Jason Kirkness - Academia.edu (original) (raw)
Papers by Jason Kirkness
Journal of applied physiology (Bethesda, Md. : 1985), Jan 5, 2015
Patients with COPD exhibit increases in lung volume due to expiratory airflow limitation (EFL). I... more Patients with COPD exhibit increases in lung volume due to expiratory airflow limitation (EFL). Increases in lung volumes may affect upper airway patency and compensatory responses to inspiratory flow limitation (IFL) during sleep. We hypothesized that COPD patients have less collapsible airways inversely proportional to their lung volumes; and that the presence of EFL limit duty cycle responses to defend ventilation in the presence of IFL. We enrolled 18 COPD patients and 18 controls, matched by age, body mass index, sex and OSA disease severity. Sleep studies including quantitative assessment of airflow at varies nasal pressure levels were conducted to determine upper airway mechanical properties (passive Pcrit) and for quantifying respiratory timing response to experimentally induced IFL. COPD patients had lower passive Pcrit than their matched controls (COPD: -2.8±0.9 cmH2O; Controls: -0.5±0.5 cmH2O, p=0.03) and there was an inverse relationship of subject's functional resid...
Annals of the American Thoracic Society, 2015
We describe a case of a 48-year-old woman with an incidental finding on a research polysomnogram,... more We describe a case of a 48-year-old woman with an incidental finding on a research polysomnogram, which posed an interesting differential diagnosis elucidated with the aid of advanced diagnostic methods. This case illustrates the utility of quantitative airflow assessment during sleep in the evaluation of involuntary upper airway phasic activity.
D100. ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY COLLAPSE, 2011
Page 1. / Mini Symposium / Wednesday, May D100 ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY CO... more Page 1. / Mini Symposium / Wednesday, May D100 ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY COLLAPSE 18/2:00 PM-4:30 PM / Korbel Ballroom 2A-3A (Lower Level), Colorado Convention Center Mechanical ...
Sleep, 2011
The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant o... more The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant of the severity of upper airway obstruction during sleep. We examined the performance characteristics of the passive and active P(CRIT) by examining both within-night and between-night variability in the measurements. We studied 54 sleep apnea patients (39 men, 15 women) and 34 normal subjects (20 men, 14 women) on either 1 or 2 nights during sleep. The P(CRIT) was measured during relative hypotonia ("passive" state) or during periods of sustained upper airway obstruction used to recruit upper airway neuromuscular responses ("active" state) within- and between-nights. In a subgroup of 10 normal subjects, we performed repeated measurements during hypnotic-induced sleep. Bland-Altman analyses were used to determine the within-night and between-night reliability of the P(CRIT) measurements. There were no significant within-night or between-night differences for the mean p...
Journal of applied physiology (Bethesda, Md. : 1985), 2008
Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms ... more Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms by which these factors increase sleep apnea susceptibility are not entirely understood. This study examined the interrelationships between sleep apnea risk factors, upper airway mechanics, and sleep apnea susceptibility. In 164 (86 men, 78 women) participants with and without sleep apnea, upper airway pressure-flow relationships were characterized to determine their mechanical properties [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] during non-rapid eye movement sleep. In multiple linear regression analyses, the effects of body mass index and age on passive Pcrit were determined in each sex. A subset of men and women matched by body mass index, age, and disease severity was used to determine the sex effect on passive Pcrit. The passive Pcrit was 1.9 cmH(2)O [95% confidence interval (CI): 0.1-3.6 cmH(2)O] lower in women than men after matching for body mass ind...
Sleep, 2010
To describe sex differences in the associations between severity of obstructive sleep apnea (OSA)... more To describe sex differences in the associations between severity of obstructive sleep apnea (OSA) and measures of obesity in body regions defined using both dual-energy absorptiometry and traditional anthropometric measures in a sleep-clinic sample. A prospective case-series observational study. The Western Australian Sleep Health Study operating out of the Sir Charles Gairdner Hospital Sleep Clinic, Perth, Western Australia. Newly referred clinic patients (60 men, 36 women) suspected of having OSA. N/A. Obstructive sleep apnea severity was defined by apnea-hypopnoea index from laboratory-based overnight polysomnography. Body mass index, neck, waist and hip circumference, neck-to-waist ratio, and waist-to-hip ratio were measured. Dual energy absorptiometry measurements included percentage fat and lean tissue. Multivariate regression models for each sex were developed. In women, percentage of fat in the neck region and body mass index together explained 33% of the variance in apnea-h...
