Ventilatory Equivalents For O2 Research Articles

Hemodynamic and cardiorespiratory responses to submaximal and maximal exercise in adults with Down syndrome.

Introduction: The genetic disorder causing Down syndrome (DS) affects the cardiorespiratory and hemodynamic parameters. When exercising, sufficient blood flow is necessary for active muscles. Cardiac output (Q) must be proportional to the peripheral requirements. In case the stroke volume (SV) is lower, the heart rate (HR) will increase further in order to maintain an adequate blood flow in the active territories (HR compensatory response). People with DS have a lower HR response to maximal exercise. Nevertheless, the response of the hemodynamic and cardiorespiratory parameters during the submaximal phases of maximal exercise was not well studied. Objective: to evaluate cardiorespiratory and hemodynamic parameters 1) during submaximal and 2) maximal metabolic treadmill test in individuals with and without DS. Methods: fifteen adults with DS (age = 27.33 ± 4.98 years old; n = 12 males/3 females) and 15 adults without disabilities, matched by age and sex, participated in this cross-sectional study. Peak and submaximal cardiorespiratory and hemodynamic parameters were measured during a treadmill test. Linear mixed-effects models were used to analyse interactions between the variables. Post-hoc analyses were employed to assess within and between-group differences. Results: The DS group showed lower peak values for ventilation (VE), respiratory exchange ratio (RER), tidal volume (VT), ventilatory equivalent for O2 (VEqO2), end-tidal partial pressure for O2 (PETO2), O2 uptake (VO2) and CO2 production (all p < 0 .050), Q, SV, systolic and diastolic blood pressure (SBP, DBP), and HR (all p < 0 .050). There were group-by-time interactions (all p < 0 .050) for all ventilatory submaximal values. Significant group and time differences were observed for VE; RER; respiratory rate (RR); VEqO2; PETO2; VO2, and VT (all p < 0 .050). There were also group-by-time interactions (all p < 0 .050) and group and time differences for SBP, mean arterial blood pressure (MAP) and HR (all p < 0.010). Conclusion: During submaximal exercise, we verified a compensatory response of HR, and greater VE and VO2 in the individuals with DS. In addition, we were able to observe that the DS group had a reduced SBP and MAP response to submaximal exercise. On the other hand, we found that adults with DS have lower peak hemodynamic and cardiorespiratory values, and a lower cardiac reserve. Further research is warranted to investigate the effects of these results on the general health of adults with DS and the impact of long-term exercise programs on these parameters.

First Evidence of Cardiopulmonary Adaptation to Physical Effort in Transgender Women After Long-Term Hormone Therapy: A Cross-Sectional Study

Introduction: Cisgender men (CM) and women (CM) present different acute cardiopulmonary (CP) adaptation to effort. The smallest arteriovenous difference in oxygen (O2) and cardiac output (CO) in CW determine a lower maximum VO2 (VO2max) than CM. CP capacity adaptation to effort of TW undergoing gender-affirming hormone therapy (GAHT) was not yet reported. Objective: To evaluate CP capacity of TW in long-term GAHT. Methods: A cross-sectional study was carried out with 8 TW (average age of 34.0 ±4.8 yo), 8 CM and 8 CW matched on age, body mass index and activity level. All TW were non-gonadectomized subjects and were in estrogen [transdermal estradiol (n=2), oral estradiol (n=3) and conjugated estrogen (n=3)], plus cyproterone acetate (n=8) therapy in an average time of 15.6 ±8.7 years. Body composition was assessed by InBody 720, and participants’ level of physical activity by IPAQ (International Physical Activity Questionnaire) short form. Total testosterone (ng/dL) levels of TW, CW and CM were 83,5 (12,0;637,0), 20,5 (12,0;41,0) and 480,5 (264,0;843,0), respectively. Hemoglobin levels of TW, CW and CM were 14,2 (13,5;14,9), 14,35 (12,8;14,7) and 15,35 (14,0;18,2), respectively. Everyone performed a CP exercise testing on a treadmill with an incremental effort. Results: Mean VO2max (L/min) in the group of TW was 2648±575.5, of CW 2128±394.0 and of CM 3235±554.0 (TWvsCW p=0.1311; TWvsCM p=0.0806; CWvsCM p=0.009). Free fat mass (FFM) of TW was 55.56±6.88 kg, CW 38.98±4,09 kg, and CM 64,98±6,29 kg (TWvsCW p<0,0001; TWvsCM p=0,024; CWvsCM p<0,0001). Analysis of VO2max/FFM (L/min/kg), TW′s rate was 46.6±6.2, CW′s was 54.6±8.4 and CM′s was 49.4±6.1 (TWvsCW p=0.0770;TWvsCM p=0.6942; CWvsCM p=0.3185). O2 pulse, VE/VO2 (ventilatory equivalents for O2) and VE/VCO2 (ventilatory equivalents for carbon dioxide) were similar in all groups. There was high correlation of O2pulse and free fat mass/height2 (FFM/Hgt2) of TW (r 0,925;p 0,008), not observed in CW (r 0.614;p0.105) or CM (r 0.737; p 0.037).% predicted Heart Rate (%HR) at effort was higher in TW (104) than in CW (95.8)(p=0.0221) and CM (100.3)(p=0.3334). Discussion: Aerobic capacity of TW was intermediate between CM and CW. Regards VO2 / FFM ratio, TW had a lower index than other groups. Since changes in pulmonary O2 diffusion, CO and blood circulation were ruled out as causing such data, it could be related to O2 uptake drops by the muscle. Increased sympathetic activity and %HR in TW and high correlation of O2pulse and FFM/Hgt2 make up compatible framework with exacerbation of ergoreflex. Conclusion: Our results support the finding of a VO2max similar between TW undergoing long-term GAHT and CW groups, despite the previous expose of TWs to testosterone during puberty. We hypothesized the presence of an increased ergoreflex sensitivity in TW individuals. These preliminary results should be confirmed by increasing the number of individuals studied.

