Page 661 - Clinical Application of Mechanical Ventilation

Case Studies 627

Patient Management

Adjustments were made to the ventilator settings. The patient was maintained for
CVP is higher than several hours on SIMV of 10/min, V 800 mL, F O 40%, peak flow 45 L/min.
normal. The systemic venous T I 2
volume status should be The patient had no spontaneous ventilation after 6 hours despite being fully alert
monitored closely. and oriented. After the F O was decreased to 40%, the blood gas results were:
2
I
pH 7.40
PaCO 38 mm Hg
Since the patient was 2
a chronic CO 2 retainer, the PaO 2 65 mm Hg
target PaCO 2 (50 mm Hg) SaO 92%
should be used to manage 2
-
this patient. HCO 23 mEq/L
3
Mode SIMV
f 10/min
V T 800 mL
F O 2 40%
I
PEEP 0 cm H O
2
Peak Flow 45 L/min
Fluid intake was adjusted to maintain a CVP reading ,10 mm Hg. Other vital
The PaCO 2 can be signs were within normal limits for her age and condition. Proventil and Intal treat-
increased (from the current
38 mm Hg to patient’s target ments were started for her asthma and her static compliance remained around
50 mm Hg) by decreasing the 70 mL/cm H O.
SIMV frequency or changing 2
to CPAP mode (if patient The spontaneous respiratory parameters 8 hours postsurgery showed MIP 222 cm
can sustain spontaneous H O, vital capacity 700 mL. A trial of CPAP of 5 cm H O at an F O of 40% was
breathing). 2 2 I 2
unsuccessful as she developed periods of apnea with spontaneous tidal volumes of
between 300 and 350 mL.
Over the next several hours, her cardiopulmonary status showed steady improve-
Preexisting asthma, post- ment from the anesthesia effects and the patient was again tried on CPAP. She toler-
anesthesia, and tissue hypoxia
are three major factors that ated the procedure very well this time, and her spontaneous respiratory parameters
lead to failure of CPAP trial. at the end of the CPAP trial were: MIP 240 cm H O, vital capacity 1,500 mL,
2
spontaneous frequency 16, and average V of 476 mL. She was successfully extu-
T
bated and placed on a 50% Venturi mask and eventually weaned to nasal cannula at
3 L/min later that evening.
Some minor complications with the patient’s oxygenation and perfusion status
Since the spontaneous were adequately managed using oxygen, blood, and fluids. Her recovery from the
respiratory frequency (f) and
average V T are 16/min and abdominal exploratory surgery was gradual but uneventful, and she was discharged
0.476 L (476 mL), respectively, from the hospital a few days later.
the f/V T ratio is 34/min/L
(16/0.476). An f/V T ratio of
less than 100/min/L correlates Complications
with weaning success.

The chest radiograph done 16 hours postextubation revealed increasing atelectasis
and pneumonia in both bases with bilateral pleural effusions. Breath sounds showed
increasing crackles with occasional rhonchi and wheezing. Aerosol treatments were
repeated with Proventil TID and prn. Her SpO on 3 L/min of oxygen was consis-
2
tently in the mid- to low-80s and she was placed back on an air-entrainment mask

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