Pleural pressures at dorsal and ventral sites in supine and prone body positions.
Pleural pressures at dorsal and ventral sites of thorax of dog in supine and prone body positions as affected by acceleration
LUNG↗
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Respiratory changes in pleural pressures at different sites and body positions.
Respiratory changes in pleural pressures at different sites and body positions in dogs
DOG↗
Effect of gravitational and inertial forces on pleural and esophageal pressures.
Effect of posture and of gravitational and inertial forces on pleural and esophageal pressures of dogs
DOG↗
Pleural and esophageal pressures in the upright body position.
Pleural and esophageal pressure measurements recorded for anesthetized dogs supported in upright position
Banchero, N.↗
Nature of pleural space of dogs
Pleural space of dogs investigated by spheres injection of varying density and diameter, discussing sedimentation velocities
Cronin, L.↗
Effects of positive Gy acceleration on blood oxygen saturation and pleural pressure relationships in dogs breathing first air, then liquid fluorocarbon in a whole body water immersion respirator
Effects of positive Gy acceleration on blood oxygen saturation and pleural pressure relations in dogs breathing air and liquid fluorocarbons in whole body water immersion respirator
Banchero, N.↗
Regional differences in pleural and esophageal pressures in head-up and head-down positions
Dogs intrapleural and intraesophageal pressures dependence on head positions
Coulam, C. M.↗
Regional volume changes in canine lungs suspended in air
The purpose of this study was to determine the effect of the absence of a pleural pressure gradient (simulating the presumed condition found in microgravity) upon regional expansion of the lung. We attempted to produce a uniform pressure over the surface of the lung by suspending excised lungs in air. Such studies should help determine whether or not the absence of a pleural pressure gradient leads to uniform ventilation. A preparation in which there is no pleural pressure gradient should also be useful in studying non-gravitational effects on ventilation distribution.
Abbrecht, Peter H.↗
Effect of gravitational and inertial forces on vertical distribution of pulmonary blood flow
Vertical distribution of pulmonary blood flow (VDPBF) was studied, using radioactive microsphere emboli, in dogs without thoracotomy in the right decubitus position during exposure to lateral accelerations of 1, 2, 4, and 6 G. At all levels of force environment studied, an inverse linear relationship was observed between vertical height in the thorax and pulmonary blood flow (ml/min/ml lung tissue) with a decrease in flow to the most dependent region of the lung despite large increases in intravascular pressures at this site. Changes in blood flow were smallest at the mid-lung level, the hydrostatic 'balance point' for vascular and pleural pressures. These force environment-dependent changes in VDPBF are not readily explainable by the Starling resistor analog. Gravity-dependent regional differences in pleural and associated interstitial pressures, plus possible changes in vascular tone resulting from inadequate aeration of blood in the most dependent regions of the lung, probably also affect VDPBF.
Chevalier, P. A.↗
Cardiopulmonary Changes with Moderate Decompression in Rats
Sprague-Dawley rats were compressed to 616 kPa for 120 min then decompressed at 38 kPa/min to assess the cardiovascular and pulmonary responses to moderate decompression stress. In one series of experiments the rats were chronically instrumented with Doppler ultrasonic probes for simultaneous measurement of blood pressure, cardiac output, heart rate, left and right ventricular wall thickening fraction, and venous bubble detection. Data were collected at base-line, throughout the compression/decompression protocol, and for 120 min post decompression. In a second series of experiments the pulmonary responses to the decompression protocol were evaluated in non-instrumented rats. Analyses included blood gases, pleural and bronchoalveolar lavage (BAL) protein and hemoglobin concentration, pulmonary edema, BAL and lung tissue phospholipids, lung compliance, and cell counts. Venous bubbles were directly observed in 90% of the rats where immediate post-decompression autopsy was performed and in 37% using implanted Doppler monitors. Cardiac output, stroke volume, and right ventricular wall thickening fractions were significantly decreased post decompression, whereas systemic vascular resistance was increased suggesting a decrease in venous return. BAL Hb and total protein levels were increased 0 and 60 min post decompression, pleural and plasma levels were unchanged. BAL white blood cells and neutrophil percentages were increased 0 and 60 min post decompression and pulmonary edema was detected. Venous bubbles produced with moderate decompression profiles give detectable cardiovascular and pulmonary responses in the rat.
