Analysis of incapacitation during +Gz induced loss of consciousness

Introduction: Occurrence of G induced loss of consciousness (G-LOC) during centrifuge training is a known entity. The Indian Air Force is currently undertaking high G training of its fighter pilots in High Performance Human Centrifuge (HPHC) which has significantly higher operational capabilities. The study aimed to analyse the incapacitation periods and myoclonic jerks associated with G-LOC occurring during HPHC training. Material and Methods: Records of episodes of 161 G-LOC during closed loop Rapid Onset Rates (ROR) runs over a period of 7 years from 2011 to 2017 were analyzed. The video recordings of these G-LOC episodes were assessed in terms of the participant demographics, +Gz onset rates, incapacitation periods, and presence or absence of myoclonic jerks during the G-LOC episodes. Descriptive statistics was applied to analyze the incapacitation periods and the duration of the myoclonic flail movements. Single tailed t-test was used to analyze the difference between the incapacitation periods of the aircrew who suffered myoclonic flail movements and those who did not. One-way ANOVA was carried out to assess the differences in incapacitation periods, if any, between aircrew of different age groups. Significance was set at P < 0.05. Results: Of these 161 episodes of G-LOC, 43.5% were seen in trainee aircrew. The mean Absolute Incapacitation Period (AIP), Relative Incapacitation Period (RIP) and Total Incapacitation Period (TIP) was 6.9 ± 2.3 s, 12.2 ± 4.7 s, and 19.1 ± 5.5 respectively. Age and flying experience did not show any significant effect with any of the incapacitation periods (p>0.05). The TIP correlated better with the RIP than with the AIP (Pearson’s correlation values of 0.9 and 0.52 respectively). Myoclonic flail movements were witnessed in 25.5% of G-LOC episodes with an average duration of 5.3 s and more than 50% occurring at ≥8Gz. The mean duration of RIP was significantly higher (P=0.03) when G-LOC was associated with myoclonic flail movements, whereas, the duration of AIP did not show any significant difference. Conclusion: The shorter incapacitation periods observed in the study compared to that reported in most of the previous studies could be attributed to the faster Gz offset rates of the present HPHC. Episodes of G-LOC having myoclonic movements were found to have higher relative incapacitation periods. Even though these movements were associated with G-LOC occurring at higher Gz levels, the durations were independent of the Gz levels.

Patient satisfaction survey: A gateway to quality improvement in primary healthcare in the IAF

Patient satisfaction is an important indicator to assess and improve quality of healthcare services. In Armed Forces Medical Services, studies on patient satisfaction are scant and mainly hospital based. Hence, a study was conducted with an objective to assess patient satisfaction in seven Primary Healthcare Delivery Centers (PHDCs) in one of the operational commands in the Indian Air Force (IAF). Patient Satisfaction Questionnaire Short Form 18 (PSQ-18), a simple tool, was used for the survey. The study was unique in the sense that few centers in the survey were remotely located from tertiary care hospitals and the Medical Officers in these PHDCs were relatively inexperienced. The analysis of the survey clearly brought out distinct differences in certain dimensions of patient satisfaction across the PHDCs. In addition, utility of the Hindi translated version of PSQ-18 was ascertained. Based on the results of the study, few important conclusions were drawn; (a) patient satisfaction could be assessed using simple questionnaire such as PSQ-18, (b) the Hindi translated version of PSQ-18 can also be used as a useful tool depending on the participants’ preference, and (c) the observed dimensions affecting patient satisfaction could be addressed through specific interventions. Similar survey is recommended to be conducted across primary, secondary, and tertiary healthcare establishments in the IAF.

Incidence and transmission dynamics of Coronavirus Disease 2019 (COVID-19) among fresh recruits in a Training Establishment of Indian Armed Forces: An observational study

