Acid Base Imbalance Made Easy 🔥 ABG Tricks for Nursing aspirants

Hinzugefügt: 2026-05-31

[00:00:00]Hello and Welcome back dear Fakans to the learning platform of Alka Nursing Classes. So in today's session we are going to discuss acid base imbalance which is a very important topic from the examination point of view. Questions are mostly asked from wherever in every exam.

[00:00:14]So look, when [nasal sound] we talk about acid-base imbalance, the first thing we talk about is regarding the regulation. So this acid base imbalance that occurs in the body, if we talk about blood, then the pH of the blood is 7.35 to 7.45, it is constant most of the times until and unless there is any disease condition, it remains in a constant range. Now why does this happen? That is because of the buffer system. So, what is a buffer called? If you have seen in chemistry, any substance called buffer means what does it do? When the acid level of the body or any thing increases, it absorbs H positive ions.

[00:00:57]So that this acidity, this acidic nature will be reduced. Correct? So when it comes to buffers, what exactly are buffers? These are weak acids.

[00:01:09]Weak acids and their salts yes plus their salts. And it will either be a weak acid or a weak base and its salt. So that is the buffer. Correct? Now the blood mainly acts as an edge buffer in the body. So the blood acts as a buffer.

[00:01:30]Acts Edge Buffer. Correct? Now there are different types of buffer solutions in the blood which act at different points of time.

[00:01:40]Which is the most common buffer solution and which we can use?

[00:01:45]One in the human body and one in the blood of an individual. That is the bicarbonate buffer. So if the examiner asks you what is the main buffer system in an individual's body and that is blood, then your answer will be that it is a bicarbonate buffer. So when acidosis occurs.

[00:02:06]When do we speak of acidosis? Acidosis is said to occur when the blood pH of an individual becomes less than 7.35. When the concentration of H positive ions increases in the body and blood.

[00:02:22]Ok? So you must have read that pH is the negative log of H positive ion concentration. That means that the more H positive ions increase in an individual's body, the more what will happen? The pH of an individual's body will decrease. Correct?

[00:02:40]Now whenever this happens in normal conditions, what is the concentration of H positive ions? If it becomes too much then what happens at that time? This H positive binds with HCO3 negative. That is the bicarbonate ion. And what does it make? It makes us H2CO3 that is the we call it carbonic acid. What do you say?

[00:03:01]carbonic acid. Ok? And this carbonic acid is a weak acid.

[00:03:07]So what happens in this? It gets supple and breaks down.

[00:03:12]In which? Water plus CO2. So this CO2 [nasal sound] then comes out of the body through the respiratory tract. In The Same Way What If? Alkalosis will occur. That means that HCO3 is negative, that is the bicarbonate ion. If this is too much then what happens there? This HCO3 gets bound with whom? With H positive ions. And what does it build from there? Regenerates H2CO3. Correct? So these are two conditions where what happens?

[00:03:45]If acidosis occurs in the body, what happens at that time? If alkalosis occurs, what happens at that time? That is in normal condition. What is the condition now? If there is any pathological condition, the pH there may be less than 7.35 or more than 7.45. So if it falls below 7.35 then we call it as acidosis. And if it exceeds 7.45 then we call it as alkalosis. Now whenever we talk about whom? Of acidosis and alkalosis. So two things come into this. One that is the respiratory respiratory acidosis. And the second one that comes up is the metabolic metabolic acidosis. Ok? In the same way, one of the alkalosis is respiratory. Second comes metabolic. Now see, whenever you have to rule out whether it is acidosis or alkalosis. So the first initial parameter you will see is the pH. What is Holy and Soli, you can know on the basis of pH? Is it acidosis or alkalosis? If it is less than 7.35 then it is acidosis. What if it is more than 7.45? So is alkalosis. Correct?

[00:04:59]Then on the basis of the remaining parameters, we say is this respiratory? Or is it metabolic? If it is respiratory or metabolic? Is it compensated or is it uncompensated? If it is compensated, is it partially compensated or fully compensated? So what's the first thing we remembered? On the basis of pH, we say whether it is acidosis or alkalosis.

[00:05:21]Now the second parameter is the normal concentration of CO2 and the normal partial pressure from the can is 35 to 45 mma. Now if we look at CO2, the first thing you have to remember here is that CO2 is acidic in nature. It is acidic in nature and is related to the respiratory system. Ok? And the bicarbonate, that is the SO3 negative. What is this? This is a metabolic component. And plus it is related with the body. Other than the other than the respiratory system. Ok? It has a metabolic component and is alkalotic in nature.