The effect of minimally invasive surgical aortic valve replacement on postoperative pulmonary and skeletal muscle function.

What is the central question of this study? How does surgical aortic valve replacement affect cardiopulmonary and muscle function during exercise? What is the main finding and its importance? Early after the surgical replacement of the aortic valve a significant decline in pulmonary function was observed, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. These date reiterate, despite restoration of aortic valve function, the need for a tailored rehabilitation programme for the respiratory and peripheral muscular system. Suboptimal post-operative improvements in functional capacity are often observed after minimally invasive aortic valve replacement (mini-AVR). It remains to be studied how AVR affects the cardiopulmonary and skeletal muscle function during exercise to explain these clinical observations and to provide a basis for improved/tailored post-operative rehabilitation. Twenty-two patients with severe aortic stenosis (AS) (aortic valve area (AVA) <1.0cm²) were pre-operatively compared to 22 healthy controls during submaximal constant-workload endurance-type exercise for oxygen uptake ( ), carbon dioxide output ( ), respiratory gas exchange ratio, expiratory volume ( ), ventilatory equivalents for O2 ( / ) and CO2 ( / ), respiratory rate (RR), tidal volume (Vt ), heart rate (HR), oxygen pulse ( /HR), blood lactate, Borg ratings of perceived exertion (RPE) and exercise-onset kinetics. These exercise tests were repeated at 5 and 21days after AVR surgery (n=14), along with echocardiographic examinations. Respiratory exchange ratio and ventilatory equivalents ( / and / ) were significantly elevated, and /HR were significantly lowered, and exercise-onset kinetics were significantly slower in AS patients vs. healthy controls (P<0.05). Although the AVA was restored by mini-AVR in AS patients, / and / further worsened significantly within 5days after surgery, accompanied by elevations in Borg RPE, and RR, and lowered Vt . At 21days after mini-AVR, exercise-onset kinetics further slowed significantly (P<0.05). A decline in pulmonary function was observed early after mini-AVR surgery, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. Therefore, a tailored rehabilitation programme should include training modalities for the respiratory and peripheral muscular system.

A prospective 5-year study of exercise performance following Melody valve implant

