Negative expiratory pressure test: A new method to detect upper airway flow limitation – a review

Abstract Introduction Upper Airway Resistance Syndrome (UARS) is suspected in individuals with excessive daytime sleepiness, fatigue, and sleep fragmentation associated with increased respiratory effort. UARS can negatively impact daytime function. Conventional polysomnography parameters do not demonstrate significant abnormalities in UARS patients but increase in RERAs and arousal index. Cyclic alternating pattern (CAP) is a periodic electroencephalogram activity of non-REM sleep that expresses a condition of sleep instability. The objective of the study was to compare CAP components between UARS patients and health individuals. Methods Fifteen subjects with UARS and 15 age- and sex- matched controls had their sleep study blinded analyzed. UARS criteria were the presence of sleepiness (Epworth Sleepiness Scale – ESS - ≥ 10) and/or fatigue (Modified Fatigue Impact Scale ≥ 38) associated with an apnea/hypopnea index (AHI) ≤ 5 and a respiratory disturbance index (RDI) > 5 events/hour of sleep, and/or flow limitation in more than 30% of total sleep time. Control group criteria were AHI < 5 events/hour, RDI ≤ 5 events/hour and < 30% of TST with flow limitation and ESS < 10, without sleep, clinical, neurological, or psychiatric disorder. CAP electroencephalogram of both groups was analyzed. Results We found higher CAP rate (p = 0.05) and CAP index in N1 stage (p < 0.001) and in N3 stage (p < 0.001) in UARS patients compared to control group. Considering only CAP phase A1 analysis, UARS patients presented higher CAP rate (p = 0.05) and CAP index in N1 stage (p < 0.001) as well as CAP index in N3 stage (p < 0.001) compared to control group. Considering only CAP phase A2 analysis, UARS patients also presented higher number of CAP in N1 stage (p = 0.05). There was no significant difference for CAP phase A3 between groups. Conclusion Although UARS is associated with high arousal index, we found increase in CAP phase A1 and A2, which do not include necessarily AASM arousals, suggesting not only sleep fragmentation but also sleep instability. Support (if any) Associação Fundo de Incentivo à Pesquisa (AFIP) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).

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Exploring the Abnormal Modulation of the Autonomic Systems during Nasal Flow Limitation in Upper Airway Resistance Syndrome by Hilbert–Huang Transform

Frontiers in Medicine ◽

10.3389/fmed.2017.00161 ◽

2017 ◽

Vol 4 ◽

Cited By ~ 3

Author(s):

Chen Lin ◽

Men-Tzung Lo ◽

Christian Guilleminault

Keyword(s):

Airway Resistance ◽

Upper Airway ◽

Flow Limitation ◽

Upper Airway Resistance Syndrome ◽

Hilbert Huang Transform ◽

Upper Airway Resistance ◽

Autonomic Systems ◽

Nasal Flow

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Test of the Starling resistor model in the human upper airway during sleep

Journal of Applied Physiology ◽

10.1152/japplphysiol.00259.2014 ◽

2014 ◽

Vol 117 (12) ◽

pp. 1478-1485 ◽

Cited By ~ 14

Author(s):

Andrew Wellman ◽

Pedro R. Genta ◽

Robert L. Owens ◽

Bradley A. Edwards ◽

Scott A. Sands ◽

...

Keyword(s):