Robinson, R.↗
Validation of Ultrasound Imaging to Rule-out Thoracic Trauma on the International Space Station
Introduction: Aboard the International Space Station (ISS) an intra-thoracic injury may be disastrous to the crew member if the diagnosis is missed or even delayed. Pneumothorax and hemothorax commonly seen in trauma patients; the diagnosis is usually confirmed by chest X-ray or computed tomography. In this study, the ability of ultrasound to rule out pneumothorax by the presence "lung sliding" and hemothorax by the absence of pleural fluid was validated. Methods: The research activities were approved by the NASA Johnson Space Center Committee for the Protection of Human Subjects, and the participating crewmembers signed informed consent prior to the activity. ISS crewmembers received 2-hours of "hands on" ultrasound training 8 months prior to the on-orbit ultrasound exam. Baseline ultrasound images of the thorax were acquired on the crewmebers of Increment 8 and 9 prior to launch from Bakonur, Russia. Ultrasound examination of the thorax were performed on crewmembers at 30 day intervals (n=??) throughout their flight. Post flight images were acquired on or about landing day 10. Ultrasound images were acquired using the ISS Health Research Facility ultrasound system and examined by experts on the ground to rule out the presence of pneumothorax and hemothorax. Results: The presence of "lung sliding" which excludes pneumothorax, was seen in all subjects. The absence of pleural fluid, which excludes hemothorax was seen in all subjects. The optimal position between sonographer and patient under microgravity conditions and the amount and type of training for a non-physician crew medical officer for these procedures was also established for this procedure. Conclusion: Ultrasound can be performed on orbit under microgravity condition to rule thoracic trauma, such as pneumothorax and hemothorax.
Hamilton, Douglas R.↗
Ultrasound Evaluation of the Magnitude of Pneumothorax: A New Concept
Pneumothorax is commonly seen in trauma patients; the diagnosis is usually confirmed by radiography. Use of ultrasound for this purpose, in environments such as space flight and remote terrestrial areas where radiographic capabilities are absent, is being investigated by NASA. In this study, the ability of ultrasound to assess the magnitude of pneumothorax in a porcine model was evaluated. Sonography was performed on anesthetized pigs (avg. wt. 50 kg) in both ground-based laboratory (n = 5) and micro gravity conditions (0 g) aboard the KC-135 aircraft during parabolic flight (n = 4). Aliquots of air (50-1 OOcc) were introduced into the chest through a catheter to simulate pneumothorax. Results were video-recorded and digitized for later interpretation by radiologists. Several distinct sonographic patterns of partial lung sliding were noted, including the combination of a sliding zone with a still zone, and a "segmented" sliding zone. These "partial lung sliding" patterns exclude massive pneumothorax manifested by a complete separation of the lung from the parietal pleura. In 0 g, the sonographic picture was more diverse; 1 g differences between posterior and anterior aspects were diminished. CONCLUSIONS: Modest pneumothorax can be inferred by the ultrasound sign of "partial lung sliding". This finding, which increases the negative predictive value of thoracic ultrasound, may be attributed to intermittent pleural contact, small air spaces, or alterations in pleural lubricant. Further studies of these phenomena are warranted.
