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Smith JR, Senefeld JW, Larson KF, Joyner MJ. Consequences of group III/IV afferent feedback and respiratory muscle work on exercise tolerance in heart failure with reduced ejection fraction. Exp Physiol 2023; 108:1351-1365. [PMID: 37735814 PMCID: PMC10900130 DOI: 10.1113/ep090755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 09/06/2023] [Indexed: 09/23/2023]
Abstract
Exercise intolerance and exertional dyspnoea are the cardinal symptoms of heart failure with reduced ejection fraction (HFrEF). In HFrEF, abnormal autonomic and cardiopulmonary responses arising from locomotor muscle group III/IV afferent feedback is one of the primary mechanisms contributing to exercise intolerance. HFrEF patients also have pulmonary system and respiratory muscle abnormalities that impair exercise tolerance. Thus, the primary impetus for this review was to describe the mechanistic consequences of locomotor muscle group III/IV afferent feedback and respiratory muscle work in HFrEF. To address this, we first discuss the abnormal autonomic and cardiopulmonary responses mediated by locomotor muscle afferent feedback in HFrEF. Next, we outline how respiratory muscle work impairs exercise tolerance in HFrEF through its effects on locomotor muscle O2 delivery. We then discuss the direct and indirect evidence supporting an interaction between locomotor muscle group III/IV afferent feedback and respiratory muscle work during exercise in HFrEF. Last, we outline future research directions related to locomotor and respiratory muscle abnormalities to progress the field forward in understanding the pathophysiology of exercise intolerance in HFrEF. NEW FINDINGS: What is the topic of this review? This review is focused on understanding the role that locomotor muscle group III/IV afferent feedback and respiratory muscle work play in the pathophysiology of exercise intolerance in patients with heart failure. What advances does it highlight? This review proposes that the concomitant effects of locomotor muscle afferent feedback and respiratory muscle work worsen exercise tolerance and exacerbate exertional dyspnoea in patients with heart failure.
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Affiliation(s)
- Joshua R. Smith
- Department of Cardiovascular MedicineMayo ClinicRochesterMNUSA
| | - Jonathon W. Senefeld
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
- Department of Kinesiology and Community HealthUniversity of Illinois at Urbana‐ChampaignUrbanaILUSA
| | | | - Michael J. Joyner
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
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2
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Villarraga N, Warner B, Bruhn EJ, Hammer SM, Bissen TG, Olson TP, Smith JR. Higher Work of Breathing During Exercise in Heart Failure With Preserved Ejection Fraction. Chest 2023; 163:1492-1505. [PMID: 36470415 PMCID: PMC10258442 DOI: 10.1016/j.chest.2022.11.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 11/21/2022] [Accepted: 11/21/2022] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND It is unknown if pulmonary alterations in heart failure with preserved ejection fraction (HFpEF) impact respiratory mechanics during exercise. RESEARCH QUESTION Are the operating lung volumes, work of breathing (Wb), and power of breathing (Pb) abnormal in patients with HFpEF during exercise? STUDY DESIGN AND METHODS Patients with HFpEF (n = 8; median age, 71 years [interquartile range (IQR), 66-80 years]) and control participants (n = 9; median age, 68 years [IQR, 64-74 years]) performed incremental cycling to volitional exhaustion. Esophageal pressure, end-expiratory lung volume (EELV), inspiratory lung volume (EILV), and ventilatory variables were compared at similar absolute (30 and 50 L/min) and relative (45% of peak, 70% of peak, and 100% of peak) minute ventilation (V.E) during exercise. RESULTS During exercise, EELVs were not different between patients with HFpEF and control participants (P > .13 for all). EILVs were lower in patients with HFpEF than control participants at 45% and 70% V.E peak (P < .03 for all). Dynamic lung compliance was lower in patients with HFpEF than control participants at 30 L/min, 50 L/min, 45% V.E peak, and 100% V.E peak (P < .04 for all). Compared with control participants, patients with HFpEF showed higher total Wb and Pb at 30 L/min (Wb: median, 1.08 J/L [IQR, 0.93-1.82 J/L] vs 0.52 J/L [IQR, 0.43-0.71 J/L]; Pb: median, 36 J/min [IQR, 30-59 J/min] vs 17 J/min [IQR, 11-23 J/min] and 50 L/min; Wb: median, 1.40 J/L [IQR, 1.27-1.68 J/L] vs 0.90 J/L [IQR, 0.74-1.05 J/L]; Pb: median, 73 J/min [IQR, 60-83 J/min] vs 45 J/min [IQR, 33-63 J/min]; P < .01 for all). At 30 and 50 L/min, inspiratory and expiratory resistive Wb and Pb were higher in patients with HFpEF than control participants (P < .04 for all). Total Wb was higher for patients with HFpEF than control participants at 45% of V.E peak (P = .02). Total Pb was higher for control participants than patients with HFpEF at 100% V.E peak because of higher inspiratory resistive Pb (P < .04 for both). INTERPRETATION These data demonstrate the HFpEF syndrome is associated with pulmonary alterations eliciting a greater Pb during exercise resulting from greater inspiratory and expiratory resistive Pb.
