Manikin study showed that neonates are exposed to high sound and vibration levels during helicopter incubator transports.

AIM: This initial Norwegian study aimed to quantify the vibrations and sounds experienced by neonates when they were transported by helicopter in an incubator. METHODS: Two neonatal manikins weighing 500 and 2000 g were placed in a transport incubator and transported in an Airbus H145 D3 helicopter during standard flight profiles. The vibrations were measured on the mattress inside the incubator and the sound levels were measured inside and outside the incubator. RESULTS: The highest vibration levels were recorded during standard flight profiles when the lighter manikin was used. These ranged 0.27-0.94 m/s2, compared to 0.27-0.76 m/s2 for the heavier manikin. The measurements exceeded the action levels set by the European Union Vibration Directive for adult work environments. The sound levels inside the incubator ranged 84.6-86.3 A-weighted decibels, with a C-weighted peak level of 122 decibels. The sound levels inside the incubator were approximately 10 decibels lower than outside, but amplification was observed in the incubator at frequencies below 160 Hz. CONCLUSION: Vibrations were highest for the lighter manikin. The sound levels during helicopter transport were higher than recommended for neonatal environments and sounds were amplified within the incubator at lower frequencies.

Arterial oxygen pressure following whole-body vibration at altitude.

INTRODUCTION: Most helicopter operations are carried out at altitudes below 10,000 ft. At these altitudes, the risk of the crew experiencing hypoxia is low. For that reason, supplementary oxygen is not standard equipment on board most helicopters. Due to developments in military missions, high-altitude operations have become more frequent-as have the chances of the crew experiencing hypoxia. Helicopter crews are subjected to a higher load of whole-body vibration compared to fixed-wing aircraft crews. Whole-body vibration increases muscle work, with increased oxygen consumption as a result. We hypothesized that whole-body vibration, as experienced by helicopter crews, causes additional lowering of arterial oxygen levels under hypoxic conditions. METHODS: Data were collected from 10 subjects. They were all exposed to six different pressure altitudes in a hypobaric chamber, ranging from 1000 ft to 16,000 ft (approximately 305 m to approximately 4877 m). Arterial blood samples were drawn on two occasions at each altitude: after 14 min of rest and followed by 15 min of whole-body vibration (17 Hz, at 1.1 m x s(-2) in the z-axis) at each altitude. RESULTS: There was no significant effect of whole-body vibration on arterial oxygen pressure at altitudes up to 16,000 ft (approximately 4877 m), nor was there any effect on ventilation, seen as changes in arterial pressure of CO2. DISCUSSION: We contribute the lack of effect to the low vibration intensity used in this study. Since this vibration intensity was higher than experienced by helicopter crews during flight, we conclude that whole-body vibration does not contribute to hypoxia during high-altitude operations in helicopters.

CT examination of the pericardium and lungs in helicopter pilots exposed to vibration and noise.

INTRODUCTION: Helicopter pilots are exposed to whole body vibration and noise in their working environment. Some researchers have found that kinetic energy from both noise and vibration is believed to affect pericardial thickness and lead to pulmonary fibrosis, known as vibroacoustic disease. The aim of this project was to determine whether we could discover similar findings in a selection of helicopter pilots. METHODS: A case control study where 27 helicopter pilots were compared to an age-matched control group of typical office workers was conducted. High resolution CT scanning of the thorax was used as the diagnostic method. Two medical radiologists interpreted the images independently, blinded to whether the subjects were pilots or from the control group. RESULTS: There were no signs of pericardial thickening or significant lung fibrosis formations in either of the groups. The average pericardium thickness for the helicopter group was 1.38 mm, SD = 0.54 mm, and for the control group: 1.37 mm, SD = 0.33 mm. There was no significant correlation between pericardium thickness and flight hours or age. DISCUSSION: The average pericardial thickness values for the helicopter and the age-matched control groups were almost identical. The results are within normal limits and comparable to an American study where 21 normal individuals were measured to 1.2 mm +/- 0.8 mm in an average of 26 different points by using trans-esophageal echocardiography. CONCLUSION: On the basis of the CT scans, our findings do not support the existence of vibroacoustic disease, where pericardial thickening is the most prominent sign.

Whole body vibration in helicopters: risk assessment in relation to low back pain.