[00:06:11]Correct? So now see if an individual has acidosis. Meaning what is the pH of 7.35? It is less. Is it respiratory or metabolic? On what basis will we say this? On the basis of CO2 On the basis of the bicarbonate ion. Now if there is acidosis and CO2 has increased. If CO2 increases then more H2CO3 will be formed.

[00:06:35]That means that more carbonic acid will be formed. So if the pH is high, the CO2 level is also high. So is respiratory acidosis. In the same way, if the pH is more than 7.45 and the CO2 levels are low, then what is this? This is respiratory alkalosis.

[00:06:56]So we find out respiratory acidosis and respiratory alkalosis on two bases.

[00:07:02]One on the basis of the PA. Second, that is based on CO2 levels. What if the PA is less than 7.35 and what's there from the other side?

[00:07:13]If carbon dioxide (CO2) is elevated, there is acidosis. Correct? If the CO2 on one side is more than 7.45 and the CO2 on the other side is less, then it is respiratory alkalosis. In the same way, if we talk about the metabolic side, then the bicarbonate ion in the metabolic side is alcoholic in nature and that is basic in nature. So it is simple that if there is acidosis then the bicarbonate ions will be less. Ok? And if there is alkalosis then there will be more bicarbonate ions. So the same scene will play here also. On the basis of PA we will say whether it is acidosis or alkalosis. Then we will look at the bicarbonate ions. If the bicarbonate ions are low then there is metabolic acidosis. And if the bicarbonate ion is high then there is metabolic alkalosis. Correct? So what we have remembered so far is that acidosis and alkalosis are based on pH. If CO2 has increased then it is respiratory acidosis, if CO2 has decreased then it is respiratory alkalosis, if bicarbonate has decreased then it is metabolic acidosis, it has increased, so it is metabolic alkalosis, this is basic, almost everyone would know what happens in these conditions, now we will talk regarding the compensation, okay that is the very thing and in most of the national exams, there is talk regarding compensation. Look, we have remembered three things till now. One CO2, second bicarbonate, third PA. We have already said about PA that we only roll out this much from the PA. Acidosis is alkalosis for the time being. Correct?

[00:08:57]We have two things left to give. One that is the CO2. The second one is that it is the SCO3 negative. Look, now if there is an individual who has acidosis or alkalosis, let us assume in one portion that there is an individual who has respiratory acidosis, then when I say there is respiratory acidosis, what will you say, first of all the pH is less than 7.35, secondly the CO2 has increased.

[00:09:27]Correct? Now if this individual needs compensation, then who will do it? The second part will be the opposite part, that means the metabolic component will compensate. If acidosis is occurring here, the metabolic part will cause alkalosis. If he did not undergo alkalosis, that means his range remained within normal limits. Meaning that this portion is not compensating.

[00:09:55]So that means that this scene that is happening here is uncompensated respiratory acidosis. So when do we say respiratory acidosis? It is uncompensated. When the bicarbonate ions are SCO3 negative, they will be in the range. How much will it be? 22 to 26 ml equivalent. Correct? Now when will you say it?

[00:10:17]That there is compensation in this. So this metabolic component has to be alkalized.

[00:10:23]How will alkalosis cause this? He has to increase his levels. So [nasal sound] if the alkalotic component and the metabolic component have increased their levels then obviously if the base has increased then what will be the acidic concentration? It will reduce. So in that case we will say that the respiratory acidosis is compensated.

[00:10:50]So in a nutshell what we will remember is that whenever we have any case if in the respiratory component we have either acidosis or alkalosis. The metabolic component has to be opposite to that.

[00:11:03]For example, there was acidosis here, so the bicarbonate levels had to be increased. What will happen to the metabolic component when it increases its levels?

[00:11:12]Alkalosis will occur. That is the compensation.

[00:11:15]In the same way, if there is respiratory alkalosis here. If there is respiratory alkalosis here, do we know? There are two things. One is pH greater than 7.45. The second thing is that CO2 is less.

[00:11:29]So what does the metabolic component have to do?

[00:11:31]This has to be acidosis. How will acidosis be treated? The levels of its basic components have to be reduced. So what will happen in this? HCO3 will be reduced.

