Control of the expiratory flow in a lung model and in healthy volunteers with an adjustable flow regulator: a combined bench and randomized crossover study

Abstract Background Pursed-lips breathing (PLB) is a technique to attenuate small airway collapse by regulating the expiratory flow. During mandatory ventilation, flow-controlled expiration (FLEX), which mimics the expiratory flow course of PLB utilizing a digital system for measurement and control, was shown to exert lung protective effects. However, PLB requires a patient’s participation and coordinated muscular effort and FLEX requires a complex technical setup. Here, we present an adjustable flow regulator to mimic PLB and FLEX, respectively, without the need of a patient’s participation, or a complex technical device. Methods Our study consisted of two parts: First, in a lung model which was ventilated with standard settings (tidal volume 500 ml, respiratory rate 12 min−1, positive end-expiratory pressure (PEEP) 5 cmH2O), the possible reduction of the maximal expiratory flow by utilizing the flow regulator was assessed. Second, with spontaneously breathing healthy volunteers, the short-term effects of medium and strong expiratory flow reduction on airway pressure, the change of end-expiratory lung volume (EELV), and breathing discomfort was investigated. Results In the lung model experiments, expiratory flow could be reduced from − 899 ± 9 ml·s−1 down to − 328 ± 25 ml·s−1. Thereby, inspiratory variables and PEEP were unaffected. In the volunteers, the maximal expiratory flow of − 574 ± 131 ml·s−1 under baseline conditions was reduced to − 395 ± 71 ml·s−1 for medium flow regulation and to − 266 ± 58 ml·s−1 for strong flow regulation, respectively (p < 0.001). Accordingly, mean airway pressure increased from 0.6 ± 0.1 cmH2O to 2.9 ± 0.4 cmH2O with medium flow regulation and to 5.4 ± 2.4 cmH2O with strong flow regulation, respectively (p < 0.001). The EELV increased from baseline by 31 ± 458 ml for medium flow regulation and 320 ± 681 ml for strong flow regulation (p = 0.033). The participants rated breathing with the flow regulator as moderately uncomfortable, but none rated breathing with the flow regulator as intolerable. Conclusions The flow regulator represents an adjustable device for application of a self-regulated expiratory resistive load, representing an alternative for PLB and FLEX. Future applications in spontaneously breathing patients and patients with mandatory ventilation alike may reveal potential benefits. Trial registration: DRKS00015296, registered on 20th August, 2018; URL: https://www.drks.de/drks_web/setLocale_EN.do.

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Expiratory flow pattern and respiratory mechanics

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y87-180 ◽

1987 ◽

Vol 65 (6) ◽

pp. 1142-1145 ◽

Cited By ~ 2

Author(s):

Jacopo P. Mortola ◽

Anne Marie Lauzon ◽

Brian Mott

Keyword(s):

Flow Pattern ◽

Respiratory System ◽

Airway Pressure ◽

Work Of Breathing ◽

Vocal Folds ◽

Resistive Load ◽

Adult Rats ◽

Expiratory Flow ◽

And Control ◽

And Diffusion

During resting breathing, expiration is characterized by the narrowing of the vocal folds which, by increasing the expiratory resistance, raises mean lung volume and airway pressure. This is even more pronounced in the neonatal period, during which expirations with short complete airway closure are commonly occurring. We asked to which extent differences in expiratory flow pattern may modify the inspiratory impedance of the respiratory system. To this aim, newborn puppies, piglets, and adult rats were anesthetized, paralyzed, and ventilated with different expiratory patterns, (a) no expiratory load, (b) expiratory resistive load, and (c) end-inspiratory pause. The stroke volume of the ventilator and inspiratory and expiratory times were maintained constant, and the loads were adjusted in such a way that inflation always started from the resting volume of the respiratory system. After 1 min of each ventilatory pattern, mean inspiratory impedance and compliance of lung and respiratory system were measured. The values were unchanged or minimally altered by changing the type of ventilation. We conclude that the expiratory laryngeal loading is not primarily aimed to decrease the work of breathing. It is conceivable that the expiratory pattern is oriented to increase and control mean airway pressure in the regulation of pulmonary fluid reabsorption, distribution of ventilation, and diffusion of gases.

