The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

BREATH ANALYSIS OF ADAPTIVE SUPPORT VENTILATION AND PROPORTIONAL ASSIST VENTILATION

S. Richey1, D. Grooms2


Background: Adaptive Support Ventilation (ASV,Hamilton Medical) and Proportional Assist Ventilation (PAV,Tyco Healthcare) are two modalities that assess patient work of breathing and incorporate this data into their algorithms to titrate the compensation pressure and additionally frequency in ASV. The purpose of this study was to explore the differences between the two modalities in a simulated spontaneous breathing model applying various work loads throughout constant minute ventilation.

Methods: The two ventilators under investigation were alternatively connected to a simulated spontaneous breathing model consisting of a dual chamber, Double TTL test lung (Michigan Instruments). One test lung (driving model) was powered by a Galileo Ventilator (Hamilton Medical) to generate spontaneous breathing of a second test lung (spontaneous model). The Volume Control-CMV mode was used for the driving ventilator with the following settings: Vt = 530, Frequency = 14 (minute ventilation= 7.42), I-time = 1.0 seconds, PEEP= +5, Peak flow = 51 lpm delivered with a sinusoidal waveform pattern, which created a peak inspiratory flow at the proximal end of the E.T.T. of 18 lpm on the spontaneous model. Flow measurement was verified utilizing a “Bicore” monitoring device (Bicore Monitoring Systems). ASV settings: Ideal Body Weight= 73kg, Minute Volume %= 100, pramp=25ms, ETS=25%, Trigger= 2 cmH2O, PEEP=0. PAV settings: 80% compensation, PEEP=0, Trigger= 2 cmH2O. Test conditions consisted of: 1. static compliance of 50 ml/cmH20, with added resistance of 6 & 9 cmH2O/L/sec 2. static resistance of 4 cmH2O/L/sec, with compliance changes of 70,50, & 30 ml/cmH20. Breath Analysis consisted of capturing time and pressure data from the proximal end of the E.T.T. by utilizing the Galileo’s Auxiliary pressure port and Data Logger software (Hamilton Medical). The “Area Under the Curve” was calculated for each breath using the “linear trapezoidal rule” & the paired two sample t test was used to evaluate differences between the modalities using spreadsheet software (Excel, Microsoft). A p value less than 0.05 was considered statistically significant.

Results: There were considerable differences with all measured respiratory data when comparing ASV to PAV in every test scenario (table 1).

Conclusion: There are many differences between the two modalities in regards to breath delivery, and compensation pressure. Conversely, both modes ventilated with safe tidal volumes and PIP.

Table 1: A Comparison Between ASV & PAV
Variable ASV PAV
Minute Ventilation (p=0.03)7.44 lpm8.54 lpm
Tidal Volume (p=0.01)491.20 ml610.60 ml
Frequency Total (p=0.03)15 bpm14 bpm
Frequency Spontaneous (p=0.01)3 bpm14 bpm
Inspiratory Time (p=0.01)1.73 seconds1.00 seconds
Area Under the Curve (p=0.01)232.93 cmH2O186.20
cmH2O
Peak Pressure (p=0.01)12.14 cmH2O15.98 cmH2O

All measured values are displayed as "means". Area Under the Curve was used to calculate total pressure compensation.


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