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Kreit J. Respiratory-Cardiovascular Interactions During Mechanical Ventilation: Physiology and Clinical Implications. Compr Physiol 2022; 12:3425-3448. [PMID: 35578946 DOI: 10.1002/cphy.c210003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Positive-pressure inspiration and positive end-expiratory pressure (PEEP) increase pleural, alveolar, lung transmural, and intra-abdominal pressure, which decrease right and left ventricular (RV; LV) preload and LV afterload and increase RV afterload. The magnitude and clinical significance of the resulting changes in ventricular function are determined by the delivered tidal volume, the total level of PEEP, the compliance of the lungs and chest wall, intravascular volume, baseline RV and LV function, and intra-abdominal pressure. In mechanically ventilated patients, the most important, adverse consequences of respiratory-cardiovascular interactions are a PEEP-induced reduction in cardiac output, systemic oxygen delivery, and blood pressure; RV dysfunction in patients with ARDS; and acute hemodynamic collapse in patients with pulmonary hypertension. On the other hand, the hemodynamic changes produced by respiratory-cardiovascular interactions can be beneficial when used to assess volume responsiveness in hypotensive patients and by reducing dyspnea and improving hypoxemia in patients with cardiogenic pulmonary edema. Thus, a thorough understanding of the physiological principles underlying respiratory-cardiovascular interactions is essential if critical care practitioners are to anticipate, recognize, manage, and utilize their hemodynamic effects. © 2022 American Physiological Society. Compr Physiol 12:1-24, 2022.
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Affiliation(s)
- John Kreit
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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Ji M, Ikegami T, Debru E, Easton PA. Parasternal Intercostal Function during Sustained Hypoxia. J Appl Physiol (1985) 2022; 132:622-631. [PMID: 35112930 DOI: 10.1152/japplphysiol.00771.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ventilatory response to sustained isocapnic hypoxia in adult humans and other mammals is characterized by a biphasic pattern, with attenuation of neuromotor output to the diaphragm. However, there is no a priori reason that hypoxic mediated attenuation of respiratory drive would be a common event among other respiratory muscles. At present, little is known about the function of the chest wall muscles during sustained hypoxia. As an obligatory inspiratory muscle with potential to act as a surrogate for neural drive to the relatively inaccessible costal diaphragm, parasternal intercostal has gained interest clinically: its function during a sustained hypoxic insult, as may occur in respiratory failure, warrants investigation. Therefore, in eleven chronically instrumented awake canines, we recorded simultaneously muscle length, shortening and electromyogram (EMG) activity of the parasternal chest wall inspiratory muscle, along with breathing pattern, during moderate levels of sustained isocapnic hypoxia lasting 20-25 minutes (mean 80 ± 2% oximeter oxygen saturation). Phasic inspiratory shortening and EMG activity of the parasternal intercostal was observed throughout room air and hypoxic ventilation in all animals. Temporal changes in parasternal intercostal shortening tracked the biphasic changes in ventilation during sustained hypoxia. Mean shortening and EMG activity of parasternal intercostal muscle increased significantly with initial hypoxia (P < 0.01), then markedly declined with constant hypoxia (P < 0.05). We conclude that attenuation of central neural respiratory drive extends to the primary chest wall inspiratory muscle, the parasternal intercostals, during sustained hypoxia, thus directly contributing to biphasic changes in ventilation.
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Affiliation(s)
- Michael Ji
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Tetsunori Ikegami
- Department of Emergency Medicine, Kurashiki Central Hospital, Miwa Kurashiki, Okayama, Japan
| | - Estifanos Debru
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Paul A Easton
- Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Milne S, Huvanandana J, Nguyen C, Duncan JM, Chapman DG, Tonga KO, Zimmermann SC, Slattery A, King GG, Thamrin C. Time-based pulmonary features from electrical impedance tomography demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease. J Appl Physiol (1985) 2019; 127:1441-1452. [PMID: 31556831 DOI: 10.1152/japplphysiol.00304.2019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary electrical impedance tomography (EIT) is a functional imaging technique that allows real-time monitoring of ventilation distribution. Ventilation heterogeneity (VH) is a characteristic feature of chronic obstructive pulmonary disease (COPD) and has previously been quantified using features derived from tidal variations in the amplitude of the EIT signal. However, VH may be better described by time-based metrics, the measurement of which is made possible by the high temporal resolution of EIT. We aimed 1) to quantify VH using novel time-based EIT metrics and 2) to determine the physiological relevance of these metrics by exploring their relationships with complex lung mechanics measured by the forced oscillation technique (FOT). We performed FOT, spirometry, and tidal-breathing EIT measurements in 11 healthy controls and 9 volunteers with COPD. Through offline signal processing, we derived 3 features from the impedance-time (Z-t) curve for each image pixel: 1) tE, mean expiratory time; 2) PHASE, mean time difference between pixel and global Z-t curves; and 3) AMP, mean amplitude of Z-t curve tidal variation. Distribution was quantified by the coefficient of variation (CV) and the heterogeneity index (HI). Both CV and HI of the tE and PHASE features were significantly increased in COPD compared with controls, and both related to spirometry and FOT resistance and reactance measurements. In contrast, distribution of the AMP feature showed no relationships with lung mechanics. These novel time-based EIT metrics of VH reflect complex lung mechanics in COPD and have the potential to allow real-time visualization of pulmonary physiology in spontaneously breathing subjects.NEW & NOTEWORTHY Pulmonary electrical impedance tomography (EIT) is a real-time imaging technique capable of monitoring ventilation with exquisite temporal resolution. We report novel, time-based EIT measurements that not only demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease (COPD), but also reflect oscillatory lung mechanics. These EIT measurements are noninvasive, radiation-free, easy to obtain, and provide real-time visualization of the complex pathophysiology of COPD.
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Affiliation(s)
- Stephen Milne
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Central Clinical School, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Northern Clinical School, University of Sydney, Sydney, New South Wales, Australia.,Department of Respiratory Medicine, Royal North Shore Hospital, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia.,Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jacqueline Huvanandana
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia
| | - Chinh Nguyen
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia
| | - Joseph M Duncan
- Department of Respiratory Medicine, Royal North Shore Hospital, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia
| | - David G Chapman
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Translational Airways Group, School of Life Sciences, University of Technology Sydney, Ultimo, New South Wales, Australia
| | - Katrina O Tonga
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Northern Clinical School, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine, the University of New South Wales, Kensington, New South Wales, Australia
| | - Sabine C Zimmermann
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Northern Clinical School, University of Sydney, Sydney, New South Wales, Australia.,Department of Respiratory Medicine, Royal North Shore Hospital, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia
| | - Alexander Slattery
- Department of Respiratory Medicine, Royal North Shore Hospital, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia
| | - Gregory G King
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Northern Clinical School, University of Sydney, Sydney, New South Wales, Australia.,Department of Respiratory Medicine, Royal North Shore Hospital, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia.,Centre of Excellence in Severe Asthma, New Lambton, New South Wales, Australia
| | - Cindy Thamrin
- Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.,Faculty of Medicine and Health, Central Clinical School, University of Sydney, Sydney, New South Wales, Australia
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