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PubMed2002

Left ventricular hypertrophy and abnormal ventricular geometry in children and adolescents with obstructive sleep apnea.

Obstructive sleep apnea (OSA) has been shown to be an independent risk factor for cardiovascular disease in adults. However, there are severe limitations in the extent to which the cardiovascular consequences of OSA are being studied in children. To investigate the echocardiographic changes in children with OSA, right and left ventricular (RV, LV) dimensions and LV mass index and geometry were measured in 28 children with OSA and 19 children with primary snoring (PS). The study showed that LV mass index and relative wall thickness were greater in the OSA group compared with those with PS (p = 0.012 and p < 0.0001, respectively). An apnea-hypopnea index of more than 10 per hour was significantly associated with RV dimension above the 95th percentile (odds ratios, 6.7; 95% confidence interval, 1.4-32) and LV mass index above the 95th percentile (odds ratios, 11.2; confidence interval, 1.9-64). Abnormality of LV geometry was present in 15% of children with PS compared with 39% of children with OSA. We conclude that OSA in children is associated with increased LV mass.

Adolescent↗

PubMed1997

Obstructive sleep apnea as a cause of systemic hypertension. Evidence from a canine model.

Several epidemiological studies have identified obstructive sleep apnea (OSA) as a risk factor for systemic hypertension, but a direct etiologic link between the two disorders has not been established definitively. Furthermore, the specific physiological mechanisms underlying the association between OSA and systemic hypertension have not been identified. The purpose of this study was to systematically examine the effects of OSA on daytime and nighttime blood pressure (BP). We induced OSA in four dogs by intermittent airway occlusion during nocturnal sleep. Daytime and nighttime BP were measured before, during, and after a 1-3-mo long period of OSA. OSA resulted in acute transient increases in nighttime BP to a maximum of 13.0+/-2.0 mmHg (mean+/-SEM), and eventually produced sustained daytime hypertension to a maximum of 15.7+/-4.3 mmHg. In a subsequent protocol, recurrent arousal from sleep without airway occlusion did not result in daytime hypertension. The demonstration that OSA can lead to the development of sustained hypertension has considerable importance, given the high prevalence of both disorders in the population.

Animals↗

PubMed2000

Site of airway collapse in obstructive sleep apnea after uvulopalatopharyngoplasty.

The objective of this prospective study was to determine the site and pattern of upper airway collapse by a multiple-catheter technique in subjects demonstrated to have obstructive sleep apnea (OSA) after uvulopalatopharyngoplasty (UPPP). Standard diagnostic nocturnal polysomnography (PSG) was done on all subjects. The PSG recordings included electroencephalogram, electrooculogram, electrocardiogram, chin and leg electromyograms, nasal and oral airflow, and abdominal effort. Polysomnography with a multiport flexible airway Gaeltec catheter was performed in 22 subjects. The Gaeltec flexible airway catheter has 4 high-fidelity pressure sensors to aid in determining the primary site of airway collapse. The primary site of airway collapse was determined by differential pressure gradients between pressure ports and by visual inspection of the pressure tracings. Forty-two subjects with prior UPPP from a total of 60 (39 men and 3 women, ages 33 to 61) agreed to be to studied by the standard PSG technique. Thirty-five subjects complained of excessive daytime sleepiness. Ten had mild OSA, 10 had moderate OSA, 12 had severe OSA, and 10 were "normal." Of the 22 subjects who had airway catheter monitoring, 3 of the normals were reclassified as having upper airway resistance (mean peak negative esophageal pressure of -28 cm H2O); 2 patients demonstrated airway obstruction in the nasopharynx, 2 at the oropharynx, and 11 at the level of the hypopharynx. Postoperative nocturnal PSG data were compared to data gathered prior to UPPP. The mean respiratory disturbance index (RDI) for the catheter group was 54 events per hour prior to UPPP, and the mean RDI after surgery was 44. There was no correlation between the severity of OSA and the stage of sleep. We conclude that the majority of patients who complain of excessive daytime sleepiness following UPPP have OSA with the primary site of obstruction at the level of the hypopharynx. The severity of airway collapse is variable during each stage of sleep. Esophageal pressure monitoring during sleep should be considered when evaluating symptoms of persistent OSA in patients who have had UPPP.

