Accuracy of pulse pressure variations for fluid responsiveness prediction in mechanically ventilated patients with biphasic positive airway pressure mode.

The accuracy of pulse pressure variation (PPV) to predict fluid responsiveness using pressure-controlled (PC) instead of volume-controlled modes is under debate. To specifically address this issue, we designed a study to evaluate the accuracy of PPV to predict fluid responsiveness in severe septic patients who were mechanically ventilated with biphasic positive airway pressure (BIPAP) PC-ventilation mode. 45 patients with sepsis or septic shock and who were mechanically ventilated with BIPAP mode and a target tidal volume of 7-8 ml/kg were included. PPV was automatically assessed at baseline and after a standard fluid challenge (Ringer's lactate 500 ml). A 15% increase in stroke volume (SV) defined fluid responsiveness. The predictive value of PPV was evaluated through a receiver operating characteristic (ROC) curve analysis and "gray zone" statistical approach. 20 (44%) patients were considered fluid responders. We identified a significant relationship between PPV decrease after volume expansion and SV increase (spearman ρ = - 0.5, p < 0.001). The area under ROC curve for PPV was 0.71 (95%CI 0.56-0.87, p = 0.007). The best cut-off (based on Youden's index) was 8%, with a sensitivity of 80% and specificity of 60%. Using a gray zone approach, we identified that PPV values comprised between 5 and 15% do not allow a reliable fluid responsiveness prediction. In critically ill septic patients ventilated under BIPAP mode, PPV appears to be an accurate method for fluid responsiveness prediction. However, PPV values comprised between 5 and 15% constitute a gray zone that does not allow a reliable fluid responsiveness prediction.

Validation of a Score for the Detection of Subjects with High Risk for Severe High-Altitude Illness.

PURPOSE: A decision tree based on a clinicophysiological score (severe high-altitude illness (SHAI) score) has been developed to detect subjects susceptible to SHAI. We aimed to validate this decision tree, to rationalize the prescription of acetazolamide (ACZ), and to specify the rule for a progressive acclimatization. METHODS: Data were obtained from 641 subjects in 15 European medical centers before and during a sojourn at high altitude. Depending on the value of the SHAI score, advice was given and ACZ was eventually prescribed. The outcome was the occurrence of SHAI at high altitude as a function of the SHAI score, ACZ prescription, and use and fulfillment of the acclimatization rule. RESULTS: The occurrence of SHAI was 22.6%, similar to what was observed 18 yr before (23.7%), whereas life-threatening forms of SHAI (high-altitude pulmonary and cerebral edema) were less frequent (2.6%-0.8%, P = 0.007). The negative predictive value of the decision tree based was 81%, suggesting that the procedure is efficient to detect subjects who will not suffer from SHAI, therefore limiting the use of ACZ. The maximal daily altitude gain that limits the occurrence of SHAI was established at 400 m. The occurrence of SHAI was reduced from 27% to 12% when the recommendations for ACZ use and 400-m daily altitude gain were respected (P < 0.001). CONCLUSIONS: This multicenter study confirmed the interest of the SHAI score in predicting the individual risk for SHAI. The conditions for an optimized acclimatization (400-m rule) were also specified, and we proposed a rational decision tree for the prescription of ACZ, adapted to each individual tolerance to hypoxia.