Effects of Varying Levels of Inspiratory Assistance with Pressure Support Ventilation and Neurally Adjusted Ventilatory Assist on Driving Pressure in Patients Recovering from Hypoxemic Respiratory Failure.

BACKGROUND: Driving pressure can be readily measured during assisted modes of ventilation such as pressure support ventilation (PSV) and neurally adjusted ventilatory assist (NAVA). The present prospective randomized crossover study aimed to assess the changes in driving pressure in response to variations in the level of assistance delivered by PSV vs NAVA. METHODS: 16 intubated adult patients, recovering from hypoxemic acute respiratory failure (ARF) and undergoing assisted ventilation, were randomly subjected to six 30-min-lasting trials. At baseline, PSV (PSV100) was set with the same regulation present at patient enrollment. The corresponding level of NAVA (NAVA100) was set to match the same inspiratory peak of airway pressure obtained in PSV100. Therefore, the level of assistance was reduced and increased by 50% in both ventilatory modes (PSV50, NAVA50; PSV150, NAVA150). At the end of each trial, driving pressure obtained in response to four short (2-3 s) end-expiratory and end-inspiratory occlusions was analyzed. RESULTS: Driving pressure at PSV50 (6.6 [6.1-7.8] cmH2O) was lower than that recorded at PSV100 (7.9 [7.2-9.1] cmH2O, P = 0.005) and PSV150 (9.9 [9.1-13.2] cmH2O, P < 0.0001). In NAVA, driving pressure at NAVA50 was reduced compared to NAVA150 (7.7 [5.1-8.1] cmH2O vs 8.3 [6.4-11.4] cmH2O, P = 0.013), whereas there were no changes between baseline and NAVA150 (8.5 [6.3-9.8] cmH2O vs 8.3 [6.4-11.4] cmH2O, P = 0.331, respectively). Driving pressure at PSV150 was higher than that observed in NAVA150 (P = 0.011). CONCLUSIONS: NAVA delivers better lung-protective ventilation compared to PSV in hypoxemic ARF patients. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: The present trial was prospectively registered at www.clinicatrials.gov (NCT03719365) on 24 October 2018.

Early extubation with immediate non-invasive ventilation versus standard weaning in intubated patients for coronavirus disease 2019: a retrospective multicenter study.

In patients intubated for hypoxemic acute respiratory failure (ARF) related to novel coronavirus disease (COVID-19), we retrospectively compared two weaning strategies, early extubation with immediate non-invasive ventilation (NIV) versus standard weaning encompassing spontaneous breathing trial (SBT), with respect to IMV duration (primary endpoint), extubation failures and reintubations, rate of tracheostomy, intensive care unit (ICU) length of stay and mortality (additional endpoints). All COVID-19 adult patients, intubated for hypoxemic ARF and subsequently extubated, were enrolled. Patients were included in two groups, early extubation followed by immediate NIV application, and conventionally weaning after passing SBT. 121 patients were enrolled and analyzed, 66 early extubated and 55 conventionally weaned after passing an SBT. IMV duration was 9 [6-11] days in early extubated patients versus 11 [6-15] days in standard weaning group (p = 0.034). Extubation failures [12 (18.2%) vs. 25 (45.5%), p = 0.002] and reintubations [12 (18.2%) vs. 22 (40.0%) p = 0.009] were fewer in early extubation compared to the standard weaning groups, respectively. Rate of tracheostomy, ICU mortality, and ICU length of stay were no different between groups. Compared to standard weaning, early extubation followed by immediate NIV shortened IMV duration and reduced the rate of extubation failure and reintubation.

Diaphragmatic Kinetics Assessment by Tissue Doppler Imaging and Extubation Outcome.

