USMLE Forum Archives - USMLE Step 2 CK - IM 3
IM 3
TheOne - 10-27-06 14:43
A 92-year-old man with a 45-year history of chronic obstructive pulmonary disease is intubated
in the intensive care unit because of a bout of viral pneumonia that fails to improve after 72
hours of antibiotics. Although the inspired fraction of oxygen is 100%, the patient's pO2
remains at 57 mm Hg. Positive-end expiratory pressure (PEEP) is added to allow the inspired
fraction of oxygen. Twelve hours after the introduction of PEEP the patient suddenly becomes
hypotensive. At the same time, his oxygen saturation drops from 92% to 61%. On physical
examination, his blood pressure is 80/50 mm Hg, and his pulse is 124/min. He had distended
neck veins and distant heart sounds. Which of the following would also most likely be seen on
this patient's physical examination?
A. Absence of breath sounds in the right hemithorax
B. High amplitude carotid artery upstroke
C. A pleural friction rub
D. Pulsus alternans
E. Splenomegaly
TheOne - 10-27-06 14:43
A 92-year-old man with a 45-year history of chronic obstructive pulmonary disease is intubated
in the intensive care unit because of a bout of viral pneumonia that fails to improve after 72
hours of antibiotics. Although the inspired fraction of oxygen is 100%, the patient's pO2
remains at 57 mm Hg. Positive-end expiratory pressure (PEEP) is added to allow the inspired
fraction of oxygen. Twelve hours after the introduction of PEEP the patient suddenly becomes
hypotensive. At the same time, his oxygen saturation drops from 92% to 61%. On physical
examination, his blood pressure is 80/50 mm Hg, and his pulse is 124/min. He had distended
neck veins and distant heart sounds. Which of the following would also most likely be seen on
this patient's physical examination?
A. Absence of breath sounds in the right hemithorax
B. High amplitude carotid artery upstroke
C. A pleural friction rub
D. Pulsus alternans
E. Splenomegaly
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#2
Re: IM 3 sebjudmd - 10-28-06 15:44 ptx- I think.
you know I have 3 days till my test, and I am more nervous than in any duties when I realiesed a ptx at any patientes.
#3
Re: IM 3 sebjudmd - 10-28-06 15:45 ptx- I think.
you know I have 3 days till my test, and I am more nervous than in any duties when I realiesed a ptx at any patientes.
#4
ptx indeed
TheOne - 10-29-06 15:56 The correct answer is A. This patient will also likely have absent breath sounds in the
right hemithorax. The question clearly describes the sudden hemodynamic collapse in a
patient who has developed a tension pneumothorax while being given positive-end
expiratory pressure (PEEP) on a respirator. The sudden hypotension and decreased
oxygenation is consistent with a tension pneumothorax, which is compressing venous
return to the right side of the heart and thus producing jugular venous distention. The
treatment would be the immediate placement of either a needle or tube thoracostomy to
allow rapid re-expansion of the right lung.
A high amplitude cardiac upstroke pulse (choice B) is usually seen in conditions such as
aortic regurgitation, in which extra blood must be pushed into the aorta to compensate
for backflow into the heart during diastole through an incompetent valve.
A pleural friction rub (choice C) suggests inflammation of the pleura, which can be seen
either when an underlying lung process involves the lung tissue adjacent to the pleura or
when infection or irritating substances are present in the pleural space. It would not be
expected in the setting of a pneumothorax, in which the visceral pleura becomes
separated from the parietal pleura by a large volume of air.
Pulsus alternans (choice D), also known as alternating pulse, is a pulse in which the
beat is regular but alternate beats are weaker or stronger. It usually indicates serious
myocardial disease.
Splenomegaly (choice E) is not usually a feature of tension pneumothorax because the
venous return from the abdomen enters the heart through the inferior vena cava, which
is much less affected by the pneumothorax than is the superior vena cava.
#6
Re: IM 3 bingousmle - 07-20-10 01:56 the patient is at risk for developing pneumothorax due to the high value and duration of PEEP ... the sudden deterioration of vitals suggests absence of breath sounds in right hemithorax
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