[00:11:44]If there is respiratory alkalosis here and HCO3 is decreasing there, then that means compensation is taking place. The same logic applies to metabolic acidosis and metabolic alcoholism.

[00:11:58]What will happen there? The CO2 present there will compensate. If there is respiratory metabolic acidosis, then CO2, the respiratory component, will cause alkalosis, meaning CO2 will decrease. If there is metabolic alkalosis from here, what will the CO2 portion do? The respiratory portion will increase the CO2 levels. So that's respiratory acidosis. That is compensation. Now there are two things here, one is that is partially compensated and the second one is that is fully compensated.

[00:12:35]Fully compensated. See. If partially compensated, when will we speak? If there is compensation, the second portion has given compensation.

[00:12:46]He has given compensation. But the pH is out of range. Out of range means that either the PA is less than 7.35 or more than 7.45. If the PA is out of range then it will be out of range from 7.35 and 7.45. But from here the second opposite component would have given compensation. We call it as a partially compensated. Partially compensated respiratory and metabolic acidosis and alkalosis. When will we say fully compensated? When the pH is in range.

[00:13:26]pH inrange means now we will discuss it a little bit from above. Then we will understand this through examples. Ok?

[00:13:33]So PA in range means that the PA that is coming is between 7.35 to 7.45. Look, this is 7.35 to 7.45, here you have to remember one thing that from 7.35 to 7.40, what will come from 35 to 40? 7.363738 399 End40 This is the acidic component. There's the acidic part and there's the acidic component and from 7.41 to 7.45, there's this alkalotic component. Has an alkalotic component. Correct? So if here compensation is taking place in the opposite part and along with that the PA is in range.

[00:14:19]We call it as fully compensated respiratory and metabolic acidosis and alkalosis. Depends upon what the parameters will be? Let us try to understand with an example.

[00:14:29]For example, if I write here that the pH is 7.15 and the PCO2 is 50 mg and the HCO3 is 24 ml. Correct? See, the first thing we said was that on the basis of PA we will say whether it is acidosis or alkalosis, if PA is less than 7.35 then that means it is acidosis. Now, is this acidosis respiratory or metabolic, if it is respiratory then the PCO2 will be seen elevated, so when we look at PCO2, that is 50 mmol/g, then 35 to 45 is normal, now if it is 50 then that means it is elevated, so this is respiratory acidosis. Respiratory acidosis is it compensated? If it is compensated, which is the opposite component. That means what would have happened to the bicarbonate? Bicarbonate will be elevated.

[00:15:35]Because this bicarbonate is the basic component. Basic components we should get elevated. But when we look at bicarbonate, what is it? 24 Normal range is 22 to 26. Guys, this is inrange. If it is in-range, that means it has not moved, so it is uncompensated.

[00:15:54]What is? There is uncompensated acidosis. Which acidosis?

[00:16:00]Respiratory acidosis. So it is uncompensated respiratory acidosis. Now let's talk about the second [nasal sound] scene. For example, what is PA, that is 7.5, what is PCO2, PCO2 is 40, okay? And bicarbonate, which is bicarbonate here is 45. So see if PA is 7.5 that means it is more than 7.45 then what is it? There is alkalosis. There is alkalosis. If there is respiratory alkalosis, the PCO2 should be low. Is the PCO2 low?

[00:16:38]No. How much is it? 40 is in range. So leave it. What will we see now?

[00:16:43]Bicarbonate. If there is metabolic alkalosis then we should find elevated bicarbonate.

[00:16:50]Is bicarbonate elevated? Yes, if bicarbonate is elevated then it is metabolic alkalosis.

[00:16:56]Metabolic alkalosis. Is this compensated? Is it uncompensated? If it is compensated then the CO2 component of PCO2 will have to increase its levels. That means it has to cause acidosis in the respiratory component. But its range, its value is 40, that means it is within the range. If this is within range then what has happened here also? There has been no compensation here.

[00:17:23]So it is also uncompensated.

[00:17:26]This is uncompensated metabolic alkalosis. For example, what has happened here is that the PCO2 here is assumed to be 60 mmHg.

[00:17:44]Ok? So it is the same scene. There is alkalosis. Which one is alkalosis? There is metabolic alkosis.

[00:17:50]But the PCO2 is elevated. That means the respiratory component has increased its levels. It has started compensation. So what will happen here now? This will lead to compensated metabolic alkalosis. Now this compensated metabolic acid alkalosis, is it partial? Is it partial and is it full?

