DR BINOD KUMAR SINGHDR BINOD KUMAR SINGH Associate Professor, PMCH, PatnaAssociate Professor, PMCH, Patna

CIAP Executive board member- 2015 CIAP Executive board member- 2015 NNF State president,Bihar- 2014NNF State president,Bihar- 2014

IAP State secretary,Bihar-2010-2011IAP State secretary,Bihar-2010-2011 NNF State secretary,Bihar-2008-2009NNF State secretary,Bihar-2008-2009

- - Consultant Neonatologist & PediatricianConsultant Neonatologist & Pediatrician

Shiv Shishu Hospital :K-208, P.C Colony.Hanuman Nagar, Patna – Shiv Shishu Hospital :K-208, P.C Colony.Hanuman Nagar, Patna – 800020800020

Web site : www.shivshishuhospital.comWeb site : www.shivshishuhospital.com

ABG ABG INTERPRETATIONINTERPRETATION

ABG InterpretationABG Interpretation

First, does the patient have an First, does the patient have an acidosis or an alkalosisacidosis or an alkalosis

Second, what is the primary problem Second, what is the primary problem – metabolic or respiratory– metabolic or respiratory

Third, is there any compensation by Third, is there any compensation by the patient – respiratory the patient – respiratory compensation is immediate while compensation is immediate while renal compensation takes timerenal compensation takes time

ABG InterpretationABG Interpretation

It would be extremely unusual for It would be extremely unusual for either the respiratory or renal system either the respiratory or renal system to overcompensateto overcompensate

The pH determines the primary The pH determines the primary problemproblem

After determining the primary After determining the primary problem and compensatory problem and compensatory acid/base balance, always evaluate acid/base balance, always evaluate the effectiveness of oxygenationthe effectiveness of oxygenation

Normal ValuesNormal Values

pH - 7.35 to 7.45pH - 7.35 to 7.45paCOpaCO2- 2- 36 to 44 mm Hg 36 to 44 mm Hg

HCOHCO33 -22 to 26 meq/L -22 to 26 meq/L

Abnormal ValuesAbnormal Values

pH < 7.35pH < 7.35 Acidosis (metabolic Acidosis (metabolic

and/or respiratory)and/or respiratory)

pH > 7.45pH > 7.45 Alkalosis (metabolic Alkalosis (metabolic

and/or respiratory)and/or respiratory)

paCOpaCO22 > 44 mm Hg > 44 mm Hg Respiratory Respiratory

acidosis (alveolar acidosis (alveolar hypoventilation)hypoventilation)

paCOpaCO22 < 36 mm Hg < 36 mm Hg Respiratory Respiratory

alkalosis (alveolar alkalosis (alveolar hyperventilation)hyperventilation)

HCOHCO33 < 22 meq/L < 22 meq/L Metabolic acidosis Metabolic acidosis

HCOHCO33 > 26 meq/L > 26 meq/L Metabolic alkalosisMetabolic alkalosis

Putting It Together - Putting It Together - RespiratoryRespiratory

SoSo

paCOpaCO22 > 44 with a pH < 7.35 represents a > 44 with a pH < 7.35 represents a respiratory acidosisrespiratory acidosis

paCOpaCO22 < 36 with a pH > 7.45 represents a < 36 with a pH > 7.45 represents a respiratory alkalosisrespiratory alkalosis

For a primary respiratory problem, pH and For a primary respiratory problem, pH and paCOpaCO22 move in the opposite direction move in the opposite direction For each deviation in paCOFor each deviation in paCO22 of 10 mm Hg in of 10 mm Hg in

either direction, 0. 08 pH units change in the either direction, 0. 08 pH units change in the opposite directionopposite direction

Putting It Together - Putting It Together - MetabolicMetabolic

AndAnd

HCOHCO33 < 22 with a pH < 7.35 < 22 with a pH < 7.35 represents a metabolic acidosis represents a metabolic acidosis

HCOHCO33 > 26 with a pH > 7.45 > 26 with a pH > 7.45 represents a metabolic alkalosisrepresents a metabolic alkalosis

For a primary metabolic problem, pH For a primary metabolic problem, pH and HCOand HCO33 are in the same direction, are in the same direction, and paCOand paCO22 is also in the same is also in the same directiondirection

