Advice

Clinical and technical evidence

Clinical and technical evidence

A literature search was carried out for this briefing in accordance with the interim process and methods statement. This briefing includes the most relevant or best available published evidence relating to the clinical effectiveness of the technology. Further information about how the evidence for this briefing was selected is available on request by contacting mibs@nice.org.uk.

Published evidence

There are a large number of studies on electrical impedance tomography (EIT) and many include data from PulmoVista 500. This briefing summarises 6 recent studies to evaluate PulmoVista 500 in patients having mechanical ventilation.

The studies are 1 cohort study with a historical control group, 1 cross-over study and 4 observational studies. There were 238 people included in these studies. A systematic review (Kobylianskii et al. 2016) investigated the validation and application of EIT in people having mechanical ventilation. Data from multiple EIT devices, including PulmoVista 500, were included in the review. The studies of PulmoVista were not analysed independently from the studies of other EIT devices.

Table 2 summarises the clinical evidence as well as its strengths and limitations.

Overall assessment of the evidence

The evidence base addresses the safety and feasibility of using the technology during ventilatory support. The studies report the relationship between weaning off ventilation support or short breathing test outcome and surrogate measures of pulmonary function, measured by PulmoVista 500. These include end-expiratory lung impedance, tidal volume and inhomogeneity index. The evidence base would benefit from randomised controlled trials comparing the clinical outcomes of the technology with current NHS standard care. Blinding is not possible in this evidence base because of the visual differences between this technology and any comparator. The sample sizes are small and because of the lack of power calculations it is unclear if the studies are powered for analyses, including subgroup analyses. There are limited data relating to systematic benefits such as incidence of ventilatory-induced lung injury and length of hospital admission.

Table 2 Summary of selected studies

Longhini et al. (2019)

Study size, design and location

Multicentre observational study of 78 patients having invasive ventilation. PulmoVista 500 recordings were taken at various time points during SBT. To establish clinical relevance the population was divided into subgroups determined by successful and failed SBT and successful and failed extubation.

Italy.

Intervention and comparator(s)

PulmoVista 500.

No comparator.

Key outcomes

Compared with SBT successes (n=61), SBT failure (n=17) showed greater reduction in change from baseline in end-expiratory lung impedance immediately after the test (p=0.003) and at the end of the test (p=0.005). SBT failure also had significantly higher inhomogeneity at all 3 time points (baseline: p=0.002; start of test, p=0.003; end of test, p=0.005) Respiratory rate to tidal volume ratio is significantly higher in the SBT failure group at the start of the test and the end of the test (both p<0.001) but not at baseline. Across all outcome measures there were no significant differences between extubation successes (n=39) and failures (n=22).

Strengths and limitations

The study is a multicentre study and analyses were completed at a single site by an investigator blinded to SBT outcomes. The study shows the potential to use the technology clinically but does not evaluate its clinical effectiveness. Outcome measures are clinically relevant. The sample size is relatively large but the subgroups analysed are inconsistent sizes. No power analyses were done. A co-author of the study has received grants and lab equipment from the company.

Zhao et al. (2019)

Study size, design and location

Study of 55 people with severe ARDS comparing the prospective use of PulmoVista 500 to guide PEEP titration with a historical cohort of routine methods.

Taiwan.

Intervention and comparator(s)

PulmoVista 500-guided PEEP titration.

Ventilator embedded pressure loop-guided PEEP.

Key outcomes

Compared with the control group, the PulmoVista 500 group had significantly higher PEEP values (13.6±3.6 cmH2O and 17.6±3.6 cmH2O, respectively; p=0.01), respiratory system compliance (20.4±5.3 ml/cmH2O and 25.9±5.9 ml/cmH2O, respectively; p=0.01) and lower driving pressure (19.1±3.7 cmH2O and 15.1±3.1 cmH2O, respectively; p=0.01). There were no statistically significant differences in hospital survival rate or weaning success between the 2 groups (p=0.18 for both).

Strengths and limitations

The study compares the technology with routine measures and reports clinically and systematically relevant outcome measures. The study was not randomised and demographics between groups different significantly. The experimental group was significantly younger (p=0.05) with a higher plateau pressure (p=0.01). First author receives a consultancy fee from the company.

Bickenbach et al. (2017)

Study size, design and location

An observational study using PulmoVista 500 to predict failure of spontaneous breathing test in 31 people with prolonged weaning.

Germany.

Intervention and comparator(s)

PulmoVista 500.

No comparator.

