Estimation of transpulmonary driving pressure using a lower assist maneuver (LAM) during synchronized ventilation in patients with acute respiratory failure: a physiological study.

Background: We previously showed in animals that transpulmonary driving pressure (PL) can be estimated during Neurally Adjusted Ventilatory Assist (NAVA) and Neural Pressure Support (NPS) using a single lower assist maneuver (LAM). The aim of this study was to test the LAM-based estimate of PL (PL_LAM) in patients with acute respiratory failure.

Methods: This was a prospective, physiological, and interventional study in intubated patients with acute respiratory failure.

Feasibility of synchronized high flow nasal cannula.

Background: A high-flow nasal cannula (cHFNC) delivers flow continuously (during inspiration and expiration). Using the diaphragm electrical activity (Edi), synchronizing HFNC could be an alternative (cycling high/low flow on inspiration/expiration, respectively). The objective of this study was to demonstrate the feasibility of synchronized HFNC (sHFNC) and compare it to cHFNC.

Dyssynchronous diaphragm contractions impair diaphragm function in mechanically ventilated patients.

Background: Pre-clinical studies suggest that dyssynchronous diaphragm contractions during mechanical ventilation may cause acute diaphragm dysfunction. We aimed to describe the variability in diaphragm contractile loading conditions during mechanical ventilation and to establish whether dyssynchronous diaphragm contractions are associated with the development of impaired diaphragm dysfunction.

Methods: In patients receiving invasive mechanical ventilation for pneumonia, septic shock, acute respiratory distress syndrome, or acute brain injury, airway flow and pressure and diaphragm electrical activity (Edi) were recorded hourly around the clock for up to 7 days.

Tidal volume delivery during nasal intermittent positive pressure ventilation: infant cannula vs. nasal continuous positive airway pressure prongs.

Objective: To measure tidal volume delivery during nasal intermittent positive pressure ventilation with two nasal interfaces: infant cannula and nasal prongs.

Study Design: A single-center crossover study of neonates with mild respiratory distress. Fifteen preterm neonates were randomized to initial interface of infant cannula or nasal prongs and monitored on a sequence of pressure settings first on the initial interface, then repeated on the alternate interface.

Predicting extubation in patients with traumatic cervical spinal cord injury using the diaphragm electrical activity during a single maximal maneuver.

Background: The unsuccessful extubation in patients with traumatic cervical spinal cord injuries (CSCI) may result from impairment diaphragm function and monitoring of diaphragm electrical activity (EAdi) can be informative in guiding extubation. We aimed to evaluate whether the change of EAdi during a single maximal maneuver can predict extubation outcomes in CSCI patients.

Methods: This is a retrospective study of CSCI patients requiring mechanical ventilation in the ICU of a tertiary hospital.

Estimation of transpulmonary driving pressure during synchronized mechanical ventilation using a single lower assist maneuver (LAM) in rabbits: a comparison to measurements made with an esophageal balloon.

Background: Mechanical ventilation is applied to unload the respiratory muscles, but knowledge about transpulmonary driving pressure (ΔP) is important to minimize lung injury. We propose a method to estimate ΔP during neurally synchronized assisted ventilation, with a simple intervention of lowering the assist for one breath ("lower assist maneuver", LAM).

Methods: In 24 rabbits breathing spontaneously with imposed loads, titrations of increasing assist were performed, with two neurally synchronized modes: neurally adjusted ventilatory assist (NAVA) and neurally triggered pressure support (NPS).

Synchronized and proportional sub-diaphragmatic unloading in an animal model of respiratory distress.

Background: A sealed abdominal interface was positioned below the diaphragm (the "NeoVest") to apply synchronized and proportional negative pressure ventilation (NPV) and was compared to positive pressure ventilation (PPV) using neurally adjusted ventilatory assist (NAVA). Both modes were controlled by the diaphragm electrical activity (Edi).

Methods: Eleven rabbits (mean weight 2.

