Association of body position with severity of apneic events in patients with severe nonpositional obstructive sleep apnea

STUDY OBJECTIVE: To compare the severity of sleep apneic events occurring in the supine posture vs the severity of sleep apneic events occurring in the lateral posture in patients with severe obstructive sleep apnea (OSA). DESIGN: A retrospective analysis of apneic event variables in a group of 30 OSA patients who underwent a complete polysomnographic evaluation in our sleep disorders unit. PATIENTS: Thirty patients with severe OSA (respiratory disturbance index [RDI] = 70.1+/-18.2) who were nonpositional patients (NPP), ie, in whom the ratio of the supine RDI to the lateral RDI is < 2 (supine RDI = 85.7+/-11.7, lateral RDI = 64.8+/-17.3), and who had > or =30 apneic events in the lateral position and 30 apneic events in the supine position during sleep stage 2 were included in the study. MEASUREMENTS: For the 30 apneic events in each body position, the following variables were evaluated: apnea duration (ApDur), minimum desaturation (MinDes), Delta desaturation (Delta-Des), duration of arousal (DurArous), maximum snoring loudness (MaxSL), and Delta heart rate (Delta-HR). In addition, three other variables assessed as a ratio of ApDur (Rate-D = Delta-Des/ApDur, R-HR =Delta-HR/ApDur, and R-Arous = DurArous/ApDur) were also calculated. RESULTS: For all variables evaluated, apneic events occurring in the supine posture were significantly more severe than those apneic events occurring in the lateral posture during sleep stage 2. ApDur of both body postures correlated significantly with DurArous, Delta-HR, and MaxSL, but not with Delta-Des and MinDes. ApDur correlated linearly with DurArous for both postures. The slopes of the two regression lines were similar (p = 0.578) but the regression line intercept for the supine apneas was significantly higher than that of lateral apneas (p<0.0001). In addition, the average number of supine apneic events that did not end with an arousal was smaller than the average number of lateral apneic events not ending with an arousal (4.4+/-6.0 vs. 10.5+/-6.7, respectively; p< 0.0001). Also, only 4 of 900 (0.44%) apneic events analyzed in the lateral posture ended with an awakening (> 15 s), whereas in the supine posture, there were 37 (4.1%) such events (p<0.001). CONCLUSIONS: These results show that even in patients with severe OSA who have a high number of apneic events in the supine and lateral posture, the apneic events occurring in the supine position are more severe than those occurring while sleeping in the lateral position. Thus, it is not only the number of apneic events that worsen in the supine sleep position but, probably no less important, the nature of the apneic events themselves.     

Postural breathing pattern changes in patients with myotonic dystrophy

We recorded by pneumotachography the breathing in nine patients with myotonic dystrophy (MD), both seated and supine and with eyes open in both positions. Irregular breathing (coefficient of variation >20% for VT and TTOT) was observed in six of the patients, two of whom showed irregularity in both positions whilst the remaining four had irregular breathing only when supine. In addition, in this latter group, irregularities first appeared in VT and only after a few minutes in TTOT. Whereas in the group exhibiting irregular breathing in both seated and supine positions, irregularities were observed throughout the recording. However, no significant difference in any ventilatory variable was observed as between the two postures. Rib cage (RC) and abdomen (AB) motions were recorded by uncalibrated respiratory inductance plethysmography. Although for MD patients the mean values of the RC/AB ratio lay within the normal range the relative decrease in value as between seated (0.78+/-0.52) and supine (0.31+/-0.13) position was less than in healthy subjects. These observations suggest that MD may cause deficiencies in several mechanisms. Analyses of the respiratory pattern in each patient may provide information leading to the identification of the impaired respiratory mechanisms.     

