Individualised optimisation of mechanical ventilation (MV) remains cumbersome in modern intensive care medicine. Computerised, model-based support systems could help in tailoring MV settings to the ...complex interactions between MV and the individual patient's pathophysiology. Therefore, we critically appraised the current literature on computational physiological models (CPMs) for individualised MV in the ICU with a focus on quality, availability, and clinical readiness.
A systematic literature search was conducted on 13 February 2023 in MEDLINE ALL, Embase, Scopus and Web of Science to identify original research articles describing CPMs for individualised MV in the ICU. The modelled physiological phenomena, clinical applications, and level of readiness were extracted. The quality of model design reporting and validation was assessed based on American Society of Mechanical Engineers (ASME) standards.
Out of 6,333 unique publications, 149 publications were included. CPMs emerged since the 1970s with increasing levels of readiness. A total of 131 articles (88%) modelled lung mechanics, mainly for lung-protective ventilation. Gas exchange (n = 38, 26%) and gas homeostasis (n = 36, 24%) models had mainly applications in controlling oxygenation and ventilation. Respiratory muscle function models for diaphragm-protective ventilation emerged recently (n = 3, 2%). Three randomised controlled trials were initiated, applying the Beacon and CURE Soft models for gas exchange and PEEP optimisation. Overall, model design and quality were reported unsatisfactory in 93% and 21% of the articles, respectively.
CPMs are advancing towards clinical application as an explainable tool to optimise individualised MV. To promote clinical application, dedicated standards for quality assessment and model reporting are essential. Trial registration number PROSPERO- CRD42022301715 . Registered 05 February, 2022.
Abstract Background Respiratory effort should be closely monitored in mechanically ventilated ICU patients to avoid both overassistance and underassistance. Surface electromyography of the diaphragm ...(sEMGdi) offers a continuous and non-invasive modality to assess respiratory effort based on neuromuscular coupling (NMCdi). The sEMGdi derived electrical activity of the diaphragm (sEAdi) is prone to distortion by crosstalk from other muscles including the heart, hindering its widespread use in clinical practice. We developed an advanced analysis as well as quality criteria for sEAdi waveforms and investigated the effects of clinically relevant levels of PEEP on non-invasive NMCdi. Methods NMCdi was derived by dividing end-expiratory occlusion pressure (Pocc) by sEAdi, based on three consecutive Pocc manoeuvres at four incremental (+ 2 cmH2O/step) PEEP levels in stable ICU patients on pressure support ventilation. Pocc and sEAdi quality was assessed by applying a novel, automated advanced signal analysis, based on tolerant and strict cut-off criteria, and excluding inadequate waveforms. The coefficient of variations (CoV) of NMCdi after basic manual and automated advanced quality assessment were evaluated, as well as the effect of an incremental PEEP trial on NMCdi. Results 593 manoeuvres were obtained from 42 PEEP trials in 17 ICU patients. Waveform exclusion was primarily based on low sEAdi signal-to-noise ratio (N tolerant = 155, 37%, N strict = 241, 51% waveforms excluded), irregular or abrupt cessation of Pocc (N tolerant = 145, 35%, N strict = 145, 31%), and high sEAdi area under the baseline (N tolerant = 94, 23%, N strict = 79, 17%). Strict automated assessment allowed to reduce CoV of NMCdi to 15% from 37% for basic quality assessment. As PEEP was increased, NMCdi decreased significantly by 4.9 percentage point per cmH 2 O. Conclusion Advanced signal analysis of both Pocc and sEAdi greatly facilitates automated and well-defined identification of high-quality waveforms. In the critically ill, this approach allowed to demonstrate a dynamic NMCdi (Pocc/sEAdi) decrease upon PEEP increments, emphasising that sEAdi-based assessment of respiratory effort should be related to PEEP dependent diaphragm function. This novel, non-invasive methodology forms an important methodological foundation for more robust, continuous, and comprehensive assessment of respiratory effort at the bedside.
