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The Journal of Pediatrics Jun 2023
Topics: Humans; Electric Impedance; Respiratory System; Airway Resistance; Thorax
PubMed: 36646246
DOI: 10.1016/j.jpeds.2023.01.007 -
Journal of Clinical Monitoring and... Dec 2023The endotracheal tubes (ETTs) used for children have a smaller inner diameter. Accordingly, the resistance across ETT (R) is higher. Theoretically, shortening the ETTs... (Observational Study)
Observational Study
Effectiveness of substantial shortening of the endotracheal tube for decreasing airway resistance and increasing tidal volume during pressure-controlled ventilation in pediatric patients: a prospective observational study.
The endotracheal tubes (ETTs) used for children have a smaller inner diameter. Accordingly, the resistance across ETT (R) is higher. Theoretically, shortening the ETTs can decrease total airway resistance (R), because R is sum of R and patient's airway resistance. However, the effectiveness of ETT shortening for mechanical ventilation in the clinical setting has not been reported. We assessed the effectiveness of shortening a cuffed ETT for decreasing R, and increasing tidal volume (TV), and estimated the R/R ratio in children. In anesthetized children in a constant pressure-controlled ventilation setting, R and TV were measured with a pneumotachometer before and after shortening a cuffed ETT. In a laboratory experiment, the pressure gradient across the original length, shortened length, and the slip joint alone of the ETT were measured. We then determined the R/R ratio using the above results. The clinical study included 22 children. The median ETT percent shortening was 21.7%. Median R was decreased from 26 to 24 cmHO/L/s, and median TV was increased by 6% after ETT shortening. The laboratory experiment showed that ETT length and the pressure gradient across ETT are linearly related under a certain flow rate, and approximately 40% of the pressure gradient across the ETT at its original length was generated by the slip joint. Median R/R ratio were calculated as 0.69. The effectiveness of ETT shortening on R and TV was very limited, because the resistance of the slip joint was very large.
Topics: Humans; Child; Airway Resistance; Tidal Volume; Intubation, Intratracheal; Respiration, Artificial; Lung
PubMed: 37289350
DOI: 10.1007/s10877-023-01038-w -
PloS One 2021Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive...
Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive disease, we measured pulmonary function in healthy adults with expiratory loading. Thirty-seven volunteers (25±5 yr) completed spirometry and body plethysmography under control and threshold expiratory loading of 7, 11 cmH2O, and a subset at 20 cmH2O (n = 11). We analyzed the shape of the flow-volume relationship with rectangular area ratio (RAR; Ma et al., Respir Med 2010). Airway resistance was increased (p<0.0001) with 7 and 11 cmH2O loading vs control (9.20±1.02 and 11.76±1.68 vs. 2.53± 0.80 cmH2O/L/s). RAR was reduced (p = 0.0319) in loading vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08). FEV1 was reduced (p<0.0001) in loading vs control (3.24±0.81 and 3.23±0.80 vs. 4.04±1.05 L). FVC was reduced (p<0.0001) in loading vs control (4.11±1.01 and 4.14±1.03 vs. 5.03±1.34 L). Peak expiratory flow (PEF) was reduced (p<0.0001) in loading vs control (6.03±1.67 and 6.02±1.84 vs. 8.50±2.81 L/s). FEV1/FVC (p<0.0068) was not clinically significant and FRC (p = 0.4) was not different in loading vs control. Supra-physiologic loading at 20 cmH2O did not result in further limitation. Expiratory loading reduced FEV1, FVC, PEF, but there were no clinically meaningful differences in FEV1/FVC, FRC, or RAR. Imposed expiratory loading likely leads to high airway pressures that resist dynamic airway compression. Thus, a concave expiratory flow-volume relationship was consistently absent-a key limitation for model comparison with pulmonary function in COPD. Threshold loading may be a useful strategy to increase work of breathing or induce dynamic hyperinflation.
Topics: Adult; Airway Resistance; Exhalation; Humans; Lung; Plethysmography; Reference Values; Respiratory Function Tests; Spirometry; Young Adult
PubMed: 34115812
DOI: 10.1371/journal.pone.0252916 -
Pediatric Critical Care Medicine : a... Oct 2022To describe pulmonary resistance in children undergoing invasive mechanical ventilation (MV) for different causes.
OBJECTIVES
To describe pulmonary resistance in children undergoing invasive mechanical ventilation (MV) for different causes.
DESIGN
A cross-sectional study.
SETTING
Two PICUs in the South region of Brazil.
PATIENTS
Children 1 month to 15 years old undergoing MV for more than 24 hours were included. We recorded ventilator variables and measured pulmonary mechanics (inspiratory and expiratory resistance, auto positive end-expiratory pressure [PEEP], and dynamic and static compliance) in the first 48 hours of MV.
INTERVENTIONS
Measurements of the respiratory mechanics variables during neuromuscular blockade.