Adult↗

PubMed2006

Does obstructive sleep apnea affect aerobic fitness?

OBJECTIVES: We sought to determine whether patients with obstructive sleep apnea (OSA) had an objective change in aerobic fitness during cycle ergometry compared to a normal population. The most accurate test of aerobic fitness is measurement of maximum oxygen consumption (VO2max) with cycle ergometry. METHODS: We performed a retrospective cohort analysis (247 patients with OSA) of VO2max from annual cycle ergometry tests compared to a large control group (normative data from 1.4 million US Air Force tests) in a tertiary care setting. RESULTS: Overall, individuals with OSA had increased VO2max when compared to the normalized US Air Force data (p < .001). Patients with an apnea-hypopnea index of greater than 20 demonstrated a decreased VO2max as compared to normalized values (p < .001). No differences in VO2max were observed after either medical or surgical therapy for OSA. CONCLUSIONS: Overall, in a US Air Force population, OSA does not predict a decrease in aerobic fitness as measured by cycle ergometry. However, patients with an apnea-hypopnea index of greater than 20 have a statistically significant decrease in aerobic fitness compared to the normal population. This study demonstrates the effects of OSA on aerobic fitness. Further correlation of fitness testing results with OSA severity and treatment is needed.

Adolescent↗

PubMed2001

Angiotensin converting enzyme in patients with sleep apnoea syndrome: plasma activity and gene polymorphisms.

The prevalence of several cardiovascular diseases is increased with obstructive sleep apnoea syndrome (OSAS), due to, as yet, unclear reasons. Angiotensin converting enzyme (ACE) abnormalities have been implicated in the pathogenesis of various cardiovascular diseases. In this study, plasma ACE activity and the distribution of an insertion (I)/deletion (D) polymorphism of the ACE gene were determined in OSAS patients and in healthy controls. A total of 63 patients with OSAS (mean+/-SEM 54.5+/-2.5 apnoea/hypopnoeas.h(-1)) and 32 healthy subjects were studied. To avoid potential confounding factors, patients treated with ACE inhibitors or continuous positive airway pressure were excluded, as well as controls in whom a blood sample was not obtained early in the morning. ACE activity was determined spectrophotometrically in 46 OSAS patients and 25 controls. The I/D ACE polymorphism was determined by polymerase chain reaction in 44 patients and 32 controls. ACE activity was higher in OSAS patients (53.9+/-2.5 IU.L(-1)) than in healthy controls (42.4+/-3.1 IU.L(-1), p<0.01). This was independent of the presence of arterial hypertension. The frequency distribution of the DD, II and ID genotypes in OSAS patients (30%, 16%, 54%, respectively) was not significantly different from that seen in healthy subjects (31%, 28%, 41%, respectively, p=0.356). These results indicate that ACE plasma activity is increased in untreated OSAS patients. This increased activity may contribute to the pathogenesis of the cardiovascular disease in these patients.

Cardiovascular Diseases↗

PubMed2005

Changes in extracranial arteries in obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) is linked with increased cardiovascular morbidity and mortality, possibly through an enhancement of atherosclerotic vascular changes. Up to now, however, only a few studies have tried to evaluate the occurrence of atherosclerosis in patients with OSA. In the present study, ultrasonography of the large extracranial vessels was performed in a group of consecutively admitted OSA patients (n = 35) and a control group of non-OSA patients (n = 35). Common carotid artery-intima media thickness (CCA-IMT) was measured at the far wall of both proximal carotid arteries. Furthermore, the presence of plaques and stenoses of the extracranial vessels was determined. All measurements were carried out blinded to the status of the patients. In the OSA group, CCA-IMT was significantly increased when compared with the non-OSA patients and was related to the degree of nocturnal hypoxia. Additionally, the formation of plaques was more pronounced and extracranial vessel stenosis was more common in the OSA patients. In conclusion, these findings are in favour of an independent influence of obstructive sleep apnoea on atherosclerotic changes of the arterial wall, and represent further strong arguments for obstructive sleep apnoea being a risk factor on its own for the emergence of cardiovascular disease.

