Skip to 0 minutes and 7 seconds Welcome to another of the Home Practicals. My name’s Dr Natasha Barrett, and I’ll be leading today’s practical. Hopefully you’ve already read the information about risks associated with this practical and how to minimise them. If you haven’t, then please take a few minutes to do so. It won’t take long. Before we start the practical, we’ll run through the aims, recap the theory, and then go through the checklist of items required. The purpose of practical work is to apply the theory that you’ve already covered. And this helps deepen your understanding of the topic. The aims of today’s practical are to investigate the effects of heart failure.
Skip to 0 minutes and 47 seconds So by the end of the practical, you should have a better understanding of the effects of heart failure, including the adaptations that the heart makes. You should also understand two terms, stroke volume and cardiac output, that I’ll introduce in a moment. So let’s start by recapping the theory. Heart failure is the progressive failing of the heart as a mechanical pump, and this is caused by damage to the heart, for example, acute damage, like a heart attack, or prolonged over work, like long term hypertension or valvular diseases. As the heart can’t fully rest and recover, instead it undergoes several adaptations that help it prolong its function for as long as possible.
Skip to 1 minute and 31 seconds Many of these adaptations are very similar to those that a healthy heart undergoes with regular cardiovascular exercise. And we’ll explore those during the practical. I also said I’d introduce two terms, stroke volume and cardiac output. Stroke volume is the volume of blood that a heart pumps with each contraction, or each squeeze, whilst cardiac output is the volume of blood that the heart pumps per minute. If you know the volume it pumps with each squeeze, and you know the number of times it squeezes or contracts in a minute, or the heart rate, you can calculate the cardiac output by multiplying the two together. We’ll be looking at these two terms through the practical, so they’ll become more familiar.
Skip to 2 minutes and 19 seconds Let’s run through the checklist of items that we’ll need for this practical. Of course, you’ll need your instruction sheet. Perhaps you’re working from a mobile device instead, in which case do make sure it’s adequately protected by placing it inside a clear plastic bag, as we are working with lots of water today. You’ll also need your worksheet, or a piece of paper on which to make your notes, and a pen to write with. It’s useful to have a spill tray to collect any spilt water and protect the area. And I’m wearing a lab coat to protect my clothes, as I’m working in a laboratory. I don’t need to wear gloves or goggles today, as it’s not deemed necessary.
Skip to 3 minutes and 3 seconds At home, I’d suggest you just wear an apron to protect your clothes. We’re going to need a measuring jug, and we’re going to fill it up with water. I’d recommend a 1 litre or 1,000 millilitre measuring jug, and it needs to have the 100 millilitre markers on the side. A 500 millilitre jug will do as well. Perhaps most importantly, we’re going to need a small hand pump. This is one from a liquid soap dispenser. At the end of the practical, you can return it to the soap dispenser, as it won’t be damaged in any way. You’re also going to need another container, such as a beaker or a glass, for when we transfer the water from one to the other.
Skip to 3 minutes and 49 seconds It’s helpful if you’ve got a calculator, as we’ll be doing quite a few calculations during this practical. Finally, we’ll need all the cleaning up equipment, for example, lots of hot, soapy water to wash all our equipment and to wash our hands, plenty of tissue or cloths to mop up any spills of water, and a disinfectant to wipe down the surface at the end. Lastly, I’d recommend having a waste bag so you can put any waste generated into it. So run through the checklist once more, and when you’re ready, we can begin.
Investigating the effects of cardiovascular stress: An introduction
There are two terms that we need to be familiar with for this practical, stroke volume and cardiac output.
Stroke volume is the volume of blood that the heart pumps with each contraction, and cardiac output is the volume of blood pumped per minute, so:
Cardiac output = stroke volume x heart rate
A list of items needed to perform this practical can be found in the previous step as well as alongside step-by-step instructions for the practical in the downloadable Week 3 home practical guide.
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