Critical Care

Acute respiratory failure

Clinical care

Technical physicians specialized in mechanical ventilation and respiratory monitoring are able to independently initiate and adjust the process of mechanical ventilation in critically ill patients. Advanced technologies to gain insight into the function of the lungs and respiratory muscles, which helps to optimize mechanical ventilation and minimize the risk of ventilator-associated injury are often needed. This applies to the acute phase of respiratory failure, difficult weaning of the mechanical ventilator and non-invasive respiratory support. With knowledge of both technology and clinical practice, technical physicians can perform advanced measurements and from there provide advice for the individual patient on respiratory support and monitoring technology.

The technical physician evaluates lung aeration and recruitable lung volume using computed tomography (CT), ultrasound and electrical impedance tomography (EIT). Developing methods for obtaining new information from these imaging techniques is done by technical physicians. In addition, monitoring a patient’s respiratory effort is a significant component of the technical physician’s expertise. Next to physical examination and graphical inspection of ventilator waveforms (if applicable), esophageal manometry or transdiaphragmatic pressure measurements are used to quantify breathing effort. And surface electrodes and electrodes placed on a nasogastric tube are used to acquire electromyographic signals of respiratory muscles to assess breathing effort. Furthermore, ultrasound measurements are used to evaluate function and effort of components of the respiratory muscle pump including the lung, diaphragm, abdominal wall muscles and accessory muscles. Technical physicians perform and interpret these complex measurements, associated signal and data analysis. These tools can be used to titrate ventilator settings, to assess and improve patient-ventilator interaction, and to diagnose respiratory muscle weakness/injury and the reason for difficult weaning.

The technical physician is also involved in the implementation and use of alternative ventilation modes, such as high frequency oscillatory ventilation (HFOV) in paediatrics. This ventilation at a supraphysiological frequency requires personalized ventilatory settings. Finally, the technical physician is involved in the implementation of new technologies, such as the use of closed-loop algorithms to titrate mechanical ventilator settings or new applications of existing lung function measurements (e.g. using the Forced Oscillation Technique (FOT)). In this way, the technical physician effectively contributes to providing lung-protective ventilation to the patient.

Clinical case

A 3-month-old infant was admitted to a pediatric ICU due to viral pneumonia while being mechanically ventilated in a pressure controlled mode with a frequency of 35 breaths/min. Neuromuscular blockers were started because the patient had toxic high peak pressures. Airway and transpulmonary (using an esophageal balloon) pressures and EIT images were assessed to optimize ventilator settings. High plateau pressures with high levels of intrinsic positive end-expiratory pressure (PEEP) and hyperinflated EIT images were found. With increasing PEEP (from 0 to 15 cm H2O), a remarkable decrease in plateau pressures and intrinsic PEEP and associated improvement of respiratory system compliance and EIT’s ventilation distribution were observed.

Due to significantly elevated intrinsic PEEP levels, a bronchoscopy was conducted, revealing a pulsating collapse of the distal part of the trachea. Furthermore, CT scans of the arteries, conducted at varying PEEP levels, identified a double aortic arch encircling and compressing the trachea. Surgical repair was performed and the patient was successfully weaned from the ventilator.

Scientific research

Acute respiratory failure is one of the leading causes of mechanical ventilation initiation and ICU admission [1]. Although mechanical ventilation is life-saving, it may induce lung and diaphragm injury through various interacting mechanisms [2]. There is ongoing research to better understand the pathophysiological mechanisms of these injuries. Advanced respiratory monitoring involves several tools to conduct an in-depth evaluation of the lung and respiratory muscles [3]. Advanced respiratory monitoring tools currently used in research include esophageal manometry [4], lung ultrasound [5][6] and electrical activity of the diaphragm [7].

Non-invasive ventilation has been shown to be effective in avoiding intubation and improving survival in patients with acute respiratory failure when compared to conventional oxygen therapy [8]. Several aspects are studied to improve patient adaptation. The use of electrical activity of the diaphragm (EADi)-driven ventilation has been shown to enhance patient comfort (9).

Circulatory failure & hemodynamics

Clinical care[KB4]

Technical physicians specializing in haemodynamics integrate clinical skills with innovative technologies to analyze circulatory problems and provide effective (technological) treatment and support.

Advanced haemodynamic monitoring, where blood pressure, blood flow, perfusion and/or saturation are (continuously) measured in more or less invasive ways to optimize hemodynamics are often needed. The technical physician understands the underlying technical principles, physiological models and limitations of these techniques and can therefore advise on the appropriate monitoring technique for the individual patient. The technical physician can also perform in-depth analyses of these measurements and, by integrating different types of information, extract more predictive or diagnostic value from existing measurements. Automation of monitoring, analysis and alarms, can be implemented by the technical physician in critical care departments, reducing the number of alarms and making them more informative. Also, using innovative parameters in cardiac ultrasound, the technical physician can diagnose underlying haemodynamic problems.

