Specific Training Improves the Detection and Management of Patient-Ventilator Asynchrony

BACKGROUND

Patient-ventilator asynchrony is common in patients undergoing mechanical ventilation. The proportion of health-care professionals capable of identifying and effectively managing different types of patient-ventilator asynchronies is limited. A few studies have developed specific training programs, but they mainly focused on improving patient-ventilator asynchrony detection without assessing the ability of health-care professionals to determine the possible causes.

METHODS

We conducted a 36-h training program focused on patient-ventilator asynchrony detection and management for health-care professionals from 20 hospitals in Latin America and Spain. The training program included 6 h of a live online lesson during which 120 patient-ventilator asynchrony cases were presented. After the 6-h training lesson, health-care professionals were required to complete a 1-h training session per day for the subsequent 30 d. A 30-question assessment tool was developed and used to assess health-care professionals before training, immediately after the 6-h training lecture, and after the 30 d of training (1-month follow-up).

RESULTS

One hundred sixteen health-care professionals participated in the study. The median (interquartile range) of the total number of correct answers in the pre-training, post-training, and 1-month follow-up were significantly different (12 [8.75-15], 18 [13.75-22], and 18.5 [14-23], respectively). The percentages of correct answers also differed significantly between the time assessments. Study participants significantly improved their performance between pre-training and post-training (P < .001). This performance was maintained after a 1-month follow-up (P = .95) for the questions related to the detection, determination of cause, and management of patient-ventilator asynchrony.

CONCLUSIONS

A specific 36-h training program significantly improved the ability of health-care professionals to detect patient-ventilator asynchrony, determine the possible causes of patient-ventilator asynchrony, and properly manage different types of patient-ventilator asynchrony.

Hiccup-like Contractions in Mechanically Ventilated Patients: Individualized Treatment Guided by Transpulmonary Pressure

Hiccups-like contractions, including hiccups, respiratory myoclonus, and diaphragmatic tremor, refer to involuntary, spasmodic, and inspiratory muscle contractions. They have been repeatedly described in mechanically ventilated patients, especially those with central nervous damage. Nevertheless, their effects on patient-ventilator interaction are largely unknown, and even more overlooked is their contribution to lung and diaphragm injury. We describe, for the first time, how the management of hiccup-like contractions was individualized based on esophageal and transpulmonary pressure measurements in three mechanically ventilated patients. The necessity or not of intervention was determined by the effects of these contractions on arterial blood gases, patient-ventilator synchrony, and lung stress. In addition, esophageal pressure permitted the titration of ventilator settings in a patient with hypoxemia and atelectasis secondary to hiccups and in whom sedatives failed to eliminate the contractions and muscle relaxants were contraindicated. This report highlights the importance of esophageal pressure monitoring in the clinical decision making of hiccup-like contractions in mechanically ventilated 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.

METHODS

Fourteen anesthetized rats were studied (380-590 g) during control, resistive breathing, acute lung injury or CO₂ rebreathing. Positive pressure continuous neurally adjusted ventilatory assist (cNAVA^P+ ) was applied via intubation. Negative pressure cNAVA (cNAVA^P- ) was applied with the animal placed in a sealed box. In part 1, automatic stepwise increments in cNAVA level by 0.2 cmH₂ O/µV every 30 s was applied for cNAVA^P+ , cNAVA^P- , and a 50/50 combination of the two (cNAVA^P± ). In part 2: During 5-min ventilation with cNAVA^P+ or cNAVA^P- we measured circuit, box, and esophageal (Pes) pressure, EAdi, blood pressure, and arterial blood gases.

RESULTS

Part 1: During cNAVA^P+ , pressure in the circuit increased with increasing cNAVA levels, reaching a plateau, and similarly for cNAVA^P- , albeit reversed in sign. This was associated with downregulation of the EAdi. Pes swings became less negative with cNAVA^P+ but, in contrast, Pes swings were more negative during increasing cNAVA^P- levels. Increasing the cNAVA level during cNAVA^P± resulted in an intermediate response. Part 2: no significant differences were observed for box/circuit pressures, EAdi, blood pressure, or arterial blood gases. Pes swings during cNAVA^P- were significantly more negative than during cNAVA^P+ .

CONCLUSION

Negative pressure ventilation synchronized and proportional to the diaphragm activity is feasible in small animals.

