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PubMedDate not supplied

Pneumomediastinum after lung packing.

Lung packing (glossopharyngeal insufflation) consists of forcing air into the lungs, using glossopharyngeal muscle contractions similar to swallowing. Breath-hold divers perform this technique after a maximal inhalation prior to diving, thus increasing initial lung volume. However, as suggested by previous authors, this breathing maneuver could theoretically lead to lung rupture. Here we report a pneumomediastinum found on chest CT scan in a diver during a physiological study, when glossopharyngeal insufflation increased the volume of gas in the lungs by 1,040 ml (over his total lung capacity); at the same time, his transpulmonary pressures increased up to 4.1 kPa. We discuss the possibility that the very high transpulmonary pressures during lung packing caused this pneumomediastinum.

Adult↗
PubMed1980

Skin circulation of the frog, Rana catesbeiana: distribution and dynamics.

The volume and distribution of blood flow to the skin of the bullfrog, Rana catesbeiana, from both the pulmocutaneous and systemic arterial sources were measured. Radioactively labelled microspheres (35 +/- 5 micron) were used to map the regional distribution of each of these sources and to measure the systemic blood flow to the skin during air breathing and diving. Cutaneous artery blood flow was measured with an ultrasonic (Doppler) flowmeter. The systemic supply to the skin perfuses predominantly the limbs, while the largest cutaneous artery supply is to the back and flanks of the animal. All regions received blood from both sources. The cutaneous artery blood flow decreased during diving to approximately one-third of the pre-dive level. This decrease, however, was offset by an approximately equivalent increase in systemic blood flow to the skin during diving. These data should reconcile the decrease in pulmocutaneous blood flow and the important function of the skin as a gas exchanger during diving.

Animals↗
PubMedDate not supplied

Continuous core temperature monitoring of search and rescue divers during extreme conditions.

OBJECTIVES: To study the feasibility of continuously monitoring core temperatures of search and rescue divers, to compare core temperature gradients occurring during warm and cold diving events, and to identify conditions under which divers are subjected to extreme temperatures. METHODS: Between June 1994 and March 1995, emergency medical technicians (EMTs) from two midwestern dive teams volunteered to ingest an encapsulated temperature sensor developed for the National Aeronautics and Space Administration. The capsule monitored continuous core temperatures and transmitted the data to a recorder worn under the divers' dry suits. RESULTS: Twenty male EMTs, mean age 34 years and mean body weight 184 pounds, were monitored during training. Nine dives were ice dives, with ice thickness averaging 9 inches, and mean ambient temperatures of 33 degrees F. Eleven dives were warm-water dives; average water temperature was 70 degrees F and mean ambient temperature was 74 degrees F. The average time spent in the dry suit was 95 minutes, and the mean total bottom time was 15 minutes. The ice divers showed a mean increase in core temperature of 1.0 degrees C, while the warm-water divers showed a mean increase of 1.2 degrees C. Divers experiencing the most extreme fluctuations were those in the role of safety diver, regardless of the season. Divers reported more subjective discomfort during ice dives than during warm-water dives. CONCLUSIONS: Continuous monitoring of body temperature during the duration of dive operations is possible, but labor-intensive. Safety measures to protect divers from extreme core temperature fluctuations should focus on the safety diver as well as the active diver.

Adult↗
PubMed1990

Microanatomy of retia mirabilia of bowhead whale foramen magnum and mandibular foramen.

The morphology of vessels of the cervical rete mirabile near the region of the foramen magnum of the bowhead whale, Balaena mysticetus, as well as of retial vessels of the mandibular foramen was studied by light and transmission electron microscopy. A comparison of arterial and venous components of the mandibular rete revealed considerable arterial branching and arteriovenous anastomoses. Although the small arteries of bowhead retia contained the same layers found in nonretial arteries, several distinctive morphologic features were evident. These included wide separation by collagenous connective tissue and small size of individual smooth muscle cells of the tunica media. These myocytes also contained considerable perinuclear glycogen and communicated minimally with adjacent myocytes by small foot-like cytoplasmic appendages as well as branching of basement membranes. Ganglia-like neural plexuses were observed within the tunica media of arterial retia. Endothelial cells lining the intima demonstrated loose peripheral edges which frequently projected into the vessel lumen, and these cells rested upon a subjacent layer of reticular fibers. It is known for some species that the retial supply to the brain in whales largely supplants an internal carotid arterial supply and that the spinal cord is supplied by retia. The physiologic role of the bowhead mandibular retia remains unknown. The retia mirabilia of cetaceans are considered as one of the morphologic adaptations which modulate hemodynamics during diving and resurfacing. The morphologic features of these vessels in the bowhead whale, as revealed by electron microscopy, appear to reflect the capability to respond in a slow but sustained manner to diving, and the large glycogen deposits may help sustain vascular myocyte metabolism during prolonged submersion.

Animals↗
PubMed2001

Headache in divers.

The increasing popularity of scuba diving has added a new category to the differential diagnosis of headache. Headache in divers, while uncommon and generally benign, can occasionally signify serious consequences of hyperbaric exposure such as arterial gas embolism, decompression sickness, and otic or paranasal sinus barotrauma. Inadequate ventilation of compressed gases can lead to carbon dioxide accumulation, cerebral vasodilatation, and headache. Other types of headache encountered in divers include exertional headache, cold stimulus headache, migraine, tension-type headache, acute traumatic headache, cervicogenic headache, carbon monoxide poisoning headache, and headache associated with envenomation. Correct diagnosis and appropriate treatment require a careful history and neurologic examination as well as an understanding of the unique physiologic stresses of the subaquatic environment.