Sleep Apnea ◽

Upper Airway ◽

Strongly Correlated ◽

Flow Limitation ◽

Single Model ◽

Multiple Sensors ◽

Pharyngeal Airway ◽

Wide Range ◽

Before And After ◽

Pressure Catheter

The human pharyngeal airway during sleep is conventionally modeled as a Starling resistor. However, inspiratory flow often decreases with increasing effort (negative effort dependence, NED) rather than remaining fixed as predicted by the Starling resistor model. In this study, we tested a major prediction of the Starling resistor model—that the resistance of the airway upstream from the site of collapse remains fixed during flow limitation. During flow limitation in 24 patients with sleep apnea, resistance at several points along the pharyngeal airway was measured using a pressure catheter with multiple sensors. Resistance between the nose and the site of collapse (the upstream segment) was measured before and after the onset of flow limitation to determine whether the upstream dimensions remained fixed (as predicted by the Starling resistor model) or narrowed (a violation of the Starling resistor model). The upstream resistance from early to mid inspiration increased considerably during flow limitation (by 35 ± 41 cmH2O·liter−1·s−1, P < 0.001). However, there was a wide range of variability between patients, and the increase in upstream resistance was strongly correlated with the amount of NED ( r = 0.75, P < 0.001). Therefore, patients with little NED exhibited little upstream narrowing (consistent with the Starling model), and patients with large NED exhibited large upstream narrowing (inconsistent with the Starling model). These findings support the idea that there is not a single model of pharyngeal collapse, but rather that different mechanisms may dominate in different patients. These differences could potentially be exploited for treatment selection.

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New method of computed tomography upper airway measurement and new computed tomography positioning technique in patients with sleep apnoea

Journal of Cranio-Maxillofacial Surgery ◽

10.1016/s1010-5182(96)80652-4 ◽

1996 ◽

Vol 24 ◽

pp. 143

Keyword(s):

Computed Tomography ◽

Upper Airway ◽

Sleep Apnoea ◽

New Method ◽

Positioning Technique

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A new method for pressure test analysis of a vertically fractured well producing commingled zones in bounded square reservoirs

Journal of Petroleum Science and Engineering ◽

10.1016/s0920-4105(97)00012-0 ◽

1997 ◽

Vol 18 (1-2) ◽

pp. 131-145

Author(s):

Mohammed E. Osman ◽

J.H. Abou-Kassem

Keyword(s):

New Method ◽

Test Analysis ◽

Pressure Test ◽

Fractured Well

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Collapsibility of the Upper Airway during Anesthesia with Isoflurane

Anesthesiology ◽

10.1097/00000542-200210000-00007 ◽

2002 ◽

Vol 97 (4) ◽

pp. 786-793 ◽

Cited By ~ 94

Author(s):

Peter R. Eastwood ◽

Irene Szollosi ◽

Peter R. Platt ◽

David R. Hillman

Keyword(s):

Lung Volume ◽

Critical Pressure ◽

Upper Airway ◽

Esophageal Pressure ◽

Inspiratory Flow ◽

Flow Limitation ◽

Anesthetic Depth ◽

Volume Collapse ◽

End Tidal ◽

Spontaneously Breathing

Background The unprotected upper airway tends to obstruct during general anesthesia, yet its mechanical properties have not been studied in detail during this condition. Methods To study its collapsibility, pressure-flow relationships of the upper airway were obtained at three levels of anesthesia (end-tidal isoflurane = 1.2%, 0.8%, and 0.4%) in 16 subjects while supine and spontaneously breathing on nasal continuous positive airway pressure. At each level of anesthesia, mask pressure was transiently reduced from a pressure sufficient to abolish inspiratory flow limitation (11.8 +/- 2.7 cm H(2)O) to pressures resulting in variable degrees of flow limitation. The relation between mask pressure and maximal inspiratory flow was determined, and the critical pressure at which the airway occluded was recorded. The site of collapse was determined from simultaneous measurements of nasopharyngeal, oropharyngeal, and hypopharyngeal and esophageal pressures. Results The airway remained hypotonic (minimal or absent intramuscular genioglossus electromyogram activity) throughout each study. During flow-limited breaths, inspiratory flow decreased linearly with decreasing mask pressure (r(2) = 0.86 +/- 0.17), consistent with Starling resistor behavior. At end-tidal isoflurane of 1.2%, critical pressure was 1.1 +/- 3.5 cm H O; at 0.4% it decreased to -0.2 +/- 3.6 cm H(2)O ( < 0.05), indicating decreased airway collapsibility. This decrease was associated with a decrease in end-expiratory esophageal pressure of 0.6 +/- 0.9 cm H(2)O ( < 0.05), suggesting an increased lung volume. Collapse occurred in the retropalatal region in 14 subjects and in the retrolingual region in 2 subjects, and did not change with anesthetic depth. Conclusions Isoflurane anesthesia is associated with decreased muscle activity and increased collapsibility of the upper airway. In this state it adopts the behavior of a Starling resistor. The decreased collapsibility observed with decreasing anesthetic depth was not a consequence of neuromuscular activity, which was unchanged. Rather, it may be related to increased lung volume and its effect on airway wall longitudinal tension. The predominant site of collapse is the soft palate.

