Search PubMed⌕ Search

PubMed · 2799365

[Decompression problems in diving in mountain lakes].

Abstract

The relationship between tolerated high-pressure tissue nitrogen and ambient pressure is practically linear. The tolerated nitrogen high pressure decreases at altitude, as the ambient pressure is lower. Additionally, tissues with short nitrogen half-times have a higher tolerance than tissues which retain nitrogen for longer duration. For the purpose of determining safe decompression routines, the human body can be regarded as consisting of 16 compartments with half-times from 4 to 635 minutes for nitrogen. The coefficients for calculation of the tolerated nitrogen-high pressure in the tissues can be deduced directly from the half-times for nitrogen. We show as application the results of 573 simulated air dives in the pressure-chamber and 544 real dives in mountain lakes in Switzerland (1400-2600 m above sea level) and in Lake Titicaca (3800 m above sea level). They are in accordance with the computed limits of tolerance.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A A Bühlmann. 1989. [Decompression problems in diving in mountain lakes].. https://pubmed.ncbi.nlm.nih.gov/2799365/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Single ventricle palliation: greater risk of complications with the Fontan procedure than with the bidirectional Glenn procedure alone.

BACKGROUND: This study was performed to evaluate and compare the early, intermediate, and long-term outcomes of the bidirectional Glenn procedure and Fontan procedure in patients who live at moderately high altitude. METHODS: The outcome of each method of palliation for patients with a functionally single ventricle was retrospectively evaluated from a review of medical records. RESULTS: The bidirectional Glenn procedure was performed in 177 patients from October 1984 to June 2004. The Fontan procedure was performed in 149 patients from June 1978 to June 2004. Cardiovascular death or heart transplantation occurred in 8% of patients after the bidirectional Glenn procedure and 17% of patients after the Fontan procedure. Complications of systemic thromboembolic events, bleeding associated with anticoagulation therapy, protein losing enteropathy, and arrhythmias requiring implantation of a pacemaker, cardioversion, or radiofrequency ablation occurred in 7% of patients after the bidirectional Glenn procedure and 47% of patients after the Fontan procedure. Cardiovascular deaths and heart transplantation occurred less frequently when the Fontan procedure was performed in patients with a previous bidirectional Glenn procedure. However, the actuarial transplant-free survival and freedom from complications was not superior for a subgroup of patients who had a Fontan procedure after a bidirectional Glenn procedure in comparison to a subgroup of patients who had a bidirectional Glenn procedure alone. CONCLUSIONS: The bidirectional Glenn procedure can be used for long-term palliation of patients with a functionally single ventricle. Additional palliation with a Fontan procedure may increase the risk of stroke, protein losing enteropathy and arrhythmias without improving survival.

Altitude↗

Effect of the interaction between high altitude and socioeconomic factors on birth weight in a large sample from South America.

Several studies of South American populations showed that altitude is associated with low birth weight and intrauterine growth retardation. Although some of them analyzed the altitude-birth weight association, only a few assessed the effect of the interaction between altitude and socioeconomic factors on birth weight. The purpose of this research is to evaluate such effects on birth weight, after adjustment for confounding factors. This observational descriptive study includes a sample of 37,022 live-born infants without congenital anomalies, weighing >or=500 g, from 75 South American maternity hospitals, during 1982-1999. Of the total sample, 1,187 infants were born in two South American cities located at more than 2,000-m altitude: La Paz, Bolivia (N = 974 at 3,600 m) and Bogota, Colombia (N = 274 at 2,600 m). Among the seven risk factors analyzed, altitude was the main predictor of birth weight (except for gestational age). After adjustment for the other risk factors, birth weight at cities located above 2,000 m showed a decrease of approximately 200 g. When comparing highest and lowest socioeconomic levels, birth weight also showed differences for levels of altitude analyzed (lowland, <2,000 m; middle land, 2,600 m; and highland, 3,600 m). Interaction between both factors showed no effect. High altitude seems to act independent of socioeconomic status in explaining birth weight reduction.

Altitude↗

Montane speciation patterns in Ithomiola butterflies (Lepidoptera: Riodinidae): are they consistently moving up in the world?

Tropical lowland areas have often been seen as the centres of terrestrial species proliferation, but recent evidence suggests that young species may be more frequent in montane areas. Several montane speciation modes have been proposed, but their relative frequencies and predominant evolutionary sequence remain unclear because so few biogeographic and phylogenetic studies have tested such questions. I use morphological data to generate a phylogenetic hypothesis for all 11 species of the riodinid butterfly genus Ithomiola (Riodininae: Mesosemiini: Napaeina). These species are shown here to be all strictly geographically and elevationally allo- or parapatrically distributed with respect to their closest relatives in lowland and montane regions throughout the Neotropics. The overwhelming pattern in Ithomiola is of repeated upward parapatric speciation across an elevational gradient, and the genus appears to provide the clearest example to date of vertical montane speciation. All of the young derived species are montane and all of the old basal species are confined to the lowlands, supporting the hypothesis of montane regions largely as 'species pumps' and lowland regions as 'museums'. Possible reasons for the post-speciation maintenance of parapatric ranges in Ithomiola are discussed.

Altitude↗