The newest quinolone antibacterial agents and theophylline.

486 Communications to the Editor well described by Pepe and Marini#{176}and is an important cause of hypotension in mechanically ventilated patients. The lungs are unable to exhale to FRC at the start of the next mechanically initiated inspiration because of airway obstruction. Positive end expiratorv intrathoracic pressure builds up, although this cannot be shown on the ventilator manometer. The patient described by Shennib et al could have had this cause for hypotension, rather than mediastinal emphysema. Restoration of blood pressure after sternotomy and recurrence ofhypotension on closing the chest supports this view. Auto-PEEP can be assessed by occluding the expiratory line at the end ofthe set exhalation period and delaying the next ventilator. delivered breath.#{176} Pressure in the tubings will equilibrate with intrathoracic pressure, and PEEP will be shown on the ventilator manometer. Ifthis pressure is high, tidal volume or ventilatory rate needs to be decreased. Hypercapnea may result from this reduction ofminute volume, but it is better to keep the patient hypoventilated and alive’ than risk the consequences ofhigh auto-PEEP This should always be considered before proceeding to surgical decompression of any pneumomediastinum or laying the chest cavity open.