) and V̇E vs. V̇CO2slope (Slope) and the relationship between Min and Slope.Methods and Results:This study enrolled 1,052 patients with heart disease who underwent CPET and impedance cardiography simultaneously. At first, the correlations between the end-tidal CO2pressure (PETCO2), tidal volume/respiratory rate (TV/RR) ratio, V̇E and V̇CO2Y-intercept (Y-int), and cardiac index (CI) and the Min and Slope were investigated. Second, the correlation between Min and Slope was investigated. PETCO2showed the largest correlation value among the 4 variables. These 4 variables could reveal 84.2% and 81.9% of Min and Slope, respectively. Although Slope correlated with Min (R=0.868) and predicted 78.9% of Min, considering these 4 variables, Slope+Y-int was more strongly correlated with Min (R=0.940); the Slope+Y-int revealed 90.6% of the Min relationship in the multiple regression analysis. CONCLUSIONS: Over 80% of the Min and Slope values were revealed with the above-mentioned 4 variables collected non-invasively. The formula, Min∝Slope+Y-int, can reveal >90% of the Min/Slope relationships, and the Y-int may be a crucial factor to clarify the relationship between Min and Slope.

Reduced exercise tolerance in mild chronic obstructive pulmonary disease: The contribution of combined abnormalities of diffusing capacity for carbon monoxide and ventilatory efficiency.

BACKGROUND AND OBJECTIVE: The combination of both reduced resting diffusing capacity of the lung for carbon monoxide (DLCO ) and ventilatory efficiency (increased ventilatory requirement for CO2 clearance [V˙E /V˙CO2 ]) has been linked to exertional dyspnoea and exercise intolerance in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are poorly understood. The current study examined if low resting DLCO and higher exercise ventilatory requirements were associated with earlier critical dynamic mechanical constraints, dyspnoea and exercise limitation in patients with mild COPD. METHODS: In this retrospective analysis, we compared V˙E /V˙CO2 , dynamic inspiratory reserve volume (IRV), dyspnoea and exercise capacity in groups of patients with Global Initiative for Chronic Obstructive Lung Disease stage 1 COPD with (1) a resting DLCO at or greater than the lower limit of normal (≥LLN; Global Lung Function Initiative reference equations [n = 44]) or (2) below the

Exercise testing in patients with cystic fibrosis-importance of ventilatory parameters.

BACKGROUND: Ventilatory parameters obtained during exercise predict survival in several chronic diseases; however, long-term changes in exercise ventilatory parameters in patients with cystic fibrosis (CF) have yet to be examined and potential differences between sexes in CF are unknown. PURPOSE: We sought to examine the change in exercise ventilatory parameters over time in patients with CF and determine if the change is different between sexes. METHODS: Exercise capacity (VO2 peak) and exercise ventilatory parameters (VE/VO2 peak, VE/VCO2 peak, and VE/VCO2 slope) were determined from a maximal cardio-pulmonary test on a cycle ergometer on two visits separated by 39 ± 16 months in 20 patients with CF (10 female, 10 male). RESULTS: No differences between sexes were observed at visit 1 (all p > 0.05). Overall, exercise ventilatory parameters significantly (p < 0.05) deteriorated between visits, with no change (p > 0.05) in VO2 peak. Moreover, compared to males, female patients exhibited greater deteriorations in VE/VO2 peak (p = 0.001), VE/VCO2 peak (p = 0.002), and VE/VCO2 slope (p = 0.016) between visits. CONCLUSIONS: These data in patients with CF indicate that exercise ventilatory parameters decline over time despite no change in VO2 peak, and female patients exhibit a more rapid deterioration compared to males.

Inspiratory Constraints and Ventilatory Inefficiency Are Superior to Breathing Reserve in the Assessment of Exertional Dyspnea in COPD.

