Electrical Activity Of Diaphragm Research Articles

Neurally adjusted ventilatory assist for children on veno-venous ECMO.

NAVA may improve veno-venous ECMO weaning in children. This is a retrospective small series, describing for the first time proof-of-principle for the use of NAVA in children on VV ECMO. Six patients (age 1-48months) needed veno-venous ECMO. Controlled conventional ventilation was replaced with assisted ventilation as soon as lung compliance improved, and could trigger initiation and termination of ventilation. NAVA was then initiated when diaphragmatic electrical activity (EAdi) allowed for triggering. NAVA was possible in all patients. Proportionate to EAdi (1.8-26μV), initial peak inspiratory pressures ranged from 21 to 34cm H2O, and the tidal volume (Vt) from 3 to 7ml/kg. During weaning, peak pressures increased proportionally to EAdi increase (5.2-41μV), with tidal volumes ranging from 6.6 to 8.6ml/kg. ECMO was weaned after a median time of 1.75days on NAVA. Following ECMO weaning, the median duration of mechanical ventilation, and intensive care unit stay were 4.5days, and 13.5days, respectively. Survival to hospital discharge was 100%. In conclusion, combining NAVA to ECMO in paediatric respiratory failure is safe and feasible, and may help in a smoother ECMO weaning, since NAVA allows the patient to drive the ventilator and regulate Vt according to needs.

Measurement of Diaphragmatic Electrical Activity by Surface Electromyography in Intubated Subjects and Its Relationship With Inspiratory Effort.

Quantification of patient effort during spontaneous breathing is important to tailor ventilatory assistance. Because a correlation between inspiratory muscle pressure (Pmus) and electrical activity of the diaphragm (EAdi) has been described, we aimed to assess the reliability of surface electromyography (EMG) of the respiratory muscles for monitoring diaphragm electrical activity and subject effort during assisted ventilation. At a general ICU of a single university-affiliated hospital, we enrolled subjects who were intubated and on pressure support ventilation (PSV) and were on mechanical ventilation for > 48 h. The subjects were studied at 3 levels of pressure support. Airway flow and pressure; esophageal pressure; EAdi; and surface EMG of the diaphragm (surface EAdi), intercostal, and sternocleidomastoid muscles were recorded. Respiratory cycles were sampled for off-line analysis. The Pmus/EAdi index (PEI) was calculated by relying on EAdi and surface EAdi (surface PEI) from an airway pressure drop during end-expiratory occlusions performed every minute. surface EAdi well correlated with EAdi and Pmus, in particular, after averaging breaths into deciles (R = 0.92 and R = 0.84). When surface PEI was used with surface EAdi, it provided a reliable estimation of Pmus (R = 0.94 in comparison with measured Pmus). During assisted mechanical ventilation, EAdi can be reliably monitored by both EAdi and surface EMG. The measurement of Pmus based on the calibration of EAdi was also feasible by the use of surface EMG.

Respiratory Muscle Effort during Expiration in Successful and Failed Weaning from Mechanical Ventilation.

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Respiratory muscle weakness in critically ill patients is associated with difficulty in weaning from mechanical ventilation. Previous studies have mainly focused on inspiratory muscle activity during weaning; expiratory muscle activity is less well understood. The current study describes expiratory muscle activity during weaning, including tonic diaphragm activity. The authors hypothesized that expiratory muscle effort is greater in patients who fail to wean compared to those who wean successfully. Twenty adult patients receiving mechanical ventilation (more than 72 h) performed a spontaneous breathing trial. Tidal volume, transdiaphragmatic pressure, diaphragm electrical activity, and diaphragm neuromechanical efficiency were calculated on a breath-by-breath basis. Inspiratory (and expiratory) muscle efforts were calculated as the inspiratory esophageal (and expiratory gastric) pressure-time products, respectively. Nine patients failed weaning. The contribution of the expiratory muscles to total respiratory muscle effort increased in the "failure" group from 13 ± 9% at onset to 24 ± 10% at the end of the breathing trial (P = 0.047); there was no increase in the "success" group. Diaphragm electrical activity (expressed as the percentage of inspiratory peak) was low at end expiration (failure, 3 ± 2%; success, 4 ± 6%) and equal between groups during the entire expiratory phase (P = 0.407). Diaphragm neuromechanical efficiency was lower in the failure versus success groups (0.38 ± 0.16 vs. 0.71 ± 0.36 cm H2O/μV; P = 0.054). Weaning failure (vs. success) is associated with increased effort of the expiratory muscles and impaired neuromechanical efficiency of the diaphragm but no difference in tonic activity of the diaphragm.

