Mechanical ventilation mode is one of the most important aspects of mechanical ventilation use. This mode refers to an inspiration support method. In general, fashion selection is based on clinical familiarity and institutional preferences, as there is a lack of evidence to indicate that modes affect clinical outcomes. The most commonly used forms of limited-volume mechanical ventilation are intermittent mandatory vents (IMV) and ongoing compulsory ventilation (CMV). There has been substantial change in the nomenclature of mechanical ventilation for years, but has recently become the standard by many respiratory and pulmonological groups. Writing modes is most appropriate in all uppercase letters with hyphens between cycles and strategies (ie PC-IMV, or VC-MMV, etc.)
Video Modes of mechanical ventilation
Taxonomy for mechanical ventilation
Taxonomy is a logical classification system based on 10 maxim of ventilator design
10 maxim
- The breath is a positive (inspiration) flow cycle and the negative (expired) flow that is determined in terms of the time-flow curve. The inspiration time is defined as the period from the beginning of the positive flow to the beginning of the negative stream. Expiration time is defined as the period from the beginning of the flow of expiration to the beginning of the flow of inspiration. The flow-time curve is the basis for many variables associated with ventilator settings.
- Breath is assisted if the ventilator works on the patient. The assisted breath is one that the ventilator does some part of the breathing work. For constant flow inflation, work is defined as the inspiratory pressure multiplied by the tidal volume. Therefore, the assisted breath is identified as the breath that air pressure (displayed on the ventilator) rises above the baseline during inspiration. Unassisted breathing is one for which the ventilator only provides the inspired flow requested by the patient and the pressure remains constant throughout the breath.
- Ventilators assist breathing using pressure control or volume control based on equations of motion for the respiratory system. Providing assistance means doing the work on the patient, which is achieved by controlling the pressure or volume. A simple mathematical model that explains this fact is known as the motion equation for a passive breathing system:
In this equation, pressure, volume, and flow are all continuous time functions. The actual pressure is the pressure difference across the system (eg, the transducpiration pressure is defined as the pressure at the minus pressure of air opening on the body surface). Elastance (defined as pressure change divided by the associated volume change, reciprocal adherence) and resistance (defined as changes in pressure divided by corresponding changes in flow) are parameters assumed to remain constant during breath.Pressure = (Elastansi ÃÆ'â € "Volume) (Resistance ÃÆ'â €" Flow)
Volume control (VC) means that the volume and flow are set before inspiration. In other words, the right-hand side of the equation of motion remains constant while the pressure changes with changes in elastance and resistance Pressure control (PC) means that the inspiratory pressure is set as a constant value or proportional to the patient's inspirational effort. In other words, the left-hand side of the motion equation remains constant while the volume and flow change with changes in elastance and resistance.
Time control (TC) means that, in some rare situations, no predefined variables (pressure, volume, or flow) are set previously. In this case only the inspired time and expiration are prearranged. - Breaths are grouped according to criteria that trigger (start) and cycle (stop) inspiration. The beginning of inspiration is called triggering events. The final inspiration is called cycle events.
- Trigger and cycle events can be initiated by the patient or machine. Inspiration can be triggered by a patient or a patient who cycles with a signal representing an inspirational effort. Inspiration can also be triggered by a machine or engine that is driven by a predefined ventilator threshold.
Patient triggers mean starting inspiration based on patient signals that are independent of the engine trigger signal. Engine trigger means initiating inspiratory flow based on the signal from the ventilator, independent of the patient's trigger signal. Cycling patients means ending inspiration time based on signals representing the patient's determined components of the equations of motion, (ie, elastance or resistance and including effects due to inspiration). Current cycling is a cycling form of the patient because the rate of decay of flow to the threshold of the cycle is determined by the mechanics of the patient. The cycling machine means an end to the inspiration time independent of the signal representing the patient's determined component of the equation of motion.
