Since the frequency that our flight crews encounter a critically ill hypoxemic patient that cannot be supported safely with our transport ventilator is approximately 1% of all transfers (approximately two patients per year), there is no justification for our health system to also invest in the additional equipment and staffing to support a mobile intensive care ground transport unit (at an additional estimated cost of $300,000 to $400,000 dollars per year). The benefit that this additional resource would provide us, as Drs. Lieshout and Vroom point out, is that it would enable our transport team to prescribe for the patient the same level of ventilatory support that they were receiving while at the ICU of the transferring hospital; however, as mentioned, we estimate that this would be necessary for only approximately two patients per year. In contrast, at a fractional cost of approximately $300/yr, for prostacyclin and disposable equipment (no additional staffing required), we can potentially improve oxygenation during transport for these few patients, even above the levels achieved at the referring hospital, despite the use of a less sophisticated ventilator. We realize, based on data from ICU patients treated with prostacyclin, that the magnitude of response in oxygenation seen in our patient will not be realized in all patients; however, given the simplicity of a prostacyclin trial, the rapidity of the response and the opportunity cost, we believe it is the most appropriate intervention to employ in this circumstance.