scholarly journals Lung Ventilation and Perfusion in Prone and Supine Postures with Reference to Anesthetized and Mechanically Ventilated Healthy Volunteers

2010 ◽  
Vol 112 (3) ◽  
pp. 682-687 ◽  
Author(s):  
Sven Nyrén ◽  
Peter Radell ◽  
Sten G. E. Lindahl ◽  
Margareta Mure ◽  
Johan Petersson ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
General Anesthesia ◽  
Healthy Volunteers ◽  
Photon Emission ◽  
Vertical Direction ◽  
Emission Computed Tomography ◽  
Mechanically Ventilated ◽  
Supine Posture ◽  
Controlled Mechanical Ventilation ◽  
Prone Posture

Background The literature on ventilation (V) and lung perfusion (Q) distributions during general anesthesia and controlled mechanical ventilation in supine and prone position is contradictory. The authors aimed to investigate whether V, Q, and ventilation to perfusion ratio (V/Q ratio) matching in anesthetized and mechanically ventilated volunteers are gravity dependent irrespective of posture. Methods Seven healthy volunteers were studied at two different occasions during general anesthesia and controlled mechanical ventilation. One occasion studied ventral to dorsal V and Q distributions in the supine posture and the other in the prone posture. Imaging was performed in supine posture at both occasions. A dual radiotracer technique and single photon emission computed tomography were used. V and Q were simultaneously tagged with Tc-Technegas (Tetley Manufacturing Ltd., Sydney, Australia) and In-labeled macroaggregates of human albumin (TechneScan LyoMAA, Mallinckrodt Medica, Petten, The Netherlands), respectively. Results No differences in V between postures were observed. Q differed between postures, being more uniform over different lung regions in prone posture and dependent in supine posture. The contribution of the vertical direction to the total V/Q ratio heterogeneity was larger in supine (31.4%) than in prone (16.4%) (P = 0.0639, two-tailed, paired t test) posture. Conclusions During mechanical ventilation, prone posture favors a more evenly distributed Q between lung regions. V distribution is independent of posture. This results in a tendency toward lower V/Q gradients in the ventral to dorsal direction in prone compared with supine posture.

Positive End-expiratory Pressure Redistributes Regional Blood Flow and Ventilation Differently in Supine and Prone Humans

2010 ◽  
Vol 113 (6) ◽  
pp. 1361-1369 ◽  
Author(s):  
Johan Petersson ◽  
Malin Ax ◽  
Joana Frey ◽  
Alejandro Sánchez-Crespo ◽  
Sten G. E. Lindahl ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Blood Flow ◽  
Single Photon ◽  
Regional Blood Flow ◽  
Photon Emission ◽  
Normal Subjects ◽  
Emission Computed Tomography ◽  
Positive End Expiratory Pressure ◽  
Regional Lung ◽  
Lung Blood Flow

Background Animal studies have demonstrated an interaction between posture and the effect of positive end-expiratory pressure (PEEP) on regional ventilation and lung blood flow. The aim of this study was to explore this interaction in humans. Methods Regional lung blood flow and ventilation were compared between mechanical ventilation with and without PEEP in the supine and prone postures. Six normal subjects were studied in each posture. Regional lung blood flow was marked with In-labeled macroaggregates and ventilation with Technegas (Tc). Radiotracer distributions were mapped using quantitative single-photon emission computed tomography. Results In supine subjects, PEEP caused a similar redistribution of both ventilation and blood flow toward dependent (dorsal) lung regions, resulting in little change in the V/Q correlation. In contrast, in prone subjects, the redistribution toward dependent (ventral) regions was much greater for blood flow than for ventilation, causing increased V/Q mismatch. Without PEEP, the vertical ventilation-to-perfusion gradient was less in prone postures than in supine, but with PEEP, the gradient was similar. Conclusions During mechanical ventilation of healthy volunteers, the addition of PEEP, 10 cm H2O, causes redistribution of both lung blood flow and ventilation, and the effect is different between the supine and prone postures. Our results suggest that the addition of PEEP in prone might be less beneficial than in supine and that optimal use of the prone posture requires reevaluation of the applied PEEP.

scholarly journals Relationship Between Chronic Kidney Disease and Sarcopenia

2021 ◽  
Author(s):  
Ming-Dian Yu ◽  
Hui-Zhen Zhang ◽  
Yu Zhang ◽  
Sheng-Ping Yang ◽  
Miao Lin ◽  
...  
Keyword(s):  
Chronic Kidney Disease ◽  
Kidney Disease ◽  
Healthy Volunteers ◽  
Photon Emission ◽  
Multivariate Logistic Regression Analysis ◽  
Control Group ◽  
Emission Computed Tomography ◽  
Ckd Progression ◽  
Skeletal Muscle Index ◽  
The Relationship

Abstract Few studies have investigated the relationship between sarcopenia and mild to moderate renal decline. This study aimed to investigate the relationship between chronic kidney disease (CKD) and sarcopenia. In total, 123 patients hospitalized with CKD and 57 healthy volunteers who underwent physical examination during the same period (control group) were analyzed. Body compositions were measured by dual-energy X-ray absorptiometry, and the relative appendicular skeletal muscle index (RASMI) was calculated. Muscular strength was evaluated using a pinch meter. Walking speed within 6 m was measured for muscular function assessment. Single-photon emission computed tomography was performed to measure the glomerular filtration rate (GFR) of CKD patients, who were then divided into CKD1 (55 patients in CKD stages 1 and 2) and CKD2 (68 patients in CKD stages 3-5). The incidence rates of sarcopenia were significantly higher in the CKD1 (40.0%) and CKD2 (55.9%) groups than in the control group (19.3%) (P<0.05). RASMI showed a downward trend with CKD progression (P=0.001). Multivariate logistic regression analysis showed that age and CKD progression were independent risk factors for sarcopenia. The morbidity of sarcopenia was significantly greater in CKD patients than in healthy volunteers, and the degree of muscle loss was closely related to CKD progression.

