Advanced Interactive Modes of Mechanical Ventilation - Research Paper Example

No Advanced Mechanical Ventilation: What are the Advanced Interactive Modes of Mechanical Ventilation? 1. Introduction Mechanical ventilation has become a breakthrough and necessary component of sustaining life in various settings especially in the Intensive Care Unit (Carbery 106). However, studies have brought to light that despite its life-saving abilities, mechanical ventilation brings about greater risks for the patient, as well as the healthcare institution. These risks include lung injury for the patient, and added healthcare costs if not used properly for the hospital or healthcare institution (Rose and Ed 145). Because of these risks, modifications and developments in mechanical ventilation have been developed to decrease the said risks posed by mechanical ventilation (Esteban, Ferguson and Meade 170). In relation, this paper will then explore the different advanced modes of mechanical ventilation. Five main mechanical ventilation modes will be presented. These modes are applied to certain situations and careful study is needed to better understand which modality is best for a specific situation. In this paper, each mode will be reviewed for its purpose, functionality, mechanism, and others. This paper will first discuss the dual-control or combination mode, followed by the Biphasic Positive Airway Pressure (BiPAP) mode and Proportional Assist Ventilation mode. Then, the Adaptive Support Ventilation mode will be explored, followed by Automatic Endotracheal Tube Compensation mode. 2. Advanced Interactive Modes of Mechanical Ventilation 2.1 Dual-Control Mode One of the advanced modalities in mechanical ventilation recently developed is the dual control mode. Combination or “Dual-Control” Modes of mechanical ventilation merge together the features of pressure-targeted and volume-targeted ventilation so as to guarantee minute ventilation (VE) or a minimum tidal volume (Vt) while at the same time restricting the amount of pressure in the system (Branson 232). With this feature, dual-control modes allow guaranteed inspiratory pressure as well as tidal volume (Rose and Ed 146). Dual control modes are also sometimes “combination” modes because they combine the attributes of volume and pressure targeting to be able to achieve goals in ventilation that would have been otherwise unattainable if pressure targeting and volume targeting modes were used independently. Still, even though dual-control modes combine the said features, it is still primarily pressure-targeted. For example, Pressure Control supplies the full support in dual-control modes, while pressure support generally supplies the partial support in dual-control modes (Rose and Ed 147). In an earlier study by Brochard, Haraf, and Lorino conducted in 1989, they stated that dual-control modes of ventilation are more favored in maintaining a constant tidal volume especially in conditions where the affected individual has recurrent variations in airway pressure or resistance (514). As a form of hybrid mode, the double-control mode of mechanical ventilation was designed to address the problems with high peak airway pressures in volume ventilation. It was also designed to address the problems associated with varying tidal volumes that sometimes happen with the use of pressure ventilation. Dual-control modes are able to address these problems because pressure and volume controls automatically adjust to guarantee a minimum VE or Vt. However, Grossbach, Chlan and Tracy (33) noted that although dual-control modes are promising, studies have not necessarily shown that this advanced more of mechanical ventilation is necessarily more successful that the conventional modes of mechanical ventilation, especially if proper attention is given to Vt. 2.2 Biphasic Positive Airway Pressure (BiPAP) Mode Another advanced mode of ventilation is the Biphasic Positive Airway Pressure or BiPAP. It actually falls under the category of dual-control mechanical ventilation, but it is among the most prominent and most utilized dual-control modes. Sometimes termed simply as BiLevel, this mode of ventilation involves the adjustment of the airway pressure baseline from which spontaneous breathing takes place along two levels or phases. In other words, BiPAP allows spontaneous respiration during the two phases of the ventilator cycle: inspiration and expiration (Seymour, Frazer and Reilly 1299). The BiPAP mode aims to permit unrestricted spontaneous respiration in order to promote weaning and decrease sedation. This mode functions by delivering time-cycled, time-triggered, and pressure-controlled breaths based on a scheme of set-points. Even with the patient’s spontaneous breaths, the mechanical ventilator retains a constant pressure based on the set points. By preserving the patient’s spontaneous breathing, BiPAP is slated to improve synchrony by reducing the patient’s need for sedation and his/her needed effort of breathing. In theory, BiPAP is also believed to improve the patient’s hemodynamic profile through different mechanisms, especially spontaneous respiration. These improvements can be manifested in better organ perfusion, reduced workload for the ventricles, greater cardiac output, decreased requirement for vasopressors, and numerous others (Mireles-Cabodevila, Diaz-Guzman and Heresi 425-426). This mode of ventilation is most intended for weaning, but it is also used for ventilation, although it is most ideal for patients with good respiratory effort. BiPAP mode of ventilation allows the superimposition of spontaneous breaths on a specified amount or number of ventilator cycles that are pressure controlled. As a result of this mechanism, BiPAP mode of mechanical ventilation decreases the system’s peak airway pressures, since the patient can breathe spontaneously, with the aid of the machine, at both high pressure levels, and low pressure levels (Yazici, Uzun, Ülgen, Teke, Maden, Kayrak, Turan and Ari 427). Although it may appear that the BiPAP mode of mechanical ventilation bears a resemblance to inverse ratio mechanical ventilation, the breathing cycles of the patient in BiPAP actually take place through an open system, in contrast to a closed circuit. This open circuit works in such a way that the airway pressure does not surpass the desired value or pressure. Because of this open circuit, the BiPAP mode has an improved synchrony between the machine response and the patient’s effort (Rose and Hawkins 1768). 