The long-term benefits of Melody valve implant for right ventricular outflow tract conduit obstruction or insufficiency on exercise capacity are undefined. As part of the Melody valve clinical trial, 136 patients with congenital heart disease underwent serial cardiopulmonary exercise testing prior to, 6 months after, and annually for up to 5 years postimplant. Mean age at Melody valve implantation was 22.4 ± 0.9 years (range 7-53 years). The 95 patients who completed the study protocol provide the basis of this report. An initial improvement in % predicted workload was present at 6 months postimplant; however, at the final (5 year) follow-up, sustained or further improvements in workload were not demonstrated for the entire cohort compared to baseline. By subgroup analysis, age <17 years at implant and pulmonary regurgitation as the primary lesion were variables associated with sustained improvement in exercise performance. There were sustained improvements in the ventilatory equivalents for O2 (minute ventilation/O2 intake, P = .01) and CO2 (minute ventilation/CO2 output, P < .01) at the ventilatory anaerobic threshold at the study conclusion. Improvements in forced vital capacity were also observed during the study but not sustained at the final follow-up. A cautious appraisal of the cardiovascular benefits of Melody valve implant on sustained improvements in exercise performance appears warranted. Although the observed changes in pulmonary function suggest improved restrictive lung physiology and more efficient gas exchange, after an initial increase in % predicted performance, neither sustained nor further improvements in exercise performance were observed, except in specific patient subgroups.

Obesity is Associated With an Increased Respiratory Workload During Exercise

SESSION TITLE: Pulmonary Physiology SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, November 1, 2017 at 01:30 PM - 02:30 PM PURPOSE: Prior literature supports a relationship between obesity and respiratory workload. Among younger, active duty military patients with respiratory symptoms, we sought to quantify the effect that obesity has on respiratory workload during cardiopulmonary exercise testing (CPET). METHODS: The STAMPEDE Study enrolls enrolls active duty service members with respiratory symptoms following deployment to Iraq or Afghanistan. All subjects undergo a comprehensive, standardized pulmonary evaluation. During treadmill CPET, minute ventilation (VE), proportion of maximum voluntary ventilation (VE/MVV), and the ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2) were measured at rest, a pre-specificed, sub-maximal VO2 of 25mL/kg/min and at max exercise. Subjects with obesity (BMI > 30 kg/m2) were compared to those without using the student t-test. We modeled obesity against other predictors of respiratory workload using linear regression. Data were analyzed using STATA (version 12). RESULTS: A total to 301 participants had data available for analysis. Patients with obesity were older, and more likely to be female, depressed and positive for serum nicotine. FVC % predicted (PPD) was lower (95.1 vs 90.2%; p=0.01) and R5 (129.8 vs 157.2%; p<0.001) and R20 (127.1 vs 136.2%; p=0.045) PPD were higher in patients with obesity. Patients with obesity had higher VE and VE/MVV at rest, higher RR, TV, VE and VE/MVV at submaximal exercise, and no differences in respiratory workload but significantly lower VO2 (cc/kg/min) at max exercise. At submaximal exercise, obesity was significantly related to VE/MVV (p<0.001) after controlling for significant differences at baseline. CONCLUSIONS: In a cohort of active duty service members with respiratory symptoms following deployment, obesity was independently associated with an elevated respiratory response to submaximal exercise. The obese do more respiratory work to achieve a given VO2 (ml/kg/min). CLINICAL IMPLICATIONS: BMI is independently associated with respiratory workload among service members presenting with unexplained dyspnea. DISCLOSURE: The following authors have nothing to disclose: Michael McMahon, Aaron Holley, Jacob Collen, Andrew Skabelund, Jeffrey Woods, John Sherner, Michael Morris No Product/Research Disclosure Information

Clinical significance of the overshoot phenomena of respiratory gas indices during recovery from maximal exercise testing

BackgroundOvershoot phenomena of the gas exchange ratio (R:VCO2/VO2), ventilatory equivalent for O2 (VE/VO2), and end-tidal O2 pressure (PETO2) are commonly observed during recovery from maximal cardiopulmonary exercise testing (CPX). We investigated the clinical significance of the overshoots of these indices by comparing their magnitudes between healthy subjects and cardiac patients with left ventricular dysfunction. MethodsIn total, 121 subjects (73 healthy subjects and 48 cardiac patients with left ventricular ejection fraction<40%) who underwent CPX and achieved peak R≥1.10 were enrolled. We evaluated and calculated the presence and magnitude of the overshoot phenomena of R, VE/VO2, and PETO2. ResultsThe overshoot phenomena of R, VE/VO2, and PETO2 were observed in all the subjects. The magnitudes of the R (21.4±12.4% vs. 29.3±10.0%, p<0.001), VE/VO2 (45.5±23.5% vs. 77.5±28.5%, p<0.001), and PETO2 (5.3±3.4% vs. 10.1±4.2%, p<0.001) overshoots were significantly lower in cardiac patients than in healthy subjects. In cardiac patients, the magnitude of the PETO2 overshoot showed significant positive correlations with the peak O2 uptake (VO2) (r=0.52, p<0.001), anaerobic threshold (r=0.43, p=0.003), and ratio of the increase in VO2 to the increase in the work rate (r=0.41, p=0.005), and a negative correlation with the slope of the increase in ventilation versus the increase in CO2 output (r=−0.50, p<0.001). The magnitudes of the R and VE/VO2 overshoots showed the same patterns of significant correlation with the CPX indices. ConclusionsWe concluded that the overshoots of R, VE/VO2, and PETO2 during recovery from maximal exercise reflect the natural cardiopulmonary adaptation after exercise and are more prominent in subjects with better cardiopulmonary function.

