Body Buffer Body Buffer systemsystem

--Hydrogen ion HomeostasisHydrogen ion Homeostasis

--Control systemControl system

- - Control CO2 (PCO2)Control CO2 (PCO2)

By lungsBy lungs

- - Control HCO3Control HCO3-- By By

Kidney and Kidney and ErythrocytesErythrocytes

Body Buffer systemBody Buffer systemHydrogen Ion HomeostasisHydrogen Ion Homeostasis

--About 50 to100 m mol of hydrogen ions About 50 to100 m mol of hydrogen ions

are released from cells into extracellular are released from cells into extracellular fluid each dayfluid each day

**Hydrogen ion concentration [HHydrogen ion concentration [H++] is ] is maintained between about 35 and maintained between about 35 and 45 nano mol\L45 nano mol\L..

40nmol/L=pH 7.440nmol/L=pH 7.4)) ))

--Control of hydrogen ion Control of hydrogen ion balance depends on the balance depends on the secretion of Hsecretion of H++ from the body, from the body, mainly into the urinemainly into the urine thereforethereforeRenal impairment causes Renal impairment causes acidosisacidosis

--Aerobic metabolism of the carbon Aerobic metabolism of the carbon skeletons of organic compounds skeletons of organic compounds converts from hydrogen, carbon converts from hydrogen, carbon and oxygen to water and carbon and oxygen to water and carbon dioxide (COdioxide (CO22))

COCO22 is essential compound of is essential compound of extracellular buffering systemextracellular buffering system

--Control of COControl of CO22 depends on normal lung depends on normal lung functionfunction . .

Definition of Buffer ConstituentDefinition of Buffer Constituent

An Acid can dissociate to produce An Acid can dissociate to produce Hydrogen ion (protons HHydrogen ion (protons H++) which) which

accepted by base Exampleaccepted by base Example

H2COH2CO33 H H++ + HCO3 + HCO3--

Carbonic acid bicarbonate Carbonic acid bicarbonate ionion

BufferingBuffering Is a process by which a strong acid (or Is a process by which a strong acid (or

base) is replaced by a weaker one, base) is replaced by a weaker one, with a consequent reduction in the with a consequent reduction in the number of free hydrogen ions and number of free hydrogen ions and therefore the change in PHtherefore the change in PH

HCl + NaHCOHCl + NaHCO33 = H2CO = H2CO33 + NaCl + NaCl

Strong acid buffer weak acid Strong acid buffer weak acid neutral saltneutral salt

PH is a measure of PH is a measure of hydrogen ion activityhydrogen ion activity

Log 100 =log 10Log 100 =log 1022=2=2

Log 10Log 1077=7=7

If [HIf [H++] is 10] is 10-7-7 (0.000 0001) (0.000 0001)

Then log [HThen log [H++] =-7] =-7

The Henderson The Henderson ––hasselbalch equationhasselbalch equation

PH=PK+log [base] /[acid]PH=PK+log [base] /[acid]

The bicarbonate pair is an The bicarbonate pair is an important biological bufferimportant biological buffer exampleexample ; ;

HH22COCO33 HCO HCO33-- + H + H++

Acid baseAcid base

The base is bicarbonate (HCOThe base is bicarbonate (HCO33--) and the ) and the

carbonic acid (Hcarbonic acid (H22COCO33)). .

--It is not possible to measure the It is not possible to measure the latter directlylatter directly however it is in equilibrium with however it is in equilibrium with dissolved COdissolved CO22 of which the partial of which the partial pressure (PCOpressure (PCO22) can be estimated) can be estimated..

The conc. ofThe conc. of H H22COCO33 is derived by is derived by

multiplying this measured value by themultiplying this measured value by the

solubility constant(s) for COsolubility constant(s) for CO22 therefore therefore

PH =PK-log [HCOPH =PK-log [HCO33--]/PCO]/PCO22 XS XS

S=0.23 kilo passcalS=0.23 kilo passcal

PK of bicarbonate system is 6.1PK of bicarbonate system is 6.1

[ [ HCOHCO33--]]

---------------------- PH=6.1+logPH=6.1+log

PCOPCO22X0.23X0.23

Hydrogen ion Hydrogen ion HomeostasisHomeostasis

PH is relatively tightly controlled in PH is relatively tightly controlled in blood by the following mechanismsblood by the following mechanisms

11--Hydrogen ions can be Hydrogen ions can be incorporated in waterincorporated in water

HH++ + HCO + HCO33-- H H22COCO33 CO CO22 + H + H22OO

This is normal mechanism during oxidative This is normal mechanism during oxidative phos phorylation. Hphos phorylation. H++ is inactivated by is inactivated by combining with the HCO3 only if the combining with the HCO3 only if the reaction is driven to the right by the reaction is driven to the right by the removal of COremoval of CO22..

