Influence of apnea type and sleep stage on nocturnal postapneic desaturation

We examined the influence of apnea type and sleep stage on the severity of apnea-induced desaturations in 32 patients with a sleep apnea syndrome. The individual postapneic desaturations were evaluated by a desaturation curve; this curve was built by plotting the fall in SaO2 after an apnea against this apnea's length for each apneic event during the whole night recording. We considered only apneas where the preapneic SaO2 was greater than 90% and the lowest SaO2 value after the apnea was equal to or greater than 60% (limit of linearity of our oximeter). From the desaturation curve, we determined a desaturation surface defined as the area under the curve between 10s and a variable apnea duration. The upper bound used for the determination of the desaturation curve and the desaturation surface was the maximal length of apnea type with the shortest apnea duration between non-REM obstructive apnea and the other apnea types (i.e., obstructive and central apnea, obstructive and mixed apnea, etc.). The desaturation surface was determined separately for non-REM sleep apneas (obstructive apneas, mixed apneas, central apneas, and obstructive apneas with persistent expiratory flow) and REM sleep apnea (all obstructive in type). Non-REM obstructive apneas served as reference to evaluate the severity of apnea-induced desaturations of the other apneas. We found that the desaturation surface of obstructive apnea (OA) with expiratory flow and of REM sleep OA were significantly greater than for OA in non-REM sleep (p less than or equal to 0.005). The OA-related desaturation was significantly greater than those of central apneas (p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of automatic analysis of SCSB, airflow and oxygen saturation signals in patients with sleep related apneas

We have developed a computerized analysis of respiratory and body movements (static charge sensitive bed [SCSB]), oxygen saturation (pulse oximeter), and airflow (thermistor) for the evaluation of sleep related apneas. The cumulative distribution of oxygen saturation, the number and distribution of desaturation events, and the duration and type of apneas are assessed. Analysis is performed separately during the total recording time and during the time when the patient sleeps on his back. We have compared the automatic analysis with the results obtained on simultaneous daytime polysomnograph naps in 55 subjects (snorers or obstructive sleep apnea syndrome [OSAS] patients). The compressed graphs obtained automatically demonstrated a periodic breathing pattern in all 22 patients who presented sleep-related apneas at polygraphic recording. The cumulative distribution of oxygen saturation was not as steep in the apnea patients as in patients not showing apneas; in 19 of the 22 OSAS patients, the value was outside our normal limits (80 percent of the recording time inside 3.6 percent SaO2 variation band). The apnea index (AI) was 26.4 in manual and 23.3 in automatic analysis. Using the automatic method there were three false negative cases in the analysis of desaturations; in these patients periodic breathing was present in output graphs indicating need for further polygraphic assessment. The duration of apneas in the automatic analysis was shorter than in manual analysis, but the agreement was sufficient for screening purposes (mean error less than 3 s, mean duration of apneas 20.1 s). The automatic method is presently used in clinical routine for screening purposes, for assessment of the severity of the disorder and the type of treatment that a subject may need, in epidemiologic investigation and follow-up of the treatment.     

Computerized detection of respiratory events during sleep from rapid increases in oxyhemoglobin saturation.

A computerized search for rapid resaturation (RES)--defined as increases in oxyhemoglobin saturation (SaO2) of 3% or more within 10 s--was used to detect apneas and hypopneas during sleep by the episodes of compensatory hyperventilation following them. Results were compared to those from computerized search for desaturations (DESAT)--defined as decreases in SaO2 of 4% or more within 40 s--and to simultaneous polysomnography. We studied 30 patients with obstructive sleep apnea (OSA) with an apnea plus hypopnea index (AHI) of 30.8 +/- 6.9 (median +/- SEM) and 23 habitual snorers (HSN) with an AHI of 7 +/- 1.5. Manual scoring of polysomnography revealed 7965 respiratory events (6192 apneas, 1773 hypopneas) in OSA patients and 940 events (411 apneas, 529 hypopneas) in the HSN group. In OSA patients, the computer found 96% of events by searching for RES and 87% by searching for DESAT. The percentage of computer-found events in OSA classified as true positive was 91% for RES and 97% for DESAT. In the HSN group, 83% of polysomnographically scored events were found by RES and 55% by DESAT, with 72% of RES and 84% of DESAT being true positive. The correlation of the number of computer-found RES with the number of events from polysomnography was better in OSA (r = 0.862, p less than 0.0001) than in HSN (r = 0.722, p less than 0.001). The same was true for DESAT (OSA: r = 0.896, p less than 0.0001; HSN: r = 0.637, p less than 0.01). In conclusion, computer-found rapid resaturations are more sensitive than desaturations for the detection of respiratory events during sleep from oximetry.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contribution of nocturnal polygraphy to the diagnosis of Pickwickian syndrome. 10 cases