Ventilatory patterns differ between maximal running and cycling

To determine the effect of exercise mode on ventilatory patterns, 22 trained men performed two maximal graded exercise tests; one running on a treadmill and one cycling on an ergometer. Tidal flow-volume (FV) loops were recorded during each minute of exercise with maximal loops measured pre and post exercise. Running resulted in a greater VO2peak than cycling (62.7±7.6 vs. 58.1±7.2mLkg−1min−1). Although maximal ventilation (VE) did not differ between modes, ventilatory equivalents for O2 and CO2 were significantly larger during maximal cycling. Arterial oxygen saturation (estimated via ear oximeter) was also greater during maximal cycling, as were end-expiratory (EELV; 3.40±0.54 vs. 3.21±0.55L) and end-inspiratory lung volumes, (EILV; 6.24±0.88 vs. 5.90±0.74L). Based on these results we conclude that ventilatory patterns differ as a function of exercise mode and these observed differences are likely due to the differences in posture adopted during exercise in these modes.

Clinical characteristics and lung function in chronic obstructive pulmonary disease complicated with impaired peripheral oxygenation

During exercise testing, patients with chronic obstructive pulmonary disease (COPD) often present with ventilatory limitations and various combinations of impaired peripheral oxygenation (IPO) to the exercising muscles. The entities of IPO include anemia, circulation impairment and deconditioning. COPD-IPO is not widely accepted as being a subgroup of COPD. Therefore, the aim of this study was to evaluate the clinical features of COPD-IPO patients. Forty-seven COPD patients underwent cardiopulmonary exercise testing. COPD-IPO was identified when all IPO variables had abnormal values. The patients who did not meet the COPD-IPO criteria were defined as the NIPO group. The variables with abnormal values included peak oxygen uptake (VO₂) <85% predicated, anaerobic threshold <40% VO₂max pred, VO₂-work rate slope <8.6 ml/watt, oxygen pulse <80%pred, and ventilatory equivalents for O₂ and CO₂ at nadir (>31 and >34, respectively). Anthropometrics, biochemistry, and lung function were compared between the groups. Forty-six COPD patients were enrolled after excluding one patient who had technical difficulties in performing the exercise tests. Despite FEV1 and FVC being similarly reduced (p = NS) between the groups, the COPD-IPO (n = 13, 28%) patients had lower body mass index and were taller, and had impaired diffusing capacity and larger total lung capacity and air-trapping (all p < 0.05). We concluded that COPD patients with all six variables having abnormal values are a unique subgroup and that identification of these patients is worthwhile for further investigations and management such as exercise training and nutritional supplements.

Identificação do limiar anaeróbio ventilatório em crianças e adolescentes: revisão da literatura

O limiar anaerobio ventilatorio (LAV) tem sido utilizado em pesquisas para representar a funcao pulmonar e a capacidade de desempenho submaximo de criancas e adolescentes. O estudo teve como objetivo identificar, a) a que grupo de criancas e adolescentes tem sido o principal foco dos trabalhos; b) quais criterios tem sido utilizados para identificacao do LAV; c) quais sao as principais referencias bibliograficas utilizadas e em que se apoiam as suas fundamentacoes teoricas. Foi feito um levantamento de trabalhos que tenham utilizado o LAV como metodologia de estudo nas bases de dados LILACS, MEDLINE, SCIELO, e PUBMED no periodo de 2000 a 2010 para identificacao de categorias por meio de analise de conteudo. Apresentacao dos dados pela estatistica descritiva. Foram encontrados quarenta e um trabalhos, que se distribuiram assim, de acordo com a categoria identificada: intolerância severa ao exercicio (21=51%); saudaveis (6=15%); obesas e comparacao de metodologias (4=10%, cada); cinetica de O2 (3=7%); esporte (2=5%); desnutricao pregressa, asma, e percepcao do esforco (1=2%, cada). O principal criterio tem sido o V-slope e a principal referencia utilizada e Beaver WL, Wasserman K, Whipp BJ (1986), com 24 ocorrencias (53%). Alem desse metodo, os equivalentes ventilatorios de oxigenio e de dioxido de carbono tem sido utilizados, o que representou 37% (17 trabalhos). Conclusao: os dados indicam que a principal utilizacao do LAV tem sido para estudos de reabilitacao de criancas e adolescentes por meio da tecnica do V-slope.