High-flow nasal cannula oxygen therapy decreases postextubation neuroventilatory drive and work of breathing in patients with chronic obstructive pulmonary disease

BackgroundThe physiological effects of high-flow nasal cannula O2 therapy (HFNC) have been evaluated mainly in patients with hypoxemic respiratory failure. In this study, we compared the effects of HFNC and conventional low-flow O2 therapy on the neuroventilatory drive and work of breathing postextubation in patients with a background of chronic obstructive pulmonary disease (COPD) who had received mechanical ventilation for hypercapnic respiratory failure.MethodsThis was a single center, unblinded, cross-over study on 14 postextubation COPD patients who were recovering from an episode of acute hypercapnic respiratory failure of various etiologies. After extubation, each patient received two 1-h periods of HFNC (HFNC1 and HFNC2) alternated with 1 h of conventional low-flow O2 therapy via a face mask. The inspiratory fraction of oxygen was titrated to achieve an arterial O2 saturation target of 88–92%. Gas exchange, breathing pattern, neuroventilatory drive (electrical diaphragmatic activity (EAdi)) and work of breathing (inspiratory trans-diaphragmatic pressure-time product per minute (PTPDI/min)) were recorded.ResultsEAdi peak increased from a mean (±SD) of 15.4 ± 6.4 to 23.6 ± 10.5 μV switching from HFNC1 to conventional O2, and then returned to 15.2 ± 6.4 μV during HFNC2 (conventional O2: p < 0.05 versus HFNC1 and HFNC2). Similarly, the PTPDI/min increased from 135 ± 60 to 211 ± 70 cmH2O/s/min, and then decreased again during HFNC2 to 132 ± 56 (conventional O2: p < 0.05 versus HFNC1 and HFNC2).ConclusionsIn patients with COPD, the application of HFNC postextubation significantly decreased the neuroventilatory drive and work of breathing compared with conventional O2 therapy.

Assessment of Inspiratory Muscle Activation using Surface Diaphragm Mechanomyography and Crural Diaphragm Electromyography.

The relationship between surface diaphragm mechanomyography (sMMGdi), as a noninvasive measure of inspiratory muscle mechanical activation, and crural diaphragm electromyography (oesEMGdi), as the invasive gold standard measure of diaphragm electrical activation, had not previously been examined. To investigate this relationship, oesEMGdi and sMMGdi were measured simultaneously in 6 healthy subjects during an incremental inspiratory threshold loading protocol, and analyzed using fixed sample entropy (fSampEn). A positive curvilinear relationship was observed between mean fSampEn sMMGdi and oesEMGdi (r = 0.67). Accordingly, an increasing electromechanical ratio was also observed with increasing inspiratory load. These findings suggest that sMMGdi could provide useful noninvasive measures of inspiratory muscle mechanical activation.

