Effects of gravity on lung diffusing capacity and cardiac output in prone and supine humans.
نویسندگان
چکیده
Both in normal subjects exposed to hypergravity and in patients with acute respiratory distress syndrome, there are increased hydrostatic pressure gradients down the lung. Also, both conditions show an impaired arterial oxygenation, which is less severe in the prone than in the supine posture. The aim of this study was to use hypergravity to further investigate the mechanisms behind the differences in arterial oxygenation between the prone and the supine posture. Ten healthy subjects were studied in a human centrifuge while exposed to 1 and 5 times normal gravity (1 G, 5 G) in the anterioposterior (supine) and posterioanterior (prone) direction. They performed one rebreathing maneuver after approximately 5 min at each G level and posture. Lung diffusing capacity decreased in hypergravity compared with 1 G (ANOVA, P = 0.002); it decreased by 46% in the supine posture compared with 25% in the prone (P = 0.01 for supine vs. prone). At the same time, functional residual capacity decreased by 33 and 23%, respectively (P < 0.001 for supine vs. prone), and cardiac output by 40 and 31% (P = 0.007 for supine vs. prone), despite an increase in heart rate of 16 and 28% (P < 0.001 for supine vs. prone), respectively. The finding of a more impaired diffusing capacity in the supine posture compared with the prone at 5 G supports our previous observations of more severe arterial hypoxemia in the supine posture during hypergravity. A reduced pulmonary-capillary blood flow and a reduced estimated alveolar volume can explain most of the reduction in diffusing capacity when supine.
منابع مشابه
Lower pulmonary diffusing capacity in the prone vs. supine posture.
We evaluated the effect of prone positioning on gas-transfer characteristics in normal human subjects. Single-breath (SB) and rebreathing (RB) maneuvers were employed to assess carbon monoxide diffusing capacity (DlCO), its components related to capillary blood volume (Vc) and membrane diffusing capacity (Dm), pulmonary tissue volume (Vti), and cardiac output (Qc). Alveolar volume (Va) was sign...
متن کاملEffects of gravity and posture on the human lung
The presence of the gravitational force at the surface of Earth affects all of the organ systems in land-living creatures. The function of the lung is particularly susceptible to changes in the direction and magnitude of gravity because of the elastic structure of this organ. Gravity-dependent deformation of lung tissue in turn is an important determinant of gas transfer between the gas and the...
متن کاملComparison of the Effects of Prone and Supine Positions on Abdominal Distention in the Premature Infants Receiving Nasal Continuous Positive Airway Pressure (NCPAP)
Background: Premature infants with respiratory distress syndrome (RDS) are in dire need of respiratory support with a ventilator. However, the high tidal volume of mechanical ventilation may cause lung injury, and researchers have been concerned with the use of nasal continuous positive airway pressure (NCPAP). NCPAP has concomitant side effects, such as abdominal distention, which might disrup...
متن کاملPulmonary perfusion in the prone and supine postures in the normal human lung.
Prone posture increases cardiac output and improves pulmonary gas exchange. We hypothesized that, in the supine posture, greater compression of dependent lung limits regional blood flow. To test this, MRI-based measures of regional lung density, MRI arterial spin labeling quantification of pulmonary perfusion, and density-normalized perfusion were made in six healthy subjects. Measurements were...
متن کاملDistributions of lung ventilation and perfusion in prone and supine humans exposed to hypergravity.
When normal subjects are exposed to hypergravity [5 times normal gravity (5 G)] there is an impaired arterial oxygenation that is less severe in the prone compared with supine posture. We hypothesized that under these conditions the heterogeneities of ventilation and/or perfusion distributions would be less prominent when subjects were prone compared with supine. Expirograms from a combined reb...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of applied physiology
دوره 95 1 شماره
صفحات -
تاریخ انتشار 2003