A109. UPPER AIRWAY CONTROL, STRUCTURE AND FUNCTION, 2012
C96. WHAT'S NEW IN PEDIATRIC SLEEP?, 2011
A68. UPPER AIRWAY AND RESPIRATORY PHYSIOLOGY, 2010
19th International Conference on Optical Fibre Sensors, 2008
Anatomical optical coherence tomography (aOCT) is an endoscopic imaging modality that can be used... more Anatomical optical coherence tomography (aOCT) is an endoscopic imaging modality that can be used to quantify size and shape of the upper airway. We report the application of respiratory gating to aOCT images. Our results show that respiratory gating can reduce motion artefact in upper airway images. Using an error metric based on distance to the dominant reflection in each A-scan, we found notable improvements when the breath cycle was partitioned into approximately four gates, but only minor improvements as the number of gates was further increased.
Clinics in Chest Medicine, 2014
Sleep is a potentially vulnerable state for the respiratory system. Respiratory drive is determin... more Sleep is a potentially vulnerable state for the respiratory system. Respiratory drive is determined by a central respiratory generator located within the brainstem. Withdrawal of wakefulness stimuli and the initiation of active sleep processes results in ventilation being determined primarily by metabolic demand. The respiratory system is regulated by central and peripheral chemoreceptors and mechanoreceptors that provide negative feedback to maintain ventilation. Sleep onset results in alterations in upper and lower airway physiology to maintain eucapnia.
Sleep and Breathing, 2014
Background Nasal insufflation (NI) is a novel treatment method that has been introduced for impro... more Background Nasal insufflation (NI) is a novel treatment method that has been introduced for improving respiration during sleep. NI's warmed and humidified nasal airflow provides ventilatory assistance delivered as a rapidly dispersed pressure head, with minimal side wall pressures, that may affect treatment tolerability. The aim of the current study was to investigate objective and subjective adherence rates for NI therapy in mild to moderate obstructive sleep apnea (OSA). Methods Ten patients (three men and seven women; age, 51.3 ±9.6 years; BMI, 32.2±7.7 kg/m 2 [mean±sd]) with recently diagnosed mild to moderate OSA (10.9±5.8 events/h) were investigated. A crossover design was used to compare adherence to NI and continuous positive airway pressure (CPAP) therapy using a range of objective and subjective measurements. Objective (sleep efficiency (%) and arousal indices (arousal/h)) and subjective evaluations of sleep quality were carried out each night in the laboratory. During in-home treatment, adherence for both therapies was assessed objectively (time on therapy) and subjectively (self-reported sleep diary). Results Objectively derived adherence values were comparable for CPAP and NI, with both treatment devices sharing similar usage per night (3.5±2.5 vs. 3.6±1.6 h/night; respectively) and the number of nights with at least 4 h of treatment (5.5±4.3 vs. 6.8±3.3 nights/trial, respectively). Self-reported adherence was significantly higher than objectively assessed adherence (p<0.03). Conclusions This study showed similar adherence to NI and CPAP over a short period of usage. A randomized clinical trial is now essential for determining the comparative effectiveness of NI therapy in relation to treatment with CPAP.
A109. UPPER AIRWAY CONTROL, STRUCTURE AND FUNCTION, 2012
Pathogenesis, Diagnosis and Treatment, 2011
Progress in Respiratory Research, 2006
Treatment options for snoring and upper airway resistance syndrome are hampered by either low com... more Treatment options for snoring and upper airway resistance syndrome are hampered by either low compliance or low efficacy. Therefore, refinements in these therapeutic strategies are needed. The understanding of the pathogenic factors of upper airway obstruction and an individual’s compensatory responses to defend ventilation in face of upper airway obstruction may help to develop more effective and less intrusive treatment
The Journal of Physiology, 2003
Research in Nursing & Health, 1995
Lazarus and Folkman's (1984) theory of stress, coping, and adaptation served as the frame... more Lazarus and Folkman's (1984) theory of stress, coping, and adaptation served as the framework for a path model of quality of life in chronic obstructive pulmonary disease (COPD). It was hypothesized that psychosocial variables (depression, anxiety, self-esteem, optimism, and social support) would mediate the effects of demographic (age, socioeconomic status) and disease (dyspnea, disease severity, and functional status) variables on life quality in COPD. Interview, pulmonary function, and 6-minute walk test data obtained from 126 subjects with COPD resulted in support for the majority of the hypothesized relationships. Variables having direct effects on life quality were self-esteem, depression, social support, and age. Anxiety and optimism did not have their hypothesized effects on quality of life, suggesting the need to reconsider their importance in influencing life quality in COPD.
