Difference in upper airway collapsibility during wakefulness between men and women in response to lower-body positive pressure.

Fluid shift from the legs to the neck induced by LBPP (lower-body positive pressure) increases UA (upper airway) collapsibility in healthy men. Rostral fluid displacement during recumbency may therefore contribute to the pathogenesis of OSA (obstructive sleep apnoea). There is a higher prevalence of OSA in men than in women. We therefore hypothesized that UA collapsibility increases more in men in response to rostral fluid displacement than in women. UA collapsibility was assessed in healthy, non-obese men and women while awake by determining UA Pcrit (critical closing pressure) during application of different suction pressures to the UA. Subjects were randomized to 5 min control or LBPP arms after which they crossed-over into the other arm following a 30 min washout. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. Pcrit, leg fluid volume and neck circumference were measured at baseline and after 5 min of both control and LBPP periods. LBPP caused a decrease in leg fluid volume and an increase in neck circumference that did not differ between men and women. However, compared with the control period, LBPP induced a much greater increase in Pcrit in men than in women (7.2+/-1.8 compared with 2.0+/-1.5 cm H2O, P=0.035). We conclude that rostral fluid displacement by LBPP increases UA collapsibility more in healthy, non-obese men than in women. This may be one mechanism contributing to the higher prevalence of OSA in men than in women.

Lower body positive pressure increases upper airway collapsibility in healthy subjects.

We previously showed that rostral fluid displacement by lower body positive pressure (LBPP) narrows the upper airway (UA) and increases UA resistance, but effects on UA collapsibility remained unknown. To test if LBPP increases UA collapsibility, 13 healthy men were randomized into a control or LBPP arm then crossed over into the other arm with a 30-min washout in between. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. UA collapsibility was assessed by determining UA critical closing pressure (P crit) during application of different negative airway pressures. P crit and leg fluid volume were measured at baseline and after 5 min during both periods. LBPP caused a significant increase in P crit associated with a reduction in leg fluid volume. We conclude that rostral fluid displacement by LBPP increases UA collapsibility in healthy men, suggesting that fluid shift into the neck could increase UA collapsibility during sleep and thereby predispose patients with fluid overload states to obstructive sleep apnea.

Acoustic rhinometry in preschool children.

OBJECTIVE: The aim of this study was to measure nasal cavity volume (NV) in preschool children with the use of acoustic rhinometry (AR). STUDY DESIGN AND SETTING: Prospective study: 1) Nasal cavity models were used to test the correlations between NV, minimal cross-sectional area (MCA), and nasal resistance; 2) 97 four-year-olds (48 boys, 49 girls) and 137 five-year-olds (68 boys, 69 girls) children were selected to undergo AR. RESULTS: 1. Model tests showed that the resistance correlated better with the changes of the volume than the MCA. 2. The average bilateral NV in preschool children was 2.03 +/- 0.4 mL. There was no significant difference in either gender (P = 0.2) or age (P = 0.197). CONCLUSIONS: Volume measurement appears more sensitive and reliable than the MCA in assessing nasal patency. AR was easily performed on preschool children, and normative NV values were achieved. SIGNIFICANCE: The results and conclusions can be used to establish a standardized technique for AR measurement and interpretation.

Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine, and pulmonary nitric oxide: a randomized, controlled, crossover trial.

