Search PubMed⌕ Search

Biomedical subjects

M H Sanders

Publications and source records attributed to M H Sanders.

48 records · Page 3Linked to original sources
PubMed1985

Prolonged expiratory phase in sleep apnea. A unifying hypothesis.

The mechanisms responsible for the various sleep apnea patterns have not been elucidated. In 5 hypersomnolent patients, we analyzed 613 events that would have been labeled mixed and central apneas had usual recording sensitivity been employed. Recording air flow at high sensitivity revealed that in most of these events expiratory flow was present throughout most of the prolonged period during which there was no inspiratory effort. In 378 events, resumption of inspiratory effort was unaccompanied by air flow (occluded events), whereas in 144 events resumption of inspiratory effort was accompanied by inspiratory air flow (not-occluded events). In another 91 events, expiratory air flow ceased during the interval between inspiratory efforts and then recommenced unaccompanied by expiratory effort suggesting airway closure and reopening. Because expiratory air flow is present during a substantial portion of the prolonged interval between inspiratory efforts seen in our sleeping patients, we conclude that "apneas" should be defined relative to absence of inspiratory air flow. In addition, it appears that the initial portion of "mixed," and at least some "central apneas," are associated with increased expiratory upper airway resistance.

Adult↗
PubMed1984

Nasal CPAP effect on patterns of sleep apnea.

To evaluate the effect of continuous positive airway pressure via nasal mask (nasal CPAP) on occlusive, mixed, and central apneas (OA, MA, and CA, respectively), we performed nocturnal polysomnography without and with nasal CPAP on 21 patients with sleep apnea. Three patients were unable to tolerate nasal CPAP. The remaining 18 patients had significant reductions in the overall apnea frequency when using nasal CPAP (52.9 +/- 5 per hour slept vs 3.3 +/- 1 per hour slept, mean +/- SE, p less than 0.001). The use of nasal CPAP significantly reduced the frequency of OAs during both nonrapid eye movement (non-REM) and REM sleep (p less than 0.001). It also reduced the frequency of MAs during both non-REM and REM sleep (p less than 0.05). Nasal CPAP did not increase the frequency of CAs in patients who had MAs when sleeping without nasal CPAP indicating that both the "central" and obstructive portions of MA were eliminated. In those patients who had CAs while sleeping without nasal CPAP, the CA frequency was unchanged by nasal CPAP although there was a good deal of interindividual variability. We conclude that nasal CPAP is well tolerated and effective in reducing the frequency of OAs and MAs. The variability of the response of CA to nasal CPAP suggests that the pathogenesis of CA may not be homogeneous.

Adult↗
PubMed1983

Inspiratory and expiratory partitioning of airway resistance during sleep in patients with sleep apnea.

Although the sleep apnea hypersomnolence syndrome (SAHS) is now a widely recognized disorder, little is known about the timing and pathogenesis of the abnormal airway mechanics that lead to airway occlusion. In order to characterize the changes in airway resistance and to determine if abnormal airway mechanics are confined to inspiration or expiration in SAHS, we separately determined the inspiratory and expiratory resistances on the 2 breaths preceding occlusive apnea in 7 patients. We observed that 6 subjects experienced a significant increase in expiratory resistance, and 5 subjects had a significant rise in inspiratory resistance from the second to the first breath before apnea. For the group, the median expiratory resistance increased from 11.5 to 18.6 cm H2O/L/s (p less than 0.05), and the median inspiratory resistance increased from 10.5 to 17.5 cm H2O/L/s (p less than 0.05) on the 2 breaths before apnea. We conclude that airway abnormalities occur during both the expiratory and the inspiratory phases of ventilation on breath(s) leading to apnea and, therefore, the loss of airway patency is not solely an inspiratory phenomenon. It is also apparent that patients with SAHS thus experience both inspiratory and expiratory resistive loading prior to apnea.

Adult↗
PubMed1983

CPAP via nasal mask: a treatment for occlusive sleep apnea.

A 38-year-old man had incapacitating hypersomnolence and severe occlusive sleep apnea. Baseline polysomnography revealed 92.9 apneic episodes per hour of sleep. Application of nasal continuous positive airway pressure through a modified nasal nitrous mask using a ball-valve resistor resulted in reduction of occlusive apnea to 1.17 episodes per hour of sleep and marked improvement in the quality of sleep.

Adult↗
PubMed1982

Acute and long-term ventilatory effects of hyperoxia in the adult sleep apnea syndrome.

Eight adult patients with sleep apnea were studied to evaluate the ventilatory and cardiac effects of hyperoxia on an acute basis. Five patients then used low-flow nighttime oxygen for 30 to 90 days. The results of the acute study showed that for 30-min study periods, the total number of apneas and per cent apnea time (duration of apneas divided by sleep time) decreased significantly from the room air to the oxygen period (207 to 68, p less than 0.05; 41.1 +/- 18.3% SD to 20.5 +/- 14.4%, p less than 0.05, respectively). Also, the apnea-associated slowing in heart rate is blocked by the supplemental oxygen. Three patients receiving oxygen at home decreased their per cent apnea time by greater than 60%. These patients also responded to the acute administration of hyperoxia by a decrease in apnea time greater than 60%. One patient prolonged the apnea time, and one had a minimal positive response, both again reflecting their acute studies. These data suggested that the severe hypoxemia that develops during an apnea in this syndrome has a central ventilatory effect that propagates the apneas and is significantly reversed by hyperoxia.

Adult↗
PubMed1981

The detection of sleep apnea in the awake patient. The 'saw-tooth' sign.

We studied 21 subjects, 13 of whom had the sleep apnea hypersomnolence syndrome associated with upper airway obstruction during sleep (SAHS-UAO) to determine if "saw-toothing" on the flow-volume loop was significantly associated with the phenomenon of airway occlusion during sleep. A "saw-tooth" pattern was present on the flow-volume loop in 11 of 13 subjects with SAHS-UAO. The presence of saw-toothing correlated with fluttering of tissue that was visualized in the upper airway via the fiberoptic bronchoscope. The specificity of the saw-tooth pattern for SAHS-UAO was 100%. Generalized obesity may indirectly influence the presence of saw-toothing due to deposition of what appeared to be adipose tissue in the pharyngeal walls. Although the number of subjects in this study is small, saw-toothing on the flow-volume loop appears to be an important aid in the diagnosis of SAHS-UAO.

Adolescent↗
PubMed1980

Respiratory mechanics and timing during sleep in occlusive sleep apnea.

Six human obese subjects with the sleep apnea hypersomnolence syndrome associated with upper airway occlusion (UAO) were studied during sleep to characterize respiration. Measurements included the timing components of ventilation, pulmonary resistance, flow, and esophageal and gastric pressures before and during UAOs. During the period between UAOs, the resistance progressively increased (9.4-18.1 cmH2O/l(-1) . s, P less than 0.05) as the ventilation decreased (1.82-0.77 l/s, P less than 0.05), but without changes in esophageal pressure swings. During this period, inspiratory time-to-total cycle time decreased (0.42-0.25 s, P less than 0.05) due to expiratory phase prolongation. The apnea began after expiration and terminated on inspiration with the maximal swings in esophageal and gastric pressure near the termination. During the UAO, the respiratory cycle time decreased slightly, but the expiratory pause time was significantly shortened immediately before ventilation. We suggest that the UAO is but one aspect of this syndrome and that a decrease in central nervous system activity diminishes the respiratory drive before the onset of the UAO.

Adult↗