The authors studied a series of 10 obese patients with respiratory failure referred for treatment because of sleep disorders and diurnal, sometimes uncontrollable, episodes of somnolence. 8 parameters were recorded in the polygraphic study performed during a night of hospitalization: electroencephalogram, electrocardiogram, electro-oculogram, chin electromyogram, thoracic movements, and nasal and buccal air flows. SaO2 and transcutaneous PO2 were recorded simultaneously. A sleep apnea syndrome was diagnosed in 6 of the 10 patients, whose apnea index was markedly above the limit of 5 apneas per hour. The apnea index was below 5 in the other 4 patients. Most patients with sleep apnea syndrome suffer from obstructive apneas of varying duration taking up as much as 48% of total sleep time. The cardiorespiratory effects of these events are apparent, with a drop in PO2 and SaO2 and a decrease in heart rate at the end of apnea. Polygraphic studies seem useful in the diagnosis of the pickwickian syndrome. They allow the type of apnea and its effects to be specified and thus guide treatment.     

Rate of oxyhemoglobin desaturation in obstructive versus nonobstructive apnea

Preapneic thoracic gas volume (Vtg), arterial saturation (SaO2), and mixed venous oxygen saturation (SvO2), have been shown to influence the rate of SaO2 fall (dSaO2/dt) during apnea. We asked the following question: does tissue oxygen consumption (tVO2) affect the dSaO2/dt during apnea? We attempted to answer this question by comparing dSaO2/dt during obstructive apneas (high tVO2) with dSaO2/dt during nonobstructive apneas (low tVO2) in six adult baboons. Fiberoptic central venous and arterial catheters were used for continuous monitoring of SvO2, SaO2, and cardiac output. A sapphire-bearing turbine monitored minute ventilation and airflow cessation. A Respitrace and esophageal pressures were used to assess relative differences in Vtg. Obstructive apneas (30, 45, and 60-s) were created by clamping an indwelling cuffed endotracheal tube at end-expiration. Nonobstructive apneas were created by paralyzing the animals with atracurium and interrupting ventilation for periods equivalent to those of the obstructed apneas. The ventilator was adjusted to duplicate the respiratory rate, tidal volume, and relative Vtg of the spontaneously breathing animal. Mean tVO2 during spontaneous breathing was 110 ml/min (Fick method) and decreased to 90 ml/min during paralysis (p less than 0.05). The dSaO2/dt for the three apnea durations (mean, all animals), obstructive versus nonobstructed were: 0.85 and 0.74%/s (n = 6), 0.87 and 0.75%/s (n = 6), and 0.60 and 0.48%/s (n = 4), respectively. The dSaO2/dt was significantly lower during the nonobstructive apneas. We conclude that differences in VO2 during apnea may affect the dSaO2/dt and that for the same duration apnea, central apneas may show less desaturation than obstructive apneas where vigorous muscular efforts at overcoming obstruction are common.     

Transtracheal oxygen, nasal CPAP and nasal oxygen in five patients with obstructive sleep apnea.

