Quantification of regional V/Q ratios in humans by use of PET. II. Procedure and normal values
57
Citation
0
Reference
10
Related Paper
Citation Trend
Abstract:
Regional measurements of tissue isotope concentration, made using positron emission tomography (PET), allow tracer models to be used in a quantitative manner to provide topographic distributions of many structural and functional parameters, each derived for the same well-defined lung element. In this paper we describe a technique to measure regional ventilation-perfusion ratios (V/Q), in absolute units, by use of PET and the continuous intravenous infusion of an inert gas isotope, 13N, and report on measurements made in 12 normal subjects (4 smokers). Data were obtained from a single lung section (slice thickness, 1.7 cm full width at half-maximum response to a line source) at the level of the right ventricle in the supine posture during quiet breathing. For the 12 subjects, volume-weighted mean values of V/Q, averaged over individual right and left lung fields, ranged from 0.50 to 1.29. Analysis of these means showed no difference between lungs: right, 0.80 +/- 0.23 SD; left, 0.76 +/- 0.20 SD. Topographically, a systematic fall of V/Q in the ventrodorsal direction was observed in eight of the subjects (mean ventrodorsal difference 0.39, range 0.19–0.90), whereas two showed a clear increase toward dependent lung regions (range 0.16–0.26). Seven of the subjects with a falling ventrodorsal V/Q gradient also exhibited discrete regions of low V/Q at the dorsal lung border. We conclude that, in normal subjects, ventilation and perfusion are generally well matched in the supine posture, but isolated mismatching often occurs in dependent lung regions.Keywords:
Supine position
Supine position
Prone position
Position (finance)
Cite
Citations (1)
The relative value of prone and supine filming in excretory urography was prospectively evaluated in 100 unselected, adult, high-dose urograms. The supine radiographs were superior or equal to prone radiographs in all cases. Significant findings were limited to the supine radiographs in six cases. Findings were seen on both supine and prone radiographs, but the supine radiograph was clearly better in nine cases. Major urinary structures were shown to better advantage on supine films, and the prone film was subject to radiographer error in a higher number of cases.
Supine position
Prone position
Cite
Citations (3)
Gravity is known to influence the mechanical behavior of the lung and chest wall. However, the effect of sustained microgravity (mu G) on lung volumes has not been reported. Pulmonary function tests were performed by four subjects before, during, and after 9 days of mu G exposure. Ground measurements were made in standing and supine postures. Tests were performed using a bag-in-box-and-flowmeter system and a respiratory mass spectrometer. Measurements included functional residual capacity (FRC), expiratory reserve volume (ERV), residual volume (RV), inspiratory and expiratory vital capacities (IVC and EVC), and tidal volume (VT). Total lung capacity (TLC) was derived from the measured EVC and RV values. With preflight standing values as a comparison, FRC was significantly reduced by 15% (approximately 500 ml) in mu G and 32% in the supine posture. ERV was reduced by 10–20% in mu G and decreased by 64% in the supine posture. RV was significantly reduced by 18% (310 ml) in mu G but did not significantly change in the supine posture compared with standing. IVC and EVC were slightly reduced during the first 24 h of mu G but returned to 1-G standing values within 72 h of mu G exposure. IVC and EVC in the supine posture were significantly reduced by 12% compared with standing. During mu G, VT decreased by 15% (approximately 90 ml), but supine VT was unchanged compared with preflight standing values. TLC decreased by approximately 8% during mu G and in the supine posture compared with preflight standing. The reductions in FRC, ERV, and RV during mu G are probably due to the cranial shift of the diaphragm, an increase in intrathoracic blood volume, and more uniform alveolar expansion.
Supine position
Residual volume
Cite
Citations (104)
Supine position
Prone position
Body surface area
Cite
Citations (1)
To investigate how prone and supine redistribution of a patient's adipose tissue affects the distance from skin to the renal collecting system.There were 48 patients who underwent CT intravenous urography with both supine and prone scans. The distance between skin and the posterior lower pole calix was measured in both positions. The difference was calculated using paired t tests. Subgroup analyses were conducted for patients with a body mass index (BMI) ≥ 28 and BMI ≥ 30.In all patients, the mean distance between skin and the posterior lower pole calix was 9.9 ± 0.3 cm and 8.7 ± 0.3 cm for patients supine and prone, respectively (P < 0.01). Patients with a BMI ≥ 28 had a mean distance of 10.6 ± 0.3 cm and 8.8 ± 0.3 cm in supine and prone positions, respectively (P < 0.01), while patients with BMI ≥ 30 had a mean distance of 11.3 ± 0.3 cm and 9.3 ± 0.3 cm (P < 0.01). Three patients had a BMI > 39 and exhibited differences in skin to the posterior lower pole calix ≥ 3.2 cm between supine and prone positioning. Coefficient of determination analysis for supine minus prone tract length yielded R(2) = 0.70895.The distance between skin and the renal collecting system is decreased in the prone position when compared with the supine position. This difference increases with the patient's BMI and is further accentuated in morbidly obese patients. In these obese patients, the difference when lying prone can exceed >4 cm.