Combining measurements of impaired lung mechanics (inspiratory constraints) with an index of increased respiratory stimuli to metabolic demand (poor ventilatory efficiency) might enhance the ability of cardiopulmonary exercise testing (CPET) in exposing a mechanistic role for ventilation on exertional dyspnea in COPD. In addition to the standard approach to suggest ventilatory limitation to exercise - a low breathing reserve (1-(peak ventilation (V̇E)/maximal voluntary ventilation × 100 < 20%) - we assessed the presence of critical inspiratory constraints (end-inspiratory lung volume (EILV)/total lung capacity (TLC) ≥ 0.9) and ventilatory inefficiency (V̇E/CO2 output (V̇CO2) nadir > 34) in 288 patients with mild to very severe COPD (FEV1 ranging from 18 to 121% predicted). We found that ∼50% of the patients with preserved breathing reserve developed critical inspiratory constraints. A low breathing reserve was weakly related to a lower peak O2 uptake (V̇O2) and/or a higher dyspnea burden; for instance, patients with low breathing reserve but without critical inspiratory constraints had similar dyspnea and peak V̇O2 than those with preserved breathing reserve (p > 0.05). In contrast, critical inspiratory constraints and ventilatory inefficiency were strongly associated with a negative outcome (likelihood ratio = 42.3 and 47.7, respectively; p < 0.001). A multiple logistic regression analysis revealed that only EILV/TLC ≥ 0.9 and V̇E/V̇CO2 nadir >34 predicted a severely reduced peak V̇O2 due to a high dyspnea burden (p < 0.001). Measurements of dynamic mechanical constraints and ventilatory inefficiency during incremental CPET are key to determine the impact of COPD on dyspnea and exercise tolerance across the spectrum of disease severity.

Oxygen uptake efficiency slope during exercise in adults with Down syndrome.

BACKGROUND: Persons with Down syndrome (DS) have low aerobic exercise capacity. The present authors sought to compare the oxygen uptake efficiency slope (OUES) between adults with and without DS performing graded exercise testing (GXT) and to investigate its relationship with peak oxygen uptake (VO2peak ) in both groups of participants. METHOD: Twenty-three participants with DS and 24 non-disabled controls performed GXT with VO2 measurements. OUES was calculated from data of the first 75%, 90% and 100% GXT time. Multiple linear regression analyses were computed to explore associations between the independent (OUES and DS) and the dependent variables (VO2peak ). RESULTS: VO2peak , GXT time and OUES were lower in participants with DS (p < .05). OUES and DS explained 69.3% of the variance in VO2peak . CONCLUSIONS: Our findings show that OUES values are lower in persons with DS. Additionally, it was shown that OUES has predictive value for VO2peak estimations in DS.

Comparison of two instructions for deep breathing exercise: non-specific and diaphragmatic breathing.

[Purpose] Breathing exercises are frequently prescribed to reduce pulmonary complications after abdominal and thoracic surgery. Appropriate instructions ensuring the integrity of the self-exercise are important. This study compared the effects of two instructions, focusing on non-specific breathing (NB) and diaphragmatic breathing (DB) patterns, respectively, on the ventilatory efficiency and work of breathing. [Subjects and Methods] The participants were healthy men (n=15) and women (n=15). Ventilatory parameters, heart rate, and autonomic nervous system activity were measured during natural and deep breathing phases performed under the two instructions (NB and DB), with the deep breathing phase following the natural breathing phase. [Results] For both men and women, ventilatory efficiency was increased during deep breathing relative to natural breathing, regardless of the instructions. In women, the increment in ventilatory efficiency during deep breathing was greater under NB compared to that under DB. The work of breathing decreased during deep breathing in women under both instructions, but did not change in men under DB. [Conclusion] Under NB instruction, deep breathing elicits similar or greater effects on ventilatory efficiency compared to that under DB instruction.

Comparative determination of ventilatory efficiency from constant load and incremental exercise testing.

