Heart rate and performance during combat missions in a flight simulator

INTRODUCTION: The psychological workload of flying has been shown to increase heart rate (HR) during flight simulator operation. The association between HR changes and flight performance remains unclear. METHODS: There were 15 pilots who performed a combat flight mission in a Weapons Tactics Trainer simulator of an F-18 Hornet. An electrocardiogram (ECG) was recorded, and individual incremental heart rates (deltaHR) from the HR during rest were calculated for each flight phase and used in statistical analyses. The combat flight period was divided into 13 phases, which were evaluated on a scale of 1 to 5 by the flight instructor. RESULTS: HR increased during interceptions (from a mean resting level of 79.0 to mean value of 96.7 bpm in one of the interception flight phases) and decreased during the return to base and slightly increased during the ILS approach and landing. DeltaHR appeared to be similar among experienced and less experienced pilots. DeltaHR responses during the flight phases did not correlate with simulator flight performance scores. Overall simulator flight performance correlated statistically significantly (r = 0.50) with the F-18 Hornet flight experience. CONCLUSIONS: HR reflected the amount of cognitive load during the simulated flight. Hence, HR analysis can be used in the evaluation of the psychological workload of military simulator flight phases. However, more detailed flight performance evaluation methods are needed for this kind of complex flight simulation to replace the traditional but rough interval scales. Use of a visual analog scale by the flight instructors is suggested for simulator flight performance evaluation.     

Inflight workload assessment: comparison of subjective and physiological measurements

INTRODUCTION: Assessment of pilot workload during flight is an important aviation safety consideration. The aim of this study was to assess inflight pilot workload using both physiological and multidimensional subjective-ratings measurements (heart rate and NASA Task Load Index, respectively), comparing relative sensitivity during the four phases of flight: take-off, cruise, approach, and landing. METHODS: Ten male pilots volunteered to participate in the trials, which took place in a Boeing 747-400 flight simulator. Electrocardiography was performed throughout the test using the portable Cardiovis ECG system. Mean heart rate (HR) and incremental heart rate (delta HR) were considered indices of physiological workload. RESULTS: Peak HR was observed during take-off (83.2 bpm) and landing (88.6 bpm); moreover, delta HR was also greatest (14.2 bpm and 18.8 bpm). The Task Load Index (TLX) scale revealed that mental and performance demands were essential components of workload during flight. In addition, temporal demand was an important component of workload during take-off and physical demand was significant during cruise. Analysis of correlation revealed that the delta HR is significantly related to TLX scores (r = 0.81, n = 40). CONCLUSIONS: Management of the individual sources of stress, which tend to become predominant during different flight phases, should be emphasized in periodic recurrent training. For example, a pilot must be trained to cope with the increased temporal stresses associated with take-off. In addition, the recommendations will be concerned with maintaining vigilance, task allocation between pilots, and inflight rest during long-haul cruise.     

深海实潜中下潜人员的心率变异性研究

目的研究深海实潜作业中交感-迷走神经对下潜人员心脏功能的调控作用,为评价潜航员工作负荷提供参考。方法 2名潜航员和3名技术人员(作为乘员)参加实验。每次潜航为1名潜航员操作"蛟龙号"携带1名乘员(技术支持)进行实潜作业,持续时间约11 h。记录他们在潜航前和潜航作业全程的心电图,提取R-R间期,计算心率,并对心率变异性(heart rate variability,HRV)的时域和频域指标进行计算和分析。结果下潜人员的心率都在1 h达到最大并逐渐下降,其中潜航员的心率在1 h~6 h显著高于对照水平(P0.05或P0.01),乘员的心率在1 h~4 h显著高于对照水平(P0.05或P0.01),之后均恢复到对照水平。相比于对照值,在1 h,10 h,11 h,潜航员的LF/HF升高,HF/TP降低(P0.01);乘员的SDNN在8 h、9 h和11 h显著高于对照水平(P0.01)。结论在下潜和上浮阶段,潜航员的交感神经活性升高、迷走神经活性降低,可能与这两个阶段潜航员的工作负荷较高有关。在下潜阶段下潜人员心率的显著升高提示可能存在精神紧张和应激反应。潜航过程中,潜航员的心率逐渐稳定,交感神经兴奋仍有出现,提示在评价潜航员工作负荷时,HRV可能是比心率更敏感的指标。     

