RESPIRATORY DISORDERS - Medicine for Mountaineering and Other Wilderness Activities - page 244

Prolongedimmobility,suchasbeingstormboundfordaysinasmalltent,immobileand
resting in cramped awkward positions
Carrying heavy packs or standing immobile for long periods of time, which increase
stasis in the legs
Trauma to the pelvis or legs, which increases the tendency for clotting
Oralcontraceptives thatcontainestrogencauseaslightincreaseintheincidence ofven-
ous thrombosis and pulmonary embolism, although the increase is far less than that asso-
ciated with pregnancy. However, no evidence indicates that these drugs increase the risk
of thrombosis and embolism at altitude above the risk at sea level, at least in nonsmokers.
Smokers definitely have an increased risk. Women taking such drugs may wish to consider
replacing them with an oral contraceptive that contains only progesterone several months
before a climb to altitudes above 18,000 feet (5500 m).
Diagnosis of Venous Thrombosis
Themostcommonsymptomofvenousthrombosisisdeep,achingpaininthecalf,inner
sideofthethigh,orbackoftheknee.Thepainfrequentlycomesonsuddenlyandisaggrav-
ated by walking. When the thrombosed vein is located in the calf, the overlying muscles
are tender. Flexing the foot upward may cause pain in the calf. Usually the affected leg is
swollen, which can be detected by measuring the circumference of both legs at identical
five-inch intervals from the ankle to the upper thigh. A difference in circumferences of 0.5
inch is common and of no significance; greater differences are cause for concern. A slight
fever is sometimes present and lasts an average of seven to ten days. Blood clots in the
veins ofthe thighs orpelvis may notcause obvioussymptoms butmay break offandtravel
to the lung causing pulmonary embolism. Consequently, if a person is in pulmonary dis-
tressandotherpulmonarydisordersdonotappeartobepresent,pulmonaryembolismmust
be suspected even though signs of venous thrombosis are absent.
Diagnosis of Pulmonary Embolism
Pulmonary embolism is heralded by the sudden onset of pain in the chest. The respir-
atory and pulse rates are usually increased, and a slight fever is frequently present. Later
the pain becomes pleuritic and is aggravated by respiration, particularly deep breathing. A
cough often is present and may produce bloody sputum. Signs of consolidation (increased
or absent breath sounds and dullness to percussion) may appear over the involved area a
day or so after onset.
If the embolus obstructs a large pulmonary artery, the initial symptom may be the sud-
den onset of a sense of suffocation rather than pain. More severe shortness of breath, cy-
anosis, distension of neck veins, and signs of shock follow shortly. Pleuritic pain, cough,
bloody sputum, and signs of consolidation usually develop a few hours later, although the