CompensationCompensation

The body’s attempt to return the The body’s attempt to return the acid/base status to normal (i.e. pH acid/base status to normal (i.e. pH closer to 7.4)closer to 7.4)

Primary ProblemPrimary Problem CompensationCompensation

respiratory acidosisrespiratory acidosismetabolic alkalosismetabolic alkalosis

respiratory alkalosisrespiratory alkalosis metabolic metabolic acidosisacidosis

metabolic acidosismetabolic acidosis respiratory alkalosisrespiratory alkalosis

metabolic alkalosismetabolic alkalosis respiratory acidosisrespiratory acidosis

REMEMBER BY HEARTREMEMBER BY HEART

CO2 IS A RESPIRATORY ACIDCO2 IS A RESPIRATORY ACIDPh and HCO3- Move in same direction.Ph and HCO3- Move in same direction.pH and PCO2- Move in opposite pH and PCO2- Move in opposite

direction.direction.HCO3 and PCO2- Move in same HCO3 and PCO2- Move in same

direction-simple disorder.direction-simple disorder.HCO3 and PCO2- Move in opposite HCO3 and PCO2- Move in opposite

direction-mixed disorder. direction-mixed disorder.

Expected CompensationExpected Compensation

Respiratory acidosisRespiratory acidosisAcute – the pH decreases 0.08 units for Acute – the pH decreases 0.08 units for

every 10 mm Hg increase in paCOevery 10 mm Hg increase in paCO22; ; HCOHCO33 1 mEq/liter per 1 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22

Chronic – the pH decreases 0.03 units Chronic – the pH decreases 0.03 units for every 10 mm Hg increase in paCOfor every 10 mm Hg increase in paCO22; ; HCOHCO33 4 mEq/liter per 4 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22

Expected CompensationExpected Compensation

Respiratory alkalosisRespiratory alkalosisAcute – the pH increases 0.08 units for Acute – the pH increases 0.08 units for

every 10 mm Hg decrease in paCOevery 10 mm Hg decrease in paCO22; ; HCOHCO33 2 mEq/liter per 2 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22

Chronic - the pH increases 0.03 units for Chronic - the pH increases 0.03 units for every 10 mm Hg decrease in paCOevery 10 mm Hg decrease in paCO22; ; HCOHCO33 4 mEq/liter per 4 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22

Expected CompensationExpected Compensation

Metabolic acidosisMetabolic acidosispaCOpaCO22 = 1.5(HCO = 1.5(HCO33) + 8 () + 8 (2)-winter’s 2)-winter’s

formulaformulapaCOpaCO22 1-1.5 per 1-1.5 per 1 mEq/liter HCO1 mEq/liter HCO33

Metabolic alkalosisMetabolic alkalosispaCOpaCO22 = 0.7(HCO = 0.7(HCO33) + 20 () + 20 (1.5)1.5)

paCOpaCO22 0.5-1.0 per 0.5-1.0 per 1 mEq/liter HCO1 mEq/liter HCO33

Classification of primary acid-Classification of primary acid-base disturbances and base disturbances and

compensationcompensation Acceptable ventilatory and metabolic acid-Acceptable ventilatory and metabolic acid-

base statusbase status Respiratory acidosis (alveolar Respiratory acidosis (alveolar

hypoventilation) - acute, chronic hypoventilation) - acute, chronic Respiratory alkalosis (alveolar Respiratory alkalosis (alveolar

hyperventilation) - acute, chronichyperventilation) - acute, chronic Metabolic acidosis – uncompensated, Metabolic acidosis – uncompensated,

compensated compensated Metabolic alkalosis – uncompensated, Metabolic alkalosis – uncompensated,

partially compensatedpartially compensated

Acute Respiratory AcidosisAcute Respiratory Acidosis

paCOpaCO22 is elevated and pH is acidotic is elevated and pH is acidoticThe decrease in pH is accounted for The decrease in pH is accounted for

entirely by the increase in paCOentirely by the increase in paCO22

Bicarbonate and base excess will be Bicarbonate and base excess will be in the normal range because the in the normal range because the kidneys have not had adequate time kidneys have not had adequate time to establish effective compensatory to establish effective compensatory mechanismsmechanisms

