scholarly journals Research on the Time of Visual Muscular Response in Divers During Diving

2020 ◽  
Vol 70 (1) ◽  
pp. 53-58
Author(s):  
Augustyn Dolatkowski ◽  
Kazimierz Dęga ◽  
Stanisław Klajman ◽  
Janusz Torbus
Keyword(s):  
Ambient Pressure ◽  
Toxic Effects ◽  
Hyperbaric Chamber ◽  
Eye Muscle ◽  
Muscle Reflex ◽  
Chamber Studies ◽  
Muscle Reflexes ◽  
Reflex Time

AbstractThe paper presents a continuation of studies on the influence of increased ambient pressure on the eye-muscle reflex. Using the same methods, the research was carried out in real conditions, i.e. during dives in water. Dives were performed in classical equipment with air as a breathing mix at depths of 10, 20, 30, 40, 50 and 60 m. It was found that statistically significant differences in the time of eye-muscle reflexes occur during the transition from 0 to 10, from 40 to 50 and 50 to 60 meters of overpressure. In the conclusions, it was found that the prolongation of reflex time is much greater than in hyperbaric chamber studies. As in previous studies, toxic effects of components of the breathing mixture, especially nitrogen, were considered the main cause.

Hyperbaric treatment for decompression sickness: current recommendations

2019 ◽  
pp. 685-693
Author(s):  
Richard E. Moon ◽  
◽  
Simon Mitchell ◽  
◽  
Keyword(s):  
Decompression Sickness ◽  
Ambient Pressure ◽  
Dissolved Gas ◽  
Hyperbaric Chamber ◽  
Hyperbaric Treatment ◽  
Hypobaric Chamber ◽  
Rapid Ascent ◽  
Gas Pressures

Rationale Decompression sickness (DCS, “bends”) is caused by formation of bubbles in tissues and/or blood when the sum of dissolved gas pressures exceeds ambient pressure (supersaturation) [1]. This may occur when ambient pressure is reduced during any of the following: • ascent from a dive; • depressurization of a hyperbaric chamber; • rapid ascent to altitude in an unpressurised aircraft or hypobaric chamber; • loss of cabin pressure in an aircraft [2] and • during space walks.

Variability in venous gas emboli following the same dive at 3,658 meters

2021 ◽  
pp. 119-126
Author(s):  
Hayden W Hess ◽  
◽  
Courtney E Wheelock ◽  
Erika St. James ◽  
Jocelyn L Stooks ◽  
...  
Keyword(s):  
Decompression Sickness ◽  
Ambient Pressure ◽  
Correction Method ◽  
Simulated Altitude ◽  
Hyperbaric Chamber ◽  
Minute Exposure ◽  
The Cross ◽  
Grade 3 ◽  
Decompression Stress ◽  
The U.S

Exposure to a reduction in ambient pressure such as in high-altitude climbing, flying in aircrafts, and decompression from underwater diving results in circulating vascular gas bubbles (i.e., venous gas emboli [VGE]). Incidence and severity of VGE, in part, can objectively quantify decompression stress and risk of decompression sickness (DCS) which is typically mitigated by adherence to decompression schedules. However, dives conducted at altitude challenge recommendations for decompression schedules which are limited to exposures of 10,000 feet in the U.S. Navy Diving Manual (Rev. 7). Therefore, in an ancillary analysis within a larger study, we assessed the evolution of VGE for two hours post-dive using echocardiography following simulated altitude dives at 12,000 feet. Ten divers completed two dives to 66 fsw (equivalent to 110 fsw at sea level by the Cross correction method) for 30 minutes in a hyperbaric chamber. All dives were completed following a 60-minute exposure at 12,000 feet. Following the dive, the chamber was decompressed back to altitude for two hours. Echocardiograph measurements were performed every 20 minutes post-dive. Bubbles were counted and graded using the Germonpré and Eftedal and Brubakk method, respectively. No diver presented with symptoms of DCS following the dive or two hours post-dive at altitude. Despite inter- and intra-diver variability of VGE grade following the dives, the majority (11/20 dives) presented a peak VGE Grade 0, three VGE Grade 1, one VGE Grade 2, four VGE Grade 3, and one VGE Grade 4. Using the Cross correction method for a 66-fsw dive at 12,000 feet of altitude resulted in a relatively low decompression stress and no cases of DCS.