Mechanical ventilation strategy for pulmonary rehabilitation based on patient-ventilator interaction

Mechanical ventilation is an effective medical means in the treatment of patients with critically ill, COVID-19 and other pulmonary diseases. During the mechanical ventilation and the weaning process, the conduct of pulmonary rehabilitation is essential for the patients to improve the spontaneous breathing ability and to avoid the weakness of respiratory muscles and other pulmonary functional trauma. However, inappropriate mechanical ventilation strategies for pulmonary rehabilitation often result in weaning difficulties and other ventilator complications. In this article, the mechanical ventilation strategies for pulmonary rehabilitation are studied based on the analysis of patient-ventilator interaction. A pneumatic model of the mechanical ventilation system is established to determine the mathematical relationship among the pressure, the volumetric flow, and the tidal volume. Each ventilation cycle is divided into four phases according to the different respiratory characteristics of patients, namely, the triggering phase, the inhalation phase, the switching phase, and the exhalation phase. The control parameters of the ventilator are adjusted by analyzing the interaction between the patient and the ventilator at different phases. A novel fuzzy control method of the ventilator support pressure is proposed in the pressure support ventilation mode. According to the fuzzy rules in this research, the plateau pressure can be obtained by the trigger sensitivity and the patient's inspiratory effort. An experiment prototype of the ventilator is established to verify the accuracy of the pneumatic model and the validity of the mechanical ventilation strategies proposed in this article. In addition, through the discussion of the patient-ventilator asynchrony, the strategies for mechanical ventilation can be adjusted accordingly. The results of this research are meaningful for the clinical operation of mechanical ventilation. Besides, these results provide a theoretical basis for the future research on the intelligent control of ventilator and the automation of weaning process.

Patient-Ventilator Interaction With Noninvasive Proportional Assist Ventilation in Subjects With COPD

BACKGROUND

To investigate patient-ventilator interaction during different levels of noninvasive proportional assist ventilation (PAV) compared with noninvasive pressure support ventilation (PSV).

METHODS

Fifteen subjects with severe COPD and hypercapnia were consecutively recruited. After the baseline assessment of unassisted spontaneous breathing, 3 levels of ventilatory support were applied. The proportional assist (PA) and pressure support (PS) levels were set by subject comfort. PA-, PS- or PA+, PS+ were set at 25% more or less of PA or PS (PA- = 75% PA, PA+ = 125% PA, PS- = 75% PS, PS+ = 125% PS). Each level lasted at least 20 min. To demonstrate the patient-ventilator interaction, the neural respiratory drive, respiratory muscle effort, flow signal, and airway pressure were simultaneously monitored.

RESULTS

The expiratory cycle delay (time between the termination of the diaphragm electromyogram [EMG_di] signal and the end of the inspiratory flow) progressively increased with increasing assist level in both modes. However, compared with PSV, the expiratory cycle delay was significantly longer in each assist level during noninvasive PAV. The runaway phenomenon was observed in PA+. The time between the peak EMG_di signal and the maximum value of the flow signal and the time difference between the peak EMG_di signal and the maximum value of inspiratory pressure were significantly increased with the increasing assist level of PAV.

CONCLUSIONS

The expiratory cycle delay of noninvasive PAV was significantly longer than that of noninvasive PSV in the subjects with COPD with respiratory failure. During the levels of PAV, the lag time between neural respiratory drive and airway pressurization was significantly increased and the "runaway" phenomenon may be observed. (ClinicalTrials.gov registration NCT01782768.).

Neurally adjusted ventilatory assist versus pressure support ventilation in patient-ventilator interaction and clinical outcomes: a meta-analysis of clinical trials

Background

The objective of this study was to conduct a meta-analysis comparing neurally adjusted ventilatory assist (NAVA) with pressure support ventilation (PSV) in adult ventilated patients with patient-ventilator interaction and clinical outcomes.

Methods

The PubMed, the Web of Science, Scopus, and Medline were searched for appropriate clinical trials (CTs) comparing NAVA with PSV for the adult ventilated patients. RevMan 5.3 was performed for comparing NAVA with PSV in asynchrony index (AI), ineffective efforts, auto-triggering, double asynchrony, premature asynchrony, breathing pattern (Peak airway pressure (Paw_peek), mean airway pressure (Paw_mean), tidal volume (V_T, mL/kg), minute volume (MV), respiratory muscle unloading (peak electricity of diaphragm (EAdi_peak), P 0.1, V_T/EAdi), clinical outcomes (ICU mortality, duration of ventilation days, ICU stay time, hospital stay time).

