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Heart Rate being normal when under treatment for the bends

Heart Rate being normal when under treatment for the bends



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When you surface from diving too quickly; you get "bends" - these are caused by gas bubbles forming in your lungs (especially nitrogen). This causes breathing problems if not treated since the bubbles are essentially blocking oxygen transport.

For treatment, you have to be in a hyperbaric chamber for several hours.

Why is it you don't get nitrogen and carbon dioxide bubbles in your bloodstream while being treated? I would think that in the machine the nitrogen, carbon dioxide and water concentrations would rise causing you to start having signs of low oxygen like loss of brain function.

As I stated previously, nitrogen bubbles block oxygen transport and thus carbon dioxide transport. Since there is nowhere else to go, it goes into the bloodstream where oxygenated blood is supposed to be. This is detected by the chemoreceptors in your arteries; this then tells the heart to beat faster in attempts to rid the body of CO2. Once again; however, this doesn't happen because now there are more nitrogen bubbles from breathing in more nitrogen and water. This leads to a progressively higher heart rate (Ventricular Tachycardia - V-tach) which is dangerous as it can lead to MI (Myocardial Infarction) symptoms - like chest pain. Ventricular tachycardia that lasts a maximum of a few minutes can then lead to V-fib (Ventricular Fibrillation) which, if not treated with epinephrine or defibrillation on time, will lead to asystole and death.

Summary:

When someone has the bends and is being treated in a hyperbaric chamber; how do they not end up having an acute MI (due to accumulation of nitrogen gas in the bloodstream)?


You are wrong on several accounts:

  1. Bends occur due to bubbles that form in muscles and joints and not lungs - They fall under Mild or Type 1 Decompression Sickness (Type 1 DCS).
  2. Formation of bubbles in blood stream do occur in the Decompression process - Hyperbaric chamber is used to treat this condition.

What happens when diving:

During deep sea diving the pressure surrounding a person increases at the rate of 1 atm (atmospheric pressure) for every 10 m in sea water and 10.3 m in fresh water. This relation is linear.

The pressure inside the body equalises with the pressure outside to prevent any deformation. The solid and liquid components of the body can withstand pressures upto 151 atm (depth of 1.5 km underwater) without undergoing any noticeable compression. But air, being extremely compressible undergoes compression.

So at 2 atmospheric pressure the space occupied by the air in our body is halved. This would shrink the lungs to half the total volume. To circumvent this the divers breathe air compressed at the same pressure as the water pressure around them, so that the pressure gradient across the chest wall is normal.

Pressure Concentration relationship:

Dalton's Law:

This law states that the Barometric Pressure is the sum of the partial pressures of the individual gases in the air mixture.

Barometric Pressure - The total pressure measured

In air at 1 atmospheric pressure (760 mm Hg) the partial pressures of various gases are:

  • Nitrogen ~ 593 mm Hg
  • Oxygen ~ 159 mm Hg
  • Co2 ~ 0.2 mm Hg
  • Others ~ 7 mm Hg

According to this Law, as the pressure inside the Lungs increase, the partial pressures of each gas increases. At 2 atm, the partial pressures of every gas doubles.

The gas exchange in the lungs is based on partial pressure of the gases. Thus due to increased partial pressure, the amount of gases dissolved in blood increases (This increase is proportionate to the pressure levels).

During a extended dive (one lasting several hours) the body tissues gradually equilibriate with the high-pressure gases. At sea level our body contains 1 L of dissolved nitrogen, equally distributed between body's water and fat. As partial pressure of Nitrogen rises, the nitrogen equilibriates with the body's lipid stores because adipose tissue is relatively underperfused.

Once equilibrium is achieved the volume of nitrogen dissolved in tissues is proportional to the alveolar partial pressure of nitrogen. Thus at 4 atm the body will contain 4 L of nitrogen.

The same principle applies to oxygen as well, though the solubility of oxygen and the speed at which equilibrium is attained are different.

