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Jayne C. Carberry - One of the best experts on this subject based on the ideXlab platform.
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changes in pharyngeal collapsibility and genioglossus reflex responses to negative pressure during the respiratory cycle in obstructive sleep apnoea
The Journal of Physiology, 2020Co-Authors: Amal M Osman, Simon C. Gandevia, Jane E. Butler, Jayne C. Carberry, Danny J EckertAbstract:KEY POINTS: Impaired pharyngeal anatomy and increased Airway collapsibility is a major cause of obstructive sleep apnoea (OSA) and a mediator of its severity. Upper Airway Reflexes to changes in Airway pressure provide important protection against Airway closure. This study shows increased pharyngeal collapsibility and attenuated genioglossus reflex responses during expiration in people with OSA. ABSTRACT: Upper Airway collapse contributes to obstructive sleep apnoea (OSA) pathogenesis. Pharyngeal dilator muscle activity varies throughout the respiratory cycle and may contribute to dynamic changes in pharyngeal collapsibility. However, whether Upper Airway collapsibility and reflex responses to changes in Airway pressure vary throughout the respiratory cycle in OSA is unclear. Thus, this study quantified differences in Upper Airway collapsibility and genioglossus electromyographic (EMG) activity and reflex responses during different phases of the respiratory cycle. Twelve middle-aged people with OSA (2 female) were fitted with standard polysomnography equipment: a nasal mask, pneumotachograph, two fine-wire intramuscular electrodes into the genioglossus, and a pressure catheter positioned at the epiglottis and a second at the choanae (the collapsible portion of the Upper Airway). At least 20 brief ( approximately 250 ms) pressure pulses ( approximately -11 cmH2 O at the mask) were delivered every 2-10 breaths during four conditions: (1) early inspiration, (2) mid-inspiration, (3) early expiration, and (4) mid-expiration. Mean baseline genioglossus EMG activity 100 ms prior to pulse delivery and genioglossus reflex responses were quantified for each condition. The Upper Airway collapsibility index (UACI), quantified as 100 x (nadir choanal - epiglottic pressure)/nadir choanal pressure during negative pressure pulses, varied throughout the respiratory cycle (early inspiration = 43 +/- 25%, mid-inspiration = 29 +/- 19%, early expiration = 83 +/- 19% and mid-expiration = 95 +/- 11% (mean +/- SD) P < 0.01). Genioglossus EMG activity was lower during expiration (e.g. mid-expiration vs. mid-inspiration = 76 +/- 23 vs. 127 +/- 41% of early-inspiration, P < 0.001). Similarly, genioglossus reflex excitation was delayed (39 +/- 11 vs. 23 +/- 7 ms, P < 0.001) and reflex excitation amplitude attenuated during mid-expiration versus early inspiration (209 +/- 36 vs. 286 +/- 80%, P = 0.009). These findings may provide insight into the physiological mechanisms of pharyngeal collapse in OSA.
