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Relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea.

Previously we showed that CO2 drive is increased in patients with obstructive sleep apnea (OSA). In the present study we would like to evaluate a possible relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea (CSA). We compared the hypercapnic ventilatory response (HCVR) between patients with OSA and CSA. HCVR was correlated with total event time and mean event duration in both groups. 17 normocapnic patients in each group and 14 controls were studied. The apnea patients were matched for apnea-hypopnea index, age, sex, and BMI. SHCVR (slope) tended to be higher in apnea patients than in controls without statistical significancy: controls 1.65 (0.16), CSA 2.17 (0.22), OSA 2.55 (0.35) (l/min per mmHg) (P = 0.13). A significant correlation was found between HCVR and event time in CSA (0.52, P = 0.04) and between HCVR and apnea mean duration in OSA (r = 0.52, P = 0.04). We conclude that while CO2 drive was not statistically increased in both apnea types, small changes can contribute to breathing instability and may increase the total event time (in CSA) but may also shorten the apnea duration (in OSA).

Adult↗

Videoradiography at submental electrical stimulation during apnea in obstructive sleep apnea syndrome. A case report.

Percutaneous submental electrical stimulation during sleep may be a new therapeutic method for patients with obstructive sleep apnea syndrome (OSAS). Electrical stimulation to the submental region during obstructive apnea is reported to break the apnea without arousal and to diminish apneic index, time spent in apnea, and oxygen desaturation. The mode of breaking the apnea by electrical stimulation has not yet been shown. However, genioglossus is supposed to be the muscle responsible for breaking the apnea by forward movement of the tongue. To visualize the effect of submental electrical stimulation, one patient with severe OSAS has been examined with videoradiography. Submental electrical stimulation evoked an immediate complex muscle activity in the tongue, palate, and hyoid bone. This was followed by a forward movement of the tongue which consistently broke obstructive apnea without apparent arousal. Time spent in apnea was diminished but intervals between apnea were not affected.

Electric Stimulation Therapy↗

Postoperative caffeine for preventing apnea in preterm infants.

BACKGROUND: Growing ex-preterm infants who undergo general anesthesia for surgery at about term-equivalent age may have episodes of apnea, cyanosis and bradycardia during the early postoperative period. Caffeine treatment given at the time of operation might prevent these episodes. OBJECTIVES: In ex-preterm infants who undergo general anesthesia for surgery, does the prophylactic use of caffeine prevent episodes of apnea, cyanosis and bradycardia during the postoperative period without clinically important side effects? SEARCH STRATEGY: The standard strategy of the Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal trials, Medline, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants and journal handsearching mainly in the English language. SELECTION CRITERIA: All trials utilising random or quasi-random patient allocation, in which treatment was compared with placebo or no treatment, were included. DATA COLLECTION AND ANALYSIS: The standard methods of the Cochrane Collaboration and its Neonatal Review Group were used to select trials, evaluate quality and to extract data. The methodological quality of each trial was reviewed by the second author blinded to trial authors and institution(s). Each author extracted data separately, compared and resolved differences. Meta-analysis used relative risk and risk difference. MAIN RESULTS: In each trial apnea/bradycardia occurred in fewer treated than control infants. In two trials (Welborn 1989, LeBard 1989) continuous recordings of oxygen saturation detected hypoxaemic episodes (<90 %) in fewer treatment than control infants. No infant in any trial required intubation and mechanical ventilation. No adverse effects were reported. REVIEWER'S CONCLUSIONS: Implications for practice. Caffeine can be used to prevent postoperative apnea/bradycardia and episodes of oxygen desaturation in growing preterm infants if this is deemed clinically necessary. In view of the small numbers of infants studied in these trials and uncertainty concerning the clinical significance of the episodes, caution is warranted in applying these results to routine clinical practice. Implications for research. There is a need to determine which infants might benefit most by this treatment. Studies confined to those most at risk of apnea (prior history, younger postmenstrual age) and those that might require mechanical ventilation (chronic lung disease) would be of value.

Anesthesia, General↗

Relation between polysomnographic parameters and apnea index in obstructive sleep apnea syndrome.