BACKGROUND: The assessment of diaphragmatic kinetics through tissue Doppler imaging (dTDI) was recently proposed as a means to describe diaphragmatic activity in both healthy individuals and intubated patients undergoing weaning from mechanical ventilation. Our primary aim was to investigate whether the diaphragmatic excursion velocity measured with dTDI at the end of a spontaneous breathing trial (SBT) was different in subjects successfully extubated versus those who passed the trial but exhibited extubation failure within 48 h after extubation. METHODS: We enrolled 100 adult subjects, all of whom had successfully passed a 30-min SBT conducted in CPAP of 5 cm H2O. In cases of extubation failure within 48 h after liberation from invasive mechanical ventilation, subjects were re-intubated or supported through noninvasive ventilation. dTDI was performed at the end of the SBT to assess excursion, velocity, and acceleration. RESULTS: Extubation was successful in 79 subjects, whereas it failed in 21 subjects. The median (interquartile range [IQR]) inspiratory peak excursion velocity (3.1 [IQR 2.0-4.3] vs 1.8 [1.3-2.6] cm/s, P < .001), mean velocity (1.6 [IQR 1.2-2.4] vs 1.1 [IQR 0.8-1.4] cm/s, P < .001), and acceleration (8.8 [IQR 5.0-17.8] vs 4.2 [IQR 2.4-8.0] cm/s2, P = .002) were all significantly higher in subjects who failed extubation compared with those who were successfully extubated. Similarly, the median expiratory peak relaxation velocity (2.6 [IQR 1.9-4.5] vs 1.8 [IQR 1.2-2.5] cm/s, P < .001), mean velocity (1.1 [IQR 0.7-1.7] vs 0.9 [IQR 0.6-1.0] cm/s, P = .002), and acceleration (11.2 [IQR 9.1-19.0] vs 7.1 [IQR 4.6-12.0] cm/s2, P = .004) were also higher in the subjects who failed extubation. CONCLUSIONS: In our setting, at the end of SBT, subjects who developed extubation failure within 48 h after extubation experienced a greater diaphragmatic activation compared with subjects who were successfully extubated. (ClinicalTrials.gov registration NCT03962322.).

Neurally adjusted ventilatory assist preserves cerebral blood flow velocity in patients recovering from acute brain injury.

Neurally adjusted ventilatory assist (NAVA) has never been applied in patients recovering from acute brain injury (ABI) because neural respiratory drive could be affected by intracranial disease with detrimental effects on cerebral blood flow (CBF) velocity. Our primary aim was to assess the impact of NAVA and pressure support ventilation (PSV) on CBF velocity. In fifteen adult patients recovering from ABI and undergoing invasive assisted ventilation, PSV and NAVA were applied over 30-min-lasting trials, in the following sequence: PSV1, NAVA, and PSV2. While PSV was set to deliver a tidal volume ranging between 6 and 8 ml kg-1 of predicted body weight, in NAVA the level of assistance was chosen to achieve the same inspiratory peak airway pressure as PSV. At the end of each trial, a sonographic evaluation of CBF mean velocity was bilaterally obtained on the middle cerebral artery and an arterial blood gas sample was taken for analysis. CBF mean velocity was 51.8 [41.9,75.2] cm  s-1 at baseline, 51.9 [43.4,71.0] cm s-1 in PSV1, 53.6 [40.7,67.7] cm s-1 in NAVA, and 49.5 [42.1,70.8] cm s-1 in PSV2 (p = 0.0514) on the left and 50.2 [38.0,77.7] cm s-1 at baseline, 47.8 [41.7,68.2] cm s-1 in PSV1, 53.9 [40.1,78.5] cm s-1 in NAVA, and 55.6 [35.9,74.1] cm s-1 in PSV2 (p = 0.8240) on the right side. No differences were detected for pH (p = 0.0551), arterial carbon dioxide tension (p = 0.8142), and oxygenation (p = 0.0928) over the entire study duration. NAVA and PSV preserved CBF velocity in patients recovering from ABI.Trial registration: The present trial was prospectively registered at www.clinicatrials.gov (NCT03721354) on October 18th, 2018.

Esophageal balloon calibration during Sigh: A physiologic, randomized, cross-over study.

PURPOSE: Optimal esophageal balloon filling volume (Vbest) depends on the intrathoracic pressure. During Sigh breath delivered by the ventilator machine, esophageal balloon is surrounded by elevated intrathoracic pressure that might require higher filling volume for accurate measure of tidal changes in esophageal pressure (Pes). The primary aim of our investigation was to evaluate and compare Vbest during volume controlled and pressure support breaths vs. Sigh breath. MATERIALS AND METHODS: Twenty adult patients requiring invasive volume-controlled ventilation (VCV) for hypoxemic acute respiratory failure were enrolled. After the insertion of a naso-gastric catheter equipped with 10 ml esophageal balloon, each patient underwent three 30-min trials as follows: VCV, pressure support ventilation (PSV), and PSV + Sigh. Sigh was added to PSV as 35 cmH2O pressure-controlled breath over 4 s, once per minute. PSV and PSV + Sigh were randomly applied and, at the end of each step, esophageal balloon calibration was performed. RESULTS: Vbest was higher for Sigh breath (4.5 [3.0-6.8] ml) compared to VCV (1.5 [1.0-2.9] ml, P = 0.0004) and PSV tidal breath (1.0 [0.5-2.4] ml, P < 0.0001). CONCLUSIONS: During Sigh breath, applying a calibrated approach for Pes assessment, a higher Vbest was required compared to VCV and PSV tidal breath.