Key outcomes

The global inhomogeneity index calculated using PulmoVista 500 was significantly higher during the SBT (t1) compared with early measures during pressure support ventilation (t0; 81.5±62.5 and 59.3±46.1, respectively; p=0.001). Statistically decreased measures in tidal impedance variation (72%; p=0.001) and changes in end-expiratory lung impedance (−65%; p=0.002) were recorded at t1 compared with t0. Assuming a PulmoVista 500 global inhomogeneity cut off value of higher than 40, ROC analyses reported sensitivity of 85% and specificity of 50% for predicting increased future tidal volume.

Strengths and limitations

The study shows the potential clinical application of the technology. The study is limited because of the lack of comparator arm. Differences in patient demographics were not tested statistically. This study looks specifically at people with prolonged weaning, limiting its generalisability to all people having ventilatory support. The study does not report power calculations.

Eronia et al. (2017)

Study size, design and location

An observational study investigating PulmoVista 500 for PEEP selection in 16 hypoxemic people.

Italy.

Intervention and comparator(s)

PulmoVista 500.

No comparator.

Key outcomes

The procedure was feasible in 87% of people. The PEEP selection guided by PulmoVista 500 was higher than the ARDS network proposition (13±3 cmH20 and 9±2 cmH20, respectively; p=0.001). During the PulmoVista 500 phase driving pressure reduced and PaO2/FiO2 ratio improved. However, these findings were not statistically significant (p=0.035 and p=0.121, respectively). Recruited volume correlated with the decrease in driving pressure (R=0.26; p=0.36).

Strengths and limitations

The study reports relevant clinical measures and compares the PEEP guided by PulmoVista 500 with the measures recorded whilst PEEP was set using ARDS network. The selection of PEEP using ARDS network is consistent with UK methods of PEEP selection. The sample size was small, and no power calculations were reported. There was a higher percentage of male subjects. Only descriptive statistics were used to report differences in the population demographics. A co-author receives fees from the company for lecturing and consulting, this author was not involved in data collection or analyses.

Zhao et al. (2017)

Study size, design and location

An observational study to investigate the correlation between regional ventilation measured using PulmoVista 500 and weaning outcomes in 30 people with prolonged mechanical ventilation.

Taiwan.

Intervention and comparator(s)

PulmoVista 500.

No comparator.

Key outcomes

Tidal volume correlated significantly with tidal variation of impedance, measured using PulmoVista 500 (r2=0.80±0.18; p<0.001). Higher ventilatory support levels resulted in higher end-expiratory lung impedance (p<0.05). Patients that exhibited redistributed ventilation to dorsal regions with lower support rates (n=13) had a higher weaning success rate (p<0.05) compared with those that didn't (n=17). They also needed significantly fewer days of SBT for weaning (13.1±4 days and 20.9±11.2 days respectively; p=0.05).

Strengths and limitations

The study repeated the measures across varying support levels to establish any relationship. However, the population was divided into 2 groups; people having automatic tube compensation ventilatory support (n=15) and another group having external continuous positive airway pressure (n=15), limiting the power of the statistical analyses. These groups may also confound findings reported on the whole population. The study does not report power calculations. Demographic data is reported using only descriptive statistics. The first author receives a consultancy fee from the company.

Mauri et al. (2014)

Study size, design and location

Randomised crossover study investigating PulmoVista 500 measured ventilation compared with helium dilation technique measures of recruitment and ventilation in 18 people with critical illness.

Italy.

Intervention and comparator(s)

PulmoVista 500.

Helium dilation technique.

Key outcomes

When PEEP was higher changes in EELV and recruitment measured using helium dilation technique (p<0.001 for both) and PulmoVista 500 (p<0.001 for both). A significant correlation was reported between PulmoVista 500 measures and helium technique measures of EELV (r=0.84; p<0.001) and recruitment estimated (r=0.78; p<0.001). High PEEP resulted in decreased compliance of non-dependent lung regions (p<0.001) and increased tidal volume in dependent lung regions (p<0.001). Increase in dependent lung region tidal volume correlated with PulmoVista 500 measures of recruitment (r=0.58; p=0.01). Patients with higher percentage of potentially recruitable lung had more severe baseline lung injury (p<0.05) and increased length of stay (p=0.01).

Strengths and limitations

This study compares the PulmoVista 500 with a comparative lung-monitoring technique. The study was well designed with a randomly assigned crossover of measures. Outcome measures are clinically and systematically relevant. The abstract presented does not report patient demographic data, method of randomisation or details regarding statistical analyses.

Abbreviations: ARDS, acute respiratory distress syndrome; EELV, end-expiratory lung volume; PEEP, positive end-expiratory pressure; ROC, receiver operating characteristic; SBT, spontaneous breathing test.

Recent and ongoing studies