We performed overnight polysomnography in 77 patients for diagnosis of sleep apnea syndrome (SAS) and assessment of severity. Patients were classified into 3 groups according to apnea index (AI): group 1 (G1; no SAS), AI < or = 10 (21 patients), group 2 (G2; moderate SAS), 10 < AI < 40 (34 patients), and group 3 (G3; severe SAS), AI > or = 40 (22 patients). In all 3 groups, 60% of the apneas were obstructive, but the proportion of mixed apnea increased from G1 to G3 (6% in G1, 12% in G2, and 24% in G3). The duration of REM sleep was shorter in G2 and G3 than in G1 (G1 61 min, G2 44 min, G3 41 min; p < 0.03). In G3 a dramatic decrease in deep sleep was noted in comparison with G1 and G2 (G1 29 min, G2 31 min, G3 10 min). The distribution of the apnea in the different sleep stages was similar in G3; in G2, 16 patients had a REM apnea predominance, but in this subgroup duration of REM sleep was longer and AI was lower than in the other 18 G2 patients. So, absence of sleep stage apnea predominance and high proportion of mixed apnea were observed in the most severe SAS.

Carbon Dioxide↗

Recurrence of sleep apnea syndrome following tracheostomy. A shift from obstructive to central apnea.

This report describes an unusual case of severe obstructive sleep apnea and alveolar hypoventilation leading to hypersomnolence and cor pulmonale, which were corrected by tracheostomy. Four years later, after a 22.5-kg weight gain, nocturnal apneas of similar frequency, duration, and depth of desaturation reappeared but were totally central in origin. The central apneas were eliminated with home nocturnal positive-pressure ventilation via cuffed tracheostomy tube. Each time the patient's apneas were corrected (obstructive: tracheostomy; central: mechanical ventilation), daytime alveolar hypoventilation disappeared rapidly. Yearly right heart catheterizations and radionuclide ejection fractions documented pulmonary hypertension and right heart failure, with resolution following tracheostomy and recurrence after appearance of central apneas. The changes in hemodynamic status corresponded to the patient's weight, presence of apnea, daytime alveolar hypoventilation, and treatment of nocturnal oxyhemoglobin desaturation. This case illustrates the theory of a common etiology of both central and obstructive apnea through abnormal respiratory controller gain and points to several roles obesity may play in apnea.

Humans↗

[Ambulatory monitoring of frequency of apnea in patients with suspected sleep apnea syndrome. Comparative studies using a thermistor sensor].

To record and evaluate the number and duration of nocturnal apneas, and easy method is needed in an outpatient setting. New methods such as recording the tracheal sounds, heart frequency, and O2 saturation, are now available. Recording of thermal convection by Thermistor has not been performed on an outpatient basis so far. Hence, we developed a method by which a thermistor was placed on a mask to record the nasal and oral flow. A specially developed computer hardware evaluates date, time, period, number and mean values of the apneas. The parameters were compared with the conventional methods of recording apneas (thoracic and abdominal movement. O2 saturation, heart frequency and 3 thermistors at mouth and nose). 20 patients, mean age 53.1 +/- 1.6 years, were examined. In 12 patients the apnea frequency was between 0 and 50 apneas per night, in 8 between 50 and 550. Patients with an apnea frequency of more than 50 per night (polygraphy) could be identified with the thermistor method. Our results show that the method is sensitive in respect of the oral and nasal flow. The method seems valid to differentiate between normal persons and patients with increased risk of apnea syndrome.

Adult↗

Fatigue in obstructive sleep apnea: driven by depressive symptoms instead of apnea severity?

OBJECTIVE: Obstructive sleep apnea is a common and frequently devastating illness that often includes significant fatigue. Fatigue is also a hallmark depressive symptom. The authors wondered if depressive symptoms in patients with obstructive sleep apnea would account for some of the fatigue beyond that explained by obstructive sleep apnea severity. METHOD: Sixty patients with obstructive sleep apnea-i.e., score >/=15 on the respiratory disturbance index (mean score=49; range=15-111)-underwent polysomnography and completed the Center for Epidemiological Studies Depression Scale (CES-D Scale), Profile of Mood States (POMS), and Medical Outcomes Study surveys. Data were analyzed by using hierarchical regression, with POMS fatigue score as the dependent variable (step 1, forced entry of apnea severity variables; step 2, forced entry of CES-D Scale score). RESULTS: Whereas score on the respiratory disturbance index and the percent of time oxygen saturation was <90% together accounted for 4.2% of variance in scores on the POMS fatigue scale, the CES-D Scale score accounted for 10 times the variance (i.e., an additional 42.3%) in POMS fatigue scale score. CONCLUSIONS: After obstructive sleep apnea severity was controlled, higher levels of depressive symptoms were dramatically and independently associated with greater levels of fatigue. Assessment and treatment of mood symptoms-not just treatment of the disordered breathing itself-might reduce the fatigue experienced by patients with obstructive sleep apnea.