Acute Respiratory AcidosisAcute Respiratory Acidosis

CausesCausesRespiratory pathophysiology - airway Respiratory pathophysiology - airway

obstruction, severe pneumonia, chest obstruction, severe pneumonia, chest trauma/pneumothoraxtrauma/pneumothorax

Acute drug intoxication (narcotics, Acute drug intoxication (narcotics, sedatives)sedatives)

Residual neuromuscular blockadeResidual neuromuscular blockadeCNS disease (head trauma)CNS disease (head trauma)

Chronic Respiratory AcidosisChronic Respiratory Acidosis

paCOpaCO22 is elevated with a pH in the is elevated with a pH in the acceptable rangeacceptable range

Renal mechanisms increase the Renal mechanisms increase the excretion of Hexcretion of H++ within 24 hours and within 24 hours and may correct the resulting acidosis may correct the resulting acidosis caused by chronic retention of COcaused by chronic retention of CO2 2 to to a certain extenta certain extent

Chronic Respiratory AcidosisChronic Respiratory Acidosis

CausesCausesChronic lung disease (BPD, COPD)Chronic lung disease (BPD, COPD)Neuromuscular diseaseNeuromuscular diseaseExtreme obesityExtreme obesityChest wall deformityChest wall deformity

Acute Respiratory AlkalosisAcute Respiratory Alkalosis

paCOpaCO22 is low and the pH is alkalotic is low and the pH is alkaloticThe increase in pH is accounted for The increase in pH is accounted for

entirely by the decrease in paCOentirely by the decrease in paCO22

Bicarbonate and base excess will be Bicarbonate and base excess will be in the normal range because the in the normal range because the kidneys have not had sufficient time kidneys have not had sufficient time to establish effective compensatory to establish effective compensatory mechanismsmechanisms

Respiratory AlkalosisRespiratory Alkalosis

CausesCauses PainPain AnxietyAnxiety HypoxemiaHypoxemia Restrictive lung Restrictive lung

diseasedisease Severe congestive Severe congestive

heart failureheart failure Pulmonary emboliPulmonary emboli

DrugsDrugs SepsisSepsis FeverFever ThyrotoxicosisThyrotoxicosis PregnancyPregnancy Overaggressive Overaggressive

mechanical mechanical ventilationventilation

Hepatic failureHepatic failure

Uncompensated Metabolic Uncompensated Metabolic AcidosisAcidosis

Normal paCONormal paCO22, low HCO, low HCO33, and a pH , and a pH less than 7.30less than 7.30

Occurs as a result of increased Occurs as a result of increased production of acids and/or failure to production of acids and/or failure to eliminate these acidseliminate these acids

Respiratory system is not Respiratory system is not compensating by increasing alveolar compensating by increasing alveolar ventilation (hyperventilation)ventilation (hyperventilation)

Compensated Metabolic Compensated Metabolic AcidosisAcidosis

paCOpaCO22 less than 30, low HCO less than 30, low HCO33, with a , with a pH of 7.3-7.4pH of 7.3-7.4

Patients with chronic metabolic Patients with chronic metabolic acidosis are unable to hyperventilate acidosis are unable to hyperventilate sufficiently to lower paCOsufficiently to lower paCO22 for for complete compensation to 7.4complete compensation to 7.4

Elevated AGElevated AGMetabolic AcidosisMetabolic Acidosis

CausesCausesKetoacidosis - diabetic, alcoholic, Ketoacidosis - diabetic, alcoholic,

starvationstarvationLactic acidosis - hypoxia, shock, sepsis, Lactic acidosis - hypoxia, shock, sepsis,

seizuresseizuresToxic ingestion - methanol, ethylene Toxic ingestion - methanol, ethylene

glycol, ethanol, isopropyl alcohol, glycol, ethanol, isopropyl alcohol, paraldehyde, tolueneparaldehyde, toluene

Renal failure - uremiaRenal failure - uremia

Normal AG Metabolic AcidosisNormal AG Metabolic Acidosis

CausesCauses Renal tubular Renal tubular

acidosisacidosis Post respiratory Post respiratory

alkalosisalkalosis HypoaldosteronismHypoaldosteronism Potassium sparing Potassium sparing

diureticsdiuretics Pancreatic loss of Pancreatic loss of

bicarbonatebicarbonate

DiarrhoeaDiarrhoea Carbonic anhydrase Carbonic anhydrase

inhibitorsinhibitors Acid administration Acid administration

(HCl, NH(HCl, NH44Cl, Cl, arginine HCl)arginine HCl)

