Pressure-controlled mechanical ventilation

2016 ◽  
Author(s):  
Thomas Muders ◽  
Christian Putensen
Keyword(s):  
Mechanical Ventilation ◽  
Tidal Volume ◽  
Spontaneous Breathing ◽  
Airway Pressure ◽  
Gas Flow ◽  
Conventional Mechanical Ventilation ◽  
Lung Inflation ◽  
Cycle Times ◽  
Airway Pressures ◽  
Pressure Controlled

Beside reduction in tidal volume limiting peak airway pressure minimizes the risk for ventilator-associated-lung-injury in patients with acute respiratory distress syndrome. Pressure-controlled, time-cycled ventilation (PCV) enables the physician to keep airway pressures under strict limits by presetting inspiratory and expiratory pressures, and cycle times. PCV results in a square-waved airway pressure and a decelerating inspiratory gas flow holding the alveoli inflated for the preset time. Preset pressures and cycle times, and respiratory system mechanics affect alveolar and intrinsic positive end-expiratory (PEEPi) pressures, tidal volume, total minute, and alveolar ventilation. When compared with flow-controlled, time-cycled (‘volume-controlled’) ventilation, PCV results in reduced peak airway pressures, but higher mean airway. Homogeneity of regional peak alveolar pressure distribution within the lung is improved. However, no consistent data exist, showing PCV to improve patient outcome. During inverse ratio ventilation (IRV) elongation of inspiratory time increases mean airway pressure and enables full lung inflation, whereas shortening expiratory time causes incomplete lung emptying and increased PEEPi. Both mechanisms increase mean alveolar and transpulmonary pressures, and may thereby improve lung recruitment and gas exchange. However, when compared with conventional mechanical ventilation using an increased external PEEP to reach the same magnitude of total PEEP as that produced intrinsically by IRV, IRV has no advantage. Airway pressure release ventilation (APRV) provides a PCV-like squared pressure pattern by time-cycled switches between two continuous positive airway pressure levels, while allowing unrestricted spontaneous breathing in any ventilatory phase. Maintaining spontaneous breathing with APRV is associated with recruitment and improved ventilation of dependent lung areas, improved ventilation-perfusion matching, cardiac output, oxygenation, and oxygen delivery, whereas need for sedation, vasopressors, and inotropic agents and duration of ventilator support decreases.

Cyclic changes in right ventricular output impedance during mechanical ventilation

1999 ◽  
Vol 87 (5) ◽  
pp. 1644-1650 ◽  
Author(s):  
Antoine Vieillard-Baron ◽  
Yann Loubieres ◽  
Jean-Marie Schmitt ◽  
Bernard Page ◽  
Olivier Dubourg ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Right Ventricular ◽  
Tidal Volume ◽  
Airway Pressure ◽  
Right Atrial ◽  
Lung Inflation ◽  
Velocity Time Integral ◽  
Time Integral ◽  
The Right ◽  
Cyclic Changes

In a context such as acute respiratory distress syndrome, where optimum tidal volume and airway pressure levels are debated, the present study was designed to differentiate the right ventricular (RV) consequences of increasing lung volume from those secondary to increasing airway pressure during tidal ventilation. The study was conducted by combined two-dimensional echocardiographic and Doppler studies in 10 patients requiring mechanical ventilation in the controlled mode because of acute respiratory failure. Continuous monitoring of airway pressure on echocardiographic and Doppler recordings provided accurate timing of each cardiac event during the respiratory cycle, with particular attention being paid to end-expiratory and end-inspiratory atrial diameters, RV dimensions, and pulmonary artery and tricuspid flow estimated by the velocity-time integral (PAVTIand TVTI, respectively). At baseline, lung inflation during the inspiratory phase of mechanical ventilation produced a drop in PAVTIfrom 14.3 ± 2.6 cm at end expiration to 11.3 ± 2.1 cm at end inspiration. This drop occurred without reduction in right atrial diameter or in RV diastolic dimensions. It was not preceded but was followed by a decrease in TVTI, thus confirming an increase in RV outflow impedance. Manipulation of tidal volume without changing airway pressure and manipulation of airway pressure without changing tidal volume demonstrated that tidal volume, but not airway pressure, was the main determinant factor of RV afterloading during mechanical ventilation.

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

2011 ◽  
Vol 39 (6) ◽  
pp. 1103-1110 ◽  
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.

Augmentation of phrenic neural activity by increased rates of lung inflation

1981 ◽  
Vol 50 (1) ◽  
pp. 149-161 ◽  
Author(s):  
A. I. Pack ◽  
R. G. DeLaney ◽  
A. P. Fishman
Keyword(s):  
Tidal Volume ◽  
Volume Change ◽  
Neural Activity ◽  
Negative Pressure ◽  
Spontaneous Breathing ◽  
Moving Average ◽  
Constant Flow ◽  
Lung Inflation ◽  
Negative Pressure Ventilation ◽  
Single Breath

Studies were conducted in anesthetized paralyzed dogs using a cycle-triggered constant-flow ventilator, which ventilated the animal in phase with the recorded phrenic neural activity. Intermittently tests were performed in which the animal was ventilated with a different airflow for a single breath. Increased airflows, within the range generated during spontaneous breathing, caused an increased rate of rise of the moving average phrenic neurogram and a shortening of the duration of the nerve burst. The magnitude of the increase in the rate of rise of the neurogram was related to the level of inspiratory airflow. Tests with brief pulses of airflow showed that an increase in the rate of rise of the phrenic neurogram could be produced without inflating the lung above the resting tidal volume of the animal. Similar results were obtained with negative-pressure ventilation and the effects were abolished by vagotomy. This vagally mediated augmentation of phrenic neural output may accelerate the inspiratory volume change in the lung during spontaneous breathing at hyperpneic levels.

