Short-term effects of neuromuscular blockade on global and regional lung mechanics, oxygenation and ventilation in pediatric acute hypoxemic respiratory failure

Background: Neuromuscular blockade (NMB) has been shown to improve outcome in acute respiratory distress syndrome (ARDS) in adults, challenging maintaining spontaneous breathing when there is severe lung injury. We tested in a prospective physiological study the hypothesis that continuous administration of NMB agents in mechanically ventilated children with severe acute hypoxemic respiratory failure (AHRF) improves the oxygenation index without a redistribution of tidal volume VT toward non-dependent lung zones. Methods: Oxygenation index, PaO2/FiO(2) ratio, lung mechanics (plateau pressure, mean airway pressure, respiratory system compliance and resistance), hemodynamics (heart rate, central venous and arterial blood pressures), oxygenation [ oxygenation index (OI), PaO2/FiO(2) and SpO(2)/FiO(2)], ventilation (physiological dead space-to-VT ratio) and electrical impedance tomography measured changes in end-expiratory lung volume (EELV), and VT distribution was measured before and 15 min after the start of continuous infusion of rocuronium 1 mg/kg. Patients were ventilated in a time-cycled, pressure-limited mode with pre-set VT. All ventilator settings were not changed during the study. Results: Twenty-two patients were studied (N = 18 met the criteria for pediatric ARDS). Median age (25-75 interquartile range) was 15 (7.8-77.5) weeks. Pulmonary pathology was present in 77.3%. The median lung injury score was 9 (8-10). The overall median CoV and regional lung filling characteristics were not affected by NMB, indicating no ventilation shift toward the non-dependent lung zones. Regional analysis showed a homogeneous time course of lung inflation during inspiration, indicating no tendency to atelectasis after the introduction of NMB. NMB decreased the mean airway pressure (p = 0.039) and OI (p = 0.039) in all patients. There were no significant changes in lung mechanics, hemodynamics and EELV. Subgroup analysis showed that OI decreased (p = 0.01) and PaO2/FiO(2) increased (p = 0.02) in patients with moderate or severe PARDS. Conclusions: NMB resulted in an improved oxygenation index in pediatric patients with AHRF. Distribution of VT and regional lung filling characteristics were not affected

Patient-Ventilator Asynchrony During Assisted Ventilation in Children

Objective: To describe the frequency and type of patient-ventilator asynchrony in mechanically ventilated children by analyzing ventilator flow and pressure signals. Design: Prospective observational study. Setting: Tertiary PICU in a university hospital. Patients: Mechanically ventilated children between 0 and 18 years old and who were able to initiate and maintain spontaneous breathing were eligible for inclusion. Patients with congenital or acquired neuromuscular disorders, those with congenital or acquired central nervous system disorders, and those who were unable to initiate and maintain spontaneous breathing from any other cause were excluded. Interventions: None. Measurements and Main Results: All patients were ventilated in a time-cycled, pressure-limited mode with flow triggering set at 1.0 L/min by using the Evita XL (Drager, Lubeck, Germany). Patient-ventilator asynchrony was identified by a random 30-minute continuous recording and an offline analysis of the flow and pressure signals. Patient-ventilator asynchrony was categorized and labeled into four different groups: 1) trigger asynchrony (i.e., insensitive trigger, double triggering, autotriggering, or trigger delay), 2) flow asynchrony, 3) termination asynchrony (i.e., delayed or premature termination), and 4) expiratory asynchrony. Flow and pressure signals were recorded in 45 patients for 30 minutes. A total number of 57,651 breaths were analyzed. Patient-ventilator asynchrony occurred in 19,175 breaths (33%), and it was seen in every patient. Ineffective triggering was the most predominant type of asynchrony (68%), followed by delayed termination (19%), double triggering (4%), and premature termination (3%). Patient-ventilator asynchrony significantly increased with lower levels of peak inspiratory pressure, positive end-expiratory pressure, and set frequency. Conclusions: Patient-ventilator asynchrony is extremely common in mechanically ventilated children, and the predominant cause is ineffective triggering