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A new method of tubeless anaesthesia for upper airway laser surgery

Lasers in Medical Science ◽

10.1007/bf02594186 ◽

1994 ◽

Vol 9 (1) ◽

pp. 55-58 ◽

Cited By ~ 4

Author(s):

M. G. Dilkes ◽

C. Broomhead ◽

P. McKelvie ◽

P. S. Monks

Keyword(s):

Laser Surgery ◽

Upper Airway ◽

New Method

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Assessment of Changes in Upper Airway Obstruction by Automatic Identification of Inspiratory Flow Limitation During Sleep

IEEE Transactions on Biomedical Engineering ◽

10.1109/tbme.2009.2023079 ◽

2009 ◽

Vol 56 (8) ◽

pp. 2006-2015 ◽

Cited By ~ 10

Author(s):

Christian Morgenstern ◽

Matthias Schwaibold ◽

Winfried J. Randerath ◽

Armin Bolz ◽

Raimon Jane

Keyword(s):

Airway Obstruction ◽

Upper Airway ◽

Inspiratory Flow ◽

Upper Airway Obstruction ◽

Automatic Identification ◽

Flow Limitation

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Collapsibility of the Upper Airway at Different Concentrations of Propofol Anesthesia

Anesthesiology ◽

10.1097/00000542-200509000-00007 ◽

2005 ◽

Vol 103 (3) ◽

pp. 470-477 ◽

Cited By ~ 179

Author(s):

Peter R. Eastwood ◽

Peter R. Platt ◽

Kelly Shepherd ◽

Kathy Maddison ◽

David R. Hillman

Keyword(s):

Upper Airway ◽

Inspiratory Flow ◽

Electromyographic Activity ◽

Flow Limitation ◽

Genioglossus Muscle ◽

Airway Collapsibility ◽

Effect Site Concentration ◽

Intramuscular Electrodes ◽

Upper Airway Collapsibility ◽

Spontaneously Breathing

Background This study investigated the effect of varying concentrations of propofol on upper airway collapsibility and the mechanisms responsible for it. Methods Upper airway collapsibility was determined from pressure-flow relations at three concentrations of propofol anesthesia (effect site concentration = 2.5, 4.0, and 6.0 mug/ml) in 12 subjects spontaneously breathing on continuous positive airway pressure. At each level of anesthesia, mask pressure was transiently reduced from a pressure sufficient to abolish inspiratory flow limitation (maintenance pressure = 12 +/- 1 cm H2O) to pressures resulting in variable degrees of flow limitation. The relation between mask pressure and maximal inspiratory flow was determined, and the critical pressure at which the airway occluded was recorded. Electromyographic activity of the genioglossus muscle (EMGgg) was obtained via intramuscular electrodes in 8 subjects. Results With increasing depth of anesthesia, (1) critical closing pressure progressively increased (-0.3 +/- 3.5, 0.5 +/- 3.7, and 1.4 +/- 3.5 cm H2O at propofol concentrations of 2.5, 4.0, and 6.0 microg/ml respectively; P < 0.05 between each level), indicating a more collapsible upper airway; (2) inspiratory flow at the maintenance pressure significantly decreased; and (3) respiration-related phasic changes in EMGgg at the maintenance pressure decreased from 7.3 +/- 9.9% of maximum at 2.5 microg/ml to 0.8 +/- 0.5% of maximum at 6.0 microg/ml, whereas tonic EMGgg was unchanged. Relative to the levels of phasic and tonic EMGgg at the maintenance pressure immediately before a decrease in mask pressure, tonic activity tended to increase over the course of five flow-limited breaths at a propofol concentration of 2.5 microg/ml but not at propofol concentrations of 4.0 and 6.0 microg/ml, whereas phasic EMGgg was unchanged. Conclusions Increasing depth of propofol anesthesia is associated with increased collapsibility of the upper airway. This was associated with profound inhibition of genioglossus muscle activity. This dose-related inhibition seems to be the combined result of depression of central respiratory output to upper airway dilator muscles and of upper airway reflexes.

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