Continuous assessment of neuro-ventilatory drive during 12 h of pressure support ventilation in critically ill patients (original) (raw)
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American Journal of Respiratory and Critical Care Medicine, 2001
We compared crural diaphragm electrical activity (EAdi) with transdiaphragmatic pressure (Pdi) during varying levels of pressure support ventilation (PS) in 13 intubated patients. With changing PS, we found no evidence for changes in neuromechanical coupling of the diaphragm. From lowest to highest PS (2 cm H(2)O +/- 4 to 20 cm H(2)O +/- 7), tidal volume increased from 430 ml +/- 180 to 527 ml +/- 180 (p < 0.001). The inspiratory volume calculated during the period when EAdi increased to its peak did not change from 276 +/- 147 to 277 +/- 162 ml, p = 0.976. Respiratory rate decreased from 23.9 (+/- 7) to 21.3 (+/- 7) breaths/min (p = 0.015). EAdi and Pdi decreased proportionally by adding PS (r = 0.84 and r = 0.90, for mean and peak values, respectively). Mean and peak EAdi decreased (p < 0.001) by 33 +/- 21% (mean +/- SD) and 37 +/- 23% with the addition of 10 cm H(2)O of PS, similar to the decrease in the mean and peak Pdi (p < 0.001) observed (34 +/- 36 and 35 +/- 23%). We also found that ventilator assist continued during the diaphragm deactivation period, a phenomenon that was further exaggerated at higher PS levels. We conclude that EAdi is a valid measurement of neural drive to the diaphragm in acute respiratory failure.
Daily titration of neurally adjusted ventilatory assist using the diaphragm electrical activity
Intensive Care Medicine, 2011
Purpose: To determine the feasibility of daily titration of the neurally adjusted ventilatory assist (NAVA) level in relation to the maximal diaphragmatic electrical activity (EAdi maxSBT) measured during a spontaneous breathing trial (SBT) during pressure support ventilation (PSV). Methods: The study included 15 consecutive patients in whom mechanical ventilation weaning was initiated with the NAVA mode. EAdi maxSBT was determined daily during an SBT using PSV with 7 cmH 2 O of inspiratory pressure and no positive end-expiratory pressure (PEEP). If the SBT was unsuccessful, NAVA was used and the level was then adjusted to obtain an EAdi of *60% of the EAdi maxSBT. Arterial blood gas analyses were performed 20 min after each change in NAVA level. Results: Three patients were dropped from the study at day 4 because of worsening of their sickness. The median duration of NAVA ventilation was 4.5 days (IQR 3-6.5). From day 1 to extubation, EAdi max-SBT and EAdi increased significantly from 16.6 (9.6) to 21.7 (10.3) lV (P = 0.013) and from 10.0 (5.5) to 15.1 (9.2) lV (P = 0.026), respectively. The pressure delivered significantly decreased from 20 (8) to 10 (5) cmH 2 O (P = 0.003). Conversely, tidal volume, carbon dioxide tension, and pH values remained unchanged during the same period. Conclusion: These results suggest that daily titration of NAVA level with an electrical goal of *60% EAdi maxSBT is feasible and well tolerated. The respiratory mechanics improvement and increase in respiratory drive allowed for a daily reduction of the NAVA level while preserving breathing, oxygenation, and alveolar ventilation until extubation.
Impact of prolonged assisted ventilation on diaphragmatic efficiency: NAVA versus PSV
Critical Care, 2015
Background Prolonged controlled mechanical ventilation depresses diaphragmatic efficiency. Assisted modes of ventilation should improve it. We assessed the impact of pressure support ventilation versus neurally adjusted ventilator assist on diaphragmatic efficiency. Method Patients previously ventilated with controlled mechanical ventilation for 72 hours or more were randomized to be ventilated for 48 hours with pressure support ventilation (n =12) or neurally adjusted ventilatory assist (n = 13). Neuro-ventilatory efficiency (tidal volume/diaphragmatic electrical activity) and neuro-mechanical efficiency (pressure generated against the occluded airways/diaphragmatic electrical activity) were measured during three spontaneous breathing trials (0, 24 and 48 hours). Breathing pattern, diaphragmatic electrical activity and pressure time product of the diaphragm were assessed every 4 hours. Results In patients randomized to neurally adjusted ventilator assist, neuro-ventilatory efficien...
Critical Care, 2013
Introduction: A reliable prediction of successful weaning from respiratory support may be crucial for the overall outcome of the critically ill patient. The electrical activity of the diaphragm (EAdi) allows one to monitor the patients' respiratory drive and their ability to meet the increased respiratory demand. In this pilot study, we compared the EAdi with conventional parameters of weaning failure, such as the ratio of respiratory rate to tidal volume. Methods: We studied 18 mechanically ventilated patients considered difficult to wean. For a spontaneous breathing trial (SBT), the patients were disconnected from the ventilator and given oxygen through a T-piece. The SBT was evaluated by using standard criteria. Results: Twelve patients completed the SBT successfully, and six failed. The EAdi was significantly different in the two groups. We found an early increase in EAdi in the failing patients that was more pronounced than in any of the patients who successfully passed the SBT. Changes in EAdi predicted an SBT failure earlier than did conventional parameters. Conclusions: EAdi monitoring adds valuable information during weaning from the ventilator and may help to identify patients who are not ready for discontinuation of respiratory support.
