Ventilatory pattern in respiratory failure arising from acute myocardial infarction. II. PtcO2 and PtcCO2 compared to Pao2 and PaCO2 during IMV4 vs IPPV12 and PEEP0 vs PEEP10.

Transcutaneous oxygen and carbon dioxide tensions (PtcO2 and PtcCO2) were compared with PaO2 and PaCO2 values in 9 patients with pulmonary edema due to acute myocardial infarction (AMI) measured during four experimental interventions: (a) intermittent mandatory ventilation (IMV) 4/min + PEEP0 (cm H2O); (b) intermittent positive pressure ventilation (IPPV)12 + PEEP0; (c) IMV4 + PEEP10; and (d) IPPV12 + PEEP10. PtcO2 responded rapidly to the institution of PEEP, the rise correlating well with that in PaO2 both on IMV4 (r = 0.78) and IPPV12 (r = 0.87). On the other hand, correlations between PtcO2 vs CI and PvO2 were poor (r being 0.45 and 0.24, respectively). Transcutaneous oxygen electrode is, thus, useful in monitoring patients with post-AMI pulmonary edema, as it rapidly reflects the effects of ventilatory therapy. A nonheated PtcCO2 sensor was used in 6 patients and a heated electrode in 3 patients. With the nonheated electrode, the correlation between PaCO2 and PtcCo2 was good (r = 0.86) in 5 patients, while r in the 3 patients with the heated electrode was 0.73. One patient having a cardiac index of 1.6 L/min . M2 showed a dissociation in PCO2 values. While PaCO2 remained unchanged, PtcCO2 rose to 73 torr and within some minutes the patient had asystole. PtcCO2 tension generally shows good correlation with PaCO2 and, thus, reflects ventilation. It may also prove to be useful in the early detection of critical low cardiac output states.