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Experimental Physiology Jul 2022What is the central question of this study? How does the interaction between posture and gravity affect the stresses on the lung, particularly in highly inflated...
NEW FINDINGS
What is the central question of this study? How does the interaction between posture and gravity affect the stresses on the lung, particularly in highly inflated gravitationally non-dependent regions, which are potentially vulnerable to increased mechanical stress and injury? What is the main finding and its importance? Changes in stress attributable to gravity are not well characterized between postures. Using a new metric of gravitational stress, we show that regions of the lung near maximal inflation have the greatest gravitational stresses while supine, but not while prone. In simulations of increased lung weight consistent with severe pulmonary oedema, the prone lung has lower gravitational stress in vulnerable, non-dependent regions, potentially protecting them from overinflation and injury.
ABSTRACT
Prone posture changes the gravitational vector, and potentially the stress induced by tissue deformation, because a larger lung volume is gravitationally dependent when supine, but non-dependent when prone. To evaluate this, 10 normal subjects (six male and four female; age, means ± SD = 27 ± 6 years; height, 171 ± 9 cm; weight, 69 ± 13 kg; forced expiratory volume in the first second/forced expiratory volume as a percentage of predicted, 93 ± 6%) were imaged at functional residual capacity, supine and prone, using magnetic resonance imaging, to quantify regional lung density. We defined regional gravitational stress as the cumulative weight, per unit area, of the column of lung tissue below each point. Gravitational stress was compared between regions of differing inflation to evaluate differences between highly stretched, and thus potentially vulnerable, regions and less stretched lung. Using reference density values for normal lungs at total lung capacity (0.10 ± 0.03 g/ml), regions were classified as highly inflated (density < 0.13 g/ml, i.e., close to total lung capacity), intermediate (0.13 ≤ density < 0.16 g/ml) or normally inflated (density ≥ 0.16 g/ml). Gravitational stress differed between inflation categories while supine (-1.6 ± 0.3 cmH O highly inflated; -1.4 ± 0.3 cmH O intermediate; -1.1 ± 0.1 cmH O normally inflated; P = 0.05) but not while prone (-1.4 ± 0.2 cmH O highly inflated; -1.3 ± 0.2 cmH O intermediate; -1.3 ± 0.1 cmH O normally inflated; P = 0.39), and increased more with height from dependent lung while supine (-0.24 ± 0.02 cmH O/cm supine; -0.18 ± 0.04 cmH O/cm prone; P = 0.05). In simulated severe pulmonary oedema, the gradient in gravitational stress increased in both postures (all P < 0.0001), was greater in the supine posture than when prone (-0.57 ± 0.21 cmH O/cm supine; -0.34 ± 0.16 cmH O/cm prone; P = 0.0004) and was similar to the gradient calculated from supine computed tomography images in a patient with acute respiratory distress syndrome (-0.51 cmH O/cm). The non-dependent lung has greater gravitational stress while supine and might be protected while prone, particularly in the presence of oedema.
Topics: Edema; Female; Humans; Lung; Male; Prone Position; Pulmonary Edema; Supine Position
PubMed: 33347661
DOI: 10.1113/EP089037 -
Critical Care Medicine Jan 2023Prone positioning and venovenous extracorporeal membrane oxygenation (ECMO) are both useful interventions in acute respiratory distress syndrome (ARDS). Combining the...
OBJECTIVES
Prone positioning and venovenous extracorporeal membrane oxygenation (ECMO) are both useful interventions in acute respiratory distress syndrome (ARDS). Combining the two therapies is feasible and safe, but the effectiveness is not known. Our objective was to evaluate the potential survival benefit of prone positioning in venovenous ECMO patients cannulated for COVID-19-related ARDS.
DESIGN
Retrospective analysis of a multicenter cohort.
PATIENTS
Patients on venovenous ECMO who tested positive for severe acute respiratory syndrome coronavirus 2 by reverse transcriptase polymerase chain reaction or with a diagnosis on chest CT were eligible.
INTERVENTIONS
None.
