Respiratory challenges and ventilatory management in different types of acute brain-injured patients

Beyond the Lungs: Extrapulmonary Effects of Non-Invasive and Invasive Ventilation Strategies

Background/Objectives: Non-invasive respiratory support and invasive mechanical ventilation are critical interventions that can induce significant changes not only in the lungs but also in extra-pulmonary organs, which are often overlooked. Understanding the extra-pulmonary effects of non-invasive respiratory support and invasive mechanical ventilation is crucial since it can help prevent or mitigate complications and improve outcomes. This narrative review explores these consequences in detail and highlights areas that require further research. Main Text: Non-invasive respiratory support and invasive mechanical ventilation can significantly impact various extrapulmonary organs. For instance, some ventilation strategies can affect venous return from the brain, which may lead to neurological sequelae. In the heart, regardless of the chosen ventilation method, increased intrathoracic pressure (ITP) can also reduce venous return to the heart. This reduction in turn can decrease cardiac output, resulting in hypotension and diminished perfusion of vital organs. Conversely, in certain situations, both ventilation strategies may enhance cardiac function by decreasing the work of breathing and lowering oxygen consumption. In the kidneys, these ventilation methods can impair renal perfusion and function through various mechanisms, including hemodynamic changes and the release of stress hormones. Such alterations can lead to acute kidney injury or exacerbate pre-existing renal conditions. Conclusions: This review emphasizes the critical importance of understanding the extensive mechanisms by which non-invasive respiratory support and invasive mechanical ventilation affect extrapulmonary organs, including neurological, cardiovascular, and renal systems. Such knowledge is essential for optimizing patient care and improving outcomes in critical care settings.

Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxic respiratory failure caused by diffuse lung inflammation and edema. ARDS can be precipitated by intrapulmonary factors or extrapulmonary factors, which can lead to severe hypoxemia. Patients suffering from ARDS have high mortality rates, including a 28-day mortality rate of 34.8% and an overall in-hospital mortality rate of 40.0%. The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of systemic inflammation and coagulation, including the respiratory system, circulatory system, and immune system. In general, the treatment of inflammatory injuries is a coordinated process that involves the downregulation of proinflammatory pathways and the upregulation of anti-inflammatory pathways. Given the complexity of the underlying disease, treatment needs to be tailored to the problem. Hence, we discuss the pathogenesis and treatment methods of affected organs, including 2019 coronavirus disease (COVID-19)-related pneumonia, drowning, trauma, blood transfusion, severe acute pancreatitis, and sepsis. This review is intended to provide a new perspective concerning ARDS and offer novel insight into future therapeutic interventions.

Management of severe traumatic brain injury in pediatric patients: an evidence-based approach

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. The decision-making process in the management of severe TBI must be based on the best available evidence to minimize the occurrence of secondary brain injuries. However, healthcare approaches to managing TBI patients exhibit considerable variation.

METHODS

Over an 18-month period, a multidisciplinary panel consisting of medical doctors, physiotherapists, nutritional therapists, and nurses performed a comprehensive review on various subtopics concerning TBI. The panel identified primary questions to be addressed using the Population, Intervention, Control, and Outcome (PICO) format and applied the Evidence to Decision (EtD) framework criteria for evaluating interventions. Subsequently, the panel formulated recommendations for the management of severe TBI in children.

RESULTS

Fourteen evidence-based recommendations have been devised for the management of severe TBI in children, covering nine topics, including imaging studies, neuromonitoring, prophylactic anticonvulsant use, hyperosmolar therapy, sedation and analgesia, mechanical ventilation strategies, nutritional therapy, blood transfusion, and decompressive craniectomy. For each topic, the panel provided clinical recommendations and identified research priorities.

CONCLUSIONS

This review offers evidence-based strategies aimed to guide practitioners in the care of children who suffer from severe TBI.

Ventilation practices in acute brain injured patients and association with outcomes: the VENTIBRAIN multicenter observational study

PURPOSE

Current mechanical ventilation practices for patients with acute brain injury (ABI) are poorly defined. This study aimed to describe ventilator settings/parameters used in intensive care units (ICUs) and evaluate their association with clinical outcomes in these patients.

METHODS

An international, prospective, multicenter, observational study was conducted across 74 ICUs in 26 countries, including adult patients with ABI (e.g., traumatic brain injury, intracranial hemorrhage, subarachnoid hemorrhage, and acute ischemic stroke), who required ICU admission and invasive mechanical ventilation. Ventilatory settings were recorded daily during the first week and on days 10 and 14. ICU and 6-months mortality and 6-months neurological outcome were evaluated.

