Cardiovascular changes during underwater static and dynamic breath-hold dives in trained divers

Limited information exists concerning arterial blood pressure (BP) changes in underwater breath-hold diving. Simulated chamber dives to 50 m of freshwater (mfw) reported very high levels of invasive BP in two divers during static apnea (SA), whereas a recent study using a noninvasive subaquatic sphygmomanometer reported unchanged or mildly increased values at 10 m SA dive. In this study we investigated underwater BP changes during not only SA but, for the first time, dynamic apnea (DA) and shortened (SHT) DA in 16 trained breath-hold divers. Measurements included BP (subaquatic sphygmomanometer), ECG, and pulse oxymetry (arterial oxygen saturation, SpO?, and heart rate). BP was measured during dry conditions, at surface fully immersed (SA), and at 2 mfw (DA and SHT DA), whereas ECG and pulse oxymetry were measured continuously. We have found significantly higher mean arterial pressure (MAP) values in SA (～40%) vs. SHT DA (～30%). Postapneic recovery of BP was slightly slower after SHT DA. Significantly higher BP gain (mmHg/duration of apnea in s) was found in SHT DA vs. SA. Furthermore, DA attempts resulted in faster desaturation vs. SA. In conclusion, we have found moderate increases in BP during SA, DA, and SHT DA. These cardiovascular changes during immersed SA and DA are in agreement with those reported for dry SA and DA.     

A technique to measure the volume of diving birds during voluntary dives

Buoyancy has a substantial contribution to the total mechanical cost of diving in waterbirds. Most of the techniques currently employed to estimate buoyancy are based on measuring the volume of carcasses or forcibly submerged birds using the water displacement (Archimedes) principle. In such techniques, the voluntary control the bird might have over plumage and respiratory air volumes is neglected. Here, I propose an adjustment to the water displacement measurement that allows the measurement of buoyancy in real-time from unrestrained live birds diving voluntarily. The novelty and accuracy of the technique lie in using a pressure sensor to continuously measure the water level inside the dive tank while filtering out the interference from surface waves. The error of the volume measurement in the proposed technique was only ±2.4%. Feasibility of measurement is demonstrated on captive Great Cormorants (Phalacrocorax carbo sinensis). The measured volumes of Great Cormorants exceeded predictions made based on the volume of carcasses and on average resembled values measured from live restrained birds. However the technique highlighted the high variation in buoyancy of live birds (up to 30%) as a result of small changes in the air volumes taken with the bird underwater.     

Cardiovascular control during voluntary static exercise in humans with tetraplegia.

The purpose of the present study was 1) to investigate whether an increase in heart rate (HR) at the onset of voluntary static arm exercise in tetraplegic subjects was similar to that of normal subjects and 2) to identify how the cardiovascular adaptation during static exercise was disturbed by sympathetic decentralization. Mean arterial blood pressure (MAP) and HR were noninvasively recorded during static arm exercise at 35% of maximal voluntary contraction in six tetraplegic subjects who had complete cervical spinal cord injury (C(6)-C(7)). Stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were estimated by using a Modelflow method simulating aortic input impedance from arterial blood pressure waveform. In tetraplegic subjects, the increase in HR at the onset of static exercise was blunted compared with age-matched control subjects, whereas the peak increase in HR at the end of exercise was similar between the two groups. CO increased during exercise with no or slight decrease in SV. MAP increased approximately one-third above the control pressor response but TPR did not rise at all throughout static exercise, indicating that the slight pressor response is determined by the increase in CO. We conclude that the cardiovascular adaptation during voluntary static arm exercise in tetraplegic subjects is mainly accomplished by increasing cardiac pump output according to the tachycardia, which is controlled by cardiac vagal outflow, and that sympathetic decentralization causes both absent peripheral vasoconstriction and a decreased capacity to increase HR, especially at the onset of exercise.     

Cardiovascular dynamics during head-up tilt assessed via pulsatile and non-pulsatile models

Journal of Mathematical Biology - This study develops non-pulsatile and pulsatile models for the prediction of blood flow and pressure during head-up tilt. This test is used to diagnose potential...     

The influence of gas exchange on lung gas concentrations during air breathing

A model study is made of the contribution that continuing respiratory gas exchange makes to the alveolar plateau slope for O₂ during air breathing. Calculations in the model of the O₂ concentration appearing at the mouth during expiration, are performed for single breaths of air at constant flow rates 18 litres/min and 120 litres/min. At 18 litres/min the breathing period is 5 sec, the initial lung volume is 2300 ml, and the O₂ uptake rate is 300 ml STPD/min; whereas at 120 litres/min these parameters are 4 sec, 1200 ml, and 1800 ml STPD/min respectively. In each case the initial lung O₂ tension is taken to be 98 mm Hg. It is found that at 18 litres/min, the O₂ concentration difference on the alveolar plateau over the last second of expiration is 0.4 mm Hg when gas exchange is omitted and 1.2 mm Hg when gas exchange is included in the model. At 120 litres/min, this difference is zero and 5.0 mm Hg respectively. The gas exchange component predicted from a corresponding well-mixed compartment model is the same at 18 litres/min (0.8 mm Hg) but is 6.0 mm Hg at 120 litres/min.     

