Page 682 - Clinical Application of Mechanical Ventilation

648 Chapter 19

Weaning

Several days later, the patient’s oxygen was weaned to 45% and frequency of 22/min.
For ventilator patients Her condition continued to improve over time and the RCPs were also able to wean
requiring high F I O 2 and PEEP,
wean F I O 2 to about 40% the PEEP to 15 cm H O. Blood gases on these settings revealed:
2
before weaning PEEP.
pH 7.58
PaCO 2 26 mm Hg
PaO 2 87 mm Hg
SaO 2 96%
-
HCO 23.5 mEq/L
3
B.E. 3.3 mEq/L
Hb 11.7 g %
CaO 2 15.8 vol %
Mode IR-PCV
f 22/min
PIP 30 cm H O
2
F O 2 45%
I
PEEP 15 cm H O
2
At this point, she was removed from pressure-controlled ventilation and allowed
to awaken. As her spontaneous breathing resumed, she was quickly weaned to con-
tinuous positive airway pressure (CPAP) with 5 cm H O of PEEP and pressure
2
support of 20 cm H O without difficulty. She maintained a frequency of less than
2
24/min with tidal volumes of about 300 mL. As her muscular effort improved, tidal
volume increased and her pressure support was titrated to maintain the same tidal
During a weaning volume and assure adequate alveolar ventilation and lung expansion.
attempt, the pressure support
level should be titrated to At night, she was rested on assist/control at a V of 600 mL, backup frequency of
T
obtain a desired spontaneous 12/min. She maintained a spontaneous frequency of 14/min. This regimen contin-
V T or f.
ued for the next 3 days where she was placed on CPAP with pressure support titrated
to assist her spontaneous tidal volumes during the day, and rested during the night.
Spontaneous parameters were obtained each morning to determine suitability to
wean and monitor her effort to breathe on her own. Eventually, rather than return-
ing to assist/control, she was able to tolerate synchronized intermittent mandatory
ventilation (SIMV) mode with pressure support of 15 cm H O during the night.
2
The following day, she remained on CPAP with 20 cm H O of pressure support
2
throughout the next 36 hours, without signs of respiratory insufficiency or distress.
She was evaluated for extubation, and her spontaneous respiratory parameters
over the last 5 days were:
Day 1: f 5 50 V 5 14.8 L V 5 0.3 L VC 5 0.80 L
E
T
MIP 5 246 f/V 5 167
T
Day 2: f 5 40 V 5 10.6 L V 5 0.27 L VC 5 0.85 L
T
E
MIP 5 248 f/V 5 148
T
Day 3: f 5 37 V 5 9.5 L V 5 0.26 L VC 5 0.87 L
E
T
MIP 5 256 f/V 5 142
T

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