Prevalence of positional sleep apnea in patients undergoing polysomnography

STUDY OBJECTIVES: The primary aim of this study was to determine the prevalence of positional obstructive sleep apnea using a functional definition. Positional sleep apnea was defined as a total apnea-hypopnea index (AHI) > or = 5 with a > 50% reduction in the AHI between the supine and nonsupine postures, and an AHI that normalizes (AHI < 5) in the nonsupine posture. A secondary aim was to determine if positional sleep apnea can be diagnosed accurately during a split-night study. DESIGN: Retrospective chart review. SETTING: Two sleep centers in Buffalo, NY, one a Veterans Affairs Western New York Healthcare System Sleep Center (VAWNY) and the other a freestanding ambulatory center (Associated Sleep Center [ASC]). PATIENTS: Three hundred twenty-six patients from the VAWNY, including 57 patients who underwent a split-night study and 242 patients from the ASC who underwent polysomnography. INTERVENTIONS: None. MEASUREMENTS: Patient characteristics and sleep study results. RESULTS: Positional sleep apnea was seen in 49 of 99 patients (49.5%) with mild sleep apnea (AHI, 5 to 15/h), 14 of 72 patients (19.4%) with moderate sleep apnea (AHI, 15 to 30/h), and 5 of 77 patients (6.5%) with severe sleep apnea (AHI > 30/h). Sufficient sleep (> 15 min) in both postures was not seen in 104 of 269 patients (38.7%) and 80 of 242 overnight studies (33.1%) at the VAWNY and ASC, respectively, and was not seen in 47 of 57 split-night studies (82.5%). The percentage of studies with insufficient sleep in both postures was significantly greater for split-night studies (p < 0.0001). CONCLUSIONS: Positional sleep apnea is common particularly in patients with mild disease. Positional sleep apnea cannot usually be assessed during a split-night study.     

Roentgenographic dimensions of the upper airway in snoring patients with and without obstructive sleep apnea

The purpose of this study was to examine whether a simple test, such as routine roentgenographic views of the upper airway, is useful in identifying anatomic narrowing of the airway in patients with sleep apnea. To accomplish this, we prospectively studied a group of 117 patients (95 male and 22 female subjects) referred for evaluation of heavy snoring and possible obstructive sleep apnea. All patients had full nocturnal polysomnography, including measurements of snoring. Lateral view of the airway obtained after swallowing contrast material was used to measure pharyngeal diameters at three sites along the airway. All measurements were performed with the patients standing and supine. We used three different definitions of sleep apnea (apnea/hypopnea index of 10, 20, and 40), and compared airway diameters between the apneic and nonapneic snorers. Only when sleep apnea was defined as greater than 40 apneas plus hypopneas per hour of sleep was there a significant difference in airway diameter at the tip of the palate and 1 cm distal to it between apneic and nonapneic snorers. Both groups of patients demonstrated a significant reduction in the retropalatal distance on assumption of the supine posture. Stepwise, forward, multiple linear regression analysis showed that the retropalatal distance and airway diameter at the tip of the palate and 1 cm distal to it were significant predictors of snoring, but not apnea. We conclude that (1) airway diameters account for some of the variability in snoring, and (2) they do not differentiate between apneic and nonapneic snorers.     

Assessment of sleep studies in myotonic dystrophy

Myotonic dystrophy (MD) is the commonest adult muscular dystrophy and is associated with respiratory muscle weakness. The role of screening sleep studies is unclear in MD. We prospectively evaluated polysomnography/overnight oximetry in a group of MD patients and related this to the daytime respiratory function in an attempt to evaluate the usefulness of screening sleep studies. Twenty-five patients with type I MD [15 males; mean age (SD) 40.0 (10.9) years] who had at least one symptom suggestive of nocturnal hypoventilation were included in the study. We performed spirometry, maximal inspiratory and expiratory mouth pressures, sniff nasal inspiratory pressure, arterial blood gases and polysomnography or overnight oximetry. Excessive tiredness and sleepiness were the most common presenting symptoms. Prevalence of sleep related breathing disorder (SRBD) was 36%. FVC was found to be normal in 33% of subjects with significant SRBD. Mouth pressures were reduced more than FVC, even in patients with normal overnight oxygen saturation. Of all the daytime measures, FVC correlated best with arterial carbon dioxide tension (r = -0.7). Sleep studies were useful to identify a small group of myotonic dystrophy patients (12%, three out of 25 in our series) with SRBD that would have been missed with routine daytime assessments. Targeted sleep monitoring in patients who are older, with multiple symptoms suggestive of SRBD, especially if they are overweight seems to be the best way to utilize the existing resources. Home unattended oximetry was well tolerated and offers a practical screening tool in this challenging patient group where excess daytime sleepiness is often due to causes other than SRBD.     