高气压变化对年轻飞行员心率及短程心率变异性的影响

目的 探讨高气压变化对年轻飞行员心率(HR)及短程心率变异性(HRV)的影响.方法 利用高压舱结合动态心电图对30名年轻飞行员进行临床试验,记录升压前、升压过程中、高压状态、减压过程中及减压后各5 min的平均HR及所有正常R-R间期标准差(SDNN)、相邻正常R-R间期差值均方根(RMSSD)、相邻R-R间期差异大于50 ms的百分数(PNN_(50))3项短程HRV时域指标,并进行统计学处理.结果 气压升高可使HR减慢,升压前76.56±12.33次/min,升压过程中67.25±10.21次/min,高压状态65.06±7.02次/min;随着大气压的恢复,HR逐渐加快,但未恢复到升压前水平;主要反映交感和迷走神经总张力的HRV指标SDNN和主要反映迷走神经张力的RMSSD、PNN_(50)基本上随着环境大气压升高而升高,随着大气压降低而降低.结论 高气压的变化对年轻飞行员的HR和短程HRV有较明显的影响,在飞行员的选拔和训练时应予以重视.     

抛物线飞行前、中、后动态心电图的改变

目的了解失重飞机飞行全过程中心电活动的特点。方法记录 1 3名被试者在失重飞机飞行前、中、后的动态心电图 (DCG)。结果飞行前、后心率基本相同 ;失重飞机飞行过程中 ,被试者心率增加 ,最大心率为 1 37.0± 1 2 .2bpm ,最小心率为 57.7± 6.6bpm平均心率为 86.0± 7.3bpm ,高于一般飞行中检出的心率 ;飞行前、后 1 3名被试者心脏节律无明显差异 ;飞行中 ,仅 1例被试者心脏节律较地面训练日稍有变化。 2例在高空失重飞行中 ,ST段呈一过性水平下移≥ 0 .1mV ,1例T波改变 ,但极量活动平板试验阴性。结论DCG可用于评价整个失重飞机飞行期间心脏电活动的改变。     

模拟飞行条件下双重任务时飞行员心理生理参数的变化特点

测量了50名健康飞行员和13名康复疗养飞行员，在模拟飞行条件下双重任务时的心理生理反应。结果发现，模拟飞行各阶段心率变化趋势与实际飞行基本一致，但变化幅度较低。双重任务时，反映情绪性变化的心率、呼吸率及肺通气量明显增加，与思维活动有关的眨眼率增加。心理运动反应速度与飞行操纵质量相互影响，其程度有个体差异。同时在该负荷环境下，发现5例心律失常的无症状飞行员。结果提示，模拟飞行双重任务条件可以造成飞行员心理生理负荷，并可能有助于发现一些潜在性病症。     

地面模拟长航时飞行时飞行学员心率和心率变异性的变化

目的探讨飞行人员长航时飞行中生理变化特点,观察心理疲劳对抗措施对长航时飞行心理疲劳的缓解作用。方法20名健康男性教-8飞行学员随机分为对照组和试验组,在教-8飞行模拟器上进行8h的长航时模拟飞行。试验组在飞行中的休息阶段采取放松措施,对照组休息阶段不采取任何措施。记录飞行学员模拟飞行过程中的心电信号,分析心率、心率变异性（heart rate variability,HRV）以及体动强度。结果模拟长航时飞行中,试验组的平均心率显著低于对照组（F-184．241,P-0．000）,试验组休息时平均心率低于飞行时（F-17．564,P-0．000）;而对照组在飞行和休息时心率变化规律不明显（F-2．014,P-0．156）。对照组休息时较飞行时校正低频功率（low frequency normalized unit,LFnu）、低频高频比值（LF／HF）显著增加,校正高频功率（highfre-quency normalized unit,HFnu）显著降低。而试验组在休息时LFnu、HFnu、LF／HF指标与飞行时比较,仅第1次第有明显变化（P〈O．05）。对照组的体动强度在休息时显著高于飞行阶段,而试验组没有明显改变。结论地面模拟长航时飞行试验中,受试者的自主神经兴奋性因试验因素的变化存在明显的变化规律。从心率变化分析,地面模拟长航时飞行属于单位时问内低负荷持续作业的试验模型。在飞行中的休息阶段实施放松措施能有效缓解受试者的焦虑、烦躁情绪。HRV频域指标中,LFnu、HFnu、LF／HF可作为评价情绪负荷较为敏感的指标。     

