An Abrupt Zero-Preoxygenation Altitude Threshold for Decompression Sickness Symptoms
Abstract
The altitude threshold for decompression sickness (DCS) symptoms has been variously described as being 18,000 ft (5,487 m) to above 25,000 ft (7,620 m). Safety and efficiency of aerospace operations require more precise determination of the DCS threshold. One hundred fifteen male human-subjects were exposed to simulated altitude (11 at 11,500 ft; 10 at 15,000 ft; 8 at 16,500 ft; 10 at 18,100 ft; 10 at 19,800 ft; 20 at 21,200 ft; 20 at 22,500 ft; 10 at 23,800 ft, and 16 at 25,000 ft) for up to 4 h. All breathed 100% oxygen beginning with ascent. Subjects were monitored for precordial venous gas emboli (VGE) and DOS symptoms. Probit curves representing altitude versus incidence of DCS symptoms and VGE allowed estimation of respective risk. VGE were first observed at 15,000 ft with increasing incidence at higher altitudes; over 50% at 21,200 ft and at least 70% at 22,500 ft and above. DCS symptoms were first reported at 21,200 ft with an incidence of 5%. At 22,500 ft, the DOS incidence climbed to 60%. The 5% threshold for zero-preoxygenation altitude DCS symptoms is at 21,000 ft and an abrupt increase in DCS symptom incidence with increased altitude.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1998
- Accession Number
- ADA426912
Entities
People
- Andrew A. Pilmanis
- James T. Webb
- Robert B. O'connor