Patient-ventilator Interface Research Articles

A Compartment-Based Mathematical Model for Studying Convective Aerosol Transport in Newborns Receiving Nebulized Drugs during Noninvasive Respiratory Support.

Nebulization could be a valuable solution to administer drugs to neonates receiving noninvasive respiratory support. Small and irregular tidal volumes and air leaks at the patient interface, which are specific characteristics of this patient population and are primarily responsible for the low doses delivered to the lung (DDL) found in this application, have not been thoroughly addressed in in vitro and in vivo studies for quantifying DDL. Therefore, we propose a compartment-based mathematical model able to describe convective aerosol transport mechanisms to complement the existing deposition models. Our model encompasses a mechanical ventilator, a nebulizer, and the patient; the model considers the gas flowing between compartments, including air leaks at the patient–ventilator interface. Aerosol particles are suspended in the gas flow and homogeneously distributed. The impact of breathing pattern variability, volume of the nebulizer, and leaks level on DDL is assessed in representative conditions. The main finding of this study is that convective mechanisms associated to air leaks and breathing patterns with tidal volumes smaller than the nebulizer dramatically reduce the DDL (up to 70%). This study provides a possible explanation to the inconsistent results of drug aerosolization in clinical studies and may provide guidance to improve nebulizer design and clinical procedures.

Associated factors of facial pressure ulcers in patients under non-invasive ventilation during hospital stay in an intermediate care facilities of a Portuguese hospital

Background & Aim: Non-invasive ventilation is a procedure that reduces respiratory stress and improves gas exchange, using a patient-ventilator interface; however, it presents consequences such as the development of facial pressure ulcers. We aim to identify the factors associated with facial pressure ulcers in Intermediate Care Facilities patients submitted to non-invasive ventilation. Methods & Materials: A cross-sectional descriptive and analytic study was performed in an intermediate care facilities, of a Portuguese hospital, from August to October of 2018, the study population consisted of patients hospitalized in this unit, who underwent to non-invasive ventilation. Data were collected through an observational form developed to obtain the information of the entire period of hospitalization of the patient. The software used to analyze the data was IBM SPSS Statistics for Windows, Version 23.0. For the descriptive analysis, absolute and relative frequencies also means and standard deviations were computed. Also, to describe the association between the variables, The point biserial correlation coefficient (rpb) were calculated. For data analysis, a significance level of .05 (α) was used. Results: 14.6% of the individuals developed PU, all in the nasal pyramid. NIV was used for 6.07±3.91 days, and PU developed between the 3rd and the 20th day. It was observed that the presence of PU had a significant positive correlation with the GCS score (rpb=0.390, p=0.012) and a significant negative correlation with the duration of NIV (rpb=-0.438, p=0.004). Dependency level, PU risk, and nutritional risk did not correlate with the development of PU. Conclusion: The pressure ulcers associated with non-invasive ventilation appear to be more frequently developed on the nasal pyramid and between the 3rd and the 20th day. Moreover, the level of consciousness and the time of administration of non-invasive ventilation are associated with the development of pressure ulcers.

CLINICAL APPLICATIONS OF CAPNOGRAPHY AMONG MECHANICALLY VENTILATED CHILDREN

Background: Capnography provides insight into the management of many emergencies. It reflects the factors affecting perfusion and metabolism, and it is used for continuous monitoring of mechanically-ventilated patients.Objectives: To investigate the correlation between the partial pressure of end tidal carbon dioxide (PetCO2) and arterial blood carbon dioxide (PaCO2), and to investigate the accuracy of the change of capnographic curve in diagnosis of special pathological situations. Patients and Methods: A total of 100 patients (1 day to 15 years), mechanically-ventilated due to various clinical causes were monitored by PetCO2, and arterial blood gas (ABG) concomitant with assessment of PetCO2. Results: Significant correlation was found between PaCO2 and PetCO2, and abnormal PaCO2-PetCO2 gradient was found to be correlated well with the duration of mechanical ventilation. Various PetCO2 waveforms were recorded. Conclusion: Capnography should be used for monitoring of critically ill patients and for confirmation of endotracheal intubation. It should be applied during cardio pulmonary resuscitation (CPR) and to monitor the quality of CPR. It is used to monitor the integrity of patient ventilator interface, identification of ventilated patients in need for additional sedation or neuromuscular blockage, and readjustment of ventilator parameters.

Automatic protective ventilation using the ARDSNet protocol with the additional monitoring of electrical impedance tomography.

