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PubMed1991

Decompression comparison of N2 and O2 in rats.

We have previously reported that O2 in the breathing gas mixture contributed significantly to the risk of decompression sickness (DCS) in rats after rapid (less than 10 s) decompression to the surface from depth. The rate of O2 uptake was extremely fast (less than 1 min estimated for equilibrium after a pressure change) compared to much slower rates for He and N2. To further define the role that O2 plays in diving, the present investigation examined decompression outcome in unanesthetized male albino rats after 60-min N2-O2 dives (1-3 atm abs O2, depth 6.26 or 7.26 atm abs). Slower decompression profiles were used to determine the elimination rates of N2 and O2 as pressure was reduced and included "stops" of up to 20 min. The probability of DCS was modeled using the maximum likelihood technique. O2 again contributed significantly to the risk of DCS, although O2 was eliminated very rapidly during decompression; the washout of N2 was considerably longer. These findings support the view that O2 can add significantly to decompression risk. However, this phenomenon may not normally be encountered during human diving operations where relatively slower decompression and lower PO2's are used.

Animals↗
PubMed1979

Evaluation of standard decompression schedule by agarose gel method.

The Standard Decompression Schedule was evaluated by the method of bubble formation in agarose gel, the result of which can be summarized as follows: 1) The number of bubbles formed in agarose gel corresponded well with the exposed pressure. 2) The technique of this method was simple and the number of bubbles was accurately counted. 3) Eventually, this method was useful for examining the decompression schedules. 4) It is not always safe to follow the Standard Decompression Schedule in some pressure conditions. 5) As to the period of time that a person is able to tolerate a high pressure condition, the prescription of the Standard Decompression Schedule is not necessarily correct. 6) The number of bubbles was small by the proper decompression schedule, for example, in the cases of exposure above the 60-meter depth of water. 7) This method can be applied for the prevention of decompression sickness when the agarose gel samples are attached to the workers during the compressed air work. 8) The number of bubbles was inconsistent with the coefficient of body pressure (1. N2 in the body), therefore it is not necessarily safe to rely only on the coefficient of body pressure. 9) To prevent osteonecrosis, the Standard Decompression Schedule is not proper, a deeper first stop and slower ascent being recommended.

Decompression↗
PubMed1985

Air and nitrox saturation decompression: a report of 4 schedules and 77 subjects.

Seventy-seven subjects were decompressed from air or nitrogen-oxygen (nitrox) saturation exposures at 18.3 to 40.2 meters sea water (msw) [60 to 132 feet sea water (fsw)] using four different decompression schedules. A h schedule for decompression from an air saturation-excursion profile at 18.3 msw (60 fsw) resulted in pain-only decompression sickness (DCS) symptoms in 2 of 23 subjects. A 32 and 35 h schedule from a different air saturation profile at 19.8 and 22.9 msw (65 and 75 fsw), respectively, resulted in DCS symptoms in 1 of 24 subjects. A third and fourth schedule for air or nitrox saturation at 40.2 msw (132 fsw) resulted in DCS symptoms in 3 of 12 and 1 of 18, respectively. No serious (type II) symptoms were observed as a result of any of the decompressions. All DCS cases consisted of knee pain occurring either in the last 3 msw of the decompression or shortly after surfacing. Doppler ultrasound monitoring revealed venous gas emboli (VGE) in several subjects, but generally only shallow to 6.1 msw (20 fsw). Results demonstrate an overall DCS incidence of 9%, and all cases were pain-only and localized to the knee. The third schedule (U.S. Navy heliox saturation decompression schedule) seems to produce a higher incidence of DCS than the other schedules when used in air or nitrox exposures. Differentiation between the schedules designed for nitrox was impossible due to the limited number of subjects in each and the variable nature of the exposures.

Adult↗
PubMed1996

[A method for evaluating the safety of decompression regimens for divers].

The authors offer a way of estimation of safety modes of decompression, based on definition of intensity of venous gas embolism (VGE) at each decompression and account of probability of illness of divers in series of tests. Intensity of VGE was determined with the help of ultrasonic gas bubbles Doppler radar. Comparative safety of standard modes of decompression of divers of the Navy was estimated, and also the modes, designed in accordance with mathematical model of decompression, offered by I. A. Voĭtsekhovich (1990), were done. The results testify, that use of ultrasonic radar for estimation of intensity of VGE at decompression and account of average and maximum probability of decompression illness in series of tests of modes permit to receive the comparative characteristic of safety of modes at small number of decompressions.