Depressive Disorder↗

Diaphragmatic and genioglossus electromyographic activity at the onset and at the end of obstructive apnea in children with obstructive sleep apnea syndrome.

We studied the activity of the diaphragm and of the genioglossus at the onset and at the end of obstructive sleep apnea in children. Seven children (mean age 46 months, range 15-87) with obstructive sleep apneas mainly due to enlarged tonsils were tested during natural sleep. We recorded sleep stages (neurophysiological criteria), nasal and buccal air flow (thermistors), thoracoabdominal motion (magnetometers), genioglossus and diaphragm electromyographic activity (EMG) (surface electrodes), and transcutaneous partial pressure of oxygen (Radiometer 44 degrees C). A total of 153 obstructive apneas for the whole group of patients was studied. Compared to the preceding unoccluded breaths, genioglossus and diaphragm EMG data showed that 1) at the onset of obstructive apnea there was no significant decrease in genioglossus and/or diaphragm EMG, contrasting with published data for obese adults, and 2) at the end of obstructive apnea, significant preferential increase in genioglossus EMG, not related to the decrease in transcutaneous partial pressure of oxygen, was found as in obese adults. This study showed that different mechanisms may control the onset of obstructive apnea in children as compared to adults, whereas children and obese adults share the same preferential increase in genioglossus EMG at the end of obstructive apnea.

Child↗

Management of obstructive sleep apnea syndrome in the home. The role of portable sleep apnea recording.

Unattended four-channel sleep apnea recording has been shown to be an accurate tool in the diagnosis of moderate to severe obstructive sleep apnea. We selected 11 patients with severe obstructive sleep apnea who had an apnea-hypopnea index (AHI) determined by unattended sleep apnea recording. The mean AHI was 41 (SD, 17.5). We began nasal continuous positive airway pressure (NCPAP) at home empirically with 5 cm to 7.5 cm of pressure for several nights. We then adjusted the level of NCPAP after telephone interview with the patients and their significant others. The level of NCPAP was increased by 2.5-cm increments until the patients reported cessation of snoring and symptom improvement. The mean NCPAP was 8.0 cm (SD, 1.4). We repeated the overnight sleep apnea recording while on NCPAP in all patients at home to determine their response to therapy. All 11 patients had documented return of their AHI to normal (mean AHI, 2.4; SD, 1.6). Statistically significant improvement was noted in the number of obstructive apneas, hypopneas, total respiratory events, and the AHI. Follow-up data confirmed that patients had improvement in their symptoms and remained compliant with therapy (mean follow-up = 18 months; SD, 10.2). No serious complications were encountered when NCPAP was introduced in an unattended setting. We were able to diagnose and treat these patients in an entirely outpatient setting.

Adult↗

Respiratory effort during sleep apneas after interruption of long-term CPAP treatment in patients with obstructive sleep apnea.

Apneas generally reappear in patients with obstructive sleep apnea (OSA) when treatment with continuous positive airway pressure (CPAP) is interrupted. However, a single-night treatment interruption may be associated with a lesser severity of sleep apneas than before treatment. We hypothesized that this decrease in severity of sleep apneas reflects changes in the respiratory response to upper airway obstruction. Therefore, we compared indexes of respiratory effort during sleep in 25 patients with OSA before and after 1 year of CPAP treatment. Respiratory effort was assessed by means of an esophageal balloon. After 1 year of CPAP treatment, there was a decrease in the maximal end-apneic esophageal pressure swings (Pes) (from 56.7 +/- 5.4 to 30.3 +/- 2.6 cm H2O; p = 0.000; mean +/- SEM), in the overall increase in Pes during an apnea (35.2 +/- 3.6 vs 16.5 +/- 1.5 cm H2O; p = 0.000), as well as the rate of increase in Pes (1.1 +/- 0.1 vs 0.6 +/- 0.1 cm H2O/s; p = 0.000). Although body mass index (BMI) did not change significantly, the individual changes in BMI significantly correlated with the changes in respiratory effort after 1 year of CPAP treatment. Apnea duration and apnea-related oxygen desaturation also decreased significantly. We conclude that long-term CPAP treatment induces changes in respiratory control that persist at least on the first night of treatment interruption.

