Splenic contraction, catecholamine release, and blood volume redistribution during diving in the Weddell seal.

The spleen of the Weddell seal (Leptonychotes weddelli) may contract and inject red blood cells (RBCs) into the peripheral circulation during diving, but evidence for this hypothesis is indirect. Accordingly, we measured splenic dimensions by ultrasonography, plasma catecholamine concentrations, hemoglobin concentration, and hematocrit in five Weddell seals before and after intravenous epinephrine during halothane anesthesia and while awake at the surface after voluntary dives. Spleen size was reduced immediately after epinephrine injection or after the seal surfaced. Within the first 2 min after the seal surfaced, cephalocaudal splenic length was 71 +/- 2% (mean +/- SD; P < 0.05) and splenic thickness was 71 +/- 4% (P < 0.05) of the maximal resting values. Splenic size increased (half-time = 6-9 min) after the seal surfaced and was inversely correlated with plasma epinephrine and norepinephrine concentrations. Hemoglobin concentration increased from 17.5 +/- 5.3 g/dl (measured during general anesthesia) to 21.9 +/- 3.7 g/dl (measured in the first 2 min after surfacing). At these same times, the hematocrit increased from 44 +/- 12 to 55 +/- 8%. These values decreased (half-time = 12-16 min) after the seal surfaced. We estimate 20.1 liters of RBCs were sequestered at rest, presumably in the spleen, and released either on epinephrine injection or during diving. Catecholamine release and splenic contraction appear to be an integral part of the voluntary diving response of Weddell seals.

Myoglobin saturation in free-diving Weddell seals.

Although the consumption of myoglobin-bound O2 (MbO2) stores in seal muscles has been demonstrated in seal muscles during laboratory simulations of diving, this may not be a feature of normal field diving in which measurements of heart rate and lactate production show marked differences from the profound diving response induced by forced immersion. To evaluate the consumption of muscle MbO2 stores during unrestrained diving, we developed a submersible dual-wavelength laser near-infrared spectrophotometer capable of measuring MbO2 saturation in swimming muscle. The probe was implanted on the surface of the latissimus dorsi of five subadult male Weddell seals (Leptonychotes weddelli) released into a captive breathing hole near Ross Island, Antarctica. Four seals had a monotonic decline of muscle O2 saturation during free diving to depths up to 300 m with median slopes of -5.12 +/- 4.37 and -2.54 +/- 1.95%/min for dives lasting < 17 and > 17 min, respectively. There was no correlation between the power consumed by swimming and the desaturation rate. Two seals had occasional partial muscle resaturations late in dives, indicating transfer of O2 from circulating blood to muscle myoglobin. Weddell seals partially consume their MbO2 stores during unrestrained free diving.

Hormonal regulatory adjustments during voluntary diving in Weddell seals.

Subadult male Weddell seals were instrumented with microcomputer-based backpacks and were then monitored during voluntary diving and recovery periods in McMurdo Sound, Antarctica. Depth and duration of diving, swim speed, and dive pattern were routinely monitored. An indwelling venous catheter was used to collect plasma samples at various time periods before and following diving episodes, so that changes in plasma concentrations of hormones and of metabolites could be measured. Adrenergic and nitroxidergic regulatory effects were assessed indirectly by measuring concentration changes in catecholamine and cyclic guanosine monophosphate (cGMP), respectively. The studies found that (i), except for dives of less than several minutes, epinephrine and norepinephrine both increased as a function of diving duration, then rapidly decreased during recovery (with a half time of about 10 min), (ii) that the changes in catecholamine concentrations correlated with splenic contraction and an increase in circulating red blood cell mass (hematocrit), (iii) that the changes in catecholamines, especially [epinephrine], were inversely related to insulin/glucagon ratios, which mediated a postdiving hyperglycemia, and (iv) that in long dives (but not short ones) the changes in catecholamines correlated with increasing reliance on anaerobic metabolism, indicated by increased plasma lactate concentrations. These diving-catecholamine relationships during voluntary diving at sea were similar to those observed during enforced submergence (simulated diving) under controlled laboratory conditions. At the end of diving, even while catecholamine concentrations were still high, many of the above effects were rapidly reversed and the reversal appeared to correlate with accelerated nitric oxide production, indirectly indicated by increased plasma cGMP concentrations. Taken together, the data led to the hypothesis of important adrenergic regulation of the diving response in seals, with rapid reversal at the end of diving and during recovery being regulated by nitroxidergic mechanisms.

HA-1A in septic patients with ARDS: results from the pivotal trial.