scholarly journals Efficacy of airway pressure release ventilation for acute respiratory distress syndrome: A meta-analysis

2020 ◽  
Author(s):  
Zhen Junhai ◽  
Hu Bangchuan ◽  
Gong Shijin ◽  
Yu Yihua ◽  
Yan Jing ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Airway Pressure ◽  
Distress Syndrome ◽  
Meta Analysis ◽  
Conventional Mechanical Ventilation ◽  
Controlled Trials ◽  
Randomized Controlled ◽  
Pressure Release Ventilation

Abstract Background Airway pressure release ventilation (APRV) has been described many years, however, it is still unclear whether APRV improves outcomes in critically ill patients admitted to Intensive Care Unit with acute respiratory distress syndrome (ARDS). Methods 3 databases were searched for randomized controlled trials (RCTs) until 8 August 2019. The relative risk (RR), mean difference (MD) and 95% confidence intervals (CI) were determined. Results A total of six randomized controlled trials (RCTs) were included with 360 ARDS patients. The Meta analysis showed that the mean arterial pressure (MAP) in APRV group is higher than traditional mechanical ventilation group [MD = 2.35, 95% CI=(1.05,3.64), P = 0.0004], and the airway peak pressure (Ppeak) is lower in APRV group with statistical difference [MD=-2.04,95% CI=(-3.33,-0.75), P = 0.002]. However, no significant beneficial effect on oxygen index (PaO2/FiO2) was shown between two groups (MD = 26.24, 95% CI=(-26.50,78.97), P = 0.33). Compared with conventional mechanical ventilation, APRV significantly improved 28-day mortality [RR = 0.66, 95% CI=(0.47,0.94), P = 0.02]. Conclusions For critically ill patients with ARDS, application of APRV is associated with the increase of MAP, the reduction of the airway Ppeak and 28-day mortality, while there is no sufficient evidence to support the APRV is superior to conventional mechanical ventilation in PaO2/FiO2.

Mechanical ventilation

2016 ◽  
Author(s):  
Robert O Grounds ◽  
Andrew Rhodes
Keyword(s):  
Mechanical Ventilation ◽  
Lung Injury ◽  
Gas Flow ◽  
Spontaneous Respiration ◽  
Positive Pressure ◽  
International Consensus ◽  
Ventilation Modes ◽  
Protective Strategies ◽  
Pressure Controlled

Mechanical ventilation is used to assist or replace spontaneous respiration. Gas flow can be generated by negative pressure techniques, but it is positive pressure ventilation that is the most efficacious in intensive care. There are numerous pulmonary and extrapulmonary indications for mechanical ventilation, and it is the underlying pathology that will determine the duration of ventilation required. Ventilation modes can broadly be classified as volume- or pressure-controlled, but modern ventilators combine the characteristics of both in order to complement the diverse requirements of individual patients. To avoid confusion, it is important to appreciate that there is no international consensus on the classification of ventilation modes. Ventilator manufacturers can use terms that are similar to those used by others that describe very different modes or have completely different names for similar modes. It is well established that ventilation in itself can cause or exacerbate lung injury, so the evidence-based lung-protective strategies should be adhered to. The term acute lung injury has been abolished, whilst a new definition and classification for the acute respiratory distress syndrome has been defined.

scholarly journals Can you calculate the total respiratory, lung, and chest wall respiratory mechanics?

2020 ◽  
Vol 1 (1) ◽  
pp. 24-26
Author(s):  
Mia Shokry ◽  
Kimiyo Yamasaki ◽  
Ehab Daoud
Keyword(s):  
Mechanical Ventilation ◽  
Tidal Volume ◽  
Chest Wall ◽  
Airway Pressure ◽  
Respiratory Mechanics ◽  
Peak Inspiratory Pressure ◽  
Esophageal Pressure ◽  
Horizontal Line ◽  
Pulmonary Pressure ◽  
Volume Controlled

Figure: Waveforms for a patient undergoing mechanical ventilation with volume controlled mode. Tidal Volume of 500 ml, PEEP 15, Constant inspiratory flow of 45 l/min A: Airway pressure in cmH2O, B: Esophageal pressure in cmH2O, C: Trans-pulmonary pressure in cmH2O, D: Flow in l/min, E: Tidal volume in ml Red dashed horizontal line: values at end of expiratory occlusion maneuver, White solid horizontal line: values at end of inspiratory occlusion maneuver, Green dashed horizontal line: values during peak inspiratory pressure.

Mechanical ventilation

2015 ◽  
Author(s):  
Gihan Abuella ◽  
Andrew Rhodes
Keyword(s):  
Mechanical Ventilation ◽  
Lung Injury ◽  
Gas Flow ◽  
Spontaneous Respiration ◽  
Positive Pressure ◽  
International Consensus ◽  
Ventilation Modes ◽  
Protective Strategies ◽  
Pressure Controlled

Mechanical ventilation is used to assist or replace spontaneous respiration. Gas flow can be generated by negative pressure techniques, but it is positive pressure ventilation that is the most efficacious in intensive care. There are numerous pulmonary and extrapulmonary indications for mechanical ventilation, and it is the underlying pathology that will determine the duration of ventilation required. Ventilation modes can broadly be classified as volume- or pressure-controlled, but modern ventilators combine the characteristics of both in order to complement the diverse requirements of individual patients. To avoid confusion, it is important to appreciate that there is no international consensus on the classification of ventilation modes. Ventilator manufacturers can use terms that are similar to those used by others that describe very different modes or have completely different names for similar modes. It is well established that ventilation in itself can cause or exacerbate lung injury, so the evidence-based lung-protective strategies should be adhered to. The term acute lung injury has been abolished, whilst a new definition and classification for the acute respiratory distress syndrome has been defined.

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