Evaluation of right ventricular function by TEE in a group of 75 ARDS patients submitted to protective ventilation revealed the persistence of a 25% incidence of ACP, resulting in detrimental hemodynamic consequences associated with tachycardia. However, ACP was reversible in patients who recovered and did not increase mortality.

In a context such as acute respiratory distress syndrome, where optimum tidal volume and airway pressure levels are debated, the present study was designed to differentiate the right ventricular (RV) consequences of increasing lung volume from those secondary to increasing airway pressure during tidal ventilation. The study was conducted by combined two-dimensional echocardiographic and Doppler studies in 10 patients requiring mechanical ventilation in the controlled mode because of acute respiratory failure. Continuous monitoring of airway pressure on echocardiographic and Doppler recordings provided accurate timing of each cardiac event during the respiratory cycle, with particular attention being paid to end-expiratory and end-inspiratory atrial diameters, RV dimensions, and pulmonary artery and tricuspid flow estimated by the velocity-time integral (PA(VTI) and T(VTI), respectively). At baseline, lung inflation during the inspiratory phase of mechanical ventilation produced a drop in PA(VTI) from 14.3 +/- 2.6 cm at end expiration to 11.3 +/- 2.1 cm at end inspiration. This drop occurred without reduction in right atrial diameter or in RV diastolic dimensions. It was not preceded but was followed by a decrease in T(VTI), thus confirming an increase in RV outflow impedance. Manipulation of tidal volume without changing airway pressure and manipulation of airway pressure without changing tidal volume demonstrated that tidal volume, but not airway pressure, was the main determinant factor of RV afterloading during mechanical ventilation.

RV outflow impedance evaluated by the Doppler technique appeared sensitive to PEEP titration. Application of PEEPA worsened RV systolic function impairment produced by tidal ventilation. Conversely, application of PEEPS reduced RV systolic function impairment, suggesting an association with a lower pulmonary vascular resistance.

Using a simple technique, ultrasound identifies the dominant internal jugular vein, thus indicating the safer side before blind catheterization.

The transesophageal echocardiography study was unable to confirm the reality of the concept of early preload adaptation by left ventricular dilatation in septic shock. Conversely, because left ventricular volume always remained in a normal range after correcting hypovolemia, systolic function was the unique determinant of stroke index in septic shock.

The presence of an initial segment with a low compliance on the static pressure-volume (PV) curve in patients with acute respiratory distress syndrome (ARDS) indicates that some lung compartments do not initially receive insufflated gas. We tested the hypothesis that an uneven distribution of time constants, producing a "slow compartment," was in part responsible for the change in compliance between the initial and the intermediate segment of the PV curve. In 16 patients with ARDS submitted to mechanical ventilation in volume-controlled mode with a supportive respiratory rate of 15 breaths/minute, we constructed the static PV curve on the first day of respiratory support and determined the intrinsic positive end-expiratory pressure (PEEPi4) during a prolonged end-expiratory pause (4 seconds). We also measured the volume of a "slow compartment" during a prolonged expiration (> 6 seconds), and determined an external PEEP (PEEPe) suppressing PEEPi4. Among the 16 patients studied, 11 exhibited a low inflection point, associated with a "slow compartment" of 172 +/- 83 ml, responsible for a PEEPi4 of 3 +/- 2 cm H2O. Conversely, the five remaining patients had a linear PV curve, associated with a minimal "slow compartment" of 28 +/- 10 ml, responsible for a negligible PEEPi4. We observed that individual slopes of the initial segment of the PV curve were inversely and significantly correlated with the proportion of the "slow compartment" (r = -0.85). We concluded that the shape of the inspiratory PV curve in ARDS might be dependent on the presence of a "slow compartment," and demonstrated that a low external PEEP appeared sufficient to achieve a substantial mechanical improvement in clinical practice.

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