Adult↗
PubMed1997

Compressed air tunneling and caisson work decompression procedures: development, problems, and solutions.

Multinational experience over many years indicates that all current air decompression schedules for caisson and compressed air tunnel workers are inadequate. All of them, including the Occupational Safety and Health Administration tables, produce dysbaric osteonecrosis. The problem is compounded because decompression sickness (DCS) tends to be underreported. Permanent damage in the form of central nervous system or brain damage may occur in compressed air tunnel workers, as seen on magnetic resonance imaging, in addition to dysbaric osteonecrosis. Oxygen decompression seems to be the only viable method for safely decompressing tunnel workers. Oxygen decompression of tunnel workers has been successfully used in Germany, France, and Brazil. In Germany, only oxygen decompression of compressed air workers is permitted. In our experience, U.S. Navy tables 5 and 6 usually prove adequate to treat DCS in caisson workers despite extremely long exposure times, allowing patients to return to work following treatment for DCS. Tables based on empirical data and not on mathematical formulas seem to be reasonably safe. U.S. Navy Exceptional Exposure Air Decompression tables are compared with caisson tables from the United States and Great Britain.

Decompression↗
PubMed1994

Comparison of haemodynamic effects during venous air infusion and after decompression in pigs.

We have compared haemodynamic effects of venous gas emboli during continuous air infusion into the right atrium and after rapid decompression in pigs. Eight anaesthetized and spontaneously breathing pigs received continuous air infusion at a rate of either 0.05 ml.kg-1.min-1 (six pigs, air infusion group) or 0.10 ml.kg-1.min-1 (two pigs). Another eight pigs (decompression group) underwent a 30-min compression to 5 bar (500 kPa, absolute pressure), followed by a rapid decompression (2 bar.min-1). Haemodynamic variables were measured or calculated, and bubbles in the pulmonary artery were monitored using transoesophageal echocardiography. The results showed less variation in the maximal increase in mean pulmonary arterial pressure (BPa,pulm) during air infusion (0.05 ml.kg-1.min-1) than after decompression, although the mean maximal increase did not differ between the two groups [28.0 mmHg (3.73 kPa), 95% confidence interval (CI) 23.5-32.5, vs 32.0 mmHg (4.27 kPa), 95% CI 25.3-38.7, P = 0.3]. The BPa,pulm stabilized or decreased very slowly after peak values were reached in the air infusion group, whereas the BPa,pulm decreased rapidly during the same period in the decompression group. No significant changes in mean arterial pressure were observed during air infusion (0.05 ml.kg-1.min-1), in contrast to the rapid increase and the subsequent decrease, that appeared after decompression. Finally, the maximal bubble count was much lower in the air infusion group than in most of the pigs in the decompression group. The two pigs that received 0.10 ml.kg-1.min-1 stopped breathing after 5-min infusion, developed arterial hypotension and died.

Animals↗
PubMed2000

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

Acute Disease↗
PubMed2001

A randomized trial of very early decompressive craniectomy in children with traumatic brain injury and sustained intracranial hypertension.

OBJECT: The object of our study was to determine, in children with traumatic brain injury and sustained intracranial hypertension, whether very early decompressive craniectomy improves control of intracranial hypertension and longterm function and quality of life. METHODS: All children were managed from admission onward according to a standardized protocol for head injury management. Children with raised intracranial pressure (ICP) were randomized to standardized management alone or standardized management plus cerebral decompression. A decompressive bitemporal craniectomy was performed at a median of 19.2 h (range 7.3-29.3 h) from the time of injury. ICP was recorded hourly via an intraventricular catheter. Compared with the ICP before randomization, the mean ICP was 3.69 mmHg lower in the 48 h after randomization in the control group, and 8.98 mmHg lower in the 48 hours after craniectomy in the decompression group (P=0.057). Outcome was assessed 6 months after injury using a modification of the Glasgow Outcome Score (GOS) and the Health State Utility Index (Mark 1). Two (14%) of the 14 children in the control group were normal or had a mild disability after 6 months, compared with 7 (54%) of the 13 children in the decompression group. Our conclusion was that when children with traumatic brain injury and sustained intracranial hypertension are treated with a combination of very early decompressive craniectomy and conventional medical management, it is more likely that ICP will be reduced, fewer episodes of intracranial hypertension will occur, and functional outcome and quality of life may be better than in children treated with medical management alone (P=0.046; owing to multiple significance testing P <0.0221 is required for statistical significance). This pilot study suggests that very early decompressive craniectomy may be indicated in the treatment of traumatic brain injury.

