Page 699 - Clinical Application of Mechanical Ventilation

Case Studies 665

symptoms that are predominantly idiopathic in nature, treatment included plasma-
phoresis in an attempt to reverse the pathology. However, by the sixth ventilator day
it was apparent that long-term management strategies would be necessary. As such,
a pediatric feeding tube was inserted and a tracheotomy was performed in an effort
Tracheotomy is to facilitate removal of secretions and to make oral care more accessible. A metabolic
performed when long-term
mechanical ventilation is study was performed to ascertain the patient’s nutritional status, and feedings were
anticipated.
adjusted in terms of optimizing the resulting V/Q ratio and total caloric intake. He
was placed in a Rotorest® bed and continuously turned from side to side and kept
comfortable with anti-anxiolytics. The patient was closely monitored for signs of hy-
percapnea, hypoxia, and respiratory distress. It is important to note that the patient
was not able to initiate any significant spontaneous tidal volume. The ventilator was
thus completely responsible for his total alveolar ventilation. Blood gas analysis after
the tracheostomy by general anesthesia revealed the following:

pH 7.40
PaCO 2 52 mm Hg
PaO 2 122 mm Hg
SaO 2 96%
-
HCO 31 mEq/L
3
Mode A/C
f 14/min
V T 500 mL
F O 2 40%
I
PEEP 10 cm H O
2
In order to improve alveolar ventilation, the frequency was increased to 16/min and
the tidal volume was increased to 670 mL (approx. 13 mL/Kg) because he was still un-
able to initiate spontaneous ventilation but appeared “air-hungry” (dyspnic). Due to
his unstable ventilatory status, blood gas results from the following morning revealed:
pH 7.39
PaCO 2 48 mm Hg
PaO 2 90 mm Hg
SaO 2 94%
-
HCO 28 mEq/L
3
Mode A/C
f 16/min
V T 670 mL
F O 2 40%
I
PEEP 10 cm H O
2
In order to minimize airway pressures and reduce the risk of barotrauma, the
patient’s PaCO was maintained in the mid to upper 40s (permissive hypercapnea).
2
This is an appropriate ventilation strategy as long as the physician and health care
team members “buy-in” to the stated goals for mechanical ventilation for a given
pathology. The patient appeared to rest comfortably. Blood gases obtained on the
18th ventilator day revealed:

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