Page 703 - Clinical Application of Mechanical Ventilation

Case Studies 669

Initial Settings

She was started on volume-controlled ventilation in assist/control (A/C)
mode, backup frequency of 12/min, tidal volume of 400 mL (approx. 8 mL/Kg),
PEEP of 5 cm H O, and an F O of 35%. ABGs drawn 30 min later revealed
2
2
I
the following:
pH 7.55
PaCO 2 25 mm Hg
PaO 2 120 mm Hg
SaO 2 96%
-
HCO 21.1 mEq/L
3
Mode A/C
f 12/min
Spont f 22/min
V T 400 mL
F O 2 35%
I
PEEP 5 cm H O
2
Based on these results, the frequency was decreased to 8/min and the F O was re-
2
I
duced to 30%. ABGs were ordered for the following morning. The results showed:
pH 7.43
PaCO 2 37 mm Hg
PaO 2 110 mm Hg
SaO 2 97%
-
HCO 23.6 mEq/L
3
Mode A/C
f 8/min
Spont f 12/min
V T 400 mL
F O 2 30%
I
f 5 cm H O
2
The patient remained febrile and weak as manifested by serial MIPs. On the
5th ventilator day, the patient underwent an elective tracheostomy for comfort and
to prevent development of septic sinusitis from prolonged nasal intubation. She
tolerated the procedure well.

Patient Monitoring

Her respiratory mechanics showed no signs of improvement through the first week
to 10 days but gradually improved over time. She was monitored for progressive
muscle strength with serial forced vital capacities (FVC) and maximum inspira-
tory pressure (MIP) measurements while on CPAP every morning, which indicated
gradual improvement. The serial measurements are listed in Table 19-2. The patient

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