Mechanical ventilation results in progressive contractile dysfunction in the diaphragm

2002 ◽  
Vol 92 (5) ◽  
pp. 1851-1858 ◽  
Author(s):  
Scott K. Powers ◽  
R. Andrew Shanely ◽  
Jeff S. Coombes ◽  
Thomas J. Koesterer ◽  
Michael McKenzie ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Spontaneous Breathing ◽  
Contractile Function ◽  
Control Group ◽  
Contractile Dysfunction ◽  
Sprague Dawley ◽  
Short Term ◽  
Mechanically Ventilated ◽  
Sprague Dawley Rats ◽  
Controlled Mechanical Ventilation

These experiments tested the hypothesis that a relatively short duration of controlled mechanical ventilation (MV) will impair diaphragmatic maximal specific force generation (specific Po) and that this force deficit will be exacerbated with increased time on the ventilator. To test this postulate, adult Sprague-Dawley rats were randomly divided into one of six experimental groups: 1) control ( n = 12); 2) 12 h of MV ( n = 4); 3) 18 h of MV ( n = 4); 4) 18 h of anesthesia and spontaneous breathing ( n = 4); 5) 24 h of MV ( n = 7); and 6) 24 h of anesthesia and spontaneous breathing ( n = 4). MV animals were anesthetized, tracheostomized, and ventilated with room air. Animals in the control group were acutely anesthetized but were not exposed to MV. Animals in two spontaneous breathing groups were anesthetized and breathed spontaneously for either 18 or 24 h. No differences ( P > 0.05) existed in diaphragmatic specific Po between control and the two spontaneous breathing groups. In contrast, compared with control, all durations of MV resulted in a reduction ( P < 0.05) in diaphragmatic specific tension at stimulation frequencies ranging from 15 to 160 Hz. Furthermore, the MV-induced decrease in diaphragmatic specific Po was time dependent, with specific Po being ∼18 and ∼46% lower ( P < 0.05) in animals mechanically ventilated for 12 and 24 h, respectively. These data support the hypothesis that relatively short-term MV impairs diaphragmatic contractile function and that the magnitude of MV-induced force deficit increases with time on the ventilator.

scholarly journals Inspiratory Efforts, Positive End-Expiratory Pressure, and External Resistances Influence Intraparenchymal Gas Redistribution in Mechanically Ventilated Injured Lungs

2021 ◽  
Vol 11 ◽  
Author(s):  
Mariangela Pellegrini ◽  
Göran Hedenstierna ◽  
Anders Sune Larsson ◽  
Gaetano Perchiazzi
Keyword(s):  
Mechanical Ventilation ◽  
Spontaneous Breathing ◽  
Distress Syndrome ◽  
Inspiratory Flow ◽  
High Peep ◽  
Swine Model ◽  
Positive End Expiratory Pressure ◽  
Mechanically Ventilated ◽  
Airway Opening ◽  
Controlled Mechanical Ventilation

BackgroundPotentially harmful lung overstretch can follow intraparenchymal gas redistribution during mechanical ventilation. We hypothesized that inspiratory efforts characterizing spontaneous breathing, positive end-expiratory pressure (PEEP), and high inspiratory resistances influence inspiratory intraparenchymal gas redistribution.MethodsThis was an experimental study conducted on a swine model of mild acute respiratory distress syndrome. Dynamic computed tomography and respiratory mechanics were simultaneously acquired at different PEEP levels and external resistances, during both spontaneous breathing and controlled mechanical ventilation. Images were collected at two cranial–caudal levels. Delta-volume images (ΔVOLs) were obtained subtracting pairs of consecutive inspiratory images. The first three ΔVOLs, acquired for each analyzed breath, were used for the analysis of inspiratory pendelluft defined as intraparenchymal gas redistribution before the start of inspiratory flow at the airway opening. The following ΔVOLs were used for the analysis of gas redistribution during ongoing inspiratory flow at the airway opening.ResultsDuring the first flow-independent phase of inspiration, the pendelluft of gas was observed only during spontaneous breathing and along the cranial-to-caudal and nondependent-to-dependent directions. The pendelluft was reduced by high PEEP (p &lt; 0.04 comparing PEEP 15 and PEEP 0 cm H2O) and low external resistances (p &lt; 0.04 comparing high and low external resistance). During the flow-dependent phase of inspiration, two patterns were identified: (1) gas displacing characterized by large gas redistribution areas; (2) gas scattering characterized by small, numerous areas of gas redistribution. Gas displacing was observed at low PEEP, high external resistances, and it characterized controlled mechanical ventilation (p &lt; 0.01, comparing high and low PEEP during controlled mechanical ventilation).ConclusionsLow PEEP and high external resistances favored inspiratory pendelluft. During the flow-dependent phase of the inspiration, controlled mechanical ventilation and low PEEP and high external resistances favored larger phenomena of intraparenchymal gas redistribution (gas displacing) endangering lung stability.

Sign in / Sign up

Export Citation Format

Share Document