The effect of transtracheal oxygen administration by means of a 9-French (2.7 mm) percutaneous catheter was assessed in five patients with severe obstructive sleep apnea. We hypothesized that the delivery of oxygen below the site of airway obstruction should reduce the arterial oxygen desaturation during apneas and hypopneas, thereby increasing respiratory stability. Standard sleep and respiratory measurements were recorded in these subjects with all-night polysomnography on nonconsecutive nights during four experimental conditions: room air (BL), nasal continuous positive airway pressure (CPAP), nasal O2 (NC O2), and transtracheal O2 (TT O2). In three of these subjects, room air was infused (TT RA) at flow rates comparable to TT O2. Compared with baseline room air measurements, TT O2 not only significantly increased the SaO2 nadir from 70.4 percent to 89.7 percent (p less than 0.01), but it also reduced the frequency of sleep apnea/hypopnea from 64.6 to 26.2/h sleep (p less than 0.01). NC O2 ameliorated desaturation during apnea/hypopnea (mean SaO2 nadir, 86.2 percent; p less than .01) but did not significantly alter frequency (59.0/h sleep). Nasal CPAP was the most effective means of reducing sleep apnea/hypopnea (13.8/h sleep) but did not abolish desaturations when apneas occurred (mean SaO2 nadir, 80.0 percent). Compared with oxygen, transtracheal infusion of room air appeared to be somewhat effective; however, the small number of studies with TT RA precluded statistical analysis. We believe that TT O2 is superior to NC O2 for some patients with obstructive sleep apnea because continuous oxygen flow below the site of airway obstruction more reliably prevents alveolar hypoxia and respiration is stabilized. Infusion of air or oxygen through the tracheal catheter flow may also increase mean airway pressure and reduce obstructive apnea similar to nasal CPAP. We conclude that TT O2 may be an effective alternative mode of therapy for some patients with severe sleep apnea/hypopnea when nasal CPAP is not tolerated or when combined oxygen and nasal CPAP are required.     

Oxygen saturation during breath-holding and during apneas in sleep

The rate of fall in oxygen saturation is said to be greater during obstructive apneas than during breath-holding in wakefulness. Using an ear oximeter, a face mask and flowmeter, and measurements of thoracoabdominal motion, we determined in six healthy subjects the rate of fall in arterial oxygen saturation (SaO2) during breath-holding which simulated obstructive and nonobstructive apneas. Breath-holding maneuvers were performed during progressive isocapnic hypoxia and were initiated at the same end-expiratory thoracoabdominal configuration. We found that at any given initial SaO2 the rate of fall in SaO2 was similar during simulated obstructive (y = 5.5-0.06 x; r = 0.83) and nonobstructive (y = 6.8-0.07 x; r = 0.92) apneas. In two healthy subjects and 13 patients with obstructive and nonobstructive apneas during sleep, the rate of fall in SaO2 at any initial SaO2 was similar to that found in healthy subjects during breath-holding in wakefulness. We conclude that during wakefulness the presence or absence of respiratory efforts does not affect the rate of fall in SaO2 during breath-holding and that the rate of fall of SaO2 during sleep apnea is largely dependent on the initial SaO2 at the onset of apnea.     

Comparison of indices used to detect hypoventilation during sleep

Because there is no uniform method of measuring the severity of sleep apnea, we compared respiratory indices calculated from airflow and oxyhemoglobin saturation (SaO2) signals in 16 subjects during a night's sleep. Airflow was measured with a loosely fitting pneumotachograph or thermister and the following indices calculated manually: total apneas (A) and hypopneas (H); A and H per hour of sleep; total A H time; average duration of A H episodes, and A H index (the product of 2 and 4). SaO2 was measured with a Hewlett-Packard ear oximeter and the following indices calculated with a microcomputer; total number of desaturation (D) episodes; D episodes per hour of sleep; average maximum D; D index (the product of 7 and 8); SaO2 50 (1), and SaO2 10(1). There was a significant correlation among all indices; the highest correlation was between total A and H and total D (r = 0.97). We conclude that SaO2 indices calculated with a microcomputer correlate well with flow indices.     

经皮电刺激对阻塞性睡眠呼吸暂停的影响

目的研究经皮颏下电刺激对睡眠期阻塞性睡眠呼吸暂停综合征的影响。方法１６例阻塞性睡眠呼吸暂停患者在接受经皮颏下电刺激（ＴＥＳ）治疗前后进行了全夜多导睡眠图监测。结果１６例中的１４例ＴＥＳ治疗成功，睡眠呼吸暂停指数（ＡＩ）下降＞５０％，平均ＡＩ下降了２９次／小时（Ｐ＜０．００１），平均呼吸暂停时间从２２秒降至７秒（Ｐ＜０．００１）呼吸暂停时间／总睡眠时间（ＴＳＴ）下降了２０％。最低血氧饱和度从７１％升至８７％（Ｐ＜０．００１）。ＴＥＳ未引起觉醒。慢波睡眠（Ⅲ＋Ⅳ）期，快动眼期（ＲＥＭ）睡眠及睡眠效率增加。结论ＴＥＳ是一种非手术的、有效的治疗阻塞性睡眠呼吸暂停综合征的方法，但对中枢性睡眠呼吸暂停无效     

