P. Germonpré - Academia.edu (original) (raw)

Papers by P. Germonpré

Research paper thumbnail of The'normobaric oxygen paradox': does it increase haemoglobin?

Research paper thumbnail of PFO and the Diver

The focus in this new title is on PFO (Patent Foramen Ovale) as a risk factor in diving and thus ... more The focus in this new title is on PFO (Patent Foramen Ovale) as a risk factor in diving and thus the text is concerned primarily with dissolved gas and the subsequent aberrant distribution of those venous bubbles in the presence of a natural and common anatomical variant of cardiac development. The prevalence of PFO is about 25% in the general population and several respectable investigators have studied this problem and feel that PFO should be considered a definite risk factor for the development of decompression sickness.

Research paper thumbnail of Oxidative stress in breath-hold divers after repetitive dives

Diving and hyperbaric medicine, 2013

Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia foll... more Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia followed by hypoxia and a build-up of carbon dioxide (CO₂), chest-wall compression and significant haemodynamic changes. This study analyses variations in plasma oxidative stress markers after a series of repetitive breath-hold dives. Thirteen breath-hold divers were asked to perform repetitive breath-hold dives to 20 metres' depth to a cumulative breath-hold time of approximately 20 minutes over an hour in the open sea. Plasma nitric oxide (NO), peroxinitrites (ONOO⁻) and thiols (R-SH) were measured before and after the dive sequence. Circulating NO significantly increased after successive breath-hold dives (169.1 ± 58.26% of pre-dive values; P = 0.0002). Peroxinitrites doubled after the dives (207.2 ± 78.31% of pre-dive values; P = 0.0012). Thiols were significantly reduced (69.88 ± 19.23% of pre-dive values; P = 0.0002). NO may be produced by physical effort during breath-hold diving....

Research paper thumbnail of Bubble Stream Reveals Functionality of the Right-to-Left Shunt: Detection of a Potential Source for Air Embolism

Ultrasound in Medicine & Biology, 2014

The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing ... more The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing a flux of bubbles under hyperbaric conditions. The aim of the study was to measure the relationship between these shunts and bubbles in 10 consecutive subjects using trans-thoracic and trans-esophageal echocardiography. In video frames, all cardiac chambers were segmented and bubbles were analyzed by our proposed method and two other methods. The relationship with bubbles and shunts was divided into three classes: no bubbles, 1-20 bubbles, >20 bubbles and measured over 2160 frames. Our sensitivity was 100% and our specificity was between 90.1% and 96.4%. There were 4.32-23.78 bubbles/frame in the left atrium according to our method. After the automatic analysis, shunts were graded double-blinded by two cardiologists. Consequently, we noted that aperture size does not necessarily reflect how active the right-to-left shunt is. Instead, our proposed decay curves constitute a better tool for determining functionality.

Research paper thumbnail of Pulsed high oxygen induces a hypoxic-like response in human umbilical endothelial cells and in humans

Journal of Applied Physiology, 2012

It has been proposed that relative changes of oxygen availability, rather than steady-state hypox... more It has been proposed that relative changes of oxygen availability, rather than steady-state hypoxic or hyperoxic conditions, play an important role in hypoxia-inducible factor (HIF) transcriptional effects. According to this hypothesis describing the “normobaric oxygen paradox”, normoxia following a hyperoxic event is sensed by tissues as an oxygen shortage, upregulating HIF-1 activity. With the aim of confirming, at cellular and at functional level, that normoxia following a hyperoxic event is “interpreted” as a hypoxic event, we report a combination of experiments addressing the effects of an intermittent increase of oxygen concentration on HIF-1 levels and the activity level of specific oxygen-modulated proteins in cultured human umbilical vein endothelial cells and the effects of hemoglobin levels after intermittent breathing of normobaric high (100%) and low (15%) oxygen in vivo in humans. Our experiments confirm that, during recovery after hyperoxia, an increase of HIF express...

Research paper thumbnail of Ultrasound lung “comets” increase after breath-hold diving

European Journal of Applied Physiology, 2010

Research paper thumbnail of The normobaric oxygen paradox: does it increase haemoglobin?