Surface electromyography (sEMG) can be used to measure the electrical activity of the respiratory muscles. The possible applications of sEMG span from patients suffering from acute respiratory ...failure to patients receiving chronic home mechanical ventilation, to evaluate muscle function, titrate ventilatory support and guide treatment. However, sEMG is mainly used as a monitoring tool for research and its use in clinical practice is still limited-in part due to a lack of standardization and transparent reporting. During this round table meeting, recommendations on data acquisition, processing, interpretation, and potential clinical applications of respiratory sEMG were discussed. This paper informs the clinical researcher interested in respiratory muscle monitoring about the current state of the art on sEMG, knowledge gaps and potential future applications for patients with respiratory failure.
•Plasma bicarbonate increased in healthy subjects by ingesting sodium bicarbonate.•With increasing inspiratory CO2 pressure, breathing parameters increased.•The ratio ΔVE/ΔPetCO2 remained unchanged ...with increased plasma bicarbonate.•Respiratory drive and minute ventilation decreased with increased plasma bicarbonate.
Patients with acute respiratory failure may develop respiratory acidosis. Metabolic compensation by bicarbonate production or retention results in posthypercapnic alkalosis with an increased arterial bicarbonate concentration. The hypothesis of this study was that elevated plasma bicarbonate levels decrease respiratory drive and minute ventilation.
In an intervention study in 10 healthy subjects the ventilatory response using a hypercapnic ventilatory response (HCVR) test was assessed, before and after administration of high dose sodium bicarbonate. Total dose of sodiumbicarbonate was 1000 ml 8.4% in 3 days.
Plasma bicarbonate increased from 25.2 ± 2.2 to 29.2 ± 1.9 mmol/L. With increasing inspiratory CO2 pressure during the HCVR test, RR, Vt, Pdi, EAdi and VE increased. The clinical ratio ΔVE/ΔPetCO2 remained unchanged, but Pdi, EAdi and VE were significantly lower after bicarbonate administration for similar levels of inspired CO2.
This study demonstrates that in healthy subjects metabolic alkalosis decreases the neural respiratory drive and minute ventilation, as a response to inspiratory CO2.
Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work received financial support from the French Government as part of ...the “Investments of the Future” program managed by the National Research Agency (ANR)
Background
Smartwatches which support recording of a single-lead electrocardiogram (ECG) are increasingly being used worldwide, mainly for detection of atrial fibrillation. Recordings beyond the wrist are anecdotal as their reliability remains unknown.
Aim
This clinical validation study assessed the reliability of an Apple Watch (AW) to obtain frontal and precordial leads as compared with standard 12-lead ECGs in both healthy subjects and patients with underlying heart disease.
Methods
In 100 subjects (80 with ECG anomalies), a standard 12-lead ECG was performed, followed by AW recordings of the standard Einthoven leads (leads I, II, and III) and precordial leads V1, V3, and V6. Seven parameters (P, QRS, ST and T-wave amplitudes, PR, QRS, and QT intervals) were compared through a Bland-Altman analysis including bias (mean difference), absolute offset (mean absolute difference), and 95% limits of agreement.
Results
No significant differences were observed for any parameter across any lead, except for R-wave measured across precordial leads V1, V3, and V6 where significantly greater amplitudes were measured by the AW, (0.20 mV; 0.19mV; 0.49 mV respectively; p = 9x10-7; p = 7x10-4; p = 6x10-14, respectively), indicating overestimation by the AW. There were no significant differences in absolute offset or bias for any parameters of any leads (p > 0.05).
Conclusion
ECGs recorded with the AW on the wrist but also on other positions had comparable durations and amplitudes compared to standard 12-lead ECG. The AW can be used to record frontal and precordial leads, paving the way for broader clinical applications.
Abstract
Background
Expiratory muscle weakness leads to difficult ventilator weaning. Maintaining their activity with functional electrical stimulation (FES) may improve outcome. We studied ...feasibility of breath-synchronized expiratory population muscle FES in a mixed ICU population (“Holland study”) and pooled data with our previous work (“Australian study”) to estimate potential clinical effects in a larger group.
