nugget of wisdom - hyperventilation

What is Hyperventilation?

Hyperventilation or overbreathing is the state of breathing faster than normal at rest (normal minute ventilation is generally 5-8 liters of air per minute at rest for a 70-kg man).

What causes the effect of Hyperventilation?
Counterintuitively, such effects are not precipitated by the sufferer's lack of oxygen or air. Rather, the hyperventilation itself reduces the carbon dioxide concentration of the blood to below its normal level because one is expiring more carbon dioxide than being produced in the body, thereby raising the blood's pH value (making it more alkaline). This causes constriction of the blood vessels which supply the brain, and preventing the transport of oxygen and other molecules necessary for the function of the nervous system.

Chilli sauce for your nugget
The high pH value resulting from hyperventilation also reduces the level of available calcium, which affects the nerves and muscles, causing constriction of blood vessels and tingling.

Hyperventilation can be useful in the management of cerebral compression. Hyperventilation, and the resultant cerebral vasoconstriction, is useful in this situation, since it decreases the volume of blood in the brain. Less blood volume in the cranial cavity results in less pressure compressing the brain. However, this comes at the cost of reducing blood flow to the brain, which can potentially result in brain damage.

(credits: Wikipedia and Dr Hull)

nugget of wisdom - asthma

one of the most common problems in Singapore..let's take a more in-depth look at it!


What is Asthma?

Asthma is a disorder of the respiratory system, which causes inflammation of the airways. This leads to constriction and swelling of airways, causing difficulty in breathing.


What is the mechanism behind an asthma attack?

An asthma attack has 2 main components - airway irritation and swelling (inflammation) and tightening of the muscles surrounding the airways (bronchoconstriction).

• In asthma, inhalation of certain substances (eg, pollen, smoke particles, cold air) causes the smooth muscle (outermost muscle) of the airway to spasm (contract), thus narrowing the airway. 
• The middle layer swells because of inflammation
• More mucus is produced which clogs the airways
• All of these effects reduce the diameter of the airways.

Analogy time!

To visualize the mechanism of airway obstruction, imagine looking through a tube where you can see out to the other side.

When an asthma attack occurs, one of the first reactions that the airway contracts. Imagine the garden hose contracting, and imagine the visible world on the other end of the hose narrowing. Think of that reduced visual field as representing less oxygen getting into the lungs.

The second reactions is swelling (from the inside). The interior muscles of the airway swells. Imagine the hose as thicker on the inside. So now, we have a narrower hose from constriction, and obstruction occuring within the hose from swelling, both narrowing the the visual field in the hose as we look out to the other end. The same thing occurs in the airway during an asthma attack - air flow is reduced further, from the action of two obstructive mechanisms.

(Medical knowledge here! Read on if you want more info) This swelling occurs because, in reaction to some stimulus that may be localized in the upper airway, the offended area is now being bombarded by white cells called mast cells (eosinophils and basophils)These cells release Histamine..Histamine causes the affected tissue to swell. Histamine when released is the primary cause of all "swelling."

Lastly, there is mucus production. which narrows our visual field through the garden hose almost completely. Imagine the hose being filled with..well, mucus. When we can't see through the hose to the other side, that symbolizes the reduction of air flow in the patient with asthma and the decreasing amounts of oxygen that are getting to the lungs.

How do Relievers Inhalers work?


The drug in a reliever inhaler relaxes the muscle in the airways. This opens the airways wider, and symptoms usually quickly ease. These drugs are called bronchodilators as they dilate (widen) the bronchi (airways). 

(yes, there are that many different inhalers!)

So...what's the difference between Reliever Inhalers, and Preventive Inhalers?


Reliever inhalers are used when an asthma attack happens, and you need a fast acting medicine. Unless medicine in tablet form, the drug in the reliever inhaler goes straight to the airway, thus making the effect much faster and stronger. 


For Preventive Inhalers, these are taken every day to prevent symptoms from developing. The type of drug commonly used in preventer inhalers is a steroid. Steroids work by reducing the inflammation in the airways. When the inflammation has gone, the airways are much less likely to become narrow and cause symptoms such as wheezing.

(anyone got the joke? :D)

tadaaaa! hope you didn't die from information overload! :D feel free to click on the below links (credits) for even more information :D

(credits - Asthma Action America, Merck Manual, Buzzle, Hub Pages, Patient.co.uk)

nugget of wisdom - AED..again!

a flowchart makes everything easier!

nugget of wisdom - AED

yeap, we have all heard it, seen it, and probably tried it (or will try it), but how exactly does an AED work?


First of all...what is an AED?

AED stands for Automated External Defibrillator. An AED is a device used to administer an electric shock through the chest wall to the heart. Built-in computers assess the patient’s heart rhythm, judge whether defibrillation is needed and then administer the shock. Audible and/or visual prompts guide the user through the process.




Will an AED always resuscitate someone in cardiac arrest?

