Heart rate variability in novice pilots during and after a multi-leg cross-country flight

A pilot's workload induces autonomic nervous system modulations which could be related to a decrease of vigilance that could impair safety. Kinetics during flight and recovery are not well known.

The aim of this study was to assess linear and nonlinear heart rate variability (HRV) modulations and vigilance during a high mental workload induced by a complex flight and subsequent recovery.

There were 10 novice pilots (37.8 +/- 4.4 yr, 115.8 +/- 15.7 h flight experience) who performed a 3 h 30 min (09:30-13:00) multi-leg cross-country flight (Piper Pa28 airplane: 160 hp). We recorded electrocardiogram (ECG) during the flight and performed tests during the 24 h before and after the flight (13:30, 16:00, 18:30, 21:00, and 06:45). Tests included a stand test (10 min supine, 10 min standing), a Mackworth 'clock' vigilance test, and a Karolinska Sleepiness Scale questionnaire. We assessed HRV components by time and frequency domains in parallel with the Poincaré plot analysis.

The flight induced a progressive decrease of RR intervals, standard deviation between normal-to-normal intervals (SDNN), Poincaré SD1 and SD2 indices, and an increase of the low-frequency to high-frequency ratio (LF/HF). During recovery, vigilance remained depressed for 2 h 30 min after the flight. The decreased RR intervals and SD1 persisted for 5 h postflight both in supine and standing positions. LF/HF stayed elevated for 2 h 30 min after the flight.

A multi-leg cross-country flight involves a vagal withdrawal and an increase of sympathetic activity lasting 5 h after landing. This delay could be recommended as a safety period.