IntroductionAutomatic ventilation for patients with respiratory failure aims at reducing mortality and can minimize the workload of clinical staff, offer standardized continuous care, and ultimately save the overall cost of therapy. We therefore developed a prototype for closed-loop ventilation using acute respiratory distress syndrome network (ARDSNet) protocol, called autoARDSNet.MethodsA protocol-driven ventilation using goal-oriented structural programming was implemented and used for 4 hours in seven pigs with lavage-induced acute respiratory distress syndrome (ARDS). Oxygenation, plateau pressure and pH goals were controlled during the automatic ventilation therapy using autoARDSNet. Monitoring included standard respiratory, arterial blood gas analysis and electrical impedance tomography (EIT) images. After 2-hour automatic ventilation, a disconnection of the animal from the ventilator was carried out for 10 seconds, simulating a frequent clinical scenario for routine clinical care or intra-hospital transport.ResultsThis pilot study of seven pigs showed stable and robust response for oxygenation, plateau pressure and pH value using the automated system. A 10-second disconnection at the patient-ventilator interface caused impaired oxygenation and severe acidosis. However, the automated protocol-driven ventilation was able to solve these problems. Additionally, regional ventilation was monitored by EIT for the evaluation of ventilation in real-time at bedside with one prominent case of pneumothorax.ConclusionsWe implemented an automatic ventilation therapy using ARDSNet protocol with seven pigs. All positive outcomes were obtained by the closed-loop ventilation therapy, which can offer a continuous standard protocol-driven algorithm to ARDS subjects.

Patient machine interface for the control of mechanical ventilation devices.

The potential of Brain Computer Interfaces (BCIs) to translate brain activity into commands to control external devices during mechanical ventilation (MV) remains largely unexplored. This is surprising since the amount of patients that might benefit from such assistance is considerably larger than the number of patients requiring BCI for motor control. Given the transient nature of MV (i.e., used mainly over night or during acute clinical conditions), precluding the use of invasive methods, and inspired by current research on BCIs, we argue that scalp recorded EEG (electroencephalography) signals can provide a non-invasive direct communication pathway between the brain and the ventilator. In this paper we propose a Patient Ventilator Interface (PVI) to control a ventilator during variable conscious states (i.e., wake, sleep, etc.). After a brief introduction on the neural control of breathing and the clinical conditions requiring the use of MV we discuss the conventional techniques used during MV. The schema of the PVI is presented followed by a description of the neural signals that can be used for the on-line control. To illustrate the full approach, we present data from a healthy subject, where the inspiration and expiration periods during voluntary breathing were discriminated with a 92% accuracy (10-fold cross-validation) from the scalp EEG data. The paper ends with a discussion on the advantages and obstacles that can be forecasted in this novel application of the concept of BCI.

Ventilação mecânica não invasiva

Patients with acute respiratory failure have been treated with intubation and mechanical ventilation for treatment of hypoxemia, hypoventilation and respiratory distress. However, tracheal intubation is associated with several complications, use of sedatives and prolongation of hospitalization time. Noninvasive ventilation provides ventilatory assistance without the need of artificial airway, with the use of masks in patient-ventilator interface. Its use in clinical practice has increased over the last 20 years as well as the availability of technology resources for its implementation. Currently, it is considered first-line treatment for acute respiratory insufficiency. Similar to invasive ventilation, noninvasive ventilation can reduce the work of breathing and respiratory rate, increase tidal volume, improve gas exchange, dyspnea, promote rest of respiratory muscles and patient comfort. Its indication is well established in chronic obstructive pulmonary disease, cardiogenic pulmonary edema and in immunosuppressed patients. Other clinical applications should be carefully evaluated as a delay in the intubation can increase mortality in these patients. Some protocols are available in the literature but the clinical judgment and knowledge of available resources by well-trained staff are key to the success of noninvasive ventilation. Likewise, choosing the correct interface, ventilation mode and monitoring in intensive care unit optimize patient comfort and patient-ventilator interaction with better clinical outcomes. This article aims to review the latest literature on indications and clinical use of noninvasive ventilation.

Asynchrony and DyspneaDiscussion

Patient-ventilator synchrony and patient comfort are assumed to go hand in hand, yet few studies provide support for this common sense idea. In reality, synchrony between the patient and ventilator is complex and can be affected by the ventilator settings, type of ventilator, patient-ventilator interface, and sedation. Inspections of airway pressure and flow waveforms are reliable methods for detecting asynchrony, and automated detection seems accurate. A number of types of asynchronies have been defined, and asynchrony during invasive and noninvasive ventilation have different calling cards. There is a clear association between asynchrony, ventilator-induced diaphragmatic dysfunction, and duration of mechanical ventilation. Whether these are cause and effect or simply associated remains to be determined.