Continuous intracellular recording from mammalian neurons exposed to hyperbaric helium, oxygen, or air

2000 ◽  
Vol 89 (2) ◽  
pp. 807-822 ◽  
Author(s):  
Jay B. Dean ◽  
Daniel K. Mulkey
Keyword(s):  
Intracellular Recording ◽  
Ambient Pressure ◽  
Hyperbaric Chamber ◽  
Nitrogen Levels ◽  
Mammalian Neuron ◽  
Pressure Cylinder ◽  
Neurophysiological Mechanisms ◽  
Oxygen Measurements ◽  
Tissue Nitrogen ◽  
Brain Stem Slices

We developed a hyperbaric chamber for intracellular recording in rat brain stem slices during continuous compression and decompression of the tissue bath with the inert gas helium. Air, rather than helium, was also used as the compression medium in some cases to increase tissue nitrogen levels. An important feature is the chamber door, which opens or closes rapidly at 1 atmosphere absolute (ATA) for increased accessibility of the microelectrode. The door also closes and seals smoothly without disrupting the intracellular recording. Hyperbaric oxygen was administered during helium compression using a separate pressure cylinder filled with perfusate equilibrated with 2.3–3.3 ATA oxygen. Measurements of tissue/bath Po 2 and pH confirmed that the effects of compression using helium or air could be differentiated from those due to increased Po 2. One hundred and thirteen neurons were studied during 375 compression cycles ranging from 1 to 20 ATA (mode 3.0 ATA). We conclude that it is technically feasible to record intracellularly from the same mammalian neuron while changing ambient pressure over a physiologically important range. These techniques will be useful for studying how various hyperbaric environments affect neurophysiological mechanisms.

scholarly journals Seizures Caused by Exposure to Hyperbaric Oxygen in Rats Can Be Predicted by Early Changes in Electrodermal Activity

2022 ◽  
Vol 12 ◽  
Author(s):  
Hugo F. Posada-Quintero ◽  
Carol S. Landon ◽  
Nicole M. Stavitzski ◽  
Jay B. Dean ◽  
Ki H. Chon
Keyword(s):  
Nervous System ◽  
Hyperbaric Oxygen ◽  
Electrodermal Activity ◽  
Radio Telemetry ◽  
Core Body Temperature ◽  
Ambient Pressure ◽  
Oxygen Toxicity ◽  
Hyperbaric Chamber ◽  
Generalized Seizures ◽  
Animal Chamber

Hyperbaric oxygen (HBO2) is breathed during undersea operations and in hyperbaric medicine. However, breathing HBO2 by divers and patients increases the risk of central nervous system oxygen toxicity (CNS-OT), which ultimately manifests as sympathetic stimulation producing tachycardia and hypertension, hyperventilation, and ultimately generalized seizures and cardiogenic pulmonary edema. In this study, we have tested the hypothesis that changes in electrodermal activity (EDA), a measure of sympathetic nervous system activation, precedes seizures in rats breathing 5 atmospheres absolute (ATA) HBO2. Radio telemetry and a rodent tether apparatus were adapted for use inside a sealed hyperbaric chamber. The tethered rat was free to move inside a ventilated animal chamber that was flushed with air or 100% O2. The animal chamber and hyperbaric chamber (air) were pressurized in parallel at ~1 atmosphere/min. EDA activity was recorded simultaneously with cortical electroencephalogram (EEG) activity, core body temperature, and ambient pressure. We have captured the dynamics of EDA using time-varying spectral analysis of raw EDA (TVSymp), previously developed as a tool for sympathetic tone assessment in humans, adjusted to detect the dynamic changes of EDA in rats that occur prior to onset of CNS-OT seizures. The results show that a significant increase in the amplitude of TVSymp values derived from EDA recordings occurs on average (±SD) 1.9 ± 1.6 min before HBO2-induced seizures. These results, if corroborated in humans, support the use of changes in TVSymp activity as an early “physio-marker” of impending and potentially fatal seizures in divers and patients.

TOXIC EFFECTS IN MONKEYS EXPOSED TO 100% OXYGEN AT AMBIENT PRESSURE

1969 ◽  
Author(s):  
Clare C. Johnston ◽  
Marilyn E. George ◽  
James P. Murphy ◽  
Kenneth C. Back
Keyword(s):  
Ambient Pressure ◽  
Toxic Effects

Maintained exercise pressor response in heart failure

1998 ◽  
Vol 85 (5) ◽  
pp. 1793-1799 ◽  
Author(s):  
J. Kevin Shoemaker ◽  
Allen R. Kunselman ◽  
David H. Silber ◽  
Lawrence I. Sinoway
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Perfusion Pressure ◽  
Pressor Response ◽  
Ambient Pressure ◽  
Muscle Blood Flow ◽  
Positive Pressure ◽  
Arterial Blood ◽  
Muscle Reflex ◽  
The Impact