Cycle length identifies obstructive sleep apnea and central sleep apnea in heart failure with reduced ejection fraction

Aim

To clarify whether unmasking of central sleep apnea during continuous positive airway pressure (CPAP) initiation can be identified from initial diagnostic polysomnography (PSG) in patients with heart failure with reduced ejection fraction (HFREF) and obstructive sleep apnea (OSA)

Materials and methods

Forty-three consecutive patients with obstructive sleep apnea and central sleep apnea (OSA/CSA) in HFREF were matched with 43 HFREF patients with OSA and successful CPAP initiation. Obstructive apneas during diagnostic PSG were then analyzed for cycle length (CL), ventilation length (VL), apnea length (AL), time to peak ventilation (TTPV), and circulatory delay (CD). We calculated duty ratio (DR) as the ratio of VL/CL and mathematic loop gain (LG).

Results

While AL was similar, CL, VL, TTPV, CD, and DR was significantly longer in patients with OSA/CSA compared to those with OSA, and LG was significantly higher. Receiver operator curves identified optimal cutoff values of 50.2 s for CL (area under the curve (AUC) 0.85, 29.2 s for VL (AUC 0.92), 11.5 s for TTPV (AUC 0.82), 26.4 s for CD (AUC 0.79), and 3.96 (AUC 0.78)) respectively for LG to identify OSA/CSA.

Conclusion

OSA/CSA in HFREF can be identified by longer CL, VL, TTPV, and CD from obstructive events in initial diagnostic PSG. The underlying mechanisms seem to be the presence of an increased LG.

     

Central sleep apnea. Improvement with acetazolamide therapy

Respiratory rhythm during sleep may be dependent on blood pH with apneas being associated with alkalosis. Acidification may therefore have therapeutic value in some forms of sleep apnea. We administered acetazolamide to six patients with symptomatic central sleep apnea, a disorder of respiratory rhythm with little or no upper airway obstruction. Sleep studies were carried out before and after one week of drug therapy, during which time the mean arterial pH decreased from 7.42 to 7.34. All six patients had significant improvement, demonstrating a 69% reduction in total apneas. Five of the six patients reported better-quality sleep and decreased daytime hypersomnolence. Subsequent studies in normal subjects showed that acetazolamide, like other agents known to produce a metabolic acidosis, shifted the hypercapnic ventilatory response to the left 5 +/- 0.54 mm Hg. This may be important in mediating the observed decrease in apneas.     

Effects of expiratory positive airway pressure on sleep-induced respiratory abnormalities in patients with hypersomnia-sleep apnea syndrome

In order to explore the efficacy of expiratory positive airway pressure (EPAP) in the prevention of sleep-induced respiratory abnormalities, we studied 9 patients with typical presentation of hypersomnia-sleep apnea syndrome 1 wk apart, without and with 10 cm water of EPAP. We found that EPAP significantly reduced apnea index (p less than 0.01), maximal and mean duration of apneas (p less than 0.01) and desaturation index (p less than 0.001), and significantly improved mean and minimal oxygen saturation (p less than 0.01) and awake supine arterial oxygen saturation (p less than 0.01) in all 9 patients. We also found that EPAP significantly decreased the relative time spent in Stages 1 and 2 NREM sleep (p less than 0.01) and increased the relative time spent in Stages 3 and 4 NREM sleep (p less than 0.01). These results indicate that EPAP reduces frequency and duration of apneas and the degree of nocturnal oxygen desaturation and improves sleep quality in patients with hypersomnia-sleep apnea syndrome.     

