Volume versus Pressure-targeted Ventilation – Surgery&Rehabilitation Example

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"Volume versus Pressure-targeted Ventilation" is a great example of a paper on surgery and rehabilitation.   During thoracic surgery, it is only possible to ensure anesthesia through one-lung ventilation for facilitating surgical exposure (Ortiz, Krick, & Cano, 2013). The main aim is to protect and isolate the patient’ s lungs during the surgery. However, the method is what laid the basis for other ventilation methods in thoracic surgeries. New methods like Volume controlled ventilation came into existence and were the most preferable for ventilating lungs during thoracic surgeries. For instance, the volume control uses a set of tidal volume (VT) (van Kaam, 2011).

There is a ventilator that calculates the flow according to the established tidal volume as well as inspiratory time to deliver the particular tidal volume. Eventually, the procedure can achieve volume-controlled waveforms. Therefore, the surgeon observes changes in inspiration and expiration. On the other hand, Pressure targeted ventilation involves setting a particular tidal volume value the ventilator delivers the volume through constant pressure and decelerating flow (Raimondo et al. , 2014). Therefore, the ventilator adjusts inspiratory pressure that the tidal volume requires so that the surgeon uses the least pressure to ventilate the lung.

It is, therefore, imperative to outline how surgeons apply the two methods during thoracic surgeries and the possible effects of each method. Briefly, this research paper strives to distinguish between the use of Volume and Pressure targeted ventilation of the thoracic surgical patients. Volume versus pressure targeted controls In the pressure targeted controls, there are pressure limits relative to the varying tidal volumes (NCBI, 2014). On the contrary, volume-targeted uses pre-set inspiration time to guarantee the flow as well as the resulting tidal volume depending on the variability of the airway pressure (Raimondo et al. , 2014).

When using pressure-targeted ventilation, surgeons normally select targeted inspiration time and pressure by considering the preferred tidal volume. The surgeons closely monitor the process since any possible change in the mechanics of the lung may affect the tidal volume. Volume targeted ventilation requires a good selection of a pattern of flow delivery as well as tidal volume (van Kaam, 2011).   Furthermore, VCV requires close monitoring of the peak airway pressure since variations in lung mechanics may also affect the pressure (van Kaam, 2011).

Volume targeted ventilation provides pre-set volumes unless the procedure exceeds the pressure limit. There are many advantages of volume targeted ventilation including the use of predictable tidal volume and flexible adjustments of volume. On the other hand, the volume target methods guarantee pre-set minute ventilations. Minute ventilation does not change when surgeons alter lung compliance or airway resistance (Raimondo et al. , 2014). Therefore, a comparison between volume and pressure targeted ventilation strives to outline the possible advantages and disadvantages of using the two methods. Volume targeted controls                       There are various methods of volume targeted controls, and some include assist control ventilation and intermittent mandatory control (NCBI, 2014).

Regarding assist control, the method is volume targeted ventilation that helps surgeons by pre-setting tidal volumes on each and every respiratory effort or in some cases the baseline rate of respiration (Raimondo et al. , 2014). The method is most common in Intensive care units. It also delivers mandatory rates, respiration, or breaths that can occur when a patient does not make any effort or the ventilator is unable to sense inspiration and expiration.

On the other hand, any breathing effort by the patient delivers breath in the predetermined tidal volume and the flow rate records as mandatory breath. All the activities enable the patient to have a minimum as well as minute ventilation. However, it is possible to set the rate of inspiration flows. The implication is that setting the rates may result in shorter cycles than the respiratory pattern of the patient (NCBI, 2014). In this case, the patient might be in danger of premature breath termination, and this may lead to dysynchrony (Raimondo et al. , 2014).

Therefore, the method is least popular owing to its inability to respond to possible changes in compliance of the lung. On the other hand, the inability to synchronize the whole respiratory system can lead to breathing difficulties thus the patient might fight the ventilator. Another important volume ventilation method is intermittent mandatory ventilation (NCBI, 2014). The method dates back to many decades and was the first ventilation mode. Besides, the method uses pre-set mandatory breaths that support patients with breathing difficulties like thoracic surgeries (Raimondo et al. , 2014).