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changes in pharyngeal collapsibility and genioglossus reflex responses to negative pressure during the respiratory cycle in obstructive sleep apnoea
The Journal of Physiology, 2020Co-Authors: Amal M Osman, Simon C. Gandevia, Jane E. Butler, Jayne C. Carberry, Danny J EckertAbstract:KEY POINTS Impaired pharyngeal anatomy and increased Airway collapsibility is a major cause of obstructive sleep apnoea (OSA) and a mediator of its severity. Upper Airway Reflexes to changes in Airway pressure provide important protection against Airway closure. This study shows increased pharyngeal collapsibility and attenuated genioglossus reflex responses during expiration in people with OSA. ABSTRACT Upper Airway collapse contributes to obstructive sleep apnoea (OSA) pathogenesis. Pharyngeal dilator muscle activity varies throughout the respiratory cycle and may contribute to dynamic changes in pharyngeal collapsibility. However, whether Upper Airway collapsibility and reflex responses to changes in Airway pressure vary throughout the respiratory cycle in OSA is unclear. Thus, this study quantified differences in Upper Airway collapsibility and genioglossus electromyographic (EMG) activity and reflex responses during different phases of the respiratory cycle. Twelve middle-aged people with OSA (2 female) were fitted with standard polysomnography equipment: a nasal mask, pneumotachograph, two fine-wire intramuscular electrodes into the genioglossus, and a pressure catheter positioned at the epiglottis and a second at the choanae (the collapsible portion of the Upper Airway). At least 20 brief (∼250 ms) pressure pulses (∼-11 cmH2 O at the mask) were delivered every 2-10 breaths during four conditions: (1) early inspiration, (2) mid-inspiration, (3) early expiration, and (4) mid-expiration. Mean baseline genioglossus EMG activity 100 ms prior to pulse delivery and genioglossus reflex responses were quantified for each condition. The Upper Airway collapsibility index (UACI), quantified as 100 × (nadir choanal - epiglottic pressure)/nadir choanal pressure during negative pressure pulses, varied throughout the respiratory cycle (early inspiration = 43 ± 25%, mid-inspiration = 29 ± 19%, early expiration = 83 ± 19% and mid-expiration = 95 ± 11% (mean ± SD) P < 0.01). Genioglossus EMG activity was lower during expiration (e.g. mid-expiration vs. mid-inspiration = 76 ± 23 vs. 127 ± 41% of early-inspiration, P < 0.001). Similarly, genioglossus reflex excitation was delayed (39 ± 11 vs. 23 ± 7 ms, P < 0.001) and reflex excitation amplitude attenuated during mid-expiration versus early inspiration (209 ± 36 vs. 286 ± 80%, P = 0.009). These findings may provide insight into the physiological mechanisms of pharyngeal collapse in OSA.
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genioglossus reflex responses to negative Upper Airway pressure are altered in people with tetraplegia and obstructive sleep apnoea
The Journal of Physiology, 2018Co-Authors: Nirupama Wijesuriya, Amy S Jordan, Peter D. Rochford, Jayne C. Carberry, Laura Gainche, David J Berlowitz, Mariannick Leguen, Fergal J Odonoghue, Warren R RuehlandAbstract:KEY POINTS Protective Reflexes in the throat area (Upper Airway) are crucial for breathing. Impairment of these Reflexes can cause breathing problems during sleep such as obstructive sleep apnoea (OSA). OSA is very common in people with spinal cord injury for unknown reasons. This study shows major changes in protective Reflexes that serve to keep the Upper Airway open in response to suction pressures in people with tetraplegia and OSA. These results help us understand why OSA is so common in people with tetraplegia and provide new insight into how protective Upper Airway Reflexes work more broadly. ABSTRACT More than 60% of people with tetraplegia have obstructive sleep apnoea (OSA). However, the specific causes are unknown. Genioglossus, the largest Upper-Airway dilator muscle, is important in maintaining Upper-Airway patency. Impaired genioglossus muscle function following spinal cord injury may contribute to OSA. This study aimed to determine if genioglossus reflex responses to negative Upper-Airway pressure are altered in people with OSA and tetraplegia compared to non-neurologically impaired able-bodied individuals with OSA. Genioglossus reflex responses measured via intramuscular electrodes to ∼60 brief (250 ms) pulses of negative Upper-Airway pressure (∼-15 cmH2 O at the mask) were compared between 13 participants (2 females) with tetraplegia plus OSA and 9 able-bodied controls (2 females) matched for age and OSA severity. The initial short-latency excitatory reflex response was absent in 6/13 people with tetraplegia and 1/9 controls. Genioglossus reflex inhibition in the absence of excitation was observed in three people with tetraplegia and none of the controls. When the excitatory response was present, it was significantly delayed in the tetraplegia group compared to able-bodied controls: excitation onset latency (mean ± SD) was 32 ± 16 vs. 18 ± 9 ms, P = 0.045; peak excitation latency was 48 ± 17 vs. 33 ± 8 ms, P = 0.038. However, when present, amplitude of the excitation response was not different between groups, 195 ± 26 vs. 219 ± 98% at baseline, P = 0.55. There are major differences in genioglossus reflex morphology and timing in response to rapid changes in Airway pressure in people with tetraplegia and OSA. Altered genioglossus function may contribute to the increased risk of OSA in people with tetraplegia. The precise mechanisms mediating these differences are unknown.
