Evaluation of the user-friendliness of seven new generation intensive care ventilators

Objective: To explore the user-friendliness and ergonomics of seven new generation intensive care ventilators. Design: Prospective task-performing study. Setting: Intensive care research laboratory, university hospital. Methods: Ten physicians experienced in mechanical ventilation, but without prior knowledge of the ventilators, were asked to perform eight specific tasks [turning the ventilator on; recognizing mode and parameters; recognizing and setting alarms; mode change; finding and activating the pre-oxygenation function; pressure support setting; stand-by; finding and activating non-invasive ventilation (NIV) mode]. The time needed for each task was compared to a reference time (by trained physiotherapist familiar with the devices). A time >180s was considered a task failure. Results: For each of the tests on the ventilators, all physicians' times were significantly higher than the reference time (P<0.001). A mean of 13±8 task failures (16%) was observed by the ventilator. The most frequently failed tasks were mode and parameter recognition, starting pressure support and finding the NIV mode. Least often failed tasks were turning on the pre-oxygenation function and alarm recognition and management. Overall, there was substantial heterogeneity between machines, some exhibiting better user-friendliness than others for certain tasks, but no ventilator was clearly better that the others on all points tested. Conclusions: The present study adds to the available literature outlining the ergonomic shortcomings of mechanical ventilators. These results suggest that closer ties between end-users and manufacturers should be promoted, at an early development phase of these machines, based on the scientific evaluation of the cognitive processes involved by users in the clinical settin

Performance of noninvasive ventilation modes on ICU ventilators during pressure support: abench model study

Objective: Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. Design and setting: Bench model study in an intensive care research laboratory of auniversity hospital. Methods: Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to alung model featuring aplastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. Results: On most ventilators leaks led to an increase in trigger delay and workload, adecrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. Conclusions: The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilato

Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated patients with chronic obstructive pulmonary disease

Objective: To evaluate the impact of helium-oxygen (He/O2) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support. Design and setting: Prospective crossover interventional study in the medical ICU of a university hospital. Patients and participants: Ten patients. Interventions: Sequential inhalation (30min each) of three gas mixtures: (a) air/O2, (b) He/O2 (c) air/O2, at constant FIO2 and level of pressure support. Measurements and results: Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO2 were 14±3cmH2O and 0.33±0.07 respectively. Compared to Air/O2, He/O2 reduced the number of ineffective breaths (4±5 vs. 9±5 breaths/min), intrinsic PEEP (3.1±2 vs. 4.8±2cmH2O), the magnitude of negative esophageal pressure swings (6.7±2 vs. 9.1±4.9cmH2O), pressure-time product (42±37 vs. 67±65cmH2Os−1min−1), and total WOB (11±3 vs. 18±10J/min). Elastic (6±1 vs. 10±6J/min) and resistive (5±1 vs. 9±4J/min) components of the WOB were decreased by He/O2. Conclusions: In intubated COPD patients ventilated with pressure support He/O2 reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O2 could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weanin

Automatic adjustment of pressure support by acomputer-driven knowledge-based system during noninvasive ventilation: afeasibility study

Objective: To evaluate the feasibility of using aknowledge-based system designed to automatically titrate pressure support (PS) to maintain the patient in a"respiratory comfort zone” during noninvasive ventilation (NIV) in patients with acute respiratory failure. Design and setting: Prospective crossover interventional study in an intensive care unit of auniversity hospital. Patients: Twenty patients. Interventions: After initial NIV setting and startup in conventional PS by the chest physiotherapist NIV was continued for 45 min with the automated PS activated. Measurements and results: During automated PS minute-volume was maintained constant while respiratory rate decreased significantly from its pre-NIV value (20 ± 3 vs. 25 ± 3 bpm). There was atrend towards aprogressive lowering of dyspnea. In hypercapnic patients PaCO2 decreased significantly from 61 ± 9 to 51 ± 2 mmHg, and pH increased significantly from 7.31 ± 0.05 to 7.35 ± 0.03. Automated PS was well tolerated. Two system malfunctions occurred prompting physiotherapist intervention. Conclusions: The results of this feasibility study suggest that the system can be used during NIV in patients with acute respiratory failure. Further studies should now determine whether it can improve patient-ventilator interaction and reduce caregiver workloa

Automatic adjustment of noninvasive pressure support with abilevel home ventilator in patients with acute respiratory failure: afeasibility study