The effects of aminophylline on sleep and sleep-disordered breathing in patients with obstructive sleep apnea syndrome

The methylxanthine derivatives are known to have respiratory stimulant properties. To determine whether these drugs would improve obstructive sleep apnea, 10 male patients with obstructive sleep apnea (OSA) (Apnea Index greater than 15/h) were given infusions of aminophylline and a saline placebo on 2 separate nights a week apart, using a randomized crossover design. There was a significant decrease during aminophylline infusion in the frequency of those apneas, which contained periods of complete respiratory inactivity (central and mixed apneas; placebo, 4.3 +/- 1.8/h; aminophylline, 0.7 +/- 0.5/h; p less than 0.05). There was no change in either the frequency (placebo, 31.8 +/- 5.9/h; aminophylline, 28.7 +/- 8.7/h; NS) or duration of obstructive apneas. Mean and minimal arterial oxygen saturation values were also unchanged. Sleep architecture was markedly disturbed by aminophylline. There was a reduction in sleep efficiency (placebo, 84.8 +/- 2.0%; aminophylline, 60.2 +/- 5.0%; p less than 0.005), an increase in sleep fragmentation (sleep stage shifts/h: placebo, 11.6 +/- 1.3: aminophylline, 21.0 +/- 2.9; p less than 0.05) and less Stage 2 and more Stage 1 non-REM sleep. We conclude that aminophylline reduces central apnea and the central component of mixed apneas but has no effect on obstructive apnea. Theophylline is therefore unlikely to be therapeutically useful in patients with OSA, and because it leads to marked sleep disruption, its long-term use could conceivably increase the propensity to upper airway occlusion during sleep.     

Sleep apnea in adult myotonic dystrophy patients who have no excessive daytime sleepiness

Purpose  

Sleep apnea is common in myotonic dystrophy (MD) and may cause respiratory failure. Most of the sleep studies have been performed in patients with excessive daytime sleepiness (EDS), which is a characteristic and strong predictor of sleep apnea. Therefore, we investigated the prevalence of sleep apnea in adult MD patients who have no EDS.     

Prevalence and clinical correlates of sleep disordered breathing in myotonic dystrophy types 1 and 2

Purpose

Myotonic dystrophy types 1 (DM1) and 2 (DM2) are the most common muscular dystrophies in adulthood. A high prevalence of excessive daytime sleepiness (EDS) and sleep disordered breathing was documented in DM1; however, there are limited data available regarding DM2. Goals of the study were: (1) to evaluate the prevalence of sleep apnea in a large cohort of patients (71 DM1 and 14 DM2) and (2) to analyze correlations among such disorders and clinical features of myotonic dystrophies.

Methods

All patients underwent clinical examination, subjective sleep evaluation, and home based cardiorespiratory monitoring, and most of them performed pulmonary function tests and oropharyngeal–oesophageal scintigraphy (OPES).

Results

Almost 45 % of patients reported poor sleep quality; only 20 % of them referred EDS. Sleep studies documented sleep apnea, mostly obstructive, in 69 % DM1 patients and 43 % DM2 patients; overall, 28 % of cases needed non-invasive ventilation. Neither age, gender, illness duration, body mass index, muscle involvement, OPES respiratory function indexes, nor n(CTG) in leukocytes were predictive of sleep apnea in DM1 patients. Conversely, in DM1 the central apnea–hypopnea index is correlated with the oral transit time estimated by OPES, whereas in DM2 apnea indexes are correlated with pulmonary function parameters.

Conclusions

Sleep apnea is highly prevalent in both forms of myotonic dystrophies. In DM1, no clinical parameters appear to be predictive, while age appears to influence the severity of the obstructive variant; in DM2, the severity of sleep apnea is correlated with the degree of respiratory muscle involvement. Considering the harmful consequences of sleep apnea on cardiorespiratory function, our findings suggest including PSG in the follow-up of myotonic dystrophies.     

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.     