With all of these techniques, technical physicians can provide clinical decision support on an individual patient level and thus contribute to more personalized treatment. In the area of haemodynamic management, technical physicians can support the automation of therapies. Examples include the implementation of closed loop infusion of fluids and vasoactive drugs based on automated data analysis and physiological models. In patients with severe circulatory failure, the technical physician can assist in the optimal setting of mechanical support such as heart-lung machines, ventricular assist devices and extracorporeal membrane oxygenation (ECMO). The interaction between this technology and the patient can be mapped by the technical physician and used to advise on the weaning from this support.

In collaboration with various specialists, such as intensivists, anaesthesiologists, thoracic surgeons and cardiologists, the technical physician plays a role in clinical decisions, assists in the design of protocols and thereby making care more efficient and effective.

Clinical case

A 69-years-old patiënt admitted to the ICU with an abdominal sepsis, further complicated by acute respiratory distress syndrome (ARDS), experiences hypotension. The clinical question is whether the patient could benefit from more fluid infusion, i.e. being fluid responsive. Especially in the presence of ARDS it is important not the cause fluid overload, as this could lead to more pulmonary edema and/or loading of the right ventricle further deteriorating the patient’s pulmonary and cardiovascular condition. Since the patient is mechanically ventilated with pressure support and a low tidal volume, the conventional measure for fluid responsiveness, pulse pressure variation, is unreliable. The technical physician advises to perform other, more personalized fluid responsiveness tests based on heart-lung interaction. These are bedside maneuvers with the ventilator, in this case an end-expiratory occlusion test predicted that fluid loading would increase cardiac output in this patient.

Particularly in the area of heart-lung interaction, the technical physician can play an important role due to his/her sound physiological knowledge, systemic, model-based approach to the human body and interdisciplinary role. Other applications of heart-lung interaction are, for example, cardioprotective ventilation and cardiac issues in ventilator weaning.

Scientific research

The large amounts of data enables many opportunities to gain insights into hemodynamics and develop new diagnostics or interventions. With the use of machine or deep learning to predict patient ICU outcome, the effect of hemodynamic interventions or blood pressure forecasting are being researched [ref]. Machine learning models and/or physiological physics based cardiovascular models, could be used to construct a computer replica of the individual patient, i.e. a digital twin, when tuned using hemodynamic data. These digital twins could then be used to reveal underlying hemodynamic problems and test different interventions, in this way serve as a clinical decision support tool [ref].

Advanced signal analysis research aids automatic online analysis of hemodynamic signals, for example studies in the morphology of the arterial pressure waveform, so that it can be used bedside comparable to the ECG signal [ref]. In combination with integration of signals and other data from different monitors and devices, new possibilities arise to enrich this information. For instance, data from the ventilator and the cardiac monitor to automatically assess fluid responsiveness [ref]. Further automation of therapies, such as closed loop vasopressor administration based on the patient’s blood pressure, is a field of research that could reduce nurse workload and aid in the overall clinical personnel shortage.

Neuromonitoring in ICU

Clinical care

In ICU patients with acute life-threatening conditions of the central or peripheral nervous system, promoting recovery from the primary injury, preventing secondary brain damage and starting the rehabilitation process as early as possible is of special interest. Multimodal neuromonitoring is the cornerstone of modern neurointensive care, as regular clinical examination of a neurological patient in the ICU is of limited value as these patients are often comatose, intubated and sedated [ref]. Due to the unique location of the brain within the skull, this monitoring requires complex techniques and signal analysis.

Bedside signal analysis to assess the reactivity of the cerebral blood vessels in patients with traumatic brain injury is one of the complex techniques used to monitor these patients. Based on arterial blood pressure and intracranial pressure (ICP), a tailored recommendation for pressure regulation can be made to ensure the best possible cerebral blood flow [ref]. By using transcranial Doppler (TCD), assessment of cerebral blood flow velocity in patients with SAH can be made to detect vasospasm and prevent DCI. Comprehensive analysis of (quantified) EEG provides information about i.e. depth of sedation and can be used for prognostic purposes in patients after cardiac arrest. Using near-infrared spectroscopy (NIRS) and brain tissue oxygenation (PbtO2), assessment of oxygenation of the brian can be made.

To perform, integrate, and interpret the various types of monitoring, knowledge of the technical aspects of the monitor as well as a sound understanding of the anatomy and underlying (patho)physiology is essential and preferably done by a technical physician. Correct application of the techniques allows for early detection of complications, prevention of secondary deterioration and the development of an optimal individual treatment plan for each patient. Collaboration with the departments of neurosurgery, neurology and clinical neurophysiology is essential.

