Chest
Volume 87, Issue 3, March 1985, Pages 330-333
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High Altitude Pulmonary Edema and Exercise at 4, 400 Meters on Mount McKinley: Effect of Expiratory Positive Airway Pressure

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Breathing against positive expiratory pressure has been used to improve gas exchange in many forms of pulmonary edema, and forced expiration against resistance during exercise has been advocated for climbing at high altitude as a method to optimize performance. To evaluate the effect of expiratory positive airway pressure (EPAP) on climbers with high altitude pulmonary edema (HAPE) and on exercise at high altitude, we studied four climbers with HAPE at rest and 13 healthy climbers during exercise on a bicycle ergometer at 4400 m. We measured minute ventilation (V˙I, L/min), arterial oxygen saturation (SaO2 percent), end-tidal carbon dioxide (PACO2, mm Hg), respiratory rate (RR), and heart rate (HR) during the last minute of a five minute interval at rest in the climbers with HAPE, and at rest, 300, and 600 kpm/minute workloads on a bicycle ergometer in the healthy subjects. The HAPE subjects demonstrated an increased SaO2 percent, no change in HR orV˙I, and a decrease in RR on EPAP as compared to control. In normal subjects, SaO2 percent,V˙I, and heart rate were significantly higher on EPAP 10 cm H2O than 0 cm H2O control (p<0. 01, 0. 01, and 0. 05, respectively). The RR and PaCO2 were not significantly different. In summary, EPAP improves gas exchange in HAPE subjects at rest. The EPAP in normal subjects at high altitude resulted in a higher SaO2 percent at the expense of a higherV˙I and higher HR. These results suggest that the work of breathing is higher and the stroke volume lower on EPAP. The positive pressure mask may be an effective temporizing measure for victims of HAPE who cannot immediately go to a lower altitude.

Section snippets

Subjects

Subjects were volunteers from climbers on Mt McKinley in the months of May and June, 1983. They gave informed consent as approved by the Human Subjects Review Committees of the Universities of Washington and Alaska. The healthy subjects consisted of 12 men and one woman (23 to 41 years). The 13 subjects (29. 7±5. 9 years) had successfully ascended to 4, 400 m or higher without symptoms of altitude illness and had resting arterial oxygen saturations (SaO2 percent) of 85 ± 3 percent. The four

RESULTS

No subjects suffered any adverse effects from the EPAP mask.

Resting SaO2 percent was significantly lower in HAPE subjects than normal subjects at all levels of EPAP (p<0. 005). Climbers with HAPE increased their resting SaO2 percent at 0, 5, and 10 cm H2O EPAP, respectively (Fig 1A). The SaO2 percent was significantly higher in normal subjects on EPAP 10 cm H2O than on EPAP 0 cm H2O at rest (p<0. 01). The SaO2 percent decreased significantly in normal subjects from rest to 600 kpm/min at each

DISCUSSION

The results of this study demonstrate that in a small number of climbers with HAPE at the same altitude at rest, increasing levels of EPAP increased oxygen saturation without increasing ventilation and changed the pattern of breathing to a higher tidal volume and lower frequency. In healthy subjects at 4, 400 m, the use of EPAP with 5 and 10 cm H2O pressure, at rest and modest workloads, increases SaO2 percent, probably because of an increased ventilation. It also raises HR. This study is the

ACKNOWLEDGMENT

This project would not have been possible without our camp managers, Brian and Diane Okonek; the enthusiastic and helpful cooperation of the climbing rangers of the US National Park Service; the skilled assistance of pilots Jim Okonek of K-2 Aviation and Doug Geeting and Lowell Thomas, Jr, of Talkeetna Air Taxi, both of Talkeetna, Alaska; the invaluable technical skills of Karl H. Maret, MD; and the literature search of Matthew Hegewald.

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  • Cited by (0)

    This study was supported by PHs NHLBI Clinical Investiator Grant HL00906 and an E. L. Trudeau Scholar Award of the American Lung Association (R.B.S.).

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