External quality assurance for the laboratory diagnosis of Buruli ulcer disease in Ghana

OBJECTIVE: To assure the quality of the laboratory diagnosis of Buruli ulcer disease; microscopy and PCR were subjected to external quality assurance (EQA). METHODS: Slides were read by test laboratory staff, followed by blinded re-reading by the controller. Parallel testing of PCR specimens was carried out at the local and external reference laboratory. Slides and PCR specimens with discordant results were subjected to a second reading/testing by the controller to determine the final result. For training purposes, slides and PCR specimens with discrepant results were subsequently re-read/re-tested under supervision at the test laboratory. RESULTS: Microscopy. First reading: concordance rate 82.9%, discordance rate 17.1%, percentage false negatives 27.1% (sensitivity 72.9%), percentage false positives 10.1% (specificity 89.9%). Second reading: concordance rate 97.9%, discordance rate 2.1%, percentage false negatives 4.2% (sensitivity 95.8%), percentage false positives 0.6% (specificity 99.4%). PCR. First testing: concordance rate 87.9%, discordance rate 12.1%, percentage false negatives 8.2% (sensitivity 91.8%), percentage false positives 19.1% (specificity 80.9%). Second testing: concordance rate 96.2%, discordance rate 3.8%, percentage false negatives 4.7% (sensitivity 95.3%), percentage false-positives 2.1% (specificity 97.9%). CONCLUSIONS: EQA identified deficiencies in the laboratory performance. Corrective action consisted in on-site training and reduced the number of false-negative and false-positive microscopy and PCR results.     

Mandibular advancement devices in 630 men and women with obstructive sleep apnea and snoring: tolerability and predictors of treatment success

STUDY OBJECTIVE: To evaluate the tolerability and to find predictors of treatment success for an individually adjusted, one-piece mandibular advancement device in patients with snoring and obstructive sleep apnea. DESIGN: Prospective study. SETTING: Departments of Respiratory Medicine and Orthodontics, Ume? University. PATIENTS: Six hundred nineteen of 630 patients (98%), who consecutively received treatment for sleep apnea and snoring from February 1989 to August 2000, were followed up. They had a mean apnea-hypopnea index of 16 (range, 0.0 to 76) and a mean body mass index of 28 (range, 19 to 42). MEASUREMENTS: Interviews, questionnaires, and overnight sleep apnea recordings. Patients with an apnea-hypopnea index of >or=10 in the supine and/or lateral position were considered to have obstructive sleep apnea. A lateral apnea-hypopnea index of < 10, together with a supine apnea-hypopnea index of >or= 10, defined supine-dependent sleep apneas. RESULTS: One hundred forty-eight of the 619 patients (24%) discontinued treatment. Female gender predicted treatment success, defined as an apnea-hypopnea index of < 10 in both the supine and lateral positions, with an odds ratio of 2.4 (p = 0.01). In the women, the odds ratios for treatment success were 12 for mild sleep apnea (p = 0.04), and 0.1 for complaints of nasal obstruction (p = 0.03). In the men, the odds ratios for treatment success were 6.0 for supine-dependent sleep apneas (p < 0.001), 2.5 for mild sleep apnea (p = 0.04), 1.3 for each millimeter of mandibular advancement (p = 0.03), and 0.8 for each kilogram of weight increase (p = 0.001). CONCLUSIONS: The mandibular advancement device is recommended for women with sleep apnea, for men with supine-dependent sleep apneas defined by a lateral apnea-hypopnea index of < 10, and for snorers without sleep apnea. Men who increase in weight during treatment reduce their chance of treatment success and are advised to be followed up with a new sleep apnea recording with the device.     

An evaluation of leucocyte analysis on the Coulter STKS.

