Monitoring of intratidal lung mechanics: a Graphical User Interface for a model-based decision support system for PEEP-titration in mechanical ventilation

Transparent decision support for mechanical ventilation using visualization of clinical preferences

Background

Systems aiding in selecting the correct settings for mechanical ventilation should visualize patient information at an appropriate level of complexity, so as to reduce information overload and to make reasoning behind advice transparent. Metaphor graphics have been applied to this effect, but these have largely been used to display diagnostic and physiologic information, rather than the clinical decision at hand. This paper describes how the conflicting goals of mechanical ventilation can be visualized and applied in making decisions. Data from previous studies are analyzed to assess whether visual patterns exist which may be of use to the clinical decision maker.

Materials and methods

The structure and screen visualizations of a commercial clinical decision support system (CDSS) are described, including the visualization of the conflicting goals of mechanical ventilation represented as a hexagon. Retrospective analysis is performed on 95 patients from 2 previous clinical studies applying the CDSS, to identify repeated patterns of hexagon symbols.

Results

Visual patterns were identified describing optimal ventilation, over and under ventilation and pressure support, and over oxygenation, with these patterns identified for both control and support modes of mechanical ventilation. Numerous clinical examples are presented for these patterns illustrating their potential interpretation at the bedside.

Conclusions

Visual patterns can be identified which describe the trade-offs required in mechanical ventilation. These may have potential to reduce information overload and help in simple and rapid identification of sub-optimal settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-021-00974-5.

Effect of individualized PEEP titration guided by intratidal compliance profile analysis on regional ventilation assessed by electrical impedance tomography - a randomized controlled trial

Background

The application of positive end-expiratory pressure (PEEP) may reduce dynamic strain during mechanical ventilation. Although numerous approaches for PEEP titration have been proposed, there is no accepted strategy for titrating optimal PEEP. By analyzing intratidal compliance profiles, PEEP may be individually titrated for patients.

Methods

After obtaining informed consent, 60 consecutive patients undergoing general anesthesia were randomly allocated to mechanical ventilation with PEEP 5 cmH₂O (control group) or PEEP individually titrated, guided by an analysis of the intratidal compliance profile (intervention group). The primary endpoint was the frequency of each nonlinear intratidal compliance (C_RS) profile of the respiratory system (horizontal, increasing, decreasing, and mixed). The secondary endpoints measured were respiratory mechanics, hemodynamic variables, and regional ventilation, which was assessed via electrical impedance tomography.

Results

The frequencies of the C_RS profiles were comparable between the groups. Besides PEEP [control: 5.0 (0.0), intervention: 5.8 (1.1) cmH₂O, p < 0.001], the respiratory and hemodynamic variables were comparable between the two groups. The compliance profile analysis showed no significant differences between the two groups. The loss of ventral and dorsal regional ventilation was higher in the control [ventral: 41.0 (16.3)%; dorsal: 25.9 (13.8)%] than in the intervention group [ventral: 29.3 (17.6)%; dorsal: 16.4 (12.7)%; p (ventral) = 0.039, p (dorsal) = 0.028].

Conclusions

Unfavorable compliance profiles indicating tidal derecruitment were found less often than in earlier studies. Individualized PEEP titration resulted in slightly higher PEEP. A slight global increase in aeration associated with this was indicated by regional gain and loss analysis. Differences in dorsal to ventral ventilation distribution were not found.

Trial registration

This clinical trial was registered at the German Register for Clinical Trials (DRKS00008924) on August 10, 2015.

Intraoperative compliance profiles and regional lung ventilation improve with increasing positive end-expiratory pressure

BACKGROUND

Anaesthesia and mechanical ventilation can lead to impaired lung. Intraoperative positive end-expiratory pressure (PEEP) should prevent intratidal recruitment/derecruitment without causing overdistension. The intratidal compliance profile indicates both unwanted phenomena. We hypothesized that a higher than usual PEEP improves the intratidal compliance and the regional lung ventilation of patients with healthy lungs.

METHODS

After ethics approval, 30 adult patients scheduled for limb surgery were investigated at PEEP 5, 7 and 9 cm H2 O during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (CRS ) and the intratidal volume-dependent CRS curve. The CRS curve indicated intratidal recruitment/derecruitment and/or overdistension. Regional ventilation was measured using electrical impedance tomography.

RESULTS

At PEEP 5, 7 and 9 cm H2 O, intratidal recruitment/derecruitment was observed in 92%, 84% and 46% (P < 0.05) of the patients respectively. Increasing PEEP was associated with recruitment in the dorsal regions of the lungs (P < 0.001). At PEEP 9 cm H2 O, lung overdistension was indicated in two patients. With PEEP levels up to 9 cm H2 O, no significant effects on haemodynamic variables were found.

