Adult respiratory distress syndrome and new modes of mechanical ventilation: reducing the complications of high volume and high pressure.

Reported survival rates for severe adult respiratory distress syndrome (ARDS) patients vary from 9% to 84%. Animal study results have suggested that application of the high pressures needed to deliver commonly used tidal volumes (10 to 15 mL/kg) may induce an overexpansion of the remaining small fraction of compliant ARDS lung still capable of gas exchange. Conventional ventilatory therapy might thus superimpose an iatrogenic lung injury on the ARDS lung. These considerations have led to pressure-limited mechanical ventilation strategies, including pressure-controlled, inverse-ratio ventilation. Caution should be exercised, however, since there are no convincing data that any particular ventilatory support mode is superior for the support of ARDS patients. Well-controlled, randomized clinical trials are needed. Because of the phenomenon of information input overload, it seems reasonable to question our ability to come to the "right therapeutic decision" when dealing with multivariate problems in severely ill patients. Since ARDS patients provide clinicians with complicated, multifactorially determined problems, the identification of patient outcome changes due to specific interventions (e.g., a new mechanical ventilation mode) is difficult. Computerized protocols eliminate unnecessary variation in clinical care. They standardize clinical care and impose control on the clinical care process. By standardizing therapy, protocols may significantly reduce the random and nonrandom noise (bias) introduced into the clinical environment by clinical care team members. This is especially important fo the many pertinent clinical questions addressed by clinical trials that cannot be double blinded. Conclusions from protocol-controlled clinical trials should be more credible and more likely to lead to action than those of the past.