Thoracic and abdominal lymph drainage in relation to mechanical ventilation and PEEP

Thoracic and abdominal lymph flow have been studied in 25 dogs. Thoracic lymph flow (TLF) was found to be (mean +/- s.e. mean) 6.1 +/- 1.4 ml/h before, and 29 +/- 4.6 ml/h after the induction of lung damage with oleic acid. TLF was depressed by 50% both before and after lung damage, when a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) was applied. This suggests impeded drainage of the lung tissue. Spontaneous breathing, compared to mechanical ventilation, significantly increased TLF by approximately 70%. Abdominal lymph flow increased from 61 +/- 5.3 ml/h to 111 +/- 12.6 ml/h, when a PEEP of 1.0 kPa was applied. These findings demonstrate that PEEP may contribute to oedema in a surgical area. It is concluded that increased intrathoracic pressure reduces TLF, and spontaneous breathing increases TLF, as compared to mechanical ventilation without PEEP.