In this case, the surgeon initiates spontaneous breaths thus further tailoring breath in patients through airway pressure supplementation. IVM came to existence owing to the problems that surgeons experienced with ACV. The implication is that ACV deregulated muscle activities of the diaphragm thus leading to wasting of the muscles. Though IVM has been common among modern physicians, the method least improves gaseous exchange, weaning times, and never allows the diaphragm to rest (NCBI, 2014). On the other hand, the method poses high risks since it requires mechanical ventilation.

Therefore, of the two volume-targeted ventilations, ACV can sometimes be advantageous over IVM.   Pressure targeted ventilation                       The PCV methods use specific inspiration rates and targeted pressures in determining when it is necessary to terminate patient breath (Raimondo et al. , 2014). The method differs with ACV that uses tidal volume in determining patient breathing rate. The use of specific respiratory rate and target pressure enables surgeons to establish maximum pressure for each breath; maximum levels that a ventilator cannot exceed. The particular feature has gained ground since there are increasing cases of lung injuries that originate from poor ventilation during surgery (Fisher, G.W & Cohen, 2010).

On the other hand, the method is advantageous over ACV since tidal volumes have a high potential of inducing lung damage.   However, the negative effect of PCV ventilation is that the method does not change with lung compliance (Raimondo et al. , 2014). On the other hand, it leads to patient discomfort thus increasing sedation as well as airway pressure. The PCV also monitors different parameters including PEEP, respiratory frequency, pressure of inspiration, percentage duty cycle.

Though the method does not measure peak flows and tidal volume, it is possible to determine them by using resistance and compliance of a patient's respiratory system. Moreover, the PCV method is most preferable when a clinician wishes to control the alveolar pressure making it possible to reduce barotrauma risks (Fisher, & Cohen, 2010). Other clinicians prefer the method because it easily controls the mean airway pressure (MAP). Differences between volume and pressure targeted ventilation                       Volume and pressure targeted ventilations have both risks and benefits thus physicians must apply them cautiously.

One common thing with the two methods is that there must be pre-set PEEP and FiO2 (Raimondo et al. , 2014). When using pressure targeted ventilation, a clinician must identify inspiratory pressure as well as inspiration time. The two elements of pressure control and pressure support are different when using pressure targeted ventilation. Pressure support refers to patient-initiated breath while pressure control uses the time to offset breath cycles instead of airflow (NCBI, 2014). On the contrary, volume targeted ventilation establishes pre-set volumes, and it has the advantage of delivering specific tidal volumes.

On the other hand, the method can ventilate patients who have difficulty in receiving medication. Therefore, it is most useful in acute care. However, the method differs from pressure-targeted ventilation with its fixed inflation time that does not integrate with changes in the patient’ s lungs. Conclusion   In summary, the two ventilation methods in thoracic surgery namely volume and pressure targeted ventilation have both merits and demerits. Though the comparison between the methods emphasizes on advantages and disadvantages, the techniques have different functionalities.   Pressure targeted controls use pressure limits depending on the tidal volumes while volume-targeted controls use pre-set times in guarantying airflow and tidal volume (NCBI, 2014).   In comparing the two methods, the research paper also found out that volume-targeted ventilation is of two types namely assist control ventilation and intermittent mandatory ventilation.

The two methods have different specifications that further differentiate the ventilation technique from pressure-targeted controls. One advantage of pressure-targeted controls is that they can initiate a breath, unlike volume-targeted methods that must rely on the patient breath. The implication is that pressure controls help patients with breathing difficulties through volume controls have the advantage of using pre-set volumes.

References

Fisher, G.W & Cohen, E. (2010). An update on anaesthesia for thoracic surgery. Retrieved on 24th November 2014 from

NCBI, (2014). Volume-controlled versus pressure-controlled ventilation-volume guaranteed mode during one-lung ventilation. Korean Journal of Anaesthology. Retrieved on 24th November 2014 from

Ortiz, M. G. T., Krick, S., & Cano, J. P. S. (2013). High-Frequency Oscillatory Ventilation, MicroRNAs in Pulmonary Hypertension, and Gastric Residual Volumes. American journal of respiratory and critical care medicine, 188(4), 23-34.

Raimondo, P. et al., (2014). Lateral decubitus and one lung ventilation in thoracic surgery: the role of esophageal pressure at residual volume. Preliminary physiological study: 5AP4‐9. European Journal of Anaesthesiology (EJA), 31(1), 88-96.

van Kaam, A. (2011). Lung-protective ventilation in neonatology. Neonatology, 99(4), 338-341.

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