Microsphere studies of bullfrog central vascular shunts during diving and breathing in air.

Bidirectional central vascular shunts were measured during diving and breathing in air in unanesthetized bullfrogs by using pulmonary trapping of 38 mu mean diameter radionuclide-labelled microspheres. Six animals studied during diving exhibited a strong overall right-to-left shunting pattern comprised of both a predominant (68% mean) right-to-left shunt and a weak (23%) left-to-right countershunt. Five animals with access to air showed a variety of distribution patterns, including predominant shunts in the left-to-right (1 animal) and right-to-left (1 animal) directions, nearly complete mixing (2 animals) and separation of systemic and pulmonary venous returns (1 animal).     

Bacterial population dynamics in dairy waste during aerobic and anaerobic treatment and subsequent storage

The objective of this study was to model a typical dairy waste stream, monitor the chemical and bacterial population dynamics that occur during aerobic or anaerobic treatment and subsequent storage in a simulated lagoon, and compare them to those of waste held without treatment in a simulated lagoon. Both aerobic and anaerobic treatment methods followed by storage effectively reduced the levels of total solids (59 to 68%), biological oxygen demand (85 to 90%), and sulfate (56 to 65%), as well as aerobic (83 to 95%), anaerobic (80 to 90%), and coliform (>99%) bacteria. However, only aerobic treatment reduced the levels of ammonia, and anaerobic treatment was more effective at reducing total sulfur and sulfate. The bacterial population structure of waste before and after treatment was monitored using 16S rRNA gene sequence libraries. Both treatments had unique effects on the bacterial population structure of waste. Aerobic treatment resulted in the greatest change in the type of bacteria present, with the levels of eight out of nine phyla being significantly altered. The most notable differences were the >16-fold increase in the phylum Proteobacteria and the approximately 8-fold decrease in the phylum Firmicutes. Anaerobic treatment resulted in fewer alterations, but significant decreases in the phyla Actinobacteria and Bacteroidetes, and increases in the phyla Planctomycetes, Spirochetes, and TM7 were observed.     

Hydroxyl radicals detected via brain microdialysis in rats breathing air and during hyperbaric oxygen convulsions

Microdialysis was done on 300-400 g, awake, male rats with microdialysis probes inserted through guide cannulas into the striatum (Bregma co-ordinates A 0.5, L 2.9, D -4.0 for guide cannulas implanted 5 days previously). Rats were exposed to hyperbaric oxygen (HBO; 6 atm absolute, 5 atm gauge pressure of oxygen with carbon dioxide absorbed by soda lime). Artificial cerebrospinal fluid (CSF) containing 5 mM sodium salicylate was perfused at 1 microl/min and collected over sequential 10 min intervals with rats breathing air, then HBO, and after decompression. Times to convulsions and duration and severity of convulsions were observed and recorded. CSF samples were analyzed for 2,3- and 2,5-dihydroxybenzoic acid (DHBA), reaction products of hydroxyl radicals with salicylate, by HPLC and compared to authentic standards. Recovery of DHBAs was 48% from fluid surrounding microdialysis probes, based on in vitro tests. The average time to the first convulsion was 21 min and rats convulsed an average of 4 times during 40 min in HBO. There were no significant differences in hydroxyl radical production by this protocol during any of the 10 min collection periods in air or HBO (average in pmoles for 10 microl of all samples: 2,3-DHBA = 7.0 +/- 2.5 and 2,5-DHBA = 11.3 +/- 4.1). The failure to detect an increase in hydroxyl radicals in HBO prior to or during convulsions appears valid since each rat served as its own control.     

