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Thursday, September 2, 2010

Heart Failure: Everything RT's need to know

To understand Congestive Heart Failure (CHF) you must understand the heart. I am sure you know this already, but for those who want a review, this should suffice.

You effectively have two hearts. Your right heart is responsible for pumping blood through your lungs, and your left heart is responsible for pumping blood through your entire body, including your heart and lungs. Your right heart is a relatively small pump that generates a light pressure to pump blood, and the left heart is a strong pump that generates a strong pressure needed to pump blood through the rest of the body.

The right heart is a smaller pump that generates a pressure of about 15. That's all that is needed to pump blood through healthy, compliant lungs. The left heart is a bigger pump that generates a pressure of about 120/80. This is what is needed to push blood through the body. Nothing new here.

You can have a diagnosis of heart failure and have no symptoms on a day to day basis. However, as your heart becomes a weaker pump, you may present with symptoms, such as noted above. The symptoms may present similar to asthma and COPD, and may include dyspnea and wheezing. Usually, but not always, the wheeze is upper airway, and it's frequently audible.

Congestive Heart failure usually refers to a is a condition where the left heart becomes unable to pump blood through the body. It is unable to fully oxygenate tissues and organs that work to keep the body functioning as a system. Without adequate blood flow, tissues and organs will fail to perform their jobs, and the body will die.

When a heart is in failure it is unable to maintain an adequate...

Cardiac Output (CO). This is the volume of blood pumped from the heart per minute. CO is the product of both the stroke volume and heart rate. An easy way of measuring CO is blood pressure. It can also be indirectly measured by feeling for a pulse. So, these are just some simple ways we check CO. It can also be checked with a pulse oximeter. If the pulse ox reading is low, a low CO may be the reason. This is important, because when a person is on too high a PEEP, CO is the first thing to be affected. You lower PEEP you increase CO. Okay, enough about that. Moving on.

Stroke Volume (SV). This is the volume of blood pumped from the heart per beat. This is determined by CO minus heart rate times stroke volume.

Heart Rate (HR). This is simply the number of heartbeats per minute. Easy enough. We check this all the time.

So, by using the formula above, you can see that cardiac output is affected by anything that decreases the heart rate or decreases the strength of the heart, or the ability of the heart to constrict and force blood to the lungs or body will decrease the amount of blood leaving the heart.

Afterload. This is blood leaving the heart.

Preload. This is blood entering the heart.

Without doing extensive testing, an easy way to measure cardiac output is by taking a blood pressure. And the even easier way is by simply taking a pulse. Since a pulse oximeter measures oxygen saturation using a pulse, a decreasing oxygen saturation can also be an indicator of decreased cardiac output. So, there I said it twice now. So, you should never forget it.

As heart failure progresses, and as the heart becomes too weak to effectively pump blood through the body, blood will back up into the vessels in the lungs, thus increasing the...

Pulmonary vascular resistance. This is the blood pressure in the lungs. As this increases, blood will seep out of the blood vessels and into the lungs, causing...

Pulmonary edema. This is fluid in the lungs. It often appears as pink and frothy. If you see this coming ouf of a person's nose and mouth, it is not a good sign. I have rarely seen this in a person who survived. Thankfully, I have not seen this in many years. So, this probably means heart failure is being treated better today than when I first arrived on the scene back in 1995.

Increased pulmonary vascular resistance actually squeezes airways, causing them to become narrow. This is why heart failure may mimic asthma, as this causes a wheeze. This is called a cardiac wheeze. It's quite often audible, as fluid may be pushed to the upper airway and sit on the vocal cords. Nurses and doctors like to think this is bronchospasm. But, it's not.

Fluid is also squeezed out of blood vessels into the intrapulmonary spaces. Some of these secretions may work their way up to the upper airways and sit by the vocal cords, thereby causing that forced, audible expiratory wheeze so commonly heard among the heart failure community. This is called a cardiac wheeze, and it used to be called cardiac asthma. This wheeze cannot be treated with a breathing treatment, although this too often is attempted.

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