By this would cause bicarbonate depletionBy this would cause bicarbonate depletion

22--HH++ can be lost from the body only through can be lost from the body only through the kidney and the intestinethe kidney and the intestine This mechanism is coupled with the This mechanism is coupled with the generation of bicarbonate ion (HCOgeneration of bicarbonate ion (HCO33

--))In the kidney this is the method which In the kidney this is the method which secretion of excess Hsecretion of excess H++ ensures ensures regeneration of buffering capacityregeneration of buffering capacity

Control systemControl system

--COCO22 and H and H++ are potentially toxic products are potentially toxic products of aerobic and anaerobic metabolismof aerobic and anaerobic metabolism

--most COmost CO22 is lost through the lungs but is lost through the lungs but some is converted to bicarbonatesome is converted to bicarbonateThus contributing important extracellular Thus contributing important extracellular buffering capacitybuffering capacity

--Bicarbonate system is the most Bicarbonate system is the most important buffer in the body because important buffer in the body because has high capacityhas high capacity . .

The control of COThe control of CO22 (PCO (PCO22) ) by the Respiratory center by the Respiratory center and lungsand lungs

The partial pressure of COThe partial pressure of CO22 in plasma is in plasma is

normally about 5.3 kpa (40 mmHg) andnormally about 5.3 kpa (40 mmHg) and

depend on the balance between the rate depend on the balance between the rate ofof

production by metabolism and the loss production by metabolism and the loss through the pulmonarythrough the pulmonary. .

--the rate of respiration, and then the rate of respiration, and then therefore the rate of COtherefore the rate of CO22 elemination elemination is controlled by chemoreceptor in the is controlled by chemoreceptor in the respiratory centre in the medulla of respiratory centre in the medulla of the brainthe brain . .

The receptors respond to changes in the The receptors respond to changes in the [CO[CO22]or[H]or[H++] of plasma or of the ] of plasma or of the cerebrospinal fluidcerebrospinal fluid. . IfIf

11--the PCOthe PCO22 rises much above 5.3 kpa. Or rises much above 5.3 kpa. Or

22--the PH falls, the rate of respiration the PH falls, the rate of respiration increasesincreases. .

Normal lungs have a very large reserve Normal lungs have a very large reserve capacity for COcapacity for CO22 elimination elimination

The normal respiratory centre and lungs can The normal respiratory centre and lungs can control COcontrol CO22 conc. Within norrow limits by conc. Within norrow limits by responding to changes in the [Hresponding to changes in the [H++] and ] and therefore compensate for changes in acid-therefore compensate for changes in acid-base disturbancesbase disturbances. .

--some diseases of the lungs, or abnormalities some diseases of the lungs, or abnormalities of respiratory control, primarily affect the of respiratory control, primarily affect the PCOPCO22

The Control of Bicarbonate The Control of Bicarbonate byby-The Kidneys and -The Kidneys and ErythrocytesErythrocytes

The renal tubular cells and The renal tubular cells and erythrocyteserythrocytes

generate bicarbonate, the buffer base generate bicarbonate, the buffer base in thein the

bicarbonate system from CObicarbonate system from CO22 under under physiological conditionsphysiological conditions..

The erythrocyte mechanism makes The erythrocyte mechanism makes finefine adjustmentsadjustments to the plasma to the plasma bicarbonate conc. In response to bicarbonate conc. In response to changes in PCOchanges in PCO22 in in

lungs and tissueslungs and tissues..

The kidneys play the major role in The kidneys play the major role in maintaining the circulating maintaining the circulating bicarbonate conc. And in elimination bicarbonate conc. And in elimination HH++ from the body from the body..

The carbonate The carbonate dehydratase systemdehydratase system

11--bicarbonate is produced following the bicarbonate is produced following the dissociation of carbonic acid formed dissociation of carbonic acid formed from COfrom CO22and Hand H22OO..

This is catalyzed by carbonate This is catalyzed by carbonate dehydratase (CD) present in high dehydratase (CD) present in high conc. in erythrocytes and renal conc. in erythrocytes and renal tubular cellstubular cells..