INTRODUCTION: Helicopter pilots are exposed to whole body vibration (WBV) in their working environment. WBV has been associated with low back pain (LBP) and helicopter pilots have a high prevalence for LBP compared with other professions. The aim of this study was to develop a test protocol for measuring helicopters with ISO 2631-1 and to perform a whole body vibration risk assessment based on the European Vibration Directive in a number of commonly used military and civilian helicopters. Both absolute values and individual difference in current helicopter types are of interest in order to evaluate the possible role of vibration in LBP in helicopter pilots. METHODS: In operationally relevant maneuvers, six helicopters were tested. In order to standardize measurements, each continuous flight was split into 15 separate maneuvers. A model of a working day exposure pattern was used to calculate A(8) vibration magnitudes for each helicopter. RESULTS: The vibration A(8) exposure estimates ranged from 0.32-0.51 m x s(-2) during an 8-h working day A(8). This compares with EU and ISO lower bounds risk criteria of 0.5 and 0.43 m x s(-2) A(8), respectively. DISCUSSION: Despite the vibration levels being relatively low, helicopter pilots report a high incidence of LBP. It is possible that helicopter pilot postures increase the risk of LBP when combined with WBV. The test protocol used in this study could be generally applied for other rotary winged aircraft testing to allow for comparison of WBV results. Data from different flight phases could be used to model different exposure profiles.

Oculometric Feature Changes During Acute Hypoxia in a Simulated High-Altitude Airdrop Scenario.

BACKGROUND: Severe acute hypoxia results in a rapid deterioration of cognitive functioning and thus poses a risk for human operations in high altitude environments. This study aimed at investigating the effects of oxygen system failure during a high-altitude high-opening (HAHO) parachute jump scenario from 30,000 ft (9144 m) on human physiology and cognitive performance using a noncontact eye-tracking task.METHODS: Nine healthy male volunteers (ages 27-48) were recruited from the Norwegian Special Operations Commandos. Eye-tracking data were collected to derive information on cognitive performance in the context of rapid dynamic changes in pressure altitude while performing a modified King-Devick test. The baseline data was collected at 8000 ft (2438 m) while breathing 100% oxygen during decompression. For every test, the corresponding arterial blood gas analysis was performed.RESULTS: The study subjects endured severe hypoxia, which resulted in significant prolongations of fixation time (range: 284.1-245.6 ms) until 23,397 ft (131 m) and fixation size (range: 34.6-32.4 mm) until 25,389 ft (7739 m) as compared to the baseline (217.6 ± 17.8 ms and 27.2 ± 4.5 mm, respectively). The increase in the saccadic movement and decrease in the saccadic velocity was observed until 28,998 ft and 27,360 ft (8839 and 8339 m), respectively.DISCUSSION: This is the first study to investigate cognitive performance from measured oculometric variables during severe hypobaric hypoxia in a simulated high-altitude airdrop mission scenario. The measurement of altered oculometric variables under hypoxic conditions represents a potential avenue to study altered cognitive performance using noncontact sensors that can derive information and serve to provide the individual with a warning from impending incapacitation.Pradhan GN, Ottestad W, Meland A, Kåsin JI, Høiseth LØ, Cevette MJ, Stepanek J. Oculometric feature changes during acute hypoxia in a simulated high-altitude airdrop scenario. Aerosp Med Hum Perform. 2021; 92(12):928-936.

A helicopter flight does not induce significant changes in systemic biomarker profiles.

Whole-body vibration and noise are inherent characteristics of helicopter operations. The helicopter pilot is affected by vibration from both low-frequency noise and mechanical vibration sources. The way this energy is transmitted to different tissues and organs depends on intensity, frequency and resonance phenomena within the body. Whole-body vibration is known to affect the muscular and skeletal system in the lower part of the spine, but less is known about the response at the cellular level to this stimulation. In some studies, chronic pathological changes have been described in different types of tissue in people exposed to low-frequency noise and vibration. The aim of the present study was to investigate possible cellular reactions to acute exposure to low-frequency noise and vibration in a helicopter. Thirteen healthy males aged 38 (18-69) years were subjected to a 3.5 h helicopter flight in a Westland Sea King Rescue helicopter. Blood tests taken before and after the flight were analysed for more than 40 parameters, including acute phase reactants, markers of leucocyte and platelet activation, complement and hemostasis markers, as well as a broad panel of cytokines, chemokines, growth factors and cell adhesion molecules. The subjects served as their own controls. With the exception of an increase in vascular cell adhesion molecule-1 (VCAM-1) during the flight, no statistically significant changes in the biomarkers were found after controlling for diurnal variation in the control blood tests, which were observed independently of the helicopter flight. In conclusion, one helicopter flight does not induce measurable changes in systemic biomarkers.

Arterial Oxygen Saturation, Pulse Oximetry, and Cerebral and Tissue Oximetry in Hypobaric Hypoxia.