Methods
Holland:
Patients with a contractile response to FES received active or sham expiratory muscle FES (30 min, twice daily, 5 days/week until weaned). Main endpoints were feasibility (e.g., patient recruitment, treatment compliance, stimulation intensity) and safety.
Pooled:
Data on respiratory muscle thickness and ventilation duration from the Holland and Australian studies were combined (
N
= 40) in order to estimate potential effect size. Plasma cytokines (day 0, 3) were analyzed to study the effects of FES on systemic inflammation.
Results
Holland:
A total of 272 sessions were performed (active/sham: 169/103) in 20 patients (
N
= active/sham: 10/10) with a total treatment compliance rate of 91.1%. No FES-related serious adverse events were reported.
Pooled:
On day 3, there was a between-group difference (
N
= active/sham: 7/12) in total abdominal expiratory muscle thickness favoring the active group treatment difference (95% confidence interval); 2.25 (0.34, 4.16) mm,
P
= 0.02 but not on day 5. Plasma cytokine levels indicated that early FES did not induce systemic inflammation. Using a survival analysis approach for the total study population, median ventilation duration and ICU length of stay were 10 versus 52 (
P
= 0.07), and 12 versus 54 (
P
= 0.03) days for the active versus sham group. Median ventilation duration of patients that were successfully extubated was 8.5 5.6–12.2 versus 10.5 5.3–25.6 days (
P
= 0.60) for the active (
N
= 16) versus sham (
N
= 10) group, and median ICU length of stay was 10.5 8.0–14.5 versus 14.0 9.0–19.5 days (
P
= 0.36) for those active (
N
= 16) versus sham (
N
= 8) patients that were extubated and discharged alive from the ICU. During ICU stay, 3/20 patients died in the active group versus 8/20 in the sham group (
P
= 0.16).
Conclusion
Expiratory muscle FES is feasible in selected ICU patients and might be a promising technique within a respiratory muscle-protective ventilation strategy. The next step is to study the effects on weaning and ventilator liberation outcome.
Trial registration:
ClinicalTrials.gov, ID NCT03453944. Registered 05 March 2018—Retrospectively registered,
https://clinicaltrials.gov/ct2/show/NCT03453944
.
Evidence from animal experiments has shown that the hypothalamic paraventricular nucleus (PVN) plays a key role in regulating body weight and blood glucose levels. However, it is unclear whether ...neuron populations in the human PVN are involved in the development of type 2 diabetes mellitus (T2DM). To address this, we investigated the neuronal and glial populations in the PVN of 26 T2DM patients and 20 matched controls. Our findings revealed a significant reduction in oxytocin (Oxt) neuron density in the PVN of T2DM patients compared to controls, while other neuronal populations remained unchanged. This suggests that Oxt neurons may play a specific role in the pathophysiology of T2DM. Interestingly, the reduction in Oxt neurons was accompanied by a decreased melanocortinergic input in to the PVN as reflected by a reduction in alpha-MSH immunoreactivity. We also analysed two glial cell populations, as they are important for maintaining a healthy neural microenvironment. We found that microglial density, phagocytic capacity, and their proximity to neurons were not altered in T2DM patients, indicating that the loss of Oxt neurons is independent of changes in microglial immunity. However, we did observe a reduction in the number of astrocytes, which are crucial for providing trophic support to local neurons. Moreover, a specific subpopulation of astrocytes characterized by aquaporin 4 expression was overrepresented in T2DM patients. Since this subset of astrocytes is linked to the glymphatic system, their overrepresentation might point to alterations in the hypothalamic waste clearance system in T2DM. Our study shows selective loss of Oxt neurons in the PVN of T2DM individuals in association with astrocytic reduction and gliovascular remodelling. Therefore, hypothalamic Oxt neurons may represent a potential target for T2DM treatment modalities.
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