Abstract P-609: THE EFFECT OF MECHANICAL VENTILATION ON DIAPHRAGM FUNCTION IN INFANTS AND CHILDREN: AN EXPLORATORY STUDY

Aims & Objectives: Mechanical ventilation (MV) leads to diaphragm dysfunction in adults, with associated morbidity. There is limited research on ventilator-induced diaphragmatic dysfunction in the paediatric population. This study aimed to describe the change in diaphragmatic function during MV in children admitted to the paediatric intensive care unit (PICU). Methods This was a prospective observational study conducted in the PICU of Red Cross War Memorial Children’s Hospital, Cape Town, South Africa. Daily standardised ultrasound measures were taken of diaphragm end-inspiratory and end-expiratory thickness, from which contractile activity (thickening fraction) was calculated. Diaphragm electrical activity, using surface electromyography was also measured daily in a standardised manner. The study received institutional ethical approval and informed consent was taken from parents/guardians. Results Twenty-five participants were included, with 24 (67% male; median age 6.5 months) in the final analysis. Median duration of ventilation was three days; there were no cases of extubation failure. One patient received a neuromuscular blocking agent for two MV days. Diaphragm electrical activity decreased significantly over the first three MV days (p = 0.007), increasing significantly again at day 2 post-extubation (p = 0.008). Variable changes in diaphragm thickness and thickening fraction occurred over the course of MV, with no clear pattern of change. Changes in diaphragm contractile activity in either direction (increased or decreased) were associated with an increase in MV duration. Conclusions More research is required to determine the impact of MV on diaphragmatic function in infants and children, and how diaphragmatic function may impact on clinical outcomes in the paediatric population.

Compensatory plasticity in diaphragm and intercostal muscle utilization in a rat model of ALS

In SOD1G93A transgenic rat model of ALS, breathing capacity is preserved until late in disease progression despite profound respiratory motor neuron (MN) cell death. To explore mechanisms preserving breathing capacity, we assessed inspiratory EMG activity in diaphragm and external intercostal T2 (EIC2) and T5 (EIC5) muscles in anesthetized SOD1G93A rats at disease end-stage (20% decrease in body mass). We hypothesized that despite significant phrenic motor neuron loss and decreased phrenic nerve activity, diaphragm electrical activity and trans-diaphragmatic pressure (Pdi) are maintained to sustain ventilation. We alternatively hypothesized that EIC activity is enhanced, compensating for impaired diaphragm function. Diaphragm, EIC2 and EIC5 muscle EMGs and Pdi were measured in urethane-anesthetized, spontaneously breathing female SOD1G93A rats versus wild-type littermates during normoxia (arterial PO2 ~90mmHg, PCO2 ~45mmHg), maximal chemoreceptor stimulation (MCS: 10.5% O2/7% CO2), spontaneous augmented breaths and sustained tracheal occlusion. Phrenic MNs were counted in C3-5; T2 and T5 ventrolateral MNs were counted. In end-stage SOD1G93A rats, 29% of phrenic MNs survived (vs. wild-type), yet integrated diaphragm EMG amplitude was normal. Nevertheless, maximal Pdi decreased ~30% vs. wild type (p<0.01) and increased esophageal to gastric pressure ratio (p<0.05), consistent with persistent diaphragm weakness. Despite major T2 and T5 MN death, integrated EIC2 (100% greater than wild type) and EIC5 (300%) EMG amplitudes were increased in mutant rats during normoxia (p<0.01), possibly compensating for decreased Pdi. Thus, despite significant phrenic MN loss, diaphragm EMG activity is maintained; in contrast, Pdi was not, suggesting diaphragm dysfunction. Presumably, increased EIC EMG activity compensated for persistent diaphragm weakness. These adjustments contribute to remarkable preservation of breathing ability despite major respiratory motor neuron death and diaphragm dysfunction.

Efficacy of ventilator waveform observation for detection of patient-ventilator asynchrony during NIV: a multicentre study.

