75 year old man brought into the ER by family, extremely SOB and speaking in 1 word sentences, using all accessory muscles to breath. Past medical hx of COPD. Worsening breathing over past 3 days with increased volumes of sputum.
Exam:
Markedly increased WOB, appears in distress. Signs of hyperinflation of the chest and is breathing with pursed lips. Breath sounds generally diminished but no adventitious sounds.
Vital Signs:
36-120-26-150/80-81%
ABG/lab results:
H* 39.5 nmol/L (35-45)
pH 7.40 (7.35-7.45)
pCO2 36 mmHg (35-45)
PO2 44mmHg (>80)
Bicarb 23 mmol/L (22-28)
Lytes:
K 4.1 mmol/L (3.5-5)
Na 137 mmol/L (135-145)
Cl 99 mmol/L (95-105)
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Questions
Analyze his ABGs and describe his acid-base status
Should you provide him with supplemental oxygen? Provide rationale
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Answers
Analyze his ABGs and describe his acid-base status
NORMAL ACID-BASE BALANCE, MODERATE RESPIRATORY IMPAIRMENT AS INDICATED BY LOW PO2
Should you provide him with supplemental oxygen? Provide rationale
HE HAS NO INDICATION THAT HE WILL RELY ON HYPOXIC DRIVE (ONLY A PORTION OF COPD PATIENTS HAVE THIS TYPE OF RESPIRATORY IMPAIRMENT)- IN THIS CASE HIS CO2 IS NORMAL AND HIS HCO3 (BICARB) IS NORMAL- SO WE NEED TO GIVE HIM OXYGEN. DO NOT ASSUME 2 L OF O2 IS A MAGICAL AMOUNT- WE WOULD GIVE HIM O2 TO SATS/ABGS THAT INDICATE ADEQUATE OXYGENATION (ADEQUATE IN THE ABSENCE OF ANY SYMPTOM REQUIRING GREATER OXYGENATION SUCH AS CHEST PAIN WOULD BE > 90%, IDEAL IS >95%)
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Patient #2
History
68 year old male with COPD is referred to ER by his GP with a short history of increased breathlessness and reduced effort tolerance. He is normally able to walk about 500 metres, but now has difficulty dressing and is SOB at rest.
Exam:
Alert, mildly distressed, using accessory muscles to breathe through pursed lips. Chest exam reveals hyperinflation and diminished breath sounds throughout, with scattered wheezes.
Initial VS - 37-96-138/82-78%
He is treated with nebulized bronchdilators, oral prednisone, and 60% O2 by FM. His oxygen saturations improve significantly, but when you return to reassess him one hour later, his condition has deteriorated and he is unable to provide a history.
Follow-up Exam:
Drowsy, difficult to rouse. No longer shows signs of respiratory distress, RR 14, chest exam unchanged
VS- 37-88-14-132/80 96%
ABG/lab results:
H* 50.8 (35-45)
pH 7.29 (7.35-7.45)
pCO2 65.3 mmHg (35-45)
PO2 84mmHg (>80)
Bicarb 30.3 mmol/L (22-28)
Lytes:
K 3.6 mmol/L (3.5-5)
Na 144 mmol/L (135-145)
Cl 102 mmol/L
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Questions
What’s going on?
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Answers
WHAT’S GOING ON?
THIS MAN IS EXPERIENCING ACUTE ON CHRONIC RESPIRATORY IMPAIRMENT- ABGS SHOW PARTIALLY COMPENSATED RESP ACIDOSIS. WE CAN TELL THIS BECAUSE HIS pH IS LOW (7.29), HIS PCO2 is high (65.3) and his bicarb is high (30.3). THIS IS THE KIND OF COPD PATIENT WHO’S LIKELY TO POOP OUT AND STOP BREATHING IS WE PROVIDE TOO MUCH SUPPLEMENTAL OXYGEN BECAUSE HE’S RELYING ON HYPOXIC DRIVE TO CONTROL BREATHING.
HOW DO WE KNOW THE DIFFERENCE?
WE SHOULD HAVE DONE ABGS IMMEDIATELY UPON ARRIVAL – THIS IS WHAT THEY WOULD HAVE SHOWN:
pH – 7.36
pCO2- 54.1
pO2- 40
bicarb- 30.6
ABGS PRIOR TO TREATMENT SHOW ELEVATED pCO2 AND ELEVATED BICARB- WITH NORMAL pH- fully compensated respiratory acidosis- remember that it takes time for renal compensation (bicarb) so this suggests it’s chronic.