体位对急性脑梗死患者睡眠呼吸紊乱的影响

目的探讨睡眠体位对脑梗死患者睡眠呼吸紊乱的影响和作用机制。方法选择急性脑梗死患者53例,分为睡眠呼吸暂停综合征(SAHS)组34例,非SAHS组19例。采用视频多导睡眠监测仪,对急性脑梗死患者自然睡眠过程及不同体位睡眠呼吸状况进行全程描记。结果 53例患者中,有34例(64.2%)急性脑梗死患者睡眠呼吸暂停低通气指数(AHI)≥10。与仰卧位比较,SAHS组左、右侧卧位患者的AHI明显降低,平均血氧饱和度明显升高(P<0.05,P<0.01);且睡眠呼吸紊乱事件以阻塞型为主,仰卧位最重(P<0.01);SAHS组患者自然睡眠状态下,AHI与侧卧位/仰卧位睡眠时间比值呈负相关(r=-0.56,P<0.01)。结论脑梗死后睡眠呼吸紊乱发生率高,仰卧位时加重,体位自我调节保护睡眠呼吸的功能减弱。     

Upper airway occlusion during sleep in patients with Cheyne-Stokes respiration

Sleep-induced periodic breathing has been suggested to lead to the development of occlusive apneas in patients with sleep apnea syndrome. If this were true, patients with Cheyne-Stokes respiration should also develop upper airway occlusion during sleep. To study this hypothesis, 6 nonobese patients with Cheyne-Stokes respiration lacking evidence for sleep apnea syndrome and anatomic upper airway abnormalities underwent polysomnography during daytime naps. A total of 463 apneas were analyzed in the 6 patients studied. In 1 patient, no evidence of upper airway occlusion was observed. In the remaining 5 patients, a varying frequency of upper airway occlusion resembling the pattern of mixed apnea was seen in 3 to 97% of the total apneas analyzed. The mean number (+/- 1 SD) of occluded inspiratory efforts per mixed apnea in these 5 patients was 1.69 +/- 0.59. These results show that patients with Cheyne-Stokes respiration may develop upper airway occlusion during sleep and are consistent with the contention that sleep-induced periodic breathing in patients with sleep apnea syndrome is primary to the development of occlusive apneas.     

Cardiogenic oscillations on the airflow signal during continuous positive airway pressure as a marker of central apnea.

Therapeutic decisions in patients with sleep apnea (eg, adjustment of continuous positive airway pressure [CPAP]) depend on differentiating central from obstructive apnea. Obstructive apnea is defined by cessation of airflow in the presence of continued respiratory effort, which is conventionally inferred from chest wall movement or intrathoracic pressure swings. Cardiogenic oscillations in the airflow have been observed during some central apneas, but there is controversy over whether they correlate with airway patency. The present study investigates whether these oscillations are markers of the absence of respiratory effort (central apnea) without regard to airway patency. METHODS: We examined 648 apneas in 52 patients undergoing nocturnal polysomnograms and CPAP titrations. Airflow was measured using the output of the CPAP generator, and apneas were identified from reduction of airflow to < 10% for > 10 s. We used only the presence or complete absence of thoracoabdominal motion to classify apneas: obstructive apnea when motion was present (297 apneas); and central apnea if motion was totally absent (351 apneas). Central apneas most often occurred at sleep onset or followed arousal with a big breath. Using only the flow signal, all apneas were examined for the presence of cardiogenic oscillation by an observer blinded to other signals and apnea types. RESULTS: No obstructive apnea showed definite cardiogenic oscillations. In four cases, there was a suggestion of oscillation that was not regular enough to be called cardiac. Sixty percent of central apneas showed clear, regular oscillations at cardiac frequency. Cardiogenic oscillations also were seen intermittently during quiet exhalation in apnea-free periods. CONCLUSION: The presence of cardiogenic oscillations on the CPAP flow signal is a specific indicator of central apnea and may have a role in self-titrating CPAP algorithms. We speculate that transmission of these cardiac-induced oscillations may relate to the relaxation of thoracic muscles during central apnea and is impeded by high muscle tone during obstructive apnea.     

