The Risks of Sleeping for Long Periods in the Sitting Position

People who have spent much longer than average sitting and sleeping (semi-erect), e.g. in deck-chairs, sofas, computer chairs and commercial airline seats, are more prone to suffer 'idiopathic thromboembolism' (Dalen 2003). However, because the aetiological sequence according to the VCHH is complex, only a minute proportion of 'long-sitters' may develop actual lesions, and then usually after a delay of days or weeks. Moreover, such instances cannot be predicted because different subjects respond in different ways to the same circumstances.

The key factor in reducing venous return during such 'long-sitting' episodes is not lack of muscle contractions per se, but the failure of foot pressure on the ground to compress and evacuate blood from the soles. Once blood from the vessels in the feet is expressed from foot to ankle, local muscle contractions normally elevate it progressively against gravity to calf, thigh and heart. Without the priming force of weight borne on the soles of the feet, leg movements in situ are unlikely to have much effect; venous valves in the calf cannot be expected to 'suck' blood up from the foot. In the sitting position with only a bar on which to rest the feet, or feet not touching the floor, and certainly no more than the weight of the lower leg acting on the soles, the absence of compressive weight to initiate the 'up-flow' will probably be compounded by a concomitantly lowered muscle-pump action. The weight of the column of blood in the lowermost extremity is entirely opposed to the venous return. Some sitters, such as long-distance travellers, are fidgety while others display lassitude, and such differences may affect the efficiency of venous return. All circumstances promoting lassitude are likely to combine to increase the chances of clinically significant DVT and pulmonary embolic fatality.

11.4.1.1 Traveller's Thrombosis Reconsidered

Since many older people are afraid of flight in general and high altitude transoceanic flight in particular, they may take hypnotics or lounge in an inebriated state for several hours - terrified, exhausted, drugged, or all three combined. That could be responsible for (or at least contribute to) DVT or pulmonary embolism on disembarkation. Such travellers could be inexperienced in the exigencies and difficulties of long distance air transport - sitting around in stations, cars, trains, buses and hotels on the way to major international hubs, transporting heavy luggage - and are particularly likely to suffer thromboembolic consequences.6 Thus, in addition to the distance and duration of such flights, the state of the passenger should be taken into account. All elderly, exhausted, terrified travellers, who are perhaps fearfully inebriated through excessive alcohol intake and/or may have used normal or unaccustomed doses of analgesics, tranquilisers, hypnotic medicaments, anti-nausea medication or neuroleptic drugs, should be considered at particular risk of prolonged relative insufficiency of their insensible 'peripheral venous hearts'.

Many commentators have noted that the leg/calf volume of long distance air passengers is frequently increased. Franklin (1937) remarked on such sequestration of body water in dependent legs, long before international flights figured in scientific concerns or papers. The semi-erect posture, inactive leg muscles and gravity are indisputably the main causes of limb swelling.7

6 The RAF (personal communication from Wing Commander John Aitken and William J. Coker, Occupational Health, RAF Innsworth), who transport thousands of young fit men thousands of miles, have no record of any traveller's thrombosis case; though significant numbers of troops are not currently transported further than Afghanistan and Iraq.

7 Although the venous physiological mechanism described may well be indirectly associated with many forms of fluid retention in the legs, perhaps leading to oedema and swelling, that oedema -though very common and real - is not specifically or directly related to the cause of DVT. The two

11.4.1.2 Ethnic Differences in Susceptibility to DVT

It may be pertinent that Asian peoples, who sit or squat on the ground or on cushions at ground level, are noted to suffer DVT less frequently than Western people who routinely sit on chairs with seats at average adult knee height (Chapter 1). The ground-to-heart distance in a person sitting on the ground is hardly more than 2 ft in a tall person, as against 4-5 ft in the same person standing or sitting on a chair; so the height of the venous blood column, and therefore gravitational resistance to venous return, is at least halved. Squatting precludes 'lounging' and is wholly incompatible with sleeping. Neither can one be inebriated while sitting on a cushion or the ground because it is constantly necessary to maintain the upright posture by active muscle control; in any case, alcohol is prohibited in many such communities.

Alcohol No More

Alcohol No More

Do you love a drink from time to time? A lot of us do, often when socializing with acquaintances and loved ones. Drinking may be beneficial or harmful, depending upon your age and health status, and, naturally, how much you drink.

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