JOURNAL/jscr/04.03/00124278-201103000-00034/OV0312/v/2021-02-09T093750Z/r/image-png o2max and ventilatory threshold of trained cyclists are not affected by 28-day l-arginine supplementation

The ergogenic effect of L-arginine on an endurance-trained population is not well studied. The few studies that have investigated L-arginine on this population have not been conducted in a laboratory setting or measured aerobic variables. The purpose of the current study is to determine if 28 days of L-arginine supplementation in trained male cyclists affects VO2max and ventilatory threshold (VT). Eighteen (18) endurance-trained male cyclists (mean ± SD, age: 36.3 ± 7.9 years; height: 182.4 ± 4.6 cm; and body mass: 79.5 ± 4.7 kg) performed a graded exercise test (GXT; 50 W + 25 W·min) before and after 28 days of supplementation with L-arginine (ARG; 2 × 6 g·d) or placebo (PLA; cornstarch). The GXT was conducted on the subject's own bicycle using the RacerMate CompuTrainer (Seattle, WA, USA). VO2 was continuously recorded using the ParvoMedics TrueOne 2400 metabolic cart (Salt Lake City, UT, USA) and VT was established by plotting the ventilatory equivalent for O2 (VE/VO2) and the ventilatory equivalent for CO2 (VE/VCO2) and identifying the point at which VE/VO2 increases with no substantial changes in VE/VCO2. L-arginine supplementation had no effect from initial VO2max (PL, 58.7 ± 7.1 ml·kg·min; ARG, 63.5 ± 7.3 ml·kg·min) to postsupplement VO2max (PL, 58.9 ± 6.0 ml·kg·min; ARG, 63.2 ± 7.2 ml·kg·min). Also, no effect was seen from initial VT (PL, 75.7 ± 4.6% VO2max; ARG, 76.0 ± 5.3% VO2max) to postsupplement VT (PL, 74.3 ± 8.1% VO2max; ARG, 74.2 ± 6.4% VO2max). These results indicate that L-arginine does not impact VO2max or VT in trained male cyclists.

Ventilatory Changes After Active Heat Acclimation for Multiday Ultramarathon Races in the Sahara Desert

To determine the effect of active heat acclimation (HA) on ventilatory responses, 4 endurance‐trained athletes (42.0 ± 5.7 y, mean ± SD) underwent 10 day of activity in 35–40°C and ~15% RH conditions to prepare for multiday ultramarathon races in the Sahara desert. Exercise during HA included 1 h/day of running at ≥50% maximal oxygen consumption (VO2max). Physiological assessments included pre‐ and post‐HA VO2max, heart rate (HR), esophageal (Tes), rectal (Tre), and skin temperatures (4 sites). Pre‐ and post‐HA VO2max values were not significantly different (52.8 ± 4.0 vs 52.0 ± 4.6 mL·kg−1·min−1, p = 0.35). Attainment of HA was confirmed by a significant reduction in exercise HR (p &lt; 0.01) and trends (p=0.12) for reductions in both Thermal Comfort ratings and Borg Ratings of Perceived Exertion over the 10‐d HA period. During incremental exercise, from pre‐ to post‐HA, the ventilatory equivalent for O2 (VE/VO2) increased from 28.6 ± 1.0 to 30.2 ± 1.0 (p = 0.06), whereas the ventilatory equivalent for CO2 (VE/VCO2) showed no change (29.6 ± 0.8 vs 29.8 ± 2.0, p = 0.37). These preliminary data suggest that active HA increases ventilatory responses independently of an exercise training effect.Supported by NSERC, Canadian Foundation for Innovation.

