Alternating versus synchronous ventilation of left and right lungs in piglets

Abstract

Objective." We tested whether alternating ventilation (AV) of each lung (i. e. with a phase difference of half a ventilatory cycle) would decrease central venous pressure and so increase cardiac output when compared with simultaneous ventilation (SV) of both lungs.Theory: If, during AV, the inflated lung expands partly via compression of the opposite lung, mean lung volume will be smaller during AV than SV. As a consequence, mean intrathoracic pressure (as cited in the literature), and therefore, central venous pressure will be smaller. Design:The experiments were performed in seven anaesthetized and paralyzed piglets using a doublepiston ventilator. Minute ventilation was the same during AV and SV. Starting at SV, we alternated three times between AV and SV for periods of 10 min.Results: During AV, central venous pressure was decreased by 0.7 mmHg and cardiac output was increased by 10+4.4~ (mean, + SD) compared with SV. AV also resulted in increased arterial pressure. During one-sided inflation with closed outlet of the opposite lung, a pressure rise occurred in the opposite lung, indicating compression. Conclusion:The higher cardiac output during AV than SV can be explained by the fact that central venous pressure is lower during AV. This lower central venous pressure is very probably due to the lower mean intrathoracic pressure caused by compression of the opposite lung during unilateral inflation.

Cross-talk between the lungs in piglets

“…In our two previous studies we found a ratio between right and left V T at a ventilatory rate of 10pbm of 1.30+0.11 [5] and 1.21+0.07 [6], which together give a value of 1.25+0.10, which is equal to the value in the present study of 1.24_+0.10. In our previous paper we regarded the ratio between the two lung volumes as the same as the ratio between both tidal volumes.…”

“…The details of the surgery have been described previously [5,6]. Twenty young female pigs of 11.0 + 1.0 kg (mean_+ sd) body weight (BW) were anaesthetized with an intraperitoneal injection of 30 mg pentobarbital sodium (Abbott/Sanofi, Maassluis, The Netherlands) per kg BW.…”

“…Paw l and Paw r were measured in the endobronchial tube and the trac}ieal cannula, respectively. We checked for an airtight fit by unilateral ventilation at the closed airway of the opposite lung [5]. Inspection after all of the experiments revealed the location of the opening of the endobronchial tube between the carina and the first bronchial branch to the left cranial lobe.…”

“…The hypothesis that the higher cardiac output during AV compared to SV in both lungs is due to a lower mean central venous pressure as a consequence of a lower intrathoracic pressure, caused by a lower mean thoracic volume, has been challenged and verified previously [5,6]. To explain the lower mean thoracic volume during AV compared to SV, we hypothesized that, during AV, the inflated lung will expand partly by compression of the opposite lung and the remainder by expansion of the thorax.…”

“…It does not change cardiac output when compared to conventional, common ventilation of both lungs [3,4]. Recently, we observed a lower central venous pressure and higher cardiac output during alternating differential ventilation (AV) of both lungs compared to synchronous differential ventilation (SV) [5]. During AV, the start of inflation of one lung is half a ventilatory cycle out of phase with that of the other lung, i.e.…”