Physiological Measurement, 2005
Upper airway luminal patency is influenced by a number of factors including: intraluminal air pre... more Upper airway luminal patency is influenced by a number of factors including: intraluminal air pressure, upper airway dilator muscle activity, surrounding extraluminal tissue pressure and surface tension acting within the liquid layer lining the upper airway. In this study we examine the performance characteristics for the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;pull-off&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; force method for measuring the surface tension (gamma) of liquids. This method is then used to examine the gamma of the liquid lining the oro-pharynx in awake human subjects. The gamma of UAL samples (approximately 0.2 microL) obtained from the posterior pharyngeal wall was quantified using the pull-off force technique in which gamma is measured as the force required to separate two curved silica discs bridged by the liquid sample. Pull-off force measurement was not influenced by sample volumes or under different temperature or humidity conditions. The coefficients of variation for repeated measurements using the pull-off force technique for the three standard liquids ranged from 1.2% to 5.6%. The pull-off method tended to give slightly lower values than the Wihelmy balance method with the mean difference being 2.4 +/- 1.8 mN m(-1). For the group, the gamma of saliva was 59.2 +/- 0.6 mN m(-1) (CV 4.9 +/- 0.9%) for five measurements of a single sample. There was no significant relationship between the measured gamma values for five subjects measured on five separate days and the day of collection of the sample for any of the subjects or the group as a whole (both p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.6). There was no significant difference (p = 0.53, ANOVA) between the gamma values for samples obtained from under the tongue (61.6 +/- 1.7 mN m(-1)), at the oral surface of the soft palate (56.1 +/- 3.2 mN m(-1)) and from the posterior oro-pharyngeal wall (58.1 +/- 2.4 mN m(-1)). The pull-off force method provides adequate reproducibility to be able to measure the gamma of UAL. In healthy humans the gamma of UAL is similar to that of saliva.
Journal of Oral Rehabilitation, 2013
Surface tension may have important role for maintaining upper airway patency in patients with obs... more Surface tension may have important role for maintaining upper airway patency in patients with obstructive sleep apnoea. It has been demonstrated that elevated surface tension increases the pharyngeal pressures required to reopen the upper airway following collapse. The aim of the study was to evaluate the associations between the concentrations of endogenous surfactants in saliva with indices of upper airway patency in obstructive sleep apnoea. We studied 20 male patients with obstructive sleep apnoea (age: 60·3 ± 10·3 years; BMI: 25·9 ± 4·6 kg m(-2); AHI: 41·5 ± 18·6 events h(-1)). We obtained 100-μL samples of saliva prior to overnight polysomnographic sleep study. The surface tension was determined using the pull-off force technique. The concentration of phosphatidylcholine (PC) was evaluated by liquid chromatography-mass spectrometry (LC-MS/MS). Regression analysis between apnoea, hypopnoea and apnoea/hypopnoea indices and the ratio of hypopnoea time/total disordered breathing time (HT/DBT) with surface tension and PC were performed. P < 0·05 was considered significant. The mean saliva surface tension was 48·8 ± 8·0 mN m(-1) and PC concentration was 15·7 ± 11·1 nM. The surface tension was negatively correlated with the PC concentration (r = -0·48, P = 0·03). There was a significant positive correlation between surface tension with hypopnoea index (r = 0·50, P = 0·03) and HT/DBT (r = 0·6, P = 0·006), but not apnoea or apnoea/hypopnoea index (P > 0·11). Similarly, PC concentration negatively correlated with hypopnoea index (r = -0·45, P = 0·04) and HT/DBT (r = -0·6, P = 0·004), but not with apnoea index or AHI (P > 0·08). An increase in salivary PC concentration may increase upper airway patency in obstructive sleep apnoea through a reduction in surface tension.
