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In Reply.
—The positive end expiratory pressure technique described by Perel provides satisfactory oxygenation during apnea tests and may be superior to tracheal catheterization in certain patients with lung diseases. Confirmation of this theoretical superiority awaits a controlled study that compares positive end expiratory pressure with tracheal catheterization.We cannot use positive end expiratory pressure for apnea tests at our hospital because the ventilators (Puritan-Bennett 7200a, Puritan-Bennett Corp, Carlsbad, Calif) have a safety mechanism that automatically ventilates the patient after approximately 30 seconds of apnea. Most ventilators designed for clinical use have the same limitation. It may be unrealistic to expect physicians to perform apnea tests requiring special equipment. Tracheal catheterization, it should be noted, is easily and inexpensively performed with readily available materials.