The analysis of the relationships between minute ventilation (VE) to CO2 output (VCO2), referred to as ventilatory efficiency, in response to incremental exercise testing, is considered a useful index for assessing the presence and severity of cardiopulmonary and metabolic diseases. The effects of constant load exercise testing performed at work intensity associated with anaerobic threshold (AT) and respiratory compensation points (RCP), on the accurate measurements of ventilatory efficiency are not well known. The aim of this present study was to investigate the reliability of the VE/VCO2 ratio obtained from constant load exercise tests performed with two important metabolic rates (at the AT and RCP) and compare it to that of those of incremental exercise tests. A total of 20 young male (20.8±0.4 yr) subjects initially performed an incremental exercise test and then two constant load exercise tests, on different days. Respiratory and pulmonary gas exchange variables were used to estimate AT and RCP. A paired t-test was used to analyse data. AT and RCP (average) occurred the at 60% and at 71% of peak O2 uptake, respectively. The lowest VE/VCO2 ratio recorded within the first 2 minutes of constant load exercise tests with a work load of AT (26.4±0.3) and RCP (26.7±0.5) was not statistically different from the lowest ratio obtained from the incremental exercise tests (26.0±0.7). In the constant load exercise test, despite the different metabolic rates, the increase in ventilation corresponded closely with the increase in CO2 production, reflecting an optimal ventilation and perfusion ratio. Clinicians should consider the constant load exercise test work load associated with AT and RCP as it provides a meaningful lowest value for ventilatory efficiency.

Correlation between peripheral endothelial function, oxygen consumption and ventilatory efficiency in heart transplantation recipients.

BACKGROUND: Endothelial dysfunction and peak oxygen uptake (VO2peak) are also predictors of increased risk of cardiovascular events in heart transplantation (HTx) recipients. The preservation of endothelial function may contribute to exercise tolerance. OBJECTIVE: To investigate the correlation between peripheral endothelial function and exercise tolerance through VO2peak and ventilation to carbon dioxide production slope (VE / VCO2 slope) in HTx recipients. METHODS: A pilot cross-sectional study was conducted with adult individuals aged 18-65 years, HTx ≥ six months after surgery, who had a stable medical condition and no changes over the last three months of immunosuppressive treatment. The patients underwent an assessment of endothelial function through PAT (EndoPAT-2000®) and performed a cardiopulmonary exercise test (CPET). RESULTS: A total of 41% of the studied population presented endothelial dysfunction. The individuals were divided into two groups: the endothelial dysfunction (GED; n=9) group and the normal endothelial function (GNEF; n=13) group according to the logarithm of the reactive hyperemia index (LnRHI). There was a positive and moderate correlation between the LnRHI and VO2 peak (r=0.659, p=0.013) and a negative and moderate correlation between the LnRHI and VE/VCO2 slope (r= -0.686, p= 0.009) in the GNEF. However, no significant correlations were found in the GED. CONCLUSION: The results showed that the preservation of peripheral endothelial function is significantly correlated with an increase in exercise tolerance in individuals after HTx. These findings bring important considerations for cardiovascular risk prevention and emphasize that therapeutic strategies with physical training programs must be implemented early.

Peak oxygen uptake in combination with ventilatory efficiency improve risk stratification in major abdominal surgery.

This pilot study aimed to evaluate if peak VO2 and ventilatory efficiency in combination would improve preoperative risk stratification beyond only relying on peak VO2 . This was a single-center retrospective cohort study including all patients who underwent cardiopulmonary exercise testing (CPET) as part of preoperative risk evaluation before major upper abdominal surgery during years 2008-2021. The primary outcome was any major cardiopulmonary complication during hospitalization. Forty-nine patients had a preoperative CPET before decision to pursue to surgery (cancer in esophagus [n = 18], stomach [6], pancreas [16], or liver [9]). Twenty-five were selected for operation. Patients who suffered any major cardiopulmonary complication had lower ventilatory efficiency (i.e., higher VE/VCO2 slope, 37.3 vs. 29.7, p = 0.031) compared to those without complications. In patients with a low aerobic capacity (i.e., peak VO2 < 20 mL/kg/min) and a VE/VCO2 slope ≥ 39, 80% developed a major cardiopulmonary complication. In this pilot study of patients with preoperative CPET before major upper abdominal surgery, patients who experienced a major cardiopulmonary complication had significantly lower ventilatory efficiency compared to those who did not. A low aerobic capacity in combination with low ventilatory efficiency was associated with a very high risk (80%) of having a major cardiopulmonary complication.