The objective of this study was to assess ability to identify asynchronies during noninvasive ventilation (NIV) through ventilator waveforms according to experience and interface, and to ascertain the influence of breathing pattern and respiratory drive on sensitivity and prevalence of asynchronies.35 expert and 35 nonexpert physicians evaluated 40 5-min NIV reports displaying flow–time and airway pressure–time tracings; identified asynchronies were compared with those ascertained by three examiners who evaluated the same reports displaying, additionally, tracings of diaphragm electrical activity. We determined: 1) sensitivity, specificity, and positive and negative predictive values; 2) the correlation between the double true index (DTI) of each report (i.e., the ratio between the sum of true positives and true negatives, and the overall breath count) and the corresponding asynchrony index (AI); and 3) the influence of breathing pattern and respiratory drive on both AI and sensitivity.Sensitivities to detect asynchronies were low either according to experience (0.20 (95% CI 0.14–0.29) for expert versus 0.21 (95% CI 0.12–0.30) for nonexpert, p=0.837) or interface (0.28 (95% CI 0.17–0.37) for mask versus 0.10 (95% CI 0.05–0.16) for helmet, p<0.0001). DTI inversely correlated with the AI (r2=0.67, p<0.0001). Breathing pattern and respiratory drive did not affect prevalence of asynchronies and sensitivity.Patient–ventilator asynchrony during NIV is difficult to recognise solely by visual inspection of ventilator waveforms.

Neural breathing pattern in newborn infants pre‐ and postextubation

To describe the neural breathing pattern before and after extubation in newborn infants. 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. Total of 25 neonates underwent 29 extubations; 10 extubations resulted in re-intubation within 72 hours. Postextubation, there was an increase in peak EAdi (EAdi-max) and EAdi-delta (peak minus minimum EAdi) in both groups. The pre- to postextubation change in EAdi-max (8.9-11.1 μv) and EAdi-delta (6-8 μv) was less in the failure group in comparison with the change in EAdi-max (10.2-13.4 μv) and EAdi-delta (6.3-10.6 μv) in the success group, (p = 0.02 and 0.01, respectively). In our neonatal cohort, extubation failure was associated with a smaller increase in peak and delta EAdi after extubation. If confirmed, these findings indicate an important cause of extubation failure in preterm infants.

New setting of neurally adjusted ventilatory assist for noninvasive ventilation by facial mask: a physiologic study

BackgroundNoninvasive ventilation (NIV) is generally delivered using pneumatically-triggered and cycled-off pressure support (PSP) through a mask. Neurally adjusted ventilatory assist (NAVA) is the only ventilatory mode that uses a non-pneumatic signal, i.e., diaphragm electrical activity (EAdi), to trigger and drive ventilator assistance. A specific setting to generate neurally controlled pressure support (PSN) was recently proposed for delivering NIV by helmet. We compared PSN with PSP and NAVA during NIV using a facial mask, with respect to patient comfort, gas exchange, and patient-ventilator interaction and synchrony.MethodsThree 30-minute trials of NIV were randomly delivered to 14 patients immediately after extubation to prevent post-extubation respiratory failure: (1) PSP, with an inspiratory support ≥8 cmH2O; (2) NAVA, adjusting the NAVA level to achieve a comparable peak EAdi (EAdipeak) as during PSP; and (3) PSN, setting the NAVA level at 15 cmH2O/μV with an upper airway pressure (Paw) limit to obtain the same overall Paw applied during PSP. We assessed patient comfort, peak inspiratory flow (PIF), time to reach PIF (PIFtime), EAdipeak, arterial blood gases, pressure-time product of the first 300 ms (PTP300-index) and 500 ms (PTP500-index) after initiation of patient effort, inspiratory trigger delay (DelayTR-insp), and rate of asynchrony, determined as asynchrony index (AI%). The categorical variables were compared using the McNemar test, and continuous variables by the Friedman test followed by the Wilcoxon test with Bonferroni correction for multiple comparisons (p < 0.017).ResultsPSN significantly improved patient comfort, compared to both PSP (p = 0.001) and NAVA (p = 0.002), without differences between the two latter (p = 0.08). PIF (p = 0.109), EAdipeak (p = 0.931) and gas exchange were similar between modes. Compared to PSP and NAVA, PSN reduced PIFtime (p < 0.001), and increased PTP300-index (p = 0.004) and PTP500-index (p = 0.001). NAVA and PSN significantly reduced DelayTR-insp, as opposed to PSP (p < 0.001). During both NAVA and PSN, AI% was <10% in all patients, while AI% was ≥10% in 7 patients (50%) with PSP (p = 0.023 compared with both NAVA and PSN).ConclusionsCompared to both PSP and NAVA, PSN improved comfort and patient-ventilator interaction during NIV by facial mask. PSN also improved synchrony, as opposed to PSP only.Trial registrationClinicalTrials.gov, NCT03041402. Registered (retrospectively) on 2 February 2017.

