The effects of altering tidal volume (V(T)) on oxygen dynamics were monitored in eight injured patients and eight cirrhotic patients. The injured patients had sustained an average of 52 minutes of shock, received 20 transfusions in the operating room, and had a pulmonary shunt (Q̇(s)/Q̇(t)) of 16 per cent at the time of study. Seven of the cirrhotic patients developed adult respiratory distress syndrome (ARDS) following a massive gastrointestinal bleeding episode and one following a portacaval shunt procedure; the cirrhotic group had a Q̇(s)/Q̇(t) of 21 per cent at the time of study. All patients were on the assist/control mode of a volume ventilator without positive end-expiratory pressure (PEEP) and tidal volume (V(T)) of 7 ml, 11 ml, and 14 ml/kg body weight were used in each patient in a random manner while oxygen dynamics were monitored. High V(T) caused a rise in minute volume, as one would predict, and a fall in respiratory rate in both groups. High V(T) did not change the PaO2 in the injured group but produced a significant increase in the PaO2 of the cirrhotic group. There was a significant decrease in Q̇(s)/Q̇(t) in the cirrhotic group and a slight fall in shunt in the injured patients. Accompanying these changes was the significant decline in the cardiac indices (CI) and O2 delivery (O2Del) in both groups of patients as the V(T) was raised. Oxygen consumption (V̇O2) changes were variable and not significant. The increased minute volume (MV) caused a significant decrease in the PaCO2 and a significant increase in pH in both groups of patients. These data show that ongoing monitoring of blood gases provides insufficient data to regulate V(T) for optimal oxygen delivery in patients with ARDS. The use of high (>12 ml/kg) V(T) is potentially dangerous and requires concomitant monitoring of CI, O2 Del and V̇O2 in these patients.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Jan 1 1983|
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