THE COMPARISON OF CONFIGURATION, DEGREE AND SITES OF OBSTRUCTION IN PATIENTS WITH SLEEP DISORDERED BREATHING: EXAMINATION USING DRUG-INDUCED SLEEP ENDOSCOPY, MUELLER MANEUVER AND POLYSOMNOGRAPHY

Objective: The purpose of this study is to evaluate the location, configuration, and degree of differences in upper airway obstruction between the Mueller Maneuver (MM) and Drug-induced sleep endoscopy (DISE), thus acquiring a better diagnostic value for SDB patients. Methods: A cross-sectional and analytical descriptive study using retrospective secondary data to evaluate the location, configuration and degree of upper airway obstruction in SDB subjects using the Mueller Maneuver and DISE. Polysomnography (PSG) type 2 was used to determine the SDB degree. Results: Subjects with SDB non-Obstructive sleep apnea (OSA) and OSA show a multilevel obstruction with a different location and configuration due to the various risk factors, such as nasal congestion, laryngopharyngeal reflux, obesity and menopause. Conclusion: Statistical differences in upper airway obstruction configuration between MM and DISE were found in the level of the velum (p=0,036), oropharynx (p<0,001) and epiglottis (p=0,036) and were also found in the obstruction degree of the velum, oropharynx, tongue base and epiglottis with p=0,002; p<0,001; p<0,001 and p<0,001. No statistical difference was found on the lowest oxygen saturation between PSG and DISE (p=0,055).

Mechanisms of inspiration that modulate cardiovascular control: the other side of breathing

The objective of this minireview is to describe the physiology and potential clinical benefits derived from inspiration. Recent animal and clinical studies demonstrate that one of the body’s natural mechanisms associated with inspiration is to harness the respiratory pump to enhance circulation to vital organs. There is evidence that large reductions in intrathoracic pressure (>20 cmH2O) caused by some inspiration maneuvers (e.g., Mueller maneuver) or pathophysiology (e.g., heart failure, chronic obstructive lung disease) can result in adverse hemodynamic effects. However, the respiratory pump can improve cardiovascular functions when a “sweet spot” for generation of negative intrathoracic pressure during inspiration can be maintained at or less than 10 cmH2O below normal inspiration. These beneficial physiological effects include greater cardiac filling and output, lower intracranial pressure, cardiac baroreflex resetting, greater cerebral blood flow oscillatory patterns, increased vascular pressure gradients, and promoting sustained feedback between sympathetic nerve activity and arterial pressure. In addition to promoting gas exchange, data obtained from numerous animal and human experiments have provided new insights into “the other side of breathing”: the modulation of circulation by reduced intrathoracic pressure generated during inspiration. The translation of these physiological relationships form the basis for the development and application of technologies designed to optimize the intrathoracic pump for treatment of clinical conditions associated with hypovolemia including cardiac arrest, orthostatic hypotension, hemorrhagic shock, and traumatic brain injury. Harnessing these fundamental mechanisms that control cardiopulmonary physiology provides opportunities to use inspiration as a potential tool to help treat significant and often life-threatening circulatory disorders.

Effect of simulated obstructive hypopnea and apnea on thoracic aortic wall transmural pressures

Preliminary evidence supports an association between obstructive sleep apnea (OSA) and thoracic aortic dilatation, although potential causative mechanisms are incompletely understood; these may include an increase in aortic wall transmural pressures, induced by obstructive apneas and hypopneas. In patients undergoing cardiac catheterization, mean blood pressure (MBP) in the thoracic aorta and esophageal pressure was simultaneously recorded by an indwelling aortic pigtail catheter and a balloon-tipped esophageal catheter in randomized order during: normal breathing, simulated obstructive hypopnea (inspiration through a threshold load), simulated obstructive apnea (Mueller maneuver), and end-expiratory central apnea. Aortic transmural pressure (aortic MBP minus esophageal pressure) was calculated. Ten patients with a median age (range) of 64 (46–75) yr were studied. Inspiration through a threshold load, Mueller maneuver, and end-expiratory central apnea was successfully performed and recorded in 10, 7, and 9 patients, respectively. The difference between aortic MBP and esophageal pressure (and thus the extra aortic dilatory force) was median (quartiles) +9.3 (5.4, 18.6) mmHg, P = 0.02 during inspiration through a threshold load, +16.3 (12.8, 19.4) mmHg, P = 0.02 during the Mueller maneuver, and +0.4 (−4.5, 4.8) mmHg, P = 0.80 during end-expiratory central apnea. Simulated obstructive apnea and hypopnea increase aortic wall dilatory transmural pressures because intra-aortic pressures fall less than esophageal pressures. Thus OSA may mechanically promote thoracic aortic dilatation and should be further investigated as a risk factor for the development or accelerated progression of thoracic aortic aneurysms.

Cardiac and vascular responses to thigh cuffs and respiratory maneuvers on crewmembers of the International Space Station

Background: the transition to microgravity eliminates the hydrostatic gradients in the vascular system. The resulting fluid redistribution commonly manifests as facial edema, engorgement of the external neck veins, nasal congestion, and headache. This experiment examined the responses to modified Valsalva and Mueller maneuvers measured by cardiac and vascular ultrasound (ECHO) in a baseline steady state and under the influence of thigh occlusion cuffs available as a countermeasure device (Braslet cuffs). Methods: nine International Space Station crewmember subjects (expeditions 16–20) were examined in 15 experiment sessions 101 ± 46 days after launch (mean ± SD; 33–185). Twenty-seven cardiac and vascular parameters were obtained with/without respiratory maneuvers before and after tightening of the Braslet cuffs (162 parameter states/session). Quality of cardiac and vascular ultrasound examinations was assured through remote monitoring and guidance by investigators from the NASA Telescience Center in Houston, TX, and the Mission Control Center in Korolyov, Moscow region, Russia. Results: 14 of 81 conditions (27 parameters measured at baseline, Valsalva, and Mueller maneuver) were significantly different when the Braslet was applied. Seven of 27 parameters were found to respond differently to respiratory maneuvers depending on the presence or absence of thigh compression. Conclusions: acute application of Braslet occlusion cuffs causes lower extremity fluid sequestration and exerts commensurate measurable effects on cardiac performance in microgravity. Ultrasound techniques to measure the hemodynamic effects of thigh cuffs in combination with respiratory maneuvers may serve as an effective tool in determining the volume status of a cardiac or hemodynamically compromised patient at the “microgravity bedside.”