Research paper thumbnail of Scuba diving can induce stress of the temporomandibular joint leading to headache

British Journal of Sports Medicine, 2004

Research paper thumbnail of Blood Glucose Variations in a Diabetic Diver Using Vigorous Self-Assessment and Underwater Intake

Research paper thumbnail of Inducing HSP for Protection against DCS: Heat Exposure before Diving Reduces Bubble Formation in Man

Research paper thumbnail of Carotid Artery Doppler as a minimally invasive screening method for patency of the Foramen Ovale

Research paper thumbnail of Lessons drawn from the in-field experience

info:eu-repo/semantics/publishe

Research paper thumbnail of Labyrinthine Hydrops as a Cause of Cochleo-Vestibular Problems After Scuba Diving: A “New” Diving Syndrome

Research paper thumbnail of Risk of decompression illness among 230 divers in relation to the presence and size of patent foramen ovale

Research paper thumbnail of Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency

Diving and Hyperbaric Medicine Journal

Introduction: Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safe... more Introduction: Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safety and operations at depth that might be reduced by using enriched air nitrox (EANx) mixtures. Using critical flicker fusion frequency (CFFF), a possible early detection of cognitive abilities/cerebral arousal impairment when breathing different oxygen (O 2) fractions was investigated. Methods: Eight male volunteers performed, in random order, two dry chamber dives breathing either air or EANx40 (40% O 2 −60% nitrogen) for 20 minutes (min) at 0.4 MPa. Cognition and arousal were assessed before the dive; upon arrival at 0.4 MPa; after 15 min exposure at 0.4 MPa; on surfacing and 30 min post-dive using behavioural computer-based testing psychology experiment building language (PEBL) and by CFFF while continuously recording brain oxygenation with near-infrared spectroscopy. Results: In both breathing conditions, CFFF and PEBL demonstrated a significant inverse correlation (Pearson r of-0.90, P < 0.0001), improved cognitive abilities/cerebral arousal occurred upon arrival at 0.4 MPa followed by a progressive deterioration. Initial brain activation was associated with a significant increase in oxyhaemoglobin (HbO 2) and a simultaneous decrease of deoxyhaemoglobin (HHb). The magnitude of the changes was significantly greater under EANx (P = 0.038). Conclusions: Since changes were not related to haemodynamic variables, HbO 2 and HHb values indicate a significant, O 2-dependent activation in the prefrontal cortex. Owing to the correlation with some tests from the PEBL, CFFF could be a convenient measure of cognitive performance/ability in extreme environments, likely under the direct influence of oxygen partial pressure, a potent modulator of IGN symptoms.

Research paper thumbnail of Do Environmental Conditions Contribute to Narcosis Onset and Symptom Severity?

International Journal of Sports Medicine, 2016

Research paper thumbnail of Functional comparison between critical flicker fusion frequency and simple cognitive tests in subjects breathing air or oxygen in normobaria

Diving and hyperbaric medicine, 2013

Measurement of inert gas narcosis and its degree is difficult during operational circumstances, h... more Measurement of inert gas narcosis and its degree is difficult during operational circumstances, hence the need for a reliable, reproducible and adaptable tool. Although being an indirect measure of brain function, if reliable, critical flicker fusion frequency (CFFF) could address this need and be used for longitudinal studies on cortical arousal in humans. To test the reliability of this method, the comparison between CFFF and three tests (Math-Processing Task, Trail-Making Task, and Perceptual Vigilance Task) from the Psychology Experiment Building Language battery (PEBL) were used to evaluate the effect of 10 minutes of 100% normobaric oxygen breathing on mental performance in 20 healthy male volunteers. Breathing normobaric oxygen significantly improved all but one of the measured parameters, with an increase of CFFF (117.3 ± 10.04% of baseline, P < 0.0001) and a significant reduction of time to complete in both the math-processing (2,103 ± 432.1 ms to 1,879 ± 417.5 ms, P = 0...

Research paper thumbnail of Nitric oxide-related endothelial changes in breath-hold and scuba divers

Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc

Scuba and breath-hold divers are compared to investigate whether endothelial response changes are... more Scuba and breath-hold divers are compared to investigate whether endothelial response changes are similar despite different exposure(s) to hyperoxia. 14 divers (nine scuba and five breath-holding) performed either one scuba dive (25m/25 minutes) or successive breath-hold dives at a depth of 20 meters, adding up to 25 minutes of immersion time in a diving pool. Flow-mediated dilation (FMD) was measured using echography. Peripheral post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography and plasmatic nitric oxide (NO) concentration using a nitrate/nitrite colorimetric assay kit. The FMD decreased in both groups. PORH was reduced in scuba divers but increased in breath-hold divers. No difference in circulating NO was observed for the scuba group. Opposingly, an increase in circulating NO was observed for the breath-hold group. Some cardiovascular effects can be explained by interaction between NO and superoxide anion during both types of diving ending to less N...