Brain Injuries↗
PubMed2001

Comparison of results of core decompression and intertrochanteric osteotomy for nontraumatic osteonecrosis of the femoral head using Cox regression and survivorship analysis.

Different surgical procedures have been recommended for osteonecrosis of the femoral head to prevent or delay the need for arthroplasty. Core decompression is a commonly used treatment in the early stages of the disease, but the published efficacy has varied markedly. Only a few comparisons of different techniques have been reported. The aim of this study was to evaluate and compare the results of 2 commonly used procedures, core decompression and intertrochanteric osteotomy, using Cox regression and survivorship analysis. A total of 177 cases with a mean age of 41 years at surgery were treated for osteonecrosis (94 core decompressions, 83 osteotomies). Any further surgery was defined as failure and endpoint. Significant risk factors for treatment failure were age > 40 years at surgery (P = .022), corticosteroid intake (P < .001), advanced stage of necrosis (Steinberg stage > or =III, P=.04), and core decompression (P = .084). To analyze the influence of the surgical procedure, patients with corticosteroid treatment were excluded, and survival analysis was performed. This analysis revealed survival rates of 74% after osteotomy and 78% after core decompression 6 years postoperatively in early, precollapse stages (P = .819). In advanced stages, the rate of survival for hips after core decompression was lower (56%) than in hips after osteotomy (76%) (P = .056). Our results indicate that core decompression may be as effective as intertrochanteric osteotomy in precollapse stages but is less traumatizing and is cost-effective. For postcollapse hips, intertrochanteric osteotomy should be considered.

Adolescent↗
PubMed1999

The degree of decompressive relief and its relation to clinical outcome in patients undergoing surgery for lumbar spinal stenosis.

STUDY DESIGN: A cross-sectional, clinical study to evaluate surgical decompression of the stenotic area monitored by computed tomographic scan and its relation to clinical variables in patients operated on for lumbar spinal stenosis. OBJECTIVE: To study in patients with lumbar spinal stenosis the influence of the degree of compressive relief on the patients' clinical outcome. SUMMARY OF BACKGROUND DATA: The goal of surgical treatment in lumbar spinal stenosis is to decompress the stenotic area. Although the decompression should be adequate, there are no clear guidelines to determine the extent of necessary decompression. In fact, there is clinical evidence that there is a discrepancy between the surgical outcome in the patient with lumbar spinal stenosis and postoperative radiologic findings. METHODS: In 92 patients with lumbar spinal stenosis who had had no prior back surgery, preoperative and postoperative computed tomographic scans were obtained to determine the degree of decompression. The postoperative scan findings were classified according to the degree of decompression into a no-stenosis group (n = 35), an adjacent-stenosis group (n = 27), and a residual-stenosis group (n = 30). The postoperative instability of the lumbar spine was investigated by functional radiography. The subjective disability of the patients was assessed using the Oswestry score and the severity of pain using the visual analog scale. Walking capacity was evaluated by a treadmill test. The patients' estimations of the results of surgery were classified into groups of satisfied patients and dissatisfied patients. RESULTS: The mean Oswestry score in all 92 patients was 27.1, and mean walking capacity was 630 m. In the satisfied patients, the Oswestry score was 18.8 and in the dissatisfied patients, 34.9 (P < 0.0000). Walking capacity was 690 m and 594 m, respectively. There were 30 patients with postoperative spinal instability, but it had no influence on surgical outcome. There were no differences in the Oswestry score, walking capacity, and patients' satisfaction among the postoperative CT groups. In the linear regression analysis, the satisfied patient corresponded significantly with the Oswestry score. CONCLUSIONS: The satisfaction of the patients with the results of surgery was more important in surgical outcome than the degree of decompression detected on computed tomographic scan.