Introduction: In times of COVID-19, when all institutions remained closed even post lock-down, the Airmen Training School of Indian Air Force proceeded with the recruitment of airmen. The present study intends to explore the incidence and transmission dynamics of COVID-19 among these freshly recruits who were quarantined in barracks with each barrack serving as one cohort. Material and Methods: In an observational study, 2978 male Air Force recruits, between the age group of 18-22 years, in two batches between 1st to 31st July 2020, were followed up in the quarantine period post recruitment. Since the quarantine was unconventional in terms of being in barracks, special and unique precautions such as repeated screening, delegation of specific toilets per billets, three ply mask distributions, Bio-Medical Waste Disposal etc were paid utmost attention. The COVID 19 cases were treated at the in-house isolation facility and the contacts with the symptomatics tested with RT-PCR or RAT before release from quarantine. All individuals were monitored with active surveillance and the data was meticulously maintained with zero attrition. Incidence, Secondary Attack Rate (SAR), demographic characteristics and others aspects of transmission dynamics were analyzed. Results: The incidence and SAR was observed to be 8.1% (71 primary cases) and 15.59% (170 secondary cases). 64.7% of cases were symptomatic with an average of 15 days of hospitalization. The rate positivity of testing with RTPCR or RAT was 11.44%. Severity was more marked in the first batch than the second batch of recruits. The overall R0 was found to be 2.39. Conclusion: The results of the study revealed some interesting characteristics of COVID-19 transmission dynamics. The cumulative incidence was found to be higher than national average. The variations between the recruits from different part of the country and the two batches could be attributed to the travel distance and mode of conveyance. The study also validates the mild nature of the infection in young adults. Fair conclusion on the implication of good quarantine and isolation measures and regular surveillance for symptoms for early diagnosis has also been compellingly indicated from these observations.

Effects of whole body vibration on human contrast sensitivity function

Introduction: Vibration is a known aeromedical stressor in rotary-winged aircraft and is known to affect visual acuity (VA). In aerospace operational conditions, contrast sensitivity (CS) takes the upper hand over VA for optimal visual performance. Examination of the effects of low frequencies whole body vibration of short duration on CS was the desired objective of the study. Material and Methods: Thirty healthy volunteers were exposed to low frequency whole body vibration using Multi-axial Vibration Simulator. Vibration frequency along the Z-axis varied from 4 to 20 Hz over a period of 30 min. CS was recorded in no vibration, under vibration and 30 min following exposure to vibration using CSV-1000 equipment at spatial frequencies of 3, 6, 12, and 18 cycles per degree (cpd). Results: CS, after an initial degradation, gradually improved with the increase in frequencies of vibration for the lower spatial frequencies (3, 6 cpd). The increasing trend was also noticed for higher spatial frequencies (12, 18 cpd) till 16 Hz; thereafter, a significant dip (P = 0.048) was observed at 20 Hz of vibration. No significant difference was observed following 30 min of post exposure. Conclusion: In contrast to the popular belief, an improvement in CS with increasing frequencies of vibration could be concluded from the results of the study. However, the sudden decrement in CS at higher CPD at higher frequencies of vibration could adversely affect visual performance of an aircrew.

Cardiopulmonary responses to centrifuge simulated parabolic flight

Introduction: Parabolic flights, by producing short periods of weightlessness, closely simulate microgravity. However, they are still expensive, incur a significant logistics support, and occurrence of any adverse events during such simulation is undesirable. The present study was formulated to explore the feasibility of using a human centrifuge for simulation of parabolic flight to study the cardiopulmonary parameters as an alternative ground-based model. Material and Methods: Twelve healthy male volunteers were subjected to simulated parabolic flight, the profile of which involved exposure to 20 repetitions of hypogravity periods (+0.5 Gz), each interposed between periods of hypergravity phases (+2 Gz), using high-performance human centrifuge. Heart rate (HR), respiratory rate (RR), and arterial oxygen saturation (SpO2) were studied during such a simulation and analyzed using one-way repeated measures ANOVA. Motion sickness assessment questionnaire was administered to the participants after the run. They were also asked to rate their subjective feeling of weightlessness experienced during the run. Results: Comparison of HR revealed a significant difference (F = 22.167, P < 0.001) across 20 loops of different gravity phases. Post hoc analysis revealed that the mean HR of hypergravity phases was significantly higher compared with pre-run 1 G values and that of hypogravity phases. Similarly, HR showed a significant difference across pre-run 1 G, 10th and 20th loops of hypogravity phases (F = 5.672, P = 0.01). Post hoc analysis revealed a significant reduction in HR at 20th loop compared to both pre-run 1 G (P = 0.023) and 10th loop (P = 0.042) values. No significant differences were observed in both RR (F = 1.789, P = 0.148) and SpO2 (F = 1.708, P =0.199) across different gravity phases. The mean overall motion sickness score was found to be 23.6%. Participants rated their subjective feeling of weightlessness between 4 and 6 (mode = 5) on a scale of 1–10. Conclusion: It can be concluded from the results that HR increased during hypergravity conditions and reduced during hypogravity conditions, an expected outcome during parabolic flight. The significant reduction in HR during the 20th loop of hypogravity phase compared to 10th loop and pre-run 1 G conditions indicate a possible association with the duration of exposure. The centrifuge simulated parabolic flight profile designed in our study was able to emanate physiological changes similar to those experienced in actual parabolic flight for HR, RR, and SpO2.