Research paper thumbnail of Influence of scuba diving on asymptomatic isolated pulmonary bullae

Diving and hyperbaric medicine, 2008

Pulmonary blebs and bullae are generally considered an absolute contra-indication for scuba divin... more Pulmonary blebs and bullae are generally considered an absolute contra-indication for scuba diving, because of a high estimated risk of pulmonary overpressure syndrome due to air-trapping inside the bulla. This is primarily based on a number of retrospective studies and case reports; formal prospective evidence of a higher risk is lacking. We present three cases where a pulmonary bulla was radiographically shown to increase in diameter, seemingly related to scuba diving activity, and causing ultimately a barotraumatic diving accident. These cases provide pathophysiological clues as to how even an isolated, non-ventilated bulla can be the cause of pulmonary barotrauma. The most likely mechanism for this phenomenon is a 'stretching' of the bulla upon ascent from the dive: after a period of compression (Boyle's Law), there is a gradual diffusion of air through the bulla wall, with restoration to its initial size by the end of the dive. Upon ascent, the air diffuses only slo...

Research paper thumbnail of Hyperbaric oxygen therapy after failure of conventional therapy for sudden deafness

B-ENT, 2006

We investigated the effect of secondary hyperbaric oxygen therapy (HBO) for patients with idiopat... more We investigated the effect of secondary hyperbaric oxygen therapy (HBO) for patients with idiopathic sudden sensorineural hearing loss after unsuccessful conventional treatment. We retrospectively evaluated 3 groups: 100 patients without further treatment (group 1), 160 patients with secondary HBO at 1.5 ATA (group 2), and 56 patients with secondary HBO at 2.5 ATA (group 3). In group 1, a mean hearing gain (MHG) of 2.6 +/- 15 dB was found at the end of the follow-up period. After HBO, a MHG of 3.1 +/- 9 dB in group 2 and 19.7 +/- 23 dB in group 3 was achieved. The results in group 3 were statistically significant in comparison to group 1 (p < 0.007) and to group 2 (p < 0.009). With HBO after initial therapy failure, there is a significant correlation of MHG with time delay before HBO (p < 0.03). HBO at 2.5 ATA in patients with idiopathic sudden sensorineural hearing loss after unsuccessful conventional treatment yields significant improvement of hearing. MHG is higher when ...

Research paper thumbnail of The'normobaric oxygen paradox': does it increase haemoglobin?

Research paper thumbnail of PFO and the Diver

The focus in this new title is on PFO (Patent Foramen Ovale) as a risk factor in diving and thus ... more The focus in this new title is on PFO (Patent Foramen Ovale) as a risk factor in diving and thus the text is concerned primarily with dissolved gas and the subsequent aberrant distribution of those venous bubbles in the presence of a natural and common anatomical variant of cardiac development. The prevalence of PFO is about 25% in the general population and several respectable investigators have studied this problem and feel that PFO should be considered a definite risk factor for the development of decompression sickness.

Research paper thumbnail of Oxidative stress in breath-hold divers after repetitive dives

Diving and hyperbaric medicine, 2013

Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia foll... more Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia followed by hypoxia and a build-up of carbon dioxide (CO₂), chest-wall compression and significant haemodynamic changes. This study analyses variations in plasma oxidative stress markers after a series of repetitive breath-hold dives. Thirteen breath-hold divers were asked to perform repetitive breath-hold dives to 20 metres' depth to a cumulative breath-hold time of approximately 20 minutes over an hour in the open sea. Plasma nitric oxide (NO), peroxinitrites (ONOO⁻) and thiols (R-SH) were measured before and after the dive sequence. Circulating NO significantly increased after successive breath-hold dives (169.1 ± 58.26% of pre-dive values; P = 0.0002). Peroxinitrites doubled after the dives (207.2 ± 78.31% of pre-dive values; P = 0.0012). Thiols were significantly reduced (69.88 ± 19.23% of pre-dive values; P = 0.0002). NO may be produced by physical effort during breath-hold diving....

Research paper thumbnail of Bubble Stream Reveals Functionality of the Right-to-Left Shunt: Detection of a Potential Source for Air Embolism

Ultrasound in Medicine & Biology, 2014

The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing ... more The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing a flux of bubbles under hyperbaric conditions. The aim of the study was to measure the relationship between these shunts and bubbles in 10 consecutive subjects using trans-thoracic and trans-esophageal echocardiography. In video frames, all cardiac chambers were segmented and bubbles were analyzed by our proposed method and two other methods. The relationship with bubbles and shunts was divided into three classes: no bubbles, 1-20 bubbles, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;20 bubbles and measured over 2160 frames. Our sensitivity was 100% and our specificity was between 90.1% and 96.4%. There were 4.32-23.78 bubbles/frame in the left atrium according to our method. After the automatic analysis, shunts were graded double-blinded by two cardiologists. Consequently, we noted that aperture size does not necessarily reflect how active the right-to-left shunt is. Instead, our proposed decay curves constitute a better tool for determining functionality.

