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A 78 year old nursing home resident develops sever pneumonia and is placed on a respirator.He is treated with broad spectrum antibiotics for 10 days.Arterial blood gas(ABG’s) on the ninth and eleventh day of hospitalization are shown below ( ventilation parameters unchanged).
PH – 7.34 ; Paco2 – 42 ; Pao2 – 85 ----------------- Day 9
PH – 7.24 ; Paco2 – 60 ; Pao2 – 68 ------------------Day 11
Which of the following is most likely cause of observed ABG changes?
A. Segmental atelectasis
B. Intrapulmonary left to right shunt
C. Worsening infection with increase dead space formation
D. Central hypoventilation
E. Acute drop in hematocrit.
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CCCC. ,
Since in the answer choices there are only two possible result, and I think Segmental atelectasis is too small to create such acidosis.
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it's definitely not D, since the central hypoventilation is caused by drug ODs, or it could be congenital. I don't think it's the case here
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70 years old=centr. hypovent.
sever infection =septicemia=metabolic acidosis,,,,,,,,otherwise if you sure 100% i have no choice,,,good luck
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well first of all u have to define the condition before speculating on the diagnosis; there is hypercapnea and hypoxemia with fall in pH.... this is a case of type 2 resp. failure . This rules out choices of drop in hematocrit and also most probably intrapulmonary shunt (unless it is extremely large which is unlikely). Atelectasis causing VQ mismatch also causes only type 1 and not type 2 and hence is ruled out.
This leaves us with central hypoventilation and increased dead space formation. These 2 or the basic 2 modalities causing type 2 resp. failure i.e. decreased resp. drive and decreased lung volume for gas exchange.
Though as pointed out central hypoventilation can be caused by drugs and genetic causes .... septicemia and also brain injure can cause it ... BUT HEY THE PERSON IS VENTILATED IT DOES"NT MATTER WHETHER HE IS RESPIRING OR NOT .... the choices would have been complicated if they had given a choice of ventilator dysfunction or a Endotracheal tube block ... but otherwise this choice cannot be chosen since the pt. is on a ventilator.
Hence the answer is C. I would like to consider this as a case of ARDS.
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thanks for all the coments correct answer is -----C.
i was like why not pulmonary shunt if its acidosis.and why was it dead space.ok ty.