RESULTS

On admission, 2095 recruited patients (median age 58 [interquartile range 45-70] years, 66.1% male) had a median plateau pressure (Pplat) of 15 (13-18) cmH20, tidal volume/predicted body weight 6.5 (5.7-7.3) mL/Kg, driving pressure 9 (7-12) cmH20, and positive end-expiratory pressure 5 (5-8) cmH20, with no modifications in case of increased intracranial pressure (> 20 mmHg). Significant differences in practices were observed across different countries. The majority of these ventilatory settings were associated with ICU mortality, with the highest hazard ratio (HR) for Pplat (odds ratio 1.50; 95% confidence interval, CI: 1.27-1.78). The results demonstrated consistent association with 6-month mortality; less clear association was observed for neurological outcome.

CONCLUSIONS

Protective ventilation strategies are commonly used in ABI patients but with high variability across different countries. Ventilator settings during ICU stay were associated with an increased risk of ICU and 6-month mortality, but not an unfavorable neurological outcome.

Positive end-expiratory pressure increases intracranial pressure but not pressure reactivity index in supine and prone positions: a porcine model study

Introduction

Positive end-expiratory pressure (PEEP) and prone positioning can improve gas exchange by promoting uniform lung aeration. However, elevated ventilation pressures may increase intracranial pressure (ICP) and disrupt cerebral autoregulation. This study investigated the effects of PEEP on ICP and cerebral autoregulation in a porcine model with healthy lungs and normal ICP, comparing prone and supine positions. Cerebral autoregulation was assessed through cerebrovascular reactivity using the pressure reactivity index (PRx). We also explored whether other baseline variables influenced potential variances in ICP and PRx.

Methodology

Twelve anesthetized pigs were randomized to begin in either supine or prone position, across PEEP of 5, 10, 15, and 20 cmH2O. Continuous monitoring included esophageal pressure to calculate end-inspiratory and end-expiratory transpulmonary pressures. The ICM+® software (University of Cambridge Enterprise, Cambridge, United Kingdom) was used for high-resolution data collection, signal processing and ICP curve analysis. Linear mixed-effects models and ANOVA were used to analyze changes in ICP and PRx and the influence of position. An exploratory correlation analysis was conducted on baseline variables potentially related to the ICP increase.

Results

Mean ICP increase was 1.0 mmHg ± 0.9 at 10 cmH2O PEEP, 2.0 mmHg ± 1.7 at 15 cmH2O PEEP, and 3.1 mmHg ± 1.6 at 20 cmH2O PEEP compared to a baseline PEEP of 5 cmH2O (p < 0.001). The effect of PEEP increase on ICP was not influenced by body position. PRx remained unaffected by PEEP. PEEP-induced increases in ICP were higher in cases of higher baseline ICP, higher central venous pressure, lower respiratory system elastance and lower end-inspiratory and end-expiratory transpulmonary pressures.

Conclusion

Increasing PEEP elevates ICP regardless of body position without adversely affecting cerebral autoregulation in a healthy porcine model. Baseline ICP, central venous pressure, respiratory system elastance and end-inspiratory and end-expiratory transpulmonary pressure may influence the magnitude of ICP changes.

Intravenous sedation for adults with profound acquired brain injury undergoing dental treatment - a seven-year service evaluation

BACKGROUND

Dental treatment may not be possible for patients with a profound acquired brain injury without pharmacological support. Intravenous (IV) sedation with midazolam is a widely accepted, safe, and effective mode of treatment for people with a disability, but there is limited evidence in this patient cohort.

AIMS

This evaluation aimed to review the IV sedation service for patients with profound acquired brain injury within the dental department at the Royal Hospital for Neuro-disability.

METHOD

This study was a retrospective service evaluation of IV sedation for dental treatment over seven years. Descriptive statistics are presented.

RESULTS

In total, 303 episodes of sedation were undertaken at the Royal Hospital of Neurodisability over seven years. Ninety-two percent were graded with an American Society of Anaesthesiologists (ASA) grade 3, and one-third had a history of stroke. 91% had treatment completed successfully. Complications occurred in 7.9% of cases, but all were minor, with no resulting patient harm (e.g. a transient drop in oxygen saturation).

CONCLUSION

Dentist-led IV sedation with midazolam is safe and effective for dental treatment for patients with a profound acquired brain injury in a specialised setting with experienced clinicians.

Managing Intracranial Pressure Crisis

PURPOSE OF REVIEW

The objective of this review is to provide a comprehensive management protocol for the treatment of intracranial pressure (ICP) crises based on the latest evidence.