Partial Neuromuscular Blockade during Partial Ventilatory Support in Sedated Patients with High Tidal Volumes.

Controlled mechanical ventilation is used to deliver lung-protective ventilation in patients with acute respiratory distress syndrome. Despite recognized benefits, such as preserved diaphragm activity, partial support ventilation modes may be incompatible with lung-protective ventilation due to high Vt and high transpulmonary pressure. As an alternative to high-dose sedatives and controlled mechanical ventilation, pharmacologically induced neuromechanical uncoupling of the diaphragm should facilitate lung-protective ventilation under partial support modes. To investigate whether partial neuromuscular blockade can facilitate lung-protective ventilation while maintaining diaphragm activity under partial ventilatory support. In a proof-of-concept study, we enrolled 10 patients with lung injury and a Vt greater than 8 ml/kg under pressure support ventilation (PSV) and under sedation. After baseline measurements, rocuronium administration was titrated to a target Vt of 6 ml/kg during neurally adjusted ventilatory assist (NAVA). Thereafter, patients were ventilated in PSV and NAVA under continuous rocuronium infusion for 2 hours. Respiratory parameters, hemodynamic parameters, and blood gas values were measured. Rocuronium titration resulted in significant declines of Vt (mean ± SEM, 9.3 ± 0.6 to 5.6 ± 0.2 ml/kg; P < 0.0001), transpulmonary pressure (26.7 ± 2.5 to 10.7 ± 1.2 cm H2O; P < 0.0001), and diaphragm electrical activity (17.4 ± 2.3 to 4.5 ± 0.7 μV; P < 0.0001), and could be maintained under continuous rocuronium infusion. During titration, pH decreased (7.42 ± 0.02 to 7.35 ± 0.02; P < 0.0001), and mean arterial blood pressure increased (84 ± 6 to 99 ± 6 mm Hg; P = 0.0004), as did heart rate (83 ± 7 to 93 ± 8 beats/min; P = 0.0004). Partial neuromuscular blockade facilitates lung-protective ventilation during partial ventilatory support, while maintaining diaphragm activity, in sedated patients with lung injury.

Demonstration of improved electrical diaphragmatic activity (Edi) signal in a preterm infant following high dose caffeine citrate

Demonstration of improved electrical diaphragmatic activity (Edi) signal in a preterm infant following high dose caffeine citrate

A diaphragmatic electrical activity-based optimization strategy during pressure support ventilation improves synchronization but does not impact work of breathing

BackgroundPoor patient-ventilator synchronization is often observed during pressure support ventilation (PSV) and has been associated with prolonged duration of mechanical ventilation and poor outcome. Diaphragmatic electrical activity (Eadi) recorded using specialized nasogastric tubes is a surrogate of respiratory brain stem output. This study aimed at testing whether adapting ventilator settings during PSV using a protocolized Eadi-based optimization strategy, or Eadi-triggered and -cycled assisted pressure ventilation (or PSVN) could (1) improve patient-ventilator interaction and (2) reduce or normalize patient respiratory effort as estimated by the work of breathing (WOB) and the pressure time product (PTP).MethodsThis was a prospective cross-over study. Patients with a known chronic pulmonary obstructive or restrictive disease, asynchronies or suspected intrinsic positive end-expiratory pressure (PEEP) who were ventilated using PSV were enrolled in the study. Four different ventilator settings were sequentially applied for 15 minutes (step 1: baseline PSV as set by the clinician, step 2: Eadi-optimized PSV to adjust PS level, inspiratory trigger, and cycling settings, step 3: step 2 + PEEP adjustment, step 4: PSVN). The same settings as step 3 were applied again after step 4 to rule out a potential effect of time. Breathing pattern, trigger delay (Td), inspiratory time in excess (Tiex), pressure-time product (PTP), and work of breathing (WOB) were measured at the end of each step.ResultsEleven patients were enrolled in the study. Eadi-optimized PSV reduced Td without altering Tiex in comparison with baseline PSV. PSVN reduced Td and Tiex in comparison with baseline and Eadi-optimized PSV. Respiratory pattern did not change during the four steps. The improvement in patient-ventilator interaction did not lead to changes in WOB or PTP.ConclusionsEadi-optimized PSV allows improving patient ventilator interaction but does not alter patient effort in patients with mild asynchrony.Trial registrationClinicaltrials.gov identifier: NCT 02067403. Registered 7 February 2014.

