Page 672 - Clinical Application of Mechanical Ventilation

638 Chapter 19

To further minimize pressure-induced lung injuries, the pressure on PCV was fur-
Permissive hypercapnia ther decreased until the tidal volume was about 450 mL. The PaCO was allowed to
is used to reduce the pressure 2
and volume requirement for reach 80 mm Hg (permissive hypercapnia) while the pH was maintained near 7.35
ventilation. by bicarbonate infusion and kidney compensation.

Key Medications

No medication was needed for intubation because the patient was unconscious
at the time of intubation. Additional medications were withheld because of the
uncertain drug interaction with other unknown drugs that the patient might have
taken.
The patient was given neuromuscular blocking agents and sedatives while on me-
chanical ventilation. As the respiratory status improved, the patient was weaned
from these drugs. Albuterol was given prn for wheezing.

Weaning

Over the next 2 weeks, the patient continued to improve. Weaning was done by
alternating CPAP with pressure support (during day) and SIMV (during night).
Both modes of ventilation were supported with flow triggering. The SIMV mode
allowed the patient to rest. He was also ambulated daily to strengthen his respira-
tory muscles and exercise endurance.
MIP . 230 cm H 2 O and As he regained strength, the following spontaneous respiratory parameters
f/V T ratio of less than 100/min/L
correlate with weaning success. were obtained: f ,35/min, minute volume around 9 L, vital capacity .1 L,
MIP .230 cm H O, and f/V ,100/min/L.
T
2
Eventually, the patient was weaned to CPAP of 5 cm H O, F O 35%, and pres-
I
2
2
sure support of 5 cm H O. A spontaneous frequency of 16 to 20/min yielded these
2
ABG results:
pH 7.37
PaCO 2 43 mm Hg
PaO 2 80 mm Hg
-
HCO 24 mEq/L
3
SpO 2 95%
Mode CPAP
PEEP 5 cm H O
2
F O 2 35%
I
PS 5 cm H O
2
Spont f 16 to 20/min

After 2 days of CPAP, the patient continued to improve, he was placed on a nasal
cannula at 4 L/min and his fenestrated tracheostomy tube was buttoned, allowing
the patient to breathe through his upper airway. He tolerated the closure of his
tracheostomy very well, and it was left this way for 2 days. Two days later, he was
transferred to the rehabilitation floor.

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