G Smith - One of the best experts on this subject based on the ideXlab platform.
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KEY WORDS
2016Co-Authors: J. A. Langton, P J Murphy, P Barker, A Key, G SmithAbstract:We describe a method for measurement of the sensitivity of Upper Airway Reflexes. The technique is based upon delivery of an irritant chemical stimulus (dilute concentrations of ammonia vapour) to the Upper Airway. The technique is non-invasive and uses equipment which is portable, allowing measurements to be made in the clinical environ
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EFFECT OF ORAL DIAZEPAM ON THE SENSITIVITY OF Upper Airway Reflexesf
2016Co-Authors: P J Murphy, P Barker, J. A. Langton, G SmithAbstract:In a double-blind, cross-over study, we have investigated the effect of oral diazepam 20 mg and placebo on the sensitivity of Upper Airway Reflexes in 10 male volunteers (aged 25-35 yr). Upper Airway reflex sensitivity (UARS) was assessed using small concentrations of ammonia vapour as a stimulus to Upper Airway receptors. A threshold concentration of ammonia, at which reflex glottic closure occurred in response to the ammonia stimulus, was used as a measure of UARS. With diazepam, there was significant depression of UARS from 30 to 150 min after administration. (Br
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effect of age on the sensitivity of Upper Airway Reflexes
BJA: British Journal of Anaesthesia, 1993Co-Authors: R J Erskine, Jeremy Adam. Langton, P J Murphy, G SmithAbstract:We have recorded the threshold concentration of inhaled ammonia vapour required to elicit reflex glottic closure (NH3TR) in 102 healthy, nonsmoking volunteers (39 female) aged 17-96 yr in order to assess the effect of age upon Upper Airway reflex sensitivity. A single measurement of sensitivity was made in each subject using a system delivering small concentrations of ammonia vapour for single intermittent breaths to the Upper Airway and recording glottic closure using an inspiratory pneumotachograph. We found a strong positive correlation between age and NH3TR, indicating a decrease in Upper Airway reflex sensitivity with increasing age. (Br. J. Anaesth. 1993; 70: 574–575)
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measurement of the sensitivity of Upper Airway Reflexes
BJA: British Journal of Anaesthesia, 1993Co-Authors: Jeremy Adam. Langton, P J Murphy, P Barker, A Key, G SmithAbstract:We describe a method for measurement of the sensitivity of Upper Airway Reflexes. The technique is based upon delivery of an irritant chemical stimulus (dilute concentrations of ammonia vapour) to the Upper Airway. The technique is non-invasive and uses equipment which is portable, allowing measurements to be made in the clinical environment. (Br. J. Anaesth. 1993; 70: 126–130
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effect of oral diazepam on the sensitivity of Upper Airway Reflexes
BJA: British Journal of Anaesthesia, 1993Co-Authors: P J Murphy, Jeremy Adam. Langton, P Barker, G SmithAbstract:In a double-blind, cross-over study, we have investigated the effect of oral diazepam 20 mg and placebo on the sensitivity of Upper Airway Reflexes in 10 male volunteers (aged 25–35 yr). Upper Airway reflex sensitivity (UARS) was assessed using small concentrations of ammonia vapour as a stimulus to Upper Airway receptors. A threshold concentration of ammonia, at which reflex glottic closure occurred in response to the ammonia stimulus, was used as a measure of UARS. With diazepam, there was significant depression of UARS from 30 to 150 min after administration. (Br. J. Anaesth. 1993; 70: 131–134)
P J Murphy - One of the best experts on this subject based on the ideXlab platform.