两种情境中不同情绪稳定性个体心率变异性与心率的比较研究

目的 比较两种情境下不同情绪稳定性个体心率变异性与心率,探讨情境、情绪稳定性与心率变异性的关系。方法 96名健康男性飞行学员,在60h飞行训练后由飞行教员用飞行学员情绪稳定性评价量表进行评定,分为高情绪稳定性组与低情绪稳定性组。在Sternberg双重作业任务与标准起落飞行两种情境中,记录心率变异性指标和心率,并进行比较。结果 Sternberg双重作业任务情境中,高情绪稳定性个体具有较小的Lfnorm和Hfnorm(P＜0．05),较小的LF／HF和心率(P＜0．05)。但处于飞行情境中,高情绪稳定性个体则有较大的Lfnorm和Hfnorm,较小的LF／HF和心率(P＜0．05)。结论 与情绪稳定性相关的自主神经系统活动的波动性出现情境分离。提示个体适应外部环境的能力差异不仅体现在个性、气质和认知模式上,也存在生理基础的差异。     

EEG and ECG changes during simulator operation reflect mental workload and vigilance

BACKGROUND: Performing mission tasks in a simulator influences many neurophysiological measures. Quantitative assessments of electroencephalography (EEG) and electrocardiography (ECG) have made it possible to develop indicators of mental workload and to estimate relative physiological responses to cognitive requirements. OBJECTIVE: To evaluate the effects of mental workload without actual physical risk, we studied the cortical and cardiovascular changes that occurred during simulated flight. METHODS: There were 12 pilots (8 novices and 4 experts) who simulated a flight composed of 10 sequences that induced several different mental workload levels. EEG was recorded at 12 electrode sites during rest and flight sequences; ECG activity was also recorded. Subjective tests were used to evaluate anxiety and vigilance levels. RESULTS: Theta band activity was lower during the two simulated flight rest sequences than during visual and instrument flight sequences at central, parietal, and occipital sites (p < 0.05). On the other hand, rest sequences resulted in higher beta (at the C4 site; p < 0.05) and gamma (at the central, parietal, and occipital sites; p < 0.05) power than active segments. The mean heart rate (HR) was not significantly different during any simulated flight sequence, but HR was lower for expert subjects than for novices. The subjective tests revealed no significant anxiety and high values for vigilance levels before and during flight. CONCLUSIONS: The different flight sequences performed on the simulator resulted in electrophysiological changes that expressed variations in mental workload. These results corroborate those found during study of real flights, particularly during sequences requiring the heaviest mental workload.     

有晕厥史飞行员立位应激下自主神经功能评价

目的：评价加速度引起的意识丧失（G－LOC）或血管迷走性晕厥（VVS）飞行员在立位耐力试验（OTT）条件下自主遥作用。方法：对30例晕厥并阳 性OTT病例组（I组），20例晕厥并阴性OTT病例组（Ⅱ组）和15例年龄，性别，飞行机种，飞行时间相匹配的健康飞行员（对照组）的心率变异（HRV）和OTT的关系进行研究，对所测量OTT前后心率（HR），收缩压（SBP），舒张压（DBP）和HRV指标进行对比分析。结果：3组被试者OTT前平均HR，SBP，DBP比较无显著性差异（P＞0．05），OTT后I组HR明显高于其他两组（P＜0．01），SBP和DBP明显低于其他两组（P＜0．01），HRV指标中I组24h连续RR间期标准差（SDNN），HRV三角指数（HRVI），RR间期平均值（RR）明显小于其他两组（P＜0．01），平均1h 功率谱分析I组低频成分／高频成份比值（LF／HF）明显高于其他两组（P＜0．05），结论：晕厥并阳性OTT飞行员立位应激下交感神经张力增强，副交感神经张力减弱，使自主神经功能失调。     