Age Distribution↗

PubMed2005

Activated CD8+ T-lymphocytes in obstructive sleep apnoea.

T-lymphocytes are implicated in the development of atherosclerosis. The aim of this study was to assess whether the CD8+ T-lymphocytes of obstructive sleep apnoea (OSA) patients undergo phenotypic and functional changes that may exaggerate atherogenic sequelae in OSA. A total of 36 OSA patients, 17 controls and 15 single-night-treated OSA patients were studied. Phenotype and cytotoxicity against K562 target cells were analysed by flow cytometry. Cytotoxicity against human umbilical vein endothelial cells (HUVECs) was assessed by 51Cr release assay. The cytotoxicity of the CD8+ T-lymphocytes of OSA patients against K562 and HUVECs was significantly greater than controls. This increased cytotoxicity directly depended on the presence of perforin and natural killer receptors (CD56, CD16), which were significantly increased in OSA CD8+ T-lymphocytes. Also the percentage of the CD56bright subset, which mediates initial interactions with vascular endothelium, significantly increased in OSA. Nasal continuous positive airway pressure treatment significantly decreased CD8+ T-cell cytotoxicity and CD56 expression, and was positively correlated with natural killer inhibitory NKB1 receptor expression either after a single-night treatment or after a prolonged treatment. In conclusion, the CD8+ T-lymphocytes of obstructive sleep apnoea patients undergo phenotypic and functional changes, rendering them cytotoxic to target cells via increased CD56+/perforin+ expression, which can be ameliorated by nasal continuous positive airway pressure treatment. These results are compatible with the current authors' hypothesis of atherogenic sequelae in obstructive sleep apnoea.

Biomarkers↗

PubMed1998

Impact of nasal continuous positive airway pressure treatment on quality of life in patients with obstructive sleep apnoea.

Quality-of-life (QoL) issues have become increasingly important in health care practice and research. Obstructive sleep apnoea syndrome (OSAS) results in an especially serious reduction in QoL. The purpose of this study was to measure the QoL (life satisfaction) of OSAS patients treated with nasal continuous positive airway pressure (nCPAP). We aimed to determine whether and to what extent the QoL of OSAS patients using nCPAP differs from that of randomly selected subjects without this disorder. The QoL of 67 patients treated for at least 3 months with nCPAP, 21 OSAS patients at the time of OSAS diagnosis, and 113 randomly selected persons visiting the hospital (controls) was investigated with the help of the Munich life-quality dimension list (MLDL), an instrument for cognitive assessment of elementary components (physical condition, psyche, social life, everyday life) of QoL. It was found that QoL of OSAS patients treated with nCPAP did not significantly differ from that of control subjects with regard to elementary components. The 21 untreated OSAS patients showed significantly lower scores in all four subcategories: physical condition (p<0.0005), psyche (p<0.01), social life (p<0.0005) and everyday life (p<0.007). Thus, it may be concluded that nasal continuous positive airway pressure therapy has an important impact on the quality of life of obstructive sleep apnoea syndrome patients, and signifies a further advantage in addition to clinical aspects. Treated patients are as satisfied or dissatisfied with their life as persons without this illness.

Female↗

PubMed1999

Cephalometric abnormalities in non-obese and obese patients with obstructive sleep apnoea.

