Premature ventricular contractions during +Gz with and without pressure breathing and extended coverage anti-G suit.
BACKGROUND: High +Gz is known to provoke cardiac dysrhythmias. Pressure breathing during G (PBG) and extended coverage anti-G suits (ECGS) are used to enhance +Gz-endurance and reduce fatigue during high +Gz flying. It is not known whether PBG in combination with ECGS increases the risk for premature ventricular contractions (PVC). HYPOTHESIS: PBG in combination with ECGS increases the risk of PVCs during high +Gz-loads. METHODS: Retrospective data were obtained from 14 subjects exposed to three different simulated aerial combat sorties each, in the centrifuge with a standard anti-G suit ensemble or with PBG in combination with ECGS. Each sortie consisted of a gradual onset G-exposure (GOR) and three simulated aerial combat maneuvers (SACM) containing four cycles of a +4.5 to +7 GzSACM; four cycles of +4 to +9 Gz tactical aerial combat maneuver (TACM) with several rapid transitions from +4 or +5 Gz to +8 or +9 Gz; and four cycles of +5 to +9 Gz SACM (5-9 SACM) with four cycles. ECG was recorded during the +Gz exposures to reveal any cardiac dysrhythmias. RESULTS AND CONCLUSIONS: No PVCs occurred during the GORs. During 4.5-7 SACMs, TACMs, and 5-9 SACMs there were 83, 50, and 24 PVCs with standard equipment, respectively, and 63, 54, and 39 PVCs with PBG and ECGS, respectively. There was no statistically significant difference between the equipment in any of the different types of +Gz exposures. No episodes of supraventricular tachycardia or relative bradycardia were found with either equipment.