Use of High-Rate Ventilation Results in Enhanced Recellularization of Bioengineered Lung Scaffolds.

While transplantation is a viable treatment option for end-stage lung diseases, this option is highly constrained by the availability of organs and postoperative complications. A potential solution is the use of bioengineered lungs generated from repopulated acellular scaffolds. Effective recellularization, however, remains a challenge.

Neurally Adjusted Ventilatory Assist in Newborns.

Patient-ventilator asynchrony is very common in newborns. Achieving synchrony is quite challenging because of small tidal volumes, high respiratory rates, and the presence of leaks. Leaks also cause unreliable monitoring of respiratory metrics.

Neurally adjusted ventilatory assist as a weaning mode for adults with invasive mechanical ventilation: a systematic review and meta-analysis.

Background: Prolonged ventilatory support is associated with poor clinical outcomes. Partial support modes, especially pressure support ventilation, are frequently used in clinical practice but are associated with patient-ventilation asynchrony and deliver fixed levels of assist. Neurally adjusted ventilatory assist (NAVA), a mode of partial ventilatory assist that reduces patient-ventilator asynchrony, may be an alternative for weaning.

Reverse Triggering Dyssynchrony 24 h after Initiation of Mechanical Ventilation.

Background: Reverse triggering is a delayed asynchronous contraction of the diaphragm triggered by passive insufflation by the ventilator in sedated mechanically ventilated patients. The incidence of reverse triggering is unknown. This study aimed at determining the incidence of reverse triggering in critically ill patients under controlled ventilation.

Duration of diaphragmatic inactivity after endotracheal intubation of critically ill patients.

Background: In patients intubated for mechanical ventilation, prolonged diaphragm inactivity could lead to weakness and poor outcome. Time to resume a minimal diaphragm activity may be related to sedation practice and patient severity.

Methods: Prospective observational study in critically ill patients.

Feasibility of neurally synchronized and proportional negative pressure ventilation in a small animal model.

Rationale: Synchronized positive pressure ventilation is possible using diaphragm electrical activity (EAdi) to control the ventilator. It is unknown whether EAdi can be used to control negative pressure ventilation.

Aim: To evaluate the feasibility of using EAdi to control negative pressure ventilation.

Continuous neurally adjusted ventilation: a feasibility study in preterm infants.

Objectives: To assess the feasibility and tolerance of NeuroPAP, a new non-invasive ventilation mode which continuously adjusts (during both inspiration and expiration) the pressure support proportionally to the diaphragm electrical activity (Edi), in preterm infants and to evaluate the impact on ventilation pressure and Edi.

Design: Prospective cross-over single-centre feasibility study.

Setting: One level 3 neonatal intensive care unit in Canada.

Work of Breathing in Premature Neonates: Noninvasive Neurally-Adjusted Ventilatory Assist versus Noninvasive Ventilation.

Background: We tested whether work of breathing in premature newborns estimated by phase angle (θ) by using respiratory inductance plethysmography is decreased during neurally-adjusted ventilatory assist (NAVA) noninvasive ventilation (NIV) versus NIV alone.

Methods: NAVA NIV and NIV were applied in random order while using respiratory inductance plethysmography to measure the phase angle.

Results: Patient-ventilator asynchrony was decreased during NAVA NIV; however, the phase angle was not different between the modes.

A novel non-invasive method to detect excessively high respiratory effort and dynamic transpulmonary driving pressure during mechanical ventilation.

Background: Excessive respiratory muscle effort during mechanical ventilation may cause patient self-inflicted lung injury and load-induced diaphragm myotrauma, but there are no non-invasive methods to reliably detect elevated transpulmonary driving pressure and elevated respiratory muscle effort during assisted ventilation. We hypothesized that the swing in airway pressure generated by respiratory muscle effort under assisted ventilation when the airway is briefly occluded (ΔP) could be used as a highly feasible non-invasive technique to screen for these conditions.

Methods: Respiratory muscle pressure (P), dynamic transpulmonary driving pressure (ΔP, the difference between peak and end-expiratory transpulmonary pressure), and ΔP were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada.