Effects of post short nap sleep inertia on cognitive and psychomotor task performance

Introduction: Sleep inertia, a detrimental effect of daytime nap, may affect cognitive functions following awakening. The present study aimed to assess the effects of sleep inertia on cognitive and psychomotor tasks following short nap of 30 min taken in the afternoon hours, a realistic probability in the aerospace operational environment. Material and Methods: In a repetitive measure design, 30 healthy male volunteers having adequate sleep the previous night, were tested for changes in cognitive and psychomotor performance following 30 min of nap after lunch at the Sleep-cum-Group confinement lab. Post nap longitudinal testing for dual task (DT) test and Stroop test was carried out in periodic intervals for 40 min. DT response time (DTRT), DT lag error (DTLE), DT correct clicks (DTCC) and response time difference (Stroop Effect [SE]) were analyzed as performance measures. Results: There was a significant increase in DTRT (χ2 =11.13, P = 0.011) in the post-nap period as compared to pre-nap baseline values. No significant changes were observed in other parameters vis DTLE, DTCC, and SE. Post-hoc analysis revealed that the increase of DTRT was significant at 6 min post-nap session; following which the changes were not statistically significant. Conclusion: Sleep inertia was found to affect speed component of the task rather than accuracy in a post-nap period of 30 min. The effect was significant at 6 min following awakening and after that, the effects got dissipated. Although nap can be an effective strategy for sleep-alertness management, the effects of sleep inertia have to be borne in mind, especially during sustained military operations.

Retrospective study of Parajump injuries in Indian Armed Forces

Introduction: A number of studies on military and civil parachuting injuries have been published in the past. Most of the studies place the incidence of parachuting injuries to vary between 0.22% and 0.89%. The profile of injuries sustained during jumps by Indian paratroopers from Paratrooper Training School (PTS), Agra, between 2013 and 2019 was analyzed. Material and Methods: A retrospective analysis of Indian military parachuting injuries was done to assess injury patterns from the records of static line and combat free fall jumps, available at the PTS. The data pertaining to 270 injuries sustained from 256 jumps were analyzed in terms of number of jumps by each paratrooper, type of course/ mission, age, time of the of jump (day/ night), type of parachute used, wind speed at the time of drop, terrain on which the paratrooper landed, the location / part of body injured, the diagnosis, and finally the possible modality of injury using descriptive statistics. Results: The incidence of injuries ascertained from the records varied from 0.054% to 0.10% with a mean incidence of 0.083% from 306,986 jumps recorded over 7 years. Most injuries were related to refresher jumps and static line jumps. There were three fatalities recorded in this period, all due to failure of main and standby parachutes. Most of the injuries were sustained at the time of landing (218, 86.17%). Lower limb injuries accounted for maximum injuries (109, 40.37%), followed by truncal injuries 95 (35.19%) and upper limb injuries 33 (12.22%). Conclusion: The study brings out an interesting aspect of significantly less military parachuting injuries seen in the present study vis-à-vis reported in literature. A high degree of physical fitness and rigorous training are probably responsible for this low incidence. Increasing the duration of refresher training and physical conditioning may further reduce the occurrence of injuries. A cost-efficacy analysis of the same may be done before effecting changes in the training programme.

