Efficacy of Helmet as Interface for Noninvasive Ventilation (NIV) in Acute Hypercapnic Respiratory Failure (AHRF)

Abstract

PURPOSE: The helmet is widely employed to deliver NIV in hypoxic respiratory failure; its use in AHRF is not yet well established. METHODS: 31 COPD patients admitted to a Respiratory Intensive Care Unit (RICU) for AHRF and supported with NIV were randomly assigned to receive as interface the FULL FACE MASK (group A, n.16; pH 7.26±0.08 PaCO2 75.1±11.8 PaO2/FiO2 95.9±55.6) or the HELMET (group B, n. 15; pH 7.25±0.07 PaCO2 81.9±15.2 PaO2/FiO2100.3±50.3). A new helmet designed to specifically improve the performance in COPD patients was used. The ventilator settings were decided according to the usual practice (maximal tolerated inspiratory pressure and PEEP 4 cmH2O) in group A (facial mask) and increasing pressure support and PEEP according to published data [Crit Care Med 2009; 37: 1921‐8] in group B (helmet). Arterial blood gases (ABGs) were evaluated after 1 and 6 hours of NIV. Vital parameters, discomfort scale, dyspnea score and adverse events were recorded too. RESULTS: Baseline ABGs were not statistically different in the two groups. 4 patients (2 in each group required intubation owing to NIV failure). NIV acutely improved alveolar ventilation vs baseline in both groups (p<0.05). Group A (facial mask) after 1 hour: PaCO2 61.1±13.1 pH 7.34±0.08; after 6 hours PaCO2 56.1±12.8 pH 7.37±0.07. Group B (helmet) after 1 hour: PaCO2 68.9±13.8 pH 7.31±0.06; after 6 hours PaCO2 57.9±12.9 pH 7.36±0.07. No difference between the two groups was observed for vital parameters, discomfort scale and dyspnea score. CONCLUSIONS: This pilot randomized controlled trial shows that the helmet is a good interface to improve alveolar ventilation of COPD patients during an AHRF.