111 COMPARISON OF THE CHARACTERISTICS OF KOREAN PATIENTS WITH NARCOLEPSY OR OBSTRUCTIVE SLEEP APNEA SYNDROME

s of 3rd International Congress of the Association of Sleep Medicine (WASM) / Sleep Medicine 10, Suppl. 2 (2009) S1–S83 S31 tocol taking into consideration age, gender, 2D-echocardiogram, and spirometry. ANOVA, p<0,05. Results: There were no differences in baseline characteristics between groups. Peak oxygen uptake (VO2) was lower in narcoleptic patients compared to OSA and controls group (18,65±6,72; 31,13±9,24; 32,97±7,46; respectively, p<0,01). Peak carbon dioxide production (NAR = 21,74±6,86; OSA = 31,06±7,50; CON = 35,59±8,97; p<0,01), anaerobic threshold (NAR = 13,74±2,85; OAS = 23,40±5,11; CON= 25,12±4,47; p<0,01), ventilatory equivalents for O2 (NAR = 38,56±10,61; OSA = 25,65±4,18; CON = 27,79±4,17; p<0,01) and CO2 (NAR = 33,39±6,87; OSA = 23,86±2,00; CON = 25,76±1,67; p<0,01) were lower in narcoleptic patients compared to all other groups. Conclusion: Narcolepsy was associated to lower exercise capacity when compared to OSA and controls subjects. 111 COMPARISON OF THE CHARACTERISTICS OF KOREAN PATIENTS WITH NARCOLEPSY OR OBSTRUCTIVE SLEEP APNEA SYNDROME S.C. Hong, J.H. Han, S.P. Lee, H.J. Seo, H.K. Lim. St. Vincent’s Hospital, The

Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation

Hyperthermia-induced hyperventilation has been proposed to be a human thermolytic thermoregulatory response and to contribute to the disproportionate increase in exercise ventilation (VE) relative to metabolic needs during high-intensity exercise. In this study it was hypothesized that VE would adapt similar to human eccrine sweating (E(SW)) following a passive heat acclimation (HA). All participants performed an incremental exercise test on a cycle ergometer from rest to exhaustion before and after a 10-day passive exposure for 2 h/day to either 50 degrees C and 20% relative humidity (RH) (n = 8, Acclimation group) or 24 degrees C and 32% RH (n = 4, Control group). Attainment of HA was confirmed by a significant decrease (P = 0.025) of the esophageal temperature (T(es)) threshold for the onset of E(SW) and a significantly elevated E(SW) (P < or = 0.040) during the post-HA exercise tests. HA also gave a significant decrease in resting T(es) (P = 0.006) and a significant increase in plasma volume (P = 0.005). Ventilatory adaptations during exercise tests following HA included significantly decreased T(es) thresholds (P < or = 0.005) for the onset of increases in the ventilatory equivalents for O(2) (VE/VO(2)) and CO(2) (VE/VCO(2)) and a significantly increased VE (P < or = 0.017) at all levels of T(es). Elevated VE was a function of a significantly greater tidal volume (P = 0.003) at lower T(es) and of breathing frequency (P < or = 0.005) at higher T(es). Following HA, the ventilatory threshold was uninfluenced and the relationships between VO(2) and either VE/VO(2) or VE/VCO(2) did not explain the resulting hyperventilation. In conclusion, the results support that exercise VE following passive HA responds similarly to E(SW), and the mechanism accounting for this adaptation is independent of changes of the ventilatory threshold or relationships between VO(2) with each of VE/VO(2) and VE/VCO(2).

Human ventilatory responsiveness to hypoxia is unrelated to maximal aerobic capacity

Ventilatory responsiveness to hypoxia (HVR) has been reported to be different between highly trained endurance athletes and healthy sedentary controls. However, a linkage between aerobic capacity and HVR has not been a universal finding. The purpose of this study was to examine the relationship between HVR and maximal oxygen consumption (VO2 max) in healthy men with a wide range of aerobic capacities. Subjects performed a HVR test followed by an incremental cycle test to exhaustion. Participants were classified according to their maximal aerobic capacity. Those with a VO2 max of >or=60 ml x kg(-1) x min(-1) were considered highly trained (n = 13); those with a VO2 max of 50-60 ml x kg(-1) x min(-1) were considered moderately-trained (n = 18); and those with a VO2 max of <50 ml x kg(-1) x min(-1) were considered untrained (n = 24). No statistical differences were detected between the three groups for HVR (P > 0.05), and the HVR values were variable within each group (range: untrained = 0.28-1.61, moderately trained = 0.23-2.39, and highly trained = 0.08-1.73 l x min.%arterial O2 saturation(-1)). The relationship between HVR and VO2 max was not statistically significant (r = -0.1723; P > 0.05). HVR was also unrelated to maximal minute ventilation and ventilatory equivalents for O2 and CO2. We found that a spectrum of hypoxic ventilatory control is present in well-trained endurance athletes and moderately and untrained men. We interpret these observations to mean that other factors are more important in determining hypoxic ventilatory control than physical conditioning per se.

