The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

SELECTION OF APPROPRIATE VENTILATION PARAMETERS: OUTCOMES ACCORDING TO MODE OF VENTILATION

Kathleen Deakins RRT, Robert L. Chatburn RRT FAARC, and Timothy R. Myers BS RRT. Rainbow Babies & Children's Hospital. Cleveland, OH

INTRODUCTION: Patients often require mechanical ventilation due to impaired gas exchange in various disease states. The goal of mechanical ventilation is to achieve adequate ventilation and oxygenation without causing adverse effects on the cardiovascular system or lung tissue damage. Respiratory Care Practitioners (RCP) play an important role in initiating mechanical ventilation that includes selection of an appropriate mode of ventilation. The purpose of this study was to evaluate the ability of the RCP to select an appropriate mode of ventilation and settings to achieve adequate gas exchange confirmed by blood gas analysis. METHODS: Two hundred two patients admitted to our PICU and NICU were placed on mechanical ventilators during a three-month period (1-8 to 4-8-00). RCPs completed a Mechanical Ventilation Initiation Data Sheet for each patient ventilated. Data collected included age, weight, diagnosis, initial ventilator settings, mode of ventilation and initial blood gas results following ventilation. Enrolled patients that required reintubation were excluded from data recollection. Blood gas values were analyzed separately by pH/PCO2 for ventilation and PO2/ SaO2 for oxygenation. Mode of ventilation was separated into categories of: Pressure Control (PC), Volume Control (VC), Dual Mode (DM), and High Frequency Ventilation (HFV). Ventilation parameters were judged appropriate if the first set of blood gas values were within acceptable ranges. Respiratory alkalosis was defined as pH > 7.45 and PaCO2 < 35 torr for all patients in all modes. Respiratory acidosis was defined as pH < 7.35 and PaCO2 > 45 torr (for PICU patients; pH < 7.25 for NICU patients). Hyperoxic status was defined as PaO2 > 100 torr (NICU patients only). Hypoxic status was defined as PaO2 < 55 torr (NICU patients) and SaO2 < 93% or SvO2 < 70% (PICU patients).

Results:
The Table below categorizes the percentage of patients by acid-base and oxygenation status for each mode of ventilation. Non-percentage numbers are patients that did not have acid-base status or oxygenation status assessed (excluded from percentage calculations). Two patients in Dual mode are not included (1 acidotic and 1 normal acid base, 2 normal oxygenation).

Acid-Base Status HFV VC PC
alkalotic (n=14) 8% 5% 9%
normal (n =151) 61% 81% 82%
acidotic (n=23) 31% 14% 9%
no gas or capillary gas (n = 13) 0 7 5
Oxygenation Status HFV VC PC
hyperoxic (n=27) - - 31%
normal (n =123) 69% 90% 52%
hypoxic (n=24) 31% 10% 17%
no gas or capillary gas 0 7 21

CONCLUSION: Successful initiation of mechanical ventilation was better achieved in conventional modes (VC and PC) for both ventilation and oxygenation. Optimization of blood gas parameters by conventional modes for ventilation was similar, but optimization of blood gas parameters for oxygenation was best achieved in Volume Control.

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