Accuracy of Breath-by-Breath Analysis of Flow-Volume Loop in Identifying Sleep-Induced Flow-Limited Breathing Cycles in Sleep Apnoea-Hypopnoea Syndrome

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.

Download Full-text

Dynamic mechanisms determine functional residual capacity in mice, Mus musculus

Journal of Applied Physiology ◽

10.1152/jappl.1979.46.5.867 ◽

1979 ◽

Vol 46 (5) ◽

pp. 867-871 ◽

Cited By ~ 82

Author(s):

A. Vinegar ◽

E. E. Sinnett ◽

D. E. Leith

Keyword(s):

Tidal Volume ◽

Functional Residual Capacity ◽

Flow Volume ◽

Linear Portion ◽

Volume Curve ◽

Flow Volume Curve ◽

Residual Capacity ◽

Expiratory Flow ◽

The Difference ◽

Pentobarbital Sodium Anesthesia

Awake mice (22.6--32.6 g) were anesthetized intravenously during head-out body plethysmography. One minute after pentobarbital sodium anesthesia, tidal volume had fallen from 0.28 +/- 0.04 to 0.14 +/- 0.02 ml and frequency from 181 +/- 20 to 142 +/- 8. Functional residual capacity (FRC) decreased by 0.10 +/- 0.02 ml. Expiratory flow-volume curves were linear, highly repeatable, and submaximal over substantial portions of expiration in awake and anesthetized mice; and expiration was interrupted at substantial flows that abruptly fell to and crossed zero as inspiration interrupted relaxed expiration. FRC is maintained at a higher level in awake mice due to a higher tidal volume and frequency coupled with expiratory braking (persistent inspiratory muscle activity or increased glottal resistance). In anesthetized mice, the absence of braking, coupled with reductions in tidal volume and frequency and a prolonged expiratory period, leads to FRCs that approach relaxation volume (Vr). An equation in derived to express the difference between FRC and Vr in terms of the portion of tidal volume expired without braking, the slope of the linear portion of the expiratory flow-volume curve expressed as V/V, the time fraction of one respiratory cycle spent in unbraked expiration, and respiratory frequency.

Download Full-text

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

SLEEP ◽

10.1093/sleepj/zsx050.470 ◽

2017 ◽

Vol 40 (suppl_1) ◽

pp. A176-A176

Author(s):

NM Skjodt ◽

S Sarraf ◽

RS Platt

Keyword(s):

Sleep Apnoea ◽

Inspiratory Flow ◽

Flow Limitation

Download Full-text

Bronchodilatation and the Inspiratory Flow Volume Curve

CHEST Journal ◽

10.1378/chest.110.5.1226 ◽

1996 ◽

Vol 110 (5) ◽

pp. 1226-1228 ◽

Cited By ~ 5

Author(s):

Raju Reddy ◽

Timothy Cook ◽

Michael F. Tenholder

Keyword(s):

Inspiratory Flow ◽

Flow Volume ◽

Volume Curve ◽

Flow Volume Curve

Download Full-text

P135 Maximum inspiratory flow measured directly with an inspiratory flow metre compared with measurements from flow volume loop traces

Thorax ◽

10.1136/thoraxjnl-2011-201054c.135 ◽

2011 ◽

Vol 66 (Suppl 4) ◽

pp. A121-A122

Author(s):

M. C. P. Apps ◽

M. Skipper ◽

J. Skipper ◽

S. Basford ◽

V. Bryant ◽

...

Keyword(s):

Inspiratory Flow ◽

Flow Volume ◽

Flow Volume Loop

Download Full-text

Evaluation of Major Airway Lesions Using the Flow-Volume Loop

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348947508400514 ◽

1975 ◽

Vol 84 (5) ◽

pp. 635-642 ◽

Cited By ~ 14

Author(s):

Robert E. Hyatt

Keyword(s):

Vital Capacity ◽

Inspiratory Flow ◽

Flow Volume ◽

Flow Volume Loop ◽

Expiratory Flow

The flow-volume (FV) loop is another way of representing spirometric data from combinations of forced expiratory and forced inspiratory vital capacity breaths. The FV loop is of use in identifying, and often localizing, lesions of the larynx and the trachea (down to the carina). Three general patterns have been recognized. When the lesion behaves in a fixed fashion (as might occur with an artificial orifice), maximal expiratory and inspiratory flows are almost equally compromised. This results in a rectangular FV loop, irrespective of whether the lesion is located intrathoracically or extrathoracically. When the lesion behaves in a variable fashion, two distinct patterns are seen, depending on the location of the lesion (intrathoracic or extrathoracic). The variable lesion acts as a fixed lesion during one phase of forced respiration only. The extrathoracic variable lesion results in a predominant reduction in forced inspiratory flow, with little effect on expiratory flow, whereas the intrathoracic variable lesion produces a characteristic reduction in expiratory flow. These patterns reflect the transmural forces existing at the site of the lesion.

Download Full-text

Abnormalities in the flow-volume loop in obstructive sleep apnoea sitting and supine.