Esophagus↗

A possible mechanism for mixed apnea in obstructive sleep apnea.

Hypopneas or pauses in respiratory effort frequently precede episodes of obstructive sleep apnea resulting in mixed apneas. We studied five subjects after chronic tracheostomy for obstructive sleep apnea. During stable non-REM (NREM) sleep, subjects breathed entirely through the tracheostomy. Tracheostomy occlusion caused experimental obstructive apnea which lasted 13.9 +/- 4.7 sec and ended with transient arousal and pharyngeal opening. At the end of the apnea there was marked hyperventilation (inspired minute ventilation rose 21.6 +/- 3.5 L on the first breath) followed by hypocapnia, hypopnea, and pauses in inspiratory effort as the subjects resumed NREM sleep. Hypocapnia was greater before inspiratory pauses lasting at least 5 sec than before shorter pauses (PETco2, 4.2 +/- 1.8 mm Hg below baseline vs 1.2 +/- 2.5 mm Hg below baseline). In three patients, pauses in inspiratory effort following experimental obstructive apnea were prevented by administration of 4 percent CO2 and 40 percent O2 inspired gas. This study suggests that: hyperventilation with hypocapnia occurs at the termination of obstructive apneas, and hypocapnia may be responsible for the attenuation or cessation of respiratory effort initiating the subsequent cycle of obstruction.

Adult↗

Correlation between severity of endoscopic findings and apnea-hypopnea index in patients with gastroesophageal reflux disease and obstructive sleep apnea.

AIM: To assess the relationship between severity of gastroesophageal reflux disease and apnea-hypopnea index (AHI) as an indicator of the severity of obstructive sleep apnea. METHODS: Data of 57 patients with proven obstructive sleep apnea and gastroesophageal reflux disease were analyzed. Patients were divided into two groups according to severity of the sleep apnea: "mild-moderate" (A)-AHI >or=5-30, n = 27, "severe" (B)-AHI >30, n = 30. All patients underwent apnea monitoring during the night, upper panendoscopy and were asked about typical reflux symptoms. RESULTS: All examined patients in both groups showed a significant overweight and there was a positive correlation between body mass index and the degree of sleep apnea (P = 0.0002). The occurrence of erosive reflux disease was significantly higher in "severe" group (P = 0.0001). Using a logistic regression analysis a positive correlation was found between the endoscopic severity of reflux disease and the AHI (P = 0.016). Forty-nine point five percent of the patients experienced the typical symptoms of reflux disease at least three times a week and there was no significant difference between the two groups. CONCLUSION: A positive correlation can be found between the severity of gastroesophageal reflux disease and obstructive sleep apnea.

Adult↗

Hypoxic and hypercapneic arousal responses and prediction of subsequent apnea in apnea of infancy.

Hypoxic and hypercapneic arousal responses from quiet sleep were tested in 56 infants with apnea of infancy (one or more episodes of cyanosis, limpness, and apnea requiring vigorous stimulation or resuscitation with no treatable cause; age 6.8 +/- 1.1 [SEM] months). Responses were compared with those of nine control infants ranging from 1 to 25 months of age. To assess hypercapneic arousal, the inspired PCO2 was rapidly increased during quiet sleep to 60 mm Hg or until arousal (restlessness, agitation, eye opening) occurred. All control infants and those with apnea of infancy aroused to hypercapnea, but control infants aroused at a lower inspired PCO2 (inspired PCO2 40.1 +/- 2.6 mm Hg) than those with apnea of infancy (inspired PCO2 46.9 +/- 1.5 mm Hg, P less than .05). To assess hypoxic arousal, the inspired PO2 was rapidly decreased during quiet sleep to 80 mm Hg or until arousal occurred. All control infants aroused to hypoxia (inspired PO2 78.3 +/- 2.1 mm Hg). However, only 38% of those with apnea of infancy aroused (inspired PO2 78.1 +/- 0.8 mm Hg), indicating an abnormality in recognition of hypoxia, or central brainstem response to hypoxia. During the 10.4 +/- 1.2 months of follow-up, there was a high incidence of subsequent apneas (greater than 20 seconds) during sleep at home in 50 apneic infants. Infants with abnormal hypoxic arousal responses had more severe subsequent apneas than those with normal hypoxic arousal responses (P less than .05).

