Decompression: English tables

The formulation of decompression procedures has generally been based on the observation that divers can be decompressed without stoppages to surface, from steady-state exposures of about twice the atmospheric pressure. Because decompression sickness rarely develops from this "no-stop decompression", it has been assumed that no gas is liberated. It is therefore assumed, in the calculation of the majority of decompression tables, that using a 2:1 decompression ratio allows the additional gas load from the hyperbaric exposure to be transported to the lungs in solution. Ultrasonic scanning and Doppler techniques have shown that this is not the case. Decompression tables must therefore be formulated so as to take into account the presence of gas, the critical diameter of circulating bubbles and the inherent unsaturation introduced by oxygen.     

Computer generated track and field scoring tables: III. Model evaluation and analysis

An investigation is made into the subject of scoring tables for track and field with emphasis on the application of computers to calculate and output the tables. The resulting scoring tables represent an attempt to describe the effective quality of performance for track and field events. This paper is published in three parts. The first part reviewed the historical development of scoring tables. The second part presented a theoretical foundation and the development of a model which could be utilized for all scoring tables. In this final part, the model is evaluated and an analysis of the model validity is made. Sample computer generated scoring tables are included.     

k-Space partition diagrams: a graphical tool for analysis of MRI pulse sequences.

A new type of graphical tool for explaining and analyzing magnetic resonance imaging pulse sequences is developed and illustrated. This tool combines the partition diagram, which shows the evolution of multiple echoes with the application of multiple RF pulses, and k-space graphs, which show the evolution of the transverse magnetization as gradients are applied. The strength of the new tool lies in its ability to depict clearly the progression of complex imaging pulse sequences. Several complicated excitation sequences are used to illustrate this method.     

Comparative analysis of striatal FDOPA uptake in Parkinson's disease: ratio method versus graphical approach.

Striatal-to-occipital ratio (SOR) and influx constant K(i)(occ) are commonly used as analytic parameters in L-3,4-dihydroxy-6-(18)F-fluorophenylalanine (FDOPA) PET studies. Both have been shown to be useful in discriminating Parkinson's disease (PD) patients from healthy subjects. We evaluated the relative performance of SOR and influx constant (K(i)(occ)) in the clinical assessment of nigrostriatal dopaminergic function in PD. METHODS: Twenty-one parkinsonian patients (Hoehn and Yahr scale I-IV; mean age +/- SD, 56 +/- 9.2 y) and 11 healthy subjects (mean age, 60 +/- 16 y) underwent 3-dimensional dynamic FDOPA scanning from 0 to 100 min. After spatial realignment, PET images at each frame were integrated by summing 4 central striatal slices, and time-activity curves (TACs) were generated after placing a standard set of elliptic regions of interest over striatal and occipital structures. SOR and K(i)(occ) values for each subject were then computed from TACs at different times using an input function from the occipital cortex. RESULTS: Both SOR and K(i)(occ) showed significant bilateral decreases in striatal dopamine uptake in the PD group compared with the control group. SOR values estimated for 10-min frames between 65 and 95 min are statistically equivalent in group discrimination. In addition, SOR values in the caudate and putamen correlated strongly with K(i)(occ), especially toward the end of the scanning epoch. Both parameters correlated significantly and comparably with Unified Parkinson's Disease Rating Scale motor scores. CONCLUSION: These results suggest that SOR determined from a single 10-min scan at 95 min is as accurate as K(i)(occ) in separating PD patients from healthy subjects and in predicting clinical measures of disease severity.     

Decompression Sickness: An Update

In brief: Until 20 years ago, the physical phenomenon of bubbling was the primary consideration in decompression sickness (DCS). Now the physiological aspects of DCS and the physiochemical states that lead to bubbling are better understood. This paper discusses four important developments in the study of DCS: (1) the recognition of the importance of hydration states and flow in the microcirculation, (2) the documentation of intravascular bubble formation during asymptomatic decompressions, (3) the recognition of pharmacological substances that influence DCS, and (4) the development of an animal model to understand spinal cord bends. More attention will probably be given to the use of pharmacological agents in treating DCS in the future.     

太空减压病的发病率与预防

通过对太空减压病同高空减压病进行比较,阐明太空减压病应由高空减压病独立出来的必要性。太空减压病与高空减压病的病因学和发病机理相同,但引起发病率有不同的规律（包括影响因素等）和各自独特的特征。为了得对太空减压病有一个系统明确的认识,利于更有效地制定预防方案和建立学科,太空减压病应成为独立的专业术语。     

Decompression sickness: USN operational experience 1969-1989.

