Heart–lung interactions during neurally adjusted ventilatory assist

Abstract

IntroductionAssist in unison to the patient’s inspiratory neural effort and feedback-controlled limitation of lung distension with neurally adjusted ventilatory assist (NAVA) may reduce the negative effects of mechanical ventilation on right ventricular function.MethodsHeart–lung interaction was evaluated in 10 intubated patients with impaired cardiac function using esophageal balloons, pulmonary artery catheters and echocardiography. Adequate NAVA level identified by a titration procedure to breathing pattern (NAVAal), 50% NAVAal, and 200% NAVAal and adequate pressure support (PSVal, defined clinically), 50% PSVal, and 150% PSVal were implemented at constant positive end-expiratory pressure for 20 minutes each.ResultsNAVAal was 3.1 ± 1.1cmH2O/μV and PSVal was 17 ± 2 cmH20. For all NAVA levels negative esophageal pressure deflections were observed during inspiration whereas this pattern was reversed during PSVal and PSVhigh. As compared to expiration, inspiratory right ventricular outflow tract velocity time integral (surrogating stroke volume) was 103 ± 4%, 109 ± 5%, and 100 ± 4% for NAVAlow, NAVAal, and NAVAhigh and 101 ± 3%, 89 ± 6%, and 83 ± 9% for PSVlow, PSVal, and PSVhigh, respectively (p < 0.001 level-mode interaction, ANOVA). Right ventricular systolic isovolumetric pressure increased from 11.0 ± 4.6 mmHg at PSVlow to 14.0 ± 4.6 mmHg at PSVhigh but remained unchanged (11.5 ± 4.7 mmHg (NAVAlow) and 10.8 ± 4.2 mmHg (NAVAhigh), level-mode interaction p = 0.005). Both indicate progressive right ventricular outflow impedance with increasing pressure support ventilation (PSV), but no change with increasing NAVA level.ConclusionsRight ventricular performance is less impaired during NAVA compared to PSV as used in this study. Proposed mechanisms are preservation of cyclic intrathoracic pressure changes characteristic of spontaneous breathing and limitation of right-ventricular outflow impedance during inspiration, regardless of the NAVA level.Trial registrationClinicaltrials.gov Identifier: NCT00647361, registered 19 March 2008Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0499-8) contains supplementary material, which is available to authorized users.

Neurally adjusted ventilatory assist (NAVA) allows patient-ventilator synchrony during pediatric noninvasive ventilation: a crossover physiological study

“…The cycling-off dys-synchronies are reported as absolute values as cycling-off dys-synchronies usually have a wide distribution of values with positive or negative values [17,29]; (c) ineffective effort: neural breath not assisted by the ventilator; (d) autotriggered breath: initiation of mechanical assist by the ventilator without an inflection of EAdi. The four types of events were detected breath-by-breath with semiautomatic analysis (one automatic step followed by a manual verification) of EAdi and airway pressure waveforms, comparing the neural timing and the ventilator timing [30].…”

Dysfunction of respiratory muscles in critically ill patients on the intensive care unit

“…93 As the support level is titrated against the patient's respiratory demand, patients are protected against over-assist. 122,123 This approach was successfully used in various clinical ICU settings 97,122,124,125 but most importantly in patients with critical illness myo-neuropathy. 97 Currently, no medical treatment for VIDD is available.…”

Neurally Adjusted Ventilatory Assist Is Associated with Greater Initial Extubation Success in Postoperative Congenital Heart Disease Patients when Compared to Conventional Mechanical Ventilation

“…1 Ventilation with NAVA enhances myocardial function by improving patient-ventilator synchrony leading to decreased diaphragmatic work and minimizing patient stress thereby reducing oxygen delivery demands on the myocardium. 29 NAVA minimizes dynamic hyperinflation and decreases aw: As native respiratory rates increase during mechanical ventilatory weaning in infants and children, dynamic hyperinflation risks increase. By means of coupling Edi to the clinician-determined NAVA level, NAVA decreases the risk of dynamic hyperinflation by preventing the continued delivery of assist breaths in the neural expiratory phase seen in conventional MV.…”