累加角度头高斜位下心率、血压、心率变异性与脑血流变化的特征

目的探讨累加角度头高斜位暴露下 ,正常人体血压、心率、脑血流及心率变异性 (HRV)变化特征 ,为建立飞行员晕厥检查的方法学提供生理依据。方法采用自行研制的多功能双向式医用倾斜床 ,结合先进的十二导联同步心电图描记方法和经颅多普勒脑血流成像技术进行累加角度 ( + 4 5°→ 60°→75°)头高斜位 (HUT)暴露下的心率、血压、HRV和脑血流速率的测量与分析。结果 1 )随着倾斜角度加大 ,暴露时程延长 ,HR逐渐增快 ,SBP逐渐下降 ,DBP逐渐升高 ,PP逐渐缩小 ,与暴露前比较 ,HR、PP和DBP相差非常显著 (P <0 .0 5 ) ;脑血流速率 (包括 :Vs、Vm、Vd)逐渐下降 ,无论与暴露前比 ,或倾斜角度之间比 ,差异十分显著 (P <0 .0 1 ) ;mRR和sdRR逐渐减小。 2 )生理指标与技术指标直线相关分析发现 :在 1min时 ,SBP、DBP、MAP、Vd、sdRR与倾斜角度呈明显正相关 (P <0 .0 1 ) ;在 2 0min时 ,HR和sdRR与倾斜角度呈明显正相关 (P <0 .0 1 ) ,与SBP、PP、Vs、mRR明显负相关 (P <0 .0 1 ) ;暴露时程与HR呈明显正相关 (P <0 .0 1 ) ,与SBP、Vm、Vd、mRR呈明显负相关 (P <0 .0 1 )。 3)生理指标间相关分析发现 :HR与SBP、Vs、Vm、Vd 呈明显负相关 (P <0 .0 1 ) ;SBP与Vd 和mRR呈明显正相关 (P <0 .0 1 ) ;Vs、Vm、Vd 与mRR和sdR     

高性能战斗机大强度飞行对飞行员生理指标及飞行劳动负荷主观评价的影响

目的观察高性能战斗机大强度飞行对飞行员的生理指标及飞行劳动负荷主观评价的影响。方法5名健康男性高性能战斗机飞行员在1个飞行日内共进行22架次的大强度飞行。记录飞行过程中的心电信号,分析心率及心率变异性（heart rate variability,HRV）;飞行后进行飞行劳动负荷和疲劳程度主观评价。结果飞行员大强度飞行时,随着飞行负荷的降低,心率和HRV频域及时域指标呈现一定的规律性变化。心率在夜问较日问低;夜间校正高频功率（high frequency normalized unit,HFnu）高于日间,校正低频功率（low frequency normalized unit,LFnu）及低频高频比值（LF／HF）则低于日问。飞行员飞行劳动负荷及疲劳程度主观评价分值均较低,没有明显的主观疲劳感。结论高性能战斗机大强度飞行对飞行员生理指标有一定影响,但尚未引起飞行疲劳。合理的飞行安排及有力的航卫保障有利于飞行员身体机能的恢复,预防飞行疲劳,保障飞行安全。     

飞行员返回抑制的时程特征及其与飞行绩效相关的研究

目的研究飞行员返回抑制(inhibition of return,IOR)时程特征,并探讨其对飞行绩效的影响,为飞行员的训练和选拔提供参考依据。方法采用线索-靶子范式中的辨别任务形式对32名飞行员进行实验。结果熟练飞行员在SOA为800 ms出现返回抑制(P<0.05),优秀飞行员在SOA为600 ms和800ms出现返回抑制(P<0.05),新手飞行员在SOA为400 ms出现易化效应(P<0.05),在600 ms和800ms均未出现返回抑制;优秀飞行员比新手飞行员拥有更强的返回抑制能力,他们能在较短SOA里出现IOR特征。所有飞行员在400 ms、600 ms和800 ms的返回抑制效应值与飞行绩效相关显著(r=0.601～0.639,P<0.01)。结论优秀飞行员更早出现返回抑制,返回抑制能力和飞行绩效相关,对飞行绩效的评估具有一定的参考价值。     

飞行训练对飞行员HR、QTc、QTd的影响

目的：探讨飞行训练对战斗机飞行员HR、QTc、QTd的影响。方法：应用12通道同步心电图记录仪,对40名飞行员按不同分组测定飞行训练前后HR、QTc、QTd并加以对比分析。结果：飞行员HR飞后10 min、一次飞后10 min、二次飞后10 min、昼航后10 min、5G载荷飞后10 min、5 km飞后10 min与飞前比较差异有统计学意义（P〈0.05）;不同飞行场次、不同飞行强度、不同飞行载荷、不同飞行高度QTc、QTd飞前后无变化（P〉0.05）。结论：HR的变化取决于飞行员对飞行应激的适应能力,与飞行负荷、飞行时间呈正相关性。     