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KEY WORDS
2016Co-Authors: J. A. Langton, P J Murphy, P Barker, A Key, G SmithAbstract:We describe a method for measurement of the sensitivity of Upper Airway Reflexes. The technique is based upon delivery of an irritant chemical stimulus (dilute concentrations of ammonia vapour) to the Upper Airway. The technique is non-invasive and uses equipment which is portable, allowing measurements to be made in the clinical environ
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EFFECT OF ORAL DIAZEPAM ON THE SENSITIVITY OF Upper Airway Reflexesf
2016Co-Authors: P J Murphy, P Barker, J. A. Langton, G SmithAbstract:In a double-blind, cross-over study, we have investigated the effect of oral diazepam 20 mg and placebo on the sensitivity of Upper Airway Reflexes in 10 male volunteers (aged 25-35 yr). Upper Airway reflex sensitivity (UARS) was assessed using small concentrations of ammonia vapour as a stimulus to Upper Airway receptors. A threshold concentration of ammonia, at which reflex glottic closure occurred in response to the ammonia stimulus, was used as a measure of UARS. With diazepam, there was significant depression of UARS from 30 to 150 min after administration. (Br
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sensitivity of Upper Airway Reflexes in cigarette smokers effect of abstinence
BJA: British Journal of Anaesthesia, 1994Co-Authors: R J Erskine, P J Murphy, J. A. LangtonAbstract:In two studies we have compared the Upper Airway reflex sensitivity (UARS) of chronic cigarette smokers with that of non-smokers and also the effect of different periods of abstinence on UARS in the smoking groups. UARS was measured by recording the threshold concentration of dilute ammonia vapour required to stimulate reflex glottic closure. The first study compared UARS in 20 non smokers with 20 smokers, followed by another measurement in the smoking group after 24 h of abstinence. In study two, we measured UARS repeatedly over a period of 3–4 weeks in 16 smokers, half of whom had stopped smoking on day 0. Chronic cigarette smokers were found to have significantly greater UARS compared with non-smokers; the sensitivity was unaltered after 24 h of abstinence but was found to reduce over several days, the change commencing between 24 and 48 h, with most achieving a consistent change within 10 days.
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the effect of intravenously administered diazepam midazolam and flumazenil on the sensitivity of Upper Airway Reflexes
Anaesthesia, 1994Co-Authors: P J Murphy, R Erskine, Jeremy Adam. LangtonAbstract:Abstract This investigation studied the effect of two intravenous benzodiazepines and the specific reversal agent, flumazenil, on the sensitivity of Upper Airway Reflexes. In a blinded, randomised, crossover study, we have investigated the effect of a single dose of diazepam ('Diazemuls') (0.2 mg.kg-1) and midazolam (0.07 mg.kg-1), both given intravenously on the sensitivity of Upper Airway Reflexes in eight male volunteers. Reflex sensitivity was assessed by identification of reflex glottic closure in response to a threshold concentration of inhaled ammonia vapour. Both diazepam and midazolam produced significant depression of Upper Airway reflex sensitivity. This was maximum with both drugs within 10 min of administration, but baseline sensitivity was regained within 60 min. Flumazenil (300 micrograms) administered 10 min after midazolam, resulted in significant reversal of the Upper Airway reflex sensitivity depression.
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effect of age on the sensitivity of Upper Airway Reflexes
BJA: British Journal of Anaesthesia, 1993Co-Authors: R J Erskine, Jeremy Adam. Langton, P J Murphy, G SmithAbstract:We have recorded the threshold concentration of inhaled ammonia vapour required to elicit reflex glottic closure (NH3TR) in 102 healthy, nonsmoking volunteers (39 female) aged 17-96 yr in order to assess the effect of age upon Upper Airway reflex sensitivity. A single measurement of sensitivity was made in each subject using a system delivering small concentrations of ammonia vapour for single intermittent breaths to the Upper Airway and recording glottic closure using an inspiratory pneumotachograph. We found a strong positive correlation between age and NH3TR, indicating a decrease in Upper Airway reflex sensitivity with increasing age. (Br. J. Anaesth. 1993; 70: 574–575)
Danny J Eckert - One of the best experts on this subject based on the ideXlab platform.