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Affiliation(s)
| | - Brit Warner
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN
| | - Eric J Bruhn
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN
| | - Shane M Hammer
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN; School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK
| | - Thomas G Bissen
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN
| | - Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN.
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Neder JA, Phillips DB, O'Donnell DE, Dempsey JA. Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension. Eur Respir J 2022; 60:13993003.00144-2022. [PMID: 35618273 DOI: 10.1183/13993003.00144-2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 05/05/2022] [Indexed: 01/11/2023]
Abstract
Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.
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Affiliation(s)
- J Alberto Neder
- Clinical Exercise Physiology and Respiratory Investigation Unit, Division of Respiratory and Critical Care Medicine, Dept of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, ON, Canada
| | - Devin B Phillips
- Clinical Exercise Physiology and Respiratory Investigation Unit, Division of Respiratory and Critical Care Medicine, Dept of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, ON, Canada
| | - Denis E O'Donnell
- Clinical Exercise Physiology and Respiratory Investigation Unit, Division of Respiratory and Critical Care Medicine, Dept of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, ON, Canada
| | - Jerome A Dempsey
- John Rankin Laboratory of Pulmonary Medicine, Dept of Population Health Sciences, University of Wisconsin-Madison, Madison, WI, USA
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4
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Pulmonary artery-to-aorta ratio on high-resolution computed tomography and exercise performance in systolic heart failure. Am J Med Sci 2022; 364:502-504. [PMID: 35588892 DOI: 10.1016/j.amjms.2022.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 09/16/2021] [Accepted: 05/11/2022] [Indexed: 01/25/2023]
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Yamazaki Y, Yabe H, Sawano K, Tawara Y, Ohgi S. Effects of exertional dyspnea on early mobilization of patients with acute decompensated heart failure. J Phys Ther Sci 2022; 34:547-553. [PMID: 35937626 PMCID: PMC9345754 DOI: 10.1589/jpts.34.547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 05/09/2022] [Indexed: 11/27/2022] Open
Abstract
[Purpose] In this study, we investigated the association between exertional dyspnea and
length of the mobilization program in patients with acute decompensated heart failure.
[Participants and Methods] We recruited all consecutive patients with heart failure who
were hemodynamically stabilized after administration of intravenous medication and were
able to walk >10 m before admission. Exertional dyspnea was evaluated using the visual
analog scale in all patients after the 10-m walk during each session of the mobilization
program. Multiple regression analysis was used to determine the factors associated with
length of the mobilization program. [Results] Our study included 52 patients. Multiple
regression analysis showed that the length of the mobilization program was significantly
associated with the visual analog scale on day 3 and the length before the start of the
mobilization program; however, the length of the mobilization program showed no
significant association with age and blood urea nitrogen levels. The standardized
coefficients for the visual analog scale scores on day 3 and the length before the start
of the mobilization program were 0.49 and 0.33, respectively. [Conclusion] Exertional
dyspnea is a good predictor of the length of the mobilization program. Our findings
highlight the importance of evaluation of exertional dyspnea.
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Affiliation(s)
- Yota Yamazaki
- Department of Rehabilitation Technology, Shizuoka City Shimizu Hospital: 1231 Miyakami, Shimizu-ku, Shizuoka, Shizuoka 424-8636, Japan
| | - Hiroki Yabe
- School of Rehabilitation Sciences, Seirei Christopher University, Japan
| | - Koichi Sawano
- Department of Rehabilitation Technology, Shizuoka City Shimizu Hospital: 1231 Miyakami, Shimizu-ku, Shizuoka, Shizuoka 424-8636, Japan
| | - Yuichi Tawara
- School of Rehabilitation Sciences, Seirei Christopher University, Japan
| | - Shohei Ohgi
- School of Rehabilitation Sciences, Seirei Christopher University, Japan
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Godbole R, Church SB, Abolhoda A, Porszasz J, Sassoon CSH. Resting Physiologic Dead Space as Predictor of Postoperative Pulmonary Complications After Robotic-Assisted Lung Resection: A Pilot Study. Front Physiol 2022; 13:803641. [PMID: 35923226 PMCID: PMC9340204 DOI: 10.3389/fphys.2022.803641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 06/17/2022] [Indexed: 11/13/2022] Open
Abstract
