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Related Concept Videos

ATP Driven Pumps III: V-type Pumps01:30

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V-type pumps are ATP-driven pumps found in the vacuolar membranes of plants, yeast, endosomal and lysosomal membranes of animal cells, plasma membranes of a few specialized eukaryotic cells, and some prokaryotes. They are also known as the V1Vo-ATPase, that couple ATP hydrolysis to transport protons against a concentration gradient.
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ATP Driven Pumps II: P-type Pumps01:34

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The P-type pumps are a large family of integral membrane transporter ATPases. They are divided into five major types based on substrate specificity, from I to V.
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
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Increasing Function01:18

Increasing Function

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An increasing function exhibits a rise in output values as input values increase. This behavior is depicted graphically as a curve or line that slopes upward from left to right. Such a function satisfies the condition that if x1 < x2, then f(x1) < f(x2), indicating that the function values grow with increasing inputs. This concept is fundamental in understanding growth trends across various domains, such as population dynamics, financial investments, or resource consumption.The...
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Pumped Concrete01:13

Pumped Concrete

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Concrete in large quantities can be pumped across long distances for placing in inaccessible sites. This system comprises a hopper that receives concrete from a mixer, a pump to propel the concrete, and pipelines that facilitate its delivery.
For direct-acting pumps, the concrete enters the pump via the inlet valve under the action of gravity and suction created by the movement of the piston. This concrete is then forced into the pipeline and out through the outlet valve by the forward movement...
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Refrigerators and Heat Pumps01:07

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Refrigerators or heat pumps are heat engines operating in a reverse direction. For a refrigerator, the focus is on removing heat from a specific area, whereas, for a heat pump, the focus is on dumping heat into one particular area. A refrigerator (or heat pump) absorbs heat Qc from the cold reservoir at Kelvin temperature Tc and discards heat Qh to the hot reservoir at Kelvin temperature Th, while work W is done on the engine’s working substance.
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Exercise Stress Test01:26

Exercise Stress Test

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Introduction
Exercise stress testing, commonly known as a treadmill test, is a noninvasive procedure used to evaluate cardiovascular function and diagnose heart conditions.
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A Swimming-Induced Zebrafish Exercise Apparatus for Versatile Training Approaches
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LVAD Pump Flow Does Not Adequately Increase With Exercise.

Christoph Gross1,2, Christiane Marko3, Johann Mikl4

  • 1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.

Artificial Organs
|August 30, 2018
PubMed
Summary
This summary is machine-generated.

Constant speed left ventricular assist devices (LVADs) offer insufficient support during maximal exercise. Aortic valve opening and heart rate response, not pump flow, influence peak oxygen uptake, suggesting speed control could improve strenuous activity support.

Keywords:
Cardiac rehabilitationCardiac responseExerciseLeft ventricular assist deviceMechanical circulatory support

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Area of Science:

  • Cardiovascular Science
  • Biomedical Engineering
  • Exercise Physiology

Background:

  • Left ventricular assist devices (LVADs) augment cardiac output but their performance during varying exercise intensities remains understudied.
  • Understanding LVAD and native heart interactions during exercise is crucial for patient rehabilitation and quality of life.

Purpose of the Study:

  • To investigate the impact of exercise intensity on LVAD pump flow, heart rate, and aortic valve opening.
  • To determine the relationship between these parameters and peak oxygen uptake (pVO2) during maximal exercise.

Main Methods:

  • Continuous monitoring of LVAD flow rate (QLVAD), heart rate (HR), and aortic valve (AV) opening in 16 patients during maximal (bicycle ergometer) and submaximal (6-min walk, training) exercise.
  • Multi-regression analysis to identify predictors of pVO2.

Main Results:

  • QLVAD responses were similar across exercise intensities, but HR and AV opening differed significantly between maximal and submaximal exercise.
  • AV opening occurred in 71% of patients during maximal exercise versus 23% during submaximal exercise.
  • pVO2 was significantly associated with workload, HR response, AV opening, and age, but not with changes in QLVAD.

Conclusions:

  • Constant speed LVADs may not provide adequate hemodynamic support for maximal physical exertion.
  • Aortic valve opening and heart rate augmentation are key indicators of exercise capacity and intensity in LVAD patients.
  • Optimizing LVAD speed control could enhance circulatory support during strenuous activities, potentially improving exercise performance.