[00:18:15]Ok? If this is partial as we say that the PA will be out of range, then the PA is 7.5, so what is the normal range? 7.35 to 7.45 so the PA is out of range. That [nasal sound] means it is partially compensated. It is partially compensated. Now let's talk about fully compensated.

[00:18:38]Suppose the PA is 7.36, right? The PCO2 is that is 20, exactly 20 mmol and the bicarbonate ions are 16 millionths, see what has happened here, the PA is 7.36, now what did we say here that if the PA is between 7.35 to 7.45, from 7.35 to 7.4, what do we have to take? S is to take acidosis and from 7.41 to 7.45 we have to take alkalosis. So if PA here is 7.3, what does that mean here? There is acidosis. Correct? Acidosis We removed the PA. Just finished PA. After that, if it is respiratory then PCO2 should increase. Because CO2 is acidic in nature. But here when we look at CO2, it has reduced so there is no respiratory acetosis. If this isn't respiratory, then what is? That is metabolic. So is it metabolic?

[00:19:53]So what happens in metabolic acidosis?

[00:19:55]We should see a low level of bicarbonate ion.

[00:19:57]Ok? Why?

[00:19:59]Because bicarbonate is basic in nature. Is there a shortage of bicarbonate ions here? Yes, there is less bicarbonate ion here.

[00:20:06]So, it is acidosis. But which metabolic acidosis is now compensated or not? Now what if what is happening in the metabolic component?

[00:20:18]What does the respiratory component have to do if acidosis is occurring?

[00:20:19]Alkalosis has to be done. So how will this cause alkalosis? By reducing CO2. If CO2 decreases, its partial pressure will decrease. Is the partial pressure of PCO2 low here? Yes, the partial pressure here is less. If it is less then that means that the compensation here is present. If compensation is present, is it fully compensated or partially compensated?

[00:20:42]So if we look at PA, that is in range. If the PA is in-ranged then it is fully. What is [nasal sound]? Fully. So what will be our final answer? That this is fully compensated metabolic acidosis. So what is the conclusion of our discussion that what will we extract from pH PA? There is acidosis that is alkalosis.

[00:21:10]Correct? If the pH is less than 7.35 then it is acidosis. If it is more than 7.45 then it is alkalosis. Now is it respiratory? It is metabolic. What do we see in respiratory? Let's look at CO2. If CO2 is increased that means carbonic acid will increase more and respiratory acidosis will occur. If CO2 has decreased, that means carbonic acid is increasing less, then there will be respiratory alkalosis.

[00:21:43]What do we see in In the Same Way Metabolic? to bicarbonate. What is bicarbonate? That is basic in nature. If the base is reduced by bicarbonate and we can, the base will be reduced and the acid will increase. Ok? If bicarbonate is low, there is metabolic acidosis. If bicarbonate is increased then there is metabolic alkalosis. After that, we talk about whom? Of compensation.

[00:22:07]What do we look for in compensation? If there is acidosis in the respiratory, then the metabolic one has to do alkalosis.

[00:22:14]How will the metabolic one cause alkalosis? Will increase bicarbonate.

[00:22:17]If there is alkalosis in respiratory meaning CO2 is low then what should the bicarbonate person do? Acetolysis has to be done. How will he get it done? By reducing bicarbonate. In the same way, if there is such a scene in metabolic, then the respiratory one will do its opposite.

[00:22:34]After that when we talked about compensation, we talked about compensation. After that we said that either it will be fully or partially.

[00:22:42]So when did we partially say that the PA is out of range? Ok? If the PA is either less than 7.35 or more than 7.45. That means out of range, so at that time we say it is partially compensated. If the pH is in this range.

[00:23:00]That means with in 7.35 to 7.45 range at that time we say it is fully compensated. Correct? So this is the scene of these four.

[00:23:10]Apart from this, sometimes the examiner asks you a question like what is the pH of a patient that is 7.2?

[00:23:22]The pH is 7.2. Which is PCO2, PCO2 is 50 mmol and which is bicarbonate, which is HCO3, that is 12 milliliters. Look, now this is 7.2, what does that mean here? There is acidosis here. Correct? Now if this is respiratory acidosis then the PCO2 should be elevated. What is elevated PCO2? Yes, it is elevated. So what is this?

[00:23:52]Respiratory acidosis. What is?