The performance of leucocyte analysis on the Coulter STKS (Coulter, Hialeah, FL, USA) was evaluated for accuracy, precision and reliability. The results were compared with those obtained from visual examination of a Romanowsky stained blood film together with the automated WBC-diff. from the Technicon H*1 (Technicon, Tarrytown, NY, USA). The relationship between the number of cells counted per WBC-diff. and the WBC count of the sample was established. Precision of the STKS WBC-diff. was acceptable on blood samples with normal and low WBC counts. Correlation with an 800 cell manual WBC-diff. (n = 104) was excellent (r = 0.97, 0.97, 0.83, 0.98 and 0.53 for neutrophils, lymphocytes, monocytes, eosinophils and basophils respectively). Blood specimens, collected into dipotassium EDTA, could be stored at 20-25 degrees C for at least 8 h with no significant effect on the STKS WBC-diff. In a study of 513 patient samples, the BLASTS suspect flag gave 5.4% false positives and zero false negatives, the VARIANT LYMPHS flag gave 1.5% false positives and 0.4% false negatives, and the IMM GRANS/BANDS flag gave 30.8% false positives and 2.3% false negatives. Several instrument and sample related problems were encountered during this study. Despite these limitations, the STKS can provide efficient 5 part WBC-diffs. and effective screening for WBC abnormalities.     

History of Chronic Alcohol Abuse Is Associated with Increased Nighttime Hypoxemia in Older Men

The all-night blood oxygen saturations (SaO2) of 19 older abstaining male alcoholics and 19 healthy age-matched controls were recorded. The alcohol group had significantly lower nighttime mean and minimum oxygen saturations, significantly greater absolute (mean-minimum) SaO2 desaturations, and significantly more desaturations below 90% compared with the control group. Additionally, the alcohol group had significantly more individuals with nighttime SaO2 means below 95% and nighttime SaO2 minimums below 90%. Finally, within the alcohol group, alcohol history was found to significantly correlate with nighttime mean and minimum SaO2 and absolute SaO2 desaturation. This preliminary study finds evidence that chronic alcohol abuse may predispose an individual to nighttime hypoxemia, and, inferentially, to sleep apnea. However, the effect is modest and it will need to be confirmed in larger, more carefully controlled studies.     

An evaluation of leucocyte analysis on the Coulter STKS

Summary The performance of leucocyte analysis on the Coulter STKS (Coulter, Hialeah, FL, USA) was evaluated for accuracy, precision and reliability. The results were compared with those obtained from visual examination of a Romanowsky stained blood film together with the automated WBC-diff. from the Technicon H*1 (Technicon, Tarrytown, NY, USA). The relationship between the number of cells counted per WBC-diff. and the WBC count of the sample was established. Precision of the STKS WBC-diff. was acceptable on blood samples with normal and low WBC counts. Correlation with an 800 cell manual WBC-diff. (n = 104) was excellent (r = 0.97, 0.97, 0.83, 0.98 and 0.53 for neutrophils, lymphocytes, monocytes, eosinophils and basophils respectively). Blood specimens, collected into dipotassium EDTA, could be stored at 20–25°C for at least 8 h with no significant effect on the STKS WBC-diff. In a study of 513 patient samples, the BLASTS suspect flag gave 5.4% false positives and zero false negatives, the VARIANT LYMPHS flag gave 1.5% false positives and 0.4% false negatives, and the IMM GRANS/BANDS flag gave 30.8% false positives and 2.3% false negatives. Several instrument and sample related problems were encountered during this study. Despite these limitations, the STKS can provide efficient 5 part WBC-diffs. and effective screening for WBC abnormalities.     

Acidification of distal esophagus and sleep-related breathing disturbances

STUDY OBJECTIVES: To investigate whether distal esophageal acidification occurs during sleep in patients suspected of sleep-disordered breathing, and whether such acidification is related to respiratory abnormalities. DESIGN AND PATIENTS: Fourteen middle-aged, snoring men all complaining of daytime sleepiness and suspected of having obstructive sleep apnea. SETTING: Sleep laboratory, Pulmonary Department, Landspitali University Hospital, Reykjavik, Iceland. MEASUREMENTS AND RESULTS: Each patient underwent full nocturnal polysomnography testing, which included continuous monitoring of esophageal pressure (Pes) and pH. We identified all pH events, which were defined as a reduction in esophageal pH of >/= 1.0. During each pH event, the respiratory recordings where examined for the presence of apneas or hypopneas, and Pes was recorded. The data were analyzed to determine the possible relationships between pH events and respiratory events, and between changes in pH and changes in Pes. We found that there were more respiratory events than pH events. The mean (+/- SD) number of apneas and hypopneas per hour of sleep was 33 +/- 22, whereas the mean number of pH events per hour of sleep was 7 +/- 6. Overall, 81% of all pH events were associated with respiratory events. Correlation analysis did not reveal any significant relationship between pH events and the magnitude of Pes or apnea-hypopnea index. CONCLUSIONS: Episodes of esophageal acidification are common in patients with sleep apnea, and are usually associated with respiratory and pressure events. However, changes in pH were independent of the magnitude of the Pes.     

