2006 OPEN FORUM Abstracts
MANAGEMENT OF THE MORBIDLY OBESE RESPIRATORY FAILURE PATIENT WITH Bi-VENTT ON THE SERVOi
Paul Luehrs RRT, BSRT, BSEd, John Wolfe MD CoxHealth,
Springfield MO
Introduction: Obesity is an independent risk factor for
intensive care unit death and should be regarded as a severe comorbidity in
such units.(1) Lung protective
ventilation strategies should be implemented in this patient population. The use of Bi-Vent (APRVT), for the management
of morbidly obese respiratory failure patients whose failure is not the result
of ALI/ARDS, has not been widely reported.
The Bi-Vent mode is available on the Servoi. The mode is
most commonly associated with those patients suffering from ALI/ARDS who
require lung recruitment and alveolar stabilization provided by an increased
mean airway pressure (MAP). Bi-Vent
allows the clinician to inverse the I:E ratio while preserving the patient's
ability to spontaneously breathe throughout the ventilatory cycle, improving
patient-ventilator synchrony and promoting lung recruitment.
Case
Summary: On 3/09/06 a 46-year-old male patient
weighing 500 lbs. presented to the ED orally intubated with an 8.0 ET receiving
bag ventilation with FiO2 1.0.
On admission the patient's WBC count was 15.5, the sputum was positive
for staphylococcus aureus, liver enzymes were elevated, echocardiogram showed a
normal LVEF, cardiomegaly and severe pulmonary hypertension. With cardiomegally, pulmonary hypertension
and a normal LVEF an elevated BNP (b-type natriuretic peptide) of 547, is
compatible with right heart failure. The
initial chest x-ray showed gross obesity and bilateral 'white out' with
evidence of cardiomegally. The patient was placed on the Servoi ventilator at 1410 on PC 20
cmH2O, PEEP 15 cmH2O, f
15, FiO2 1.0. The first ABG
at 1425 revealed pH 7.06, PaCO2 106, PaO2 72, O2Hb
85%, COHb 5.1, P/F 72 on a MVe 5.2 l/m.
Over the next 104 minutes the patient was placed in Bi-Vent mode 3 times
resulting in dramatic hypotension. At
1745 the patient was successfully changed to Bi-Vent, without dramatic
hypotension, on PHigh of 35 cmH2O, THigh 3.4
s, TPEEP 0.4 s, f 16, with a PEEPtot. measured at
23 cmH2O, MAP 34 cmH2O.
At 1817 the ABG showed an improving respiratory acidosis and a P/F ratio
of 73. On 3/10/06 at 0540 the patient's
ABG showed a pH 7.47, PaCO2 45, PaO2 265 and P/F 279 on
Bi-Vent: PHigh 33 cmH2O, THigh 4.1 s, TPEEP 0.3 s, PEEP 0, f 14, MVe 7.8 l/m.
Over the following 10 days the patient was maintained in Bi-Vent mode in
order to maintain alveolar patency with high MAPs in the context of a large
abdominal compartment. On day 11 the
patient was changed to PS 10 cmH2O, PEEP 20 cmH2O and
eventually transitioned over to unassisted ventilation with flow-by to the
tracheostomy on day 33. On day 40 the
patient was discharged to home with 2 l/m oxygen.
Discussion: This patient suffered from acute
decompensation of CHF and fluid overload as evidenced by the ED admission BNP
of 547. As a consequence of his BMI his
respiratory and ventilatory status declined.
The patient was placed on a bariatric bed enabling the caregivers to
inflate portions of the bed for skin maintenance. The extremely obese abdomen
put pressure on the chest while in the recumbent or semi-recumbent position
common to the intubated ICU patient.
This abdominal pressure increases the likelihood that the lower lungs
may develop atelectasis. Sedation and
analgesics also increase the opportunity for alveolar collapse under the weight
of the abdominal compartment. We chose
the mode Bi-Vent so the MAP could be increased while maintaining control of the
Plp or PIP, which has been associated with less ventilator associated lung
injury (VALI). Extending the inspiratory
time and limiting the expiratory time, to less than 0.5 s, maintains the
patient in the inspiratory phase for the majority of their ventilatory
cycle. This leads to a sustained
inflation and a higher MAP to combat the intruding abdomen. The use of Bi-Vent in the morbidly obese
patient should be studied as a means of reducing morbidity and mortality.
1. Bercault,
Nicolas Md et al. Obesity-related excess mortality rate in an adult intensive care unit: A risk
adjusted matched cohort study *.Critical
Care Medicine. 32(4):998-1003, April 2004.