An AED only works in 2 situations - when the casualty is going through Ventricular Fibrillation (VF), or Ventricular Tarchycardia (VT). Most patients, when they become pulseless go through a brief period of VF. An AED only treats a fibrillating heart (heart that still has rhythm). VF eventually deteriorates into a total absence of electrical activity, often around ten to fifteen minutes after arrest. In cardiac arrest without any heart rhythm at all, the heart does not respond to an AED, and requires CPR instead.

Err...how does a heart looks like ah?

Blood comes in from the atria (plurar of atrium!), and goes out from the ventricles! 

The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. 

What is Ventricular Tarchycardia (VT)?

VT is a rapid heart rhythm originating within the ventricles. VT tends to disrupt the orderly contraction of the ventricular muscle, so that the ventricle's ability to eject blood is often significantly reduced. That, combined with the excessive heart rate, can reduce the amount of blood actually being pumped by the heart during VT to dangerous levels. Consequently, patients with VT often experience -- in addition to palpitations -- extreme lightheadedness, loss of consciousness, or even sudden death.

the above diagram shows the difference between a normal heart rate (top), and VT (bottom)

Or to understand that simply...the heart rhythm is messed up. 

What is Ventricular Fibrillation (VF)?

VF is closely related to VT. However, VF is a much more disorganized rhythm that immediately brings to a halt all meaningful ventricular contractions. Blood immediately stops flowing, and loss of consciousness occurs within seconds. Unless cardiopulmonary resuscitation is started within a few minutes of the onset of VF, sudden death will occur.

the heart rhythm is fast (300 to 600!), and extremely irregular..that's VF for you!

Or to understand that simply...the heart rhythm is really, really, really messed up.

Why does someone having a heart attack need an AED?

When a heart attack becomes a full cardiac arrest, the heart most often goes into uncoordinated electric activity called ventricular fibrillation. The heart twitches ineffectively and can’t pump blood. 

The AED delivers electric current to the heart muscle, momentarily stunning the heart and stopping all activity. This gives the heart an opportunity to resume beating effectively. While the heart pauses, the small piece of tissue responsible for the next impulse (the sinus node or sinoatrial node) should fire off the next heart beat.

Video

If you're confused by all that rubbish above, this video should clear it up a little! :)

:D please do not try this

nugget of wisdom - CPR

confused by the CPR procedure?? here's a simple flowchart to (hopefully) make your life simpler! :D

note: all comp trainees are to have a copy of this during the training this coming Sat

nugget of wisdom - shock

so...what exactly is shock?

yes yes, I know the S&S are weak rapid pulse, fast shallow breathing, cold clammy skin, yada yada....

but, what is shock??


 shock, essentially is a life-threatening condition in which blood pressure is too low to sustain life.


Shock has several causes: a low blood volume, which causes hypovolemic shock; inadequate pumping action of the heart, which causes cardiogenic shock; or excessive widening of blood vessels, which causes distributive shock (anaphylactic shock, neurogenic shock and septic shock).


Hypovolemic Shock

Low blood volume results in less-than-normal amounts of blood entering the heart with every heartbeat and therefore less-than-normal amounts of blood being pumped out to the body and its cells.

Cardiogenic Shock

Inadequate pumping action of the heart can also result in less-than-normal amounts of blood being pumped out with every heartbeat.

Distributive Shock

Excessive dilation of blood vessels (vasodilation) increases the capacity of blood vessels, so that blood meets with less resistance as it flows through them. Blood pressure in the dilated vessels is lower, so the cells fed by those vessels get less blood.

Blood vessels may be excessively dilated because of a serious allergic reaction (anaphylaxis (see Allergic Reactions: Anaphylactic Reactions)), a severe bacterial infection (shock caused by such an infection is called septic shock (see Bacteremia, Sepsis, and Septic Shock: Introduction)), overdose of drugs or poisons that dilate blood vessels, and injuries to the spinal cord and rarely the brain.

read http://www.merckmanuals.com/home/sec03/ch024/ch024a.html for more info!

nugget of wisdom - cerebral compression

here's a simple, yet detailed explanation of how cerebral compression arises!




"Your brain takes up about eight/tenths of the space inside your skull. Most of the rest of the space is filled with blood vessels and cerebrospinal fluid (CSF), a dense, clear, colorless substance. CSF flows around the outside of the brain, through a latticework of fibers. Working together, fluid and fibers form the brain's primary shock absorption system, protecting the brain from the bumps and jiggles of everyday life. But, if your head smacks into something with sufficient force, your brain can slosh around enough to tear some of the blood vessels, and even bruise the brain itself, if it hits the inside of the skull. That's how you can have brain damage without headbone damage.

What happens inside the head is this. Blood flows out of the broken blood vessels in the head and, sometimes, blood serum starts to leak out of the vessels in the damaged area of the brain. Swelling results, but, unlike the rest of the body, there's no place for the swelling to go. As the space inside the head decreases, there is less and less room for the flow of life-sustaining blood. Initially, the brain stops making CSF, and starts to reabsorb what is already there . . . the brain tries to create more space. The brain can even limit the amount of blood flowing to itself. But, if the damage is sufficient, the brain's compensatory mechanisms cannot keep up with the swelling. Intracranial pressure (ICP) starts to rise, and, as a result, the brain is squashed."

tadaaaa!