Clinical case

A 45-year-old cyclist was involved in a severe road traffic accident. The trauma team arrives by helicopter when the patient loses consciousness and scores a Glasgow coma scale of three with sluggish pupils. The team decides to intubate and rush to the nearest emergency department. The initial computed tomography scan shows an extensive subdural hematoma with midline shift, indicating increased intracranial pressure and the prompt requirement of neurosurgical intervention. After removal of the hematoma, a combined intracranial pressure (ICP) and brain tissue oxygenation (PbtO2) sensor was placed to monitor the neurological state of the patient in the ICU. Blood pressure management was started according to protocol and ICP and PbtO2 were within normal ranges. The technical physician routinely starts bedside analysis of the available physiological time series to create a clear overview of the most important parameters and continuously assess the status of cerebral vascular reactivity. The next day, the patient develops increased ICP with PbtO2 levels at ischemic threshold. Analysis of ICP and blood pressure signals revealed deterioration of the status of cerebral autoregulation with a decrease in limits of regulation at higher blood pressure levels than currently regulated. By increasing blood pressure, the ICU team was able to steer towards a level of reactivity where cerebral blood flow was adequate, normalizing ICP and PbtO2 levels.

Scientific research

The directions and possibilities of scientific research using multimodal neuromonitoring are endless. Research is conducted using neuromonitoring to provide more insight in neurological deterioration in patients with various conditions in the ICU, providing more understanding and insight in pathophysiological mechanisms [9]. Research using advanced signal analysis can provide potential new bedside tools and parameters to assess the condition of the patient or target values [10][11][12][13]. Analysis of large quantities of data is suited for predictive (AI driven) modeling that can be used for i.e. prediction of intracranial hypertension, brain hypoxia or mortality [14][15].

Intramural patient monitoring

Clinical care

Due to the increasing pressure on the Dutch healthcare system, interest in remote monitoring of patients is growing, also in perioperative care. The Integral Care Agreement (IZA) and Framework for Appropriate Care focus on delivering the right care at the right place and digitally where possible. Another important aspect is to sustainably deploy staff and reduce administrative burdens. The use of technology in healthcare processes is necessary to maintain high-quality care, especially with the aging population and the increase in vulnerable patients with multiple chronic conditions.

The technical physician specialising in inpatient monitoring is working on wearable sensors for patient monitoring in clinical practice. Patient monitoring holds value and impact in various aspects. It reduces administrative pressure of healthcare professionals by replacing manual measurements of vital signs with a wearable sensor that measures continuously. This also contributes to the availability of necessary patient data. Thus, it can support healthcare professionals in earlier recognition of deterioration, evaluating recovery, and decision-making. Patient monitoring can reduce the transition between high-care units (e.g. intensive care unit (ICU) or postanesthesia care unit (PACU), general wards, and home settings while strengthening patient empowerment, enabling patients to work on recovery earlier and more efficiently.

Clinical case

Patients who (have a high risk of) obstructive sleep apnea syndrome (OSAS) remain in the PACU for 24 hours after surgery for monitoring of any occurrences of breath cessation leading to reduced blood oxygen saturation. However, these patients could be transferred to a ward earlier with a validated wearable sensor continuously measuring oxygen saturation and respiratory rate, while nurses receive notifications on their mobile devices when measured values drop below target levels. Patients also benefit from a quieter environment on the ward, promoting better sleep patterns, and earlier mobilisation. Other examples for continuous monitoring on the ward include patients admitted from the emergency department to the ward with a high risk of developing sepsis or patients on the ward seen by the ICU consultant, which may prevent ICU admission.

The technical physician plays a significant role in the implementation of continuous monitoring at the ward, including the choice and use of wearable sensors, development of clinical monitoring protocols, and education of nurses. Moreover, the technical physician advises on the application of monitoring of specific patients and patient populations, and is part of the multidisciplinary team to improve patient monitoring (e.g. by development of alarm strategies).

Scientific research

Closing the monitoring gaps between the perioperative care units, ICU, surgical ward and home for early warning of postoperative deterioration, while allowing early mobilization, is considered one of the main applications of telemonitoring [16][17]. Vital signs can change in the hours before certain complications [18], however, this could be missed due to the intermittent monitoring at the ward. On top of that, nurse documentation on vital signs is not always complete and error prone [19]. New devices and algorithms are being developed to derive a wide range of parameters from photoplethysmography and/or electrocardiography signals. Continuous monitoring of vital signs with a wearable sensor at the surgical ward has been associated with early administration of antibiotics in sepsis, shorter length of hospital stay, and lower risk for readmission within 30-days after discharge [20]. However, high quality studies that report clinical benefit or cost-effectiveness of wearable sensors for continuous monitoring on the ward are lacking, and wearable sensors are often still in the phase of evaluation for clinical validation or feasibility [21][22]. One of the main challenges of telemonitoring is the interpretation of the data. In general, most healthcare professionals are not used to interpreting data from continuous monitoring. Main barriers for telemonitoring on the ward are nursing engagement and alarm burden [16][20][23][24]. Software or algorithms are needed to assist in deriving, handling and interpreting data from patients by telemonitoring, but it is currently unknown what suitable alarm criteria are.