COCO22 + H + H22O CD HO CD H22COCO33 H H++ + HCO + HCO33--

22--in addition to content erythrocytes andin addition to content erythrocytes and renal tubular cell to CD they also haverenal tubular cell to CD they also have means of removing one of the products, means of removing one of the products,

HH ,+ ,+thus both reactions continues to the right thus both reactions continues to the right and HCO3- is formedand HCO3- is formed..

33--one of the reactants, water, is freely one of the reactants, water, is freely available and one of the products, Havailable and one of the products, H++ is is removedremoved..

HCOHCO33-- generation is therefore accelerated if generation is therefore accelerated if

the conc.ofthe conc.of: :

11--COCO22 rises rises

22--HCOHCO33-- falls falls..

33--HH++ falls because it is either buffered falls because it is either buffered by erythrocytes or excreted from the by erythrocytes or excreted from the body by renal tubular cellsbody by renal tubular cells..

Therefore an increase of intracellular P COTherefore an increase of intracellular P CO22 or decrease in intracellular [HCOor decrease in intracellular [HCO33

--] in the ] in the erythrocytes and renal tubular cells erythrocytes and renal tubular cells maintain the extracellular bicarbonate maintain the extracellular bicarbonate conc. by accelerating the production of conc. by accelerating the production of HCOHCO33

--..

This minimizes changes in the ratio of This minimizes changes in the ratio of [HCO[HCO33

--] to PCO] to PCO2 2 and therefore change in PHand therefore change in PH..

In normal subject, at a In normal subject, at a plasmaplasma; ;

11--PCOPCO22 of 5.3KPa(a CO of 5.3KPa(a CO22 of about 1.2 of about 1.2 mmol\Lmmol\L

22--Erythrocytes and renal tubular Erythrocytes and renal tubular cells keep the extracellular cells keep the extracellular bicarbonate at about 25 mmol\Lbicarbonate at about 25 mmol\L

33--The extracellular ratio of [HCOThe extracellular ratio of [HCO33--] to ] to

[CO[CO22] (both in mmol\L) is just over ] (both in mmol\L) is just over 20:120:1..

PH can be calculated from the PH can be calculated from the Henderson equation that with PK of Henderson equation that with PK of 6.1,this6.1,this

represents a PH very near 7.4represents a PH very near 7.4 . .

An increase of intracellular PCOAn increase of intracellular PCO22,or a ,or a decrease in intracellular [HCOdecrease in intracellular [HCO33

--], ], accelerates HCOaccelerates HCO33

-- production and production and minimizes changes in the ratio and minimizes changes in the ratio and therefore in PHtherefore in PH . .

Bicarbonate Generation by Bicarbonate Generation by the Erythrocytesthe Erythrocytes

11--Erythrocytes produce little COErythrocytes produce little CO22 as they as they lack aerobic pathwaylack aerobic pathway

22--Plasma COPlasma CO22 diffuses along a concentration diffuses along a concentration gradient into erythrocytes, where gradient into erythrocytes, where carbonate dehydratase catalyses its carbonate dehydratase catalyses its reaction with water to from carbonic acid reaction with water to from carbonic acid (H(H22COCO33) which then dissociates) which then dissociates

33--Much of the HMuch of the H++ is buffered by hemoglobin is buffered by hemoglobin and the HCOand the HCO33

-- diffuses out into the diffuses out into the extracellular fluid along a conc. Gradientextracellular fluid along a conc. Gradient

The kidneysThe kidneysTwo renal mechanism control Two renal mechanism control [HCO[HCO33

--]in the extracellular fluid]in the extracellular fluid : :

11--bicarbonate reclamationbicarbonate reclamation ((reabsorption)reabsorption)

The COThe CO22 driving in renal tubular cells is driving in renal tubular cells is derived from filtered bicarbonate, derived from filtered bicarbonate, after action of the carbonate after action of the carbonate dehydratase. There is no correct to dehydratase. There is no correct to an acidosis but can maintain a an acidosis but can maintain a steady statesteady state..

Normal urine is nearly HCONormal urine is nearly HCO33-- free. free.

An An

amount equivalent to that filtered amount equivalent to that filtered by the by the

glomeruli is returned to the body glomeruli is returned to the body by the tubular cells.by the tubular cells.

