Page 683 - Clinical Application of Mechanical Ventilation

Case Studies 649

Day 4: f 5 33 V 5 8.2 L V 5 0.3 L VC 5 1.02 L
E
T
MIP 5 257 f/V 5 110
T
Day 5: f 5 32 V 5 10.3 L V 5 0.32 L VC 5 1.14 L
T
E
MIP 5 242 f/V 5 100
T
Extubation decisions are frequently made in conjunction with spontaneous
f/V T of 100/min/L or breathing parameters as well as other clinical indicators that may predict success.
lower suggests readiness for Ideally, every member of the patient care team may give input concerning this
weaning attempt. Rapid shal-
low breathing usually results important decision. The frequency (f) should be below 30/min. The minute vol-
in a high f/V T .
ume (V ) should be around 10 L with a tidal volume of .5 to 8 mL/kg and a vital
E
capacity .10 to 15 mL/kg. The maximum inspiratory pressure (MIP) should be
greater than 220 to 230 cm H O where muscle strength is directly proportional
2
to the volume generated for inspiration. The frequency to tidal volume ratio
(f/V ), sometimes called rapid shallow breathing index (RSBI), measures the pa-
T
An f/V T ratio of less than tient’s volume as compared to the frequency. Patients breathing rapidly with shal-
100 is predictive of weaning low volumes may only ventilate the anatomic deadspace (i.e., conducting zones
success.
within the lungs without effective alveolar ventilation). This ratio, then, should
be below 100/min/L before effective weaning may take place.
Realize, however, that these indicators are only idealistic values and should not
be taken individually as predictors of success. Other clinical signs such as level of
consciousness, sensorium, ability to follow commands, ability to lift head off pil-
low, character and volume of secretions, and hemodynamic status may also help in
predicting a successful postextubation course.
Complications

The patient followed a gradual resolution of her multiorgan dysfunction and severe re-
fractory pulmonary difficulties after an 18-day ventilator course. She was recovered and
discharged to a home health agency where she was advised to abstain from prescription
narcotics, continued on Gentamicin 360 mg IV once per day, and Ciprofloxacin 750 mg
twice daily for 10 days. Her SpO at discharge was 90% on room air while walking.
2

CASE 9: ACUTE RESPIRATORY

DISTRESS SYNDROME

INTRODuCTION

M.I. was a 22-year-old, 54-Kg female with a history of systemic lupus erythemato-
sus, congenital mitral regurgitation, and syncope. For the past several months, she
complained of a mild productive cough while lying down. One week prior to her admis-
sion she developed a severe cough, progressive dyspnea without the use of accessory
muscles, and associated pain throughout her chest wall and into her upper abdomen.

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