Cross-Sectional Studies↗
PubMed1999

Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord.

STUDY DESIGN: A study to measure the shifts of the spinal cords and the effects of decompression laminoplasty in 65 patients with cervical lesions who underwent computed tomographic myelography before and after laminoplasty. OBJECTIVES: To investigate limitations of the spinal cord posterior shift after laminoplasty and to clarify the optimal decompression areas to obtain effective posterior shifting. SUMMARY OF BACKGROUND: Although several types of laminoplasty have been performed, all procedures share the common purpose of posterior decompression. No previous studies have examined the limitations of posterior decompression or the optimal decompression range. METHODS: The distance from the posterior edge of each vertebral body or disc level to the posterior edge of the spinal cord was measured by computed tomographic myelography. After the posterior shift was determined by calculating the difference between pre- and postsurgical distances, the relations between posterior shift and neck alignment, clinical results, and the areas of decompression were analyzed. RESULTS: The spinal cord shift ranged from a maximum of 6.6 mm to a minimum of 0 mm. Clinically, spinal cord shifts greater than 3 mm were associated with good clinical outcomes. Upward or downward advanced laminoplasty was related to larger spinal cord shifts at the upper or lower cervical spine. CONCLUSIONS: A mean spinal cord shift of > 3 mm was associated with good clinical outcomes after laminoplasty. In cases with compressive lesions at the upper or lower cervical spine, extension of decompression one level above or one level below likely results in a greater posterior spinal cord shift at these lesions.

Cervical Vertebrae↗
PubMed1997

Decompression comparison of helium and hydrogen in rats.

The hypothesis that there are differences in decompression risk between He and H2 was examined in 1,607 unanesthetized male albino rats subjected to dives on 2% O2-balance He or 2% O2-balance H2 (depths < or = 50 ATA, bottom times < or = 60 min). The animals were decompressed to 10.8 ATA with profiles varying from rapid to slow, with up to four decompression stops of up to 60 min each. Maximum likelihood analysis was used to estimate the relative decompression risk on a per unit pressure basis (termed "potency") and the rate of gas uptake and elimination, both factors affecting the decompression sickness risk, from a specific dive profile. H2 potency for causing decompression sickness was found to be up to 35% greater than that for He. Uptake rates were unresolvable between the two gases with the time constant (TC) estimated at approximately 2-3 min, leading to saturation in both cases in < 15 min. Washout of both gases was significantly slower than uptake, with He washout (TC approximately 1.5-3 h) substantially slower than H2 washout (TC approximately 0.5 h). It is unknown whether the decompression advantage of the faster washout of H2 or the disadvantage of its increased potency, observed in the rat, would be important for human diving.

Animals↗
PubMed2001

Effects of intraluminal distention and decompression on microvascular permeability and hemodynamics of the equine jejunum.

OBJECTIVE: To determine whether intraluminal distention and subsequent decompression of the equine jejunum affects intestinal blood flow, hemodynamics, and microvascular permeability. ANIMALS: 5 healthy adu t horses. PROCEDURES: Horses were anesthestized and underwent exploratory laparotomy. Two jejunal segments were identified as sham-operated or instrumented segments. After baseline values were obtained, intraluminal distention was created in the experimental segment to induce an ntraluminal pressure of 18 cm H2O. After 120 minutes of distention, the intestine was decompressed for 120 minutes. Mesenteric blood flow, oxygen delivery, oxygen consumption, microvascular permeability, wet weight-to-dry weight ratio, neutrophil infiltration, and vascular resistance were determined and comparisons made among control, sham-operated, and experimental segments. RESULTS: Mean jejunal blood flow was 21.4 ml/min per kg. There was a significant decrease in mesenteric bood flow to the distended intestine (13.4 ml/min per kg). Blood flow increased significantly during the decompression period (340% of baseline blood flow). Intraluminal distention and subsequent decompression resulted in a significant increase in microvascular permeability, as determined by the osmotic reflection coefficient. Oxygen delivery and oxygen content decreased significantly during the distention period and increased during decompression. Morphologic evaluation revealed a significant increase in edema and neutrophil infiltration after distention and decompression, compared with results for the sham-operated or control segments. CONCLUSIONS AND CLINICAL RELEVANCE: Intraluminal distention and decompression of the equine jejunum results in low-flow ischemia and edema, which may contribute to adhesions and ileus in the postoperative period after surgery for obstructions of the small intestines.