Research paper thumbnail of Pulsed high oxygen induces a hypoxic-like response in human umbilical endothelial cells and in humans

Journal of Applied Physiology, 2012

It has been proposed that relative changes of oxygen availability, rather than steady-state hypox... more It has been proposed that relative changes of oxygen availability, rather than steady-state hypoxic or hyperoxic conditions, play an important role in hypoxia-inducible factor (HIF) transcriptional effects. According to this hypothesis describing the “normobaric oxygen paradox”, normoxia following a hyperoxic event is sensed by tissues as an oxygen shortage, upregulating HIF-1 activity. With the aim of confirming, at cellular and at functional level, that normoxia following a hyperoxic event is “interpreted” as a hypoxic event, we report a combination of experiments addressing the effects of an intermittent increase of oxygen concentration on HIF-1 levels and the activity level of specific oxygen-modulated proteins in cultured human umbilical vein endothelial cells and the effects of hemoglobin levels after intermittent breathing of normobaric high (100%) and low (15%) oxygen in vivo in humans. Our experiments confirm that, during recovery after hyperoxia, an increase of HIF express...

Research paper thumbnail of Ultrasound lung “comets” increase after breath-hold diving

European Journal of Applied Physiology, 2010

Research paper thumbnail of The normobaric oxygen paradox: does it increase haemoglobin?

Research paper thumbnail of Scuba diving can induce stress of the temporomandibular joint leading to headache

British Journal of Sports Medicine, 2004

Research paper thumbnail of Blood Glucose Variations in a Diabetic Diver Using Vigorous Self-Assessment and Underwater Intake

Research paper thumbnail of Inducing HSP for Protection against DCS: Heat Exposure before Diving Reduces Bubble Formation in Man

Research paper thumbnail of Carotid Artery Doppler as a minimally invasive screening method for patency of the Foramen Ovale

Research paper thumbnail of Lessons drawn from the in-field experience

info:eu-repo/semantics/publishe

Research paper thumbnail of Labyrinthine Hydrops as a Cause of Cochleo-Vestibular Problems After Scuba Diving: A “New” Diving Syndrome

Research paper thumbnail of Risk of decompression illness among 230 divers in relation to the presence and size of patent foramen ovale

Research paper thumbnail of Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency

Diving and Hyperbaric Medicine Journal

Introduction: Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safe... more Introduction: Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safety and operations at depth that might be reduced by using enriched air nitrox (EANx) mixtures. Using critical flicker fusion frequency (CFFF), a possible early detection of cognitive abilities/cerebral arousal impairment when breathing different oxygen (O 2) fractions was investigated. Methods: Eight male volunteers performed, in random order, two dry chamber dives breathing either air or EANx40 (40% O 2 −60% nitrogen) for 20 minutes (min) at 0.4 MPa. Cognition and arousal were assessed before the dive; upon arrival at 0.4 MPa; after 15 min exposure at 0.4 MPa; on surfacing and 30 min post-dive using behavioural computer-based testing psychology experiment building language (PEBL) and by CFFF while continuously recording brain oxygenation with near-infrared spectroscopy. Results: In both breathing conditions, CFFF and PEBL demonstrated a significant inverse correlation (Pearson r of-0.90, P < 0.0001), improved cognitive abilities/cerebral arousal occurred upon arrival at 0.4 MPa followed by a progressive deterioration. Initial brain activation was associated with a significant increase in oxyhaemoglobin (HbO 2) and a simultaneous decrease of deoxyhaemoglobin (HHb). The magnitude of the changes was significantly greater under EANx (P = 0.038). Conclusions: Since changes were not related to haemodynamic variables, HbO 2 and HHb values indicate a significant, O 2-dependent activation in the prefrontal cortex. Owing to the correlation with some tests from the PEBL, CFFF could be a convenient measure of cognitive performance/ability in extreme environments, likely under the direct influence of oxygen partial pressure, a potent modulator of IGN symptoms.

Research paper thumbnail of Do Environmental Conditions Contribute to Narcosis Onset and Symptom Severity?