Procedures for measuring and verifying gastric tube placement in newborns: an integrative review.

ABSTRACTObjective:to investigate evidence in the literature on procedures for measuring gastric tube insertion in newborns and verifying its placement, using alternative procedures to radiological examination. Method:an integrative review of the literature carried out in the Cochrane, LILACS, CINAHL, EMBASE, MEDLINE and Scopus databases using the descriptors “Intubation, gastrointestinal” and “newborns” in original articles. Results:seventeen publications were included and categorized as “measuring method” or “technique for verifying placement”. Regarding measuring methods, the measurements of two morphological distances and the application of two formulas, one based on weight and another based on height, were found. Regarding the techniques for assessing placement, the following were found: electromagnetic tracing, diaphragm electrical activity, CO2 detection, indigo carmine solution, epigastrium auscultation, gastric secretion aspiration, color inspection, and evaluation of pH, enzymes and bilirubin. Conclusion:the measuring method using nose to earlobe to a point midway between the xiphoid process and the umbilicus measurement presents the best evidence. Equations based on weight and height need to be experimentally tested. The return of secretion into the tube aspiration, color assessment and secretion pH are reliable indicators to identify gastric tube placement, and are the currently indicated techniques.

The Diaphragm Acts as a Brake during Expiration to Prevent Lung Collapse.

The diaphragm is the major inspiratory muscle and is assumed to relax during expiration. However, electrical postinspiratory activity has been observed. Whether there is an expiratory diaphragmatic contraction that preserves lung patency has yet to be explored. We hypothesized the occurrence of an expiratory diaphragmatic contraction directed at stabilizing peripheral airways and preventing or reducing cyclic expiratory lung collapse. Mild acute respiratory distress syndrome was induced in 10 anesthetized, spontaneously breathing pigs. Lung volume was decreased by lowering end-expiratory airway pressure in a stepwise manner. We recorded the diaphragmatic electric activity during expiration, dynamic computed tomographic scans, and respiratory mechanics. In five pigs, the same protocol was repeated during mechanical ventilation after muscle paralysis. Diaphragmatic electric activity during expiration increased by decreasing end-expiratory lung volume during spontaneous breathing. This enhanced the diaphragm muscle force, to a greater extent with lower lung volume, indicating a diaphragmatic electromechanical coupling during spontaneous expiration. In turn, the resulting diaphragmatic contraction delayed and reduced the expiratory collapse and increased lung aeration compared with mechanical ventilation with muscle paralysis and absence of diaphragmatic activity. The diaphragm is an important regulator of expiration. Its expiratory activity seems to preserve lung volume and to protect against lung collapse. The loss of diaphragmatic expiratory contraction during mechanical ventilation and muscle paralysis may be a contributing factor to unsuccessful respiratory support.