MEASUREMENTS AND MAIN RESULTS
All patients on venovenous ECMO for respiratory failure in whom prone position status while on ECMO and in-hospital mortality were known were included. Of 647 patients in 41 centers, 517 were included. Median age was 55 (47-61), 78% were male and 95% were proned before cannulation. After cannulation, 364 patients (70%) were proned and 153 (30%) remained in the supine position for the whole ECMO run. There were 194 (53%) and 92 (60%) deaths in the prone and the supine groups, respectively. Prone position on ECMO was independently associated with lower in-hospital mortality (odds ratio = 0.49 [0.29-0.84]; p = 0.010). In 153 propensity score-matched pairs, mortality rate was 49.7% in the prone position group versus 60.1% in the supine position group (p = 0.085). Considering only patients alive at decannulation, propensity-matched proned patients had a significantly lower mortality rate (22.4% vs 37.8%; p = 0.029) than nonproned patients.
CONCLUSIONS
Prone position may be beneficial in patients supported by venovenous ECMO for COVID-19-related ARDS but more data are needed to draw definitive conclusions.
Topics: Humans; Male; Middle Aged; Female; Extracorporeal Membrane Oxygenation; Prone Position; Retrospective Studies; COVID-19; Respiratory Distress Syndrome
PubMed: 36519982
DOI: 10.1097/CCM.0000000000005714 -
Radiotherapy and Oncology : Journal of... Dec 2021Accelerated partial breast irradiation (APBI) may benefit from the MR-Linac for target definition, patient setup, and motion monitoring. In this planning study, we...
BACKGROUND AND PURPOSE
Accelerated partial breast irradiation (APBI) may benefit from the MR-Linac for target definition, patient setup, and motion monitoring. In this planning study, we investigated whether prone or supine position is dosimetrically beneficial for APBI on an MR-Linac and we evaluated patient comfort.
MATERIALS AND METHODS
Twenty-patients (9 postoperative, 11 preoperative) with a DCIS or breast tumor <3 cm underwent 1.5 T MRI in prone and supine position. The tumor or tumor bed was delineated as GTV and a 2 cm CTV-margin and 0.5 cm PTV-margin were added. 1.5 T MR-Linac treatment plans (5 × 5.2 Gy) with 11 beams were created for both positions in each patient. We evaluated the number of plans that achieved the planning constraints and performed a dosimetric comparison between prone and supine position using the Wilcoxon signed-rank test (p-value <0.01 for significance). Patient experience during scanning was evaluated with a questionnaire.
RESULTS
All 40 plans met the target coverage and OAR constraints, regardless of position. Heart D was not significantly different (1.07 vs. 0.79 Gy, p-value: 0.027). V5Gy to the ipsilateral lung (4.4% vs. 9.8% median, p-value 0.009) and estimated delivery time (362 vs. 392 s, p-value: 0.003) were significantly lower for prone position. PTV coverage and dose to other OAR were comparable between positions. The majority of patients (13/20) preferred supine position.
CONCLUSION
APBI on the MR-Linac is dosimetrically feasible in prone and supine position. Mean heart dose was similar in both positions. Ipsilateral lung V5Gy was lower in prone position.
Topics: Breast Neoplasms; Female; Humans; Magnetic Resonance Imaging; Prone Position; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Supine Position
PubMed: 34774649
DOI: 10.1016/j.radonc.2021.11.001 -
Critical Care Medicine Oct 2021It is not known how lung injury progression during mechanical ventilation modifies pulmonary responses to prone positioning. We compared the effects of prone positioning...
OBJECTIVES
It is not known how lung injury progression during mechanical ventilation modifies pulmonary responses to prone positioning. We compared the effects of prone positioning on regional lung aeration in late versus early stages of lung injury.
DESIGN
Prospective, longitudinal imaging study.
SETTING
Research imaging facility at The University of Pennsylvania (Philadelphia, PA) and Medical and Surgical ICUs at Massachusetts General Hospital (Boston, MA).
SUBJECTS
Anesthetized swine and patients with acute respiratory distress syndrome (acute respiratory distress syndrome).
