In the late 1960s single-hose regulators started to take over as the standard, and this complicated the buddy breathing procedure. The single hose exhaust valve position at the bottom of most DVs made it necessary to offset the recipient to the right side when face to face, or to the left when side by side. The standard procedure of continuous exhalation during ascent to avoid lung over-pressure injury could leave the diver with insufficient air to clear the regulator, so it was necessary to hold the DV in a way that did not obstruct the recipient from accessing the purge button, as the single hose would not normally free flow when raised above the head. The increasing popularity of the buoyancy compensator was another complication, as it is necessary to periodically vent it during an ascent to avoid a runaway expansion of the contents and an uncontrolled buoyant ascent. This requires the use of one hand. the other is needed to control the regulator and hold on to the other diver, a moderately complex set of simultaneous tasks. It is possible to coordinate these activities, but this requires greater skill than with the original procedure, and therefore more intensive training to perform reliably. Since running out of air was becoming less common, the procedure was practiced less often, and skills generally deteriorated. The use of a secondary (octopus) second stage or a bailout cylinder removes the necessity for this complex and relatively stressful procedure.