Decompression

During ascent from the depths, the Barometric Pressure (surrounding pressure Pb) falls. As the Pb falls the pressure inside the alveoli fall as well. This causes a fall in the partial pressures of all gases in the lungs creating a gradient of gases from the tissues to the alveoli.

So the diver has to ascend slowly to give enough time for the gases to move into blood from the tissues and then get washed out. If the ascent is too rapid, gases dissolved in the tissues - due to high pressure - attains the gaseous form (due to pressure drop) and become bubbles. This is similar to opening a pressurised coke can where one can observe gas bubbles forming.

The bubbles are the reason for the bends. Bubbles can also cause serious problems like arterial gas embolisation, CNS disorders (due to formation of bubbles in the myelin sheath of axons which compromise nerve conduction), pulmonary symptoms (due to pulmonary emboli), sometimes even Disseminated Intravascular Coagulation.

Solution

The decompression is done in stages - in which the divers spend various amount of time at various under water levels to allow complete diffusion of dissolved gases into blood and into the alveoli which is consequently breathed out.

Hyperbaric Chamber

The hyperbaric chamber is used when the above solution is not applied i.e. the diver has surfaced rapidly without spending sufficient time at various levels to allow proper decompression.

In a hyperbaric chamber the diver is recompressed to the pressures equal to the pressure experienced at the level to which the diver dived. Due to the increase in pressure, the bubbles get dissolved again. This instantly relieves many symptoms - like the nerve conduction delay, bends, niggles etc… Now the decompression is carried out by under controlled environment, simulating the various intervals the diver has to stay at various pressure levels under water.

Hope this explains your doubt.

So coming to myocardial infarction, the hyperbaric chamber redissolves the gas bubbles thus preventing myocardial infarction.


For more info read chapter 61 of Medical Physiology, 2nd edition, by Walter F. Boron and Emile L. Boulpaep.


Tachycardia is a heart rate of more than 100 beats per minute. The heart normally beats at a rate of 60 to 100 times per minute, and the pulse (felt at the wrist, neck or elsewhere) matches the contractions of the heart's ventricles, the heart's two powerful lower chambers.

Tachycardia can be part of the body's normal response to anxiety, fever, rapid blood loss or strenuous exercise. It also can be caused by medical problems, such as an abnormally high level of thyroid hormones, called hyperthyroidism. In some people, tachycardia is the result of a cardiac arrhythmia (a heart-generated abnormality of heart rate or rhythm). Tachycardia can also be caused by lung problems, such as pneumonia or a blood clot in one of the lung's arteries.

In other cases, tachycardia can be a side effect of some foods and drinks, including coffee, tea, alcohol and chocolate tobacco or medication.


"Normal" Values

At rest, the sinus node typically generates electrical impulses at a rate of between 60 and 100 times per minute. A resting heart rate within this range is called normal sinus rhythm.

Sinus bradycardia is a heart rate between 50 to 60 beats per minute. While technically out of the normal range, these values can be completely normal for some people. A healthy body is very good at regulating the heart rate to be whatever it needs to be to support the body’s functions. And often, that is within this range.

This is considered a physiologic form of sinus bradycardia. In other words, the heart rate is appropriate to the body’s requirements and is not of concern.

Healthy young people and even older people in good physical condition will frequently have resting heart rates in the 40s or 50s. It is also common (and normal) for many people to have heart rates in this range while sleeping.

It is only when the rate becomes so slow that not enough blood is being pumped by the heart that sinus bradycardia is considered abnormal and needs to be treated. Sinus bradycardia that is producing symptoms is a sign of this.


How do you take these readings?

Stromberg: At the Zoo, we are big advocates of positive reinforcement training, which gives our animals the option to choose to participate in their own care. These interactive training sessions also help build trusting relationships between the animals and us. They know that if they do the behavior asked of them correctly, they will receive a reward — usually a combination of food and an emphatic “good job” from their keeper.