SO, WHAT HAPPENED AND WHAT SHOULD WE HAVE DONE?
BY GIVING HIM TOO MUCH OXYGEN, WE SUPPRESSED HIS RESPIRATORY DRIVE AND HE’S AT RISK FOR RESPIRATORY FAILURE. HE WILL NEED TO BE TRANSFERRED TO ICU HOPEFULLY TO BE TREATED WITH BIPAP OR IF NECESSARY, INTUBATED.
BOTTOM LINE- NOT ALL PATIENTS WITH COPD ARE THE SAME. INITIAL BASELINE ASSESSMENT REQUIRES ABGS AND OXYGEN SATURATION FOR THIS PERSON CANNOT TAKE THE PLACE OF ABGS (BECAUSE WE NEED TO SEE BICARB ETC). INSTEAD OF USING NP, YOU SHOULD ALWAYS CONSIDER MUCH BETTER CONTROLLED ADMINISTRATION OF OXYGEN- E.G., VIA VENTIMASK (AT 24-28%).
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Of Interest
NEW UK GUIDELINES SUGGEST A TARGET OXYGEN SATURATION OF 88-92% FOR COPD PATIENTS. ADDITIONALLY, USE OF OXYGEN ALERT CARDS BY PATIENTS WHO HAVE A HISTORY OF COPD AND ABG EVIDENCE OF HYPOXIC DRIVE IS PROVING USEFUL. NOTE THAT VENTI MASK IS INDICATED, ALONG WITH USE OF COMPRESSED AIR FOR NEBULIZED TREATMENT (WITH O2 2L NP AT THE SAME TIME AS THE COMPRESSED AIR NEBULIZER)- AND A TIME LIMIT OF 6 MINUTES FOR NEBULIZED TREATMENTS
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Patient #3
History:
36 year old pregnant woman on the maternity ward complains of feeling SOB. She has no other symptoms and no relevant medical history.
Exam:
Patient heavily pregnant but otherwise appears well. Exam of chest reveals no abnormalities
36.6-110-20-112/90
ABG/lab results:
H* 35 nmol/L (35-45)
pH 7.45 (7.35-7.45)
pCO2 35 mmHg (35-45)
PO2 35mmHg (>80)
Bicarb 24 mmol/L (22-28)
Lytes:
K 3.6 mmol/L (3.5-5)
Na 138 mmol/L (135-145)
Cl 104 mmol/L (95-105)
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Questions
Describe her acid-base status?
What is the most likely cause of her low PO2?
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Answers
Describe her acid-base status
NORMAL ACID-BASE STATUS WITH SEVERE HYPOXIA- DOESN’T MAKE SENSE- EVERYTHING ELSE CAN’T BE NORMAL WITH SUCH A LOW PO2- COMPENSATORY MECHANISMS KICK IN!!!
What is the most likely explanation for the low PaO2?
THE SAMPLE IS NOT ARTERIAL BLOOD GAS, IT’S A VENOUS BLOOD SPECIMEN BY ACCIDENT. PATIENT IS ACTUALLY JUST FINE.
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Patient #4
History:
35 year-old female brought to the ER by ambulance after being found in her home unconscious by her 10 year old daughter returning from school. Recent history of “stomach upset” according to the patient’s daughter.
Examination:
Drowsy, peripherally shut down with very dry mucous membranes. Respirations are deep and sighing, she has a funny odour.
36.9-130-26-90/60
ABG/lab results:
H* 35 nmol/L (35-45)
pH 7.05 (7.35-7.45)
pCO2 11 mmHg (35-45)
PO2 187 mmHg (>80)
Bicarb 6.0 mmol/L (22-28)
Lytes:
K 5.3 mmol/L (3.5-5)
Na 141mmol/L (135-145)
Cl 96 mmol/L (95-105)
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Questions
Describe her acid-base status
Using the clues you’ve uncovered, try to create a “clinical picture” of what might be happening
Other than getting help, what do you need to do STAT?
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Answers
Describe her acid-base status
SEVERE PARTIALLY COMPENSATED METABOLIC ACIDOSIS
Using the clues you’ve uncovered, try to create a “clinical picture” of what might be happening
Other than getting help, what do you need to do STAT?