Results

Our meta-analysis included 12 studies involving a total of 331 adult ventilated patients, AI was significantly lower in NAVA group [mean difference (MD) -12.82, 95% confidence interval (CI): -21.20 to -4.44, I²=88%], and using subgroup analysis, grouped by mechanical ventilation, the results showed that NAVA also had lower AI than PSV (Mechanical ventilation, MD -9.52, 95% CI: -17.85 to -1.20, I²=87%), (Non-invasive ventilation (NIV), MD -24.55, 95% CI: -35.40 to -13.70, I²=0%). NAVA was significantly lower than the PSV in auto-triggering (MD -0.28, 95% CI: -0.51 to -0.05, I²=10%), and premature triggering (MD -2.49, 95% CI: -3.77 to -1.21, I²=29%). There were no significant differences in double triggering, ineffective efforts, breathing pattern (Paw_mean, Paw_peak, V_T, MV), and respiratory muscle unloading (EAdi_peak, P 0.1, V_T/EAdi). For clinical outcomes, NAVA was significantly lower than the PSV (MD -2.82, 95% CI: -5.55 to -0.08, I²=0%) in the duration of ventilation, but two groups did not show significant differences in ICU mortality, ICU stay time, and hospital stay time.

Conclusions

NAVA is more beneficial in patient-ventilator interaction than PSV, and could decrease the duration of ventilation.

Neurally-Adjusted Ventilatory Assist for Noninvasive Ventilation via a Helmet in Subjects With COPD Exacerbation: A Physiologic Study

BACKGROUND

In patients with COPD exacerbation, noninvasive ventilation (NIV) is strongly recommended. NIV is generally delivered by using patient triggered and flow-cycled pressure support through a face mask. A specific method to generate neurally-controlled pressure support has been shown to improve comfort and patient-ventilator interaction. In addition, the helmet interface was better tolerated by patients compared with a face mask. Herein, we compared neurally-controlled pressure support through a helmet with pressure support through a face mask with respect to subject comfort, breathing pattern, gas exchange, pressurization and triggering performance, and patient-ventilator synchrony.

METHODS

Two 30-min trials of NIV were randomly delivered to 10 subjects with COPD exacerbation redundant: (1) pressure support through a face mask with inspiratory pressure support of ≥8 cm H₂O to obtain a tidal volume of 6-8 mL/kg of ideal body weight; and (2) NAVA through a helmet, setting the neurally-adjusted ventilatory assist level at 15 cm H₂O/μV, with an upper airway pressure limit to obtain the same overall airway pressure applied during pressure support through a face mask. We assessed subject comfort, breathing frequency, respiratory drive, arterial blood gases, pressure-time product (PTP) of the first 300 ms and 500ms after initiation of subject effort, inspiratory trigger delay, and rate of asynchrony determined as the asynchrony index.

RESULTS

Median and interquartile range NAVA through a helmet improved comfort (7.0 [6.0-8.0]) compared with pressure support through a face mask (5.0 [4.7-5.2], P = .005). The breathing pattern was not different between the methods. Respiratory drive was slightly, although not significantly, reduced (P = .19) during NAVA through a helmet in comparison with pressure support through a face mask. Gas exchange was also not different between the trials. The PTP of the first 300 ms (P = .92) and PTP of the first 500 ms (P = .08) were not statistically different between trials, whereas triggering performance, patient-ventilator interaction, and synchrony were all improved by NAVA through a helmet compared with pressure support through a face mask.

CONCLUSIONS

In the subjects with COPD with exacerbation, NAVA through a helmet improved comfort, triggering performance, and patient-ventilator synchrony compared with pressure support through a face mask.

Neurally Adjusted Ventilatory Assist After Pediatric Cardiac Surgery: Clinical Experience and Impact on Ventilation Pressures

BACKGROUND

After pediatric cardiac surgery, ventilation with high airway pressures can be detrimental to right ventricular function and pulmonary blood flow. Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interactions, helping maintain spontaneous ventilation. This study reports our experience with the use of NAVA in children after a cardiac surgery. We hypothesize that using NAVA in this population is feasible and allows for lower ventilation pressures.