Sargsyan, Ashot E.↗
Human Cardiovascular Adaptation to Weightlessness
Entering weightlessness (0 G) induces immediately a shift of blood and fluid from the lower to the upper parts of the body inducing expansion of the cardiac chambers (Bungo et al. 1986; Charles & Lathers 1991; Videbaek & Norsk 1997). For many years the effects of sudden 0 G on central venous pressure (CVP) was discussed, and it puzzled researchers that CVP compared to the 1-G supine position decreased during the initial hours of spaceflight, when at the same time left atrial diameter increased (Buckey et al. 1996). By measuring esophageal pressure as an estimate of inter-pleural pressure, it was later shown that this pressure decreases more than CVP does during 0 G induced by parabolic flights (Videbaek & Norsk 1997). Thus, transmural CVP is increased, which distends the cardiac chambers. This unique lung-heart interaction whereby 1) inter-pleural pressure decreases and 2) central blood volume is expanded is unique for 0 G. Because transmural CVP is increased, stroke volume increases according to the law of Frank-Starling leading to an increase in cardiac output, which is maintained increased during months of 0 G in space to levels of some 25% above that of the 1-G seated position (Norsk unpublished). Simultaneously, sympathetic nervous activity is at the level of the upright 1-G posture, which is difficult to explain based on the high stroke volume and decreased blood pressure and systemic vascular resistance. This paradox should be explored and the mechanisms revealed, because it might have implications for estimating the cardiovascular risk of travelling in space.
Norsk, Peter↗
Restrictive spirometry pattern among construction trade workers
Spirometry-based studies of occupational lung disease have mostly focused on obstructive or mixed obstructive/restrictive outcomes. We wanted to determine if restrictive spirometry pattern (RSP) is associated with occupation and increased mortality. Study participants included 18,145 workers with demographic and smoking data and repeatable spirometry. The mortality analysis cohort included 15,445 workers with known vital status and cause of death through December 31, 2016. Stratified analyses explored RSP prevalence by demographic and clinical variables and trade. Log-binomial regression models explored RSP risk factors while controlling for important confounders such as smoking, obesity, and comorbidities. Cox regression models explored mortality risk by spirometry category. Prevalence of RSP was very high (28.6%). Mortality hazard ratios for RSP were 1.50 for all causes, 1.86 for cardiovascular diseases, 2.31 for respiratory diseases, and 1.66 for lung cancer. All construction trades except painters, machinists, and roofers had significantly elevated risk for RSP compared to our internal reference group. RSP was significantly associated with both parenchymal and pleural changes seen by chest X-ray. Construction trade workers are at significantly increased risk for RSP independent of obesity. Individuals with RSP are at increased risk for all-cause mortality as well as mortality attributable to respiratory diseases, cardiovascular diseases, and lung cancer. RSP deserves greater attention in occupational medicine and epidemiology.
60 APPLIED LIFE SCIENCES↗
Position-dependent regional differences in pericardial pressures
Position dependent variations in intrapericardial, pleural and esophageal pressures and cardiac output in thorax of dogs
Avasthey, P.↗
Ultrastructural changes in rat lung during long-term exposure to oxygen.
The pathogenesis of oxygen toxicity in the lung of rats was studied by electron microscopy. The following long-term effects were established: (1) a progressive destruction of the blood-air barrier beginning with the endothelial cell layer; (2) a profuse edema in the interstitial spaces in the pleural space in the alveoli and in the cytoplasm and organelles; (3) a continuing increase in the quantity and complexity of the alveolar exudate; (4) gradual hemolysis of red blood cells; and (5) eventual subsiding of the interstitial edema in surviving rats with a concomitant development of emphysema.
Harrison, G. A.↗
Finite element displacement analysis of a lung.
A method is given based on the technique of finite elements which determines theoretically the mechanical behavior of a lung-shaped body loaded by its own weight. The results of this theoretical analysis have been compared with actual measurements of alveolar size and pleural pressures in animal lungs.
Matthews, F. L.↗
Intrathoracic and venous pressure relationships during responses to changes in body position
Simultaneous end-expiratory pressures, referred to midthoracic level, in the superior and abdominal venae cavae, pericardial space, and right and left heart, were recorded without thoracotomy in three anesthetized dogs during sudden changes from supine to vertical head-up or head-down body positions. Intrathoracic and dependent great vein pressures referred to midchest level (sixth thoracic vertebra) decreased and showed simple hydrostatic gradients in either vertical position. However, a discontinuity in the large vein hydrostatic gradient occurred just distal to the superior margin of the thorax in either body position and was resumed again above this level. It is concluded that, just as the cerebrospinal fluid and intraperitoneal pressures minimize the effects of gravitational and inertial forces on the cerebral and visceral circulations, the pericardial and pleural pressures have a similar role for the heart proper.
Avasthey, P.↗