Noninvasive positive pressure ventilation (NPPV) in critically ill patients: preliminary experience

Study objective

To validate the efficacy of NPPV in patients with hypercapnic or hypoxemic acute respiratory failure (ARF) admitted to a Medical Intensive Care Unit.

Materials and methods

Thirty-two patients (23M, 9F, mean age 66, range 25–91) received NPPV if they met the following criteria: severe dyspnea at rest, respiratory muscle fatigue, normal mentation, normal upper airways, stable hemodynamic status and, as for hypercapnic ARF. pH <7.35, PaCO₂ >45 mmHg, respiratory rate (RR) >25 bpm and, as for hypoxemic ARF, PaO₂/FiO₂ <200, RR >30 bpm. Eighteen patients (12M, 6F, mean age 68,4, range 50–91) had hypercapnic ARF due to chronic obstructive lung disease (COLD); 7 (6M, 1F, mean age 75, range 73–84) had cardiogenic hypercapnic acute pulmonary edema (cAPE); 7 (5M, 2F, mean age 50, range 25–72) had severe pneumonia (SP), 2 with hypercanic ARF. End-points were the following: pH >7.35, RR <24 bpm, V_T >7 ml/kg, reduced dyspnea, diminished signs of muscle fatigue, SpO₂ >90%. NPPV was considered successful if the patient was not intubated and mechanically ventilated. NPPV was considered unsuccessful if the patient was intubated and mechanically ventilated, became intolerant of mask or died. BiPAP Respironics^® ventilators (S/T-D 20, S/T-D 30, Vision), were used to administer NPPV, as pressure support ventilation, by nasal or facial masks. All patients were given standard medical therapy, as required by the underlying disease.

Results

NPPV was successful in 14 of 18 COPD patients (77.7%), in all 7 patients with cAPE (100%) and in 3 of 7 patients with SP (42.8%). Failure in 4 COLD patients was due to mask intolerance in three cases and to sudden death in one case. Four patients with SP (three seriously imnuinocompromised) died. COLD patients were ventilated for 3 to 62 h (mean 21.5 h), cAPE patients for 4 to 15 h (mean 7.4 h) and SP patients for 12 to 148 h (mean 59.7 h). Ventilation was longer in SP patients who obtained a therapeutic benefit (mean 112 h) than in SP patients who did not (mean 23 h).

Conclusion

With the limits of this observational study, we conclude that NPPV has been shown to be an effective support therapy for COLD patients with acute exacerbation and for hypercapnic severe cAPE patients. The use of NPPV in patients with SP was less effective and warrants ulterior study to be validated, dated, according to literature.