The Science Journal of the American Association for Respiratory Care

2002 OPEN FORUM Abstracts

A COMPARISON OF CONTINUOUS MANDATORY VENTILATION WITH AND WITHOUT LEAK COMPENSATION AND AUTOFLOW (CMV-AF), AND PRESSURE CONTROL VENTILATION DURING AN AIR LEAK SYNDROME (ALS) IN A LUNG MODEL.

David L Vines, MHS,RRT, Anita Alvarez, CRT, Salvador A Davo, CRT and Jay I Peters, MD. Respiratory Care, The University of Texas Health Science Center, San Antonio, Texas.

Background: The purpose of this study is to determine if differences exist in tidal volumes (VT) and peak inspiratory pressure (PIP) at the airway and between the lungs when using continuous mandatory ventilation (CMV), CMV with leak compensation (CMV-LC), CMV with AutoFlow (CMV-AF), and pressure control ventilation (PCV) in 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 VT, expired VT, and PIP were 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). CMV, CMV-LC, CMV-AF, and PCV were set to deliver a VT of 400, 600 and 800 mL at a rate of 15 bpm on the Evita 4 ventilator (Dräger Medical, Inc., Telford, PA.). All variables were 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 0.50 and 0.20 L/cmH2O with an airway resistance of 2.7 cmH2O/L/sec, and a compliance of 0.50 L/cmH2O with an airway resistance of 17.6 cmH2O/L/sec.

Results: The following results are means (SD) for data collected under all conditions. There were no significant differences between CMV, CMV-LC, CMV-AF, and PCV without a leak. Inspired VT was significantly higher during CMV-LC (764 ± 197mL) and CMV-AF (764 ± 210mL) with a leak compared to CMV (548 ± 149mL), CMV-LC (558 ± 151mL, CMV-AF (555 ± 159mL), and PCV (568 ± 157mL) without a leak, and CMV (552 ± 148mL) with a leak. Expired VT was significantly higher during CMV without a leak (547 ± 150mL) and CMV-LC (509 ± 147mL, 557 ± 152mL), CMV-AF (502 ± 148mL, 567 ± 160mL), and PCV (470 ± 131mL, 574 ± 161mL) with and without a leak compared to CMV with a leak (352 ± 118mL). Right lung inspired VT was significantly higher during CMV without a leak (240 ± 78mL) and CMV-LC (271 ± 85mL, 249 ± 77mL), CMV-AF (269 ± 84mL, 254 ± 81mL), and PCV (240 ± 80mL, 255 ± 84mL) with and without a leak compared to CMV with a leak (172 ± 74mL). Right lung expired VT was significantly higher during CMV without a leak (235 ± 73mL) and CMV-LC (262 ± 81mL, 242 ± 73mL), CMV-AF (253 ± 81mL, 240 ± 76mL), and PCV (234 ± 74mL, 248 ± 78mL) with and without a leak compared to CMV with a leak (173 ± 63mL). Left lung inspired VT was significantly higher during CMV-LC (489 ± 127mL), CMV-AF (503 ± 142mL), and PCV (440 ± 141mL) with a leak compared to CMV (359 ± 91mL) with a leak, and CMV (286 ± 79mL), CMV-LC (289 ± 80mL), CMV-AF (293 ± 84mL), and PCV (299 ± 84mL) without a leak. Left lung expired VT was significantly higher during CMV (281 ± 75mL), CMV-LC (284 ± 76mL), CMV-AF (286 ± 79mL), PCV (293 ± 80mL) without a leak compared to CMV (162 ± 61mL), CMV-LC (220 ± 62mL), CMV-AF (219 ± 62mL), and PCV (208 ± 55mL) with a leak. Left lung expired VT was significantly higher during CMV-LC (220 ± 62mL) and CMV-AF (219 ± 62mL) with a leak compared to CMV (162 ± 61mL) with a leak. There were no significant differences between PIP at the airway or between the lungs with or without an air leak.

Conclusions: When a leak was present, CMV with leak compensation or AutoFlow increased inspired VT to maintain a significantly higher expired VT in both lungs compared to CMV without leak compensation or AutoFlow. In the presence of an air leak, PCV increased inspiratory flow to maintain the set inspiratory pressure, which resulted in a significantly higher inspired VT in both lungs and a significantly higher expired VT in the right lung compared to CMV without leak compensation or AutoFlow. These findings suggest that CMV with leak compensation, CMV with AutoFlow or PCV may maintain better gas exchange compared to CMV without leak compensation or AutoFlow.

OF-02-150

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