Expiratory Resistances Prevent Expiratory Diaphragm Contraction, Flow Limitation, and Lung Collapse. 2020

Mariangela Pellegrini, and Magni Gudmundsson, and Reka Bencze, and Monica Segelsjö, and Filip Freden, and Christian Rylander, and Göran Hedenstierna, and Anders S Larsson, and Gaetano Perchiazzi
Department of Surgical Sciences and.

Rationale: Tidal expiratory flow limitation (tidal-EFL) is not completely avoidable by applying positive end-expiratory pressure and may cause respiratory and hemodynamic complications in ventilated patients with lungs prone to collapse. During spontaneous breathing, expiratory diaphragmatic contraction counteracts tidal-EFL. We hypothesized that during both spontaneous breathing and controlled mechanical ventilation, external expiratory resistances reduce tidal-EFL.Objectives: To assess whether external expiratory resistances 1) affect expiratory diaphragmatic contraction during spontaneous breathing, 2) reduce expiratory flow and make lung compartments more homogeneous with more similar expiratory time constants, and 3) reduce tidal atelectasis, preventing hyperinflation.Methods: Three positive end-expiratory pressure levels and four external expiratory resistances were tested in 10 pigs after lung lavage. We analyzed expiratory diaphragmatic electric activity and respiratory mechanics. On the basis of computed tomography scans, four lung compartments-not inflated (atelectasis), poorly inflated, normally inflated, and hyperinflated-were defined.Measurements and Main Results: Consequently to additional external expiratory resistances, and mainly in lungs prone to collapse (at low positive end-expiratory pressure), 1) the expiratory transdiaphragmatic pressure decreased during spontaneous breathing by >10%, 2) expiratory flow was reduced and the expiratory time constants became more homogeneous, and 3) the amount of atelectasis at end-expiration decreased from 24% to 16% during spontaneous breathing and from 32% to 18% during controlled mechanical ventilation, without increasing hyperinflation.Conclusions: The expiratory modulation induced by external expiratory resistances preserves the positive effects of the expiratory brake while minimizing expiratory diaphragmatic contraction. External expiratory resistances optimize lung mechanics and limit tidal-EFL and tidal atelectasis, without increasing hyperinflation.

UI MeSH Term Description Entries
D008168 Lung Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood. Lungs
D009119 Muscle Contraction A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D011175 Positive-Pressure Respiration A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. Positive End-Expiratory Pressure,Positive-Pressure Ventilation,End-Expiratory Pressure, Positive,End-Expiratory Pressures, Positive,Positive End Expiratory Pressure,Positive End-Expiratory Pressures,Positive Pressure Respiration,Positive Pressure Ventilation,Positive-Pressure Respirations,Positive-Pressure Ventilations,Pressure, Positive End-Expiratory,Pressures, Positive End-Expiratory,Respiration, Positive-Pressure,Respirations, Positive-Pressure,Ventilation, Positive-Pressure,Ventilations, Positive-Pressure
D012121 Respiration, Artificial Any method of artificial breathing that employs mechanical or non-mechanical means to force the air into and out of the lungs. Artificial respiration or ventilation is used in individuals who have stopped breathing or have RESPIRATORY INSUFFICIENCY to increase their intake of oxygen (O2) and excretion of carbon dioxide (CO2). Ventilation, Mechanical,Mechanical Ventilation,Artificial Respiration,Artificial Respirations,Mechanical Ventilations,Respirations, Artificial,Ventilations, Mechanical
D012123 Pulmonary Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Respiratory Airflow,Ventilation Tests,Ventilation, Pulmonary,Expiratory Airflow,Airflow, Expiratory,Airflow, Respiratory,Test, Ventilation,Tests, Ventilation,Ventilation Test
D012128 Respiratory Distress Syndrome A syndrome characterized by progressive life-threatening RESPIRATORY INSUFFICIENCY in the absence of known LUNG DISEASES, usually following a systemic insult such as surgery or major TRAUMA. ARDS, Human,Acute Respiratory Distress Syndrome,Adult Respiratory Distress Syndrome,Pediatric Respiratory Distress Syndrome,Respiratory Distress Syndrome, Acute,Respiratory Distress Syndrome, Adult,Respiratory Distress Syndrome, Pediatric,Shock Lung,Distress Syndrome, Respiratory,Distress Syndromes, Respiratory,Human ARDS,Lung, Shock,Respiratory Distress Syndromes,Syndrome, Respiratory Distress
D003964 Diaphragm The musculofibrous partition that separates the THORACIC CAVITY from the ABDOMINAL CAVITY. Contraction of the diaphragm increases the volume of the thoracic cavity aiding INHALATION. Respiratory Diaphragm,Diaphragm, Respiratory,Diaphragms,Diaphragms, Respiratory,Respiratory Diaphragms
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001261 Pulmonary Atelectasis Absence of air in the entire or part of a lung, such as an incompletely inflated neonate lung or a collapsed adult lung. Pulmonary atelectasis can be caused by airway obstruction, lung compression, fibrotic contraction, or other factors. Atelectasis, Congestive,Lung Collapse,Atelectasis,Compression Atelectasis,Compression Pulmonary Atelectasis,Congestive Atelectasis,Congestive Pulmonary Atelectasis,Contraction Pulmonary Atelectasis,Postoperative Pulmonary Atelectasis,Resorption Atelectasis,Resorption Pulmonary Atelectasis,Atelectases,Atelectases, Compression,Atelectases, Compression Pulmonary,Atelectases, Congestive,Atelectases, Congestive Pulmonary,Atelectases, Contraction Pulmonary,Atelectases, Postoperative Pulmonary,Atelectases, Pulmonary,Atelectases, Resorption,Atelectases, Resorption Pulmonary,Atelectasis, Compression,Atelectasis, Compression Pulmonary,Atelectasis, Congestive Pulmonary,Atelectasis, Contraction Pulmonary,Atelectasis, Postoperative Pulmonary,Atelectasis, Pulmonary,Atelectasis, Resorption,Atelectasis, Resorption Pulmonary,Collapse, Lung,Compression Atelectases,Compression Pulmonary Atelectases,Congestive Atelectases,Congestive Pulmonary Atelectases,Contraction Pulmonary Atelectases,Postoperative Pulmonary Atelectases,Pulmonary Atelectases,Pulmonary Atelectases, Compression,Pulmonary Atelectases, Congestive,Pulmonary Atelectases, Contraction,Pulmonary Atelectases, Postoperative,Pulmonary Atelectases, Resorption,Pulmonary Atelectasis, Compression,Pulmonary Atelectasis, Congestive,Pulmonary Atelectasis, Contraction,Pulmonary Atelectasis, Postoperative,Pulmonary Atelectasis, Resorption,Resorption Atelectases,Resorption Pulmonary Atelectases

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