Journal of applied physiology (Bethesda, Md. : 1985), Jan 5, 2015
Patients with COPD exhibit increases in lung volume due to expiratory airflow limitation (EFL). I... more Patients with COPD exhibit increases in lung volume due to expiratory airflow limitation (EFL). Increases in lung volumes may affect upper airway patency and compensatory responses to inspiratory flow limitation (IFL) during sleep. We hypothesized that COPD patients have less collapsible airways inversely proportional to their lung volumes; and that the presence of EFL limit duty cycle responses to defend ventilation in the presence of IFL. We enrolled 18 COPD patients and 18 controls, matched by age, body mass index, sex and OSA disease severity. Sleep studies including quantitative assessment of airflow at varies nasal pressure levels were conducted to determine upper airway mechanical properties (passive Pcrit) and for quantifying respiratory timing response to experimentally induced IFL. COPD patients had lower passive Pcrit than their matched controls (COPD: -2.8±0.9 cmH2O; Controls: -0.5±0.5 cmH2O, p=0.03) and there was an inverse relationship of subject's functional resid...
Annals of the American Thoracic Society, 2015
We describe a case of a 48-year-old woman with an incidental finding on a research polysomnogram,... more We describe a case of a 48-year-old woman with an incidental finding on a research polysomnogram, which posed an interesting differential diagnosis elucidated with the aid of advanced diagnostic methods. This case illustrates the utility of quantitative airflow assessment during sleep in the evaluation of involuntary upper airway phasic activity.
D100. ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY COLLAPSE, 2011
Page 1. / Mini Symposium / Wednesday, May D100 ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY CO... more Page 1. / Mini Symposium / Wednesday, May D100 ANATOMIC AND NEUROMUSCULAR INFLUENCES ON AIRWAY COLLAPSE 18/2:00 PM-4:30 PM / Korbel Ballroom 2A-3A (Lower Level), Colorado Convention Center Mechanical ...
Sleep, 2011
The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant o... more The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant of the severity of upper airway obstruction during sleep. We examined the performance characteristics of the passive and active P(CRIT) by examining both within-night and between-night variability in the measurements. We studied 54 sleep apnea patients (39 men, 15 women) and 34 normal subjects (20 men, 14 women) on either 1 or 2 nights during sleep. The P(CRIT) was measured during relative hypotonia ("passive" state) or during periods of sustained upper airway obstruction used to recruit upper airway neuromuscular responses ("active" state) within- and between-nights. In a subgroup of 10 normal subjects, we performed repeated measurements during hypnotic-induced sleep. Bland-Altman analyses were used to determine the within-night and between-night reliability of the P(CRIT) measurements. There were no significant within-night or between-night differences for the mean p...
Journal of applied physiology (Bethesda, Md. : 1985), 2008
Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms ... more Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms by which these factors increase sleep apnea susceptibility are not entirely understood. This study examined the interrelationships between sleep apnea risk factors, upper airway mechanics, and sleep apnea susceptibility. In 164 (86 men, 78 women) participants with and without sleep apnea, upper airway pressure-flow relationships were characterized to determine their mechanical properties [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] during non-rapid eye movement sleep. In multiple linear regression analyses, the effects of body mass index and age on passive Pcrit were determined in each sex. A subset of men and women matched by body mass index, age, and disease severity was used to determine the sex effect on passive Pcrit. The passive Pcrit was 1.9 cmH(2)O [95% confidence interval (CI): 0.1-3.6 cmH(2)O] lower in women than men after matching for body mass ind...
Sleep, 2010
To describe sex differences in the associations between severity of obstructive sleep apnea (OSA)... more To describe sex differences in the associations between severity of obstructive sleep apnea (OSA) and measures of obesity in body regions defined using both dual-energy absorptiometry and traditional anthropometric measures in a sleep-clinic sample. A prospective case-series observational study. The Western Australian Sleep Health Study operating out of the Sir Charles Gairdner Hospital Sleep Clinic, Perth, Western Australia. Newly referred clinic patients (60 men, 36 women) suspected of having OSA. N/A. Obstructive sleep apnea severity was defined by apnea-hypopnoea index from laboratory-based overnight polysomnography. Body mass index, neck, waist and hip circumference, neck-to-waist ratio, and waist-to-hip ratio were measured. Dual energy absorptiometry measurements included percentage fat and lean tissue. Multivariate regression models for each sex were developed. In women, percentage of fat in the neck region and body mass index together explained 33% of the variance in apnea-h...
