Case 90: disseminated tuberculosis.
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AIDS-Related Opportunistic Infections↗
Biomedical subjects
Luis H Luyando
Publications and source records attributed to Luis H Luyando.
Inspiratory vs. expiratory pressure-volume curves to set end-expiratory pressure in acute lung injury.
OBJECTIVE: To study the effects of two levels of positive end-expiratory pressure (PEEP), 2 cm H(2)O above the lower inflection point of the inspiratory limb and equal to the point of maximum curvature on the expiratory limb of the pressure-volume curve, in gas exchange, respiratory mechanics, and lung aeration. DESIGN AND SETTING: Prospective clinical study in the intensive care unit and computed tomography ward of a university hospital. PATIENTS: Eight patients with early acute lung injury. INTERVENTIONS: Both limbs of the static pressure-volume curve were traced and inflection points calculated using a sigmoid model. During ventilation with a tidal volume of 6 ml/kg we sequentially applied a PEEP 2 cm H(2)O above the inspiratory lower inflection point (15.5+/-3.1 cm H(2)O) and a PEEP equal to the expiratory point of maximum curvature (23.5+/-4.1 cmH(2)O). MEASUREMENTS AND RESULTS: Arterial blood gases, respiratory system compliance and resistance and changes in lung aeration (measured on three computed tomography slices during end-expiratory and end-inspiratory pauses) were measured at each PEEP level. PEEP according to the expiratory point of maximum curvature was related to an improvement in oxygenation, increase in normally aerated, decrease in nonaerated lung volumes, and greater alveolar stability. There was also an increase in PaCO(2), airway pressures, and hyperaerated lung volume. CONCLUSIONS: High PEEP levels according to the point of maximum curvature of the deflation limb of the pressure-volume curve have both benefits and drawbacks.
Aged↗
Tomographic study of the inflection points of the pressure-volume curve in acute lung injury.
The inflection points of the pressure-volume curve have been used for setting mechanical ventilation in patients with acute lung injury. However, the lung status at these points has never been specifically addressed. In 12 patients with early lung injury we traced both limbs of the pressure-volume curve by means of a stepwise change in airway pressure, and a computed tomography (CT) scan slice was obtained for every pressure level. Although aeration (increase in normally aerated lung) and recruitment (decrease in nonaerated lung) were parallel and continuous along the pressure axis during inflation, loss of aeration and derecruitment were only significant at pressures below the point of maximum curvature on the deflation limb of the pressure-volume curve. This point was related to a higher amount of normally aerated tissue and a lower amount of nonaerated tissue when compared with the lower inflection point on both limbs of the curve. Aeration at the inflection points was similar in lung injury from pulmonary or extrapulmonary origin. There were no significant changes in hyperinflated lung tissue. These results support the use of the deflation limb of the pressure-volume curve for positive end-expiratory pressure setting in patients with acute lung injury.
Adult↗