2.3 Proportional Assist Ventilation Mode Another advanced mode of mechanical ventilation involves the Proportional Assist Ventilation (PAV) mode. This advanced mode of mechanical ventilation is an alternative mode of partial ventilator support, and works by amplifying the individual’s instantaneous volume and flow, so as to decrease the resistive and elastic loads (Hart, Hunt and Polkey 979). This mode has been developed as an effective way of improving the interaction between the patient and the ventilator. Such an improvement in the interaction is achieved through a mechanism that puts the one of the two oscillatory pumps under the direction of the other. In other words, the mechanical ventilator is placed under the control of the patient’s central control of respiration (Younes 116). Ambrosino and Rossi notes that the PAV mode is the only mode physiologically designed in such a way that the technical support specifically offered by ventilators is not the priority or is not the main aspect of the system that is working. Moreover, the PAV mode works in a manner wherein pressure is generated by the ventilator in proportion to the spontaneous efforts of the patient. In other words, the greater that the patient breaths, then the greater the pressure generated by the machine. Therefore, the PAV mode allows the mechanical ventilator to amplify the inspiratory effort of the patient without any pre-set setting of targeted pressure or volume. This lack of a preselected value allows the patient to reach whatever breathing pattern and ventilation is most suitable for the whole system, especially the patient. Through this, the PAV mode assumes control on the ventilation system and creates a situation wherein the neuroventilatory uncoupling is established by the discrepancy between the inadequate capacity of the ventilator pump to deal with the workload and the high ventilator demand of the patient. Thus, in a sense, PAV supplies an additional lung muscle which under the complete control of the individual’s ventilator drive (Mireles-Cabodevila, Diaz-Guzman, Heresi and Chatburn 423-424). By providing ventilatory assistance in terms of volume and flow, the PAV mode greatly unloads the elastic and resistive burdens in the system. Also, since there is no target pressure, volume or flow in PAV, the responsibility of controlling the breathing pattern is shifted to the patient from the caregiver, thus promoting patient-ventilator interaction (Ambrosino and Rossi 273). A study by Hart et al. revealed that PAV is useful in helping patients with chronic respiratory failure to have an improved minute ventilation and breathing pattern while at the same time unloading the breathing muscles through an effective patient-ventilator interaction (979). Moreover, another study by Hawkins et al. found that PAV helps in increasing COPD patients’ tolerance to exercise (858). 2.4 Adaptive Support Ventilation Mode Another advanced mode of ventilation worth looking into is the Adaptive Support Ventilation or ASV. This mode is a closed-loop mode that evolved as a type of compulsory minute ventilation that is accompanied by adaptive pressure control (Kirakli et al. 774). As a form of minute ventilation, this mode permits the operator to pre-specify an intended minute ventilation, and if the patient’s spontaneous respiration generates a minute ventilation lower than the desired, the machine then provides either pressure-controlled or volume-controlled mandatory breaths (Dongelmans et al. 565). The ASV mode automatically chooses the suitable tidal volume for spontaneous respirations as well as the frequency and tidal volume for mandatory respiration based on the aimed-for minute alveolar ventilation and system mechanics of respiration (Petter et al. 1743). It works by delivering pressure-controlled respirations with the use of an optimal adaptive scheme. The term optimal refers to the mechanical effort of inspiration, wherein the machine chooses a frequency and tidal volume that the individual’s brain would supposedly select if he were not hooked to a mechanical ventilator (Mireles-Cabodevila et al. 423). The machine calculates the normal needed minute ventilation according to the patient’s estimated dead space volume and ideal body weight. After calculation, the ventilator initially supplies test breaths and then measures the different variables involved with the whole respiration process. From these, the target or optimal tidal volume is computed and the settings are adjusted. In theory, the aforementioned pattern encourages the patient to produce spontaneous breaths. The ventilator also continuously monitors the mechanics of the respiratory system, and accordingly adjusts the setting (Chen et al. 977). ASV is most commonly used for patients who are being weaned from ventilation (Mireles-Cabodevila et al. 423). 2.5 Automatic ET Tube Compensation Mode The last mode to be discussed, the automatic ET tube compensation mode, involves the maximization of the functions of the endotracheal tube. In here, the endotracheal tube supplies greater resistance to the whole process of ventilation during both expiration and inspiration. It is most commonly called as automatic tube compensation or ATC, and it works by adjusting the pressure output of the system based on the flow, providing an appropriate value of pressure support needed especially as the flow demands vary along the different respiration cycles (Cohen, Shapiro and Grozovski 982). Some variations of the ATC speed up expiration by dropping pressures in the airway during the early section of expiration. This reduction of airway pressure in the expiratory phase is sometimes used a means of compensation for tube resistance. Moreover, ATC delivers exactly the amount of pressure needed to overcome the resistance placed by the ET tube during the flow measured at that instant (Fabry et al. 281). A remarkable characteristic of ATC is that the intratracheal pressure contained at the carinal end of the ET tube is the mechanism used to control the flow of air. The ATC mode of mechanical ventilation calculates intratracheal pressure through the properties of the ET tube, the circuit pressure, and the inspiratory flow of the patient. As with most of the other advanced modes of mechanical ventilation, ATC is also most suitable for weaning patients off of the mechanical ventilator (Unoki, Serita and Grap 37). 3. Conclusion Numerous other modes of advanced mechanical ventilation have been developed over the past years, and some are still being developed. The modes discussed in this paper are among the most common advanced mode and the practitioner must have adequate knowledge to be able to make the best decision on which mode will be used for which situations. Works Cited Ambrosino, N and A Rossi. 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