BACKGROUND: Although recent studies have indicated that nut consumption may improve levels of blood lipids, nuts are not generally recommended as snacks for hyperlipidemic subjects because of their high fat content. Furthermore, the effective dose is still unknown. METHODS AND RESULTS: The dose-response effects of whole almonds, taken as snacks, were compared with low-saturated fat (<5% energy) whole-wheat muffins (control) in the therapeutic diets of hyperlipidemic subjects. In a randomized crossover study, 27 hyperlipidemic men and women consumed 3 isoenergetic (mean 423 kcal/d) supplements each for 1 month. Supplements provided 22.2% of energy and consisted of full-dose almonds (73+/-3 g/d), half-dose almonds plus half-dose muffins, and full-dose muffins. Fasting blood, expired air, blood pressure, and body weight measurements were obtained at weeks 0, 2, and 4. Mean body weights differed <300 g between treatments. The full-dose almonds produced the greatest reduction in levels of blood lipids. Significant reductions from baseline were seen on both half- and full-dose almonds for LDL cholesterol (4.4+/-1.7%, P=0.018, and 9.4+/-1.9%, P<0.001, respectively) and LDL:HDL cholesterol (7.8+/-2.2%, P=0.001, and 12.0+/-2.1%, P<0.001, respectively) and on full-dose almonds alone for lipoprotein(a) (7.8+/-3.5%, P=0.034) and oxidized LDL concentrations (14.0+/-3.8%, P<0.001), with no significant reductions on the control diet. No difference was seen in pulmonary nitric oxide between treatments. CONCLUSIONS: Almonds used as snacks in the diets of hyperlipidemic subjects significantly reduce coronary heart disease risk factors, probably in part because of the nonfat (protein and fiber) and monounsaturated fatty acid components of the nut.

Nasal nitric oxide in children: a novel measurement technique and normal values.

OBJECTIVES: To develop and standardize a technique for measuring nasal nitric oxide (NO) output in children and to determine normal values in this population. STUDY DESIGN: Prospective study evaluating a new technique for measuring nasal nitric oxide in a cohort of normal patients and a cohort of patients with nasal disease. METHODS: Nasal NO was measured using an aspiration technique, aspirating room air through the nasal cavities by means of a Teflon nozzle placed in one nasal vestibule while maintaining velopharyngeal closure using a party "blow-out" toyRESULTS Nasal NO measurements were performed in 45 children (mean age, 11.0 y; age range, 3.2-17.6 y) There were 20 girls and 25 boys. All children were able to perform the maneuvers necessary for measurement of nasal NO output. Among the subgroup of normal healthy children (30), there was considerable variation in NO output between subjects, with a mean NO output of 481 nL/min and an SD of 283 nL/min. CONCLUSIONS: Nasal NO can be readily measured in children using the presented technique. There is considerable variability in the values for nasal NO output in normal children.

Sleep apnea in patients with oral cavity and oropharyngeal cancer after surgery and chemoradiation therapy.

OBJECTIVE: To determine the point prevalence of sleep apnea in patients following oral and oropharyngeal cancer treatment at a major tertiary care referral center. STUDY DESIGN: A retrospective cross-sectional survey. SUBJECTS AND METHODS: Twenty-four patients with established oral or oropharyngeal cancer were submitted to overnight polysomnography. The surgical group consisted of 15 patients (11 male, 4 female; average age 64.2 yrs) having undergone primary surgery with radial forearm free flap reconstruction. The remaining patients (5 male, 4 female; average age 54.8 yrs) were treated nonsurgically with chemoradiation therapy. The fatigue-related daytime sleepiness was measured with the Epworth sleepiness scale (ESS). RESULTS: Eleven patients in the surgical group and three in the nonsurgical group had a respiratory disturbance index (RDI) greater than 15 (odds ratio = 5.5, P = 0.092). Twelve patients in the surgical group and five in the nonsurgical group had significant oxygen desaturation during sleep hours (odds ratio = 3.3, P = 0.356). There was no observed significant correlation between RDI and oxygen desaturation (r(2) = 0.28), nor was there any observed association between the RDI and ESS score (r(2) = 0.18). CONCLUSION: This preliminary study has suggested that surgical patients in our cohort have a higher prevalence of moderate to severe obstructive sleep apnea in the postoperative period, when tested, compared with a nonsurgical group. A small sample size and incomplete matching on important cofactors of interest, such as primary site location, body mass index, and thyroid function, limit this study. A pretreatment and post-treatment analysis is obviously required to demonstrate any significant level of association between treatment type and sleep apnea status.

Alterations in upper airway cross-sectional area in response to lower body positive pressure in healthy subjects.