To take the orangutans’ and gorillas’ ECG measurements, I hook my phone up to a pad with built-in electrodes. To get a proper reading, the apes must reach their fingers through the mesh, place them on the electrodes and hold them there for 30 seconds. While they sit still, I reward them with dilute juice from a squeeze bottle. They don’t seem to mind the phone at all — between keepers and visitors, they are very familiar with them!

Nub Armstrong’s process is a bit different. To get his blood pressure reading, I will put a cuff around the base of his tail and inflate it. Then, when it comes time from the glucose reading, we prick the skin of his tail to get a drop of blood. He is one of the most stoic and patient monkeys I’ve ever worked with, which makes him an ideal candidate for this training. No matter the situation, if there are peanuts in play, he is dedicated and focused on the task at hand.


Irregular Heartbeat (Arrhythmia) In Children

Change in the heart rate is normal. When your children are physically active, their heart rate is usually higher. And when they are resting, it could be lower. Likewise, the child’s heart rate can increase considerably during strenuous exercises.

But when the heart’s rhythm or rate changes drastically without any physiological triggers, it is abnormal. This condition is called arrhythmia or irregular heartbeat. This could indicate a heart problem or other underlying medical conditions. A fast heart rate might be accompanied by palpitations (noticeable sudden, rigid heartbeat), dizziness, and sometimes fainting (3).


Biological Factors Affecting Heart Rate

There are several different kinds of heart rates, starting with your resting heart rate. That's the number of times your heart beats in one minute when your body is in a state of rest and calm, explains the American Heart Association (AHA). The average resting heart rate is 60 to 100 beats a minute, but which side of that spectrum your own heart rate leans toward says a lot about your health.

"Multiple factors can affect a person's resting heart rate, including age, sex, level of physical conditioning and any medical and cardiac diseases they may have," says Vasundhara Muthu, MD, a cardiologist with the University of Maryland Medical System in the Baltimore area.

Fitness can affect your heart rate in a variety of ways: The more fit you are, the lower your resting heart rate tends to be, the AHA explains.

Two other types of heart rates — maximum heart rate and target heart rate — come into play when you get your heart pumping during a workout. Maximum heart rate (calculated by subtracting your age from 220) is your heart's limit during exercise, Mayo Clinic says. And your target heart rate — 50 to 70 percent of your max heart rate for moderate-intensity exercise, and 70 to 85 percent for vigorous activity — strikes the balance between having a fit heart versus an overworked heart.

So, how do you know where within these ranges your heart rate will land during a workout? "The rise in heart rate with physical activity will depend predominantly on the level of physical conditioning and your heart and lung health," explains Dr. Muthu.

Any underlying health conditions you may have, such as chronic heart and lung diseases, can play a role in heart rate elevations and irregularities, Dr. Muthu adds. These can also include anemia, thyroid disorders, fever, infections, pain as well as anxiety and other psychiatric conditions, she explains.


Outlook / Prognosis

What’s the outlook for someone with altitude sickness?

Most people who get altitude sickness get the mild form. Once you return to a lower elevation (or stay at your current elevation without climbing higher), symptoms improve.

Are there long-term effects of altitude sickness?

If you take care and move to a lower elevation when you feel symptoms, altitude sickness has no long-term negative effects. You’ll recover within a few days. Once you feel better, you can continue to travel to higher elevations, as long as you do so slowly and carefully.

Can altitude sickness be fatal?

In rare cases, altitude sickness can be life-threatening. If you develop HAPE or HACE, you are at risk for complications such as coma or even death. Get treatment as soon as possible to reduce your risk.

Can altitude sickness be cured?

Altitude sickness is temporary. Once you return to a lower altitude, you’ll feel better. When you begin your ascent again (or on your next climb), make sure to travel slowly to let your body acclimate.


Protons vs. X-rays

X-rays are electronic waves that penetrate tissue, gradually losing energy as they move along. To penetrate deeply enough in the body to reach most tumors, higher doses of radiation must be used. With X-ray therapy, however, the highest radiation dose occurs shortly after entering the body meaning that much of the radiation is deposited in the healthy tissue in front of the tumor. When the X-ray exits the tumor, it continues to affect healthy tissue as it leaves the body. That can cause a variety of short- and long-term side effects, some of which can seriously affect quality of life and health.