MEASUREMENTS AND MAIN RESULTS
A total of 113 children were included, 5 months (median [interquartile range (IQR) [2.0-21.5 mo]) old, and median (IQR) weight 6.5 kg (4.5-11.0 kg), with 60% male. Median (IQR) peak inspiratory pressure (PIP) was 30 cm H 2 O (26-35 cm H 2 O), and median (IQR) PEEP was 5 cm H 2 O (5-7 cm H 2 O). The median (IQR) duration of MV was 7 days (5-9 d), and mortality was nine of 113 (8%). The median (IQR) inspiratory and expiratory resistances were 94.0 cm H 2 O/L/s (52.5-155.5 cm H 2 O/L/s) and 117 cm H 2 O/L/s (71-162 cm H 2 O/L/s), with negative association with weight and age (Spearman -0.850). When we assess weight, in smaller children (< 10 kg) had increased pulmonary resistance, with mean values over 100 mH 2 O/L/s, which were higher than larger children ( p < 0.001).
CONCLUSIONS
Increased pulmonary resistance is prevalent in the pediatric population undergoing invasive MV. Especially in children less than 1 year old, this variable should be considered when defining a ventilatory strategy.
Topics: Airway Resistance; Child; Cross-Sectional Studies; Female; Humans; Infant; Lung; Male; Positive-Pressure Respiration; Respiratory Mechanics
PubMed: 35880871
DOI: 10.1097/PCC.0000000000003035 -
BMC Pulmonary Medicine May 2024Assessing mechanical properties of the respiratory system (C) during mechanical ventilation necessitates an end-inspiration flow of zero, which requires an...
BACKGROUND
Assessing mechanical properties of the respiratory system (C) during mechanical ventilation necessitates an end-inspiration flow of zero, which requires an end-inspiratory occlusion maneuver. This lung model study aimed to observe the effect of airflow obstruction on the accuracy of respiratory mechanical properties during pressure-controlled ventilation (PCV) by analyzing dynamic signals.
METHODS
A Hamilton C3 ventilator was attached to a lung simulator that mimics lung mechanics in healthy, acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) models. PCV and volume-controlled ventilation (VCV) were applied with tidal volume (V) values of 5.0, 7.0, and 10.0 ml/kg. Performance characteristics and respiratory mechanics were assessed and were calibrated by virtual extrapolation using expiratory time constant (RC).
RESULTS
During PCV ventilation, drive pressure (DP) was significantly increased in the ARDS model. Peak inspiratory flow (PIF) and peak expiratory flow (PEF) gradually declined with increasing severity of airflow obstruction, while DP, end-inspiration flow (EIF), and inspiratory cycling ratio (EIF/PIF%) increased. Similar estimated values of C and airway resistance (R) during PCV and VCV ventilation were obtained in healthy adult and mild obstructive models, and the calculated errors did not exceed 5%. An underestimation of C and an overestimation of R were observed in the severe obstruction model.
CONCLUSION
Using the modified dynamic signal analysis approach, respiratory system properties (C and R) could be accurately estimated in patients with non-severe airflow obstruction in the PCV mode.
Topics: Humans; Airway Resistance; Pulmonary Disease, Chronic Obstructive; Respiration, Artificial; Respiratory Distress Syndrome; Tidal Volume; Respiratory Mechanics; Lung; Lung Compliance; Models, Biological; Adult
PubMed: 38769572
DOI: 10.1186/s12890-024-03061-2 -
Respiratory Physiology & Neurobiology Nov 2015The effect of remodeling on airway function is uncertain. It may affect airway compressibility during forced expirations differently than airflow resistance, providing a...
The effect of remodeling on airway function is uncertain. It may affect airway compressibility during forced expirations differently than airflow resistance, providing a tool for its assessment. The aim of the current study was to compare the effects of acute and chronic antigen challenge on methacholine-induced bronchoconstriction assessed from resistance and maximal tidal expiratory flow. Balb/C mice were sensitized with ovalbumin (OVA) and challenged either daily for three days with intra-nasal OVA or daily for 5 days and three times a week for 5 subsequent weeks. Acute and chronic allergen challenge induced airway hyperresponsiveness (AHR) to methacholine. However the relationship between maximal tidal expiratory flow and resistance during methacholine challenge was different between the two conditions, suggesting that the determinants of AHR are not identical following acute and chronic allergen exposure. We conclude that the contrast of changes in maximal tidal expiratory flow and respiratory resistance during methacholine-induced bronchoconstriction may allow the detection of the mechanical consequences of airway remodeling.
Topics: Acute Disease; Airway Remodeling; Airway Resistance; Animals; Bronchoconstrictor Agents; Chronic Disease; Disease Models, Animal; Elasticity; Female; Goblet Cells; Methacholine Chloride; Mice, Inbred BALB C; Muscle, Smooth, Vascular; Ovalbumin; Pulmonary Ventilation; Random Allocation; Respiratory Hypersensitivity; Tidal Volume
PubMed: 26213118
DOI: 10.1016/j.resp.2015.07.007 -
Einstein (Sao Paulo, Brazil) 2019To simulate different diameters of endotracheal tubes and to verify the fluid dynamics aspects by means of flow and resistance measurements.
