Davor Eterović

Aerobic exercise before diving reduces venous gas bubble formation in humans

We have previously shown in a rat model that a single bout of high‐intensity aerobic exercise 20h before a simulated dive reduces bubble formation and after the dive protects from lethal decompression sickness. The present study investigated the importance of these findings in man. Twelve healthy male divers were compressed in a hyperbaric chamber to 280kPa at a rate of 100kPamin−1 breathing air and remaining at pressure for 80min. The ascent rate was 9mmin−1 with a 7min stop at 130kPa. Each diver underwent two randomly assigned simulated dives, with or without preceding exercise. A single interval exercise performed 24h before the dive consisted of treadmill running at 90% of maximum heart rate for 3min, followed by exercise at 50% of maximum heart rate for 2min; this was repeated eight times for a total exercise period of 40min. Venous gas bubbles were monitored with an ultrasonic scanner every 20min for 80min after reaching surface pressure. The study demonstrated that a single bout of strenuous exercise 24h before a dive to 18 m of seawater significantly reduced the average number of bubbles in the pulmonary artery from 0.98 to 0.22 bubbles cm−2(P= 0.006) compared to dives without preceding exercise. The maximum bubble grade was decreased from 3 to 1.5 (P= 0.002) by pre‐dive exercise, thereby increasing safety. This is the first report to indicate that pre‐dive exercise may form the basis for a new way of preventing serious decompression sickness.

EFFECT OF HUMAN SPLENIC CONTRACTION ON VARIATION IN CIRCULATING BLOOD CELL COUNTS

1. The human spleen sequesters 200–250 mL densely packed red blood cells. Up to 50% of this viscous blood is actively expelled into the systemic circulation during strenuous exercise or simulated apnoea (breath‐hold) diving. The contribution of splenic contraction to changes in the circulating volume of red blood cells (RBCV), as well as the venous concentration of white blood cells (WBC) and platelets (PLT), was investigated following repeated breath‐hold apnoeas.

Correlation between symptomatology and site of acute myocardial infarction.

OBJECTIVE We determined the occurrence of presenting symptoms in patients with different sites of acute myocardial infarction after controlling for age and conventional risk factors. METHODS Hospital-based study of patients hospitalized because of first anterior (n=731), inferior (n=719) and lateral (n=96) infarction in Clinical Hospital Split between 1990 and 1994. Data form about presenting symptoms and clinical profile was completed for each patient. RESULTS Anterior infarctions were more often presented by headache (adjusted odds ratio (OR)=1.67, 95% CI=1.06-2.62), weakness (OR=1.60, 95% CI=1.31-1.96), dyspnea (OR=1.40, 95% CI=1.14-1.72), cough (OR=2.24, 95% CI=1.59-3.16), vertigo (OR=2.04, 95% CI=1.40-2.99) and tinnitus (OR=2.09, 95%CI=1.06-4.14). Inferior infarctions were more often associated with epigastric (OR=1.71, 95%CI=1.30-2.24), neck (OR=1.47, 95% CI=1.10-1.98) and jaw pain (OR=2.16, 95% CI=1.42-3.27), sweating (OR=1.56, 95% CI=1.27-1.92), nausea (OR=2.01, 95%CI=l.64-2.46), vomiting (OR=1.55, 95% CI=1.22-1.97), belching (OR=1.57, 95% CI=1.21-2.03) and hiccups (OR=2.88, 95%CI=1.53-5.42). Patients with lateral infarctions were more likely to complain of left arm (OR=1.80, 95% CI=1.07-3.05), left shoulder (OR=1.82, 95% CI=1.19-2.79) and back pain (OR=2.40, 95% CI=1.28-4.46). Pain was less frequently reported by hypercholesterolemic (P=l.4x10(-7)), patients over 70 years (P=0.002), women (P=0.0007) and those with non-triggered infarction (P=0.0009), whereas those over 70 (P=1.7x10(-6)) and men (P=0.0003) were less likely to report other relevant symptoms. CONCLUSIONS Our study suggests a linkage between different infarction sites and specific groups of symptoms. Furthermore, coronary patients should give their full attention to non-specific symptoms and any kind of discomfort.