METHODS

We retrospectively studied all children ventilated with NAVA (invasively or noninvasively) after undergoing cardiac surgery between January 2013 and May 2015 in our pediatric intensive care unit. The number and duration of NAVA episodes were described. For the first period of invasive NAVA in each subject, detailed clinical and ventilator data in the 4 h before and after the start of NAVA were extracted.

RESULTS

33 postoperative courses were included in 28 subjects with a median age of 3 [interquartile range (IQR) 1-12] months. NAVA was used invasively in 27 courses for a total duration of 87 (IQR 15-334) h per course. Peak inspiratory pressures and mean airway pressures decreased significantly after the start of NAVA (mean differences of 5.8 cm H₂O (95% CI 4.1-7.5) and 2.0 cm H₂O (95% CI 1.2-2.8), respectively, P < .001 for both). There was no significant difference in vital signs or blood gas values. NAVA was used noninvasively in 14 subjects, over 79 (IQR 25-137) h.

CONCLUSIONS

NAVA could be used in pediatric subjects after cardiac surgery. The significant decrease in airway pressures observed after transition to NAVA could have a beneficial impact in this specific population, which should be investigated in future interventional studies.

Performance of Leak Compensation in All-Age ICU Ventilators During Volume-Targeted Neonatal Ventilation: A Lung Model Study

BACKGROUND

Volume-targeted ventilation is increasingly used in low birthweight infants because of the potential for reducing volutrauma and avoiding hypocapnea. However, it is not known what level of air leak is acceptable during neonatal volume-targeted ventilation when leak compensation is activated concurrently.

METHODS

Four ICU ventilators (Servo-i, PB980, V500, and Avea) were compared in available invasive volume-targeted ventilation modes (pressure control continuous spontaneous ventilation [PC-CSV] and pressure control continuous mandatory ventilation [PC-CMV]). The Servo-i and PB980 were tested with (+) and without (-) their proximal flow sensor. The V500 and Avea were tested with their proximal flow sensor as indicated by their manufacturers. An ASL 5000 lung model was used to simulate 4 neonatal scenarios (body weight 0.5, 1, 2, and 4 kg). The ASL 5000 was ventilated via an endotracheal tube with 3 different leaks. Two minutes of data were collected after each change in leak level, and the asynchrony index was calculated. Tidal volume (V_T) before and after the change in leak was assessed.

RESULTS

The differences in delivered V_T between before and after the change in leak were within ±5% in all scenarios with the PB980 (-/+) and V500. With the Servo-i (-/+), baseline V_T was ≥10% greater than set V_T during PC-CSV, and delivered V_T markedly changed with leak. The Avea demonstrated persistent high V_T in all leak scenarios. Across all ventilators, the median asynchrony index was 1% (interquartile range 0-27%) in PC-CSV and 1.8% (0-45%) in PC-CMV. The median asynchrony index was significantly higher in the Servo-i (-/+) than in the PB980 (-/+) and V500 in 1 and 2 kg scenarios during PC-CSV and PC-CMV.

CONCLUSIONS

The PB980 and V500 were the only ventilators to acclimate to all leak scenarios and achieve targeted V_T. Further clinical investigation is needed to validate the use of leak compensation during neonatal volume-targeted ventilation.

Physiological Significance of Well-tolerated Inspiratory Pressure to Chronic Obstructive Pulmonary Disease Patient with Hypercapnia During Noninvasive Pressure Support Ventilation

The inspiratory pressure is often set by tolerance of chronic obstructive pulmonary disease (COPD) patient during noninvasive pressure support ventilation (PSV). However, physiological effects of this setting remain unclear. This study was undertaken to assess the physiological effect of highest tolerated assist level on COPD patient.  The baseline inspiratory pressure (PS) was titrated by tolerance in 15 severe COPD patients with hypercapnia during acute exacerbation. In addition to the baseline PS, an additional decrease by 25% (PS- = 75% PS) or increase by 25% (PS+ = 125% PS) of PS was applied to the patients. Each level lasted at least 20 minutes. Respiratory rate (RR), tidal volume (Vt), inspiratory effort (PTP_pesin/min), and neuro-ventilatory coupling (VE/RMS%) were measured. Asynchrony Index (AI) was calculated.  The Vt and VE/RMS% were significantly increased by PS level (Vt: 561 ± 102 ml, VE/RMS%: 1.06 ± 0.42 L/%, comfort score: 7.5 ± 1.1). The inspiratory muscles were sufficiently unloaded (PTP_pesin/min 56.67 ± 32.71 cmH₂O.S/min). In comparison with PS, PS+ resulted in a further increase in Vt, VE/RMS% and AI (P < 0.01), with no further reduction in neural drive (RMS) and respiratory muscle activity (P > 0.05).  Increasing inspiratory pressure significantly enhances the VE/RMS% and Vt. However, the inspiratory pressure higher than COPD patient's most tolerated level cannot lead to further reduction in respiratory muscle load and RMS, but more asynchrony events. Physiological data can monitor the patient's responses and the ventilator-patient interaction, which may provide objective criterion to ventilator setting.