SulfamylonSulfamylon CholestyramineCholestyramine Ureteral diversionsUreteral diversions

Effectiveness of OxygenationEffectiveness of Oxygenation

Further evaluation of the arterial blood gas Further evaluation of the arterial blood gas requires assessment of the effectiveness requires assessment of the effectiveness of oxygenation of the bloodof oxygenation of the blood

Hypoxemia – decreased oxygen content of Hypoxemia – decreased oxygen content of blood - paOblood - paO22 less than 60 mm Hg and the less than 60 mm Hg and the saturation is less than 90%saturation is less than 90%

Hypoxia – inadequate amount of oxygen Hypoxia – inadequate amount of oxygen available to or used by tissues for available to or used by tissues for metabolic needsmetabolic needs

Mechanisms of HypoxemiaMechanisms of Hypoxemia

Inadequate inspiratory partial Inadequate inspiratory partial pressure of oxygenpressure of oxygen

HypoventilationHypoventilationRight to left shuntRight to left shuntVentilation-perfusion mismatchVentilation-perfusion mismatch Incomplete diffusion equilibriumIncomplete diffusion equilibrium

Assessment of Gas ExchangeAssessment of Gas Exchange

Alveolar-arterial OAlveolar-arterial O22 tension difference tension difference A-a gradientA-a gradient PAOPAO22-PaO-PaO22

PAOPAO22 = FiO = FiO22(BP - PH(BP - PH22O) - PaCOO) - PaCO22/RQ*/RQ* Arterial-Alveolar OArterial-Alveolar O22 tension ratio tension ratio

PaOPaO22/PAO/PAO22

Arterial-Inspired OArterial-Inspired O22 ratio ratio PaOPaO22/FIO/FIO2 2 * *

Respiratary quotient= 0.8 Respiratary quotient= 0.8

Assessment of Gas ExchangeAssessment of Gas Exchange

A-a DO2={(FIO2)(760-47)-(1.25)(PaCO2)}-A-a DO2={(FIO2)(760-47)-(1.25)(PaCO2)}-PaO2PaO2

Normal A-a gradient -10-20 mm HgNormal A-a gradient -10-20 mm Hg Increased A-a gradient with hypoxemia- Increased A-a gradient with hypoxemia-

oxygenation failure /V-Q mismatch/lung oxygenation failure /V-Q mismatch/lung disorderdisorder

Normal A a gradient with hypoxemia- Normal A a gradient with hypoxemia- ventilation failure/hypoventilationventilation failure/hypoventilation

Assessment of Gas ExchangeAssessment of Gas ExchangeABGABG A-a gradA-a grad

PaOPaO22 PaCOPaCO22 RARA 100%100%

Low FIOLow FIO22 N*N* NN

Alveolar hypoventilationAlveolar hypoventilation NN NN

Altered gas exchangeAltered gas exchange

Regional V/Q mismatchRegional V/Q mismatch /N//N/ N/N/ Intrapulmonary R to L shuntIntrapulmonary R to L shunt N/N/ Impaired diffusionImpaired diffusion N/N/ NN

Anatomical R to L shuntAnatomical R to L shunt

(intrapulmonary or intracardiac)(intrapulmonary or intracardiac) N/N/ * N=normal* N=normal