Protons are particles that can be manipulated to release their energy at a precise point. The more energy, the deeper the protons can penetrate into the body. The amount of proton energy is calculated to release the proton radiation precisely at the tumor site. The peak of this radiation dose (called the Bragg Peak) is designed to conform to the back of the tumor. Immediately after that point, the radiation dose falls to zero. Less of the radiation affects the healthy tissue in front of the tumor, and virtually none of it affects the healthy tissue behind the tumor. That results in much less damage to healthy tissue or nearby organs and structures. It also means that a higher dose often can be delivered, leading to more effective treatment.

With X-ray radiation therapy (black line), the radiation dose peaks soon after entering the body and often, long before reaching the tumor, gradually decreases. Healthy tissue surrounding the tumor receives much of the dose. With proton therapy (blue lines), treatment conforms more closely to the tumor, so that less radiation is deposited in the healthy tissue in front of the tumor compared to X-ray therapy, and almost none is deposited in the healthy tissue behind the tumor.Source: ProCure Treatment Centers Inc.


Fast Heart Rate – Symptoms, Causes and Treatments

A fast heart rate is known as tachycardia and commonly defined as a heart rate greater than 100 beats per minute. Although a fast heart rate is commonly defined as a heart rate greater than 100 beats per minute, there is no specific cut off for what defines a significantly fast heart rate or a number above which a fast heart rate becomes an issue. Each case is different and needs to be approached differently. Articles on normal heart rate and low heart rate are linked here.

What Causes A Fast Heart Rate?

The heart rate can be fast for reasons inside the heart or reasons outside the heart.

The electrical system of the heart itself can cause a fast heart rate if there are ‘short circuits’ that occur within it. These are known as tachyarrhythmias. These can occur from the top chamber or the bottom chamber of the heart. Fast heart rates from the top chamber of the heart are known as supraventricular tachycardia or SVT for short. They can be regular or irregular. One of the most common causes for a fast heart rate, especially if irregular in nature is known as atrial fibrillation or AF for short. Fast heart rates that occur from the bottom chamber of the heart are known as ventricular tachycardia or VT for short. These are generally regular in nature. Ventricular Tachycardia is considered more concerning in general than other causes of fast heart rate and needs prompt work up and attention.

The heart rate may be fast simply as a reaction to other processes going on in the body. For example, if the body is under stress from pain, infection, blood loss or general illness then the heart rate may increase significantly, often to provide blood to vital organs. When someone has pain, there is an increase in secretion of stress hormones that directly increases heart rate through acting on receptors in the heart. There may be problems with hormones such as overproduction of thyroid hormone that may lead to increase in heart rate. When the body is in shock, be it for reasons from inside or outside the heart, the heart rate will increase significantly. For example if the heart function is severely impaired and the amount of blood being pumped out per beat is therefore reduced, the heart attempts to compensate by increasing the rate. Finally its important to note that ingestion of substances such as stimulants that would directly increase heart rate need to be ruled out as a cause of fast heart rate.

Symptoms of a Fast Heart Rate

Many people don’t have symptoms when they find out they have a fast heart rate. They often just notice it when checking their pulse rate, or from a blood pressure machine or a Fitbit type accessory. Some patients may feel tired, short of breath, dizzy or fatigued. If the heart rate is particularly fast people may notice a thumping sensation or palpitations. If the heart rate is particularly fast, there may be a sensation of light-headedness or feeling of faintness. In the case of SVT that comes and goes at unpredictable times, there may be intermittent palpitations and light-headedness. When the palpitations come on, some patients may have associated chest pain that on occasion can point to underlying heart artery disease. If the palpitations are more serious, people may pass out as a result.