OBJECTIVE: To evaluate the effects of HA-1A, a human monoclonal antiendotoxin antibody, in septic patients with ARDS. DESIGN: Substudy of a multicenter, double-blinded, placebo-controlled trial of HA-1A in septic patients. PATIENTS: 63 septic patients with ARDS at the time of study entry. INTERVENTION: A single intravenous injection of HA-1A (100 mg) or placebo. RESULTS: A quantitative radiographic score, the PaO2/FIO2 ratio and an index of the severity of ARDS did not show a significant difference between the treatment and placebo groups at 3, 5 and 7 days after treatment. The duration of endotracheal intubation did not differ between the two groups. 15 of 30 HA-1A treated patients (50%) and 23 of 33 placebo-treated patients (69.7%) died within 28 days. The daily mortality was always lower in the HA-1A group, but this difference was not statistically significant at 28 days. The 28-day survival curves for the two treatment groups adjusted by covariate analysis were not significantly different (p = 0.07). Using logistic regression, a significant independent effect of HA-1A treatment was detected upon the early survival rate at 7 days (p = 0.03) but not at 14 and 28 days. CONCLUSION: A single injection of HA-1A in septic patients with ARDS did not reverse acute respiratory failure or improve long-term survival.

Continuous pulse oximetry in the breath-hold diving women of Korea and Japan.

Arterial oxygen saturation during breath-hold diving has not previously been measured continuously. We devised a submersible, waterproof, backpack computer to continuously record heart rate, depth, and arterial oxygen saturation (SPO2) as determined by earlobe pulse oximetry. Our measurements showed that one assisted (Funado) diver had reduced SPO2 values immediately after surfacing from 22 dives which lasted 23-76 s, from a mean of 99 +/- 1% SPO2 to 96 +/- 3% SPO2. SPO2 returned to 97 +/- 2% within 15 s after surfacing (P < 0.05 surface value differs from predive base line). Four unassisted (Cachido) divers showed no significant reduction of mean predive SPO2 below 98 +/- 2% at any time during the dive or recovery period in 92 routine dives lasting from 15 to 44 s. Upon surfacing from diving, mean SPO2 was 98 +/- 2% and the mean SPO2 15 s after surfacing was 97 +/- 3% for the unassisted divers. Three Cachido divers were asked to dive and breath hold for as long as possible. Mean SPO2 at the conclusion of breath holding was 73% after an average dive and breath hold lasting 69 s.

Arterial blood gas tensions during breath-hold diving in the Korean ama.

Korean female unassisted divers (cachido ama) breath-hold dive > 100 times to depths of 3-7 m during a work day. We sought to determine the extent of arterial hypoxemia during normal working dives and reasonable time limits for breath-hold diving by measuring radial artery blood gas tensions and pH in five cachido ama who dove to a fixed depth of 4-5 m and then continued to breath hold for various times after their return to the surface. Eighty-two blood samples were withdrawn from indwelling radial artery catheters during 37 ocean dives. We measured compression hyperoxia [arterial PO2 = 141 +/- 24 (SD) Torr] and hypercapnia (arterial PCO2 = 46.6 +/- 2.4 Torr) at depth. Mean arterial PO2 near the end of breath-hold dives lasting 32-95 s (62 +/- 14 s) was decreased (62.6 +/- 13.5 Torr). Mean arterial PCO2 reached 49.9 +/- 5.4 Torr. Complete return of these values to their baseline did not occur until 15-20 s after breathing was resumed. In dives of usual working duration (< 30 s), blood gas tensions remained within normal ranges. Detailed analysis of hemoglobin components and intrinsic oxygenation properties revealed no evidence for adaptive changes that could increase the tolerance of the ama to hypoxic or hypothermic conditions associated with repetitive diving.

Portable airway-suction systems: a comparison of performance.

UNLABELLED: A number of portable suction systems (powered either manually, pneumatically, or electrically) are available. We compared the performance of three electric systems (Laerdal Medical LSU, Laerdal Medical CSU, and Matrx Medical) and two manual systems (Vitalograph Emergency Aspirator and California Medical V-VAC) to wall suction set at maximum pressure of 300 torr [39.9 kPa]. METHODS: We determined the maximum pressure each system was capable of generating, and we measured the volume of imitation maple syrup each system at maximum pressure could suction within 5 seconds and the time required by each system at maximum pressure to suction 150 mL of syrup. In addition, we evaluated the life of each electric system's internal battery. RESULTS: All the electric systems were capable of generating suction pressure greater than 300 torr [39.9 kPa]. The amount of time required by the electric systems to suction 150 mL of syrup was not significantly different from that required by wall suction. In 5 seconds, wall suction suctioned a significantly greater volume of syrup than did the Matrx Medical system (p less than 0.05, ANOVA), but a significantly smaller volume of syrup than did the Laerdal Medical CSU system (p less than 0.05, ANOVA). The manual Vitalograph Emergency Aspirator was capable of generating 300 torr [39.9 kPa] pressure, but the California Medical V-VAC was not. Wall suction significantly outperformed both of the manual systems when volume of syrup suctioned in 5 seconds and time required to suction 150 mL of syrup were compared (P less than 0.05 ANOVA). All electric systems were capable of maintaining maximum suction greater than 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)