The luminal surface of renal tubular The luminal surface of renal tubular cells arecells are

impermeable to HCOimpermeable to HCO33-- , Thus, HCO , Thus, HCO33

-- cancan

only be returned to the body if first only be returned to the body if first convertedconverted

to COto CO22 in the tubular Lumina, and an in the tubular Lumina, and an

equivalent amount of COequivalent amount of CO22 is converted is converted to HCOto HCO33

- - with in tubular cells with in tubular cells..

22--bicarbonate generationbicarbonate generation

A very important mechanism for A very important mechanism for correctingcorrecting

acidosis, in which the levels of COacidosis, in which the levels of CO22 or or

[[HCOHCO33-- ] ]affecting the carbonate dehydratase affecting the carbonate dehydratase

reaction in tubular cellsreaction in tubular cells

reflect those in the extracellular fluid, reflect those in the extracellular fluid, there is a net loss of Hthere is a net loss of H++ (fig) (fig)

Acid_Base disordersAcid_Base disorders

--Disturbances of HDisturbances of H++ homoeostasis homoeostasis always involve the bicarbonate always involve the bicarbonate buffer pairbuffer pair..

--In respiratory disturbances In respiratory disturbances abnormalities of CO2 are primaryabnormalities of CO2 are primary . .

--Whereas so-called metabolic or nonWhereas so-called metabolic or non

respiratory disturbances [HCOrespiratory disturbances [HCO33--] is ] is

affected early and changes in COaffected early and changes in CO22 are secondaryare secondary..

--Acid blood PH is known as acidaemia, Acid blood PH is known as acidaemia, and alkaline blood PH is called and alkaline blood PH is called alkalaemiaalkalaemia . .

--Abnormal processes, either Abnormal processes, either respiratory or metabolic, generate respiratory or metabolic, generate abnormal amounts of acid or abnormal amounts of acid or base,acidosis or alkalosis base,acidosis or alkalosis respectivelyrespectively . .

--The blood PH may or may not be The blood PH may or may not be abnormal because of the abnormal because of the compensatory mechanismscompensatory mechanisms

AcidosisAcidosisAcidosis occurs if there is a fall in Acidosis occurs if there is a fall in the ratio [HCOthe ratio [HCO33

--]:PCO]:PCO22in the in the extracellular fluidextracellular fluid..

It may be due toIt may be due to ; ;

11--metabolic(non-respiratory) metabolic(non-respiratory) acidosisacidosis..

In which the primary abnormality In which the primary abnormality in the bicarbonate buffer system in the bicarbonate buffer system is a reduction in [HCOis a reduction in [HCO33

--]]

22--respiratory acidosisrespiratory acidosis,,

In which the primary abnormality in In which the primary abnormality in the bicarbonate buffer system is rise the bicarbonate buffer system is rise in PCOin PCO22

The primary disorder in the The primary disorder in the bicarbonate buffer system in a bicarbonate buffer system in a metabolic acidosis is a reduction in metabolic acidosis is a reduction in [HCO[HCO33

--],resulting in a fall in blood PH],resulting in a fall in blood PH..

The reduction in the HCOThe reduction in the HCO33-- may be due may be due

toto;;

Metabolic acidosisMetabolic acidosis

11--its use in buffering Hits use in buffering H++ more rapidly more rapidly than it can be generated by normal than it can be generated by normal homeostatic mechanismhomeostatic mechanism

22--loss in the urine or gastrointestinal loss in the urine or gastrointestinal tract more rapidly than it can be tract more rapidly than it can be generated by normal homeostatic generated by normal homeostatic mechanismmechanism..

33--impaired productionimpaired production. .

Some causes of Some causes of metabolic acidosismetabolic acidosis..

11--acute or chronic renal failureacute or chronic renal failure

22--ketosis (diabetes mellitus or ketosis (diabetes mellitus or starvation)starvation)..

33--lactic acidosislactic acidosis..

Management of metabolic Management of metabolic acidosisacidosis

The biochemical findings in plasma in The biochemical findings in plasma in aa

metabolic acidosis aremetabolic acidosis are;;

11--plasma [HCOplasma [HCO33--] is always low] is always low,,

22--PCOPCO22 is usually low is usually low (compensatory change)(compensatory change),,

33--the PH is low (uncompensated or the PH is low (uncompensated or partly compensated) or near normal partly compensated) or near normal (fully compensated)(fully compensated)..