International Journal of Sports Medicine, 2016

Research paper thumbnail of Functional comparison between critical flicker fusion frequency and simple cognitive tests in subjects breathing air or oxygen in normobaria

Diving and hyperbaric medicine, 2013

Measurement of inert gas narcosis and its degree is difficult during operational circumstances, h... more Measurement of inert gas narcosis and its degree is difficult during operational circumstances, hence the need for a reliable, reproducible and adaptable tool. Although being an indirect measure of brain function, if reliable, critical flicker fusion frequency (CFFF) could address this need and be used for longitudinal studies on cortical arousal in humans. To test the reliability of this method, the comparison between CFFF and three tests (Math-Processing Task, Trail-Making Task, and Perceptual Vigilance Task) from the Psychology Experiment Building Language battery (PEBL) were used to evaluate the effect of 10 minutes of 100% normobaric oxygen breathing on mental performance in 20 healthy male volunteers. Breathing normobaric oxygen significantly improved all but one of the measured parameters, with an increase of CFFF (117.3 ± 10.04% of baseline, P < 0.0001) and a significant reduction of time to complete in both the math-processing (2,103 ± 432.1 ms to 1,879 ± 417.5 ms, P = 0...

Research paper thumbnail of Nitric oxide-related endothelial changes in breath-hold and scuba divers

Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc

Scuba and breath-hold divers are compared to investigate whether endothelial response changes are... more Scuba and breath-hold divers are compared to investigate whether endothelial response changes are similar despite different exposure(s) to hyperoxia. 14 divers (nine scuba and five breath-holding) performed either one scuba dive (25m/25 minutes) or successive breath-hold dives at a depth of 20 meters, adding up to 25 minutes of immersion time in a diving pool. Flow-mediated dilation (FMD) was measured using echography. Peripheral post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography and plasmatic nitric oxide (NO) concentration using a nitrate/nitrite colorimetric assay kit. The FMD decreased in both groups. PORH was reduced in scuba divers but increased in breath-hold divers. No difference in circulating NO was observed for the scuba group. Opposingly, an increase in circulating NO was observed for the breath-hold group. Some cardiovascular effects can be explained by interaction between NO and superoxide anion during both types of diving ending to less N...

Research paper thumbnail of Influence of scuba diving on asymptomatic isolated pulmonary bullae

Diving and hyperbaric medicine, 2008

Pulmonary blebs and bullae are generally considered an absolute contra-indication for scuba divin... more Pulmonary blebs and bullae are generally considered an absolute contra-indication for scuba diving, because of a high estimated risk of pulmonary overpressure syndrome due to air-trapping inside the bulla. This is primarily based on a number of retrospective studies and case reports; formal prospective evidence of a higher risk is lacking. We present three cases where a pulmonary bulla was radiographically shown to increase in diameter, seemingly related to scuba diving activity, and causing ultimately a barotraumatic diving accident. These cases provide pathophysiological clues as to how even an isolated, non-ventilated bulla can be the cause of pulmonary barotrauma. The most likely mechanism for this phenomenon is a 'stretching' of the bulla upon ascent from the dive: after a period of compression (Boyle's Law), there is a gradual diffusion of air through the bulla wall, with restoration to its initial size by the end of the dive. Upon ascent, the air diffuses only slo...

Research paper thumbnail of Hyperbaric oxygen therapy after failure of conventional therapy for sudden deafness

B-ENT, 2006

We investigated the effect of secondary hyperbaric oxygen therapy (HBO) for patients with idiopat... more We investigated the effect of secondary hyperbaric oxygen therapy (HBO) for patients with idiopathic sudden sensorineural hearing loss after unsuccessful conventional treatment. We retrospectively evaluated 3 groups: 100 patients without further treatment (group 1), 160 patients with secondary HBO at 1.5 ATA (group 2), and 56 patients with secondary HBO at 2.5 ATA (group 3). In group 1, a mean hearing gain (MHG) of 2.6 +/- 15 dB was found at the end of the follow-up period. After HBO, a MHG of 3.1 +/- 9 dB in group 2 and 19.7 +/- 23 dB in group 3 was achieved. The results in group 3 were statistically significant in comparison to group 1 (p < 0.007) and to group 2 (p < 0.009). With HBO after initial therapy failure, there is a significant correlation of MHG with time delay before HBO (p < 0.03). HBO at 2.5 ATA in patients with idiopathic sudden sensorineural hearing loss after unsuccessful conventional treatment yields significant improvement of hearing. MHG is higher when ...