Adaptation and population dynamics of Azotobacter vinelandii during aerobic biological treatment of olive-mill wastewater

Olive-mill wastewater (OMW) has a high organic and polyphenol content and is resistant to biodegradation. Its disposal leads to a major environmental pollution problem in the Mediterranean basin. The detoxification of OMW following inoculation with Azotobacter vinelandii (strain A) was performed for two successive 5-day-period cycles in an aerobic, biowheel-type reactor, under non-sterile conditions. The phytotoxicity of the processed product was reduced by over 90% at the end of both cycles. To exclusively monitor the A. vinelandii population in the reactor a most probable number-PCR approach was employed and applied daily to serial dilutions of total DNA extracted from reactor samples. PCR sensitivity was independent of the presence of OMW or non-target DNA. The A. vinelandii population dynamics were successfully monitored, showing an initial adaptation period, followed by a sharp population maximum on the fourth day of both cycles (1.6x10(8) and 9.6x10(7) cells ml(-1) respectively), after a major phytotoxicity decline. N(2) fixation rates were estimated using the acetylene reduction assay and reached a peak during the first 1-2 days of each cycle (36 and 29 nmol C(2)H(2) ml(-1) h(-1) respectively). The data are consistent with an initial physiological adaptation phase, where the presence of phenolic compounds limits A. vinelandii growth but stimulates N(2) fixation, followed by a rapid growth phase as phytotoxicity declines.     

Hydroxyl radicals detected via brain microdialysis in rats breathing air and during hyperbaric oxygen convulsions

Abstract

Microdialysis was done on 300–400 g, awake, male rats with microdialysis probes inserted through guide cannulas into the striatum (Bregma co-ordinates A 0.5, L 2.9, D –4.0 for guide cannulas implanted 5 days previously). Rats were exposed to hyperbaric oxygen (HBO; 6 atm absolute, 5 atm gauge pressure of oxygen with carbon dioxide absorbed by soda lime). Artificial cerebrospinal fluid (CSF) containing 5 mM sodium salicylate was perfused at 1 µl/min and collected over sequential 10 min intervals with rats breathing air, then HBO, and after decompression. Times to convulsions and duration and severity of convulsions were observed and recorded. CSF samples were analyzed for 2,3- and 2,5-dihydroxybenzoic acid (DHBA), reaction products of hydroxyl radicals with salicylate, by HPLC and compared to authentic standards. Recovery of DHBAs was 48% from fluid surrounding microdialysis probes, based on in vitro tests. The average time to the first convulsion was 21 min and rats convulsed an average of 4 times during 40 min in HBO. There were no significant differences in hydroxyl radical production by this protocol during any of the 10 min collection periods in air or HBO (average in pmoles for 10 µl of all samples: 2,3-DHBA = 7.0 ± 2.5 and 2,5-DHBA = 11.3 ± 4.1). The failure to detect an increase in hydroxyl radicals in HBO prior to or during convulsions appears valid since each rat served as its own control.     

Working ability between air and trimix breathing gas under 8 ATA air condition

Pneumatic caisson work in Japan has come into operation since 1924. Afterward, this technique of compressed air work has been widely utilized in the construction of foundation basements, shafts of the bottom tunnel shields for subway and so forth. While using this technique of compressed air work means that workers have to be exposed to hyperbaric environment, this technique has risks of not only decompression sickness (DCS) but also toxicity of poisonous gas and/or oxygen deficiency. However, this technique is independent of city construction work and the operation of compressed air work higher than 5ATA (4.0 kg/cm2G) is actually been planning recently. Accordingly unmanned caisson work is considered as a better technique for such higher pressurized work, even though workers must enter into hyperbaric working fields for maintenance or repair of unmanned operated machinery and materials. This research is to establish the safe work under hyperbaric air environment at 8ATA.     

Beach-spawning fishes, terrestrial eggs, and air breathing

Many fishes have independently evolved beach spawning with oviposition at the water's edge. These include intertidal, subtidal, and estuarine, as well as a few freshwater, species. Their spectacular reproductive behavior at the boundary of water and land has focused attention on adults, but they emerge either briefly or not at all. The need for air breathing is more apparent in the eggs, and the reasons for emergence are more applicable to eggs than to the adults of most beach-spawning fishes. There is little evidence of air breathing in the adults, unless they are regularly emerged at other times as well. Conversely, eggs metabolize in air and show substantial emergence tolerance. We consider beach spawning a form of parental care in fishes. The adults place eggs so they will be emerged into air during part or all of incubation, providing increased temperatures, oxygen availability, and protection. Beach spawning provides habitat segregation at different points in the life history, with air emergence early in the life cycle and a return to water at hatching. The parents take great risks to spawn at the water's edge to give their offspring the most advantageous beginning in life.     

Temporal coordination of pharyngeal and laryngeal dynamics with breathing during swallowing: single liquid swallows.

The critical integration of timing and patterning between respiratory and swallowing events was studied with simultaneous videofluoroscopic and respiratory recording during single liquid swallows. Respiratory phase patterns and the onsets and durations of 12 predetermined swallowing events and associated respiratory activities were studied. Results showed four highly repeatable, temporally oriented sequences (clusters) of swallowing and related respiratory events. Two respiratory phase patterns were identified without statistically significant differences in frequency of occurrence between age, gender, or race. These findings will aid in the identification of normal and abnormal patterns of breathing and swallowing in patients with dysphagia.