44--plasma [Clplasma [Cl--] is unaffected in most ] is unaffected in most cases unless there is cases unless there is hyperchloraemic acidosishyperchloraemic acidosis

Some Biochemical testSome Biochemical testthat may help to elucidate the cause of that may help to elucidate the cause of thethe metabolic acidosis aremetabolic acidosis are;;

11--plasma urea and creatinine plasma urea and creatinine estimationestimation..

22--determination of plasma anion gapdetermination of plasma anion gap,,

33--plasma glucose estimationplasma glucose estimation,,

44--blood lactate determinationblood lactate determination..

55--test for blood gasestest for blood gases..

66--test for ketones in urinetest for ketones in urine..

77--tests for, drugs or poison .i.e.(ethanol tests for, drugs or poison .i.e.(ethanol paracetamol, salicylate)paracetamol, salicylate)..

88--specialized tests for renal tubular specialized tests for renal tubular acidosisacidosis..

Respiratory acidosisRespiratory acidosis

The primary abnormality in the The primary abnormality in the bicarbonatebicarbonate

buffer system is CObuffer system is CO2 2 retention , retention , usually dueusually due

to impaired alveolar ventilation to impaired alveolar ventilation with a consequent rise in PCO2with a consequent rise in PCO2..

As in the metabolic disturbance, the As in the metabolic disturbance, the acidosis is accompanied by a fall in acidosis is accompanied by a fall in the ratio [HCO3-]:PCO2the ratio [HCO3-]:PCO2..

IN acute respiratory failure, both the IN acute respiratory failure, both the erythrocyte and renal tubular erythrocyte and renal tubular mechanisms increase the rate of mechanisms increase the rate of generation as soon as the PCO2 risesgeneration as soon as the PCO2 rises ..

In the short term renal contribution to In the short term renal contribution to HCOHCO33

--

production is limited by timeproduction is limited by time..

A relatively large proportion of the slight A relatively large proportion of the slight rise in plasma [HCO3-] is derived from rise in plasma [HCO3-] is derived from erythrocytes because, in normal erythrocytes because, in normal circumstances, the Hb buffering circumstances, the Hb buffering mechanism is not saturatedmechanism is not saturated..

This degree of compensation is rarely This degree of compensation is rarely adequate to prevent a fall in PHadequate to prevent a fall in PH..

Management of Management of respiratory acidosisrespiratory acidosis

the blood findings in a respiratory the blood findings in a respiratory acidosis are as followacidosis are as follow; ;

11--PCO2 is always raisedPCO2 is always raised..

-*-*In acute respiratory failureIn acute respiratory failure::

- -PH is lowPH is low

[[HCOHCO33-- ] ]is high-normal or slightly raisedis high-normal or slightly raised..——

-*-*In chronic respiratory failureIn chronic respiratory failure::

--

--PH is normal or low , depending upon PH is normal or low , depending upon chronicitychronicity..

[--[--HCOHCO33-- ] ]is raisedis raised

alkalosisalkalosis

alkalosis occurs if there is rise in the ratio alkalosis occurs if there is rise in the ratio [HCO3-]:PCO2 in the extracellular fluid[HCO3-]:PCO2 in the extracellular fluid..

In metabolic alkalosis the primary In metabolic alkalosis the primary abnormality in the bicarbonate buffer abnormality in the bicarbonate buffer system is arise in [HCO3-]system is arise in [HCO3-]..

There is little compensatory change in There is little compensatory change in PCO2PCO2

11--In respiratory alkalosisIn respiratory alkalosis the the primary abnormality is a fall in the primary abnormality is a fall in the PCO2PCO2..

----The compensatory change is a fall in The compensatory change is a fall in [HCO3-][HCO3-]..----

----As the primary products of As the primary products of metabolism are H+ and CO2, not OH- metabolism are H+ and CO2, not OH- and HCO3-, and HCO3-, thereforetherefore alkalosis is alkalosis is less common than acidosisless common than acidosis..

22 - -Metabolic alkalosisMetabolic alkalosis..

A primary rise in plasma [HCO3-] A primary rise in plasma [HCO3-] may occur in the following may occur in the following situationsituation::

11--Bicarbonate administration, such Bicarbonate administration, such as the ingestion of large amounts as the ingestion of large amounts of HCO3- to treat indigestionof HCO3- to treat indigestion..

22--Severe K+ depletion with generation Severe K+ depletion with generation of HCO3- by the kidneyof HCO3- by the kidney..

33--Loss of H+ if a H+ is excreted a Loss of H+ if a H+ is excreted a HCO3- is gained in the extracellular HCO3- is gained in the extracellular spacespace..