Mechanical Ventilation Guided by Uncalibrated Esophageal Pressure May Be Potentially Harmful.

BACKGROUND: Esophageal balloon calibration was proposed in acute respiratory failure patients to improve esophageal pressure assessment. In a clinical setting characterized by a high variability of abdominal load and intrathoracic pressure (i.e., pelvic robotic surgery), the authors hypothesized that esophageal balloon calibration could improve esophageal pressure measurements. Accordingly, the authors assessed the impact of esophageal balloon calibration compared to conventional uncalibrated approach during pelvic robotic surgery. METHODS: In 30 adult patients, scheduled for elective pelvic robotic surgery, calibrated end-expiratory and end-inspiratory esophageal pressure, and the associated respiratory variations were obtained at baseline, after pneumoperitoneum-Trendelenburg application, and with positive end-expiratory pressure (PEEP) administration and compared to uncalibrated values measured at 4-ml filling volume, as per manufacturer recommendation. Data are expressed as median and [25th, 75th percentile]. RESULTS: Ninety calibrations were successfully performed. Chest wall elastance worsened with pneumoperitoneum-Trendelenburg and PEEP (19.0 [15.5, 24.6] and 16.7 [11.4, 21.7] cm H2O/l) compared to baseline (8.8 [6.3, 9.8] cm H2O/l; P < 0.0001 for both comparisons). End-expiratory and end-inspiratory calibrated esophageal pressure progressively increased from baseline (3.7 [2.2, 6.0] and 7.7 [5.9, 10.2] cm H2O) to pneumoperitoneum-Trendelenburg (6.2 [3.8, 10.2] and 16.1 [13.1, 20.6] cm H2O; P = 0.014 and P < 0.001) and PEEP (8.8 [7.7, 15.6] and 18.9 [16.3, 22.0] cm H2O; P < 0.0001 vs. baseline for both comparison; P < 0.001 and P = 0.002 vs. pneumoperitoneum-Trendelenburg) and, at each study step, they were persistently lower than uncalibrated esophageal pressure (P < 0.0001 for all comparisons). Overall, difference among uncalibrated and calibrated esophageal pressure was 5.1 [3.8, 8.4] cm H2O at end-expiration and 3.8 [3.0, 6.3] cm H2O at end-inspiration. Uncalibrated esophageal pressure swing was always lower than calibrated one (P < 0.0001 for all comparisons) with a difference of -1.0 [-1.8, -0.4] cm H2O. CONCLUSIONS: In a clinical setting with variable chest wall mechanics, uncalibrated measurements substantially overestimated absolute values and underestimated respiratory variations of esophageal pressure. Calibration could substantially improve mechanical ventilation guided by esophageal pressure.

Oesophageal balloon calibration during pressure support ventilation: a proof of concept study.

Oesophageal balloon calibration improves the oesophageal pressure (Pes) assessment during invasive controlled mechanical ventilation. The primary aim of the present investigation was to ascertain the feasibility of oesophageal balloon calibration during pressure support ventilation (PSV). Secondarily, the calibrated Pes (Pescal) was compared to uncalibrated one acquired at 4 ml-filling volume (PesV4), as per manufacturer recommendation. After a naso-gastric tube equipped with oesophageal balloon was correctly positioned in 21 adult patients undergoing invasive volume-controlled ventilation (VCV) for acute hypoxemic respiratory failure, the balloon was progressively inflated, applying a series of end-inspiratory and end-expiratory holds at each filling volume during VCV and PSV. Upon optimal balloon filling volume (Vbest) was identified, Pescal was computed by correcting the Pes measured at Vbest for the oesophageal wall pressure elicited at same filling volume. Finally, end-expiratory and end-inspiratory PesV4 were recorded too. A total of 42 calibrations, 21 per ventilatory mode, were performed. Vbest was 1.9 ± 1.6 ml in VCV and 1.7 ± 1.6 ml in PSV (p = 0.5217). PesV4 was overestimated compared to Pescal at end-expiration and end-inspiration (p <0.0001 for all comparisons) in both VCV (13.4 ± 3.4 cmH2O and 15.4 ± 3 cmH2O vs. 8.5 ± 2.9 cmH2O and 11.4 ± 3 cmH2O) and PSV (14.7 ± 4.2 cmH2O and 17 ± 3.9 cmH2O vs. 8.9 ± 3.4 cmH2O and 12.4 ± 3.9 cmH2O). In PSV, oesophageal balloon calibration is feasible and allows to obtain a reliable Pes assessment compared to uncalibrated approach.