The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts


Theresa Ryan Schultz BA. RRT, P/P Spec., Linda Allen NapoM, BS, RRT, RPFT, P/P Spec., Lorralne F. Hough, MEd, RRT, P/P Spec., Maureem O'Rourke, MD, Andrew Costarno, MD, Rodolfo I. Godinez, MD, PhD, The Children's Hospital of Philadelphia, Philadelphia, PA

PATIENT DATA AND CASE SUMMARY: This is an almost 3 year old previously well boy with group B strep sepsis, and venous thrombosis. He underwent fasciotomy of his right lower extremity secondary to compartment syndrome. Post-operative complications included acute renal failure, ARDS, and subcutaneous emphysema. Immediately post-operatively the patient was hemodynamically unstable with poor perfusion. Medications delivered included dopamine, sodium nitroprusside and heparin. Oxygenation and ventilation were maintained with an exhaled minute ventilation of 423 ml/kg/min, peak inflating pressures were 30 cm H_2O, FiO_2.7, and PEEP 8 cm H_2O. A-a DO_2 was equal to 240 mm Hg. Twenty-four hours post-op, ventilation and oxygenation demands were increased with PEEP equal to + 12 cm H_2O and peak inflating pressures equal to 52 cm H_2O on the same pre-set tidal volume. A-a DO_2 was equal to 325 mm Hg. Chest x-ray 48 hours post op revealed diffuse atelectasis. Pneumomediastinum, subcutaneous emphysema and a small left pleural effusion were noted on the patient's x-ray seventy-two hours after surgery. Permissive hypercarbia with PaO_2 greater than or equal to 40 mm Hg became acceptable. In order to achieve this goal the patient was paralyzed and placed on PEEP +15 cm H_2O. Three days post-op, in the face of persistent acidosis, with an A-a DO_2 equal to 411 mm Hg. peak inflating pressures nearing 70 cm H_2O with a chest x-ray that revealed an extension of the pneumomediastinum, subcutaneous emphysema and bilateral pleural effusions, the patient was placed on Pressure Regulated Volume Control (PRVC) via the Siemens Servo 300. The following chart summarizes changes in ventilation parameters:

Day of Ventilation Time ModePreset V_TPeak Inflating PressurePEEP

Day 13:00 AMSIMV 360 ml 30 cm H208

Day 25:00 AMSIMV 360 ml 52 cm H20 12

Day 38:00 PMSIMV 300 ml 62 cm H20 11

Day 4 11:00 AMSIMV 300 ml 63 cm H20 15

Day 41:00 PMSIMV 250 ml 59 cm H20 15

Day 42:00 PMSIMV 220 ml 62 cm H20 15

Day 45:00 PMPRVC 220 ml 47 cm H20 12

Day 49:40 PMPRVC 220 ml 40 cm H20 12

Day 12 5:00 PM VS(180 ml)37 cm H208

Day 13 7:00 AM VS(170 ml)25 cm H208

After being on PRVC for three hours, the patient's peak inflating pressures were 47 cm H_2O and the PEEP was weaned to + 12 cm H_2O. Medication and fluid management were unchanged. Seven hours after PRVC the peak inflating pressures were 40 cm H_2O and the PEEP was weaned to 12 cm H_2O with an improvement in A-a DO_2 and acidosis. Less than two days later, the patient's A-a DO_2 was 246 mm Hg. Chest x-ray at that time revealed decreased mediastinal air, atelectasis, subcutaneous air, and overall improved aeration. On day eleven of mechanical ventilation; day 8 of PRVC, peak inflating pressures were 30 cm H_2O and the PEEP had successfully been weaned to 8 cm H_2O, A-a DO_2 was equal to 159 mm Hg. Paralysis was discontinued and the patient was placed in the Volume Support mode on day 9 of PRVC. Ventilation was achieved with pressures equal to 37 cm H_2O. Eight hours after the patient was on Volume Support, the pressure necessary to maintain essentially the same minute ventilation was 25 cm H_2O. The patient appeared comfortable while breathing spontaneously and had diuresed well overnight, hence lung compliance improved. This patient ultimately weaned off the ventilator a few days later with no subsequent oxygen requirement.

SIGNIFICANCE OF THE CASE: Pressure Regulated Volume Control appeared to be valuable in the treatment of this patient. The availability of this mode of ventilation enabled the healthcare team to ventilate this patient with lower peak inflating pressures.