INTRODUCTION: Clinical accuracy of pulse oximeters (giving Spo2) is routinely tested down to an Sao2 of 70%, but lower oxygen saturations are often experienced during hypobaric hypoxia. Cerebral (Sco2) and peripheral tissue (Sto2) oxygen saturations can be measured using near infra-red spectroscopy. In a project simulating oxygen system failure during high altitude-high opening parachuting (HAHO), Sao2, Spo2, Sco2, and forearm Sto2 were measured. The aim of the present analysis was to explore the agreement between Sao2 and the three noninvasive measurements of hypoxemia (Spo2, Sco2, and Sto2).METHODS: Healthy volunteers from the Norwegian Special Operations Commando were studied in a hypobaric chamber as supplemental oxygen was removed at 301 hPa ambient pressure (30,000 ft) and recompressed at 25 hPa · min-1 (1000 ft · min-1) to ground level simulating a HAHO parachute flight. Sao2 was compared with Spo2, Sco2, and Sto2 in scatterplots and Bland-Altman plots, calculating bias and limits of agreement (LOA).RESULTS: The bias ± LOA were: Sao2 vs. Spo2: -5.8% ± 16, Sao2 vs. Sco2: -3.4% ± 11, and Sao2 vs. Sto2: 17% ± 30. The bias for Sao2 vs. Spo2 was dependent on the range of values, and correcting for this with a sloped bias line reduced the LOA to ± 8.2%.DISCUSSION: There were wide limits of agreement between Sao2 and Spo2. Sao2 and Sco2 agreed better, whereas Sao2 and forearm Sto2 had wide LOA. The agreement between Sao2 and Spo2 improved when correcting for the underestimation of Spo2 at low values. There is a poor agreement between Spo2 and the gold standard Sao2 during extreme hypobaric hypoxemia.Ottestad W, Kåsin JI, Høiseth LØ. Arterial oxygen saturation, pulse oximetery, and cerebral and tissue oximetry in hypobaric hypoxia. Aerospace Med Hum Perform. 2018; 89(12):1045-1049.

Acute hypoxia in a simulated high-altitude airdrop scenario due to oxygen system failure.

High-Altitude High Opening (HAHO) is a military operational procedure in which parachute jumps are performed at high altitude requiring supplemental oxygen, putting personnel at risk of acute hypoxia in the event of oxygen equipment failure. This study was initiated by the Norwegian Army to evaluate potential outcomes during failure of oxygen supply, and to explore physiology during acute severe hypobaric hypoxia. A simulated HAHO without supplemental oxygen was carried out in a hypobaric chamber with decompression to 30,000 ft (9,144 m) and then recompression to ground level with a descent rate of 1,000 ft/min (305 m/min). Nine subjects were studied. Repeated arterial blood gas samples were drawn throughout the entire hypoxic exposure. Additionally, pulse oximetry, cerebral oximetry, and hemodynamic variables were monitored. Desaturation evolved rapidly and the arterial oxygen tensions are among the lowest ever reported in volunteers during acute hypoxia. PaO2 decreased from baseline 18.4 (17.3-19.1) kPa, 138.0 (133.5-143.3) mmHg, to a minimum value of 3.3 (2.9-3.7) kPa, 24.8 (21.6-27.8) mmHg, after 180 (60-210) s, [median (range)], N = 9. Hyperventilation with ensuing hypocapnia was associated with both increased arterial oxygen saturation and cerebral oximetry values, and potentially improved tolerance to severe hypoxia. One subject had a sharp drop in heart rate and cardiac index and lost consciousness 4 min into the hypoxic exposure. A simulated high-altitude airdrop scenario without supplemental oxygen results in extreme hypoxemia and may result in loss of consciousness in some individuals.NEW & NOTEWORTHY This is the first study to investigate physiology and clinical outcome of oxygen system failure in a simulated HAHO scenario. The acquired knowledge is of great value to make valid risk-benefit analyses during HAHO training or operations. The arterial oxygen tensions reported in this hypobaric chamber study are among the lowest ever reported during acute hypoxia.

Action slips during whole-body vibration.

Helicopter aircrew members engage in highly demanding cognitive tasks in an environment subject to whole-body vibration (WBV). Sometimes their actions may not be according to plan (e.g. action slips and lapses). This study used a Sustained Attention to Response Task (SART) to examine whether action slips were more frequent during exposure to WBV. Nineteen participants performed the SART in two blocks. In the WBV block participants were exposed to 17 Hz vertical WBV, which is typical of larger helicopter working environments. In the No-WBV block there was no WBV. There were more responses to the rare no-go digit 3 (i.e. action slips) in the WBV block, and participants responded faster in the WBV block. These results suggest that WBV influences response inhibition, and can induce impulsive responding. WBV may increase the likelihood of action slips, mainly due to failure of response inhibition.