Validity of the polar S810 to measure R-R intervals in children

Intervals between two consecutive cardiac beats (R-R intervals) and the subsequent analysis of heart rate variability (HRV) obtained simultaneously from the Polar S810 heart rate monitor (HRM) and an electrocardiogram (ECG) in a supine position were compared in twelve children (age 9.6 +/- 0.9 years) before and after protocol correction. R-R intervals were significantly different between the ECG and the HRM uncorrected and corrected signal (p < 0.001, effect size [ES] = 0.005, and 0.005, respectively). However, the bias (95 % confidence interval) was 0.80 (- 124.76 - 123.16) ms and 0.80 (- 12.76 - 11.16) ms, respectively. HRV parameters derived from both signals were not different (p > 0.05) and well correlated (r > 0.99, p < 0.05), except SD2 (p < 0.05, ES = 0.000; r = 0.99). These data support the validity of the Polar S810 HRM to measure R-R intervals and make the subsequent HRV analysis in a supine position in children.     

心率变异性分析的新指标及其在航空医学中的应用

目的通过对２４ｈ心率变异性（ＨＲＶ）谱成分极低频（ＶＬＦ）、低频（ＬＦ）与高频（ＨＦ）功率之间的关系进行回归分析，探讨回归方程各参数的病理生理意义及其在飞行员心功能鉴定中的价值。方法对象为健康女飞行员３０名、年龄相当的男飞行员３０名、可疑冠心病飞行员８例、确诊的冠心病人２０例。采用２４ｈ全信息动态心电图仪。分析指标：ＶＬＦ（０．００３Ｈｚ～０．００４Ｈｚ）、ＬＦ（０．０４Ｈｚ～０．１５Ｈｚ）、ＨＦ（０．１５Ｈｚ～０．４０Ｈｚ）和总体平均功率（０．００３Ｈｚ～０．４０Ｈｚ，ＴＦ），回归分析各频率间的关系，并进行ｔ检验。结果①ＶＬＦ和ＬＦ与ＨＦ均呈显著负相关；ＶＬＦ与ＨＦ的相关系数值（ｒ）显著大于ＬＦ与ＨＦ的相关系数值。②ＶＬＦ和ＬＦ与ＨＦ回归方程的斜率（Ｂ）、相关系数（ｒ）以及ＨＦ值均表现为夜间大于白天，女性大于男性，健康飞行员大于冠心病人。结论ＶＬＦ可能反映交感神经系统活性；ＶＬＦ或ＬＦ与ＨＦ回归方程的斜率可反映交感神经系统与副交感神经系统的均衡性，相关系数可反映二者的拮抗性与协调性。女飞行员的夜间迷走神经活性高于男性飞行员；冠心病人可表现有交感神经系统与副交感神经系统的协调性降低，以及迷走神经活性受损     

Visual neglect: occurrence and patterns in pilots in a simulated overnight flight

INTRODUCTION: Visual neglect is the unconscious inability to recognize or acknowledge some visual information in the presence of a structurally intact visual system, and was hypothesized to occur with less than 24 h of continuous wakefulness. Visual perception was evaluated in military pilots during a simulated overnight flight to explore for the possible occurrence of visual neglect. METHODS: There were eight military pilots (male, 31-52 yr of age, mean 37 yr) on flight status who were recruited to perform the primary task of flying a simulated 12.5 h overnight mission after a day of continuous wakefulness and the secondary task of responding to repeated 20 min presentations of single- and double-light stimuli displayed in random sequence at 15 degrees intervals across the cockpit instrument panel. In addition to the visual performance task, simulator shutdowns occurring when the tolerances of the simulator were exceeded were measured and simple reaction time on the psychomotor vigilance task was assessed. Total continuous wakefulness was 26.5 h. RESULTS: Combined performance on the visual perception task showed response omissions increasing at 19 h of continuous wakefulness. Patterns included omissions at all stimulus locations, of primarily peripherally located stimuli, and of one of two simultaneously presented stimuli. Simulator shutdowns began at 21.5 h of continuous wakefulness. Correlation of visual task response omissions with simulator shutdowns was r = 0.95, p < 0.0001. CONCLUSIONS: Significant neglect of visual stimuli occurred in pilots beginning at 19 h of continuous wakefulness in a simulated overnight fixed wing aircraft flight, preceded simulator shutdowns, and correlated at 0.95 with simulator shutdowns.     