A109. UPPER AIRWAY CONTROL, STRUCTURE AND FUNCTION, 2012
C96. WHAT'S NEW IN PEDIATRIC SLEEP?, 2011
A68. UPPER AIRWAY AND RESPIRATORY PHYSIOLOGY, 2010
19th International Conference on Optical Fibre Sensors, 2008
Anatomical optical coherence tomography (aOCT) is an endoscopic imaging modality that can be used... more Anatomical optical coherence tomography (aOCT) is an endoscopic imaging modality that can be used to quantify size and shape of the upper airway. We report the application of respiratory gating to aOCT images. Our results show that respiratory gating can reduce motion artefact in upper airway images. Using an error metric based on distance to the dominant reflection in each A-scan, we found notable improvements when the breath cycle was partitioned into approximately four gates, but only minor improvements as the number of gates was further increased.
Clinics in Chest Medicine, 2014
Sleep is a potentially vulnerable state for the respiratory system. Respiratory drive is determin... more Sleep is a potentially vulnerable state for the respiratory system. Respiratory drive is determined by a central respiratory generator located within the brainstem. Withdrawal of wakefulness stimuli and the initiation of active sleep processes results in ventilation being determined primarily by metabolic demand. The respiratory system is regulated by central and peripheral chemoreceptors and mechanoreceptors that provide negative feedback to maintain ventilation. Sleep onset results in alterations in upper and lower airway physiology to maintain eucapnia.
Sleep and Breathing, 2014
Background Nasal insufflation (NI) is a novel treatment method that has been introduced for impro... more Background Nasal insufflation (NI) is a novel treatment method that has been introduced for improving respiration during sleep. NI's warmed and humidified nasal airflow provides ventilatory assistance delivered as a rapidly dispersed pressure head, with minimal side wall pressures, that may affect treatment tolerability. The aim of the current study was to investigate objective and subjective adherence rates for NI therapy in mild to moderate obstructive sleep apnea (OSA). Methods Ten patients (three men and seven women; age, 51.3 ±9.6 years; BMI, 32.2±7.7 kg/m 2 [mean±sd]) with recently diagnosed mild to moderate OSA (10.9±5.8 events/h) were investigated. A crossover design was used to compare adherence to NI and continuous positive airway pressure (CPAP) therapy using a range of objective and subjective measurements. Objective (sleep efficiency (%) and arousal indices (arousal/h)) and subjective evaluations of sleep quality were carried out each night in the laboratory. During in-home treatment, adherence for both therapies was assessed objectively (time on therapy) and subjectively (self-reported sleep diary). Results Objectively derived adherence values were comparable for CPAP and NI, with both treatment devices sharing similar usage per night (3.5±2.5 vs. 3.6±1.6 h/night; respectively) and the number of nights with at least 4 h of treatment (5.5±4.3 vs. 6.8±3.3 nights/trial, respectively). Self-reported adherence was significantly higher than objectively assessed adherence (p<0.03). Conclusions This study showed similar adherence to NI and CPAP over a short period of usage. A randomized clinical trial is now essential for determining the comparative effectiveness of NI therapy in relation to treatment with CPAP.
A109. UPPER AIRWAY CONTROL, STRUCTURE AND FUNCTION, 2012
Pathogenesis, Diagnosis and Treatment, 2011
Progress in Respiratory Research, 2006
Treatment options for snoring and upper airway resistance syndrome are hampered by either low com... more Treatment options for snoring and upper airway resistance syndrome are hampered by either low compliance or low efficacy. Therefore, refinements in these therapeutic strategies are needed. The understanding of the pathogenic factors of upper airway obstruction and an individual’s compensatory responses to defend ventilation in face of upper airway obstruction may help to develop more effective and less intrusive treatment
The Journal of Physiology, 2003
Research in Nursing & Health, 1995
Lazarus and Folkman's (1984) theory of stress, coping, and adaptation served as the frame... more Lazarus and Folkman's (1984) theory of stress, coping, and adaptation served as the framework for a path model of quality of life in chronic obstructive pulmonary disease (COPD). It was hypothesized that psychosocial variables (depression, anxiety, self-esteem, optimism, and social support) would mediate the effects of demographic (age, socioeconomic status) and disease (dyspnea, disease severity, and functional status) variables on life quality in COPD. Interview, pulmonary function, and 6-minute walk test data obtained from 126 subjects with COPD resulted in support for the majority of the hypothesized relationships. Variables having direct effects on life quality were self-esteem, depression, social support, and age. Anxiety and optimism did not have their hypothesized effects on quality of life, suggesting the need to reconsider their importance in influencing life quality in COPD.
