AUTHOR=Borghi-Silva Audrey , Goulart Cassia da Luz , Carrascosa Cláudia R. , Oliveira Cristino Carneiro , Berton Danilo C. , de Almeida Dirceu Rodrigues , Nery Luiz Eduardo , Arena Ross , Neder J. Alberto 

TITLE=Proportional Assist Ventilation Improves Leg Muscle Reoxygenation After Exercise in Heart Failure With Reduced Ejection Fraction

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.685274

DOI=10.3389/fphys.2021.685274

ISSN=1664-042X

ABSTRACT=<sec><title>Background</title><p>Respiratory muscle unloading through proportional assist ventilation (PAV) may enhance leg oxygen delivery, thereby speeding off-exercise oxygen uptake (<inline-formula><mml:math id="INEQ1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula>) kinetics in patients with heart failure with reduced left ventricular ejection fraction (HFrEF).</p></sec><sec><title>Methods</title><p>Ten male patients (HFrEF = 26 ± 9%, age 50 ± 13 years, and body mass index 25 ± 3 kg m<sup>2</sup>) underwent two constant work rate tests at 80% peak of maximal cardiopulmonary exercise test to tolerance under PAV and sham ventilation. Post-exercise kinetics of <inline-formula><mml:math id="INEQ2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula>, vastus lateralis deoxyhemoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy, and cardiac output (Q<sub><italic>T</italic></sub>) by impedance cardiography were assessed.</p></sec><sec><title>Results</title><p>PAV prolonged exercise tolerance compared with sham (587 ± 390 s vs. 444 ± 296 s, respectively; <italic>p</italic> = 0.01). PAV significantly accelerated <inline-formula><mml:math id="INEQ3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> recovery (<italic>τ</italic> = 56 ± 22 s vs. 77 ± 42 s; <italic>p</italic> &lt; 0.05), being associated with a faster decline in Δ[deoxy-Hb + Mb] and Q<sub><italic>T</italic></sub> compared with sham (<italic>τ</italic> = 31 ± 19 s vs. 42 ± 22 s and 39 ± 22 s vs. 78 ± 46 s, <italic>p</italic> &lt; 0.05). Faster off-exercise decrease in Q<sub><italic>T</italic></sub> with PAV was related to longer exercise duration (<italic>r</italic> = −0.76; <italic>p</italic> &lt; 0.05).</p></sec><sec><title>Conclusion</title><p>PAV accelerates the recovery of central hemodynamics and muscle oxygenation in HFrEF. These beneficial effects might prove useful to improve the tolerance to repeated exercise during cardiac rehabilitation.</p></sec>