Page 711 - Clinical Application of Mechanical Ventilation

Case Studies 677

was slow, indicating poor peripheral perfusion, but the extremities were warm.
The anterior fontanel was soft with slightly overlapping sutures. Breath sounds were
The blood gases show diminished bilaterally.
oxygenation failure because
the PaO 2 is far below normal Arterial blood was drawn from the UAC while on the ventilator with a set fre-
and the PaCO 2 of 48 mm Hg is quency of 40/min, PIP/PEEP of 28/4 cm H O, and 100% oxygen. The blood
only slightly above normal. 2
gas results were:
UAC Sample
pH 7.28
PaCO 2 48 mm Hg
PaO 2 22 mm Hg
-
HCO 21.6 mEq/L
3
Several tests are B.E. 27.2 mEq/L
available to confirm PPHN,
including physical exam, labil- Mode SIMV
ity of oxygenation, preductal FO 100%
and postductal oxygenation I 2
saturation measurements PIP 28 mm Hg
(5% difference2PDA PEEP 4 cm H O
presents with a greater 2
difference in pre-/postductal f 40/min
oxygen saturations), chest
radiograph, and color Doppler Doppler echocardiography confirmed the presence of PPHN as indicated by the
echocardiography.
pre- and postductal saturation measurements.
During a 24-hour period, unsuccessful attempts were made to decrease the oxy-
gen requirement. Very little progress was seen in the patient as the pulmonary hy-
pertension was not resolved using the hyperventilation strategy. Inhaled nitric oxide
(iNO) therapy was started in the hope of reversing the pulmonary hypertension.
The patient received 55 ppm (parts per million) of iNO, and the blood gases
after 1 hour of iNO therapy showed:
UAC Sample
pH 7.45
PaCO 2 35 mm Hg
PaO 2 105 mm Hg
Mode SIMV
PIP/PEEP 32/6 cm H O
2
f 45/min
T INSP 0.24 sec
FO 2 85%
I
The infant’s FO requirement continued to decrease over the next 48 hours.
2
I
iNO therapy was discontinued and the FO was weaned to 45%. Conventional
2
I
ventilation continued at a frequency of 45/min.
Patient Management

The pulmonary vascular resistance of the infant was increased due to severe hy-
poxemia and hypoxic vasoconstriction. Since hypoxemia could not be reversed
with oxygen and ventilation, long-standing hypoxemia caused a persistent increase

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