Dermatological indicators of coronary risk: a case-control study

OBJECTIVE We examined the association of dermatological signs such as baldness, thoracic hairiness, hair greying and diagonal earlobe crease with the risk of myocardial infarction in men under the age of 60 years. METHODS A hospital-based, case-control study included 842 men admitted for the first non-fatal myocardial infarction, the controls were 712 men admitted with noncardiac diagnoses, without clinical signs of coronary disease. The relative risks were estimated as odds ratios. Logistic regression was used to control for the confounding variables. RESULTS Baldness, thoracic hairiness and earlobe crease were approximately 40% more prevalent in cases (P<10(-6) in each case). In both cases and controls, baldness and thoracic hairiness were frequently coexistent, as well as hair greying and earlobe crease (P<10(-4) in each case). After allowing for age and other established coronary risk factors, the relative risk of myocardial infarction for fronto-parietal baldness compared with no hair loss was 1.77 (95% CI 1.27-2.45) and it was 1.83 (95 CI 1.4-2.3) for men with thick, extended thoracic hairiness. The presence of a diagonal earlobe crease yielded a relative risk of 1.37 (95% CI 1.25-1.5), while hair greying was associated with myocardial infarction only in men under the age of 50 years. CONCLUSION It appears that baldness, thoracic hairiness and diagonal earlobe crease indicate an additional risk of myocardial infarction in men under the age of 60 years, independently of age and other established coronary risk factors.

Restoration of hemodynamics in apnea struggle phase in association with involuntary breathing movements

Involuntary breathing movements (IBM) that occur in the struggle phase of maximal apneas produce waves of negative intrathoracic pressure. This could augment the venous return, increasing thereby the cardiac output and gas exchange, and release the fresh blood from venous pools of spleen and liver. To test these hypotheses we used photoplethysmography and ultrasound for assessment of hemodynamics and spleen size before, during and after maximal dry apneas at large lung volume in 7 trained divers. During the easy-going phase cardiac output was reduced about 40%, due to reduction in stroke volume and in presence of reduced inferior vena cava venous return, while the spleen contracted for about 60 ml. Towards the end of the struggle phase, in presence of intense IBM, the spleen volume further decreased for about 70 ml, while cardiac output and caval flow almost renormalized. In conclusion, IBM coincide with splenic volume reduction and restoration of hemodynamics, likely facilitating the use of the last oxygen reserves before apnea cessation.

Gender differences in triggering of acute myocardial infarction

The frequencies of potential triggers of acute myocardial infarction differ between men and women. There is a possibility that anti-ischemic drugs protect against trigger-related infarctions.

PYELOLITHOTOMY IMPROVES WHILE EXTRACORPOREAL LITHOTRIPSY IMPAIRS KIDNEY FUNCTION

PURPOSE Extracorporeal shock wave lithotripsy (ESWL) causes acute depression of kidney function, which chronically returns to baseline levels. This sequala could indicate chronic regression of acute lesions or a balance between lesions and relief of obstruction. We compared changes in kidney function 1 week and 3 months after ESWL and pyelolithotomy. MATERIALS AND METHODS A group of 17 women and 13 men 28 to 71 years old with 0.6 to 3 cm. stones received 1,800 to 3,200 shock waves by an electromagnetic lithotriptor. Another group of 21 women and 9 men 35 to 76 years old with 2.5 to 3.8 cm. stones underwent Gil-Vernet intra-sinus pyelolithotomy. Split renal plasma flow, glomerular filtration rate and mean parenchymal transit times of nonreabsorbable filtrate solutes were measured by dual gamma camera renography, and plasma clearances of 99mtechnetium diethylenetriaminepentaacetic acid and 131orthoiodohippurate acid. RESULTS ESWL caused acute deterioration and chronic restoration of baseline parameters of the treated kidney, and small but sometimes irreversible damage to plasma flow to the untreated kidney, especially in obese patients. In contrast, pyelolithotomy acutely and chronically improved function of the treated kidney, and normalized parenchymal transit times of radiotracers. CONCLUSIONS ESWL does not achieve substantial improvements in kidney function, which can be achieved by other methods of stone removal.