Physiological Measurement, 2005
Upper airway luminal patency is influenced by a number of factors including: intraluminal air pre... more Upper airway luminal patency is influenced by a number of factors including: intraluminal air pressure, upper airway dilator muscle activity, surrounding extraluminal tissue pressure and surface tension acting within the liquid layer lining the upper airway. In this study we examine the performance characteristics for the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;pull-off&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; force method for measuring the surface tension (gamma) of liquids. This method is then used to examine the gamma of the liquid lining the oro-pharynx in awake human subjects. The gamma of UAL samples (approximately 0.2 microL) obtained from the posterior pharyngeal wall was quantified using the pull-off force technique in which gamma is measured as the force required to separate two curved silica discs bridged by the liquid sample. Pull-off force measurement was not influenced by sample volumes or under different temperature or humidity conditions. The coefficients of variation for repeated measurements using the pull-off force technique for the three standard liquids ranged from 1.2% to 5.6%. The pull-off method tended to give slightly lower values than the Wihelmy balance method with the mean difference being 2.4 +/- 1.8 mN m(-1). For the group, the gamma of saliva was 59.2 +/- 0.6 mN m(-1) (CV 4.9 +/- 0.9%) for five measurements of a single sample. There was no significant relationship between the measured gamma values for five subjects measured on five separate days and the day of collection of the sample for any of the subjects or the group as a whole (both p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.6). There was no significant difference (p = 0.53, ANOVA) between the gamma values for samples obtained from under the tongue (61.6 +/- 1.7 mN m(-1)), at the oral surface of the soft palate (56.1 +/- 3.2 mN m(-1)) and from the posterior oro-pharyngeal wall (58.1 +/- 2.4 mN m(-1)). The pull-off force method provides adequate reproducibility to be able to measure the gamma of UAL. In healthy humans the gamma of UAL is similar to that of saliva.
Journal of Oral Rehabilitation, 2013
Surface tension may have important role for maintaining upper airway patency in patients with obs... more Surface tension may have important role for maintaining upper airway patency in patients with obstructive sleep apnoea. It has been demonstrated that elevated surface tension increases the pharyngeal pressures required to reopen the upper airway following collapse. The aim of the study was to evaluate the associations between the concentrations of endogenous surfactants in saliva with indices of upper airway patency in obstructive sleep apnoea. We studied 20 male patients with obstructive sleep apnoea (age: 60·3 ± 10·3 years; BMI: 25·9 ± 4·6 kg m(-2); AHI: 41·5 ± 18·6 events h(-1)). We obtained 100-μL samples of saliva prior to overnight polysomnographic sleep study. The surface tension was determined using the pull-off force technique. The concentration of phosphatidylcholine (PC) was evaluated by liquid chromatography-mass spectrometry (LC-MS/MS). Regression analysis between apnoea, hypopnoea and apnoea/hypopnoea indices and the ratio of hypopnoea time/total disordered breathing time (HT/DBT) with surface tension and PC were performed. P < 0·05 was considered significant. The mean saliva surface tension was 48·8 ± 8·0 mN m(-1) and PC concentration was 15·7 ± 11·1 nM. The surface tension was negatively correlated with the PC concentration (r = -0·48, P = 0·03). There was a significant positive correlation between surface tension with hypopnoea index (r = 0·50, P = 0·03) and HT/DBT (r = 0·6, P = 0·006), but not apnoea or apnoea/hypopnoea index (P > 0·11). Similarly, PC concentration negatively correlated with hypopnoea index (r = -0·45, P = 0·04) and HT/DBT (r = -0·6, P = 0·004), but not with apnoea index or AHI (P > 0·08). An increase in salivary PC concentration may increase upper airway patency in obstructive sleep apnoea through a reduction in surface tension.