Related Experiment Video
Updated: Jul 13, 2026
09:22
Quantitatively Measuring In situ Flows using a Self-Contained Underwater Velocimetry Apparatus (SCUVA)
Published on: October 31, 2011
Influence of bottom time on preflight surface intervals before flying after diving
R D Vann1, N W Pollock, J J Freiberger
1Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC 2 7710, USA.
Summary
Divers flying after scuba diving require shorter preflight surface intervals (PFSI) for shorter, simpler dives. Shorter PFSIs are needed for 40-minute dives compared to 55-minute dives, and for single decompression dives versus repetitive dives.
Area of Science:
- Diving Medicine
- Hyperbaric Physiology
Background:
- Previous research indicated low risk of decompression sickness (DCS) after a 55-minute air dive with an 11-hour preflight surface interval (PFSI).
- Repetitive dives with longer bottom times (75-95 minutes) at the same depth necessitated significantly longer PFSIs (16 hours).
Observation:
- Trials investigated PFSIs for a 60 feet seawater (fsw), 40-minute no-stop dive and a 60 fsw, 120-minute decompression dive.
- For the 40-minute dive, PFSIs were reduced from 12 hours to 5 minutes, resulting in 3 DCS incidents.
- For the 120-minute dive, PFSIs were reduced from 22.75 hours to 2 hours, leading to 9 DCS incidents, with 6 incidents occurring at a 2-hour PFSI.
Findings:
- Low-risk PFSIs for the 40-minute dive were nearly 12 hours shorter than for the 55-minute dive.
- Low-risk PFSIs for the single 120-minute decompression dive were 12 hours shorter than for the 75-95 minute repetitive dives.
- Under dry, resting conditions, low-risk PFSIs are sensitive to dive profile characteristics like bottom time, repetitive exposures, and decompression stops.
Implications:
- Dive profile complexity significantly impacts the required preflight surface interval to mitigate decompression sickness risk.
- Current US Navy guidelines may overestimate required PFSIs for simpler dive profiles.
- Further research is needed to determine if these findings apply to wet, working dive conditions.
More Related Videos
Related Concept Videos
01:26Influence of Earth's Curvature and Atmospheric Refraction on Leveling
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance. Over a...
01:04Hydrostatic Pressure Force on a Plane Surface
When a plane surface is submerged in a fluid, hydrostatic forces develop on the surface due to the fluid's pressure. For horizontal surfaces, the pressure exerted by the fluid is uniform because the depth remains constant. The resultant force is determined by the pressure at the given depth multiplied by the area of the surface, and it acts through the centroid of the surface. For vertical surfaces, the pressure varies with depth, increasing as the distance from the fluid's free surface...
01:29Application of Linearization and Approximation
A drone flying through complex terrain often relies on more than one sensing method to estimate small changes in altitude. Along with direct measurements, air pressure provides a useful indirect indicator of vertical movement. Atmospheric pressure decreases as altitude increases, and this relationship is commonly described using an exponential model. Although accurate, converting pressure measurements into altitude values requires calculations that are too complex to perform repeatedly during...
01:18Boundary Layer Characteristics
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...
01:11Buoyancy and Stability for Submerged and Floating Bodies
In fluid mechanics, buoyancy and stability are key concepts for understanding the behavior of submerged and floating bodies. When a stationary body is fully or partially submerged in a fluid, the fluid exerts a force on the body known as the buoyant force. This force acts vertically upward through a point called the center of buoyancy, which is the center of the displaced fluid volume. According to Archimedes' principle, the magnitude of the buoyant force is equal to the weight of the fluid...
01:14Testing Water Quality
When the quality of water for concrete preparation is uncertain, its impact on the setting time of cement and compressive strength of mortar is assessed by comparison with de-ionized or distilled water benchmarks. American Society for Testing and Materials (ASTM) C1602 requires the setting times to be within 90 minutes of the control, British Standard (BS) 3146:1980 allows a 30-minute variance in the initial setting, while British Standards European Norm (BS EN) 1008 specifies initial setting...