The aim of this work was to comprehensively evaluate the cephalometric features in Japanese patients with obstructive sleep apnoea (OSA) and to elucidate the relationship between cephalometric variables and severity of apnoea. Forty-eight cephalometric variables were measured in 37 healthy males and 114 male OSA patients, who were classed into 54 non-obese (body mass index (BMI) <27 kg x m(-2), apnoea-hypopnoea index (AHI)=25.3+/-16.1 events x h(-1)) and 60 obese (BMI > or = 27 kg x m(-2), AHI=45.6+/-28.0 events h(-1)) groups. Diagnostic polysomnography was carried out in all of the OSA patients and in 19 of the normal controls. The non-obese OSA patients showed several cephalometric defects compared with their BMI-matched normal controls: 1) decreased facial A-P distance at cranial base, maxilla and mandible levels and decreased bony pharynx width; 2) enlarged tongue and inferior shift of the tongue volume; 3) enlarged soft palate; 4) inferiorly positioned hyoid bone; and 5) decreased upper airway width at four different levels. More extensive and severe soft tissue abnormalities with a few defects in craniofacial bony structures were found in the obese OSA group. For the non-obese OSA group, the stepwise regression model on AHI was significant with two bony structure variables as determinants: anterior cranial base length (S-N) and mandibular length (Me-Go). Although the regression model retained only linear distance between anterior vertebra and hyoid bone (H-VL) as an explainable determinant for AHI in the obese OSA group, H-VL was significantly correlated with soft tissue measurements such as overall tongue area (Ton), inferior tongue area (Ton2) and pharyngeal airway length (PNS-V). In conclusion, Japanese obstructive sleep apnoea patients have a series of cephalometric abnormalities similar to those described in Caucasian patients, and that the aetiology of obstructive sleep apnoea in obese patients may be different from that in non-obese patients. In obese patients, upper airway soft tissue enlargement may play a more important role in the development of obstructive sleep apnoea, whereas in non-obese patients, bony structure discrepancies may be the dominant contributing factors for obstructive sleep apnoea.

Adult↗

PubMed2005

Searching for epistatic interactions in nuclear families using conditional linkage analysis.

BACKGROUND: Genomic screens generally employ a single-locus strategy for linkage analysis, but this may have low power in the presence of epistasis. Ordered subsets analysis (OSA) is a method for conditional linkage analysis using continuous covariates. METHODS: We used OSA to evaluate two-locus interactions in the simulated Genetic Analysis Workshop 14 dataset. We used all nuclear families ascertained by Aipotu, Karangar, and Danacaa. Using the single-nucleotide polymorphism map, multipoint affected-sibling-pair (ASP) linkage analysis was performed on all 100 replicates for each chromosome using SIBLINK. OSA was used to examine linkage on each chromosome using LOD scores at each 3-cM location on every other chromosome as covariates. Two methods were used to identify positive results: one searching across the entire covariate chromosome, the other conditioning on location of known disease loci. RESULTS: Single-locus linkage analysis revealed very high LOD scores for disease loci D1 through D4, with mean LOD scores over 100 replicates ranging from 4.0 to 7.8. Although OSA did not obscure this linkage evidence, it did not detect the simulated interactions between any of the locus pairs. We found inflated type I error rates using the first OSA method, highlighting the need to correct for multiple comparisons. Therefore, using "null chromosome pairs" without simulated disease loci, we calculated a corrected alpha-level. CONCLUSION: We were unable to detect two-locus interactions using OSA. This may have been due to lack of incorporation of phenotypic subgroups, or because linkage evidence as summarized by LOD scores performs poorly as an OSA covariate. We found inflated type I error rates, but were able to calculate a corrected alpha-level for future analyses employing this strategy to search for two-locus interactions.

Chromosome Mapping↗

PubMed2003

The diagnosis of obstructive sleep apnea as a risk factor for unanticipated admissions in outpatient surgery.

UNLABELLED: The goal of this study was to determine whether the preoperative diagnosis of obstructive sleep apnea (OSA) is an independent risk factor for perioperative complications in patients undergoing nonotorhinolaryngologic outpatient surgical procedures. We used existing databases to identify 234 patients with polysomnography-confirmed OSA who had outpatient surgical procedures in the years 1997 through 2000. Control patients were matched for type of anesthesia, age, sex, body mass index, surgical procedure, and surgical date. Their perioperative medical records were reviewed. There was no significant difference in the intraoperative management of OSA and control patients, except that the laryngeal mask airway was less likely to be used in OSA patients. There was no significant difference in the rate of unplanned hospital admissions (23.9% versus 18.8%; odds ratio, 1.4; 95% confidence interval, 0.8-2.5) or other adverse events (2.1% versus 1.3%; odds ratio, 1.7; 95% confidence interval, 0.4-7.0) between OSA and non-OSA patients. Further, when admission did occur, it was generally unrelated to cardiac or respiratory events. In this retrospective analysis, the preoperative diagnosis of OSA was not a risk factor for either unanticipated hospital admission or for other adverse events among patients undergoing outpatient surgical procedures in a tertiary referral center. IMPLICATIONS: In patients scheduled for outpatient surgery in a large academic practice, the diagnosis of obstructive sleep apnea confirmed by polysomnography was not an independent risk factor for unanticipated hospital admission or for other adverse perioperative events.

