[Work at high altitudes: risk factors and health surveillance]. / Il lavoro in alta quota: fattori di rischio e sorveglianza sanitaria.

Work at high altitude (elevation equal to or greater than 3000 m above sea level) results in a physiological adaptation of the human organism to changing environmental conditions. The main problem related to the altitude is represented by the reduction of partial pressure of oxygen (hypoxia). Our study takes into consideration occupational risk factors: those related to physical environment of high altitude; those related to the worker; those related to the characteristics of the job. It is finally addressed the decision making process related to the formulation of the judgment of suitability for performance of work activities at high altitude. The health protocol proposed requires an accurate anamnestic investigation aimed at gathering information on pre-existing pathophysiological conditions that need, once identified, clinical and instrumental tests specific and targeted. These clinical protocols are analyzed and proposed for the main pathophysiologic conditions that pose a risk to health at high altitude.

Italian high altitude laboratories: past and present.

Italy is a mountainous country with a total of 88 huts and bivouacs at altitudes higher than 3,000 m. Starting in the 19th century a great deal of research in high altitude pathophysiology has been carried out in Italy and many Italian physicians have been involved in mountain medicine. Most of the Italian research has been carried out at two locations: the scientific laboratories "Angelo Mosso" on Monte Rosa (Capanna Regina Margherita and Laboratorio Angelo Mosso), and the "Pyramid" in Nepal. The Capanna Regina Margherita, located on the top of Punta Gnifetti (Monte Rosa, 4,559 m), was inaugurated in 1893. With the support of Queen Margherita of Savoy, an Observatory for scientific studies was built beside this hut in 1894. In 1980 the hut was completely rebuilt by the Italian Alpine Club. The Istituto Angelo Mosso at Col d'Olen, at the base of Monte Rosa (at 2,900 m) was inaugurated in 1907. The high altitude laboratory named the "Pyramid" was built in 1990. Made of glass and aluminium, this pyramid-shaped structure is situated in Nepal at 5,050 m. The scientific laboratories "Angelo Mosso" on Monte Rosa (mainly the Capanna Regina Margherita) and the Pyramid form a nucleus for high altitude research: the former is especially devoted to research regarding acute mountain sickness and the response to subacute hypoxia, whereas the latter is a unique facility for research responses to chronic hypoxia, the effect of exposure to very high altitude, and the study of the resident population living in the Himalayas for at least 25,000 years.

Systemic arterial hypertension and small airways function: acute effects of diazoxide and furosemide.

Two groups of 10 patients with systemic arterial hypertension were studied by respiratory function tests before and after acute administration of diazoxide or furosemide. Small airways obstruction was present in a high percentage of patients and was partially reversed after the acute administration either of diazoxide or of furosemide. Systemic arterial hypertension seems to influence small airways caliber, through pulmonary vascular distension and/or pulmonary interstitial edema.

The effects of exposure to moderate altitude on cardiovascular autonomic function in normal subjects.

Cardiovascular responses to altitude have been studied on well-trained young subjects, generally at high altitudes (>4000 m). Less known are the effects of exposure to lower altitudes, easily reached by the general population. The aim of the study was to evaluate the effects of exposure to a moderate altitude (2950 m) on heart rate (HR), blood pressure (BP) profile, and cardiovascular autonomic function, and their correlation with hemoglobin oxygen saturation (HbO2S), in untrained subjects of a wide age range. Twenty-seven healthy normotensive subjects (age range 6-83; 8 children, 9 adults, and 10 elderly subjects) underwent a battery of noninvasive cardiovascular reflex tests and 24-h ambulatory BP monitoring. Corrected QT interval was also calculated. HbO2S was measured with a transcutaneous oxymeter. All measurements were performed at about 200 m (s.l.) and repeated at 2950 m. 24-h HR and systolic/diastolic BP mean values increased at 2950 m in children (% change respectively: 6.4 +/- 6.4, p<0.05; 6.5 +/- 4.0/13.5 +/- 6.9, p < 0.05), adults (4.9 +/- 8.1, NS; 6.0 +/- 5.1/8.1 +/- 5.8, p < 0.05), and elderly subjects (7.2 +/- 4.8, p < 0.05; 5.1 +/- 2.3/2.8 +/- 4.1, p < 0.05 for systolic BP only). Standard deviation of BP mean values increased during night-time in the adult group (p < 0.05). All subjects scored normal cardiovascular test results and no differences were observed after exposure to 2950m, at both 1 hour and 24 hours from arrival. After exposure to altitude, HbO2S decreased significantly in the three groups, both on arrival and after 24 hours. No correlation was found between changes in HbO2S and BP/HR responses, and cardiovascular test results. In conclusion, exposure to moderate altitudes, easily and often reached by the general population, causes a small but significant increase in BP and HR in healthy untrained subjects of a wide age range (6-83 years). Some physiological factors (eg, lower environmental temperature and lifestyle modification) together with hypoxia, possibly more than altered cardiovascular reactivity, seem responsible for this cardiovascular change. In terms of end-organ damage, the clinical relevance of this increase in BP and BP variability for repeated exposure is not known.

Use of corrected QT interval in autonomic function testing: assessment of reproducibility.

QT interval duration is influenced by the autonomic nervous system and has been proposed as an additional tool in the diagnosis of diabetic autonomic neuropathy. The study aimed to assess in normal subjects the reproducibility of QT interval duration compared with that of cardiovascular tests commonly used to explore the function of the autonomic nervous system. Fifty-nine healthy subjects (31 males, 28 females; mean age 35.1 +/- 17.7 years) performed five cardiovascular tests: deep breathing test (DBT), lying to standing test (LST), Valsalva manoeuvre (VM), postural blood pressure test (PBPT) and cough test (CT). QT interval duration was measured on an electrocardiogram (ECG) registered after a 15-min rest in the supine position. Corrected QT interval (QTc) was calculated according to Bazett's formula. The QTc interval duration for each subject was expressed as the mean of the QTc calculated by two observers. Each subject was submitted to the cardiovascular test battery and the ECG twice in 1 week. The coefficient of variation (CV) was calculated to assess the reproducibility. The observed CV values were as follows: DBT 15.8%, LST 8.0%, VM 9.5%, CT 7.2%, PBPT 176%, QTc 3.4%. Our data confirm the reproducibility of heart rate cardiovascular tests: the QTc interval is a reproducible, easily measurable parameter, which has the advantage of not requiring patient cooperation.