To determine if, compared to pressure support (PS), neurally adjusted ventilatory assist (NAVA) reduces patient-ventilator asynchrony in intensive care patients undergoing noninvasive ventilation with an oronasal face mask. In this prospective interventional study we compared patient-ventilator synchrony between PS (with ventilator settings determined by the clinician) and NAVA (with the level set so as to obtain the same maximal airway pressure as in PS). Two 20-min recordings of airway pressure, flow and electrical activity of the diaphragm during PS and NAVA were acquired in a randomized order. Trigger delay (T(d)), the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s neural inspiratory time (T(in)), ventilator pressurization duration (T(iv)), inspiratory time in excess (T(iex)), number of asynchrony events per minute and asynchrony index (AI) were determined. The study included 13 patients, six with COPD, and two with mixed pulmonary disease. T(d) was reduced with NAVA: median 35 ms (IQR 31-53 ms) versus 181 ms (122-208 ms); p = 0.0002. NAVA reduced both premature and delayed cyclings in the majority of patients, but not the median T(iex) value. The total number of asynchrony events tended to be reduced with NAVA: 1.0 events/min (0.5-3.1 events/min) versus 4.4 events/min (0.9-12.1 events/min); p = 0.08. AI was lower with NAVA: 4.9 % (2.5-10.5 %) versus 15.8 % (5.5-49.6 %); p = 0.03. During NAVA, there were no ineffective efforts, or late or premature cyclings. PaO(2) and PaCO(2) were not different between ventilatory modes. Compared to PS, NAVA improved patient ventilator synchrony during noninvasive ventilation by reducing T(d) and AI. Moreover, with NAVA, ineffective efforts, and late and premature cyclings were absent.
Increased duration of mechanical ventilation is associated with decreased diaphragmatic force
Critical Care, 2010
Introduction: Respiratory muscle weakness is an important risk factor for delayed weaning. Animal data show that mechanical ventilation itself can cause atrophy and weakness of the diaphragm, called ventilator-induced diaphragmatic dysfunction (VIDD). Transdiaphragmatic pressure after magnetic stimulation (TwPdi BAMPS) allows evaluation of diaphragm strength. We aimed to evaluate the repeatability of TwPdi BAMPS in critically ill, mechanically ventilated patients and to describe the relation between TwPdi and the duration of mechanical ventilation.
Titration and Implementation of Neurally Adjusted Ventilatory Assist in Critically Ill Patients
CHEST Journal, 2009
Background: Neurally adjusted ventilatory assist (NAVA) delivers assist in proportion to the patient's respiratory drive as reflected by the diaphragm electrical activity (EAdi). We examined to what extent NAVA can unload inspiratory muscles, and whether unloading is sustainable when implementing a NAVA level identified as adequate (NAVAal) during a titration procedure. Methods: Fifteen adult, critically ill patients with a PaO 2 /fraction of inspired oxygen (FIO 2) ratio < 300 mm Hg were studied. NAVAal was identified based on the change from a steep increase to a less steep increase in airway pressure (Paw) and tidal volume (VT) in response to systematically increasing the NAVA level from low (NAVAlow) to high (NAVAhigh). NAVAal was implemented for 3 h. Results: At NAVAal, the median esophageal pressure time product (PTPes) and EAdi values were reduced by 47% of NAVAlow (quartiles, 16 to 69% of NAVAlow) and 18% of NAVAlow (quartiles, 15 to 26% of NAVAlow), respectively. At NAVAhigh, PTPes and EAdi values were reduced by 74% of NAVAlow (quartiles, 56 to 86% of NAVAlow) and 36% of NAVAlow (quartiles, 21 to 51% of NAVAlow; p < 0.005 for all). Parameters during 3 h on NAVAal were not different from parameters during titration at NAVAal, and were as follows: VT, 5.9 mL/kg predicted body weight (PBW) [quartiles, 5.4 to 7.2 mL/kg PBW]; respiratory rate (RR), 29 breaths/min (quartiles, 22 to 33 breaths/min); mean inspiratory Paw, 16 cm H 2 O (quartiles, 13 to 20 cm H 2 O); PTPes, 45% of NAVAlow (quartiles, 28 to 57% of NAVAlow); and EAdi, 76% of NAVAlow (quartiles, 63 to 89% of NAVAlow). PaO 2 /FIO 2 ratio, PaCO 2 , and cardiac performance during NAVAal were unchanged, while Paw and VT were lower, and RR was higher when compared to conventional ventilation before implementing NAVAal. Conclusions: Systematically increasing the NAVA level reduces respiratory drive, unloads respiratory muscles, and offers a method to determine an assist level that results in sustained unloading, low VT, and stable cardiopulmonary function when implemented for 3 h.
Journal of Applied Physiology
The patient-ventilator breath contribution (PVBC) index estimates the relative contribution of the patient to total tidal volume (Vtinsp) 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 (Vtinsp) and diaphragm electrical activity (EAdi) during assisted breaths (Vtinsp/EAdi)assist and during unassisted breaths (Vtinsp/EAdi)no-assist. Vtinsp was normalized to peak EAdi (EAdipeak) using 1) one assisted breath, 2) five consecutive assisted breaths, or 3) five assisted breaths with matching EAdi preceding the unassisted breath (N1PVBC2, X5PVBC2, and [Formula: see text], respectively). In addition, PVBC was calculated by comparing only Vtinsp for breaths with matching EAdi (PVBCβ2). Test-retest reliability of the different PVBC calculation methods was evaluated with the in...