44--Contraction alkalosis, due to thiazide Contraction alkalosis, due to thiazide or loop of diureticor loop of diuretic . .

Management of a Management of a metabolic alkalosismetabolic alkalosis

the arterial blood findings in metabolicthe arterial blood findings in metabolic

alkalosis arealkalosis are::

11--Blood PH highBlood PH high , ,

22[-[-HH++ ] ]lowlow..

33[-[-HCOHCO33-- ] ]raisedraised

44--PCO2 raised in compensationPCO2 raised in compensation

Useful laboratory Useful laboratory investigations in a metabolic investigations in a metabolic alkalosis may includealkalosis may include::

11--Plasma Na+, K+, Cl-,Mg+2, urea Plasma Na+, K+, Cl-,Mg+2, urea and creatinineand creatinine..

22--Blood gasesBlood gases

33 - -urine [Cl-] less than 20 mmol/L urine [Cl-] less than 20 mmol/L the saline-non-responsive formthe saline-non-responsive form..

Respiratory alkalosisRespiratory alkalosis

the primary abnormality in the the primary abnormality in the bicarbonate buffer system in bicarbonate buffer system in respiratory alkalosis is a fall in PCO2respiratory alkalosis is a fall in PCO2..

--This is due to abnormally rapid or This is due to abnormally rapid or deep respiration when the CO2 deep respiration when the CO2 transport capacity of the pulmonary transport capacity of the pulmonary alveoli is relatively normalalveoli is relatively normal..

--The fall in PCO2 reduces the CD The fall in PCO2 reduces the CD activity in renal tubular cells and activity in renal tubular cells and erythrocyteserythrocytes..

--The compensatory fall in plasma The compensatory fall in plasma [HCO3] tends to correct the PH[HCO3] tends to correct the PH

The arterial blood The arterial blood findings in respiratory findings in respiratory alkalosis arealkalosis are::

11--PCO2 is always reducedPCO2 is always reduced..

22[-[-HCO3HCO3 ]- ]-is low-normalis low-normal..

33--PH is raised (uncompensated or PH is raised (uncompensated or partly compensated) or near normal partly compensated) or near normal (fully compensated)(fully compensated)..

Management of respiratory Management of respiratory alkalosisalkalosis

Laboratory tests could includeLaboratory tests could include::

11--blood gasesblood gases

22--plasma [K+] and ionized [Ca+2] plasma [K+] and ionized [Ca+2] may belowmay below. .

33--elevated white cell countelevated white cell count..

44--full blood count to exclude full blood count to exclude anaemiaanaemia..

55--liver function tests when hepatic liver function tests when hepatic failure is suspectedfailure is suspected..

66--exclude salicylate overdose and exclude salicylate overdose and respiratory stimulatantsrespiratory stimulatants..

Compensatory changes in acid-Compensatory changes in acid-base-disturbancesbase-disturbances..

In either metabolic or respiratory acidosisIn either metabolic or respiratory acidosis

the ratio of [HCO3-]:PCO2,and therefore the ratio of [HCO3-]:PCO2,and therefore thethe

PH, can be corrected by change in conc.of PH, can be corrected by change in conc.of the otherthe other

member of the buffer pair in the same member of the buffer pair in the same direction as the primary abnormalitydirection as the primary abnormality..

This compensation may be either This compensation may be either partial or complete, but never over-partial or complete, but never over-compensates isnot PH overshootcompensates isnot PH overshoot..

The compensatory change in a The compensatory change in a metabolic acidosis is a reduction in metabolic acidosis is a reduction in PCO2 by hyperventilation whilst in a PCO2 by hyperventilation whilst in a respiratory acidosis it is arise in respiratory acidosis it is arise in plasma [HCO3-] plasma [HCO3-] BYBY THE ACTION OF THE ACTION OF THE RENAL TUBULESTHE RENAL TUBULES

In a metabolic alkalosis compensation by In a metabolic alkalosis compensation by (no fully but relativly compensate)(no fully but relativly compensate)..

SlightlySlightly hyp hypooventilation results in an ventilation results in an elevation ofelevation of

PCO2, whilst in a respiratory alkalosis thePCO2, whilst in a respiratory alkalosis the

kidneys increase HCO3- excretion, kidneys increase HCO3- excretion, thereby lowering plasma [HCO3-]thereby lowering plasma [HCO3-]..

----The PH The PH isis a fully compensated a fully compensated in in acidosisacidosis..