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Monitoring during mechanical ventilation: MECHANICS DURING MECHANICAL VENTILATION (4)

Evaluation of the static pressure-volume (P-V) curve may be useful for patients with acute respiratory distress syndrome (ARDS). In such patients, the P-V curve typically has a sigmoidal shape with an inflection point at low lung volume (lower Pflex) and another inflection point at high lung volume (upper Pflex) (Figure 6). PEEP should be set above the lower Pflex to avoid repeated opening and closing of lung units with each respiratory cycle. Likewise, Pplat should be set below the upper Pflex to avoid overdistension injury to the lungs. In other words, the patient should be ventilated on the linear compliant part of the P-V curve. The P-V curve can be constructed for individual patients by changing inspired VT for a few breaths and measuring the resultant Pplat (after which the baseline level of ventilation is re-established). If this procedure is performed for a sufficient number of VTs, the static P-V curve can be constructed. To identify the lower Pflex, PEEP must be removed during these manoeuvres. It must be recognized that the static P-V curve so constructed is different from the dynamic P-V curve displayed on ventilator lung mechanics displays. The dynamic P-V curve only approximates the static P-V curve during constant slow inflation. The dynamic P-V curve is not a valid reflection of lung mechanics with decelerating flow patterns such as those that occur with pressure ventilation. Efficient treatment has got less costly: find sildenafil online pharmacy cheap at best online pharmacy.

Figure 6. Monitoring during mechnical
Figure 6) Static pressure-volume curve. Note the lower and upper inflection points. Positive end-expiratory pressure (PEEP) should be set above the lower inflection point and tidal volume should be set below the upper inflection point

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