Supine position
Prone position
Body position
Cite
Citations (2)
Quasi-static pressure-volume curves and single-breath nitrogen washouts were performed simultaneously on eight anesthetized horses (average body wt = 485 kg) in left lateral, right lateral, prone, and supine postures (sequence randomized). The shift from prone to lateral or supine posture decreased expiratory reserve volume (ERV), vital capacity (VC), residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC); RV and FRC expressed as %TLC were unchanged, suggesting that in the lateral and supine postures a significant portion of the lung volume was not recruited by VC maneuvers. Phase III slope increased from 0.13 %N2/l in prone horses to 0.34 %N2/l in the lateral and supine positions. The onset of phase IV was not significantly different from FRC in the prone or laterally recombent animal, but exceeded FRC in the supine horse. The sequence of body positions had no effect on any of our results indicating that all changes in lung volumes and regional asynchronous ventilation c;n be reversed by placing the horse in the prone posture. The reduction in lung volume and increased asynchronous ventilation in the lateral and supine horse suggests that impaired gas exchange in anesthetized horses is predominantly related to posture, and not general anesthesia.
Supine position
Prone position
Expiration
Cite
Citations (81)
We studied the effect of a postural change from the erect to the supine position on the unevenness of pulmonary ventilation in six normal subjects. Static pressure-volume curves had a similar shape in both positions but the supine curves were shifted such that all transpulmonary pressures were 5–8 cmH2O lower. Dynamic compliance (Cdyn) was measured in seated and supine postures at functional residual capacity (FRC) and also while the seated subjects maintained end-expiratory lung volume at the level of supine FRC. Frequency dependence of Cdyn increased relative to that measured in the seated position at FRC when the subject remained seated but decreased his lung volume, or when he assumed the supine posture. There was no significant difference between Cdyn measured in the supine posture and in the seated at supine FRC. We conclude that the increased frequency dependence seen in the supine posture is largely attributed to the associated decrease of lung volume rather than to position per se.
Supine position
Pulmonary compliance
Body position
Transpulmonary pressure
Residual volume
Cite
Citations (20)
Background: Several factors are associated with successful treatment of mild to moderate OSA with a mandibular advancement device (MAD). Data about the predictive value of supine-dependent OSA are conflicting. Very little literature is available about the predictive value of the AHI in supine position. Here, we investigate supine dependent OSA and AHI in supine position as predictors of successful treatment with MAD. Methods: From January 1, 2015 until December 31, 2017, patients with OSA with an AHI >5 and <30 receiving an MAD were included. Successful treatment was defined as a decrease of AHI with MAD of at least 50% and AHI <10/hour. Results: 118 patients were included, 78.8% had supine dependent OSA, 21.2% had non-supine dependent OSA. Successful treatment was achieved in 44% of the patients with supine dependent OSA, versus 28% of patients with non-supine dependent OSA, p=0.12. With linear regression, the only independent predictor of success was BMI. No relations were found between success and supine dependent OSA or AHI in supine position. Conclusion: In our cohort, supine dependent and AHI in supine position were not predicting factors for successful treatment of mild to moderate OSA with MAD.
Supine position
Cite
Citations (0)
The relation between the nystagmus in the supine position and the affected side in patients with horizontal semicircular canal benign paroxysmal positional vertigo (HC-BPPV) is studied because nystagmus is frequently observed in the supine position before the patient assumes the supine right-ear-down and left-ear-down positions. Thirty patients with HC-BPPV were examined using electronystagmography (ENG) in the supine, supine right-ear-down and supine left-ear-down positions, and the relation between the direction of nystagmus in the supine position and the affected side was studied. The direction of nystagmus in the supine position was consistent with the affected side in 11 of 18 (61%) patients with cupulolithiasis and in 7 of 12 (58%) patients with canalithiasis. ENG findings in HC-BPPV patients with cupulolithiasis suggested that the cupula is oriented laterally in the HC. Other ENG findings in HC-BPPV patients with canalithiasis suggested that otoconia are located in the medial position of the HC. These findings are helpful to infer the affected side in the patient with HC-BPPV by observation of the nystagmus in the supine position before placing the patient in the supine right/left-ear-positions.
Supine position
Electronystagmography
Cite
Citations (0)
Objective: To determine the accuracy of supine and prone approaches to sonographically measured kidney dimensions. Methods: The kidney dimensions of 109 participants were sonographically determined in supine and prone patient positions. The two measurements were compared with each other using the intra-class correlation, coefficient of variation for duplicate measurements and Bland-Altman plot. The two sets of measurements were each compared with measurements from computed tomography. Results: There was a very strong agreement between kidney dimensions in supine and prone positions. There was also an agreement between kidney dimensions in supine and prone positions and computed tomography measurements. Conclusion: The kidney dimensions obtained using patient-in-supine position and patient-in-prone position approaches may be equivalent and the two approaches may be used interchangeably.
Supine position
Prone position
Position (finance)
Cite
Citations (0)