RESUMEN
BACKGROUND: Non-invasive positive pressure ventilation (NPPV) reduces the incidences of ventilator-associated pneumonia, the duration of ICU stay and the mortality rate compared with conventional respiratory management of the patients with acute respiratory failure (ARF). Recently, helmet NPPV equipment became available. Because of the high tolerability, the helmet seems to be the best NPPV interface when prolonged and continuous assistance is needed. In this study, we analyzed several factors related to failure of helmet NPPV in ARF patients in intensive care unit (ICU), retrospectively. METHODS: Institutional Research Committee of Nagasaki Rosai Hospital approved this study. We studied consecutive patients with ARF who needed ventilator support in ICU from February 2012 to February 2013. We excluded the patients whose trachea had been intubated before admission to ICU and comatose patients. After admission to ICU, all ARF-patients received helmet NPPV and conventional intensive care therapy including sedation with dexmedetomidine and vasoactive agents. General clinical data including blood gas analysis were recorded at admission to ICU and during ICU stay. Patient's tracheas were intubated if they met at least one of the following criteria, as judged after they had received helmet NPPV: lack of improvement in arterial blood pH or PaCO2; changes in mental status, in patients unable to tolerate noninvasive ventilation; a decrease in SaO2 to less than 85% despite the use of a high FIO2. The final decision of endotracheal intubation was made by a staff intensivist. We defined the failure of helmet NPPV as the execution of endotracheal intubation. The data were presented as median (IQR), and statistical analysis was performed using Mann-Whitney U-test and Fisher's exact probability test at the P<0.05 level of significance. RESULTS: The subjects were 36 patients (25 males and 11 females) aged 27 to 94 years, including 6 patients with acute heart failure (AHF), 8 with pneumonia, 6 with aspiration pneumonia, 2 with hemothorax, 10 with acute respiratory distress syndrome (ARDS), 1 with asthma, and 3 with acute exacerbation of chronic obstructive pulmonary disease (COPD). NPPV was successful in 29 (19 males and 10 females), but unsuccessful in 7 patients (6 males and 1 female). There were no significant differences in demographic data and the variables before induction of NPPV between the successful and unsuccessful groups. The P/F ratio was improved from 133 (99,167) to 209 (143,274) in the successful group, and from 93 (81,157) to 188 (129,271) in the unsuccessful group after the induction of NPPV, but there was no significant difference between the two groups. In the patients with unsuccessful NPPV, expiratory positive airway pressure, inspiratory positive airway pressure, respiratory rate, body temperature and FIO2 before removing NPPV were significantly higher, and ICU stay was longer compared with the patients with successful NPPV. Furthermore, marked excretion of sputum was observed in 4 of the 7 patients with unsuccessful NPPV. CONCLUSIONS: Helmet NPPV improved oxygenation in ARF patients immediately after induction of NPPV. Although there were no significant predictable parameters of unsuccessful NPPV before induction of NPPV, a lot of excretion of sputum might be suggested as a risk factor.