Effects of acute hypoxia on the estimation of the lactate threshold from ventilatory gas exchange indices during an incremental exercise test.

The purpose of this study was to investigate the validity of non-invasive lactate threshold estimation using ventilatory and pulmonary gas exchange indices under condition of acute hypoxia. Seven untrained males (21.4+/-1.2 years) performed two incremental exercise tests using an electromagnetically braked cycle ergometer: one breathing room air and other breathing 12 % O2. The lactate threshold was estimated using the following parameters: increase of ventilatory equivalent for O2 (VE/VO2) without increase of ventilatory equivalent for CO2 (VE/VCO2). It was also determined from the increase in blood lactate and decrease in standard bicarbonate. The VE/VO2 and lactate increase methods yielded the respective values for lactate threshold: 1.91+/-0.10 l/min (for the VE/VO2) vs. 1.89+/-0.1 l/min (for the lactate). However, in hypoxic condition, VE/VO2 started to increase prior to the actual threshold as determined from blood lactate response: 1.67+/-0.1 l/min (for the lactate) vs. 1.37+/-0.09 l/min (for the VE/VO2) (P=0.0001), i.e. resulted in pseudo-threshold behavior. In conclusion, the ventilatory and gas exchange indices provide an accurate lactate threshold. Although the potential for pseudo-threshold behavior of the standard ventilatory and gas exchange indices of the lactate threshold must be concerned if an incremental test is performed under hypoxic conditions in which carotid body chemosensitivity is increased.

Assessment of ventilatory thresholds during graded and maximal exercise test using time varying analysis of respiratory sinus arrhythmia

Objective: To test whether ventilatory thresholds, measured during an exercise test, could be assessed using time varying analysis of respiratory sinus arrhythmia frequency (fRSA). Methods: Fourteen sedentary subjects and 12...

Similarity Of Maximum Ventilatory Quotients For O2 And CO2 Among Women With Lupus And Controls

Background We have previously reported functional aerobic impairment, increased cardiac output and stroke volume, and attenuated arteriovenous oxygen difference (a-vO2) in women who had mild lupus and normal hematocrit. We hypothesize that attenuated muscle oxygen extraction impairs oxidative metabolism in lupus. However, deficits in hemoglobin oxygenation could also limit the widening of a-vO2. Purpose This study was conducted to examine relationships among gas exchange and pulmonary ventilation in women with lupus. Methods Here, we compared the ventilatory equivalents for O2 (Ve/VO2) and CO2 (Ve/VCO2) among women with (n=16) and without (n=16) lupus. These quotients and corollary data were obtained at maximum treadmill exercise. Results Maximum attained Ve/VO2 was 37.38±08.46 in the women with lupus and 37.00±08.16 in the controls. Maximum attained Ve/VCO2 was 33.06±5.36 in the women with lupus and 33.19±04.64 in the controls. Ve/VO2 and Ve/VCO2 were not significantly different for the women with lupus and controls. Maximum attained VO2 (lupus =19.6±04.4 ml/kg/min vs. control = 27.4±04.7 ml/kg/min; p < 0.0001) and maximum widening of a-vO2 (lupus=10.9±02.5 ml/dl vs. control=13.3±01.8 ml/dl; p < 0.0026) were significantly lower in women with lupus than in controls. Conclusion These women with lupus had neither a history of pulmonary impairment nor symptoms of pulmonary complications and were not anemic. Neither the ratio of air ventilated to oxygen consumed nor minute ventilation normalized to expiration of CO2 appeared to be altered, at maximum exertion, in the women with lupus. Therefore, it is unlikely that impaired lung diffusion limited oxidative metabolism in these women. In the women with lupus, oxidative capacity was most likely limited by deficits in the ability of the peripheral exercising muscles to extract oxygen from the blood. Supported by NIH R03 HD39775-02

Inefficient ventilation and reduced respiratory muscle capacity in congestive heart failure.