Timing of nocturnal ventricular ectopy in heart failure patients with sleep apnea

BACKGROUND: Ventricular ectopy is frequent in heart failure (HF) patients with sleep apnea. A previous report indicated that in HF patients, ventricular premature beats (VPB) occurred more frequently during episodes of recurrent central sleep apnea (CSA) than during normal breathing, and their frequency was greater during hyperpnea than during apnea. We hypothesized that, because respiratory stimuli that might provoke ventricular ectopy are stronger during obstructive apneas than during central apneas, in contrast to CSA, VPBs would be more frequent during apnea than hyperpnea in HF patients with obstructive sleep apnea (OSA). METHODS: HF patients in sinus rhythm who have OSA or CSA (apnea-hypopnea index, > or = 15 events per hour) and with > 30 VPBs per hour were matched for severity of cardiac dysfunction and sleep apnea. The frequency of VPBs was then assessed during stage 2 sleep during the apneic and the hyperpneic phases of recurrent obstructive or central apneas. RESULTS: VPBs occurred more frequently during the apneic phase than during the hyperpneic phase in patients with OSA. In contrast, VPBs occurred more frequently during the hyperpneic phase than the apneic phase in patients with CSA. There was no difference in the degree of apnea-related oxygen desaturation between central and obstructive apneas. CONCLUSIONS: In patients with HF, nocturnal ventricular ectopy oscillates in time with oscillations in ventilation, with VPBs occurring predominantly during apneas in patients with OSA, but during hyperpneas in patients with CSA. This difference in VPB timing between OSA and CSA may be attributable to the differences in timing of arrhythmic stresses in these patients.     

Does oximetry contribute to the detection of apneic events? Mathematical processing of the SaO2 signal

The purpose of this study was to assess the ability of continuous nocturnal oximetry to detect sleep apnea syndrome (SAS) and to recognize nonapneic oxyhemoglobin desaturations. Oxygen saturation oscillations, related to successive apneas in SAS or to apneic episodes in COPD or restrictive patients, were quantified using a new index: delta = 1/n sigma 1 n magnitude of delta(SaO2)/delta(t)(12-s intervals) Twenty-six patients (15 SAS, 8 COPD, and 3 restrictive patients) were included in a prospective study comparing nocturnal oximetry and polysomnography over 34 nights. In apneic patients, we found a strong correlation (r2 = 0.73, p less than 0.01) between time spent in apnea and the delta index. In COPD, the number of apneas was also correlated to the delta index (r2 = 0.92, p less than 0.01). A lower threshold for delta of 1.5 is accurate enough to detect apneas if initial SaO2 is greater than 93 percent. If initial SaO2 is greater than 93 percent, the delta threshold should be 0.8 (sensitivity 95 percent). Such a method could contribute to the accurate selection of patients for polysomnography.     