82例睡眠呼吸暂停低通气综合征的诊断与无创正压通气治疗

目的探讨睡眠呼吸暂停综合征(SAHS)的诊断及自动调节持续气道内正压通气(auto-CPAP)对SAHS的治疗价值。方法82例SAHS患者,均行整夜的多导睡眠仪监测,并对18例中重度患者进行auto-CPAP治疗。结果SAHS患者随病情加重Epworth评分、呼吸紊乱程度、最长呼吸暂停时间、鼾声指数、氧减指数等参数明显增加,最低氧饱和度明显降低。Auto-CPAP治疗后呼吸紊乱和低氧血症的程度显著减轻,中枢性呼吸暂停的次数及所占时间没有明显改变。Epworth评分与呼吸紊乱、低氧血症以及打鼾的的时间和次数有明显的相关关系。结论Auto-CPAP可有效的治疗中重度SAHS患者,消除阻塞性及混合性呼吸暂停,减轻低氧血症,明显改善症状,并具有良好的接受性。夜间频繁出现的低氧血症是导致日间过度嗜睡的重要因素。     

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome

The effect of posture on upper airway dimensions was assessed for two reasons. First, some patients with untreated sleep apnea/hypopnea syndrome (SAHS) report they sleep better sitting upright. Second, to allow comparison of the differing techniques used to determine the site of maximal airway narrowing in awake patients with SAHS, as some are carried out in the erect and others in the supine posture. Lateral cephalometry was therefore carried out in 33 nonsnoring normal subjects and in 29 patients with obstructive SAHS (mean apneas plus hypopneas, 46 per hour; range, 17 to 103). In both normal subjects and patients, uvular width was increased (p less than 0.05) in the supine posture, and this was associated with significant narrowing of the retropalatal airway in the patients with SAHS (erect, 5.0 +/- SD 2.6 mm; supine, 3.6 +/- 2.8 mm; p less than 0.01). In both normal subjects and patients, the retroglossal hypopharynx widened (p less than 0.05) in the supine posture (e.g., in patients with SAHS, posterior airway space was: erect, 11.5 +/- 4.5 mm; supine, 13.4 +/- 4.8 mm; p = 0.003). In the supine posture there was anterior movement of the hyoid and neck flexion in both groups. However, a study of the effect of neck flexion in the erect posture showed that neck flexion produced no changes in airway caliber. Thus, posture is an important determinant of upper airway dimensions.     

Reversal of central sleep apnea using nasal CPAP

Based on the theory that obstructive (OSA) and central (CSA) sleep apneas share common pathophysiologic mechanisms, we attempted to treat eight patients with predominantly CSA by continuous positive airway pressure (CPAP). All patients exhibited repetitive episodes of CSA and mixed sleep apneas (MSA) in the supine position with a mean duration of 23.7 +/- 0.7 s and 34.5 +/- 1.3 s, respectively. The pattern of apnea changed when the subject lay in the lateral position. Five patients were observed to develop OSA in the lateral position with a mean duration of 27.2 +/- 1.5 s, while the other three patients snored continuously. High levels of CPAP (range 9.0 to 16.5 cm H2O) prevented all CSA and MSA and resulted in quiet breathing in all eight patients. Intermediate levels of CPAP produced firstly MSA, then purely OSA and/or continuous snoring. Low levels of nasal CPAP also prevented OSA and snoring occurring in the lateral posture in all subjects (range 2.0 to 8.3 cm H2O). Three patients are currently on home CPAP therapy for a range of four to 36 months. We conclude that upper airway collapse in the supine posture has a key role in the induction of CSA. We suggest that a reflex inhibition of respiration through activation of supraglottic mucosal receptors during passive oropharyngeal airway closure caused CSA in these patients.     

Night-to-night consistency of apneas during sleep

The consistency of apneas from night to night was examined in 2 groups of patients. The first group had more than 100 apneas per night (frequent apnea) and the second group had less than 100 apneas per night (infrequent apnea). All patients underwent clinical polysomnography for 2 nights, with no significant weight change or treatment occurring between recordings. The frequent apnea group showed a consistent number of apneas on the 2 nights (r = 0.92, p less than 0.01), whereas the infrequent apnea group showed a highly variable number of apneas (r = 0.35, p greater than 0.10). The correlations on apnea index (apneas per hours of sleep) showed a similar result. Apnea duration and type were consistent in both groups of patients.     

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.