INTERVENTIONS
Lung injury was induced by bronchial hydrochloric acid (3.5 mL/kg) in 10 ventilated Yorkshire pigs and worsened by supine nonprotective ventilation for 24 hours. Whole-lung CT was performed 2 hours after hydrochloric acid (Day 1) in both prone and supine positions and repeated at 24 hours (Day 2). Prone and supine images were registered (superimposed) in pairs to measure the effects of positioning on the aeration of each tissue unit. Two patients with early acute respiratory distress syndrome were compared with two patients with late acute respiratory distress syndrome, using electrical impedance tomography to measure the effects of body position on regional lung mechanics.
MEASUREMENTS AND MAIN RESULTS
Gas exchange and respiratory mechanics worsened over 24 hours, indicating lung injury progression. On Day 1, prone positioning reinflated 18.9% ± 5.2% of lung mass in the posterior lung regions. On Day 2, position-associated dorsal reinflation was reduced to 7.3% ± 1.5% (p < 0.05 vs Day 1). Prone positioning decreased aeration in the anterior lungs on both days. Although prone positioning improved posterior lung compliance in the early acute respiratory distress syndrome patients, it had no effect in late acute respiratory distress syndrome subjects.
CONCLUSIONS
The effects of prone positioning on lung aeration may depend on the stage of lung injury and duration of prior ventilation; this may limit the clinical efficacy of this treatment if applied late.
Topics: Adult; Aged; Boston; Female; Humans; Longitudinal Studies; Lung Injury; Male; Middle Aged; Pennsylvania; Positive-Pressure Respiration; Prone Position; Prospective Studies; Treatment Outcome
PubMed: 33938714
DOI: 10.1097/CCM.0000000000005071 -
Critical Care (London, England) Aug 2021This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at ... (Review)
Review
This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2021 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from https://link.springer.com/bookseries/8901 .
Topics: Extracorporeal Membrane Oxygenation; Humans; Intensive Care Units; Patient Positioning; Prone Position; Respiratory Distress Syndrome; Survival Analysis
PubMed: 34461971
DOI: 10.1186/s13054-021-03675-6 -
Medicina Clinica Apr 2021In December 2019, Wuhan, China, experienced an outbreak of coronavirus disease 2019 (COVID-19). Some patients admitted to our hospital were treated with early prone... (Observational Study)
Observational Study
OBJECTIVE
In December 2019, Wuhan, China, experienced an outbreak of coronavirus disease 2019 (COVID-19). Some patients admitted to our hospital were treated with early prone positioning (PP). Here, we analyzed its clinical significance.
METHODS
This was a retrospective observational study. We defined the early PP group as mild COVID-19 patients who were placed into a prone position within 24h of admission; others served as the control group. We recorded basic data and outcomes of early PP and compared the results to those of controls.
RESULTS
After 1 day of treatment, oxygenation was greater in the early PP group than in the control group (P/F: 421.6±39.74 vs. 382.1±38.84mmHg [1mmHg=0.133kPa], p<0.01). And early PP group spent less total time in prone position (11.1±4.17 vs. 16.9±5.20 days, p<0.01), and required shorter hospitalization duration (12.2±4.49 vs. 23.2±4.83 days, p<0.001).
CONCLUSIONS
Early PP treatment can improve hypoxia and shorten the prone position time and hospitalization duration in mild COVID-19 patients. It is a potential clinically applicable intervention.
Topics: Adult; COVID-19; China; Female; Humans; Male; Middle Aged; Patient Positioning; Prone Position
PubMed: 33478810
DOI: 10.1016/j.medcli.2020.11.036 -
Chest Oct 2022
Topics: COVID-19; Humans; Patient Positioning; Prone Position; Respiration, Artificial; SARS-CoV-2
PubMed: 36210097
DOI: 10.1016/j.chest.2022.06.031 -
Enfermeria Intensiva 2023To identify adverse events related to prone positioning in COVID-19 patients with severe disease and acute respiratory distress syndrome, to analyze the risk factors...
OBJECTIVE
To identify adverse events related to prone positioning in COVID-19 patients with severe disease and acute respiratory distress syndrome, to analyze the risk factors associated with the development of anterior pressure ulcers, to determine whether the recommendation of prone positioning is associated with improved clinical outcomes.
