OBJECTIVE: During proportional assist ventilation (PAV) the timing and frequency of inflations are controlled by the patient and the patient's work of breathing may be relieved by elastic and/or resistive unloading. It is important and the authors' objective to determine whether ventilators delivering PAV function well in situations mimicking neonatal respiratory conditions. DESIGN: In vitro laboratory study. SETTING: Tertiary neonatal ICU. INTERVENTIONS: Dynamic lung models were developed which mimicked respiratory distress syndrome, bronchopulmonary dysplasia and meconium aspiration syndrome to assess the performance of the Stephanie neonatal ventilator. MAIN OUTCOME MEASURES: The effects of elastic and resistive unloading on inflation pressures and airway pressure wave forms and whether increasing unloading was matched by an 'inspiratory' load reduction. RESULTS: During unloading, delivered pressures were between 1 and 4 cm H(2)O above those expected. Oscillations appeared in the airway pressure wave form when the elastic unloading was greater than 0.5 cm H(2)O/ml with a low resistance model and 1.5 cm H(2)O/ml with a high resistance model and when the resistive unloading was greater than 100 cm H(2)O/l/s. There was a time lag in the delivery of airway pressure of at least 60 ms, but increasing unloading was matched by an inspiratory load reduction. CONCLUSIONS: During PAV, unloading does reduce inspiratory load, but there are wave form abnormalities and a time lag in delivery of the inflation pressure. The impact of these problems needs careful evaluation in the clinical setting.
OBJECTIVE: During proportional assist ventilation (PAV) the timing and frequency of inflations are controlled by the patient and the patient's work of breathing may be relieved by elastic and/or resistive unloading. It is important and the authors' objective to determine whether ventilators delivering PAV function well in situations mimicking neonatal respiratory conditions. DESIGN: In vitro laboratory study. SETTING: Tertiary neonatal ICU. INTERVENTIONS: Dynamic lung models were developed which mimicked respiratory distress syndrome, bronchopulmonary dysplasia and meconium aspiration syndrome to assess the performance of the Stephanie neonatal ventilator. MAIN OUTCOME MEASURES: The effects of elastic and resistive unloading on inflation pressures and airway pressure wave forms and whether increasing unloading was matched by an 'inspiratory' load reduction. RESULTS: During unloading, delivered pressures were between 1 and 4 cm H(2)O above those expected. Oscillations appeared in the airway pressure wave form when the elastic unloading was greater than 0.5 cm H(2)O/ml with a low resistance model and 1.5 cm H(2)O/ml with a high resistance model and when the resistive unloading was greater than 100 cm H(2)O/l/s. There was a time lag in the delivery of airway pressure of at least 60 ms, but increasing unloading was matched by an inspiratory load reduction. CONCLUSIONS: During PAV, unloading does reduce inspiratory load, but there are wave form abnormalities and a time lag in delivery of the inflation pressure. The impact of these problems needs careful evaluation in the clinical setting.
Authors: Olie Chowdhury; Prashanth Bhat; Gerrard F Rafferty; Simon Hannam; Anthony D Milner; Anne Greenough Journal: Eur J Pediatr Date: 2016-01-08 Impact factor: 3.183
Authors: Sandeep Shetty; Prashanth Bhat; Ann Hickey; Janet L Peacock; Anthony D Milner; Anne Greenough Journal: Eur J Pediatr Date: 2015-07-31 Impact factor: 3.183