- Breath is classified as spontaneous or mandatory based on trigger and cycle events. Spontaneous breathing is the breath in which the patient triggers and inhaling. Spontaneous breathing may occur during mandatory breathing (eg Air Pressure Release Ventilation). Spontaneous breathing can be helped or not helped. The mandatory breath is the breath that triggers the machine and/or inhaling. Mandatory breathing may occur during spontaneous breath (eg, High Frequency Jet Ventilation). Breath is mandatory, by definition, aided.
- There are 3 breath sequences: Ongoing Ventilation (CMV), Intermittent Mandatory Ventilation (IMV), and Continuous Spontaneous Ventilation (CSV). The breath sequence is a special pattern of spontaneous and/or mandatory breathing. 3 possible breathing sequences are: continuous mandatory ventilation, (CMV, spontaneous breath is not allowed between mandatory breaths), intermittent mandatory ventilation (IMV, spontaneous breath may occur between mandatory breaths), and ongoing spontaneous ventilation (CSV, all spontaneous breaths).
- There are 5 basic ventilation patterns: VC-CMV, VC-IMV, PC-CMV, PC-IMV, and PC-CSV. The combination of VC-CSV is not possible because the volume control implies the machine cycle and the engine cycle makes every breath mandatory, not spontaneous. The sixth pattern, TC-IMV is possible but rare.
- Within each ventilation pattern there are several variations that can be distinguished by its targeting scheme. Targeting scheme is a description of how the ventilator reaches a predetermined target. The target is the target ventilator output that has been determined. Examples of deep breath targets include inspiration flow or set-point targeting, tidal volume (double targeting) and constant proportionality between inspiratory pressure and patient effort (servo targeting). Examples of intermediate tidal targets and targeting schemes include average tidal volume (for adaptive targeting), percent minute ventilation (for optimal targeting) and a combination of PCO2 values, volumes, and frequencies depicting "comfort zones" (for intelligent targeting, for example, SmartCarePS or IntelliVent-ASV). Targeting schemes (or combinations of targeting schemes) are what distinguish one pattern of ventilation from another. There are 7 basic targeting schemes consisting of a wide range that are visible in various ventilation modes:
Set-point: The targeting scheme in which the operator specifies all parameters of pressure wave (pressure control mode) or volume and flow waveform (volume control mode).
Dual: A targeting scheme that allows the ventilator to switch between volume control and pressure control during an inspiration Bio-variable: A targeting scheme that allows the ventilator to automatically adjust the inspiratory pressure or tidal volume randomly to mimic the variability observed during normal breathing.
Servo: A targeting scheme whose inspiration pressures are comparable to the inspirational effort Adaptive: A targeting scheme that allows the ventilator to automatically set one target (for example, pressure in the breath) to reach another target (eg, average tidal volume through several breaths).
Optimal: Targeting schemes that automatically adjust the target ventilation pattern either minimize or maximize some overall performance characteristics (for example, minimize the level of work performed by the ventilation pattern). Smart: Targeting schemes that use artificial intelligence programs like fuzzy logic, rule-based expert systems, and artificial neural networks. - A ventilation mode is classified according to its control variables, breath order, and targeting scheme (s). The previous 9 principles created a theoretical foundation for taxonomic mechanical ventilation. Taxonomy is based on this theoretical construct and has four hierarchical levels:
- Control Variables (Pressure or Volume, for primary breath)
- Breath Order (CMV, IMV, or CSV)
- Primary Breathing Improvement Scheme (for CMV or CSV)
- Secondary Breathing Targeting Scheme (for IMV)
"The primary breath" is the only breath available (mandatory for CMV and spontaneous for CSV) or it is the mandatory breath in IMV. The targeting scheme can be represented by a single lowercase letter: set-point = s, dual = d, servo = r, bio-variable = b, adaptive = a, optimal = o, intelligent = i. Tags stands for classification of modes, such as PC-IMV, s. Compound tags are possible, for example, PC-IMVoi, oi.