Lung resection surgery carries significant risks of postoperative pulmonary complications (PPC). Cardiopulmonary exercise testing (CPET) is performed to predict risk of PPC in patients with severely reduced predicted postoperative forced expiratory volume in one second (FEV1) and diffusion of carbon monoxide (DLCO). Recently, resting end-tidal partial pressure of carbon dioxide (PETCO2) has been shown as a good predictor for increased risk of PPC. However, breath-breath breathing pattern significantly affects PETCO2. Resting physiologic dead space (VD), and physiologic dead space to tidal volume ratio (VD/VT), may be a better predictor of PPC than PETCO2. The objective of this study was to prospectively determine the utility of resting measurements of VD and VD/VT in predicting PPC in patients who underwent robotic-assisted lung resection for suspected or biopsy-proven lung malignancy. Thirty-five consecutive patients were included in the study. Patients underwent preoperative pulmonary function testing, symptom-limited CPET, and a 6-min walk test. In the first 2 min prior to the exercise portion of the CPET, we obtained resting VT, minute ventilation (V˙E), VD (less instrument dead space), VD/VT, PETCO2, and arterial blood gases. PPC within 90 days were recorded. Fourteen (40%) patients had one or more PPC. Patients with PPC had significantly elevated resting VD compared to those without (0.318 ± 0.028 L vs. 0.230 ± 0.017 L (± SE), p < 0.006), and a trend toward increased VD/VT (0.35 ± 0.02 vs. 0.31 ± 0.02, p = 0.051). Area under the receiver operating characteristic (ROC) for VD was 0.81 (p < 0.002), VD/VT was 0.68 (p = 0.077), and PETCO2 was 0.52 (p = 0.840). Peak V˙O2, V˙E/ V˙CO2 slope, pulmonary function tests, 6-min walk distance and arterial blood gases were similar between the two groups. Intensive care unit and total hospital length of stay was significantly longer in those with PPC. In conclusion, preoperative resting VD was significantly elevated in patients with PPC. The observed increase in resting VD may be a potentially useful predictor of PPC in patients undergoing robotic-assisted lung resection surgery for suspected or biopsy-proven lung malignancy. A large prospective study is needed for confirmation.
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Affiliation(s)
- Rohit Godbole
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Irvine, CA, United States
| | - Sanford B. Church
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Irvine, CA, United States
| | - Amir Abolhoda
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Irvine, CA, United States
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, VA Long Beach Healthcare System, Long Beach, CA, United States
| | - Janos Porszasz
- The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, United States
| | - Catherine S. H. Sassoon
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Irvine, CA, United States
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, VA Long Beach Healthcare System, Long Beach, CA, United States
- *Correspondence: Catherine S. H. Sassoon,
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Tanaka-Yagi Y, Yamaguchi T, Matsuda Y, Mori M, Ikari T, Miwa S, Suzuki K, Tachikawa R, Nakata K, Kanatani M. Morphine May Contribute to Improving Respiratory Failure in Severe COVID-19: A Case Report. Indian J Palliat Care 2022; 28:221-223. [PMID: 35673688 PMCID: PMC9168286 DOI: 10.25259/ijpc_132_2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 04/18/2022] [Indexed: 12/15/2022] Open
Abstract
At present, the world is undergoing successive waves of the COVID-19 pandemic. When COVID-19 becomes severe, it causes respiratory failure and symptoms of dyspnoea. The patient’s dyspnoea worsens to the IPOS of 3. One COVID-19 patient admitted to our medical institution developed severe illness characterised by hypoxaemia and dyspnoea. In addition to disease-modifying treatments such as remdesivir and dexamethasone, we administered morphine to relieve his dyspnoea. Surprisingly, we observed an improvement in both hypoxaemia and dyspnoea.
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Affiliation(s)
| | - Takashi Yamaguchi
- Department of Palliative Medicine, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan,
| | - Yoshinobu Matsuda
- Department of Psychosomatic Internal Medicine, Kinki-Chuo Chest Medical Center, Sakai, Osaka, Japan,
| | - Masanori Mori
- Department of Palliative and Supportive Care Division, Seirei Mikatahara General Hospital, Hamamatsu, Shizuoka, Japan,
| | - Tomoo Ikari
- Department of Palliative Medicine, Tohoku University School of Medicine, Sendai, Miyagi, Japan,
| | - Satoru Miwa
- Department of Seirei Hospice, Seirei Mikatahara General Hospital, Hamamatsu, Shizuoka, Japan,
| | - Kozue Suzuki
- Department of Palliative Care, Tokyo Metropolitan Cancer and Infectious Disease Center Komagome Hospital, Tokyo, Japan,
| | - Ryo Tachikawa
- Department of Respiratory Medicine, Kobe City Medical Center General Hospital, Kobe, Hyogo, Japan,
| | - Kyosuke Nakata
- Department of Palliative Care, Konan Medical Center, Hyogo, Japan,