Animals↗
PubMed2002

Sleep patterns during 30-m nitrox saturation dives and in a confined atmospheric environment.

Sleep patterns during saturation dives equivalent to a 30-m depth (pressurized condition) and habitation in a confined environment at 1 atm absolute pressure (non-pressurized condition) were studied to determine the effects of environmental pressure. Eight inexperienced divers experienced the pressurized condition of the saturation dives, and nine healthy subjects experienced the non-pressurized condition. Standard polysomnographs were recorded for 262 nights. For both conditions, reductions in total sleep time accompanied by lengthening in sleep latency and reduction in sleep efficiency were observed from the latter part of the experiments through to the recovery periods. These findings suggest that changes were related to psychological and physiological stresses caused by long stays in a confined environment and not by the environmental pressure.

Adult↗
PubMed1987

[Evaluation of diving stress implication of analysis of work loads].

An investigation was conducted on the actual diving conditions of 2,996 divers in Japan except those engaged in fishery. Results of analysis made on the diving profiles and actual working conditions showed that some of their jobs required heavy load and that the burden was excessively large. Little study has been made for the proper evaluation of diving stress or work loads, but it has been assumed from these limited studies that the load is not so heavy. The load has been generally estimated to be about 1.8l/min STPD of oxygen consumption (VO2) during 40 l/min STPD of expiratory gas volume/min (VE). In our examination of their actual diving work, their work load was far greater than our expectation. It was in practice not only difficult to obtain the actual VO2 but also very difficult to determine their actual fatigue. Instead of these, it is necessary to establish an adequate index for evaluating diving work load. Studies have been made in our laboratory since 1981 and regression equations have been finally obtained, by which load during diving work can be determined using heart rate as index. Seven healthy males were chosen as subjects of the present study having a mean age of 34.4 yr and a mean diving history of 7.3 yr. First, performance time was acquired in each subject by bicycle ergometer exercise and the maximalen oxygen consumption (VO2-max) was obtained. In the second step, VO2-max was obtained by using the regulator apparatus for breathing during SCUBA diving. This value was 86.1% of the first step. The third step was made in a swimming pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1970

[The dolphin].

Explore the source record for details and available documents.

Adaptation, Physiological↗
PubMed2000

Functional conservation of the active sites of human and Drosophila angiotensin I-converting enzyme.

Human somatic angiotensin I-converting enzyme (sACE) has two active sites present in two homologous protein domains, resulting from a tandem gene duplication. It has been proposed that the N- and C-terminal active sites can have specific in vivo roles. In Drosophila melanogaster, Ance and Acercode for two ACE-like single-domain proteins, also predicted to have distinct physiological roles. We have investigated the relationship of Ance and Acer to the N- and C-domains of human sACE by genomic sequence analysis and by using domain-selective inhibitors, including RXP 407, a selective inhibitor of the human N-domain. These phosphinic peptides were potent inhibitors of Acer, but not of Ance. We conclude that the active sites of the N-domain and of Acer share structural features that permit the binding of the unusual RXP407 inhibitor and the hydrolysis of a broader range of peptide structures. In comparison, Ance, like the human C-domain of ACE, displays greater inhibitor selectivity. From the analysis of the published sequence of the Adh region of Drosophila chromosome 2, which carries Ance, Acer, and four additional ACE-like genes, we also suggest that this functional conservation is reflected in an ancestral gene structure identifiable in both protostome and deuterostome lineages and that the duplication seen in vertebrate genomes predates the divergence of these lineages. The conservation of ACE enzymes with distinct active sites in the evolution of both vertebrate and invertebrate species provides further evidence that these two kinds of active sites have different physiological functions.

Acetylation↗
PubMed1987

Lipoid pneumonitis in a commercial abalone diver.

This report describes the clinical and pulmonary function manifestations found in a 37-yr-old commercial abalone diver who developed diffuse lipoid pneumonitis due to inhalation of aerosolized mineral oil contained in the unfiltered air generated from his surface air compressor. Four years later, the patient continued to be symptomatic with shortness of breath and dyspnea during exertion, and repeat physiologic evaluation continued to demonstrate findings of a restrictive ventilatory defect.

Adult↗
PubMed1981

Chokes--favorable response to delayed recompression therapy: a case report.

The pulmonary manifestations of decompression sickness have been attributed to various mechanisms, all of which invoke bubble formation and presence in the lung as the cause of symptoms. A case of persistent "chokes" syndrome, which responded to recompression of 72 h after presentation, is described. The possible physiological mechanisms and the late response to therapy is discussed.

Adult↗
PubMed1978

Chamber-based system for physiological monitoring of submerged exercising subjects.

A system has been designed which allows for measurement of cardiorespiratory parameters in the fully submerged subject performing graded exercise. It consists of a horizontal wet chamber; a waterproofed, electrically braked bicycle ergometer; and a low-resistance "bag-in-a-box" breathing apparatus. Chamber and breathing apparatus design allow for a great deal of flexibility in both positioning of the subject and instrumentation. The 200-liter "bag-in-a-box" configuration provides the subject with humidified gas through 2.5 in. i.d. tubing. A rolling seal spirometer provides the lung counter volume. Provision is made for breath-by-breath gas analysis with a mass spectrometer. Hydrostatic pressure on the diver's thorax relative to chamber pressure can be easily and reproducibly varied over a wide range of positive and negative static lung loads. This system has been used on over 100 man-dives to depths equivalent to 6.5 ATA with oxygen consumptions up to 4.0 liters/min.

Humans↗