The effects of low-dose epinephrine infusion on spleen size, central and hepatic circulation and circulating platelets

In several conditions associated with adrenergic stimulation, an increase in peripheral count of larger platelets has been observed, but the mechanism remained elusive. Larger platelets have greater prothrombotic potential and increase the risk of acute thrombotic events. The human spleen retains one‐third of total body platelets, with mean volume (MPV) about 20% greater than that of circulating platelets. We aimed to answer whether low‐dose epinephrine infusion results in spleen contraction and MPV increase. We undertook the continuous ultrasonic measurements of spleen volume, hepatic and central circulation with concurrent blood sampling in response to intravenous infusion of epinephrine (6 min of 0·06 µg kg−1 per min, followed by 3 min of 0·12 µg kg−1 per min) in nine healthy young subjects. The spleen volume started to decrease immediately after the onset of infusion, in the presence of substantial decreases in peripheral resistance and mean blood pressure and increases in heart rate and cardiac output. The majority of spleen emptying, approximately 25%, (95% CI 71·3–299·7) was observed 1 min after infusion onset, the hepatic vein flow peaked at the end of infusion for 28·4% (95% CI 1074·6–407·9), while increases in platelet count for approximately 31% (95% CI 187·8–314·8) and MPV for 4·4% (95% CI 7·3–10·9) lagged until 1 min after infusion cessation. We suggest that spleen is a dynamic reservoir of large platelets, which are mobilized even by low‐dose epinephrine infusion in conditions of decreased blood pressure.

Triggers of acute myocardial infarction regarding its site.

We have studied the incidence of possible triggers of the myocardial infarction regarding its site in 750 patients with anterior and 731 patients with inferior infarction. Infarctions occurred most frequently without recalling any triggering activity, especially in patients with anterior infarction (67 vs. 44%). Physical effort as the possible precipitator was also more frequent in anterior infarctions (22 vs. 16%). However, the onset of inferior infarction was more frequent during meteorological stress (9 vs. 2%), emotional stress (10 vs. 3%), after overeating (13 vs. 3%) and nicotine abuse (6 vs. 1.5%). These triggers were independent and highly significant (P < 0.02 in each case) discriminators of the site of myocardial infarction. Bimodal circadian rhythm, with primary peak between 6 and 9 h a.m. and the secondary peak between 3 and 6 p.m. was observed in patients which did not recall any triggering activity, and this was more pronounced in patients with inferior infarction. These results support the hypothesis that the influence of the vegetative tone is most pronounced in the onset of myocardial infarction of inferior wall.

Effects of Hemodialysis and Anemia on Pulmonary Diffusing Capacity, Membrane Diffusing Capacity and Capillary Blood Volume in Uremic Patients

The study aimed at investigating pulmonary function in uremic patients, emphasizing the lung diffusing capacity for CO (DLCO) and its membrane and pulmonary capillary blood volume (Vc) components. The study sample comprised 25 uremic patients without clinical/radiological evidence of lung disease. They were enrolled in a chronic hemodialysis (HD) program and had anemia requiring transfusions. The subjects were tested for their lung function before and after both a first HD and a HD with blood transfusion (BT) that followed a few days later. After HD-induced removal of body fluid, and increase in pre-HD reduced forced vital capacity, alveolar volume and mid-expiratory flow rate (FEF25-75%) was observed. HD-induced DLCO decrease (p less than 0.005) was observed and was related to decreased Vc. The second HD with BT increased DLCO, due to partially normalized Hb. On average, a 7.2% DLCO increase corresponded to each 10-g/l Hb rise. In conclusion, (1) the beneficial effect of HD in uremic patients reverts the small-airway obstruction; (2) the lower values of DLCO in these patients are due to reduced Hb and HD causes further DLCO reduction via decrease of Vc, and (3) HD with BT still increases DLCO because improvement of Hb predominates.