INDICATION FOR ECMOINDICATION FOR ECMO

IF iNO VENTILATION INCLUDING HFO VENTILATION UNABLE TO SUSTAIN LIFE

IF AO2-aO2 GRADIENT OF MORE THAN 600 mmHg FOR 6 TO 12 hrs

VENTILATION INDEX= [ (RR * PIP * paCO2 ) / 1000 ] , of more than 90 for 4 hr

OXYGENATION INDEX= (MAP * FiO2) Post-ductal paO2

, of more than 40 in two ABGs at 1 hr apart

ABG REPORT - SHIV SHISHU HOSPITAL PATNAABG REPORT - SHIV SHISHU HOSPITAL PATNA DATE/TIME 27:07:2011 12:12DATE/TIME 27:07:2011 12:12 SAMPLE No- 5388SAMPLE No- 5388 Pat ID B N 5 Pat ID B N 5 Sample type arterial blood Sample type arterial blood BARO- 747.2mm HgBARO- 747.2mm Hg Temp- 37.0 CTemp- 37.0 C A/F FETALA/F FETAL PO2 82.5 mmHg(80.0-100.0PO2 82.5 mmHg(80.0-100.0 PCO2 36 mmHg(-)(35.0-45.0)PCO2 36 mmHg(-)(35.0-45.0) pH 7.393 (7.350-7.450)pH 7.393 (7.350-7.450) Na 143.1 mmol/L(135.0-148.0)Na 143.1 mmol/L(135.0-148.0) Cl 104.1 mmol/L(98.0-107.0)Cl 104.1 mmol/L(98.0-107.0) Ica 1.267 mmol/L(1.120-1.320)Ica 1.267 mmol/L(1.120-1.320) K 3.74 mmol/L(3.50-4.50) K 3.74 mmol/L(3.50-4.50) Hct 49.7 % (35.0-50.0)Hct 49.7 % (35.0-50.0) BE -3.6 mmol/LBE -3.6 mmol/L BEecf -4.5 mmol/LBEecf -4.5 mmol/L CHCO3st 23 mmol/LCHCO3st 23 mmol/L P50 21.5 mmHgP50 21.5 mmHg ctO2 20.7 vol%ctO2 20.7 vol%

ABG REPORT- SHIV SHISHU HOSPITAL PATNAABG REPORT- SHIV SHISHU HOSPITAL PATNA

DATE/TIME 27:07:2011 12:17DATE/TIME 27:07:2011 12:17 SAMPLE No- 5389SAMPLE No- 5389 Pat ID B N 15Pat ID B N 15

Sample type arterial Blood Sample type arterial Blood BARO- 747.0mm HgBARO- 747.0mm Hg Temp- 37.0 CTemp- 37.0 C A/F FETALA/F FETAL PO2 153.2 mmHg(+)(80.0-100.0)PO2 153.2 mmHg(+)(80.0-100.0) PCO2 59.3 mmHg(+)(35.0-45.0)PCO2 59.3 mmHg(+)(35.0-45.0) pH 7.262 (7.350-7.450)pH 7.262 (7.350-7.450) Na 136.3 mmol/L(135.0-148.0)Na 136.3 mmol/L(135.0-148.0) Cl 99.4 mmol/L(98.0-107.0)Cl 99.4 mmol/L(98.0-107.0) Ica 0.977 mmol/L(--)(1.120-1.320)Ica 0.977 mmol/L(--)(1.120-1.320) K 4.38 mmol/L(3.50-4.50) K 4.38 mmol/L(3.50-4.50) Hct 38.4 % (35.0-50.0)Hct 38.4 % (35.0-50.0) BE -2.1 mmol/LBE -2.1 mmol/L BEecf -0.9 mmol/LBEecf -0.9 mmol/L CHCO3st 22.1 mmol/LCHCO3st 22.1 mmol/L P50 21.5 mmHgP50 21.5 mmHg ctO2 21.2 vol%ctO2 21.2 vol%

ABG REPORT-S SHIV SHISHU HOSPITAL PATNAABG REPORT-S SHIV SHISHU HOSPITAL PATNA

DATE/TIME 27:07:2011 11:08DATE/TIME 27:07:2011 11:08 SAMPLE No- 5386SAMPLE No- 5386 Pat ID B N 3Pat ID B N 3

Sample type arterial Blood Sample type arterial Blood BARO- 747.2mm HgBARO- 747.2mm Hg Temp- 37.0 CTemp- 37.0 C A/F FETALA/F FETAL PO2 57.5 mmHg(--)(80.0-100.0)PO2 57.5 mmHg(--)(80.0-100.0) PCO2 26.6 mmHg(-)(35.0-45.0)PCO2 26.6 mmHg(-)(35.0-45.0) pH 7.482 (+) (7.350-7.450)pH 7.482 (+) (7.350-7.450) Na 139.6 mmol/L(135.0-148.0)Na 139.6 mmol/L(135.0-148.0) Cl 101.0 mmol/L(98.0-107.0)Cl 101.0 mmol/L(98.0-107.0) Ica 1.006 mmol/L(--)(1.120-1.320)Ica 1.006 mmol/L(--)(1.120-1.320) K 3.41 mmol/L(3.50-4.50) K 3.41 mmol/L(3.50-4.50) Hct 57.3 %(+) (35.0-50.0)Hct 57.3 %(+) (35.0-50.0) BE -2.3 mmol/LBE -2.3 mmol/L BEecf -4.0 mmol/LBEecf -4.0 mmol/L CHCO3st 22.4 mmol/LCHCO3st 22.4 mmol/L P50 21.5 mmHgP50 21.5 mmHg ctO2 20.2 vol%ctO2 20.2 vol%