The impact of forearm blood flow limitation on muscle reflex (metaboreflex) activation during exercise was examined in 10 heart failure (HF) (NYHA class III and IV) and 9 control (Ctl) subjects. Rhythmic handgrip contractions (25% maximal voluntary contraction, 30 contractions/min) were performed over 5 min under conditions of ambient pressure or with +50 mmHg positive pressure about the exercising forearm. Mean arterial blood pressure (MAP) and venous effluent hemoglobin (Hb) O2 saturation, lactate and H+ concentrations ([La] and [H+], respectively) were measured at baseline and during exercise. For ambient contractions, the increase (Δ) in MAP by end exercise (ΔMAP; i.e., the exercise pressor response) was the same in both groups (10.1 ± 1.2 vs. 7.33 ± 1.3 mmHg, HF vs. Ctl, respectively) despite larger Δ[La] and Δ[H+] for the HF group ( P < 0.05). With ischemic exercise, the ΔMAP for HF (21.7 ± 2.7 mmHg) exceeded that of Ctl subjects (12.2 ± 2.8 mmHg) ( P < 0.0001). Also, for HF, Δ[La] (2.94 ± 0.4 mmol) and Δ[H+] (24.8 ± 2.7 nmol) in the ischemic trial were greater than in Ctl (1.63 ± 0.4 mmol and 15.3 ± 2.8 nmol; [La] and [H+], respectively) ( P < 0.02). Hb O2 saturation was reduced in Ctl from ∼43% in the ambient trial to ∼27% with ischemia ( P < 0.0001). O2 extraction was maximized under ambient exercise conditions for HF but not for Ctl. Despite progressive increases in blood perfusion pressure over the course of ischemic exercise, no improvement in Hb O2saturation or muscle metabolism was observed in either group. These data suggest that muscle reflex activation of the pressor response is intact in HF subjects but the resulting improvement in perfusion pressure does not appear to enhance muscle oxidative metabolism or muscle blood flow, possibly because of associated increases in sympathetic vasoconstriction of active skeletal muscle.

scholarly journals Evaluation and Characteristic of Modified Ventilator Under Hyperbaric Conditions During Volume-controlled Ventilation

2021 ◽  
Author(s):  
Cong Wang ◽  
Lianbi Xue ◽  
Jialong Liu ◽  
Liyun Chang ◽  
Qiuhong Yu ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Minute Volume ◽  
Test Lung ◽  
Hyperbaric Chamber ◽  
Controlled Ventilation ◽  
Volume Controlled Ventilation ◽  
Grand Rapids ◽  
The Stability ◽  
Volume Controlled ◽  
Hyperbaric Conditions

Abstract Purpose：The stability of the modified ventilator (Shangrila590, Beijing Aeonmed Company, Beijing, China) was evaluated under hyperbaric conditions during volume-controlled ventilation in this study by Michigan test lung (5601i, Grand Rapids, MI, US).Methods：Experiments were performed inside the multiplace hyperbaric chamber at 1.0, 1.5 and 2.0 atmospheres absolute (ATA). The modified ventilator placed inside the hyperbaric chamber was connected to the test lung. During volume-controlled ventilation (VCV), data for the test lung were collected by a personal computer outside the hyperbaric chamber. The preset tide volume (VTset) of the ventilator (400-1000 ml) and the resistance and compliance of the testing lung were adjusted before the experiments at every ambient pressure. With every test setting, the tide volume (VT), inspiratory airway peak pressure (Ppeak) and minute volume (MV) displayed by the ventilator and the test lung were recorded by the computer. We compared the ventilator and test lung data under 1.0, 1.5 and 2.0 ATA to evaluate the stability of the modified ventilator.Results：The variation in VT in the test lung and the ventilator at different ambient pressures changed within a narrow range, and the differences were statistically significant. In every test setting, changes in the MV of the ventilator were limited and acceptable, with significant differences at different ambient pressures. However, Ppeak increased obviously, as detected by the ventilator and test lung at higher ambient pressure during VCV.Conclusions：The modified Shangrila590 ventilator can work well in a hyperbaric chamber. It can provide relatively stable VT and MV during VCV with VTset from 400 ml to 1000 ml when the ambient pressure increases from 1.0 ATA to 2.0 ATA. The raised ambient pressure will lead to increased gas density, which may result in more airway resistance and higher Ppeak during VCV.