METHODS
Retrospective study performed in 63 consecutive patients with COVID-19 pneumonia admitted to intensive care unit on invasive mechanical ventilation and treated with prone positioning between March and April 2020. Association between prone-related pressure ulcers and selected variables was explored by the means of logistic regression.
RESULTS
A total of 139 proning cycles were performed. The mean number of cycles were 2 [1-3] and the mean duration per cycle was of 22h [15-24]. The prevalence of adverse events this population was 84.9 %, being the physiologic ones (i.e., hypo/hypertension) the most prevalent. 29 out of 63 patients (46%) developed prone-related pressure ulcers. The risk factors for prone-related pressure ulcers were older age, hypertension, levels of pre-albumin <21mg/dl, the number of proning cycles and severe disease. We observed a significant increase in the PaO/FiO at different time points during the prone positioning, and a significant decrease after it.
CONCLUSIONS
There is a high incidence of adverse events due to PD, with the physiological type being the most frequent. The identification of the main risk factors for the development of prone-related pressure ulcers will help to prevent the occurrence of these lesions during the prone positioning. Prone positioning offered an improvement in the oxygenation in these patients.
Topics: Humans; Respiration, Artificial; COVID-19; Prone Position; Pressure Ulcer; Retrospective Studies; Respiratory Distress Syndrome; Hypertension
PubMed: 36934077
DOI: 10.1016/j.enfie.2022.09.002 -
European Journal of Pediatrics Oct 2023To analyze the optimal lumbar puncture position in infants. A systematic review and meta-analysis. Infants (age < 1 year). December 2022 in PubMed, Scopus, and... (Meta-Analysis)
Meta-Analysis
To analyze the optimal lumbar puncture position in infants. A systematic review and meta-analysis. Infants (age < 1 year). December 2022 in PubMed, Scopus, and Web of Science. Randomized controlled trials focusing on lumbar puncture positions were included. Other lumbar puncture position than standard lateral decubitus position. First puncture success and overall success rate. Secondary outcome was desaturation during puncture and procedure-related harms. Risk of bias 2.0 assessment was performed. Outcomes are reported as risk ratios (RR) with 95% confidence intervals (CI). We screened 225 abstracts, and six studies were included. Four studies compared sitting position, one study head elevated lateral position, and one study prone position to lateral position. Risk of bias was high in two studies. First puncture success rate in sitting position (RR 1.00, CI: 0.78-1.18; 2 studies) and overall success rate in sitting position were similar to lateral position (RR 0.97, CI: 0.87-1.17; 3 studies). First attempt success rate was higher in elevated lateral position (RR 1.48, CI: 1.14-1.92; 1 study) and in prone position (RR 1.09, CI: 1.00-1.17; 1 study). Conclusion: Sitting position seems to be equally effective in terms of first attempt and overall success in lumbar puncture than standard lateral position. Elevated lateral position and prone positions had better first attempt success than standard lateral position, but these were assessed only in one study each and thus further studies in these positions are needed. Trial registration: This review was registered in PROSPERO. ID: CRD42022382953. What is Known: • Success rate in lumbar puncture has been poor and first attempt success rate has varied between 50 to 80% in literature. • Optimal lumbar puncture positions for infants have been debated between sitting and lateral decubitus position mostly. What is New: • This is the first meta-analysis focused on lumbar puncture positions in infants, and it found that sitting position was equal to standard lateral position. • Prone position and head elevated lateral positions had higher first puncture success rates, but these were assessed both only in one study, which creates uncertainty to the finding.
Topics: Humans; Infant; Spinal Puncture; Patient Positioning; Prone Position
PubMed: 37540241
DOI: 10.1007/s00431-023-05137-3 -
Canadian Respiratory Journal 2017Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia.... (Review)
Review
Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO) provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation.
Topics: Extracorporeal Membrane Oxygenation; Humans; Prone Position; Respiration; Respiration, Artificial; Respiratory Insufficiency; Ventilator Weaning
PubMed: 28127231
DOI: 10.1155/2017/1783857