Her current ventilator settings are assist control ac

Her current ventilator settings are assist control (AC), respiratory rate (RR) of
12/min, tidal volume (TV)
of 500 ml, fraction of inspired oxygen (FiO2) is 50%, positive end expiratory
pressures (PEEP) of 5 mm/Hg. The most appropriate intervention at this time is to
A. decrease set respiratory rate
B. increase the fraction of inspired oxygen
C. increase PEEP
D. increase tidal volume
E. make no adjustments at this time
Explanation:
The correct answer is D. The key to this question is to recognize that this patient
remains acidotic
and hypercarbic despite intubation. In order to "blow off" more carbon dioxide and
normalize the
blood pH, you must increase minute ventilation (MV).
If you remember that MV=TV X RR, you can

quickly recognize that the two ways to decrease carbon dioxide is to increase the
RR or increase the TV.
Decreasing RR (choice A) will increase carbon dioxide because we are decreasing
minute
ventilation as described above. This will result in worsening acidosis. In addition,
our set respiratory
rate is lower than the patient's actual rate. If we decreased the respiratory rate, our
patient would
continue to breathe at a high rate and receive the same tidal volume (thereby not
even changing the
MV).
Increasing FiO2 (choice B) will not be beneficial. First, the patient already has a
paO2 of greater
than 60 mm Hg. If you remember the hemoglobin binding curve, you should
remember oxygen
saturations remain above 90% for paO2>60 mm Hg. Therefore, our goal is to keep
paO2>60 mm Hg
for most patients. Second, maintaining patients on greater than 60% oxygen may
have some
associated lung toxicity. Therefore, if possible, keeping the inspired oxygen less
than 60% is an
important part of management. Of course, if high levels of inspired oxygen are
necessary, you should
not hesitate to use them. Please remember that patients on ventilators need not (and
should not) have
oxygen saturations of 100% or paO2 much greater than 60 mm Hg.
PEEP (choice C) is the use of positive airway pressures at the end of expiration.
PEEP is useful in
hypoxic respiratory failure such as ARDS or cardiogenic pulmonary edema. Low
levels of PEEP can
be used in COPD to keep airways open. Our patient's oxygenation is acceptable so
increasing
PEEP would not be beneficial now. In addition, our patients blood pressure is only
borderline
acceptable. Increasing PEEP will decrease venous return to the heart and might lead
to further
reductions in blood pressures. High levels of PEEP might also predispose patients
to barotrauma
which is a form of ventilator induced lung damage.
Making no adjustments (choice E) is not acceptable. This patient is severely
acidotic and
hypercarbic and should not be left in this state.

A 45-year-old woman is planning a trip from the United States to Hong Kong on a
direct flight. She
comes to the office inquiring about advice for any travel precautions that she should
take. She has
fibrocystic disease of the breast and takes oral contraceptive pills. Physical
examination is
unremarkable. Her estimated