The extent and time-course of changes in lung volumes, ventilatory efficiency at rest and during exercise, and respiratory muscle function and their influence on exercise limitation in congestive heart failure (CHF) are unclear. It is unknown whether respiratory muscle function may predict changes in exercise limitation or may be impaired in patients with poor outcome. 145 male patients (54 +/- 1 years) suffering from CHF (NYHA class I-III, mean 2.3 +/- 0.1), with a LVEF of 23 +/- 1%, and a mean peak O2 uptake (VO2peak) 15.0 +/- 0.5 mL X min(-1) X kg(-1), were studied. They were grouped in Weber functional classes A to D according to their VO2peak. Significant increases in ventilatory equivalents for O2 and CO2 (VE/VCO2peak) and in dead space ventilation at rest and during exercise were found with increasing exercise limitation. Moreover, there was a correlation of static and dynamic lung volumes (inspiratory vital capacity, IVC, r = 0.43, P < 0.01), as well as of maximal inspiratory pressure (MIP; r = 0.46, P < 0.01) with VO2peak. Patients who died (n = 26) or were heart transplanted (n = 20) during a follow-up (mean 800 +/- 10 days) had a reduced MIP (6.4 +/- 0.4 kPa) as compared with survivors (n = 82; 9.3 +/- 0.7 kPa, P < 0.01). In a subgroup of 33 patients re-evaluated after six months, individual changes in IVC and VE/CO2peak, but not in MIP, correlated to changes in VO2peak (r = 0.69 and r = 0.72 respectively; P < 0.01). In CHF, exercise limitation is associated with reversible lung restriction and inefficient ventilation at rest and during exercise. Patients with severe CHF have a significant reduction in MIP, a finding that is associated with poor outcome.

Effects of 'cool-down' during exercise recovery on cardiopulmonary systems in patients with coronary artery disease.

The effects of 'cool-down' during exercise recovery on cardiovascular and respiratory systems have not been fully clarified. The recovery of respiratory gasses was compared in cardiac patients after maximal exercise during which subjects either performed a cool-down or rested. Twenty-one patients (61+/-10 years) with coronary artery disease performed 2 symptom-limited incremental exercise tests on a cycle ergometer: one with a cool-down and the other without during recovery from the maximal exercise test. Expired gasses were analyzed on a breath-by-breath basis throughout the test and for 6min of recovery. Without a cool-down, the ventilatory equivalent for O2 (VE/O2) increased dramatically during recovery compared with the resting values or those of peak exercise: 44.5+/-7.7 at rest, 44.0+/-10.6 at peak exercise and 63.3+/-14.5 after 2min of recovery. End-tidal PO2 (P(ET)O2) also increased significantly during recovery. However, the overshoot phenomenon of these variables was attenuated when cool-down exercise was performed during recovery. The high ratio of VE/VO2 reflects ventilation perfusion (VA/Q) unevenness and P(ET)O2 is an index of arterial PO2. Thus, it is suggested that cool-down exercise during recovery after maximal exercise testing provides beneficial effects on the respiratory system by decreasing the VA/Q unevenness and relative hyperventilation that are observed when cool-down exercise is not performed.

VE and VCO2 remain tightly coupled during incremental cycling performed after a bout of high-intensity exercise.

The purpose of the present study was to determine whether the linear relationship between CO2 output (VCO2) and pulmonary ventilation (VE) is altered during incremental cycling performed after exercise-induced metabolic acidosis. Ten untrained, female subjects performed two incremental cycling tests (15 W x min(-1) up to 165 W) on separate days. One incremental exercise test was conducted without prior exercise, whereas the other test was preceded by a 1-min bout of maximal cycling. The ventilatory equivalent for O2 (VE/VO2) was only elevated above control values at 15-60 W during incremental cycling performed after high-intensity exercise. In contrast, the ventilatory equivalent for CO2 (VE/VCO2) was significantly increased above control levels at nearly every work stage of incremental work (all except 165 W). Hyperventilation relative to VCO2 was confirmed by the significantly lower end-tidal CO2 tension (P(ET)CO2) obtained throughout the incremental cycling that was performed after high-intensity exercise (except at 165 W). VE and VCO2 were significantly correlated under both treatment conditions (r > 0.99; P < 0.001). Moreover, both the slope and y-intercept of the linear regression were found to be significantly elevated during the incremental cycling performed after high-intensity cycling compared to control conditions (P < 0.01). The increase in the slope of the VE-VCO2 relationship during incremental exercise performed under these conditions does not represent an uncoupling of VE from VCO2, but could be accounted for by the significantly lower P(ET)CO2 observed during exercise.