BACKGROUND: Fluid accumulation in the neck during recumbency might narrow the upper airway (UA) and thereby contribute to its collapse in patients with obstructive sleep apnoea (OSA). It is hypothesised that acute fluid shifts from the legs to the upper body in healthy subjects would increase neck circumference and reduce the cross-sectional area of the UA (UA-XSA). METHODS: In 27 healthy non-obese subjects of mean (SE) age 39 (3) years and body mass index 23.2 (0.6) kg/m2 studied while supine, leg fluid volume was measured using bioelectrical impedance, neck circumference using a mercury strain gauge and mean UA-XSA between the velum and the glottis using acoustic pharyngometry at end expiration. Measurements were made at baseline after which subjects were randomly assigned to a 5 min time control period or to a 5 min application of lower body positive pressure (LBPP) at 40 mm Hg by anti-shock trousers, separated by a 15 min washout period. Subjects then crossed over to the opposite arm of the study. RESULTS: Compared with control, application of LBPP significantly reduced leg fluid volume (p<0.001) and increased neck circumference (p<0.001), both at 1 min and 5 min, and reduced UA-XSA after both 1 min (-0.15 cm2; 95% CI -0.23 to -0.09, p<0.001) and 5 min (-0.20 cm2; 95% CI -0.33 to -0.09, p<0.001). CONCLUSION: In healthy subjects, displacement of fluid from the legs by LBPP causes distension of the neck and narrowing of the UA lumen. Fluid displacement from the lower to the upper body while recumbent may contribute to pharyngeal narrowing and obstruction to airflow in patients with OSA. This may have particular pathological significance in oedematous states such as heart and renal failure.

Fluid shift by lower body positive pressure increases pharyngeal resistance in healthy subjects.

INTRODUCTION: Fluid displacement into nuchal and peripharyngeal soft tissues while recumbent may contribute to narrowing and increased airflow resistance of the pharynx (Rph), and predispose to pharyngeal collapse in patients at risk for obstructive sleep apnea. OBJECTIVES: To determine whether displacement of fluid from the lower body to the neck will increase both neck circumference and Rph in healthy subjects. METHODS: In 11 healthy, nonobese subjects, studied while awake and supine, leg fluid volume, neck circumference, and Rph were measured at baseline. Subjects were then randomized to a control period or to application of lower body positive pressure (LBPP) of 40 mm Hg via antishock trousers to displace fluid from the legs, after which they crossed over to the other arm. Baseline measurements were repeated at 1 and 5 min during the control and LBPP periods. RESULTS: Compared with the control period, application of LBPP caused a significant reduction in leg fluid volume (p < 0.001) and a significant increase in neck circumference (p = 0.004). Rph remained stable during the control period, but increased significantly from baseline after 1 and 5 min of LBPP (from 0.43 +/- 0.10 to 0.60 +/- 0.11 cm H(2)O/L/s, p = 0.034, and to 0.87 +/- 0.19 cm H(2)O/L/s, p < 0.001, compared with baseline, respectively). CONCLUSIONS: Fluid displacement from the legs by LBPP increases neck circumference and Rph in healthy subjects. These findings suggest the hypothesis that fluid displacement to the upper body during recumbency may predispose to pharyngeal obstruction during sleep, especially in fluid overload states, such as heart and renal failure.

Nitric oxide (NO) and obstructive sleep apnea (OSA).

Nitric oxide (NO) and obstructive sleep apnea are inseparable. Obstructive sleep apnea could be described as the intermittent failure to transport the full complement of nasal NO to the lung with each breath. There NO matches perfusion to ventilation. NO is utilized by the efferent pathways that control the unequal, inspiratory battle between the pharyngeal dilators and the closing negative pressures induced by the thoracic musculature. Recurrent cortical arousals are a major short-term complication, and the return to sleep after each arousal uses NO. The long-term complications, namely hypertension, myocardial infarction, and stroke, might be due to the repeated temporary dearth of NO in the tissues, secondary to a lack of oxygen, one of NO's two essential substrates.