The major advantage of volume control ventilation:-
Correct Answer: Constant tidal volume
Description: Volume - controlled ventilation, where the inflation volume is preselected, and the ventilator automatically adjusts the inflation pressure to deliver the desired volume. the rate of lung inflation can be constant or decelerating. Advantages of volume control ventilation Guaranteed tidal volumes produce a more stable minute volume.The reliability of the minute volume makes this mode of ventilation more appropriate in situations where careful control of PaCO2is of impoance. Volume controlled modes were the standard of care for patients with severe traumatic brain injury where tight PaCO2 control is necessary. The minute volume remains stable over a range of changing pulmonary characteristics.If airway resistance fluctuates significantly (eg. in the course of therapy for status asthmaticus) this mode has the advantage of maintaining a reliable minute volume. The initial flow rate is lower than in pressure-controlled modes. This is an advantage if airway resistance is high; blowing more slowly into the tight bronchi does not produce a high resistance-related early pressure peak, and potentially prevents an early termination of the breath by the pressure alarm limit. Disadvantages of volume control ventilation The mean airway pressure is lower with volume control ventilation,due to the slopy shape of the pressure waveform. This can theoretically be a disadvantage in patients who have severe hypoxia; in those people one might want to use a pressure-controlled mode instead. One wa of getting around this is to use an inspiratory pause, which is discussed elsewhere (in summary, it doesn't work and possibly increases the work of breathing). Recruitment may be poorer in lung units with poor compliance.Units with a long time constant and poor compliance may remain unrecruited until very late in the inspiratory phase when pressure approaches its maximum value. These units will have little time for gas exchange before the ventilator cycles to expiration. From this, one might expect that with a volume-controlled mode the degree of atelectasis will be greater than with a pressure controlled mode, peak aiway pressures being equal. In the presence of a leak, the mean airway pressure may be unstable.The constant flow used during VCV may not be able to compensate for an intermittent leak.Consider: if the leak flow rate is equal to the inspiratory flow rate, there will be no volume delivered. Insufficient flow may give rise to patient-ventilatordyssynchrony.In the presence of increased respiratory demand during the course of a breath, the ventilator may not meet the patient's need for increased flow.
Category:
Anaesthesia
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