Absent or Elevated Middle Ear Muscle Reflexes in the Presence of Normal Otoacoustic Emissions: A Universal Finding in 136 Cases of Auditory Neuropathy/Dys-synchrony

2005 ◽  
Vol 16 (08) ◽  
pp. 546-553 ◽  
Author(s):  
Charles I. Berlin ◽  
Linda J. Hood ◽  
Thierry Morlet ◽  
Diane Wilensky ◽  
Patti St. John ◽  
...  
Keyword(s):  
Middle Ear ◽  
Otoacoustic Emissions ◽  
Hearing Screening ◽  
Auditory Neuropathy ◽  
The Other ◽  
Frequency Bands ◽  
Behavioral Audiogram ◽  
Muscle Reflex ◽  
Muscle Reflexes

We extracted a subpopulation of 136 patients (from our database of 257 AN/AD subjects) in whom middle ear muscle reflexes had been measured. None showed normal reflexes at all frequencies tested. Only three subjects showed any reflexes at 95 dB HL or below, but never at both 1 and 2 kHz in both ears whether ipsilaterally or contralaterally elicited. All the other reflex measures in these remaining 133 patients were either absent or observed above 100 dB HL, which is incongruous with their normal otoacoustic emissions throughout the frequency bands.Therefore, we urge colleagues to test ipsilateral middle ear muscle reflex at least at 1 kHz and 2 kHz in any perinatal hearing screening that depends solely on otoacoustic emissions. If the emissions are present and the reflexes are absent or elevated, an ABR may be required to properly intervene, because the management of AN/AD patients often differs drastically from what the behavioral audiogram or the ABR suggest.

Role of diprotonated phosphate in evoking muscle reflex responses in cats and humans

1994 ◽  
Vol 267 (2) ◽  
pp. H770-H778 ◽  
Author(s):  
L. I. Sinoway ◽  
M. B. Smith ◽  
B. Enders ◽  
U. Leuenberger ◽  
T. Dzwonczyk ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Triceps Surae ◽  
Nerve Activity ◽  
Reflex Responses ◽  
Arterial Blood ◽  
Muscle Reflex ◽  
Muscle Reflexes

Lactic acid and H+ evoke muscle reflexes that raise sympathetic nerve activity. Whether these substances are direct afferent stimulants or markers for the acidification of other substances is unknown. Diprotonated phosphate (H2PO4-), a possible mediator of fatigue, increases as the cell acidifies and phosphate is produced. Its role in evoking muscle reflexes is unknown. We used 31P-nuclear magnetic resonance to measure forearm muscle H+ and H2PO4- and microneurography to measure muscle sympathetic nerve activity (MSNA, peroneal nerve) during a handgrip protocol designed to dissociate H+ from H2PO4-. Ischemic handgrip (50% maximal voluntary contraction x 2 min) was followed by a 1-min rest period during which the muscle was freely perfused. This was followed by a second bout of ischemic handgrip and a 5-min recovery. In seven of eight subjects, MSNA correlated with H2PO4-, whereas it correlated with pH in only one subject. To determine whether muscle reflex responses are evoked by H+, lactic acid, monoprotonated phosphate (HPO4(2-), or H2PO4-, we injected H+, lactate, H2PO4- [all 50 mM in 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffered to pH 6], and HPO4(2-) (50 mM, pH 7.5 in 10 mM HEPES) into the arterial supply of the triceps surae of the cat (n = 9) as we measured mean arterial blood pressure (MAP). H2PO4- increased MAP more than HPO4(2-), H+, or lactate (27.1 +/- 3.7 vs. 5.0 +/- 1.3, 4.6 +/- 3.1, and 7.7 +/- 3.2 rise in mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of Masseteric Reflexes by Simulated Mastication

2009 ◽  
Vol 89 (1) ◽  
pp. 61-65 ◽  
Author(s):  
S. Naser-ud-Din ◽  
P.F. Sowman ◽  
H. Dang ◽  
K.S. Türker
Keyword(s):  
Muscle Spindle ◽  
Reflex Modulation ◽  
Masticatory Muscle ◽  
Limb Muscle ◽  
Reflex Responses ◽  
Human Movements ◽  
Muscle Reflex ◽  
Muscle Reflexes

It is well-known that limb muscle reflexes are modulated during human movements. However, little is known about the existence of equivalent masticatory muscle reflex modulation. We hypothesized that masticatory reflexes would be modulated during chewing so that smooth masticatory movements occur. To examine this hypothesis, we studied the modulation of inhibitory reflexes evoked by periodontal mechanoreceptor activation and of excitatory reflexes evoked by muscle spindle activation during simulated mastication. In 28 participants, 1- and 2-N mechanical taps were delivered to the incisor. Reflex responses to these taps were examined in the average masseteric electromyogram. To differentiate between periodontal mechanoreceptor- and muscle-spindle-mediated reflex components, we performed experiments prior to, and in the presence of, periodontal anesthesia. Both periodontal mechanoreceptor and muscle spindle reflexes were reduced during simulated masticatory movements.

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