0471 INSPIRATORY FLOW LIMITATION IN A LARGE AMBULATORY COHORT OF SUSPECTED SLEEP APNOEA PATIENTS

1. Inspiratory flow limitation is involved in the pathophysiology of sleep-related breathing disorders. Since the definition of flow-limited cycle is based on a dissociation between flow and respiratory efforts, identification of inspiratory flow limitation requires upper airway or intrathoracic pressure measurements. We examined the accuracy of the analysis of the flow—volume loop of a tidal breath in identifying inspiratory flow limitation during sleep in ten patients with a sleep apnoea—hypopnoea syndrome. 2. Measurements were taken during continuous positive airway pressure trials. After data acquisition, the presence of inspiratory flow limitation was identified by the presence of an inspiratory plateau or decrease in inspiratory flow independently of the increase in inspiratory efforts. The flow—volume loop was reconstructed for each breathing cycle by plotting the instantaneous flow and the tidal volume. The instantaneous inspiratory and expiratory flows were measured at 50% of the respective portion of the tidal volume, and a breath-by-breath analysis of the midtidal volume—flow ratio (inspiratory/expiratory ratio) was obtained. The analysis of the flow—volume loop was compared with standard inspiratory flow limitation criteria using different values of the inspiratory/expiratory ratio threshold, below which breathing cycles were classified as flow-limited. With a lower limit of the normal inspiratory/expiratory ratio threshold of 0.97, the sensitivity and specificity of the method were both 76%. In each subject, the proportion of breathing cycles identified as flow-limited according to the inspiratory/expiratory ratio progressively decreased with an increasing positive pressure level. 3. We conclude that analysis of the flow—volume curve is accurate in identifying most of the inspiratory flow limitation breathings in sleep apnoea—hypopnoea syndrome.

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S24 A comparison of pulse transit time between subjects with obstructive sleep apnoea syndrome, nocturnal inspiratory flow limitation and the absence of significant sleep disordered breathing

Thorax ◽

10.1136/thoraxjnl-2016-209333.30 ◽

2016 ◽

Vol 71 (Suppl 3) ◽

pp. A15.2-A16

Author(s):

B Chakrabarti ◽

S Emegbo ◽

S Craig ◽

N Duffy ◽

JF O’Reilly

Keyword(s):

Transit Time ◽

Obstructive Sleep Apnoea ◽

Sleep Disordered Breathing ◽

Pulse Transit Time ◽

Sleep Apnoea ◽

Inspiratory Flow ◽

Obstructive Sleep Apnoea Syndrome ◽

Flow Limitation ◽

Sleep Apnoea Syndrome ◽

Obstructive Sleep

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Detection of inspiratory flow limitation during sleep by computer assisted respiratory inductive plethysmography

European Respiratory Journal ◽

10.1034/j.1399-3003.2000.15.24.x ◽

2000 ◽

Vol 15 (3) ◽

pp. 570 ◽

Cited By ~ 36

Author(s):

V. Kaplan ◽

J.N. Zhang ◽

E.w Russi ◽

K.e Bloch

Keyword(s):

Inspiratory Flow ◽

Computer Assisted ◽

Flow Limitation ◽

Respiratory Inductive Plethysmography ◽

Inductive Plethysmography

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Inspiratory flow limitation in children with bronchopulmonary dysplasia

Pediatric Pulmonology ◽

10.1002/(sici)1099-0496(199809)26:3<167::aid-ppul3>3.0.co;2-i ◽

1998 ◽

Vol 26 (3) ◽

pp. 167-172 ◽

Cited By ~ 6

Author(s):

Hossein Sadeghi ◽

Diana B. Lowenthal ◽

Allen J. Dozor

Keyword(s):

Bronchopulmonary Dysplasia ◽

Inspiratory Flow ◽

Flow Limitation

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Palatal prolapse as a signature of expiratory flow limitation and inspiratory palatal collapse in patients with obstructive sleep apnoea

European Respiratory Journal ◽

10.1183/13993003.01419-2017 ◽

2018 ◽

Vol 51 (2) ◽

pp. 1701419 ◽

Cited By ~ 13

Author(s):

Ali Azarbarzin ◽

Scott A. Sands ◽

Melania Marques ◽

Pedro R. Genta ◽

Luigi Taranto-Montemurro ◽

...

Keyword(s):

Obstructive Sleep Apnoea ◽

Sleep Apnoea ◽

Flow Limitation ◽

Sleep Endoscopy ◽

Expiratory Flow Limitation ◽

Patient Level ◽

Obstructive Sleep ◽

Expiratory Flow ◽

Nasal Pressure ◽

Lateral Walls

In some individuals with obstructive sleep apnoea (OSA), the palate prolapses into the velopharynx during expiration, limiting airflow through the nose or shunting it out of the mouth. We hypothesised that this phenomenon causes expiratory flow limitation (EFL) and is associated with inspiratory “isolated” palatal collapse. We also wanted to provide a robust noninvasive means to identify this mechanism of obstruction.Using natural sleep endoscopy, 1211 breaths from 22 OSA patients were scored as having or not having palatal prolapse. The patient-level site of collapse (tongue-related, isolated palate, pharyngeal lateral walls and epiglottis) was also characterised. EFL was quantified using expiratory resistance at maximal epiglottic pressure. A noninvasive EFL index (EFLI) was developed to detect the presence of palatal prolapse and EFL using the flow signal alone. In addition, the validity of using nasal pressure was assessed.A cut-off value of EFLI >0.8 detected the presence of palatal prolapse and EFL with an accuracy of >95% and 82%, respectively. The proportion of breaths with palatal prolapse predicted isolated inspiratory palatal collapse with 90% accuracy.This study demonstrates that expiratory palatal prolapse can be quantified noninvasively, is associated with EFL and predicts the presence of inspiratory isolated palatal collapse.

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