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Smith JR, Joyner MJ, Curry TB, Borlaug BA, Keller-Ross ML, Van Iterson EH, Olson TP. Influence of locomotor muscle group III/IV afferents on cardiovascular and ventilatory responses in human heart failure during submaximal exercise. J Appl Physiol (1985) 2022; 132:903-914. [PMID: 35201931 PMCID: PMC8957342 DOI: 10.1152/japplphysiol.00371.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 02/22/2022] [Accepted: 02/22/2022] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study is to determine the influence of locomotor muscle group III/IV afferent inhibition on central and peripheral hemodynamics at multiple levels of submaximal cycling exercise in patients with heart failure with reduced ejection fraction (HFrEF). Eleven patients with HFrEF and nine healthy matched controls were recruited. The participants performed a multiple stage [i.e., 30 W, 50%peak workload (WL), and a workload eliciting a respiratory exchange ratio (RER) of ∼1.0] exercise test with lumbar intrathecal fentanyl (FENT) or placebo (PLA). Cardiac output ([Formula: see text]tot) was measured via open-circuit acetylene wash-in technique and stroke volume was calculated. Leg blood flow ([Formula: see text]l) was measured via constant infusion thermodilution and leg vascular conductance (LVC) was calculated. Radial artery and femoral venous blood gases were measured. For HFrEF, stroke volume was higher at the 30 W (FENT: 110 ± 21 vs. PLA: 100 ± 18 mL), 50%peak WL (FENT: 113 ± 22 vs. PLA: 103 ± 23 mL), and RER = 1.0 (FENT: 119 ± 28 vs. PLA: 110 ± 26 mL) stages, whereas heart rate and systemic vascular resistance were lower with fentanyl than with placebo (all, P < 0.05). [Formula: see text]tot in HFrEF and [Formula: see text]tot, stroke volume, and heart rate in controls were not different between fentanyl and placebo (all, P > 0.19). During submaximal exercise, controls and patients with HFrEF exhibited increased leg vascular conductance (LVC) with fentanyl compared with placebo (all, P < 0.04), whereas no differences were present in [Formula: see text]l or O2 delivery with fentanyl (all, P > 0.20). Taken together, these findings provide support for locomotor muscle group III/IV afferents playing a role in integrative control mechanisms during submaximal cycling exercise in patients with HFrEF and older controls.NEW & NOTEWORTHY Patients with HFrEF exhibit severe exercise intolerance. One of the primary peripheral mechanisms contributing to exercise intolerance in patients with HFrEF is locomotor muscle group III/IV afferent feedback. However, it is unknown whether these afferents impact the central and peripheral responses during submaximal cycling exercise. Herein, we demonstrate that inhibition of locomotor muscle group III/IV afferent feedback elicited increases in stroke volume during submaximal exercise in HFrEF, but not in healthy controls.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Barry A Borlaug
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
| | - Manda L Keller-Ross
- Division of Physical Therapy and Rehabilitation Sciences, University of Minnesota, Minneapolis, Minnesota
| | - Erik H Van Iterson
- Section of Preventative Cardiology and Rehabilitation, Cleveland Clinic, Cleveland, Ohio
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
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9
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Smith JR, Berg JD, Curry TB, Joyner MJ, Olson TP. Respiratory muscle work influences locomotor convective and diffusive oxygen transport in human heart failure during exercise. Physiol Rep 2021; 8:e14484. [PMID: 32562374 PMCID: PMC7305241 DOI: 10.14814/phy2.14484] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/13/2020] [Accepted: 05/15/2020] [Indexed: 11/24/2022] Open
Abstract
Introduction It remains unclear if naturally occurring respiratory muscle (RM) work influences leg diffusive O2 transport during exercise in heart failure patients with reduced ejection fraction (HFrEF). In this retrospective study, we hypothesized that RM unloading during submaximal exercise will lead to increases in locomotor muscle O2 diffusion capacity (DMO2) contributing to the greater leg VO2. Methods Ten HFrEF patients and 10 healthy control matched participants performed two submaximal exercise bouts (i.e., with and without RM unloading). During exercise, leg blood flow was measured via constant infusion thermodilution. Intrathoracic pressure was measured via esophageal balloon. Radial arterial and femoral venous blood gases were measured and used to calculate leg arterial and venous content (CaO2 and CvO2, respectively), VO2, O2 delivery, and DMO2. Results From CTL to RM unloading, leg VO2, O2 delivery, and DMO2 were not different in healthy participants during submaximal exercise (all, p > .15). In HFrEF, leg VO2 (CTL: 0.7 ± 0.3 vs. RM unloading: 1.0 ± 0.4 L/min, p < .01), leg O2 delivery (CTL: 0.9 ± 0.4 vs. RM unloading: 1.4 ± 0.5 L/min, p < .01), and leg DMO2 (CTL: 31.5 ± 11.4 vs. RM unloading: 49.7 ± 18.6 ml min−1 mmHg−1) increased from CTL to RM unloading during submaximal exercise (all, p < .01), whereas CaO2‐CvO2 was not different (p = .51). The degree of RM unloading (i.e., % decrease in esophageal pressure‐time integral during inspiration) was related to the % increase in leg DMO2 with RM unloading (r = −.76, p = .01). Conclusion Our data suggest RM unloading leads to increased leg VO2 due to greater convective and diffusive O2 transport during submaximal exercise in HFrEF patients.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Jessica D Berg
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
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10