A nasal cannula can be used to treat obstructive sleep apnea

RATIONALE: Obstructive sleep apnea syndrome is due to upper airway obstruction and is associated with increased morbidity. Although continuous positive airway pressure efficaciously treats obstructive apneas and hypopneas, treatment is impeded by low adherence rates. OBJECTIVES: To assess the efficacy on obstructive sleep apnea of a minimally intrusive method for delivering warm and humidified air through an open nasal cannula. METHODS: Eleven subjects (age, 49.7+/-5.0 yr; body mass index, 30.5+/-4.3 kg/m2), with obstructive apnea-hypopnea syndrome ranging from mild to severe (5 to 60 events/h), were administered warm and humidified air at 20 L/minute through an open nasal cannula. MEASUREMENTS AND MAIN RESULTS: Measurements were based on standard sleep-disordered breathing and arousal indices. In a subset of patients pharyngeal pressure and ventilation were assessed to determine the mechanism of action of treatment with nasal insufflation. Treatment with nasal insufflation reduced the mean apnea-hypopnea index from 28+/-5 to 10+/-3 events per hour (p<0.01), and reduced the respiratory arousal index from 18+/-2 to 8+/-2 events per hour (p<0.01). Treatment with nasal insufflation reduced the apnea-hypopnea index to fewer than 10 events per hour in 8 of 11 subjects, and to fewer than 5 events per hour in 4 subjects. The mechanism of action appears to be through an increase in end-expiratory pharyngeal pressure, which alleviated upper airway obstruction and improved ventilation. CONCLUSIONS: Our findings demonstrate clinical proof of concept that a nasal cannula for insufflating high airflows can be used to treat a diverse group of patients with obstructive sleep apnea.     

Bedtime Ethanol Increases Resistance of Upper Airways and Produces Sleep Apneas in Asymptomatic Snorers

Nasal continuous positive airway pressure (nasal CPAP) and polysomnography were used to analyze the time course of the effect of bedtime ethanol on resistance of upper airways and on the number of respiratory pauses during sleep. On one night, six asymptomatic nonalcoholic male snorers drank 2 ml/kg of 100 proof vodka mixed in orange juice (ethanol dose, 0.79 gm/kg, giving a peak blood alcohol level of 71.8 +/- 33.3 mg/dl). On a second night they received a placebo (1-2 drops of vodka floated on top of the orange juice). We measured (a) the minimum nasal (CPAP) required to eliminate snoring, (b) the number of hypopneas and apneas during each hour of sleep and (c) the arterial oxygen saturation (SaO2) by ear oximetry. On the alcohol night there was a significant increase in the CPAP pressure required to eliminate snoring (placebo 4.8 +/- 1.7 cm H2O, alcohol 6.2 +/- 1.5 cm H2O). The number of respiratory events per hour of sleep (apnea index) was 7.5 +/- 2.1 for ethanol nights versus 3.8 +/- 2.7 for placebo nights (p less than 0.0125). An apnea index of greater than 5 is generally considered abnormal. There was no significant difference in the number of desaturation events (declines of 4% or more in the SaO2) or in the mean SaO2, but the minimum SaO2 was significantly lower on the ethanol night (placebo 89.8% +/- 1.6, alcohol 86.8% +/- 2.7, p less than 0.05). The effect of this dose of alcohol on airway resistance was most pronounced during the first 2 hr after ingestion.     

Effect of cardiac output reduction on rate of desaturation in obstructive apnea.

The nadir of SaO2 during an obstructive apnea is dependent upon the apnea's duration and the rate of fall of saturation (dSaO2/dt). We postulated that a low Q, such as in patients with congestive heart failure with sleep apnea, or a reduction in Q, as seen in some humans during obstructive sleep apnea, might steepen dSaO2/dt. The mechanism postulated was lowering of SvO2 with increased pulmonary capillary blood oxygen uptake and faster depletion of alveolar oxygen. This study examines dSaO2/dt following the onset of apnea in eight spontaneously breathing adult baboons. Nonrepetitive obstructive apneas (30, 45, and 60 seconds) were created by clamping an indwelling cuffed endotracheal tube at the end of expiration. Following baseline measurements, the animals were given a bolus of a rapid-acting beta-adrenergic blocker followed by continuous infusion to reduce cardiac output and to limit the cardiovascular response to obstructive asphyxia. Fiberoptic catheters were used for continuous monitoring of SaO2, SvO2, and cardiac output. Esophageal pressure and relative thoracic gas volume (Respitrace) were monitored to insure equivalence of lung volume at the onset of apnea. Beta-adrenergic blockade reduced resting Q by a mean of 25 percent. The blocked vs unblocked dSaO2/dt was 0.73 vs 0.72 percent/s, 0.76 vs 0.73 percent/s, and 0.70 vs 0.71 percent/s for 30-second, 45-second, and 60-second apneas, respectively. Thus, mean dSaO2/dt for all durations of apneas was unaffected by beta-adrenergic blockade. We concluded that dSaO2/dt is not influenced by limited Q preceding or induced by obstructive asphyxia.