Effects of levosimendan on respiratory muscle function in patients weaning from mechanical ventilation.

Purpose: Respiratory muscle weakness frequently develops in critically ill patients and is associated with adverse outcome, including difficult weaning from mechanical ventilation. Today, no drug is approved to improve respiratory muscle function in these patients. Previously, we have shown that the calcium sensitizer levosimendan improves calcium sensitivity of human diaphragm muscle fibers in vitro and contractile efficiency of the diaphragm in healthy subjects.

Monitoring patient-ventilator breath contribution in the critically ill during neurally adjusted ventilatory assist: reliability and improved algorithms for bedside use.

The patient-ventilator breath contribution (PVBC) index estimates the relative contribution of the patient to total tidal volume (Vt) during mechanical ventilation in neurally adjusted ventilator assist mode and has been used to titrate ventilator support. The reliability of this index in ventilated patients is unknown and was investigated in this study. PVBC was calculated by comparing tidal volume (Vt) and diaphragm electrical activity (EAdi) during assisted breaths (Vt/EAdi) and during unassisted breaths (Vt/EAdi).

Control of respiratory drive by extracorporeal CO removal in acute exacerbation of COPD breathing on non-invasive NAVA.

Background: Veno-venous extracorporeal CO removal (vv-ECCOR) and non-invasive neurally adjusted ventilator assist (NIV-NAVA) are two promising techniques which may prevent complications related to prolonged invasive mechanical ventilation in patients with acute exacerbation of COPD.

Methods: A physiological study of the electrical activity of the diaphragm (Edi) response was conducted with varying degrees of extracorporeal CO removal to control the respiratory drive in patients with severe acute exacerbation of COPD breathing on NIV-NAVA.

Results: Twenty COPD patients (SAPS II 37 ± 5.

Tidal volume transmission during non-synchronized nasal intermittent positive pressure ventilation via RAM cannula.

Background: Nasal intermittent positive pressure ventilation (NIPPV) is a widely used mode of support in neonates, during which ventilator inflations may or may not coincide with spontaneous breathing.

Objective: We tested the hypothesis that inflations delivered with NIPPV via RAM cannula and not accompanied by patient effort produce minimal tidal volume as measured by respiratory inductance plethysmography.

Design/methods: Fourteen subjects were monitored while receiving NIPPV.

Estimation of the diaphragm neuromuscular efficiency index in mechanically ventilated critically ill patients.

Background: Diaphragm dysfunction develops frequently in ventilated intensive care unit (ICU) patients. Both disuse atrophy (ventilator over-assist) and high respiratory muscle effort (ventilator under-assist) seem to be involved. A strong rationale exists to monitor diaphragm effort and titrate support to maintain respiratory muscle activity within physiological limits.

Neural Breathing Pattern and Patient-Ventilator Interaction During Neurally Adjusted Ventilatory Assist and Conventional Ventilation in Newborns.

Objective: To compare neurally adjusted ventilatory assist and conventional ventilation on patient-ventilator interaction and neural breathing patterns, with a focus on central apnea in preterm infants.

Design: Prospective, observational cross-over study of intubated and ventilated newborns. Data were collected while infants were successively ventilated with three different ventilator conditions (30 min each period): 1) synchronized intermittent mandatory ventilation (SIMV) combined with pressure support at the clinically prescribed, SIMV with baseline settings (SIMVBL), 2) neurally adjusted ventilatory assist, 3) same as SIMVBL, but with an adjustment of the inspiratory time of the mandatory breaths (SIMV with adjusted settings [SIMVADJ]) using feedback from the electrical activity of the diaphragm).

Neural breathing pattern in newborn infants pre- and postextubation.

Aim: To describe the neural breathing pattern before and after extubation in newborn infants.

Methods: Prospective, observational study. In infants deemed ready for extubation, the diaphragm electrical activity (EAdi) was continuously recorded from 30 minute before to two hours after extubation.