Arousal↗

Sleep apnea avoidance pillow effects on obstructive sleep apnea syndrome and snoring.

UNLABELLED: The study was performed to determine the ability of a new inclined pillow to treat snoring and obstructive sleep apnea syndrome. The SONA Pillow is a triangular pillow with space to place your arm under the head while sleeping on the side. Twenty-two patients with nocturnal polysomnogram (NPSG)-proven obstructive sleep apnea syndrome were included in this study; the group included 11 mild, 8 moderate, and 3 severe sleep apnea patients. All patients had a second attended NPSG performed while utilizing this specific inclined pillow. The pillow was found to be an effective and easily used treatment for mild (respiratory disturbance index [RDI] 5 to 19) and moderate (RDI 20 to 40) obstructive sleep apnea and snoring. In this group, RDI ranged from 5.1 to 35.2 and decreased on the average from 17 events per hour to fewer than 5 events per hour while utilizing the inclined pillow (<0.0001). Also, a statistically significant difference was noted in rapid eye movement (REM) RDI decrement in all patients with mild to moderate sleep apnea (p=0.001) and the increase in SaO2 was also significant (p=0.004). Overall, snoring was decreased or eliminated (p=0.017). CONCLUSION: A uniquely designed pillow (SONA Pillow) is effective in reducing the number of events in patients with mild to moderate obstructive sleep apnea. Using this pillow also reduces snoring.

Adult↗

Pathogenesis of apneas in hypersomnia-sleep apnea syndrome.

To define the pathogenesis of apneas, eight patients with hypersomnia-sleep apnea syndrome were studied during nocturnal sleep. Diaphragmatic and genioglossal electromyograms quantitated as moving time average activity showed parallel periodic fluctuations resembling the pattern of Cheyne-Stokes breathing. Hypopneas and occlusive apneas occurred at the nadir of these cyclic changes, and mixed apneas represented an extreme of this periodicity with no inspiratory activity at the nadir of the cycle. Tracings of central apneas were compatible with an extremely prolonged expiratory phase. Electromyogram activity of both muscles showed an inversely linear relationship with oxygen saturation but genioglossal activity at the resolution of upper airway occlusion was increased out of proportion to the increase in diaphragmatic activity and the degree of oxygen desaturation. These results indicated that occlusive and mixed apneas result from an instability of ventilatory control during sleep, which seems to be an exaggeration of periodic breathing observed at sleep onset.

Adult↗

Differences in pharyngeal properties between snorers with predominantly central sleep apnea and those without sleep apnea.

The underlying cause of idiopathic central sleep apnea syndrome is not well understood. We therefore examined the possibility that patients with idiopathic central sleep apnea may have abnormalities of upper airway mechanics that might contribute to the pathogenesis of central apneas. The acoustic reflection technique was used to assess pharyngeal size, lung volume dependence, and pharyngeal "compliance" in 8 patients with idiopathic central sleep apnea, all of whom were snorers, and in 8 weight-matched, snoring control subjects with normal sleep studies. Patients with central sleep apnea when compared with control subjects exhibited markedly increased specific pharyngeal "compliance" (0.12 +/- 0.05 versus 0.03 +/- 0.01 cm H2O-1; p less than 0.001), increased change in pharyngeal area from FRC to RV (0.8 +/- 0.5 versus 0.03 +/- 0.3 cm2; p less than 0.05), and a larger pharyngeal area at FRC (4.7 +/- 0.9 versus 3.8 +/- 0.8 cm2; p less than 0.03). We conclude that increased pharyngeal "compliance" and lung volume dependence may play a role in the etiology of central apneas in this syndrome.

Brain Diseases↗

Sleep apnea syndrome. A critical review of the apnea index as a diagnostic criterion.

The utility of the apnea index (number of apneic events per hour of sleep) in diagnosing sleep apnea syndrome is reviewed. Data from currently extant reports indicate that many otherwise normal, aging subjects may be classified as having sleep apnea syndrome based on the current diagnostic threshold of five apneic episodes per hour: A chi 2 analysis suggests a relationship between age and level of sleep apnea. Several other reports indicate that use of a threshold of five apneic episodes per hour does not reliably predict increased health risk or somnolence in aging subjects. Adjustment of the apnea index, based on studies of aging normal subjects and of aging patients with sleep apnea syndrome is necessary to ensure reliable results in clinical and research applications.

Adult↗