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A bedside device to hold the fiberoptic bronchoscope.

We appreciate the interest shown by Dr. Corddry in our editorial on competent internal jugular valves. We are puzzled as to his contention that we speculated that internal jugular valves (IJV) might insulate the jugular venous system from sustained increases in central venous pressure (CVP), secondary to congestive heart failure or increased mean airway pressures. Obviously, one-way valves cannot “insulate” any flowing system against increase; in pressure. In the editorial, we asked the question, “Could higher positive end-expiratory pressure (PEEP) or peak airway pressure be used if we know the IJV are competent?” In a flowing, pulsatile system, less energy will be transmitted in a retrograde direction with one-way valves. It seems reasonable that competent IJV may facilitate the management of patients with the undesirable combination of closed head injury and oxygenation problems. PEEP raises end-expiratory pressure to the level of PEEP applied, but, during inspiration, the increase in peak airway pressure is greater than the magnitude of PEEP because compliance decreases with increased lung volume. An increase in CVP follows the increase in airway pressure with the addition of PEEP. The ratio of pressure increase is not one to one because there are other factors, such as lung compliance, which determine how much of the airway pressure increase is transmitted to the superior vena cava. Although competent IJV cannot negate the slight decrease in cerebral perfusion pressure during expiration with the addition of PEEP, they might protect the cerebral circulation from the pulsatile higher CW during the inspiratory phase of mechanical ventilation. The protection would be partial, because closure of the IJV would only prevent back pressure from the high CVP from being transmitted to the upper jugular venous system. There would still be a brief buildup of pressure from drainage of blood from the sagittal sinuses. That pressure rapidly diminishes as blood flows across the IJV when the pressure on the other side of the competent IJV decreases during expiration. Therefore, competent IJV cannot isolate cerebral circulation from short-lived high CVP, but it is reasonable to say they may provide some benefits when they are competent.