Chest
Volume 74, Issue 1, July 1978, Pages 39-44
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Clinical Investigations
A New Oxygen Cannula System Using Intermittent-Demand Nasal Flow

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A new cannula with a system of intermittent nasal flow was evaluated and compared with a standard constant-flow nasal cannula in 15 patients with chronic obstructive pulmonary disease. The intermittent-demand cannula released oxygen only when a negative pressure was detected in the nose (negative mode) or when a positive pressure ceased to be detected in the nose (positive mode). At rates of flow varying from 0.63 to 5.60 L/min, the continuous-flow mode used 9 percent more oxygen than the negative mode and 31 percent more oxygen than the positive mode to achieve comparable improvement in arterial oxygen tension. The system using the intermittent-demand cannula was sensitive and reliable in over 150 hours of testing.

Section snippets

Materials and Methods

The module for the demand cannula is schematically represented in Figure 1. The supply regulator controls the flow of oxygen to a selector switch that the operator can set to deliver oxygen either continuously or only on demand. With continuous flow the oxygen goes directly to the flowmeter and then to the patient When the selector switch is set for the demand mode, oxygen is released only at specified times. The sensitivity adjustment screw permits alteration in the triggering pressure down to

Results

All patients tolerated and completed the experiment without difficulty or complications. Based on the data of Sherter et al,23 a 30-minute period of equilibration was selected before a sample of arterial blood was drawn. The ear oximeter showed that it took from 1 to 27 minutes to stabilize a patient's SaO2 after changing the mode of delivery of oxygen. The mean time required was ten minutes; and 79 percent of the time, equilibration occurred in less than 15 minutes.

Values for SaO2 read from

Discussion

Since the 1920s, when Barach and Woodwell1 reported the clinical benefits of therapy with supplemental oxygen, a large amount of data has accrued showing the beneficial effects of therapy with low flows of oxygen on cardiac, hematologic, social, physical, psychologic, and intellectual function;6, 7, 24 however, until 1967, patients who received supplemental oxygen were relegated to a confined environment because of the lack of portability of gaseous oxygen. At that time, Levine et al25 reported

ACKNOWLEDGMENTS

We wish to thank Mr. Joseph Smith, Miss Lynn Hunt, and Mr. Eugene Cox for their technical assistance, Mrs. Mary Ann Cobb and Mrs. Marjorie Rider for typing our report, and Mrs. Alice Cullu for editorial assistance.

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    Supported by a grant from the Bendix Corp., Davenport, la.

    Read before the American Thoracic Society, San Francisco, May 16, 1977. and published as an abstract in the American Review of Respiratory Disease (115:106, 1977).

    Manuscript received September 4; revision accepted January 11.

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