RECENT FINDINGS

The review discusses updated information on various aspects of critical care management in patients experiencing ICP crises, including mechanical ventilation, fluid therapy, hemoglobin targets, and hypertonic saline infusion, the advantages of ICP monitoring, the critical ICP threshold, and bedside neuromonitoring. All aspects of critical care treatment, including hemodynamic and respiratory support and adjustment of ICP reduction therapy, may impact patient outcomes. ICP monitoring allows ICP values, trends, waveforms, and CPP calculation, which are helpful to guide patient care. Advanced neuromonitoring devices are available at the bedside to diagnose impaired intracranial compliance and intracranial hypertension, assess brain function, and optimize cerebral perfusion. Future research should focus on developing appropriate intervention protocols for both invasive and noninvasive neuromonitoring in managing ICP crisis patients.

Safety of flow-controlled ventilation with positive and negative end-expiratory pressure in a swine model of intracranial hypertension

BACKGROUND

Patients with brain damage often require mechanical ventilation. Although lung-protective ventilation is recommended, the application of increased positive end-expiratory pressure (PEEP) has been associated with elevated intracranial pressure (ICP) due to altered cerebral venous return. This study investigates the effects of flow-controlled ventilation (FCV) using negative end-expiratory pressures (NEEP), on cerebral hemodynamics in a swine model of intracranial hypertension.

METHODS

A model of intracranial hypertension involving bilateral trepan bolt holes was performed in 14 pigs. Pressure-controlled volume-guaranteed ventilation (PCV-VG) with PEEP and FCV using PEEP and then NEEP were applied. Intracranial pressure and oxygenation, as well as systemic hemodynamics and gas exchange parameters, were continuously monitored. Data were collected at baseline and at varying PEEP levels for both PCV-VG and FCV ventilation modalities. Following this, FCV ventilation and NEEP levels of -3, -6 and -9 cmH2O were applied.

RESULTS

ICP remained stable with low PEEP levels, but significantly decreased with NEEP. Lower ICP following NEEP improved cerebral perfusion pressure and cerebral tissue oxygenation (p < 0.05 for all). FCV with NEEP at EEP-6 and EEP-9 significantly improved cardiac output and mean arterial pressure (MAP), compared to PCV-VG and FCV using PEEP (p < 0.05, respectively). There were no significant differences in gas exchange parameters between modalities (PCV-VG vs FCV), and between the application of PEEP or NEEP. No significant correlations were observed between ΔICP and ΔMAP.

CONCLUSION

The application of FCV with NEEP appears to be a safe ventilation mode and offers an additional tool for controlling severe intracranial pressure episodes. These findings warrant validation in future studies and may lead to important potential applications in clinical practice.

The Neurological and Hemodynamics Safety of an Airway Clearance Technique in Patients with Acute Brain Injury: An Analysis of Intracranial Pressure Pulse Morphology Using a Non-Invasive Sensor

Patients with acute brain injury (ACI) often require mechanical ventilation (MV) and are subject to pulmonary complications, thus justifying the use of Airway Clearance Techniques (ACTs), but their effects on intracranial pressure (ICP) are unknown. This study investigates the neurological and hemodynamics safety of an ACT called ventilator hyperinflation (VHI) in patients with ACI. This was a randomized clinical equivalence trial, which included patients aged ≥ 18 years with a clinical diagnosis of hemorrhagic stroke, with symptom onset within 48 h. The participants were randomly allocated to the Experimental Group (EG, n = 15), which underwent VHI followed by tracheal aspiration (TA), and the Control Group (CG, n = 15), which underwent TA only. Neurological safety was verified by analyzing the morphology of the ICP wave through the non-invasive B4C sensor, which detects bone deformation of the skull, resulting in a P2/P1 ratio and TTP, and hemodynamics through a multi-parameter monitor. Evaluations were recorded during five instances: T1 (baseline/pre-VHI), T2 (post-VHI and before TA), T3 (post-TA), T4 and T5 (monitoring 10 and 20 min after T3). The comparison between groups showed that there was no effect of the technique on the neurological variables with a mean P2/P1 ratio [F (4,112) = 1.871; p = 0.120; np2 = 0.063] and TTP [F (4,112) = 2.252; p = 0.068; np2 = 0.074], and for hemodynamics, heart rate [F (4,112) = 1.920; p = 0.112; np2 = 0.064] and mean arterial pressure [F(2.73, 76.57) = 0.799; p = 0.488; np2 = 0.028]. Our results showed that VHI did not pose a neurological or hemodynamics risk in neurocritical patients after ACI.