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changes in pharyngeal collapsibility and genioglossus reflex responses to negative pressure during the respiratory cycle in obstructive sleep apnoea
The Journal of Physiology, 2020Co-Authors: Amal M Osman, Simon C. Gandevia, Jane E. Butler, Jayne C. Carberry, Danny J EckertAbstract:KEY POINTS Impaired pharyngeal anatomy and increased Airway collapsibility is a major cause of obstructive sleep apnoea (OSA) and a mediator of its severity. Upper Airway Reflexes to changes in Airway pressure provide important protection against Airway closure. This study shows increased pharyngeal collapsibility and attenuated genioglossus reflex responses during expiration in people with OSA. ABSTRACT Upper Airway collapse contributes to obstructive sleep apnoea (OSA) pathogenesis. Pharyngeal dilator muscle activity varies throughout the respiratory cycle and may contribute to dynamic changes in pharyngeal collapsibility. However, whether Upper Airway collapsibility and reflex responses to changes in Airway pressure vary throughout the respiratory cycle in OSA is unclear. Thus, this study quantified differences in Upper Airway collapsibility and genioglossus electromyographic (EMG) activity and reflex responses during different phases of the respiratory cycle. Twelve middle-aged people with OSA (2 female) were fitted with standard polysomnography equipment: a nasal mask, pneumotachograph, two fine-wire intramuscular electrodes into the genioglossus, and a pressure catheter positioned at the epiglottis and a second at the choanae (the collapsible portion of the Upper Airway). At least 20 brief (∼250 ms) pressure pulses (∼-11 cmH2 O at the mask) were delivered every 2-10 breaths during four conditions: (1) early inspiration, (2) mid-inspiration, (3) early expiration, and (4) mid-expiration. Mean baseline genioglossus EMG activity 100 ms prior to pulse delivery and genioglossus reflex responses were quantified for each condition. The Upper Airway collapsibility index (UACI), quantified as 100 × (nadir choanal - epiglottic pressure)/nadir choanal pressure during negative pressure pulses, varied throughout the respiratory cycle (early inspiration = 43 ± 25%, mid-inspiration = 29 ± 19%, early expiration = 83 ± 19% and mid-expiration = 95 ± 11% (mean ± SD) P < 0.01). Genioglossus EMG activity was lower during expiration (e.g. mid-expiration vs. mid-inspiration = 76 ± 23 vs. 127 ± 41% of early-inspiration, P < 0.001). Similarly, genioglossus reflex excitation was delayed (39 ± 11 vs. 23 ± 7 ms, P < 0.001) and reflex excitation amplitude attenuated during mid-expiration versus early inspiration (209 ± 36 vs. 286 ± 80%, P = 0.009). These findings may provide insight into the physiological mechanisms of pharyngeal collapse in OSA.
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changes in pharyngeal collapsibility and genioglossus reflex responses to negative pressure during the respiratory cycle in obstructive sleep apnoea
The Journal of Physiology, 2020Co-Authors: Amal M Osman, Simon C. Gandevia, Jane E. Butler, Jayne C. Carberry, Danny J EckertAbstract:KEY POINTS: Impaired pharyngeal anatomy and increased Airway collapsibility is a major cause of obstructive sleep apnoea (OSA) and a mediator of its severity. Upper Airway Reflexes to changes in Airway pressure provide important protection against Airway closure. This study shows increased pharyngeal collapsibility and attenuated genioglossus reflex responses during expiration in people with OSA. ABSTRACT: Upper Airway collapse contributes to obstructive sleep apnoea (OSA) pathogenesis. Pharyngeal dilator muscle activity varies throughout the respiratory cycle and may contribute to dynamic changes in pharyngeal collapsibility. However, whether Upper Airway collapsibility and reflex responses to changes in Airway pressure vary throughout the respiratory cycle in OSA is unclear. Thus, this study quantified differences in Upper Airway collapsibility and genioglossus electromyographic (EMG) activity and reflex responses during different phases of the respiratory cycle. Twelve middle-aged people with OSA (2 female) were fitted with standard polysomnography equipment: a nasal mask, pneumotachograph, two fine-wire intramuscular electrodes into the genioglossus, and a pressure catheter positioned at the epiglottis and a second at the choanae (the collapsible portion of the Upper Airway). At least 20 brief ( approximately 250 ms) pressure pulses ( approximately -11 cmH2 O at the mask) were delivered every 2-10 breaths during four conditions: (1) early