How is the mode classified
Step 1: Identify the primary breath control variable. If inspiration begins with a preset inspiratory pressure, or if the pressure is proportional to the inspiration effort, then the control variable is pressure. If inspiration begins with the tidal volume of the preset and the inspiration flow, then the control variable is the volume. If both are incorrect, the control variable is time.
Step 2: Identify the sequence of breaths. Determine whether trigger events and cycles are the patient or machine specified. Then, use this information to determine the order of the breath.
Step 3: Identify targeting schemes for primary breath and (if applicable) secondary breath.
The sample mode classification is given below
Mode Name: A/C Volume Control (Covidien PB 840)
- The volume and flow of inspiration are preset, so the control variable is volume.
- Each breath is a cycling volume, which is a form of cycling machine. Every breath that inspires a cycling machine is classified as a mandatory breath. Therefore, the breathing sequence is a continuous mandatory ventilation.
- The operator controls all the volume parameters and flow waveforms so that the targeting scheme is set-point. Thus, this mode is classified as a continuous mandatory volume control control with set-point targeting (VC-CMVs).
Mode Name: SIMV Volume Control Plus (Covidien PB 840)
- The operator sets the tidal volume but not the inspiration stream. Because the self-volume setting (such as flow settings only) is a necessary but not sufficient criterion for volume control, the control variable is pressure.
- Spontaneous breathing is allowed between the mandatory breaths so that the order of breaths is IMV.
- Ventilator adjusts the inspiratory pressure between the breath to achieve the average tidal preset volume, so the targeting scheme is adaptive. The tag mode is PC-IMVa, s.
Maps Modes of mechanical ventilation
Description of common mode
Help mode, control mode and control-aid mode
The fundamental difference in mechanical ventilation is whether each breath is initiated by the patient (aid mode) or by the machine (control mode). The dynamic hybrid of the two (aid-control mode) is also possible, and the control mode without help is now mostly obsolete.
Ventilation of air pressure release
The air pressure release ventilation is a time-biking alternator between two positive airway pressure levels, with a prime time at a high level and a short expiration release to facilitate ventilation.
Airway pressure release ventilation is usually used as an inverse-type ventilation type. Respiratory time (T low ) is shortened to usually less than a second to maintain alveoli inflation. In a basic sense, this is a sustained pressure with a short release. APRV is currently the most efficient conventional mode for ventilation of the lungs.
Different perceptions of this mode may exist around the world. While 'APRV' is common to users in North America, a very similar mode, positive biphasic air pressure (BIPAP), was introduced in Europe. The term APRV has also been used in American journals where, from the characteristics of ventilation, BIPAP would be a very good terminology. But BiPAP (tm) is a trademark for noninvasive ventilation mode in a special ventilator (Respironics Inc.).
Other manufacturers have followed suit with their own brand name (BILEVEL, DUOPAP, BIVENT). Although similar in modality, these terms illustrate how a mode is intended to inflate the lungs, rather than defining the characteristics of synchronization or a supported spontaneous breathing.
Intermittent compulsory ventilation does not always have a synchronized feature, so mode sharing is understood as SIMV (synced) vs IMV (not-synced). Since the American Association for Respiratory Care establishes the nomenclature of mechanical ventilation, the "synchronized" part of the title has been dropped and now there is only IMV.
Ventilate minutes required
Mandatory minutes of compulsory (MMV) allow for spontaneous breathing with automatic adjustment of mandatory ventilation to meet minimum minute patient preset volume requirements. If the patient maintains a minute volume setting for V T x f, no mandatory breathing is sent.
If the patient's minutes volume is insufficient, a mandatory delivery of a preset tidal volume will occur until the minute volume is reached. The method to monitor whether the patient meets the required ventilation (V E ) differs from the ventilator and model brands, but, in general, there is a monitored time window, and a smaller window is checked against a larger window ie, at the DrÃÆ'¤ger EvitaÃ,® line of mechanical ventilator there is a moving 20 seconds window, and every 7 seconds of current tidal volume and rate is measured) to decide whether mechanical breathing is necessary to keep the vents minute.
