The effect of intermittent positive-pressure respiration on the speed of blood-flow in the deep veins of the lower limb

Deep vein thrombosis in patients with neuromuscular disease who undergo tracheotomy with positive pressure ventilation

“…In another study of patients with underlying intensive care with ventilator use, 23.6% of patients had DVT detected 11 . Ventilator use can cause a reduction in venous return and prolonged immobility 12 . The high prevalence of DVT in our patients might have been caused by TPPV.…”

The Prevention of Deep Vein Thrombosis After Surgery

“…That there is a reduced velocity in blood flow after surgery has been confirmed by Doran, Drury and Sawyer (1964); the time of the greatest reduction of velocity, however, was not associated with the period when the majority of thrombi are known to form. Dyde and Bethel (1968) suggested that modern anaesthetic techniques may even aggravate the situation; using radioactive tracers to measure venous blood velocity, they found that transit times were increased when the surgery was performed under anaesthesia incorporating intermittent positive pressure ventilation. For these reasons it is customary to try to achieve early ambulation after surgery.…”

A clinical trial designed to test the relative value of two simple methods of reducing the risk of venous stasis in the lower limbs during surgical operations, the danger of thrombosis, and a subsequent pulmonary embolus, with a survey of the problem

“…The venous return was grossly delayed whether the intermittent positivepressure respiration was applied manually or mechanically. Further tests performed by Dyde and Bethel (1968) on 17 patients undergoing 'minor' surgery demonstrated that intermittent positivepressure respiration did not cause venous stasis, but only if the pressure peak was kept down to 9-15 cm. of water.…”

“…Therefore in a patient having a major abdominal operation the venous return from the lower limbs depends on the output of the left ventricle per beat and that fraction of the systolic pressure which filters across the capillary bed. The output of the heart can be reduced by halothane because it is hypotensive and by a fall in the partial carbon-dioxide pressure (Dyde and Bethel, 1968). Browse's (1962) studies showed that in 75 per cent of patients the blood-flow through the calf was reduced to half its preoperative volume.…”