The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Cardiopulmonary Interactions During a Ventilator Mode change in a Pediatric Patient

Michelle Lilley RRT, Patrice Benjamin RRT, David A. Turner, MD Children's Hospital Boston and Harvard Medical School, Boston, MA

Introduction: Airway pressure release ventilation (APRV) is a mode aimed at recruiting and maintaining lung volume, while preserving spontaneous ventilation1. We report an episode of dramatic cardiopulmonary interaction involving a pediatric patient who was switched from APRV to PCV+PSV.

Case Summary:
A 3 yr old girl with Kaposiform hemangioendothelioma required prolonged mechanical ventilation following an exploratory laporatomy. PCV+PSV parameters were rate 22, PIP/PEEP 30/10 cmH2O, PSV 20 cmH2O, and FIO2 0.85, Paw 19 cmH2O, mandatory VT 5 mL/kg, spontaneous VT 2.0 mL/kg, and ABGs were pH 7.33, PaCO2 71 mmHg, PaO2 85 mmHg. APRV was initiated due to worsening gas exchange, enlarged abdominal girth, increasing ventilator support, and the need to preserve spontaneous ventilation.  Initial APRV settings were PHIGH/PLOW 24/0 cmH2O, THIGH /TLOW 7.0/0.4 sec, FIO2 0.6. Paw was 24 cmH2O, and release VT 8 mL/kg. ABG was pH 7.36, PaCO2 64 mmHg, PaO2 130 mmHg. The patient required continuous veno-venous hemofiltration (CVVH). Due to hemodynamic instability, despite inotropic support, CVVH output was limited leaving the patient in a persistent fluid positive state. On day 4 of APRV parameters were PHIGH/PLOW 28/0 cmH2O, THIGH /TLOW 5.6/0.4 sec, FIO2 0.45. Paw was 27 cmH2O, and release VT 12 mL/kg. ABG was pH 7.20, PaCO2 71 mmHg, PaO2 65 mmHg. A CXR showed an essentially clear left lung with sharp costophrenic angle and an opacified right lung. The patient continued to require inotropic support, CVVH output was suboptimal and fluid status persistently positive. Due to the lack of appreciable uniform alveolar disease by CXR and ongoing hemodymanic instability, a trial of PCV+PSV was attempted. PCV+PSV parameters were rate 22, PIP/PEEP 30/12 cmH2O, PSV 20 cmH2O, and FIO2 0.5, Paw 19 cmH2O, mandatory VT 8 mL/kg, and spontaneous VT 7 mL/kg. ABG was pH 7.23, PaCO2 69 mmHg, PaO2 134 mmHg, and concomitantly the patient's BP improved, inotropic support was decreased, and CVVH output was optimized. The patient's fluid status became increasingly negative.  

Discussion:
While we achieved the goal of preserving spontaneous ventilation in this patient, APRV does not appear to have been the optimal mode. The unilateral nature of the lung disease may have lead to lung overdistention and subsequent detrimental cardiovascular effects. Ongoing assessment of clinical data to determine the appropriateness of the settings and mode is an important part of daily clinical practice. We utilize a CPG to assist with patient selection and the use of this mode. Development of a CPG to help guide the team at the bedside is one way to help optimize patient care. 

1. Habashi N (2004). Ventilator strategies for posttraumatic acute respiratory distress syndrome: airway pressure release ventilation and the role of spontaneous breathing in critically ill patients. Curr Opin Crit Care 10(6):549-57.

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