MMV is the optimal mode for weaning in both the neonatal and pediatric populations and has been shown to reduce long-term complications associated with mechanical ventilation.
Volume control settings
The pressure-adjustment volume control is IMV-based mode. Pressurized pressure volume control using limited pressure, targeted volume, breathing cycle time which can be either a ventilator or a starting patient.
The highest inspiratory pressure provided by the ventilator varies by breath-to-breath to achieve the tidal volume target set by the physician.
For example, if the target tidal volume of 500 mL is set but the ventilator gives 600 mL, the next breath will be sent with a lower inspiratory pressure to achieve a lower tidal volume. Although PRVC is considered a hybrid mode because tidal volume adjustment (VC) and pressure-restriction setting (PC) is basically PRVC is a pressure control mode with adaptive targeting.
Continuous positive air pressure
Continous positive airway pressure (CPAP) is a noninvasive positive pressure mode for respiratory support. CPAP is the pressure applied at the end of the breath to keep the alveoli open and not completely deflate. This mechanism for maintaining increased alveoli helps increase the partial pressure of oxygen in arterial blood, an increase in proper CPAP increases PaO 2 . CPAP is not technically a "ventilation" mode because it does not directly affect minute volume.
Automatic positive airway pressure
Automatic positive airway pressure (APAP) is a CPAP form that automatically sets the amount of pressure delivered to the patient to the minimum required to maintain an unobstructed airway on a breath-by-breath basis by measuring resistance in the patient's breathing.
Bilevel positive airway pressure
Bilevel positive airway pressure (BPAP) is the mode used during non-invasive ventilation (NIV). First used in 1988 by Professor Benzer in Austria, it provides predetermined positive inspiratory air pressure (IPAP) and positive expiratory airway pressure (EPAP). BPAP can be described as a Continuous Positive Air Pressure system with a change in time cycle of the applied CPAP level. CPAP, BPAP and other non-invasive ventilation modes have proven to be an effective management tool for chronic obstructive pulmonary disease and acute respiratory failure.
Often BPAP is incorrectly referred to as "BiPAP". BiPAP is the name of a portable ventilator manufactured by Respironics Corporation; it is just one of many ventilators that can deliver BPAP.
Medical use
BPAP has been shown to be useful in reducing mortality and reducing the need for endotracheal intubation when used in people with chronic obstructive pulmonary disease (COPD). High-frequency_ventilation_.28Active.29 "> High-frequency ventilation (On)
The term active refers to the ventilator's forced expiratory system. In the HFV-A scenario, the ventilator uses pressure to apply the breath of inspiration and then apply opposite pressure to force the expiratory breath. In high frequency oscillating ventilation (sometimes abbreviated HFOV) bellows oscillations and positive pressure of piston pressure and apply negative pressure to force expiration.
High-frequency ventilation (Passive)
The term passive refers to the ventilator's non-forced expiratory system. In the HFV-P scenario, the ventilator uses pressure to apply the breath of inspiration and then returns to atmospheric pressure to allow passive expiration. This is seen in High Frequency Jet Vents, sometimes abbreviated as HFJV. It is also categorized under High Frequency Ventilation of High Frequency Percussive Vents, sometimes abbreviated as HFPV. With HFPV it utilizes an open circuit to provide its subtidal volume by means of a patient interface known as Phasitron.
Volume assurance
Volume guarantees additional parameters available in many ventilator types that allow the ventilator to change its inspiratory pressure setting to achieve minimum tidal volume. It is most commonly used in neonatal patients who require controlled pressure mode with consideration to control the volume to minimize volutrauma.
