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Respiratory Care Jun 2020Mechanical ventilation in critically ill patients must effectively unload inspiratory muscles and provide safe ventilation (ie, enhancing gas exchange, protect the lungs... (Review)
Review
Mechanical ventilation in critically ill patients must effectively unload inspiratory muscles and provide safe ventilation (ie, enhancing gas exchange, protect the lungs and the diaphragm). To do that, the ventilator should be in synchrony with patient's respiratory rhythm. The complexity of such interplay leads to several concerning issues that clinicians should be able to recognize. Asynchrony between the patient and the ventilator may induce several deleterious effects that require a proper physiological understanding to recognize and manage them. Different tools have been developed and proposed beyond the careful analysis of the ventilator waveforms to help clinicians in the decision-making process. Moreover, appropriate handling of asynchrony requires clinical skills, physiological knowledge, and suitable medication management. New technologies and devices are changing our daily practice, from automated real-time recognition of asynchronies and their distribution during mechanical ventilation, to smart alarms and artificial intelligence algorithms based on physiological big data and personalized medicine. Our goal as clinicians is to provide care of patients based on the most accurate and current knowledge, and to incorporate new technological methods to facilitate and improve the care of the critically ill.
Topics: Critical Illness; Humans; Pulmonary Ventilation; Respiration, Artificial; Respiratory Mechanics; Ventilators, Mechanical
PubMed: 32457175
DOI: 10.4187/respcare.07404 -
Anesthesiology Nov 2020Prone ventilation redistributes lung inflation along the gravitational axis; however, localized, nongravitational effects of body position are less well characterized....
BACKGROUND
Prone ventilation redistributes lung inflation along the gravitational axis; however, localized, nongravitational effects of body position are less well characterized. The authors hypothesize that positional inflation improvements follow both gravitational and nongravitational distributions. This study is a nonoverlapping reanalysis of previously published large animal data.
METHODS
Five intubated, mechanically ventilated pigs were imaged before and after lung injury by tracheal injection of hydrochloric acid (2 ml/kg). Computed tomography scans were performed at 5 and 10 cm H2O positive end-expiratory pressure (PEEP) in both prone and supine positions. All paired prone-supine images were digitally aligned to each other. Each unit of lung tissue was assigned to three clusters (K-means) according to positional changes of its density and dimensions. The regional cluster distribution was analyzed. Units of tissue displaying lung recruitment were mapped.
RESULTS
We characterized three tissue clusters on computed tomography: deflation (increased tissue density and contraction), limited response (stable density and volume), and reinflation (decreased density and expansion). The respective clusters occupied (mean ± SD including all studied conditions) 29.3 ± 12.9%, 47.6 ± 11.4%, and 23.1 ± 8.3% of total lung mass, with similar distributions before and after lung injury. Reinflation was slightly greater at higher PEEP after injury. Larger proportions of the reinflation cluster were contained in the dorsal versus ventral (86.4 ± 8.5% vs. 13.6 ± 8.5%, P < 0.001) and in the caudal versus cranial (63.4 ± 11.2% vs. 36.6 ± 11.2%, P < 0.001) regions of the lung. After injury, prone positioning recruited 64.5 ± 36.7 g of tissue (11.4 ± 6.7% of total lung mass) at lower PEEP, and 49.9 ± 12.9 g (8.9 ± 2.8% of total mass) at higher PEEP; more than 59.0% of this recruitment was caudal.
CONCLUSIONS
During mechanical ventilation, lung reinflation and recruitment by the prone positioning were primarily localized in the dorso-caudal lung. The local effects of positioning in this lung region may determine its clinical efficacy.
Topics: Animals; Lung; Models, Animal; Prone Position; Pulmonary Ventilation; Respiration, Artificial; Supine Position; Swine; Tomography, X-Ray Computed
PubMed: 32773690
DOI: 10.1097/ALN.0000000000003509 -
Respiratory Care Jun 2013Patient-ventilator synchrony and patient comfort are assumed to go hand in hand, yet few studies provide support for this common sense idea. In reality, synchrony... (Review)
Review
Patient-ventilator synchrony and patient comfort are assumed to go hand in hand, yet few studies provide support for this common sense idea. In reality, synchrony between the patient and ventilator is complex and can be affected by the ventilator settings, type of ventilator, patient-ventilator interface, and sedation. Inspections of airway pressure and flow waveforms are reliable methods for detecting asynchrony, and automated detection seems accurate. A number of types of asynchronies have been defined, and asynchrony during invasive and noninvasive ventilation have different calling cards. There is a clear association between asynchrony, ventilator-induced diaphragmatic dysfunction, and duration of mechanical ventilation. Whether these are cause and effect or simply associated remains to be determined.