Animals↗
PubMed1999

Ventricular pressure monitoring during bilateral decompression with dural expansion.

OBJECT: The management of massive brain swelling remains an unsolved problem in neurosurgery. Despite newly developed medical and pharmacological therapy, the rates of mortality and morbidity caused by massive brain swelling remain high. According to many recent reports, surgical decompression with dural expansion is superior to medical management in patients with massive brain swelling. To show the quantitative effect of decompressive surgery on intracranial pressure (ICP), the authors performed a ventricular puncture and measured the ventricular ICP continuously during decompressive surgery and the postoperative period. METHODS: Twenty patients with massive brain swelling who underwent bilateral decompressive craniectomy with dural expansion were included in this study. In all patients, ventricular puncture was performed at Kocher's point on the side opposite the massive brain swelling. The ventricular puncture tube was connected to the continuous monitor via a transducer device. The ventricular pressure was monitored continuously, during the bilateral decompressive procedures and postoperative period. The initial ventricular ICP was variable, ranging from 16 to 65.8 mm Hg. Immediately after the bilateral craniectomy, the mean ventricular ICP decreased to 50.2+/-16.6% of the initial ICP (range 5-51.5 mm Hg). Additional opening of the dura decreased the mean ICP by an additional 34.5% and reduced the ventricular pressure to 15.7+/-10.7% of the initial pressure (range 0-15 mm Hg). Ventricular pressure measured postoperatively in the neurosurgical intensive care unit was lowered to 15.1+/-16.5% of the initial ICP. The ventricular ICP trend in the first 24 hours after decompressive surgery was an important prognostic factor; if it was greater than 35 mm Hg, the mortality rate was 100%. CONCLUSIONS: Bilateral decompression with dural expansion is an effective therapeutic modality in the control of ICP. To obtain favorable clinical outcomes in patients with massive brain swelling, early decision making and proper patient selection are very important.

Adolescent↗
PubMedDate not supplied

Study of long intestinal tube for decompression of obstructive left colon cancer.

BACKGROUND/AIMS: Recently, several reports have recommended primary resection, rather than a staged operation, for obstructive left colon cancer. However pre-operative decompression is important for reducing complications and improving the curability of primary resection. Among the many pre-operative decompression strategies reported, we selected the long intestinal tube and evaluated the effectiveness of this convenient strategy. METHODOLOGY: A long intestinal tube was inserted pre-operatively for decompression in 27 of 29 patients undergoing resection for obstructive left colon cancer (1991-1995). We retrospectively studied the clinical features (responders vs. non-responders) of the 27 patients. We also compared these 27 with 26 other pre-1990 patients, who did not receive pre-operative decompression, in term of post-operative morbidity. RESULTS: Twelve of the 27 patients were responders; success rate 44.4%. There were no blood profile differences between responders and non-responders, but the time from bowel movement cessation to intestinal tube insertion was 3 days or less in all responders but 4 days or more in non-responders (p<0.001). There was no significant difference in the rate of post-operative morbidity between those with and without pre-operative decompression. CONCLUSIONS: Decompression is likely to be successful, allowing elective primary resection, when initiated within 3 days of bowel movement cessation. However, more than 4 days post-onset, other decompression methods or emergency surgery is necessary.

Adenocarcinoma↗
PubMed1976

Decompression-induced bubble formation in salmonids: comparison to gas bubble disease.

