MELANIA DIRCE OLIVEIRA MARQUES
Projetos de Pesquisa
Unidades Organizacionais
Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina - Médico
3 resultados
Resultados de Busca
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- Predicting epiglottic collapse in patients with obstructive sleep apnoea(2017) AZARBARZIN, Ali; MARQUES, Melania; SANDS, Scott A.; BEECK, Sara Op de; GENTA, Pedro R.; TARANTO-MONTEMURRO, Luigi; MELO, Camila M. de; MESSINEO, Ludovico; VANDERVEKEN, Olivier M.; WHITE, David P.; WELLMAN, AndrewObstructive sleep apnoea (OSA) is characterised by pharyngeal obstruction occurring at different sites. Endoscopic studies reveal that epiglottic collapse renders patients at higher risk of failed oral appliance therapy or accentuated collapse on continuous positive airway pressure. Diagnosing epiglottic collapse currently requires invasive studies (imaging and endoscopy). As an alternative, we propose that epiglottic collapse can be detected from the distinct airflow patterns it produces during sleep. 23 OSA patients underwent natural sleep endoscopy. 1232 breaths were scored as epiglottic/nonepiglottic collapse. Several flow characteristics were determined from the flow signal (recorded simultaneously with endoscopy) and used to build a predictive model to distinguish epiglottic from nonepiglottic collapse. Additionally, 10 OSA patients were studied to validate the pneumotachograph flow features using nasal pressure signals. Epiglottic collapse was characterised by a rapid fall(s) in the inspiratory flow, more variable inspiratory and expiratory flow and reduced tidal volume. The cross-validated accuracy was 84%. Predictive features obtained from pneumotachograph flow and nasal pressure were strongly correlated. This study demonstrates that epiglottic collapse can be identified from the airflow signal measured during a sleep study. This method may enable clinicians to use clinically collected data to characterise underlying physiology and improve treatment decisions.
- Stable Breathing in Patients With Obstructive Sleep Apnea Is Associated With Increased Effort but Not Lowered Metabolic Rate(2017) MELO, Camila M. de; TARANTO-MONTEMURRO, Luigi; BUTLER, James P.; WHITE, David P.; LORING, Stephen H.; AZARBARZIN, Ali; MARQUES, Melania; BERGER, Philip J.; WELLMAN, Andrew; SANDS, Scott A.Study objectives: In principle, if metabolic rate were to fall during sleep in a patient with obstructive sleep apnea (OSA), ventilatory requirements could be met without increased respiratory effort thereby favoring stable breathing. Indeed, most patients achieve periods of stable flow-limited breathing without respiratory events for periods during the night for reasons that are unclear. Thus, we tested the hypothesis that in patients with OSA, periods of stable breathing occur when metabolic rate (VO2) declines. Methods: Twelve OSA patients (apnea-hypopnea index > 15 events/h) completed overnight polysomnography including measurements of VO2 (using ventilation and intranasal PO2) and respiratory effort (esophageal pressure). Results: Contrary to our hypothesis, VO2 did not differ between stable and unstable breathing periods in non-REM stage 2 (208 +/- 20 vs. 213 +/- 18 mL/min), despite elevated respiratory effort during stable breathing (26 +/- 2 versus 23 +/- 2 cmH(2)O, p =.03). However, VO2 was lowered during deeper sleep (244 to 179 mL/min from non-REM stages 1 to 3, p =.04) in conjunction with more stable breathing. Further analysis revealed that airflow obstruction curtailed metabolism in both stable and unstable periods, since CPAP increased VO 2 by 14% in both cases (p =.02,.03, respectively). Patients whose VO2 fell most during sleep avoided an increase in PCO2 and respiratory effort. Conclusions: OSA patients typically convert from unstable to stable breathing without lowering metabolic rate. During sleep, OSA patients labor with increased respiratory effort but fail to satisfy metabolic demand even in the absence of overt respiratory events.
- Effect of 4-Aminopyridine on Genioglossus Muscle Activity during Sleep in Healthy Adults(2017) TARANTO-MONTEMURRO, Luigi; SANDS, Scott A.; AZARBARZIN, Ali; MARQUES, Melania; MELO, Camila M. de; EDWARDS, Bradley A.; ECKERT, Danny J.; MESSINEO, Ludovico; WHITE, David P.; WELLMAN, AndrewRationale: The reduction in upper airway muscle activity from wakefulness to sleep plays a key role in the development of obstructive sleep apnea. Potassium (K+) channels have been recently identified as the downstream mechanisms through which hypoglossal motoneuron membrane excitability is reduced both in non-rapid eye movement (NREM) sleep and REM sleep. In animal models, the administration of 4-aminopyridine (4-AP), a voltage-gated K+ channel blocker, increased genioglossus activity during wakefulness and across all sleep stages. Objectives: We tested the hypothesis that administration of a single dose of 4-AP 10 mg extended release would increase genioglossus activity (electromyography of the genioglossus muscle [EMG(GG)]) during wakefulness and sleep, and thereby decrease pharyngeal collapsibility. Methods: We performed a randomized controlled crossover proof-of- concept trial in 10 healthy participants. Participants received active treatment or placebo in randomized order 3 hours before bedtime in the physiology laboratory. Results: EMG(GG) during wakefulness and NREM sleep and upper airway collapsibility measured during NREM sleep were unchanged between placebo and 4-AP nights. Tonic but not phasic EMGGG during REM sleep was higher on the 4-AP night when measured as a percentage of maximal voluntary activation (median [interquartile range] 0.3 [0.5] on placebo vs. 0.8 [1.9] %(max) on 4 AP; P = 0.04), but not when measured in mu V or as a percentage of wakefulness value. Conclusions: A single dose of 4-AP 10 mg extended release showed only a small increase in tonic EMG(GG) during REM sleep in this group of healthy subjects. We speculate that a higher dose of 4-AP may further increase EMG(GG). However, given the potentially severe, dose-related adverse effects of this drug, including seizures, the administration of 4-AP does not appear to be an effective strategy to increase genioglossus activity during sleep in humans.