The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

A COMPARISON OF ASSIST CONTROL VOLUME VENTILATION, PRESSURE CONTROL VENTILATION, AND ADAPTIVE PRESSURE VENTILATION DURING AN AIR LEAK SYNDROME (ALS) IN A LUNG MODEL.


David Chapa, BS, CRT, David L Vines, MHS, RRT, and Jay I Peters, MD. Respiratory Care, The University of Texas Health Science Center, San Antonio, Texas.


Background:
The primary purpose of this study is to determine if differences exist in tidal volume (VT), peak inspiratory pressure (PIP), and mean airway pressure (MAP) at the airway and between the lungs when using assist control volume ventilation (ACV), pressure control ventilation (PCV), and adaptive pressure ventilation (APV) in air leak syndrome (ALS).

Method: The ALS was created in a two-compartment mechanical lung model (Michigan Instruments Inc., Grand Rapids, MI) by inserting a 3.0 mm catheter in the left lung. Inspired and expired VT and PIP will be measured at the beginning of the airway using a Ventrak 1550 (Novametrix Medical Systems, Inc., Wallington, CT) and before both lungs using a CO2SMO Plus (Novametrix Medical Systems, Inc., Wallington, CT). ACV, PCV, and APV will be set to deliver a VT of 400, 600 and 800 mL at a rate of 15 bpm on the Galileo (Hamilton Medical, Reno, NV). All variables will be collected for all modes on an inspiratory to expiratory ratio of 1:2, 1:1, and 2:1 with and without a leak in the following lung conditions: compliance of 1.0 L/cm H2O, 0.40 L/cm H2O, and 0.20 L/cm H2O while airway resistance was 2.7 cm H2O/L/sec, and a compliance of 1.0 L/cm H2O while airway resistance was 17.6 cm H2O/L/sec.

RESULTS:
The following results are the mean values of the data collected under all conditions. There were no significant differences between ACV, PCV, and APV without an air leak. Inspired VT was significantly higher during PCV (724 + 191 mL) and APV ( 707 + 175 mL) with an air leak compared to ACV (573 + 149 mL), PCV (571 + 151 mL), and APV (552 + 143 mL) without a leak and ACV (575 + 152 mL) with a leak. Expired VT was significantly higher during ACV without a leak (564 + 147 mL), PCV (576 + 156 mL, 421 + 135 mL) and APV (411 + 134 mL, 558 + 142 mL) with and without a leak, compared to ACV with a leak (323 + 123 mL). The MAP was significantly greater in PCV (7 + 4 cm H2O, 8 + 5 cm H2O) and APV (6 + 3 cm H2O, 7 + 5 cm H2O) with and without a leak, compared to ACV with a leak (4 + 2 cm H2O). In the right lung, inspired VT were significantly higher in ACV without a leak (250 + 78 mL), PCV (241 + 73 mL, 260 + 75 mL) and APV (248 + 95 mL, 251 + 71 mL) with and without a leak compared to ACV with a leak (171 + 74 mL). Right lung expired VT were significantly higher in ACV without a leak (248 + 72 mL), PCV (229 + 71 mL, 252 + 71 mL) and APV (225 + 69 mL, 243 + 67 mL) with and without a leak compared to ACV with a leak (174 + 62 mL). MAP in the right lung was significantly higher in PCV (8 + 5 cm H2O) and APV (8 + 5 cm H2O) without a leak compared to ACV (4 + 2 cm H2O) with a leak. Left lung inspired VT were significantly higher in PCV with a leak (502 + 144mL) and APV with a leak (489 + 130 mL) compared to ACV (383 + 96 mL, 282 + 77 mL) with and without a leak, and PCV (293 + 79 mL) and APV (283 + 72 mL) without a leak. Left lung expired VT were significantly higher in ACV (281 + 71 mL), PCV (289 + 77 mL), and APV (279 + 69 mL) without a leak, compared to ACV (144 + 55 mL), PCV (185 + 59 mL), and APV (181 + 59 mL) with a leak. Left lung expired VT were significantly higher in PCV (185 + 59mL) and APV (181 + 59mL) with a leak compared to ACV (144 + 55 mL) with a leak. MAP in the left lung was significantly higher in ACV (6 + 3 cm H2O) without a leak, PCV (7 + 4 cm H2O, 8 + 5 cm H2O), and APV (6 + 3 cm H2O, 8 + 5 cm H2O) with and without a leak, compared to ACV (4 + 2 cm H2O) with a leak. There were no significant differences in PIP between the different modes at the airway or between either lung with and without a leak. 

CONCLUSION:
When a leak was present, PCV and APV increased inspired tidal volume to maintain a significantly higher expired tidal volume in both lungs, along with significantly higher mean airway pressures at the airway and in the left lung, compared to ACV. These findings suggest that in the presence of an air leak PCV and APV may maintain better ventilation and oxygenation compared to ACV.

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