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Smith JR, Hirai DM, Copp SW, Ferguson SK, Holdsworth CT, Hageman KS, Poole DC, Musch TI. Exercise training decreases intercostal and transversus abdominis muscle blood flows in heart failure rats during submaximal exercise. Respir Physiol Neurobiol 2021; 292:103710. [PMID: 34091075 DOI: 10.1016/j.resp.2021.103710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/18/2021] [Accepted: 06/02/2021] [Indexed: 11/30/2022]
Abstract
Diaphragm muscle blood flow (BF) and vascular conductance (VC) are elevated with chronic heart failure (HF) during exercise. Exercise training (ExT) elicits beneficial respiratory muscle and pulmonary system adaptations in HF. We hypothesized that diaphragm BF and VC would be lower in HF rats following ExT than their sedentary counterparts (Sed). Respiratory muscle BFs and mean arterial pressure were measured via radiolabeled microspheres and carotid artery catheter, respectively, during submaximal treadmill exercise (20 m/min, 5 % grade). During exercise, no differences were present between HF + ExT and HF + Sed in diaphragm BFs (201 ± 36 vs. 227 ± 44 mL/min/100 g) or VCs (both, p > 0.05). HF + ExT compared to HF + Sed had lower intercostal BF (27 ± 3 vs. 41 ± 5 mL/min/100 g) and VC (0.21 ± 0.02 vs. 0.31 ± 0.04 mL/min/mmHg/100 g) during exercise (both, p < 0.05). Further, HF + ExT compared to HF + Sed had lower transversus abdominis BF (20 ± 1 vs. 35 ± 6 mL/min/100 g) and VC (0.14 ± 0.02 vs. 0.27 ± 0.05 mL/min/mmHg/100 g) during exercise (both, p < 0.05). These data suggest that exercise training lowers the intercostal and transversus abdominis BF responses in HF rats during submaximal treadmill exercise.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, United States.
| | - Daniel M Hirai
- Department of Health and Kinesiology, Purdue University, West Lafayette, IN, United States
| | - Steven W Copp
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States
| | - Scott K Ferguson
- Department of Kinesiology and Exercise Sciences, University of Hawaii, Hilo, HI, United States
| | - Clark T Holdsworth
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States; Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States
| | - K Sue Hageman
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States
| | - David C Poole
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States; Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States
| | - Timothy I Musch
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States; Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States
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11
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Smith JR, Hart CR, Ramos PA, Akinsanya JG, Lanza IR, Joyner MJ, Curry TB, Olson TP. Metabo- and mechanoreceptor expression in human heart failure: Relationships with the locomotor muscle afferent influence on exercise responses. Exp Physiol 2020; 105:809-818. [PMID: 32105387 DOI: 10.1113/ep088353] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 02/20/2020] [Indexed: 12/17/2022]
Abstract
NEW FINDINGS What is the central question of this study? How do locomotor muscle metabo- and mechanoreceptor expression compare in heart failure patients and controls? Do relationships exist between the protein expression and cardiopulmonary responses during exercise with locomotor muscle neural afferent feedback inhibition? What is the main finding and its importance? Heart failure patients exhibited greater protein expression of transient receptor potential vanilloid type 1 and cyclooxygenase-2 than controls. These findings are important as they identify receptors that may underlie the augmented locomotor muscle neural afferent feedback in heart failure. ABSTRACT Heart failure patients with reduced ejection fraction (HFrEF) exhibit abnormal locomotor group III/IV afferent feedback during exercise; however, the underlying mechanisms are unclear. Therefore, the purpose of this study was to determine (1) metabo- and mechanoreceptor expression in HFrEF and controls and (2) relationships between receptor expression and changes in cardiopulmonary responses with afferent inhibition. Ten controls and six HFrEF performed 5 min of cycling exercise at 65% peak workload with lumbar intrathecal fentanyl (FENT) or placebo (PLA). Arterial blood pressure and catecholamines were measured via radial artery catheter. A vastus lateralis muscle biopsy was performed to quantify cyclooxygenase-2 (COX-2), purinergic 2X3 (P2X3 ), transient receptor potential vanilloid type 1 (TRPV 1), acid-sensing ion channel 3 (ASIC3 ), Piezo 1 and Piezo 2 protein expression. TRPV 1 and COX-2 protein expression was greater in HFrEF than controls (both P < 0.04), while P2X3 , ASIC3 , and Piezo 1 and 2 were not different between groups (all P > 0.16). In all participants, COX-2 protein expression was related to the percentage change in ventilation (r = -0.66) and mean arterial pressure (MAP) (r = -0.82) (both P < 0.01) with FENT (relative to PLA) during exercise. In controls, TRPV 1 protein expression was related to the percentage change in systolic blood pressure (r = -0.77, P = 0.02) and MAP (r = -0.72, P = 0.03) with FENT (relative to PLA) during exercise. TRPV 1 and COX-2 protein levels are elevated in HFrEF compared to controls. These findings suggest that the elevated TRPV 1 and COX-2 expression may contribute to the exaggerated locomotor muscle afferent feedback during cycling exercise in HFrEF.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Corey R Hart