[00:23:55]Respiratory acidosis. Now, if there is respiratory acidosis, then the bicarbonate should either be in the normal range or it should be elevated. If elevated is found then compensation is being given. If found in the normal range then it is uncompensated.

[00:24:10]But what is happening here? The bicarbonate present here has also reduced. So bicarbonate is lower than here. If the PA is less than this, it is metabolic acidosis. PA is lower than here. If the PCO2 is high, it is respiratory acidosis. Now here there is metabolic acidosis as well as respiratory acidosis. So it is metabolic acidosis as well. So whenever an individual has respiratory acidosis, they will also have metabolic alkalosis. So we call it as the mixed acidosis.

[00:24:46]Ok? and mixed respiratory metabolic acidosis. What could possibly happen along with this? Mixed alkalosis may also occur. Here if we give the final answer, so it is mixed respiratory acidosis.

[00:25:04]Ok? and mixed metabolic acidosis.

[00:25:09]Ok? So when the mix comes, that means both the metabolic and respiratory components are involved and what is happening in both?

[00:25:19]Either acidosis is occurring or alkalosis is occurring. So here if some causes are given here. If an individual has respiratory acidosis, then we said that in respiratory acidosis the pH will decrease. Respiratory or metabolic pH will decrease. PCO2 increases and bicarbonate may either be normal or elevated.

[00:25:42]So what are the reasons for this? If there is hypoventilation in an individual and his breathing is slow, then due to that CO2 will build up, hence there will be respiratory acidosis or there will be obstruction in COPD also. The CO2 gets accumulated. Ok? Either it could be pneumonia or drug overdose. What happens in a drug overdose? The respiratory center will become depressed.

[00:26:06]So with that there will be accumulation of CO2 in the body.

[00:26:11]When does alkalosis occur? Alkalosis in the case of hyperventilation. If an individual is hyperventilating because of anxiety. Ok? And because of some other reason.

[00:26:21]So what will happen in that? The CO2 that is there will be more and more blow out. When more CO2 comes out of the body, the PCO2 here will decrease. The PA will increase. And we can cause alkalosis and we will see bicarbonate either being normal or reduced. Along with this there will be anxiety fever or hypoxia. So, in case of hypoxia, the individual will suffer from tachypnea in the beginning.

[00:26:48]So what will happen with that? He will develop alkalosis, respiratory alkalosis. But later on in the advanced stage, an individual gets Bradnia.

[00:26:58]And along with this, you will remember what happens in head trauma? Respiratory alkalosis occurs.

[00:27:05]Why does it happen? Because whenever an individual suffers head trauma, ICP increases at the time of head trauma.

[00:27:11]Correct? Now to reduce ICP, the body's respiratory system increases its rate and we can cause the individual to hyperventilate. When an individual hyperventilates, more and more CO2 will be released. The more CO2 is released, the more cerebral vasoconstriction will occur.

[00:27:30]Why would cerebral vasoconstriction occur?

[00:27:32]Because the CO2 causes vasodilation.

[00:27:35]So when CO2 causes vasodilation, the cerebral blood flow will increase.

[00:27:40]Ok? And we can see that the cerebral vessels will dilate.

[00:27:45]So when they become deflated, their seeping ability increases. That means that fluid can flow out of the vascular tree.

[00:27:53]So the more fluid is released, the more cerebral edema will increase.

[00:27:58]So to prevent this the body compensates. So that more CO2 comes out. More CO2 comes out.

[00:28:05]Vasoconstriction occurs and edema is reduced. So in the same way, when will metabolic acidosis occur? When PA decreases. PCO2 will be normal or the bicarbonates will either be reduced or normal. Correct? So if an individual has DKA or renal failure. Ok?

[00:28:25]Or if an individual is suffering from excessive diarrhea or if an individual is suffering from excessive starvation, then what can happen due to that? Metabolic acidosis occurs. So what causes metabolic alkalosis? If vomiting occurs, HCL will come out. Ok? There will be diuresis. So diuretics increase the excretion of H positive ions.

[00:28:46]So when more and more H positive ions are released from the body, then metabolic alkalosis or excess anti acid will occur. When you take excess anti- acids, they neutralize the gaseous pH. Ok? Reduces acidity. So what happens there? Metabolic alkalosis occurs. So this was a summarized lecture on the acid-base imbalance. Hope you have enjoyed it.