Adult↗

PubMed1991

Screening for sleep apnea using pulse oximetry and a clinical score.

Confirmation of the diagnosis of OSA currently requires overnight polysomnography. This study evaluates the usefulness of pulse oximetry together with a clinical score in identifying OSA. Forty patients were assigned a clinical score based on the presence or absence of loud snoring, observations of interrupted breathing during sleep, hypersomnolence, obesity and essential hypertension. Each underwent a night of domiciliary pulse oximetry followed by nocturnal polysomnography. Significant OSA was confirmed in 26. All 15 patients with positive pulse oximetry tracings had significant OSA (apnea index greater than or equal to 10). Five of eight with negative tracings were also shown to have significant OSA along with six of the seven patients with inadequate or indeterminate tracings. Clinical scores were significantly different for those with and without OSA. This study confirms the usefulness of nocturnal pulse oximetry in establishing the diagnosis of OSA and highlights the value of a clinical score in improving its sensitivity as a screening tool.

Adult↗

PubMed1992

Mechanisms of obstructive sleep apnea.

This article has reviewed the anatomic, compliance, reflex, and respiratory muscle variables that affect upper airway caliber and abnormalities which may precipitate upper airway collapse during sleep. One or more of these variables may be important in the mechanism of OSA in any given patient. First, anyone with anatomic narrowing of the upper airway is susceptible to OSA. However, we do know if anatomic narrowing of the upper airway is necessary for the development of OSA. Surely, heavy snoring produces pharyngeal trauma and possibly edema or inflammation, which in turn may narrow the upper airway. Submucosal adipose tissue or cervical adipose tissue may compress the airway when the tonic electrical activity of the pharyngeal muscles decreases with sleep onset. Data reviewed support the idea that the upper airway of OSA patients may be more collapsible than the upper airway of nonapneic subjects. Intrinsic tissue abnormalities have not been demonstrated that might be responsible for this collapsibility. Changes in collapsibility found are consistent with, and may be due to, changes in tonic and phasic contraction of upper airway muscles. Abnormalities in reflexes affecting upper airway size surely might exist in OSA. Edema or inflammation of pharyngeal tissues might not only narrow the upper airway but might also impair normal function of the receptors responsible for initiating protective reflexes. We propose the fluctuation between a low- and a high-drive state contributes to upper airway collapse in OSA. With this fluctuation the balance of forces and critical pressure concepts discussed above come into play (Fig 6). By stimulating upper airway inspiratory muscles, CO2 eliminates the hypoapneic, low-drive, high-resistance periods and thereby reduces the number of apneas. In addition, preferential stimulation of upper airway muscle activity dilates the upper airway per se. If the relative value of each of these factors can be determined diagnostically, perhaps therapy can be made more specific. By being more specific, therapy should be more successful than the present practice of prescribing a particular therapy, regardless of the specific mechanism responsible for the OSA in a given patient.

Humans↗

PubMed1995

Nasal continuous positive airway pressure in the perioperative management of patients with obstructive sleep apnea submitted to surgery.