The relationship of gas bubble disease (GBD) in fish to decompression-induced bubble formation was investigated with salmonids. Acute bioassays were used to determine equilibration times for critical effects in fish decompressed from depths to 200 fsw. It was found that equilibration of critical tissues was complete in 60-90 min. Salmonids and air-breathers are sensitive to decompressions at similar levels of supersaturation if elimination of excess gas following decompression is unrestricted. However, if elimination is restricted, bubble formation and growth increase accordingly. Tests with mixtures of He-O2, Ar-O2, N2-O2 (80% inert gas: 20% O2) and pure oxygen demonstrated that gas solubility as well as supersaturation (delta P), pressure ratio (initial pressure: final pressure), and absolute pressure must be considered in setting tolerance limits for any decompression. Gases with higher solubility are more likely to produce bubbles upon decompression. Oxygen, however, does not follow this relationship until higher pressures are reached, probably owing to its function in metabolism and in binding with hemoglobin. Tissue responses observed in both GBD and decompressed fish involved similar pathological effects at acute exposures. The circulatory system was consistently affected by bubbles that occluded vessels and blocked flow through the heart.

Animals↗
PubMed2000

Preliminary report: long-term results of transnasal orbital decompression in malignant Graves' ophthalmopathy.

In order to demonstrate the safety and efficacy of transnasal orbital decompression for malignant Graves' ophthalmopathy, we carried out a retrospective chart review and clinical follow-up examination of 78 consecutive patients who were operated on for compressive optic neuropathy (CON) with loss of visual acuity or visual field defects. The intervention - strictly transnasal, endoscopically controlled, bilateral decompression of the medial and inferomedial wall of the orbit - was performed when medical and radiation therapy had failed. A total of 145 endonasal decompressions were performed on 78 patients (63 female, 15 male, 52. 2 +/- 10.5 yrs.) over 9 years. Of these, 65 were operated bilaterally, 15 required only unilateral decompression; 4 had repeated surgery. Visual acuity increased from an average of 0.50 +/- 0.27 (range, 0.01 - 1.25) to 0.75 +/- 0.21 (range, 0.01 - 1.25). Proptosis decreased by an average of 3.94 +/- 2.73 mm (range, -1.0 - 11.0 mm), from a mean preoperative Hertel measurement of 22.19 +/- 3. 13 mm (range, 15 - 34 mm) to a mean postoperative Hertel measurement of 18.3 +/- 2.65 mm (range, 10 - 26 mm). Ocular motility was corrected by recession of the medial rectus muscle in 58 cases, in 26 cases immediately after decompression in the same surgical session. The transnasal orbital decompression procedure improved vision, decreased proptosis in a range comparable to more invasive techniques and had favorable cosmetic results without additional disfiguring by scars. Post-decompression strabismus was successfully managed by recession of both medial orbital muscles in the same surgical session.

Decompression, Surgical↗
PubMed2000

Computation of decompression tables using continuous compartment half-lives.

There is no consensus on the number of compartments and the half-lives (T1/2) used in the calculation of inert gas exchange and decompression sickness (DCS) boundary in existing dive tables and decompression computers. We propose the use of a continuous variable for the tissue half-lives, allowing the simulation of an infinite number of compartments and reducing the discrepancy between different algorithms to a single DCS boundary expression. Our computational method is based on the premise that M-values can be expressed in terms of T1/2 and ambient pressure (D). We combined the surfaces defined by M(D,T1/2) and tissue tension H(t,T1/2) to plan decompression. The efficiency and applicability of the method is investigated with four different DCS boundaries. The first two utilize the M-value relations proposed by Bühlmann and Wienke to derive no-D limits for sea level. The third boundary is defined by a surface fitted to the empirical M-values of US Navy, Bühlmann tables, US Air Force, and our altitude diving data. This expression was used to design the decompression procedure for a multilevel dive at 11,429-ft altitude and was used in six man dives in the Kaçkar Mountains, Turkey. Although precordial bubbles were observed in two dives, there were no cases of DCS. The fourth DCS boundary is constructed with the addition of a constraint that forces calculated M-values to stay below the available M-values. This constraint aims the highest degree of "conservatism". As an application of the new boundary, the method is used to derive decompression stop diving schedules for 11,429-ft altitude. The concept of continuous tissue half-lives is applicable to different types of gas exchange and DCS boundary functions or to a combination of different models with a desired level of conservatism. It has proved to be a useful tool in planning decompression for undocumented modes of diving such as decompression stop diving or multilevel diving at altitude. The algorithm can easily be incorporated into dive computers.

Algorithms↗