Respiratory settings and spontaneous support
Positive final expiratory pressure
The positive end-expiratory pressure (PEEP) is the pressure applied after expiration. PEEP is applied using either a valve connected to the expiration port and manually set or the valve is managed internally by a mechanical ventilator.
PEEP is the pressure that must be exhaled, consequently causing the alveoli to remain open and not completely deflated. This mechanism for maintaining increased alveoli helps increase the partial pressure of oxygen in arterial blood, and increased PEEP increases PaO 2 .
Support pressure
Pressure Support is a spontaneous ventilation mode also called Pressure Support Ventilation (PSV). The patient starts each breath and the ventilator provides support with the preset pressure value. With support from the ventilator, the patient also regulates their own respiratory rate and their tidal volume.
In Pressure Support, the level of regulated inspiration pressure support is kept constant and there is a slowing down of flow. The patient triggers all the breath. If there is a change in the mechanical properties of the lungs/chest and patient efforts, the tidal volume that is sent will be affected. The user should then set the pressure support level to get the desired ventilation.
Pressure support increases oxygenation, ventilation and decreases breathing work.
See also adaptive support vents.
Other ventilation modes and strategies
Closed loop system
Adaptive Support Ventilation
Adaptive Support Ventilation is the only commercially available closed mode of mechanical ventilation to date using "optimal targeting". This targeting scheme was first described by Tehrani in 1991, and was designed to minimize breathing work rates, mimic natural breathing, stimulate spontaneous breathing, and reduce weaning time.
Automatic Tube Compensation
Automatic Tube Compensation (ATC) is the simplest example of a computer-controlled targeting system in a ventilator. This is a form of servo targeting.
The goal of ATC is to support resistive breathing work through artificial airways
Neurologically Adjusted Ventilation Support
Neurally Adjusted Ventilatory Assist (NAVA) is customized by a computer (servo) and similar to ATC but with more complex requirements for implementation.
In terms of patient-ventilator sync, NAVA supports resistive and elastic breathing work in proportion to patient inspiration efforts
Proportional Aid Ventilation
Proportional auxiliary ventilation (PAV) is a mode based on other servo targeting where the ventilator guarantees the percentage of work without changes in compliance and lung resistance.
Ventilators vary the volume and tidal pressure based on respiratory work of the patient. The amount given is proportional to the percentage of aid set for grant.
PAV, like NAVA, supports restrictive and elastic breathing work in proportion to patient inspiration.
Liquid ventilation
Liquid ventilation is a mechanical ventilation technique in which the lungs are wrapped with oxygenated perfluorochemical fluid rather than a mixture of oxygen-containing gases. The use of perfluorochemicals, not nitrogen, as an inert carrier of oxygen and carbon dioxide offers a number of theoretical advantages for the treatment of acute pulmonary injury, including:
- Reduce the surface tension by maintaining the fluid interface with alveoli
- Opening of collapsed alveoli by hydraulic pressure with lower barotrauma risk
- Provides a reservoir in which oxygen and carbon dioxide can be exchanged for pulmonary capillary blood
- Works as a high efficiency heat exchanger
Despite its theoretical advantages, efficacy studies have been disappointing and optimal clinical use of LV has not been determined.
Total liquid vents
In total ventilation (TLV), the entire lung is filled with oxygenated PFC fluid, and the liquid tidal volume of PFC is actively pumped in and out of the lungs. Special equipment is required to transmit and release solid and solid PFC volume, and to extract oxygen and remove carbon dioxide from liquids.
Partial liquid vents
In the partial fluid ventilation (PLV), the lungs are slowly filled with equivalent volume of PFC or close to the FRC during the gas vents. PFC in oxygenated lungs and carbon dioxide is released by inhaling respiratory gas in the lungs with a conventional gas ventilator.
See also
- Mechanical ventilation mode table
- Mechanical Ventilation
- Respiratory Therapy
- Bubble CPAP
References
Source of the article : Wikipedia
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