ABG REPORT- SHIV SHISHU HOSPITAL PATNAABG REPORT- SHIV SHISHU HOSPITAL PATNA

DATE/TIME 27:07:2011 20:16DATE/TIME 27:07:2011 20:16 SAMPLE No- 5324SAMPLE No- 5324 Pat ID B N 5Pat ID B N 5

Sample type arterial Blood Sample type arterial Blood BARO- 740.4mm HgBARO- 740.4mm Hg Temp- 37.0 CTemp- 37.0 C A/F FETALA/F FETAL PO2 52.6 mmHg(--)(80.0-100.0)PO2 52.6 mmHg(--)(80.0-100.0) PCO2 24.6 mmHg(-)(35.0-45.0)PCO2 24.6 mmHg(-)(35.0-45.0) pH 7.255 (-) (7.350-7.450)pH 7.255 (-) (7.350-7.450) Na 134.1 mmol/L(135.0-148.0)Na 134.1 mmol/L(135.0-148.0) Cl 98.7 mmol/L(98.0-107.0)Cl 98.7 mmol/L(98.0-107.0) Ica 1.064 mmol/L(--)(1.120-1.320)Ica 1.064 mmol/L(--)(1.120-1.320) K 3.95 mmol/L(3.50-4.50) K 3.95 mmol/L(3.50-4.50) Hct 56.8 %(+) (35.0-50.0)Hct 56.8 %(+) (35.0-50.0) BE -14.5 mmol/LBE -14.5 mmol/L BEecf -16.5 mmol/LBEecf -16.5 mmol/L CHCO3st 13.2 mmol/LCHCO3st 13.2 mmol/L P50 21.5 mmHgP50 21.5 mmHg ctO2 18.7 vol%ctO2 18.7 vol%

SummarySummary

First, does the patient have an acidosis or First, does the patient have an acidosis or an alkalosis an alkalosis Look at the pHLook at the pH

Second, what is the primary problem – Second, what is the primary problem – metabolic or respiratorymetabolic or respiratory Look at the pCOLook at the pCO22

If the pCOIf the pCO22 change is in the opposite direction change is in the opposite direction of the pH change, the primary problem is of the pH change, the primary problem is respiratoryrespiratory

SummarySummary

Third, is there any compensation by Third, is there any compensation by the patient - do the calculationsthe patient - do the calculationsFor a primary respiratory problem, is the For a primary respiratory problem, is the

pH change completely accounted for by pH change completely accounted for by the change in pCOthe change in pCO22if yes, then there is no metabolic if yes, then there is no metabolic

compensationcompensationif not, then there is either partial if not, then there is either partial

compensation or concomitant metabolic compensation or concomitant metabolic problemproblem

SummarySummary

For a metabolic problem, calculate the For a metabolic problem, calculate the expected pCOexpected pCO22if equal to calculated, then there is if equal to calculated, then there is

appropriate respiratory compensationappropriate respiratory compensationif higher than calculated, there is if higher than calculated, there is

concomitant respiratory acidosisconcomitant respiratory acidosisif lower than calculated, there is if lower than calculated, there is

concomitant respiratory alkalosisconcomitant respiratory alkalosis

SummarySummary

Next, don’t forget to look at the Next, don’t forget to look at the effectiveness of oxygenation, (and effectiveness of oxygenation, (and look at the patient)look at the patient)your patient may have a significantly your patient may have a significantly

increased work of breathing in order to increased work of breathing in order to maintain a “normal” blood gasmaintain a “normal” blood gas

metabolic acidosis with a concomitant metabolic acidosis with a concomitant respiratory acidosis is concerningrespiratory acidosis is concerning