Thorax ◽

10.1136/thx.39.10.775 ◽

1984 ◽

Vol 39 (10) ◽

pp. 775-779 ◽

Cited By ~ 19

Author(s):

E T Shore ◽

R P Millman

Keyword(s):

Obstructive Sleep Apnoea ◽

Sleep Apnoea ◽

Flow Volume ◽

Flow Volume Loop ◽

Obstructive Sleep

Download Full-text

Heliox administration in anesthetized rabbits with spontaneous inspiratory flow limitation

Journal of Applied Physiology ◽

10.1152/japplphysiol.00830.2020 ◽

2021 ◽

Author(s):

Edgardo Giacomo D'Angelo ◽

Matteo M. Pecchiari ◽

François Bellemare ◽

Gabriele Cevenini ◽

Paolo Barbini

Keyword(s):

Inspiratory Flow ◽

Flow Limitation ◽

Upper Airways ◽

Relative Contribution ◽

Volume Curve ◽

Pressure Volume Curve ◽

Tracheal Pressure ◽

Airway Opening ◽

Laminar And Turbulent Flow ◽

Geometrical Factors

We investigated the effects of heliox administration (80% Helium in O2) on tidal inspiratory flow limitation (tIFL) occurring in supine anesthetized spontaneously breathing rabbits, regarded as an animal model of obstructive apnea-hypopnea syndrome. 22 rabbits were instrumented to record oro-nasal mask flow, airway opening, tracheal and esophageal pressures and diaphragm and genioglossus electromyographic activities while breathing either room air or heliox, and, in 12 rabbits, also during the application of continuous positive airway pressure (CPAP; 6 cmH2O). For the group, heliox increased peak inspiratory flow, ventilation (18±11%), peak inspiratory tracheal and dynamic transpulmonary pressures, but in no animal eliminated tIFL, as instead CPAP did in all. Muscle activities were unaffected by heliox. In the presence of IFL the increase in flow with heliox (ΔV̇IFL) varied markedly among rabbits (2 to 49%), allowing the distinction between responders and non-responders. None of the baseline variables discriminated responders and non-responders. However, fitting the Rohrer equation (R=K1+K2V̇) to the tracheal pressure-flow relationship over the first 0.1s of inspiration while breathing air allowed such discrimination on the basis of larger K2 in responders (0.005±.002 vs 0.002±.001 cmH2O·s2·ml-2; p<0.001), suggesting a corresponding difference in the relative contribution of laminar and turbulent flow. The differences in ΔV̇IFL between responders and non-responders were simulated by modeling the collapsible segment of the upper airways as a non-linear resistor and varying its pressure-volume curve, length and diameter, thus showing the importance of mechanical and geometrical factors in determining the response to heliox in the presence of tIFL.

Download Full-text

Inspiratory Flow Volume Loop Flattening to Predict Exercise-Induced Vocal Cord Dysfunction with Eucapnic Voluntary Hyperventilation

10.1164/ajrccm-conference.2020.201.1_meetingabstracts.a3241 ◽

2020 ◽

Author(s):

B. Temte ◽

J. Wells ◽

J.G. Mastronarde ◽

R. Wobig ◽

C. Clark ◽

...

Keyword(s):

Vocal Cord ◽

Inspiratory Flow ◽

Vocal Cord Dysfunction ◽

Flow Volume ◽

Voluntary Hyperventilation ◽

Flow Volume Loop ◽

Eucapnic Voluntary Hyperventilation ◽

Exercise Induced

Download Full-text

Novel method for measuring effects of gas compression on expiratory flow

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00573.2003 ◽

2004 ◽

Vol 287 (2) ◽

pp. R479-R484 ◽

Cited By ~ 8

Author(s):

Amir Sharafkhaneh ◽

Todd M. Officer ◽

Sheila Goodnight-White ◽

Joseph R. Rodarte ◽

Aladin M. Boriek

Keyword(s):

Normal Subjects ◽

Chronic Obstructive ◽

Flow Limitation ◽

Flow Volume ◽

Expiratory Flow Limitation ◽

Obstructive Pulmonary Disease ◽

Flow Volume Loop ◽

Gas Compression ◽

Novel Method ◽

Expiratory Flow

During forced vital capacity maneuvers in subjects with expiratory flow limitation, lung volume decreases during expiration both by air flowing out of the lung (i.e., exhaled volume) and by compression of gas within the thorax. As a result, a flow-volume loop generated by using exhaled volume is not representative of the actual flow-volume relationship. We present a novel method to take into account the effects of gas compression on flow and volume in the first second of a forced expiratory maneuver (FEV1). In addition to oral and esophageal pressures, we measured flow and volume simultaneously using a volume-displacement plethysmograph and a pneumotachograph in normal subjects and patients with expiratory flow limitation. Expiratory flow vs. plethysmograph volume signals was used to generate a flow-volume loop. Specialized software was developed to estimate FEV1 corrected for gas compression (NFEV1). We measured reproducibility of NFEV1 in repeated maneuvers within the same session and over a 6-mo interval in patients with chronic obstructive pulmonary disease. Our results demonstrate that NFEV1 significantly correlated with FEV1, peak expiratory flow, lung expiratory resistance, and total lung capacity. During intrasession, maneuvers with the highest and lowest FEV1 showed significant statistical difference in mean FEV1 ( P < 0.005), whereas NFEV1 from the same maneuvers were not significantly different from each other ( P > 0.05). Furthermore, variability of NFEV1 measurements over 6 mo was <5%. We concluded that our method reliably measures the effect of gas compression on expiratory flow.

Download Full-text