- Division of Endocrinology, Mayo Clinic, Rochester, MN, USA
| | - Paola A Ramos
- Division of Endocrinology, Mayo Clinic, Rochester, MN, USA
| | | | - Ian R Lanza
- Division of Endocrinology, Mayo Clinic, Rochester, MN, USA
| | | | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
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12
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Cheyne WS, Harper MI, Gelinas JC, Sasso JP, Eves ND. Mechanical cardiopulmonary interactions during exercise in health and disease. J Appl Physiol (1985) 2020; 128:1271-1279. [PMID: 32163324 DOI: 10.1152/japplphysiol.00339.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The heart and lungs are anatomically coupled through the pulmonary circulation and coexist within the sealed thoracic cavity, making the function of these systems highly interdependent. Understanding of the complex mechanical interactions between cardiac and pulmonary systems has evolved over the last century to appreciate that changes in respiratory mechanics significantly impact pulmonary hemodynamics and ventricular filling and ejection. Furthermore, given that the left and right heart share a common septum and are surrounded by the nondistensible pericardium, direct ventricular interaction is an important mediator of both diastolic and systolic performance. Although it is generally considered that cardiopulmonary interaction in healthy individuals at rest minimally affects hemodynamics, the significance during exercise is less clear. Adverse heart-lung interaction in respiratory disease is of growing interest as it may contribute to the pathogenesis of comorbid cardiovascular dysfunction and exercise intolerance in these patients. Similarly, heart failure represents a pathological uncoupling of the cardiovascular and pulmonary systems, whereby cardiac function may be impaired by the normal ventilatory response to exercise. Despite significant research contributions to this complex area, the mechanisms of cardiopulmonary interaction in the intact human and the clinical consequences of adverse interactions in common respiratory and cardiovascular diseases, particularly during exercise, remain incompletely understood. The purpose of this review is to present the key physiological principles of cardiopulmonary interaction as they pertain to resting and exercising hemodynamics in healthy humans and the clinical implications of adverse cardiopulmonary interaction during exercise in chronic obstructive pulmonary disease (COPD), pulmonary hypertension, and heart failure.
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Affiliation(s)
- William S Cheyne
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Megan I Harper
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Jinelle C Gelinas
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - John P Sasso
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Neil D Eves
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
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13
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Machado AC, Vianna LC, Gomes EAC, Teixeira JAC, Ribeiro ML, Villacorta H, Nobrega ACL, Silva BM. Carotid chemoreflex and muscle metaboreflex interact to the regulation of ventilation in patients with heart failure with reduced ejection fraction. Physiol Rep 2020; 8:e14361. [PMID: 32026605 PMCID: PMC7002537 DOI: 10.14814/phy2.14361] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 01/16/2023] Open
Abstract
Synergism among reflexes probably contributes to exercise hyperventilation in patients with heart failure with reduced ejection fraction (HFrEF). Thus, we investigated whether the carotid chemoreflex and the muscle metaboreflex interact to the regulation of ventilation ( V ˙ E ) in HFrEF. Ten patients accomplished 4-min cycling at 60% peak workload and then recovered for 2 min under either: (a) 21% O2 inhalation (tonic carotid chemoreflex activity) with legs' circulation free (inactive muscle metaboreflex); (b) 100% O2 inhalation (suppressed carotid chemoreflex activity) with legs' circulation occluded (muscle metaboreflex activation); (c) 21% O2 inhalation (tonic carotid chemoreflex activity) with legs' circulation occluded (muscle metaboreflex activation); or (d) 100% O2 inhalation (suppressed carotid chemoreflex activity) with legs' circulation free (inactive muscle metaboreflex) as control. V ˙ E , tidal volume (VT ) and respiratory frequency (fR ) were similar between each separated reflex (protocols a and b) and control (protocol d). Calculated sum of separated reflexes effects was similar to control. Oppositely, V ˙ E (mean ± SEM: Δ vs. control = 2.46 ± 1.07 L/min, p = .05) and fR (Δ = 2.47 ± 0.77 cycles/min, p = .02) increased versus control when both reflexes were simultaneously active (protocol c). Therefore, the carotid chemoreflex and the muscle metaboreflex interacted to V ˙ E regulation in a fR -dependent manner in patients with HFrEF. If this interaction operates during exercise, it can have some contribution to the HFrEF exercise hyperventilation.
