In the report of Avery et al, only 18 of 67 patients with an elevated PaC02 were intubated (for these 67 patients, mean PaC02 was 69 and mean pH was 7.13); 26 of the 67 died. In our study, 63 patients had an elevated PaC02 (mean PaC02, 70; mean pH, 7.14). All were intubated and only 13 died. If we exclude patients with cardiogenic shock and cardiopulmonary arrest, as did Avery et al, only four of 47 patients in our study died compared with 26 of 67 in the study of Avery et al. These findings suggest that mechanical ventilation is an important therapy that improves survival in acute cardiogenic pulmonary edema. In our study, mortality was not associated with respiratory failure, which was successfully treated by mechanical ventilation, but rather by irreversible cardiac dysfunction.
We did not find that mechanical ventilation excessively prolonged life before an inevitable death occurred. Nonsurvivors and survivors had similar lengths of stay, and with one exception spent similar time receiving mechanical ventilation. Moreover, causes of death were cardiac in origin, suggesting patients were not being kept alive by mechanical ventilation to die of complications associated with a prolonged hospitalization. In conclusion, two groups of patients emerge from examination of our data. The first group includes patients with hypotension, many of whom had myocardial infarction.