Hypoxic hazards of traditional paper bag rebreathing in hyperventilating patients

It is traditional practice to treat acute hyperventilation (thought to be due to anxiety) by having patients rebreathe into a brown paper bag. The author reports three cases in which this treatment, erroneously applied to patients who were hypoxemic or had myocardial ischemia, resulted in death. This clinical experience motivated a study of the effects of paper bag rebreathing in normal volunteers. Subjects deliberately hyperventilated to an average end-tidal CO 2 concentration of 21.6 (SD, 3.2) mm Hg and then continued to hyperventilate into a no. 4 Kraft brown paper bag containing the calibrated sensors for a Hewlett-Packard 47210A capnograph and a Teledyne TED 60J digital oxygen monitor. Fourteen men and six women with an average age of 36 years (SD, 6.1) were tested. Results are reported as mm Hg. After 30 seconds of rebreathing, mean change in O 2 from room air was −15.9 (SD, 4.6) and mean CO 2 was 38.7 (SD, 6.2); at 60 seconds, −20.5 (6.0) and 40.2 (6.4); at 90 seconds −22 (6.8) and 40.5 (6.4); at 120 seconds −23.6 (6.8) and 40.7 (6.5); at 150 seconds −25.1 (1.2) and 41 (7.3); and at 180 seconds −26.6 (8.4) and 41.3 (7.5). A few subjects achieved CO 2 levels as high as 50, but many never reached 40. The mean maximal drop in O 2 was 26 (8.8); seven subjects had drops in oxygen of 26 mm Hg at three minutes, four had drops of 34 mm Hg, and one had a drop of 42 mm Hg. Three subjects rebreathed into an 18-L plastic bag filled with 100% O 2 , but although CO 2 rapidly exceeded 40, O 2 levels reached 21% within two to four minutes and continued to decline to less than 10% at 15 minutes. Paper bag rebreathing decreases inspired oxygen sufficiently to endanger hypoxic patients. Paper bag rebreathing should never be administered unless myocardial ischemia can be ruled out and the patient's oxygenation has been directly measured by arterial blood gases or pulse oximetry Since these conditions are impossible to achieve outside the hospital, its recommendation and use by prehospital personnel should be abandoned, and its use in hospital probably should be diminished.