用微动敏感床垫监测睡眠的研究

目的研究一种能对飞行员睡眠状况进行常年监测的技术途径。方法为了不在受试者身上粘贴电极进行睡眠分期,笔者在既往从心率变异性提取睡眠信息的基础上,研制了微动敏感床垫睡眠监测系统。该系统可以从床垫上采集信号,采用以小波分析为主的信号处理技术,逐拍分析受试者心动周期的变异性。用它在２４名正常人身上进行了睡眠监测,同时记录ＥＥＧ,ＥＣＧ作为对照。结果用床垫及小波分析技术可以准确地获得逐拍心动周期信息。通过逐拍心动周期变异分析,可获得较为准确的基本睡眠分期,和脑电波分析结果相比,符合率达０．８５２。讨论本系统对受试者干扰小,操作方便,容易被接受。对本项技术可运用到航空卫生保障工作的其它诸多方面以及本系统当前存在的主要不足及解决途径进行了讨论。     

The effect of age and gender on heart rate variability after endurance training

PURPOSE: This research investigated the age and gender differences in cardiovascular adaptation to a standardized/quantified endurance-training program that included two taper periods. METHODS: The latter was analyzed from spectral analysis of electrocardiogram records of heart rate variability (HRV) at rest in groups of young (19-21 yr) and middle aged (40-45 yr), mixed gender groups (6 males and 6 females), pre- and poststandardized training. All subjects were recreational runners who completed the same 12-wk running program. Before, and subsequent to training, HRV was measured during supine rest and submaximal cycling. RESULTS: There was a significant decrease in heart rate both at rest (2.7 +/- 0.45 beats x min-1) and during submaximal exercise (8.1 +/- 0.67 beats x min-1) in both age groups after training. After training, total spectral power increased (560.7 +/- 308.9 ms2), as well as high-frequency power (362.3 +/- 405.5 ms2), in both age groups at rest. The young group showed a greater increase in total power (849.0 +/- 308.7 ms2) after the training program. CONCLUSION: It is concluded that a well-designed 12-wk endurance-training program will decrease resting and submaximal heart rate in both younger and older adults. The significant increase in HRV, total power, and high-frequency power in all groups after endurance training indicates that HRV measurement appears to provide an effective, noninvasive assessment of cardiovascular adaptation to aerobic training.     

Cardiac arrhythmias in F-16 pilots during aerial combat maneuvers (ACMS): a descriptive study focused on G-level acceleration

INTRODUCTION: It is well known that acceleration during centrifuge training provokes cardiac arrhythmias. However, there is little research regarding cardiac arrhythmia during actual flight. Therefore, to identify the kinds of cardiac arrhythmias that occur in response to the Aerial Combat Maneuvers (ACM) environment, we analyzed electrocardiograms (ECG) of 35 male pilots. METHODS: ECGs were recorded from 35 pilots (mean age 31 yr, range 27-39) from 1 h before take-off to 1 h after landing. G-load was simultaneously recorded. To see the patterns of the arrhythmia as Gz force increased, ECG data of each subject were classified into three G levels: a) G-level A was < +3 G; b) G-level B was > or = +3 G but < +6 G lasting longer than 3 s; and c) G-level C was > or = +6 G lasting longer than 3 s. RESULTS: Mean total flying time of the 35 pilots was 1475 h (range 578-3300). Arrhythmias were observed in 17 of the pilots (49%) during ECG recording. Four pilots (11.4%) experienced arrhythmias before take-off, 16 pilots (45.7%) inflight and 4 pilots (11.4%) after landing. Arrhythmias were recorded in 13 of 35 pilots (37.1%) at G-level A, in 10 of 35 pilots (28.6%) at G-level B and in 1 of 21 pilots (5%) at G-level C. During flight, unifocal premature ventricular contractions (PVC) were experienced by three of the subjects (8.6%); supraventricular premature beats (SVPB) by four subjects (11.4%), and PVCs with bigeminy by one subject (2.9%). Eight subjects (22.9%) experienced combined arrhythmias. CONCLUSION: There were no clinically significant arrhythmias recorded during ACM in these experienced pilots.