MELANIA DIRCE OLIVEIRA MARQUES
Projetos de Pesquisa
Unidades Organizacionais
Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina - Médico
2 resultados
Resultados de Busca
Agora exibindo 1 - 2 de 2
- Breath-holding as a means to estimate the loop gain contribution to obstructive sleep apnoea(2018) MESSINEO, Ludovico; TARANTO-MONTEMURRO, Luigi; AZARBARZIN, Ali; MARQUES, Melania D. Oliveira; CALIANESE, Nicole; WHITE, David P.; WELLMAN, Andrew; SANDS, Scott A.Increased ""loop gain"" of the ventilatory control system promotes obstructive sleep apnoea (OSA) in some patients and offers an avenue for more personalized treatment, yet diagnostic tools for directly measuring loop gain in the clinical setting are lacking. Here we test the hypothesis that elevated loop gain during sleep can be recognized using voluntary breath-hold manoeuvres during wakefulness. Twenty individuals (10 OSA, 10 controls) participated in a single overnight study with voluntary breath-holding manoeuvres performed during wakefulness. We assessed (1) maximal breath-hold duration, and (2) the ventilatory response to 20 s breath-holds. For comparison, gold standard loop gain values were obtained during non-rapid eye movement (non-REM) sleep using the ventilatory response to 20 s pulses of hypoxic-hypercapnic gas (6% CO2-14% O-2, mimicking apnoea). Continuous positive airway pressure (CPAP) was used to maintain airway patency during sleep. Additional measurements included gold standard loop gain measurement during wakefulness and steady-state loop gain measurement during sleep using CPAP dial-ups. Higher loop gain during sleep was associated with (1) a shorter maximal breath-hold duration (r(2) = 0.49, P < 0.001), and (2) a larger ventilatory response to 20 s breath-holds during wakefulness (second breath; r(2) = 0.50, P < 0.001); together these factors combine to predict high loop gain (receiver operating characteristic area-under-curve: 92%). Gold standard loop gain values were remarkably similar during wake and non-REM sleep. The results show that elevated loop gain during sleep can be identified using simple breath-holding manoeuvres performed during wakefulness. This may have implications for personalizing OSA treatment.
- 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.