Hypoxia signature: A useful tool for hypoxia recognition among aircrew

Introduction: Hypoxia, often referred to as “silent killer,” a common aeromedical stressor in aviation, may have catastrophic events in-flight unless recognized well in time. On exposure to hypoxia, an individual manifests a specific spectrum of symptoms referred to as “hypoxia signature.” The present study was conducted to assess the manifestation of “hypoxia signature” on repeated exposure to simulated hypobaric hypoxia for its potential usage as a tool for hypoxia recognition. Material and Methods: Twenty-two healthy adult volunteers were subjected to a simulated altitude of 22,000 feet for a duration of 5 min in the hypobaric altitude chamber. The symptoms experienced by the participants at the said altitude were recorded using a questionnaire. The heart rate (HR) and oxygen saturation (SpO2) were recorded during the exposure. The hypoxia exposure was repeated two more times with a minimum interval of 3 weeks between each. Paired t-test was used to compare the mean values of physiological parameters (HR and SpO2) between ground level and 22000 feet recorded in all the three exposures. The hypoxia symptoms and their severity reported during the exposures were compared with those of recalled symptoms (reported after 3 weeks of exposure) using McNemar test and Wilcoxon Signed Rank test, respectively. Results: Paired t-test revealed a statistically significant increase in HR and fall in SpO2 with rise in altitude from ground level to 22000 feet. The three most common symptoms consistently observed were lightheadedness, thinking slow, and warm feeling. The common hypoxic symptoms and their severity scores reported at 22,000 feet compared with recalled counterpart during subsequent exposures did not reveal any significant differences (P > 0.05). Conclusion: There was a high degree of similarity in the frequency and severity score of symptoms between acute exposure to hypobaric hypoxia and recall indicating evidence of repeatability of symptoms across the three sessions of hypoxia exposure within the individuals. This brings out the usefulness of “hypoxia signature” as a tool for hypoxia recognition and its application in hypoxia indoctrination and training for aircrew.

Spacecraft launch and re-entry: Effects of simulated +Gx acceleration on cardiorespiratory parameters

Introduction: In the spaceflight, during launch and re-entry, the crew is exposed to acceleration ranging from +4Gx to +8Gx in nominal conditions. This study was conducted to assess the changes in cardiorespiratory parameters, namely, heart rate (HR), electrocardiogram (ECG), respiratory rate (RR), and SpO2 on exposure to simulated +Gx acceleration. Material and Methods: Fifteen randomly selected healthy male volunteers participated in the study. They were exposed to a simulated acceleration profile consisting of two peaks in the high-performance human centrifuge; first peak of +4Gx for 30 s and second peak of+8Gx for 30 s. The cardiorespiratory parameters were monitored and recorded during the acceleration exposure. The data were compiled and analyzed using one-way repeated measures ANOVA. Results: Significant increase in HR was observed on exposure to +4Gx (110.4 ± 16.7 bpm; P < 0.001) in comparison to the baseline value (80.5 ± 7.5 bpm). However, the changes in the HR at +8Gx were not significant in comparison to baseline as well as +4Gx values. On the other hand, RR indicated a significant increase on exposure to +8Gx (25.2 ± 5.8 breaths/min) in comparison to the baseline (15.1 ± 1.6 breaths/min; P = 0.001) and +4Gx (19.0 ± 6.1 breaths/min; P = 0.009) values. SpO2 showed a significant reduction at +8Gx (94.2 ± 3.8%) in comparison to baseline (98.9 ± 0.3%; P = 0.004) and +4Gx (96.9 ± 1.5%; P = 0.003). ECG did not show any evidence of arrhythmia during the exposure to +Gx acceleration. Conclusion: The insignificant changes in the HR at peak of +8Gx indicate less pronounced effects on the smaller hydrostatic gradient in +Gx acceleration unlike +Gz acceleration. However, the findings of the study point towards a significant increase in respiratory rate and reduction in SpO2 at +8Gx.

Lumbosacral transitional vertebra in military aviation candidates: A cross-sectional study

Introduction: Lumbosacral transitional vertebra (LSTV) is a common anomaly of the lumbosacral junction with a prevalence of 4–35.9% in various studies. Plain radiography of the spine in anteroposterior and lateral projections is done for the evaluation of the spine in candidates coming for medical evaluation for flying duties in the armed forces. Material and Methods: An observational study was conducted on the whole spine series of radiographs done at a medical selection establishment. The study population included candidates reporting to the establishment for medical examination to ascertain fitness for flying duties. In a small subset of this study population having LSTV, the Ferguson’s view was done to better delineate the lumbosacral junction. Results: The analysis revealed a total 148 cases of LSTV with a prevalence of 13.9%. Ferguson’s view, undertaken among 30 doubtful cases, confirmed the presence of LSTV in 27 cases. Type IIa was observed to be the most common pattern of LSTV followed by Type IIIb. As per the existing policy, 63.8% of candidates with LSTV were considered unfit for flying duties. Conclusion: Flying duties in the armed forces require the highest standard of physical fitness. LSTV is a very common finding during the evaluation of candidates and it is appropriate that the cases of LSTV be evaluated thoroughly. In doubtful cases of LSTV, the Ferguson’s view is a useful supplementary view as it clearly delineates the lumbosacral junction.