Anesthetic, sedative, and analgesic drugs have been shown in animals and humans to selectively impair upper airway muscle activity. In patients with an already compromised upper airway, these drugs may further jeopardize upper airway patency, especially during sleep. Thus, patients with obstructive sleep apnea syndrome (OSAS) are at high risk for surgery because of the use of the aforementioned drugs in the perioperative period. It has been recommended that such drugs should be avoided or used with extreme caution in patients with OSAS submitted to surgery. We report herein on 16 adult patients with documented OSAS undergoing various types of surgical procedures, including coronary artery bypass surgery. Anesthesia was carried on with the usual type of drugs for each type of surgery. Postoperative opioid analgesia and sedation were not restricted. The first patient, whose OSAS was diagnosed but not treated, died after various complications, including a respiratory arrest in the ward. The second patient experienced serious postoperative complications until a treatment for OSAS with nasal continuous positive airway pressure (N-CPAP) was instituted, and thereafter he made an uneventful recovery. The 14 following patients were started on N-CPAP before surgery, were put on N-CPAP as soon as extubated, on a near-continuous basis, for 24 to 48 h and thereafter for all sleep periods. None of them had major complications. The intensive care unit and hospital stays were the normal ones for each type of surgery in our institution. We conclude that N-CPAP started before surgery and resumed immediately after extubation allowed us to safely manage a variety of surgical procedures in patients with OSAS, and to freely use sedative, analgesic, and anesthetic drugs without major complications. Every effort should be made to identify patients with OSAS and institute N-CPAP therapy before surgery.

Adult↗

PubMed1995

The relationship of sleepiness and blood pressure to respiratory variables in obstructive sleep apnea.

As a follow-up to a previous assessment of complications of sleep-disturbed breathing in 265 patients, we have reevaluated measures of sleepiness and hypertension in patients with obstructive sleep apnea (OSA) (n = 518), central sleep apnea (n = 50), and subclinical sleep-disordered breathing (SDB) (n = 107). Both subjective and objective (multiple sleep latency test [MSLT]) measures indicated that OSA patients were sleepier than those with subclinical SDB. The OSA patients weighed significantly more than the patients with central sleep apnea or subclinical SDB. They had a higher proportion of men, described more habitual sleepiness, and had a higher likelihood of feeling unrefreshed in the morning compared with the group with subclinical SDB. Among the OSA patients, there was a significant correlation between subjective and objective assessment of sleepiness, but this relationship was quantitatively very small. A forward stepwise regression analysis revealed that weight, and to a lesser degree waking time after sleep onset, could account for 65.5% of the variance in subjective sleepiness. Seventy-five percent of the variance of the mean sleep latency in the MSLT could be accounted for by the mean minimum arterial oxygen saturation in non-REM sleep and the nocturnal sleep latency. Diastolic BP was significantly higher in OSA patients compared with the patients with central sleep apnea and subclinical SDB. When covarying for weight, age, and gender, this effect lost significance. Among OSA patients taken by themselves, 98.3% of the variance in diastolic blood pressure could be accounted for by the mean minimum arterial oxygen saturation in non-REM sleep, with very small additional contributions of apnea/hypopnea index, weight, and age. In summary, among patients across a spectrum of SDB, differences in diastolic BP were primarily associated with weight, age, and gender. Among OSA patients, perhaps because of a more limited variance in weight, diastolic BP was associated with measures of SDB.

Adult↗

PubMed1996

Changes in cerebral oxygenation and hemodynamics during obstructive sleep apneas.

OBJECTIVE: To evaluate changes in cerebral tissue oxygenation and blood volume during obstructive sleep apnea (OSA). METHODS: We studied eight men with moderate to severe OSA by near-infrared spectroscopy (NIRS) simultaneously with polysomnography during nocturnal sleep (five patients) and daytime naps (three). RESULTS: In all patients, a consistent decrease of oxyhemoglobin (OxyHb) and increases of deoxyhemoglobin and total hemoglobin (TotalHb) in the regional cerebral tissue were observed during the episode of OSA at every sleep stage. Changes in each hemoglobin and apnea duration were significantly (p<0.01) more remarkable during rapid eye movement (REM) sleep than non-REM (NREM) sleep. Significant correlations of changes in OxyHb and TotalHb during the apneic episode with apnea duration were found during both NREM and REM sleep (p<0.01). CONCLUSIONS: Since TotalHb is used as an indicator of blood volume in the NIRS technique and the venous return is reported to increase during OSA, it is assumed that cerebral blood flow (CBF) increases during the episode of OSA. Because a decrease in OxyHb was observed and brain activity is reported to decrease during OSA, it is supposed that oxygen supply to the brain tissue decreases rather than oxygen consumption in the brain increases. The results of this study indicate that possibly increased CBF could not compensate for reduced arterial oxygen saturation and cerebral tissue hypoxia may occur during the episode of OSA.