Topics: Dyspnea; Humans; Pulmonary Ventilation; Respiration, Artificial; Respiratory Mechanics; Respiratory Muscles; Ventilators, Mechanical; Work of Breathing
PubMed: 23709195
DOI: 10.4187/respcare.02507 -
Respiratory Care Apr 2018Patient-ventilator asynchrony exists when the phases of breath delivered by the ventilator do not match those of the patient. Asynchronies occur throughout mechanical... (Review)
Review
Patient-ventilator asynchrony exists when the phases of breath delivered by the ventilator do not match those of the patient. Asynchronies occur throughout mechanical ventilation and negatively affect patient comfort, duration of mechanical ventilation, length of ICU stays, and mortality. Identifying asynchronies requires careful attention to patients and their ventilator waveforms. This review discusses the different types of asynchronies, how they are generated, and their impact on patient comfort and outcome. Moreover, it discusses practical approaches for detecting, correcting, and preventing asynchronies. Current evidence suggests that the best approach to managing asynchronies is by adjusting ventilator settings. Proportional modes improve patient-ventilator coupling, resulting in greater comfort and less dyspnea, but not in improved outcomes with respect to the duration of mechanical ventilation, delirium, or cognitive impairment. Advanced computational technologies will allow smart alerts, and models based on time series of asynchronies will be able to predict and prevent asynchronies, making it possible to tailor mechanical ventilation to meet each patient's needs throughout the course of mechanical ventilation.
Topics: Humans; Periodicity; Pulmonary Ventilation; Respiration Disorders; Respiration, Artificial; Respiratory Mechanics; Ventilators, Mechanical
PubMed: 29487094
DOI: 10.4187/respcare.05949 -
Thorax May 2006Understanding collateral ventilation is probably central to planning new bronchoscopic techniques for treating emphysema
Understanding collateral ventilation is probably central to planning new bronchoscopic techniques for treating emphysema
Topics: Bronchoscopy; Humans; Pulmonary Alveoli; Pulmonary Emphysema; Pulmonary Ventilation
PubMed: 16648350
DOI: 10.1136/thx.2006.060509 -
Seminars in Respiratory and Critical... Oct 2010Aging is associated with a progressive deterioration in the structure and function of the pulmonary circulation. Remodeling of the pulmonary vasculature occurs from... (Review)
Review
Aging is associated with a progressive deterioration in the structure and function of the pulmonary circulation. Remodeling of the pulmonary vasculature occurs from maturity to senescence that is characterized by an increase in pulmonary vascular stiffness, pulmonary vascular pressures, and pulmonary vascular resistance along with increased heterogeneity of alveolar ventilation and pulmonary perfusion and decreased pulmonary capillary blood volume and membrane diffusing capacity that is consistent with a reduction in alveolar-capillary surface area. In theory, the aforementioned age-related changes in the pulmonary circulation may conspire to make elderly individuals more susceptible to gas exchange abnormalities during exercise. However, despite the erosion in ventilatory reserve with aging, the healthy older adult appears able to maintain alveolar ventilation at a level that allows maintenance of arterial blood gases within normal limits, even during heavy exercise. This ability to maintain adequate gas exchange likely occurs because age-related reductions in the maximal metabolic demand of exercise occur at a rate equal to or greater than the rate of deterioration in ventilatory reserve. A more prominent aspect of aging is the loss of lung elastic recoil that is associated with a modest reduction in the expiratory boundary of the maximal flow-volume envelope. This in turn increases the severity of expiratory airflow limitation and induces dynamic lung hyperinflation during exercise. The consequences of this age-associated decrease in elastic recoil on the pulmonary circulation are speculative, but an age-associated decline in elastic recoil may influence pulmonary vascular resistance and cardiac output, in addition to its impact on the work and oxygen cost of breathing.
Topics: Aged; Aging; Exercise; Exercise Tolerance; Heart Failure; Humans; Lung; Pulmonary Circulation; Pulmonary Gas Exchange; Pulmonary Ventilation
PubMed: 20941654
DOI: 10.1055/s-0030-1265894 -
International Journal of Environmental... Dec 2017Refractory ceramic fibers (RCFs) can cause adverse health effects on workers' respiratory system, yet no proper biomarkers have been used to detect early pulmonary...