OBJECTIVE
To simulate different diameters of endotracheal tubes and to verify the fluid dynamics aspects by means of flow and resistance measurements.
METHODS
Fluid dynamics software was used to calculate mean flow and airway resistance in endotracheal tube with a diameter of 6.0, 7.0, 7.5, 8.0, 9.0 and 10.0mm at normal body temperature and under constant pressure. The same measurements were taken in the fusion of the first 22cm of a 9.0mm endotracheal tube with 10.0mm diameter, and with the end part in 12cm of a 6.0mm endotracheal tube with 7.0mm diameter.
RESULTS
The fusion of the first 22cm of an endotracheal tube of 10.0mm diameter with the terminal part in 12cm of an endotracheal tube of 6.0mm diameter, preserving the total length of 34cm, generated average flow and airway resistance similar to that of a conventional 7.5mm endotracheal tube.
CONCLUSION
This simulation study demonstrates that a single-sized endotracheal tube may facilitate endotracheal intubation without causing increased airway resistance.
Topics: Airway Resistance; Computer Simulation; Equipment Design; Intubation, Intratracheal; Respiration, Artificial
PubMed: 31644676
DOI: 10.31744/einstein_journal/2020AO4805 -
Computers in Biology and Medicine Jan 2023Current methods to diagnose and monitor COPD employ spirometry as the gold standard to identify lung function reduction with reduced forced expiratory volume (FEV)/vital...
BACKGROUND
Current methods to diagnose and monitor COPD employ spirometry as the gold standard to identify lung function reduction with reduced forced expiratory volume (FEV)/vital capacity (VC) ratio. Current methods utilise linear assumptions regarding airway resistance, where nonlinear resistance modelling may provide rapid insight into patient specific condition and disease progression. This study examines model-based expiratory resistance in healthy lungs and those with progressively more severe COPD.
METHODS
Healthy and COPD pressure (P)[cmHO] and flow (Q)[L/s] data is obtained from the literature, and 5 intermediate levels of COPD and responses are created to simulate COPD progression and assess model-based metric resolution. Linear and nonlinear single compartment models are used to identify changes in inspiratory (R) and linear (R)/nonlinear (RΦ) expiratory resistance with disease severity and over the course of expiration.
RESULTS
R increases from 2.1 to 7.3 cmHO/L/s, R increases from 2.4 to 10.0 cmHO/L/s with COPD severity. Nonlinear RΦ increases (mean RΦ: 2.5 cmHO/L/s (healthy) to 24.4 cmHO/L/s (COPD)), with increasing end-expiratory nonlinearity as COPD severity increases.
CONCLUSION
Expiratory resistance is increasingly highly nonlinear with COPD severity. These results show a simple, nonlinear model can capture fundamental COPD dynamics and progression from regular breathing data, and such an approach may be useful for patient-specific diagnosis and monitoring.
Topics: Humans; Pulmonary Disease, Chronic Obstructive; Lung; Airway Resistance; Forced Expiratory Volume; Exhalation
PubMed: 36543001
DOI: 10.1016/j.compbiomed.2022.106430 -
Respiratory Physiology & Neurobiology Jun 2015In healthy Vietnamese children the respiratory resistance has been suggested to be similar at 110 cm height but larger at 130 cm when compared with data in Caucasians...
In healthy Vietnamese children the respiratory resistance has been suggested to be similar at 110 cm height but larger at 130 cm when compared with data in Caucasians from the literature, suggesting smaller airways in older Vietnamese children (Vu et al., 2008). The hypothesis tested here is whether the difference in airway resistance remains consistent throughout growth, and if it is larger in adult Vietnamese than in Caucasians. Airway resistance and Functional Residual Capacity were measured in healthy young Caucasian and Vietnamese adults in their respective native country using identical equipment and protocols. Ninety five subjects in Vietnam (60 males) and 101 in France (41 males) were recruited. Airway resistance was significantly larger in Vietnamese than in Caucasians and in females than in males, consistent with difference in body dimensions. Specific airway resistance however was not different by ethnicity or gender. The findings do not support the hypothesis that airway size at adult age - once normalized for lung volume - differs between Vietnamese and Caucasians.
Topics: Adolescent; Adult; Airway Resistance; Asian People; Female; France; Humans; Male; Multivariate Analysis; Plethysmography; Sex Characteristics; Vietnam; White People; Young Adult
PubMed: 25796614
DOI: 10.1016/j.resp.2015.03.002 -
Pediatric Allergy, Immunology, and... Dec 2023
Topics: Oscillometry; Respiratory Function Tests; Airway Resistance
PubMed: 38134317
DOI: 10.1089/ped.2023.0149