Adult↗

PubMed1996

The single-breath diffusing capacity for carbon monoxide in obstructive sleep apnea and obesity.

BACKGROUND: We have observed high values of single-breath diffusing capacity for carbon monoxide (Dco) in patients with obstructive sleep apnea (OSA). STUDY OBJECTIVES: To confirm this observation and to determine the factors influencing diffusion indices in patients with OSA. As weight excess was found to be the major determinant of increased diffusion indices, the adequacy of various prediction equations was evaluate in obese subjects. DESIGN: Retrospective data collection. SETTING: University hospital. METHODS: DCO was measured in patients with OSA and in nonapneic subjects who served as control SUBJECTS: The results were expressed with respect to our own reference values and also to other prediction equations. RESULTS: In moderate/severe OSA (apnea/hypopnea index [AHI] > or = 30), both DCO and transfer coefficient (KCO) were increased and KCO was positively correlated with AHI and body mass index (BMI). Diffusion indices were not different between patients with moderate/severe OSA and nonapneic control subjects matched for age and BMI. In the latter group, KCO was also correlated with BMI. In our obese patients (BMI, 36.7 +/- 5.6 kg/m2), DCO was about 10% and KCO was 20 to 25% greater than predicted by standard reference equations. CONCLUSIONS: DCO and KCO are increased in a typical population of patients with moderate/severe OSA. This appears to be due to weight excess and not to OSA itself. In obese subjects, whether apneic or not, BMI is a determinant of diffusion indices that are higher than predicted by equations relying on age and stature alone.

Adult↗

PubMed1996

Posture-dependent change of tracheal sounds at standardized flows in patients with obstructive sleep apnea.

BACKGROUND: The ability of awake subjects with obstructive sleep apnea (OSA) to dilate their pharynx during inspiration may be defective. Airflow through a relatively more narrow pharyngeal passage should lead to increased flow turbulence and hence to louder respiratory sounds. We therefore studied the increase of tracheal sound intensity (TSI) in the supine position as an indicator of abnormal pharyngeal dynamics in patients with documented OSA. SUBJECTS AND METHODS: Sound was recorded with a contact sensor at the suprasternal notch in 7 patients with OSA (age, 52 +/- 8 years; body mass index, 29.0 +/- 3; apnea-hypopnea index, 58 +/- 17; means +/- SD), and in 8 control subjects, including obese subjects and snorers (age, 39 +/- 8 years; body mass index, 28.6 +/- 4). Subjects breathed through a pneumotachograph and aimed at target flows of 1.5 to 2 L/s, first sitting, then supine. Flow and sound signals were digitized at a 10-KHz rate. Fourier analysis was applied to sounds within the target flow range and average power spectra were obtained. Spectral power was calculated for frequency bands 0.2 to 1, 1 to 2, and 2 to 3 KHz. RESULTS: In the supine position, OSA patients had a significantly greater increase of inspiratory TSI than control subjects: 7.5 +/- 1.2 dB vs 1.7 +/- 3.4 dB (p < 0.001); 6.6 +/- 1.7 dB vs 1.3 +/- 3.9 dB (p < 0.005); and 12.2 +/- 3.2 dB vs 5.6 +/- 3.1 dB (p < 0.001) at low, medium, and high frequencies, respectively. Expiratory TSI also increased in supine subjects, but the change was significantly greater in OSA subjects only at high frequencies. These findings confirm our earlier observations that did not include obese subjects or snorers among control subjects. SUMMARY: Measuring posture effects on tracheal sounds is noninvasive and requires little time and effort. The greater increase of inspiratory TSI in supine OSA patients compared to subjects without OSA suggests a potential value for daytime acoustic screening.

Adult↗