Objective: To test the feasibility of applying noninvasive ventilation (NIV) using aprototype algorithm implemented in abilevel ventilation device designed to adjust pressure support (PS) to maintain aclinician-set alveolar ventilation in patients with acute respiratory failure after initial stabilization. Design and setting: Prospective crossover interventional study in an intensive care unit, university hospital. Patients: 19 patients receiving NIV for acute hypercapnic respiratory failure (13 men, 6 women; mean age 70 ± 11 years). Methods: The same bilevel ventilator was used with manually adjusted PS and with the automated algorithm (autoPS), set to maintain the same alveolar ventilation as in PS. Sequence (measurements at end of each period): (a) prior to initiating NIV (baseline 1); (b) 45 min with manually set PS; (c) 60 min without NIV; (d) 45 min with autoPS; (e) 60 min without NIV; (f) 45 min with manually set PS. Results: The magnitude of decrease in PaCO2 and increase in pH with autoPS was comparable to that of conventional PS, with the same alveolar ventilation and level of PS. No technical problem occurred in autoPS mode, and no NIV trial had to be discontinued because of patient discomfort. Conclusions: These results suggest that the alveolar ventilation based automatic control of PS during NIV with abilevel device is feasible and leads to beneficial effects in patients with acute respiratory failure comparable to those of manually set PS. Further studies should now explore the potential of this system over longer periods in patients with acute and chronic respiratory failur

Performance of noninvasive ventilation algorithms on ICU ventilators during pressure support: a clinical study

Objective: To evaluate the impact of noninvasive ventilation (NIV) algorithms available on intensive care unit ventilators on the incidence of patient-ventilator asynchrony in patients receiving NIV for acute respiratory failure. Design: Prospective multicenter randomized cross-over study. Setting: Intensive care units in three university hospitals. Methods: Patients consecutively admitted to the ICU and treated by NIV with an ICU ventilator were included. Airway pressure, flow and surface diaphragmatic electromyography were recorded continuously during two 30-min periods, with the NIV (NIV+) or without the NIV algorithm (NIV0). Asynchrony events, the asynchrony index (AI) and a specific asynchrony index influenced by leaks (AIleaks) were determined from tracing analysis. Results: Sixty-five patients were included. With and without the NIV algorithm, respectively, auto-triggering was present in 14 (22%) and 10 (15%) patients, ineffective breaths in 15 (23%) and 5 (8%) (p=0.004), late cycling in 11 (17%) and 5 (8%) (p=0.003), premature cycling in 22 (34%) and 21 (32%), and double triggering in 3 (5%) and 6 (9%). The mean number of asynchronies influenced by leaks was significantly reduced by the NIV algorithm (p<0.05). A significant correlation was found between the magnitude of leaks and AIleaks when the NIV algorithm was not activated (p=0.03). The global AI remained unchanged, mainly because on some ventilators with the NIV algorithm premature cycling occurs. Conclusion: In acute respiratory failure, NIV algorithms provided by ICU ventilators can reduce the incidence of asynchronies because of leaks, thus confirming bench test results, but some of these algorithms can generate premature cyclin

Patient-ventilator asynchrony during non-invasive ventilation for acute respiratory failure: a multicenter study

Objective : To determine the prevalence of patient-ventilator asynchrony in patients receiving non-invasive ventilation (NIV) for acute respiratory failure. Design : Prospective multicenter observation study. Setting : Intensive care units in three university hospitals. Methods: Patients consecutively admitted to ICU were included. NIV, performed with an ICU ventilator, was set by the clinician. Airway pressure, flow, and surface diaphragmatic electromyography were recorded continuously for 30min. Asynchrony events and the asynchrony index (AI) were determined from visual inspection of the recordings and clinical observation. Results: A total of 60 patients were included, 55% of whom were hypercapnic. Auto-triggering was present in 8 (13%) patients, double triggering in 9 (15%), ineffective breaths in 8 (13%), premature cycling 7 (12%) and late cycling in 14 (23%). An AI>10%, indicating severe asynchrony, was present in 26 patients (43%), whose median (25-75 IQR) AI was 26 (15-54%). A significant correlation was found between the magnitude of leaks and the number of ineffective breaths and severity of delayed cycling. Multivariate analysis indicated that the level of pressure support and the magnitude of leaks were weakly, albeit significantly, associated with an AI>10%. Patient comfort scale was higher in pts with an AI<10%. Conclusion: Patient-ventilator asynchrony is common in patients receiving NIV for acute respiratory failure. Our results suggest that leaks play a major role in generating patient-ventilator asynchrony and discomfort, and point the way to further research to determine if ventilator functions designed to cope with leaks can reduce asynchrony in the clinical settin

