The optimal noninvasive respiratory support for acute hypoxemic respiratory failure is debated. Recent preliminary data indicate that both pressure-support noninvasive ventilation (NIV) and continuous-positive airway pressure (CPAP) may be of benefit. While often applied interchangeably in clinical practice, NIV and CPAP have different effects on the inspiratory effort, which is the major determinant of self-inflicted lung injury. Also, inspiratory effort widely varies among individuals. The purpose of this study is to assess the physiological effects of a noninvasive respiratory support approach guided by inspiratory effort, as compared to CPAP and NIV, in patients with moderate-to-severe acute hypoxemic respiratory failure.
Patients with acute hypoxemic respiratory failure will undergo a decremental pressure-support trial during helmet noninvasive support. The following pressure-support settings will be applied sequentially, with positive end-expiratory pressure kept constant and equal to 10-12 cmH2O: 20 cmH2O, 16 cmH2O, 12 cmH2O, 8 cmH2O and high-flow-driven CPAP. Inspiratory effort will be monitored during the trial through esophageal manometry. The personalized setting of noninvasive support will be defined as the minimal pressure-support level capable of generating inspiratory effort between 5 and 10 cmH2O. Personalized noninvasive support will be then compared to conventionally-set NIV and CPAP in a randomized cross-over trial.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
20
Noninvasive respiratory support delivered through a helmet
Fondazione Policlinico Universitaro A. Gemelli IRCCS
Rome, Italy
Tidal volume
Tidal volume size, assessed with electrical impedance tomography
Time frame: 1 hour
Transpulmonary driving pressure
The positive inspiratory swing in transpulmonary pressure, calculated as airway pressure minus esophageal pressure
Time frame: 1 hour
Inspiratory effort
Inspiratory effort, defined as the negative deflection in esophageal pressure
Time frame: 1 hour
Respiratory rate
Respiratory rate per minute
Time frame: 1 hour
Blood oxygenation
PaO2/FiO2 ratio
Time frame: 1 hour
Work of breathing
Simplified esophageal pressure pressure-time product
Time frame: 1 hour
Corrected minute ventilation
Minute ventilation (assessed with electrical impedance tomography) normalized to PaCO2
Time frame: 1 hour
Tidal volume distribution
Tidal volume distribution in the four lung regions of interest (ventral, mid-ventral, mid-dorsal and dorsal), assessed with electrical impedance tomography
Time frame: 1 hour
End-expiratory lung impedance
End-expiratory lung impedance, assessed with electrical impedance tomography
Time frame: 1 hour
Pendelluft extent
Pendelluft, assessed with electrical impedance tomography and expressed in % of tidal volume size
Time frame: 1 hour
Lung compliance
Defined as the ration of tidal volume to transpulmonary driving pressure
Time frame: 1 hour
Dyspnea
Dyspnea, defined through a visual analog scale ((ranging from 0 to 10, with representing most severe dyspnea)
Time frame: 1 hour
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