This report presents data on the U.S. Navy's experience in decompression sickness occurring in operational flight from 1 January 1969 to 30 December 1989. During these 21 years, decompression sickness was reported in 12 USN aircraft and involved 15 aircrew. The primary cause of decompression, as might be expected, was a loss of cabin or cockpit pressurization. The most common manifestation of decompression sickness was limb or joint pain although some crewmembers experienced various manifestations of neurological dysfunction. One crewmember experienced chokes. Of the 15 afflicted aircrew, 13 (87%) had complete remission of symptoms by the time they landed. Two crewmembers required compression therapy for resolution of symptoms. None of the reported symptoms were incapacitating and none of the aircraft involved crashed or received even minor damage.     

Generation of dose calculation data tables using cubic spline interpolation

In order to calculate treatment machine settings for a teletherapy machine (e.g., time or monitor units), tables are usually used for variables such as output factor, TMR, percent depth dose. The tables are often generated from data collected at a few points. A linear interpolation is usually used to generate values between the measured points. This can introduce errors as great as 2% between the calculated and actual data points. Using a mathematical software package a computer can generate smooth, accurate curves that agree with measured values to within a few tenths of a percent. This method is not an averaging type of procedure by which a certain function is chosen and parameters are adjusted to force the function to fit the data as closely as possible, but rather is a procedure that fits curves exactly through the measured data points.     

Decompression sickness during simulated extravehicular activity: ambulation vs. non-ambulation

BACKGROUND: Extravehicular activity (EVA) is required from the International Space Station on a regular basis. Because of the weightless environment during EVA, physical activity is performed using mostly upper-body movements since the lower body is anchored for stability. The adynamic model (restricted lower-body activity; non-ambulation) was designed to simulate this environment during earthbound studies of decompression sickness (DCS) risk. DCS symptoms during ambulatory (walking) and non-ambulatory high altitude exposure activity were compared. The objective was to determine if symptom incidences during ambulatory and non-ambulatory exposures are comparable and provide analogous estimates of risk under otherwise identical conditions. METHODS: A retrospective analysis was accomplished on DCS symptoms from 2010 ambulatory and 330 non-ambulatory exposures. RESULTS: There was no significant difference between the overall incidence of DCS or joint-pain DCS in the ambulatory (49% and 40%) vs. the non-ambulatory exposures (53% and 36%; p > 0.1). DCS involving joint pain only in the lower body was higher during ambulatory exposures (28%) than non-ambulatory exposures (18%; p < 0.01). Non-ambulatory exposures terminated more frequently with non-joint-pain DCS (17%) or upper-body-only joint pain (18%) as compared with ambulatory exposures, 9% and 11% (p < 0.01), respectively. DISCUSSION: These findings show that lower-body, weight-bearing activity shifts the incidence of joint-pain DCS from the upper body to the lower body without altering the total incidence of DCS or joint-pain DCS. CONCLUSIONS: Use of data from previous and future subject exposures involving ambulatory activity while decompressed appears to be a valid analogue of non-ambulatory activity in determining DCS risk during simulated EVA studies.     

Decompression illness presenting as breast pain.

We present two cases of decompression illness in women in whom the initial symptom causing distress after completion of the dives was breast pain. Both women were also subsequently found to have a patent foramen ovale. We postulate that breast pain may be an unusual under-recognized manifestation of decompression illness.     

Viewpoint: the type A- and the type B-variants of Decompression Sickness.

BACKGROUND: Symptoms of neurological decompression incidents (DCS/AGE) can be severe or mild. It is unknown if these differences of symptom presentation represent different clinical entities or if they represent just the spectrum of DCS/AGE. METHODS: 267 cases with DCS/AGE were compared retrospectively and classified into two subgroups, the Type A-DCS/AGE for cases with a severe and often stroke-like symptomatology and the Type B-DCS/AGE for those with milder and sometimes even doubtful neurological symptoms. The main outcome measures were the number of hyperbaric treatments (HTs) needed and the clinical outcome. RESULTS: 42 patients with DCS/AGE were classified as Type A- and 225 patients met the criteria for a Type B-DCS/AGE. Patients with Type A-lesions were more severely affected, needed more hyperbaric treatments and had a less favorable outcome than patients with the Type B-variant. CONCLUSIONS: The Type A- and the Type B-DCS/AGE are likely to be different entities with better clinical outcome in the Type B-variant and possibly significant differences in the underlying pathophysiologies of both variants. Future studies with a particular focus on the up to now inadequately investigated Type B-DCS/AGE are necessary to elucidate such differences in the pathophysiology.     

Decompression sickness: an increasing risk for the private pilot.

Decompression sickness is not an appreciated hazard among the private pilot community. This is of growing concern with the increasing number of nonpressurized aircraft capable of flying to altitudes in excess of 5,468 m (18,000 ft). A case report is presented of a 42-year-old pilot who apparently experienced decompression sickness at flight level 250 which went unrecognized until several months after the incident.