Effects of PEEP on intracranial pressure in patients with acute brain injury: An observational, prospective and multicenter study

OBJECTIVE

To analyze the impact of positive end-expiratory pressure (PEEP) changes on intracranial pressure (ICP) dynamics in patients with acute brain injury (ABI).

DESIGN

Observational, prospective and multicenter study (PEEP-PIC study).

SETTING

Seventeen intensive care units in Spain.

PATIENTS

Neurocritically ill patients who underwent invasive neuromonitorization from November 2017 to June 2018.

INTERVENTIONS

Baseline ventilatory, hemodynamic and neuromonitoring variables were collected immediately before PEEP changes and during the following 30 min.

MAIN VARIABLES OF INTEREST

PEEP and ICP changes.

RESULTS

One-hundred and nine patients were included. Mean age was 52.68 (15.34) years, male 71 (65.13%). Traumatic brain injury was the cause of ABI in 54 (49.54%) patients. Length of mechanical ventilation was 16.52 (9.23) days. In-hospital mortality was 21.1%. PEEP increases (mean 6.24-9.10 cmH2O) resulted in ICP increase from 10.4 to 11.39 mmHg, P < .001, without changes in cerebral perfusion pressure (CPP) (P = .548). PEEP decreases (mean 8.96 to 6.53 cmH2O) resulted in ICP decrease from 10.5 to 9.62 mmHg (P = .052), without changes in CPP (P = .762). Significant correlations were established between the increase of ICP and the delta PEEP (R = 0.28, P < .001), delta driving pressure (R = 0.15, P = .038) and delta compliance (R = -0.14, P = .052). ICP increment was higher in patients with lower baseline ICP.

CONCLUSIONS

PEEP changes were not associated with clinically relevant modifications in ICP values in ABI patients. The magnitude of the change in ICP after PEEP increase was correlated with the delta of PEEP, the delta driving pressure and the delta compliance.

Focus on brain-lung crosstalk: Preventing or treating the pathological vicious circle between the brain and the lung

Recently, there has been increasing attention to bidirectional information exchange between the brain and lungs. Typical physiological data is communicated by channels like the circulation and sympathetic nervous system. However, communication between the brain and lungs can also occur in pathological conditions. Studies have shown that severe traumatic brain injury (TBI), cerebral hemorrhage, subarachnoid hemorrhage (SAH), and other brain diseases can lead to lung damage. Conversely, severe lung diseases such as acute respiratory distress syndrome (ARDS), pneumonia, and respiratory failure can exacerbate neuroinflammatory responses, aggravate brain damage, deteriorate neurological function, and result in poor prognosis. A brain or lung injury can have adverse effects on another organ through various pathways, including inflammation, immunity, oxidative stress, neurosecretory factors, microbiome and oxygen. Researchers have increasingly concentrated on possible links between the brain and lungs. However, there has been little attention given to how the interaction between the brain and lungs affects the development of brain or lung disorders, which can lead to clinical states that are susceptible to alterations and can directly affect treatment results. This review described the relationships between the brain and lung in both physiological and pathological conditions, detailing the various pathways of communication such as neurological, inflammatory, immunological, endocrine, and microbiological pathways. Meanwhile, this review provides a comprehensive summary of both pharmacological and non-pharmacological interventions for diseases related to the brain and lungs. It aims to support clinical endeavors in preventing and treating such ailments and serve as a reference for the development of relevant medications.

Nervous System Response to Neurotrauma: A Narrative Review of Cerebrovascular and Cellular Changes After Neurotrauma

Neurotrauma is a significant cause of morbidity and mortality worldwide. For instance, traumatic brain injury (TBI) causes more than 30% of all injury-related deaths in the USA annually. The underlying cause and clinical sequela vary among cases. Patients are liable to both acute and chronic changes in the nervous system after such a type of injury. Cerebrovascular disruption has the most common and serious effect in such cases because cerebrovascular autoregulation, which is one of the main determinants of cerebral perfusion pressure, can be effaced in brain injuries even in the absence of evident vascular injury. Disruption of the blood-brain barrier regulatory function may also ensue whether due to direct injury to its structure or metabolic changes. Furthermore, the autonomic nervous system (ANS) can be affected leading to sympathetic hyperactivity in many patients. On a cellular scale, the neuroinflammatory cascade medicated by the glial cells gets triggered in response to TBI. Nevertheless, cellular and molecular reactions involved in cerebrovascular repair are not fully understood yet. Most studies were done on animals with many drawbacks in interpreting results. Therefore, future studies including human subjects are necessarily needed. This review will be of relevance to clinicians and researchers interested in understanding the underlying mechanisms in neurotrauma cases and the development of proper therapies as well as those with a general interest in the neurotrauma field.