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Reference value for expiratory time constant calculated from the maximal expiratory flow-volume curve

BMC Pulmonary Medicine ◽

10.1186/s12890-019-0976-6 ◽

2019 ◽

Vol 19 (1) ◽

Author(s):

Takamitsu Ikeda ◽

Yasuhiro Yamauchi ◽

Kanji Uchida ◽

Koji Oba ◽

Takahide Nagase ◽

...

Keyword(s):

Airway Obstruction ◽

Time Constant ◽

Characteristic Curve ◽

Reference Value ◽

Flow Volume ◽

Expiratory Time ◽

Maximal Expiratory Flow ◽

Volume Curve ◽

Expiratory Flow ◽

Spontaneously Breathing

Abstract Background The expiratory time constant (RCEXP), which is defined as the product of airway resistance and lung compliance, enable us to assess the mechanical properties of the respiratory system in mechanically ventilated patients. Although RCEXP could also be applied to spontaneously breathing patients, little is known about RCEXP calculated from the maximal expiratory flow-volume (MEFV) curve. The aim of our study was to determine the reference value for RCEXP, as well as to investigate the association between RCEXP and other respiratory function parameters, including the forced expiratory volume in 1 s (FEV1)/ forced vital capacity (FVC) ratio, maximal mid-expiratory flow rate (MMF), maximal expiratory flow at 50 and 25% of FVC (MEF50 and MEF25, respectively), ratio of MEF50 to MEF25 (MEF50/MEF25). Methods Spirometric parameters were extracted from the records of patients aged 15 years or older who underwent pulmonary function testing as a routine preoperative examination before non-cardiac surgery at the University of Tokyo Hospital. RCEXP was calculated in each patient from the slope of the descending limb of the MEFV curve using two points corresponding to MEF50 and MEF25. Airway obstruction was defined as an FEV1/FVC and FEV1 below the statistically lower limit of normal. Results We retrospectively analyzed 777 spirometry records, and 62 patients were deemed to have airway obstruction according to Japanese spirometric reference values. The cut-off value for RCEXP was 0.601 s with an area under the receiver operating characteristic curve of 0.934 (95% confidence interval = 0.898–0.970). RCEXP was strongly associated with FEV1/FVC, and was moderately associated with MMF and MEF50. However, RCEXP was less associated with MEF25 and MEF50/MEF25. Conclusions Our findings suggest that an RCEXP of longer than approximately 0.6 s can be linked to the presence of airway obstruction. Application of the concept of RCEXP to spontaneously breathing subjects was feasible, using our simple calculation method.

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Anaesthetic and respiratory equipment. Peak expiratory flow meters for the assessment of pulmonary function in spontaneously breathing humans

10.3403/30292012 ◽

2015 ◽

Keyword(s):

Pulmonary Function ◽

Peak Expiratory Flow ◽

Flow Meters ◽

Expiratory Flow ◽

Spontaneously Breathing

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Evaluation of a Humidified Nasal High-Flow Oxygen System, Using Oxygraphy, Capnography and Measurement of Upper Airway Pressures

Anaesthesia and Intensive Care ◽

10.1177/0310057x1103900620 ◽

2011 ◽

Vol 39 (6) ◽

pp. 1103-1110 ◽

Cited By ~ 121

Author(s):

J. E. Ritchie ◽

A. B. Williams ◽

C. Gerard ◽

H. Hockey

Keyword(s):

Healthy Volunteers ◽

Airway Pressure ◽

Gas Flow ◽

Air Entrainment ◽

High Flow ◽

Positive Pressure ◽

Mean Airway Pressure ◽

Flow Rates ◽

Oxygen Fraction ◽

Airway Pressures

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO2, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH2O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.

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Pattern and mechanism of airway response to hypocapnia in normal subjects

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.1.8 ◽

1979 ◽

Vol 47 (1) ◽

pp. 8-12 ◽

Cited By ~ 35

Author(s):

C. F. O'Cain ◽

M. J. Hensley ◽

E. R. McFadden ◽

R. H. Ingram

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Oxygen Mixture ◽

Flow Volume ◽

Mixture Density ◽

Lung Capacity ◽

Airway Constriction ◽

Maximal Expiratory Flow ◽

Airway Response ◽

Expiratory Flow

We examined the bronchoconstriction produced by airway hypocapnia in normal subjects. Maximal expiratory flow at 25% vital capacity on partial expiratory flow-volume (PEFV) curves fell during hypocapnia both on air and on an 80% helium- 20% oxygen mixture. Density dependence also fell, suggesting predominantly small airway constriction. The changes seen on PEFV curves were not found on maximal expiratory flow-volume curves, indicating the inhalation to total lung capacity substantially reversed the constriction. Pretreatment with a beta-sympathomimetic agent blocked the response, whereas atropine pretreatment did not, suggesting that hypocapnia affects airway smooth muscle directly, not via cholinergic efferents.