New Setting of Neurally Adjusted Ventilatory Assist during Noninvasive Ventilation through a Helmet

Compared to pneumatically controlled pressure support (PSP), neurally adjusted ventilatory assist (NAVA) was proved to improve patient-ventilator interactions, while not affecting comfort, diaphragm electrical activity (EAdi), and arterial blood gases (ABGs). This study compares neurally controlled pressure support (PSN) with PSP and NAVA, delivered through two different helmets, in hypoxemic patients receiving noninvasive ventilation for prevention of extubation failure. Fifteen patients underwent three (PSP, NAVA, and PSN) 30-min trials in random order with both helmets. Positive end-expiratory pressure was always set at 10 cm H2O. In PSP, the inspiratory support was set at 10 cm H2O above positive end-expiratory pressure. NAVA was adjusted to match peak EAdi (EAdipeak) during PSP. In PSN, the NAVA level was set at maximum matching the pressure delivered during PSP by limiting the upper pressure. The authors assessed patient comfort, EAdipeak, rates of pressurization (i.e., airway pressure-time product [PTP] of the first 300 and 500 ms after the initiation of patient effort, indexed to the ideal pressure-time products), and measured ABGs. PSN significantly increased comfort to (median [25 to 75% interquartile range]) 8 [7 to 8] and 9 [8 to 9] with standard and new helmets, respectively, as opposed to both PSP (5 [5 to 6] and 7 [6 to 7]) and NAVA (6 [5 to 7] and 7 [6 to 8]; P < 0.01 for all comparisons). Regardless of the interface, PSN also decreased EAdipeak (P < 0.01), while increasing PTP of the first 300 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.01) and PTP of the first 500 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.001). ABGs were not different among trials. When delivering noninvasive ventilation by helmet, compared to PSP and NAVA, PSN improves comfort and patient-ventilator interactions, while not ABGs. (Anesthesiology 2016; 125:1181-9).

Impact of feeding method on diaphragm electrical activity and central apnea in preterm infants (FEAdi study)

BackgroundIn preterm infants, it is unknown whether feeding affects neural breathing pattern. ObjectivesBy measuring the diaphragm electrical activity (Edi) waveform, we evaluated the effect of enteral feeding and compared the effects of feeding methods on neural breathing pattern and central apnea in very low birth weight preterm infants. MethodsIn a prospective, randomized, crossover study, ten non-ventilated preterm infants with birth weights<1250g and tolerating full feeds were randomized to either bolus feeding (BF) or slow infusion feeding (SF) over 90min, followed by crossover to the other method at the next feed. Edi was continuously measured by a feeding catheter with miniaturized sensors. Five 15-min epochs were chosen [Baseline (BL), first 15min and 90min after BF/SF started] for breath-by-breath analyses of neural breathing pattern, including Edi peak, Edi min (end-expiratory), neural inspiratory and expiratory times, neural respiratory rate, and central apnea. Primary outcome was change in Edi min with feed. Secondary outcomes include change in Edi peak, frequency and duration of central apnea with feeding. ResultsAlthough intrasubject coefficient of variation was not significantly different, individual responses to feeding and feeding method were variable. No significant difference in Edi timing, Edi min, Edi peak, or apnea was observed for the different epochs. ConclusionsIn this study cohort, neural breathing pattern does not appear to be consistently affected by enteral feeding or the feeding method. Compared with BF, SF does not appear to reduce the number or duration of apneas.

A randomized clinical trial of neurally adjusted ventilatory assist versus conventional weaning mode in patients with COPD and prolonged mechanical ventilation.

BackgroundPatient-ventilator asynchrony is a common problem in mechanically ventilated patients; the problem is especially obvious in COPD. Neutrally adjusted ventilatory assist (NAVA) can improve patient-ventilator asynchrony; however, the effect in COPD patients with prolonged mechanical ventilation is still unknown. The goals of this study are to evaluate the effect of NAVA and conventional weaning mode in patients with COPD during prolonged mechanical ventilation.MethodsThe study enrolled a total of 33 COPD patients with ventilator dependency for more than 21 days in the weaning center. A diaphragm electrical activity (Edi) catheter was inserted in patients within 24 hours after admission to the respiratory care center, and patients were randomly allocated to NAVA or conventional group. A spontaneous breathing trial was performed every 24 hours. The results correlated with the clinical parameters.ResultsThere were significantly higher asynchrony incidence rates in the whole group after using Edi catheter (before vs post-Edi catheter insertion =60.6% vs 87.9%, P<0.001). Asynchrony index: before vs post-Edi catheter insertion =7.4%±8.5% vs 13.2%±13.5%, P<0.01. Asynchrony incidence: NAVA vs conventional =0% vs 84.2%, P<0.001. Asynchrony index: NAVA vs conventional =0 vs 11.9±11.2 (breath %), P<0.001. The most common asynchrony events were ineffective trigger and delayed trigger.ConclusionCompared to conventional mode, NAVA mode can significantly enhance respiratory monitoring and improve patient-ventilator interaction in COPD patients with prolonged mechanical ventilation in respiratory care center.