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Affiliation(s)
- Alessandro C. Machado
- Laboratory of Exercise SciencesDepartment of Physiology and PharmacologyFluminense Federal UniversityNiteróiRJBrazil
- Latin American Institute of Life and Nature SciencesFederal University of Latin American IntegrationFoz do IguaçuPRBrazil
| | - Lauro C. Vianna
- Faculty of Physical EducationUniversity of BrasíliaBrasiliaDFBrazil
| | - Erika A. C. Gomes
- Laboratory of Exercise SciencesDepartment of Physiology and PharmacologyFluminense Federal UniversityNiteróiRJBrazil
| | - Jose A. C. Teixeira
- Antonio Pedro University HospitalFaculty of MedicineFluminense Federal UniversityNiteróiRJBrazil
| | - Mario L. Ribeiro
- Antonio Pedro University HospitalFaculty of MedicineFluminense Federal UniversityNiteróiRJBrazil
| | - Humberto Villacorta
- Antonio Pedro University HospitalFaculty of MedicineFluminense Federal UniversityNiteróiRJBrazil
| | - Antonio C. L. Nobrega
- Laboratory of Exercise SciencesDepartment of Physiology and PharmacologyFluminense Federal UniversityNiteróiRJBrazil
| | - Bruno M. Silva
- Department of PhysiologyFederal University of São PauloSão PauloSPBrazil
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14
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Koerber DM, Rosenbaum AN, Olson TP, Kushwaha S, Stulak J, Maltais S, Behfar A. Exercise-induced hypoxemia predicts heart failure hospitalization and death in patients supported with left ventricular assist devices. Int J Artif Organs 2019; 43:165-172. [PMID: 31630619 DOI: 10.1177/0391398819882435] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Following implantation of continuous-flow left ventricular assist devices, mechanical off-loading results in improved resting hemodynamics; however, peak exercise capacity generally does not increase substantially. This study evaluated patients supported by continuous-flow left ventricular assist devices who were invasively monitored during exercise to define parameters that underpin exercise capacity and outcomes. A review of all patients supported by continuous-flow left ventricular assist devices who underwent supine bicycle ergometry exercise testing with measurement of pulmonary gas exchange during right heart catheterization for evaluation of dyspnea at one institution between 2007 and 2018 was performed (n = 22). The primary outcome of this investigation was death or heart failure hospitalization. Although resting filling pressures were relatively preserved, resting cardiac index (Fick) was low (2.1 ± 0.5 mL/kg/min). An impaired cardiac output reserve was present in 75% of patients. On univariate modeling, patients with supine exercise-induced hypoxemia (O2 saturation <90%) experienced significantly diminished hospitalization-free survival (unadjusted hazard ratio = 11.0, confidence interval = 2.4-57.2, p = 0.003), which persisted despite adjustment for right heart catheterization peak VO2 and peak cardiac output (adjusted hazard ratio = 25, confidence interval = 3.6-322, p = 0.001). Our findings suggest that supine exercise testing provides additional prognostic utility in the continuous-flow left ventricular assist device population.
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Affiliation(s)
- Daniel M Koerber
- Van Cleve Cardiac Regenerative Medicine Program, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA
| | | | - Thomas P Olson
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA
| | - Sudhir Kushwaha
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.,William J. von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, MN, USA
| | - John Stulak
- Department of Cardiovascular Surgery, Mayo Clinic, Rochester, MN, USA
| | - Simon Maltais
- Department of Cardiovascular Surgery, Mayo Clinic, Rochester, MN, USA
| | - Atta Behfar
- Van Cleve Cardiac Regenerative Medicine Program, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.,William J. von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, MN, USA
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15
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Smith JR, Johnson BD, Olson TP. Impaired central hemodynamics in chronic obstructive pulmonary disease during submaximal exercise. J Appl Physiol (1985) 2019; 127:691-697. [PMID: 31295068 DOI: 10.1152/japplphysiol.00877.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is unknown whether central hemodynamics are impaired during exercise in chronic obstructive pulmonary disease (COPD) patients. We hypothesized that, at a similar absolute V̇o2 during exercise, COPD patients would have a lower stroke volume and cardiac output compared with healthy controls. Furthermore, we hypothesized that greater static hyperinflation [ratio of inspiratory capacity to total lung capacity (IC/TLC)] and expiratory intrathoracic pressure would be significantly related to the lower cardiac output and stroke volume responses in COPD patients. Clinically stable COPD (n = 13; FEV1/FVC: 52 ± 13%) and controls (n = 10) performed constant workload submaximal exercise at an absolute V̇o2 of ~1.3 L/min. During exercise, inspiratory capacity maneuvers were performed to determine operating lung volumes and cardiac output (via open-circuit acetylene rebreathe technique) and esophageal pressure were measured. At similar absolute V̇o2 during exercise (P = 0.81), COPD had lower cardiac output than controls (COPD: 11.0 ± 1.6 vs. control: 12.2 ± 1.2 L/min, P = 0.03) due to a lower stroke volume (COPD: 107 ± 13 vs. control: 119 ± 19 mL, P = 0.04). The heart rate response during exercise was not different between groups (P = 0.66). FEV1 (%predicted) and IC/TLC were positively related to stroke volume (r = 0.68, P = 0.01 and r = 0.77, P < 0.01). Last, esophageal pressure-time integral during inspiration was positively related to cardiac output (r = 0.56, P = 0.047). These data demonstrate that COPD patients have attenuated cardiac output and stroke volume responses during exercise compared with control. Furthermore, these data suggest that the COPD patients with the most severe hyperinflation and more negative inspiratory intrathoracic pressures have the most impaired central hemodynamic responses.NEW & NOTEWORTHY Chronic obstructive pulmonary disease leads to cardiac structural changes and pulmonary derangements that impact the integrative response to exercise. However, it is unknown whether these pathophysiological alterations influence the cardiac response during exercise. Herein, we demonstrate that COPD patients exhibit impaired central hemodynamics during exercise that are worsened with greater hyperinflation.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