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HIGH FREQUENCY PERCUSSIVE VENTILATION CAN MIMIC AIRWAY PRESSURE RELEASE VENTILATION IN A TEST LUNG MODEL

Critical Care Medicine ◽

10.1097/00003246-200412001-00144 ◽

2004 ◽

Vol 32 (Supplement) ◽

pp. A38

Author(s):

Faera L Byerly ◽

Bruce A Cairns ◽

Kathy A Short ◽

John A Haithcock ◽

Lynn Shapiro ◽

...

Keyword(s):

High Frequency ◽

Airway Pressure ◽

Airway Pressure Release Ventilation ◽

Lung Model ◽

Test Lung ◽

Pressure Release ◽

Pressure Release Ventilation

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Determinants of maximal expiratory flow from the lungs.

Journal of Applied Physiology ◽

10.1152/jappl.1967.23.5.646 ◽

1967 ◽

Vol 23 (5) ◽

pp. 646-662 ◽

Cited By ~ 244

Author(s):

N B Pride ◽

S Permutt ◽

R L Riley ◽

B Bromberger-Barnea

Keyword(s):

Maximal Expiratory Flow ◽

Expiratory Flow

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Pilot Study on Healthy Volunteers to Investigate the Implications of Expiratory Positive Airway Pressure Applied Via a Full-Face Mask on Capnographic Parameters and Subject Comfort Level

CHEST Journal ◽

10.1016/j.chest.2017.08.1125 ◽

2017 ◽

Vol 152 (4) ◽

pp. A1091

Author(s):

Rodolfo Estrada ◽

Richard Wettstein ◽

Ruben Restrepo ◽

Luis Reyes ◽

Jay Peters

Keyword(s):

Pilot Study ◽

Healthy Volunteers ◽

Airway Pressure ◽

Positive Airway Pressure ◽

Face Mask ◽

Comfort Level ◽

Expiratory Positive Airway Pressure ◽

Full Face

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Volume history and effect on airway reactivity in infants and adults

Journal of Applied Physiology ◽

10.1152/japplphysiol.00986.2001 ◽

2002 ◽

Vol 93 (3) ◽

pp. 1069-1074 ◽

Cited By ~ 22

Author(s):

A. Weist ◽

T. Williams ◽

J. Kisling ◽

C. Clem ◽

R. S. Tepper

Keyword(s):

Vital Capacity ◽

Healthy Adults ◽

Airway Hyperreactivity ◽

Airway Reactivity ◽

Maximal Expiratory Flow ◽

Healthy Infants ◽

Forced Expiratory Flow ◽

Residual Capacity ◽

Expiratory Flow ◽

Volume History

Volume history is an important determinant of airway responsiveness. In healthy adults undergoing airway challenge, deep inspiration (DI) provides bronchodilating and bronchoprotective effects; however, the effectiveness of DI is limited in asthmatic adults. We hypothesized that, when assessed under similar conditions, healthy infants have heightened airway reactivity compared with healthy adults and that the effectiveness of DI is limited in infants. We compared the effect of DI on reactivity by using full (DI) vs. partial (no DI) forced-expiratory maneuvers on 2 days in supine, healthy nonasthmatic infants (21) and adults (10). Reactivity was assessed by methacholine doses that decreased forced expiratory flow after exhalation of 75% forced vital capacity during a full maneuver and maximal expiratory flow at functional residual capacity during a partial maneuver by 30% from baseline. Reactivity in adults increased when DI was absent, whereas infants' reactivity was unchanged. Infants were more reactive than adults in the presence of DI; however, adult and infant reactivity was similar in its absence. Our findings indicate that healthy infants are more reactive than adults and, like asthmatic adults, do not benefit from DI; this difference may be an important characteristic of airway hyperreactivity.

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