inspiration, (2) mid-inspiration, (3) early expiration, and (4) mid-expiration. Mean baseline genioglossus EMG activity 100 ms prior to pulse delivery and genioglossus reflex responses were quantified for each condition. The Upper Airway collapsibility index (UACI), quantified as 100 x (nadir choanal - epiglottic pressure)/nadir choanal pressure during negative pressure pulses, varied throughout the respiratory cycle (early inspiration = 43 +/- 25%, mid-inspiration = 29 +/- 19%, early expiration = 83 +/- 19% and mid-expiration = 95 +/- 11% (mean +/- SD) P < 0.01). Genioglossus EMG activity was lower during expiration (e.g. mid-expiration vs. mid-inspiration = 76 +/- 23 vs. 127 +/- 41% of early-inspiration, P < 0.001). Similarly, genioglossus reflex excitation was delayed (39 +/- 11 vs. 23 +/- 7 ms, P < 0.001) and reflex excitation amplitude attenuated during mid-expiration versus early inspiration (209 +/- 36 vs. 286 +/- 80%, P = 0.009). These findings may provide insight into the physiological mechanisms of pharyngeal collapse in OSA.
Jeremy Adam. Langton - One of the best experts on this subject based on the ideXlab platform.
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2 Upper Airway Reflexes
Baillière's clinical anaesthesiology, 1995Co-Authors: Jeremy Adam. LangtonAbstract:Summary The maintenance of a clear unobstructed Upper Airway and the rapid return of normal laryngeal Reflexes after the end of general anaesthesia form two of the most fundamental principles of modern anaesthetic practice. Upper Airway Reflexes are of considerable importance to clinical anaesthetists. The sensitivity of the Upper Airway Reflexes are important during induction of anaesthesia, when heightened Upper Airway Reflexes may lead to the development of life threatening laryngospasm. Following anaesthesia the larynx plays a primary role in protecting the lungs from aspiration of foreign material. The irritant nature of inhalation anaesthetic agents varies, with halothane being one of the least irritant. Newer agents including isoflurane and desflurane have been found to be associated with a much higher incidence of Airway irritation. The intravenous anaesthetic induction agents thiopentone and propofol seem to have different actions on the sensitivity of Upper Airway Reflexes during induction of anaesthesia, the Upper Airway appearing to be less irritable following propofol. Laryngospasm is a common and potentially dangerous complication of general anaesthesia, the incidence is higher in young children particularly between the ages of 1 and 3 months. Upper respiratory tract infection increases the incidence of laryngospasm. This is thought to be due to the viral infection causing shedding of epithelial cells, leading to increased exposure of intraepithelial sensory receptors to inhaled irritants. Histologically, sensory nerve fibres are found in almost all areas of the laryngeal mucosa. A particularly high density of sensory free nerve endings are found in the posterior supraglottis. Stimulation of irritant receptors in the Upper respiratory tract causes a reflex motor response, afferent signals travel in the vagus nerve and project centrally to the caudal and posterior parts of the nucleus tractus solitarius. The efferent response results in vocal cord closure, changes in respiratory rhythm and coughing, which together act to protect the lower Airway from foreign material.
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the effect of ethyl alcohol on the sensitivity of Upper Airway Reflexes
Alcohol and Alcoholism, 1994Co-Authors: R Erskine, Paul Murphy, Jeremy Adam. LangtonAbstract:The effect of ethyl alcohol on Upper Airway reflex sensitivity (UARS) has not been previously investigated in humans. Using a technique that we have previously described, intermittent breaths of low concentrations of ammonia vapour were used to measure the effect of ethyl alcohol 0.55-0.66 g/kg on UARS in ten healthy male volunteers. The depression of Upper Airway Reflexes that occurred following ingestion of ethyl alcohol was maximum at 60 min and returned to baseline by 150 min. This dose of ethyl alcohol was insufficient to produce statistically significant depression of UARS. The blood alcohol levels achieved showed a wide range with a mean of 78.9 mg/100 ml (SEM 10.3). Individual subjects who had blood alcohol levels in excess of 100 mg/100 ml displayed much greater depression of UARS. In conclusion, 0.55-0.66 g/kg ethyl alcohol given to healthy male volunteers does not produce significant depression of UARS as measured using an ammonia stimulus technique.