Refractory ceramic fibers (RCFs) can cause adverse health effects on workers' respiratory system, yet no proper biomarkers have been used to detect early pulmonary injury of RCFs-exposed workers. This study assessed the levels of two biomarkers that are related to respiratory injury in RCFs-exposed workers, and explored their relations with lung function. The exposure levels of total dust and respirable fibers were measured simultaneously in RCFs factories. The levels of TGF-β1 and ceruloplasmin (CP) increased with the RCFs exposure level ( < 0.05), and significantly increased in workers with high exposure level (1.21 ± 0.49 ng/mL, 115.25 ± 32.44 U/L) when compared with the control group (0.99 ± 0.29 ng/mL, 97.90 ± 35.01 U/L) ( < 0.05). The levels of FVC and FEV₁ were significantly decreased in RCFs exposure group ( < 0.05). Negative relations were found between the concentrations of CP and FVC (B = -0.423, = 0.025), or FEV₁ (B = -0.494, = 0.014). The concentration of TGF-β1 (B = 0.103, = 0.001) and CP (B = 8.027, = 0.007) were associated with respirable fiber exposure level. Occupational exposure to RCFs can impair lung ventilation function and may have the potential to cause pulmonary inflammation and fibrosis. TGF-β1 and CP might be used as sensitive and noninvasive biomarkers to detect lung injury in occupational RCFs-exposed workers. Respirable fiber concentration can better reflect occupational RCFs exposure and related respiratory injuries.
Topics: Adult; Biomarkers; Ceramics; China; Dust; Forced Expiratory Volume; Humans; Lung; Male; Occupational Exposure; Pulmonary Fibrosis; Pulmonary Ventilation; Vital Capacity
PubMed: 29280967
DOI: 10.3390/ijerph15010042 -
NMR in Biomedicine Dec 2014The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and... (Review)
Review
The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and oxygen-enhanced imaging techniques to quantify regional perfusion and ventilation, respectively, in standard units of measurement. By combining these techniques into a single scan, it is also possible to quantify the local ventilation-perfusion ratio, which is the most important determinant of gas-exchange efficiency in the lung. To demonstrate potential for accurate and meaningful measurements of lung function, this technique was used to study gravitational gradients of ventilation, perfusion, and ventilation-perfusion ratio in healthy subjects, yielding quantitative results consistent with expected regional variations. Such techniques can also be applied in the time domain, providing new tools for studying temporal dynamics of lung function. Temporal ASL measurements showed increased spatial-temporal heterogeneity of pulmonary blood flow in healthy subjects exposed to hypoxia, suggesting sensitivity to active control mechanisms such as hypoxic pulmonary vasoconstriction, and illustrating that to fully examine the factors that govern lung function it is necessary to consider temporal as well as spatial variability. Further development to increase spatial coverage and improve robustness would enhance the clinical applicability of these new functional imaging tools. In the realm of structural imaging, pulse sequence techniques such as ultrashort echo-time radial k-space acquisition, ultrafast steady-state free precession, and imaging-based diaphragm triggering can be combined to overcome the significant challenges associated with proton MRI in the lung, enabling high-quality three-dimensional imaging of the whole lung in a clinically reasonable scan time. Images of healthy and cystic fibrosis subjects using these techniques demonstrate substantial promise for non-contrast pulmonary angiography and detailed depiction of airway disease. Although there is opportunity for further optimization, such approaches to structural lung imaging are ready for clinical testing.
Topics: Humans; Imaging, Three-Dimensional; Lung; Magnetic Resonance Imaging; Protons; Pulmonary Ventilation; Time Factors
PubMed: 24990096
DOI: 10.1002/nbm.3156 -
The European Respiratory Journal Jun 2015An elevated physiological dead space, calculated from measurements of arterial CO2 and mixed expired CO2, has proven to be a useful clinical marker of prognosis both for... (Review)
Review
An elevated physiological dead space, calculated from measurements of arterial CO2 and mixed expired CO2, has proven to be a useful clinical marker of prognosis both for patients with acute respiratory distress syndrome and for patients with severe heart failure. Although a frequently cited explanation for an elevated dead space measurement has been the development of alveolar regions receiving no perfusion, evidence for this mechanism is lacking in both of these disease settings. For the range of physiological abnormalities associated with an increased physiological dead space measurement, increased alveolar ventilation/perfusion ratio (V'A/Q') heterogeneity has been the most important pathophysiological mechanism. Depending on the disease condition, additional mechanisms that can contribute to an elevated physiological dead space measurement include shunt, a substantial increase in overall V'A/Q' ratio, diffusion impairment, and ventilation delivered to unperfused alveolar spaces.
Topics: Exercise; Heart Failure; Humans; Hypertension, Pulmonary; Pulmonary Diffusing Capacity; Pulmonary Gas Exchange; Pulmonary Ventilation; Respiratory Dead Space; Respiratory Distress Syndrome; Ventilation-Perfusion Ratio
PubMed: 25395032
DOI: 10.1183/09031936.00137614 -
American Journal of Respiratory and... Mar 2023
Topics: Humans; Lung; Respiration, Artificial; Respiratory Mechanics; Pulmonary Ventilation
PubMed: 36395483
DOI: 10.1164/rccm.202211-2044LE