Automatic detection of AutoPEEP during controlled mechanical ventilation

BackgroundDynamic hyperinflation, hereafter called AutoPEEP (auto-positive end expiratory pressure) with some slight language abuse, is a frequent deleterious phenomenon in patients undergoing mechanical ventilation. Although not readily quantifiable, AutoPEEP can be recognized on the expiratory portion of the flow waveform. If expiratory flow does not return to zero before the next inspiration, AutoPEEP is present. This simple detection however requires the eye of an expert clinician at the patient’s bedside. An automatic detection of AutoPEEP should be helpful to optimize care.MethodsIn this paper, a platform for automatic detection of AutoPEEP based on the flow signal available on most of recent mechanical ventilators is introduced. The detection algorithms are developed on the basis of robust non-parametric hypothesis testings that require no prior information on the signal distribution. In particular, two detectors are proposed: one is based on SNT (Signal Norm Testing) and the other is an extension of SNT in the sequential framework. The performance assessment was carried out on a respiratory system analog and ex-vivo on various retrospectively acquired patient curves.ResultsThe experiment results have shown that the proposed algorithm provides relevant AutoPEEP detection on both simulated and real data. The analysis of clinical data has shown that the proposed detectors can be used to automatically detect AutoPEEP with an accuracy of 93% and a recall (sensitivity) of 90%.ConclusionsThe proposed platform provides an automatic early detection of AutoPEEP. Such functionality can be integrated in the currently used mechanical ventilator for continuous monitoring of the patient-ventilator interface and, therefore, alleviate the clinician task.

Patient-Ventilator Interaction: The Last 40 Years

Patient-ventilator synchrony is a complex issue affected by ventilator performance, patient characteristics, and the patient-ventilator interface. The history of patient-ventilator interaction includes avoidance of pharmacalogic paralysis, the development of spontaneous breathing systems, microprocessor technology to maximize interaction, and closed-loop control. While most clinicians agree that patient-ventilator synchrony is desirable, there remain no cause-and-effect data that asynchrony is associated with poor outcome.

Patient-Ventilator Dyssynchrony: Clinical Significance and Implications for Practice

The cost of providing care to critically ill patients in the United States consumes roughly 15% of all health care dollars, or 1% of the gross national product.1 Contributing to this economic burden are patients admitted to the intensive care unit (ICU) who require mechanical ventilation and patients with complications from their dependence on this technology.2,3 In fact, 50% of ICU patients receive mechanical ventilation.4 Often, sedation is required to increase patients’ tolerance of the endotracheal tube, reduce anxiety, and facilitate sleep. In particular, sedation is used frequently to reduce patient-ventilator dyssynchrony (PVD).5–9 Sassoon and Foster10 define PVD as a mismatching between the patient’s breaths (neural) and ventilator-assisted breaths (phase asynchrony), as well as the inability of the ventilator’s flow delivery to match the patient’s flow demand (flow asynchrony). This definition suggests a faulty interaction between the patient and ventilator that is commonly managed by sedation and advanced ventilator modes and adjustments. The correction of PVD is complex and multifaceted given the current capabilities of traditional ventilators. An imperfect solution exists because the sensitivity and responsiveness of both the patient and the ventilator during the interaction is confounded by factors related to the patient and the ventilator. However, in light of the most serious complications (hypoxemia, barotrauma, prolonged mechanical ventilation, and discomfort) of PVD, and an imperfect solution for the resolution of PVD at the current time, nurses continue to face the challenge of preventing the consequences of PVD as well as complications due to oversedation or undersedation. In this article, we discuss the factors contributing to PVD; the manifestations, measurement, types, and causes of PVD; nursing implications; and future directions for improvement, with nursing research questions proposed for consideration.

Performance of noninvasive ventilation modes on ICU ventilators during pressure support: a bench model study

Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. Bench model study in an intensive care research laboratory of a university hospital. Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to a lung model featuring a plastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. On most ventilators leaks led to an increase in trigger delay and workload, a decrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilator.

New advances in the use of noninvasive ventilation for acute hypoxaemic respiratory failure

Noninvasive ventilation (NIV) includes various techniques for augmenting alveolar ventilation without an endotracheal airway. The theoretical advantages of this approach include avoiding the complications associated with endotracheal intubation, improving patient comfort, preserving airway defence mechanisms, speech and swallowing. The successful application of NIV in hypoxaemic acute respiratory failure (ARF) of varied etiologies has been extensively described but success rate is strictly dependent on ARF etiology and until today the application of NIV strategies in the setting of hypoxaemic ARF is controversial. Larger, controlled studies are required to clarify the role of NIV in the setting of hypoxaemic ARF. The correct choice of the patient ventilator interface is a crucial issue in noninvasive ventilation. The study of new interfaces could improve tolerability reducing the noninvasive ventilation failure rate.