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the effect of intravenously administered diazepam midazolam and flumazenil on the sensitivity of Upper Airway Reflexes
Anaesthesia, 1994Co-Authors: P J Murphy, R Erskine, Jeremy Adam. LangtonAbstract:Abstract This investigation studied the effect of two intravenous benzodiazepines and the specific reversal agent, flumazenil, on the sensitivity of Upper Airway Reflexes. In a blinded, randomised, crossover study, we have investigated the effect of a single dose of diazepam ('Diazemuls') (0.2 mg.kg-1) and midazolam (0.07 mg.kg-1), both given intravenously on the sensitivity of Upper Airway Reflexes in eight male volunteers. Reflex sensitivity was assessed by identification of reflex glottic closure in response to a threshold concentration of inhaled ammonia vapour. Both diazepam and midazolam produced significant depression of Upper Airway reflex sensitivity. This was maximum with both drugs within 10 min of administration, but baseline sensitivity was regained within 60 min. Flumazenil (300 micrograms) administered 10 min after midazolam, resulted in significant reversal of the Upper Airway reflex sensitivity depression.
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Upper Airway Reflexes and anaesthesia.
1994Co-Authors: Jeremy Adam. LangtonAbstract:In this thesis I describe the importance of Upper Airway Reflexes to anaesthesia and discuss the anatomy and physiology relating to normal Upper Airway function and protective Airway Reflexes. The measurement of Upper Airway Reflexes has not previously been fully investigated in humans and I describe the background to the measurement of the sensitivity of Upper Airway Reflexes and outline a technique to measure the sensitivity of Upper Airway Reflexes. Using this technique I have explored the changes in the sensitivity of Upper Airway Reflexes that occur due to ageing and following administration of drugs. Smokers are known to have an increased incidence of coughing and laryngospasm on induction of anaesthesia. The effect of cigarette smoking and the changes in the sensitivity of Upper Airway Reflexes which occur on stopping smoking were investigated. Benzodiazepines are commonly used for premedication and intravenously to produce sedation, the effects of these drugs on the sensitivity of Upper Airway Reflexes was examined as well as the effect of the reversal agent flumazenil. Patients who have consumed ethyl alcohol may readily aspirate gastric contents with fatal consequences. The effect of ethyl alcohol on the sensitivity of Upper Airway Reflexes is measured and the relevance to anaesthetists providing emergency anaesthesia is discussed. The inhalation of nitrous oxide and oxygen mixtures is frequently used for analgesic purposes in groups of patients known to have full stomachs and who are at risk from aspiration of gastric contents. I have studied the effects of nitrous oxide and oxygen mixtures on Upper Airway Reflexes. The final chapter of this thesis uses a fibre-optic method of measuring the movements of the vocal cords on induction of anaesthesia, to examine the actions of two commonly used anaesthetic induction agents on the sensitivity of Upper Airway Reflexes
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effect of age on the sensitivity of Upper Airway Reflexes
BJA: British Journal of Anaesthesia, 1993Co-Authors: R J Erskine, Jeremy Adam. Langton, P J Murphy, G SmithAbstract:We have recorded the threshold concentration of inhaled ammonia vapour required to elicit reflex glottic closure (NH3TR) in 102 healthy, nonsmoking volunteers (39 female) aged 17-96 yr in order to assess the effect of age upon Upper Airway reflex sensitivity. A single measurement of sensitivity was made in each subject using a system delivering small concentrations of ammonia vapour for single intermittent breaths to the Upper Airway and recording glottic closure using an inspiratory pneumotachograph. We found a strong positive correlation between age and NH3TR, indicating a decrease in Upper Airway reflex sensitivity with increasing age. (Br. J. Anaesth. 1993; 70: 574–575)