CONCLUSION

We conclude that in most patients, the often applied PEEP of 5 cm H2 O is insufficient to prevent intratidal recruitment/derecruitment and that few patients show overdistension at high PEEP levels. To establish optimal pressure-volume relationships in the respiratory system, the analysis of the individual intratidal compliance profiles could be a means for individualized perioperative PEEP titration.

Intratidal recruitment/derecruitment persists at low and moderate positive end-expiratory pressure in paediatric patients

In paediatric patients positive end-expiratory pressure (PEEP) is traditionally set lower than in adults. We investigated whether moderately higher PEEP improves respiratory mechanics and regional ventilation. Therefore, 40 children were mechanically ventilated with PEEP 2 and 5cmH₂O. Volume-dependent compliance profiles were analysed as a measure of intratidal recruitment/derecruitment. Regional ventilation was assessed using electrical impedance tomography. Mean compliance was 17.9±9.9mLcmH₂O^-1 (PEEP 2cmH₂O), and 19.0±10.9mLcmH₂O^-1 (PEEP 5 cmH₂O, p<0.001). Strong intratidal recruitment/derecruitment occurred in 40% of children at PEEP 2 cmH₂O, and 36% at PEEP 5 cmH₂O. Children showing strong recruitment/derecruitment were 33 (PEEP 2 cmH₂0) and 20 (PEEP 5 cmH₂0) months younger than children showing moderate recruitment/derecruitment. A higher PEEP improved peripheral ventilation. In conclusion, mechanically ventilated paediatric patients undergo intratidal recruitment/derecruitment which occurs more prominently in younger than in older children. A PEEP of 5cmH₂O does not fully prevent intratidal recruitment/derecruitment but homogenizes regional ventilation in comparison to 2cmH₂O.

Pneumoperitoneum deteriorates intratidal respiratory system mechanics: an observational study in lung-healthy patients

BACKGROUND

Pneumoperitoneum during laparoscopic surgery leads to atelectasis and impairment of oxygenation. Positive end-expiratory pressure (PEEP) is supposed to counteract atelectasis. We hypothesized that the derecruiting effects of pneumoperitoneum would deteriorate the intratidal compliance profile in patients undergoing laparoscopic surgery.

METHODS

In 30 adult patients scheduled for surgery with pneumoperitoneum, respiratory variables were measured during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (C _RS) and the intratidal volume-dependent C _RS curve using the gliding-SLICE method. The C _RS curve was then classified in terms of indicating intratidal recruitment/derecruitment (increasing profile) and overdistension (decreasing profile). During the surgical interventions, the PEEP level was maintained nearly constant at 7 cm H₂O. Data are expressed as mean [confidence interval].

RESULTS

Baseline C _RS was 60 [54-67] mL cm H₂O^-1. Application of pneumoperitoneum decreased C _RS to 40 [37-43] mL cm H₂O^-1 which partially recovered to 54 [50-59] mL cm H₂O^-1 (P < 0.001) after removal but remained below the value measured before pneumoperitoneum (P < 0.001). Baseline compliance profiles indicated intratidal recruitment/derecruitment in 48 % patients. After induction of pneumoperitoneum, intratidal recruitment/derecruitment was indicated in 93 % patients (P < 0.01), and after removal intratidal recruitment/derecruitment was indicated in 59 % patients. Compliance profiles showing overdistension were not observed.

CONCLUSIONS

Analyses of the intratidal compliance profiles reveal that pneumoperitoneum during laparoscopic surgery causes intratidal recruitment/derecruitment which partly persists after its removal. The analysis of the intratidal volume-dependent C _RS profiles could be used to guide intraoperative PEEP adjustments during elevated intraabdominal pressure.

Simultaneous monitoring of intratidal compliance and resistance in mechanically ventilated piglets: A feasibility study in two different study groups

Compliance measures the force counteracting parenchymal lung distension. In mechanical ventilation, intratidal compliance-volume (C(V))-profiles therefore change depending on PEEP, tidal volume (VT), and underlying mechanical lung properties. Resistance counteracts gas flow through the airways. Due to anatomical linking between parenchyma and airways, intratidal resistance-volume (R(V))-profiles are hypothesised to change in a non-linear way as well. We analysed respiratory system mechanics in fifteen piglets with lavage-induced lung injury and nine healthy piglets ventilated at different PEEP/VT-settings. In healthy lungs, R(V)-profiles remained mostly constant and linear at all PEEP-settings whereas the shape of the C(V)-profiles showed an increase toward a maximum followed by a decrease (small PEEP) or volume-dependent decrease (large PEEP). In the lavage group, a large drop in resistance at small volumes and slow decrease toward larger volumes was found for small PEEP/VT-settings where C(V)-profiles revealed a volume-dependent increase (small PEEP) or a decrease (large PEEP and large VT). R(V)-profiles depend characteristically on PEEP, VT, and possibly whether lungs are healthy or not. Curved R(V)-profiles might indicate pathological changes in the underlying mechanical lung properties and/or might be a sign of derecruitment.