Clinical recommendations for high altitude exposure of individuals with pre-existing cardiovascular conditions

Abstract

Take home figureAdapted from Bärtsch and Gibbs2 Physiological response to hypoxia. Life-sustaining oxygen delivery, in spite of a reduction in the partial pressure of inhaled oxygen between 25% and 60% (respectively at 2500 m and 8000 m), is ensured by an increase in pulmonary ventilation, an increase in cardiac output by increasing heart rate, changes in vascular tone, as well as an increase in haemoglobin concentration. BP, blood pressure; HR, heart rate; PaCO2, partial pressure of arterial carbon dioxide.

Blood pressure at high altitude: physiology and clinical implications

“…However, the foremost factor underlying physiological responses to HA is the low atmospheric pressure and the consequent proportional reduction of oxygen partial pressure in the inspired air (hypobaric hypoxia; FIGURE 1). 1,2 This occurs even though the relative air composition remains the same as at sea level, with oxygen content being about 21%. The ensuing hypoxemia and tissue hypoxia trigger numerous regulatory mechanisms, which in most cases favor adaptation but may sometimes evolve into pathological conditions such as acute mountain sickness (AMS) or chronic mountain sickness (Monge disease).…”

“…This raises several questions such as: 1) whether the effect of altitude exposure is the same as in healthy young people; 2) whether the extra burden imposed on the cardiovascular system to achieve acclimatization may be detrimental in these patients; and 3) whether treated hypertensive individuals should modify antihypertensive therapy to prevent excessive BP increase and, if yes, how. 2 Focusing on elderly individuals, it is widely accepted that BP increases with age because of the combined effect of atherosclerotic changes, large artery stiffening, renal function impairment, and arterial baroreflex dysfunction, with older people having on average higher systolic BP values than younger ones. 41,42 Few studies evaluated the effects of altitude exposure in the elderly, sometimes with conflicting results, and most of them focused on moderate altitude instead of HA.…”

“…The topic of patients with preexisting cardiovascular conditions who wish to reach HA locations has been extensively discussed in a recent consensus statement of experts and scientific societies. 2 In fact, even if the increase in BP observed during HA exposure, although important, should not, per se, represent a risk for a healthy person, this may not necessarily be true for diseased individuals. For example, hypertensive patients may be more susceptible to normalizing BP increase at altitude for the metabolic demands imposed by exercise, BP trajectories of hypertensive lowlanders exercising at altitude are shifted upwards and become steeper compared with those observed at sea level.…”

“…39,49 A summary of recently published practical recommendations for patients with hypertension who are planning an HA stay is presented in TABLE 1. 2 Conclusions The cardiovascular system responds to the challenge of HA exposure in a complex manner, usually leading to adaptation, but in some cases contributing to acute and chronic altitude -related pathological conditions. The responses of BP and of its regulatory mechanisms to HA are significantly modified by the duration of the exposure.…”

Effects of baseline heart rate at sea level on cardiac responses to high-altitude exposure

“…However, after a few days of acclimatization (3-5 days), the CO begins to decrease and returns to baseline level with a higher HR and a lower SV [7]. The increase in HR is mainly due to sympathetic activation [8], whereas the decrease in SV is attributed to a decrease in blood volume, an increase in mPAP, the impairment of myocardial relaxation and an increase in HR, all of which contribute to the altered filling patterns of both ventricles [9]. During these physiological processes, the change in HR seems to be a critical determinant of cardiac performance at HA.…”