Neurally adjusted ventilator assist (NAVA) reduces asynchrony during non-invasive ventilation for severe bronchiolitis

BACKGROUND

To determine the prevalence of main inspiratory asynchrony events during non-invasive intermittent positive-pressure ventilation (NIV) for severe bronchiolitis. Ventilator response time and asynchrony were compared in neurally adjusted ventilator assist (NAVA) and in pressure assist/control (PAC) modes.

METHODS

This prospective physiological study was performed in a university hospital's paediatric intensive care unit and included 11 children (aged 35.2 ± 23 days) with respiratory syncytial virus bronchiolitis with failure of nCPAP. Patients received NIV for 2 hr in PAC mode followed by 2 hr in NAVA mode. Electrical activity of the diaphragm and pressure curves were recorded for 10 min. Trigger delay, main asynchronies (auto-triggering, double triggering, or non-triggered breaths) were analyzed, and the asynchrony index was calculated for each period.

RESULTS

The asynchrony index was lower during NAVA than during PAC (3 ± 3% vs. 38 ± 21%, P < 0.0001), and the trigger delay was shorter (43.9 ± 7.2 vs. 116.0 ± 38.9 ms, P < 0.0001). Ineffective efforts were significantly less frequent in NAVA mode (0.54 ± 1.5 vs. 21.8 ± 16.5 events/min, P = 0.01). Patient respiratory rates were similar, but the ventilator rate was higher in NAVA than in PAC mode (59.5 ± 17.9 vs. 49.8 ± 8.5/min, P = 0.03). The TcPCO2 baselines values (64 ± 12 mmHg vs. 62 ± 9 mmHg during NAVA, P = 0.30) were the same and their evolution over the 2 hr study period (-6 ± 10 mmHg vs. -12 ± 17 mmHg during NAVA, P = 0.36) did not differ.

CONCLUSION

Patient-ventilator inspiratory asynchronies and trigger delay were dramatically lower in NAVA mode than in PAC mode during NIV in infants with severe bronchiolitis.

A bench study of 2 ventilator circuits during helmet noninvasive ventilation

OBJECTIVE

To compare helmet noninvasive ventilation (NIV), in terms of patient-ventilator interaction and performance, using 2 different circuits for connection: a double tube circuit (with one inspiratory and one expiratory line) and a standard circuit (a Y-piece connected only to one side of the helmet, closing the other side).

METHODS

A manikin, connected to a test lung set at 2 breathing frequencies (20 and 30 breaths/min), was ventilated in pressure support ventilation (PSV) mode with 2 different settings, randomly applied, of the ratio of pressurization time to expiratory trigger time (T(press)/T(exp-trigger)) 50%/25%, default setting, and T(press)/T(exp-trigger) 80%/60%, fast setting, through a helmet. The helmet was connected to the ventilator randomly with the double and the standard circuit. We measured inspiratory trigger delay (T(insp-delay)), expiratory trigger delay (T(exp-delay)), T(press)), time of synchrony (T(synch)), trigger pressure drop, inspiratory pressure-time product (PTP), PTP at 300 ms and 500 ms, and PTP at 500 ms expressed as percentage of an ideal PTP500 (PTP500 index).

RESULTS

At both breathing frequencies and ventilator settings, helmet NIV with the double tube circuit showed better patient-ventilator interaction, with shorter T(insp-delay), T(exp-delay), and T(press); longer T(synch); and higher PTP300, PTP500, and PTP500 index (all P < .01).

CONCLUSIONS

The double tube circuit had significantly better patient-ventilator interaction and a lower rate of wasted effort at 30 breaths/min.