We report a case of transient circulatory depression due to inadvertent apnea of a subject during decompression from a stimulated dive. The dive consisted of exposure to air at 5 bar and subsequent ...decompression stops. Arterial blood pressure and a lead II ECG were recorded continuously. During decompression from 1.6 to 1.3 bar, the subject inadvertently held his breath. Arterial pressure fell rapidly from 120/80 to 60/53 mmHg within 20 s. Recognizing that the subject held his breath, one of the supervisors ordered him to resume breathing, and arterial blood pressure was restored rapidly. This circulatory depression was probably due to reduced stroke volume such as described for the syncope of ascent: with the subject retaining his breath, the expanding lung volume increased intrathoracic pressure resulting in impaired venous return.
In five subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated ...dives consisted of exposure at rest to air at 6 bar for 30 min. corresponding to a depth of 50 m. Afterwards the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6 and 1.3 bar with a total decompression time of 73 min. Immediately after decompression and every 40 min. until the 240th min. arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min. after decompression indicating still incomplete nitrogen wash-out at least two hours after decompression had been accomplished. Bubble formation is discussed as a cause for prolonged nitrogen elimination. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest.
Testing of the blood pressure-lowering effect of a slow-release (24 hours) nifedipine preparation.
Single blind, randomized placebo controlled, single cross-over test; duration eight days.
18 ...inpatients with essential hypertension and a blood pressure of more than 160/95 mmHg.
A single 60 mg slow-release nifedipine tablet (Aprical long 60 mg) administered daily at 1800 hours. MEASURING PARAMETERS: Pulse and blood pressure measured after 3, 12, 15, 18, 20, 22 and 24 hours post-administration.
Even 18 to 24 hours after administration, the systolic blood pressure was reduced on average by 20 mmHg, the diastolic pressure by 14 mmHg. In the case of the test substance, the percentage of blood pressures in the target range (less than 160/95 mmHg) was 40 percentage points (systolic) and 49 percentage points (diastolic) higher than in the case of placebo. In 15 patients, both systolic and diastolic blood pressure was maintained within the defined target range for 24 hours. Reflex tachycardia was not observed, while other side effects such as headache, flushing, hot flashes, and leg edema occurred only rarely. There was evidence that an evening administration of the drug had a favorable effect on the morning blood pressure increase.
In 5 subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated ...dives consisted of exposure to air at 6 bar for 30 min corresponding to a depth of 50 m. Afterward the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6, and 1.3 bar with a total decompression time of 67 min. In 3 of the subjects the measurements were repeated after they had exercised (workload 75 W) during bottom time. Immediately after decompression and every 40 min until Minute 240 arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min after decompression, indicating still incomplete nitrogen washout for at least 2 h after decompression had been accomplished. We did not find any difference in PN2 values after decompression from dives at rest and after exercise. Applying a computer program based on a wide range of theoretical tissue half-times nitrogen elimination proved to be consistent with Haldanian theories when using our decompression profile. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest and after exercise.
