End-tidal carbon dioxide concentration monitoring in obstructive sleep apnea patients.
ABSTRACT The objective of this study was to investigate the end-tidal carbon dioxide concentration (ETco(2)) monitoring in obstructive sleep apnea (OSA) patients during sleep and to explore whether the ETco(2) value may explain a significant portion of the relationship between ETco(2) value and apnea/hypopnea index (AHI) and nocturnal oxygenation indices.
Thirty-eight consecutive patients underwent overnight polysomnography and were synchronously monitored for ETco(2) using an microstream capnometer. Mean and maximum values during wake time and different sleep stages were recorded. We grouped 38 OSA patients into 2 subgroups on the basis of their difference of mean total sleep time and wake time ETco(2) [(T - W) ETco(2)]; one group, 20 patients with (T - W) ETco(2) less than 0, and the other group,18 patients with (T - W) ETco(2) greater than 0.
Group with (T - W) ETco(2) less than 0 patients exhibited higher AHI (mean ± SD, 68.58 ± 22.78 vs. 27.61 ± 19.44 events/h) and lower nocturnal oxygenation indices (minimum Sao(2), 67.85 ± 10.08 vs. 82.61% ± 6.07%; mean Sao(2), 91.29 ± 3.31 vs. 95.15% ± 1.88%) compared with the other group.
In summary, the study provides preliminary data showing that ETco(2) potentially can be used in continuous monitoring of OSA patients. And, (T - W) ETco(2) can indicate the severity of OSA.
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ABSTRACT: Identify polysomnographic and demographic factors associated with elevation of nocturnal end-tidal CO2 in patients with obstructive sleep apnea. Forty-four adult patients with obstructive sleep apnea were selected such that the maximal nocturnal end-tidal CO2 was below 45 mm Hg in 15 studies, between 45 and 50 mm Hg in 14, and above 50 mm Hg in 15. Measurements included mean event (i.e., apneas or hypopneas) and mean inter-event duration, ratio of mean post- to mean pre-event amplitude, and percentage of total sleep time spent at an end-tidal CO2 < 45, 45-50, and > 50 mm Hg. An integrated nocturnal CO2 was calculated as the sum of the products of average end-tidal CO2 at each time interval by percent of total sleep time spent at the corresponding time interval. The integrated nocturnal CO2 was inversely correlated with mean post-apnea duration, with lesser contributions from mean apnea duration and age (R (2) = 0.56), but did not correlate with the apnea-hypopnea index, or the body mass index. Mean post-event to mean pre-event amplitude correlated with mean post-apnea duration (r = 0.88, p < 0.001). Mean apnea duration did not correlate with mean post-apnea duration. Nocturnal capnometry reflects pathophysiologic features of sleep apnea, such as the balance of apnea and post-apnea duration, which are not captured by the apnea-hypopnea index. This study expands the indications of capnometry beyond apnea detection and quantification of hypoventilation syndromes. Jaimchariyatam N; Dweik RA; Kaw R; Aboussouan LS. Polysomnographic determinants of nocturnal hypercapnia in patients with sleep apnea. J Clin Sleep Med 2013;9(3):209-215.Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 01/2013; 9(3):209-215. DOI:10.5664/jcsm.2480 · 2.83 Impact Factor
Article: The Obese Parturient.International anesthesiology clinics 01/2013; 51(3):136-163. DOI:10.1097/AIA.0b013e3182988c82
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ABSTRACT: Numerical simulation is an effective tool to study the biomechanical mechanism of the upper airway collapse, but few previous studies have considered the effect of the neural control. Based on a finite element model including airway, skull, neck, hyoid and soft tissue around the upper airway, the effect of the neural control on the upper airway collapse was studied with fluid-structure interaction method. Spring element was used to simulate the function of the muscle group. The results show that the strain concentration disappears and the airway resistance decreases during the apnea episode when the neural control exists, which means that the neural control reduces the deformation of airway successfully and avoids the risk of OSAS.