| | - Bruce D Johnson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
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16
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Barbosa GW, Müller PDT. Non‐COPD smokers: The occult face behind exercise physiology in heart failure. Exp Physiol 2019; 104:775-776. [PMID: 31034115 DOI: 10.1113/ep087584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 01/22/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Gisele Walter Barbosa
- Laboratory of Respiratory Pathophysiology (LAFIR)Maria A. Pedrossian University HospitalFederal University of Mato Grosso do Sul, Campo Grande Mato Grosso do Sul Brazil
| | - Paulo de Tarso Müller
- Laboratory of Respiratory Pathophysiology (LAFIR)Maria A. Pedrossian University HospitalFederal University of Mato Grosso do Sul, Campo Grande Mato Grosso do Sul Brazil
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17
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Smith JR, Olson TP. Reply to Barbosa and Müller. Exp Physiol 2019; 104:777-778. [PMID: 31034116 DOI: 10.1113/ep087618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 02/18/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Joshua R. Smith
- Department of Cardiovascular MedicineMayo Clinic Rochester MN USA
| | - Thomas P. Olson
- Department of Cardiovascular MedicineMayo Clinic Rochester MN USA
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18
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Effects of bi-level positive airway pressure on ventilatory and perceptual responses to exercise in comorbid heart failure-COPD. Respir Physiol Neurobiol 2019; 266:18-26. [PMID: 31005600 DOI: 10.1016/j.resp.2019.04.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 03/28/2019] [Accepted: 04/18/2019] [Indexed: 12/11/2022]
Abstract
This study tested the hypothesis that, by increasing the volume available for tidal expansion (inspiratory capacity, IC), bi-level positive airway pressure (BiPAP™) would lead to greater beneficial effects on dyspnea and exercise intolerance in comorbid heart failure (HF)-chronic obstructive pulmonary disease (COPD) than HF alone. Ten patients with HF and 9 with HF-COPD (ejection fraction = 30 ± 6% and 35 ± 7%; FEV1 = 83 ± 12% and 65 ± 15% predicted, respectively) performed a discontinuous exercise protocol under sham ventilation or BiPAP™. Time to intolerance increased with BiPAP™ only in HF-COPD (p < 0.05). BiPAP™ led to higher tidal volume and lower duty cycle with longer expiratory time (p < 0.05). Of note, BiPAP™ improved IC (by ∼0.5 l) across exercise intensities only in HF-COPD. These beneficial consequences were associated with lower dyspnea scores at higher levels of ventilation (p < 0.05). By improving the qualitative" (breathing pattern and operational lung volumes) and sensory (dyspnea) features of exertional ventilation, BiPAP™ might allow higher exercise intensities to be sustained for longer during cardiopulmonary rehabilitation in HF-COPD.
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Smith JR, Borlaug BA, Olson TP. Exercise Ventilatory Efficiency in Older and Younger Heart Failure Patients With Preserved Ejection Fraction. J Card Fail 2019; 25:278-285. [PMID: 30822511 DOI: 10.1016/j.cardfail.2019.02.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/31/2019] [Accepted: 02/20/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND Patients with heart failure with preserved ejection fraction (HFpEF) exhibit pulmonary abnormalities, but the studies to date have reported wide variability in the ventilatory equivalent for carbon dioxide (V̇E/V̇CO2) slope. It is possible that aging may contribute to that variability. We sought to compare ventilatory efficiency and its components in older and younger HFpEF patients during exercise. METHODS AND RESULTS Eighteen older (O; 80 ± 4 y) and 19 younger (Y; 59 ± 7 y) HFpEF patients performed cardiopulmonary exercise testing to volitional fatigue. Measurements of arterial blood gases were used to derive VD/VT, dead space ventilation, and alveolar ventilation. V̇E/V̇CO2 slope was greater in older compared with younger HFpEF patients (O 36 ± 7vs Y 31 ± 7; P = .04). At peak exercise, older HFpEF exhibited greater VD/VT compared with younger HFpEF (O 0.37 ± 0.10vs Y 0.28 ± 0.10; P < .01), whereas PaCO2 was not different between groups (P = .58). V̇E and alveolar ventilation were similar (P > .23), but dead space ventilation was greater in older compared with younger HFpEF at peak exercise (P = .04). CONCLUSIONS Older HFpEF patients exhibit greater ventilatory inefficiency resulting from elevated physiologic dead space during peak exercise compared with younger HFpEF patients. These results suggest that aging can worsen the pathophysiologic mechanisms underlying ventilatory efficiency during exercise in HFpEF.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota.
| | - Barry A Borlaug
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
| | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
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