Consequences of a Fast Heart Rate

Often a fast heart rate will have no significant effect on the heart, although there may be associated symptoms. In some cases however the symptoms may be enough as to cause concern and quality of life limiting symptoms. In a few cases, the heart rate may be continually elevated over a long period of time weeks-months often at heart rates above 120-130 beats per minutes and lead to a weakening of the heart muscle known as tachycardia mediated cardiomyopathy. Regardless, it is important to work up and identify any underlying causes of fast heat rate and give the appropriate treatment.

Fast Heart Rate – What Tests Are Needed?

History – The initial most important thing is a good history. Are there associated symptoms of palpitations, light-headedness, fatigue, and dizziness or passing out? Is there associated chest pain or shortness of breath? Is the fast heart rate intermittent or constant and do the symptoms only appear when the heart rate is elevated? What happens to the blood pressure when the heart rate is elevated? Is there a history of heart disease or prior testing? These questions are critical in determining the seriousness of the situation and determining the work up required. If there are alarm symptoms such as above then the heart rate needs work up and should not be ignored.

Physical Exam – Is the heart rate regular or irregular when it is fast. Are there physical exam signs of heart failure such as fluid retention? Also a thorough physical exam can point toward other systemic problems such a thyroid issues or other.

EKG – A baseline EKG is key. Is the heart rhythm normal or abnormal? Is there any evidence of abnormality of the heart rate or conduction system of the heart? It is particularly useful to perform an EKG during the period of fast heart rate as it may help clinch the diagnosis if there is a cardiac cause.

Blood work – Basic blood tests will be performed to rule out anemia or electrolyte abnormalities, thyroid function testing may be performed. Other testing may be performed as indicated.

Monitor – Often palpitations or fast heart rate occur intermittently and never when at the doctors office! A monitor can be worn to help catch an intermittent fast heart rate and then characterize it providing useful information. Monitors can be 1 day, several days, several weeks, or even much longer term if implanted. I personally find the utility of a monitor goes up significantly if a symptom diary is kept to record times when symptoms occur. The diary can then be crosschecked with the monitor to see any correlations.

Echocardiogram – This is an ultrasound scan of the heart that looks at the structure and function of the heart done commonly in patients with palpitations or fast heart rate.

EP study – If the heart rate elevation is felt to be from a cardiac cause, or related to abnormality of the structural system of the heart then sometimes to clarify a diagnosis electrophysiology specialists may perform an invasive test to clarify the diagnosis.

Treatment of Fast Heart Rate

Treat the Underlying Cause: Most important is to ensure there is no underlying systemic problem that is causing the fast heart rate. If there is anemia, for example, that will need to be treated. Infection and dehydration would need to be treated. Hormonal imbalances would require treating. Medications will be reviewed and any potential offending agents will need to be stopped if possible.

Medications: It is important not just to treat a number the reason underlying must be sought out. If the fast heart rate is thought to be from a cardiac cause then the appropriate treatment should be given. If there is significant muscle dysfunction then treatment aimed at strengthening the heart is given. If there are problems with the electrical system of the heart then medicines to slow the rate may be given such a beta blockers or calcium channel blockers. In some cases stronger medicines that prevent the occurrence of the arrhythmia in the first place may be prescribed, known as anti-arrhythmic medications. Specialists known as electrophysiologists typically prescribe anti-arrhythmic medications.

Procedures: If the fast heart rate is felt to be a primary cardiac arrhythmia then procedures may be required, particularly if medications do not work. In the case of SVT, procedures known as ablation can be particularly effective. In patients with Atrial fibrillation an ablation procedure may be useful if medicines aren’t effective and symptoms are present. VT may also be treated in this manner. Ablation procedures are performed by electrophysiologists, who are cardiologists specializing in the electrical system of the heart.

Fast Heart Rate – Overview and Conclusion

A fast heart rate although often defined as a heart rate over 90 is not necessarily abnormal and each case is different. History, physical exam and diagnostic testing are required in order to determine the significance of the heart rate and to see if any treatment is required. Treatment for non-cardiac causes of fast heart rate is to address the underlying cause. In the case of cardiac causes of fast heart rate, typically medication will be tried first or in some cases a procedure required particularly if the problem is with the electrical system of the heart.


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