Neurally adjusted ventilatory assist improves patient-ventilator interaction

Purpose: To determine if, compared with pressure support (PS), neurally adjusted ventilatory assist (NAVA) reduces trigger delay, inspiratory time in excess, and the number of patient-ventilator asynchronies in intubated patients. Methods: Prospective interventional study in spontaneously breathing patients intubated for acute respiratory failure. Three consecutive periods of ventilation were applied: (1) PS1, (2) NAVA, (3) PS2. Airway pressure, flow, and transesophageal diaphragmatic electromyography were continuously recorded. Results: All results are reported as median (interquartile range, IQR). Twenty-two patients were included, 36.4% (8/22) having obstructive pulmonary disease. NAVA reduced trigger delay (ms): NAVA, 69 (57-85); PS1, 178 (139-245); PS2, 199 (135-256). NAVA improved expiratory synchrony: inspiratory time in excess (ms): NAVA, 126 (111-136); PS1, 204 (117-345); PS2, 220 (127-366). Total asynchrony events were reduced with NAVA (events/min): NAVA, 1.21 (0.54-3.36); PS1, 3.15 (1.18-6.40); PS2, 3.04 (1.22-5.31). The number of patients with asynchrony index (AI) >10% was reduced by 50% with NAVA. In contrast to PS, no ineffective effort or late cycling was observed with NAVA. There was less premature cycling with NAVA (events/min): NAVA, 0.00 (0.00-0.00); PS1, 0.14 (0.00-0.41); PS2, 0.00 (0.00-0.48). More double triggering was seen with NAVA, 0.78 (0.46-2.42); PS1, 0.00 (0.00-0.04); PS2, 0.00 (0.00-0.00). Conclusions: Compared with standard PS, NAVA can improve patient-ventilator synchrony in intubated spontaneously breathing intensive care patients. Further studies should aim to determine the clinical impact of this improved synchron

Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interaction during non-invasive ventilation delivered by face mask

Purpose: 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. Methods: 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'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. Results: The study included 13 patients, six with COPD, and two with mixed pulmonary disease. T d was reduced with NAVA: median 35ms (IQR 31-53ms) versus 181ms (122-208ms); 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: 1.0events/min (0.5-3.1events/min) versus 4.4events/min (0.9-12.1events/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. PaO2 and PaCO2 were not different between ventilatory modes. Conclusion: 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 absen

Bench testing of a new hyperbaric chamber ventilator at different atmospheric pressures

Purpose: Providing mechanical ventilation is challenging at supra-atmospheric pressure. The higher gas density increases resistance, reducing the flow delivered by the ventilator. A new hyperbaric ventilator (Siaretron IPER 1000) is said to compensate for these effects automatically. The aim of this bench test study was to validate the compensation, define its limits and provide details on the ventilator's output at varied atmospheric pressures. Methods: Experiments were conducted inside a multiplace hyperbaric chamber at 1, 2.2, 2.8 and 4 atmospheres absolute (ATA), with the ventilator connected to a test lung. Transducers were recalibrated at each ATA level. Various ventilator settings were tested in volume and pressure control modes. Measured tidal volumes were compared with theoretical predictions based on gas laws. Results: Results confirmed the ventilator's ability to provide compensation, but also identified its limits. The compensation range could be predicted and depended on the maximal flow attainable, decreasing linearly with increasing atmospheric pressure. With settings inside the range, tidal volumes approximated set values (mean error 10±5%). With settings outside the range, the volume was limited to the predicted maximal value calculated from maximal flow. A practical guide for clinicians is provided. Conclusion: The IPER 1000 ventilator attempted to deliver stable tidal volume by adjusting the opening of the inspiratory valve in proportion to atmospheric pressure. Adequate compensation was observed, albeit only within a predictable range, which can be reliably predicted for each setting and ATA level combination. Setting a tidal volume outside this range can result in an unwanted decrease in minute ventilatio