Assisted Ventilation in Patients With Acute Respiratory Distress Syndrome

BACKGROUND: In patients with acute respiratory distress syndrome (ARDS), the use of assisted mechanical ventilation is a subject of debate. Assisted ventilation has benefits over controlled ventilation, such as preserved diaphragm function and improved oxygenation. Therefore, higher level of patient of ventilator assist may be preferable in ARDS. However, assisted modes may also increase the risk of high tidal volumes and lung-distending pressures. The current study aims to quantify how differences in freedom to control the ventilator affect lung-protective ventilation, breathing pattern variability, and patient-ventilator interaction. METHODS: Twelve patients with ARDS were ventilated in a randomized order with assist pressure control ventilation (PCV), pressure support ventilation (PSV), and neurally adjusted ventilatory assist (NAVA). Transpulmonary pressure, tidal volume, diaphragm electrical activity, and patient-ventilator interaction were measured. Respiratory variability was assessed using the coefficient of variation of tidal volume. RESULTS: During inspiration, transpulmonary pressure was slightly lower with NAVA (10.3 +/- 0.7, 11.2 +/- 0.7, and 9.4 +/- 0.7 cm H2O for PCV, PSV, and NAVA, respectively; P < 0.01). Tidal volume was similar between modes (6.6 [5.7 to 7.0], 6.4 [5.8 to 7.0], and 6.0 [5.6 to 7.3] ml/kg for PCV, PSV, and NAVA, respectively), but respiratory variability was higher with NAVA (8.0 [6.4 to 10.0], 7.1 [5.9 to 9.0], and 17.0 [12.0 to 36.1] % for PCV, PSV, and NAVA, respectively; P < 0.001). Patient-ventilator interaction improved with NAVA (6 [5 to 8] % error) compared with PCV (29 [14 to 52] % error) and PSV (12 [9 to 27] % error); P < 0.0001. CONCLUSION: In patients with mild-to-moderate ARDS, increasing freedom to control the ventilator maintains lung-protective ventilation in terms of tidal volume and lung-distending pressure, but it improves patient-ventilator interaction and preserves respiratory variability.

Impact of prolonged assisted ventilation on diaphragmatic efficiency: NAVA versus PSV.

BackgroundProlonged 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.MethodPatients 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.ResultsIn patients randomized to neurally adjusted ventilator assist, neuro-ventilatory efficiency increased from 27 ± 19 ml/μV at baseline to 62 ± 30 ml/μV at 48 hours (p <0.0001) and neuro-mechanical efficiency increased from 1 ± 0.6 to 2.6 ± 1.1 cmH2O/μV (p = 0.033). In patients randomized to pressure support ventilation, these did not change. Electrical activity of the diaphragm, neural inspiratory time, pressure time product of the diaphragm and variability of the breathing pattern were significantly higher in patients ventilated with neurally adjusted ventilatory assist. The asynchrony index was 9.48 [6.38– 21.73] in patients ventilated with pressure support ventilation and 5.39 [3.78– 8.36] in patients ventilated with neurally adjusted ventilatory assist (p = 0.04).ConclusionAfter prolonged controlled mechanical ventilation, neurally adjusted ventilator assist improves diaphragm efficiency whereas pressure support ventilation does not.Trial registrationClinicalTrials.gov study registration: NCT0247317, 06/11/2015.