Preoperative pulmonary hemodynamics determines changes in airway and tissue mechanics following surgical repair of congenital heart diseases

Abstract

To characterize the effect of changes in pulmonary hemodynamics on airway and tissue mechanics, forced oscillatory input impedance of the respiratory system (Zrs) was measured between 0.4-12 Hz in two groups of children undergoing surgical repair of congenital heart disease (CHD) immediately before sternotomy and after chest closure during short apneic intervals. Children with lesions associated with high pulmonary blood flow and/or pressure (septal defects; HP group, n = 12) and children with hypoperfused lungs (tetralogy of Fallot; LP group, n = 12) were included in the study. Airway resistance (Raw), and coefficients of respiratory tissue damping (G) and elastance (H), were estimated from Zrs by model-fitting. A postoperative reduction in pulmonary blood flow and/or pressure in the HP group resulted in an immediate decrease in Raw of 29 +/- 9 (SE)% (P < 0.05), whereas children in the LP group had increases in Raw (24 +/- 17%, no significance) after surgery. No significant change was observed in G in either the HP (6.4 +/- 13%) or LP (27 +/- 23%) group, while H increased in children of both the HP (23 +/- 8%, P < 0.05) and LP (36 +/- 7%, P < 0.01) groups. These results suggest that the preoperative pulmonary hemodynamic condition determines changes in airway mechanics: surgical repair of CHD leads to an improvement in airway function only in children with congested lungs. The adverse effects of surgery, mechanical ventilation, and/or cardiopulmonary bypass may be responsible for the increased stiffness of the respiratory system observed in both groups of children.

Effects of Acute Blood Volume Expansion on Respiratory Mechanics in the Rat

“…The previous results were obtained mostly in children undergoing cardiac open-chest surgery, before and after highly invasive surgical maneuvers required to correct congenital heart defects [6,7,8,9]. Moreover, in our experiments, data were obtained from individual healthy rats under control conditions and immediately after acute BVE, so that each rat was its own control, and the possible confounding effects of chronic modifications of pulmonary parenchyma and/or vasculature were avoided.…”

“…This aspect has been studied mainly in infants with various congenital heart defects causing different ratios of pulmonary to systemic blood flow [1,2,3,4,5], and in infants after surgical correction of left to right shunts [6,7], after induction of a left to right shunt [8], or correction of pulmonary hyper- or hypoperfusion [9]. The results of these studies suggest that a high pulmonary blood flow may be associated with increased pulmonary elastance and airway resistance [10,11].…”

Post Operative Pulmonary Complications Following Surgery for Congenital Heart Disease

“…Many of the patients have preexisting lung issues related with CHD 6 . In addition, CHD is often associated with an impaired pulmonary hemodynamic condition that has a great effect on the mechanical properties of the lung 7,8 .…”

Ventilating the Lungs Safely: What’s New for Infants and Children?

“…Although all inflation maneuvers improve oxygenation by increasing the arterial oxygen tension, decreasing atelectasis [10,11] and restoring end-expiratory lung volume, they differ in their effects to increase afterload on the right ventricle and thus, impair cardiac output [12,13]. However, a recent systematic review on the hemodynamic effects of alveolar recruitment maneuvers performed in adult patients with acute lung injury demonstrated that hemodynamic instability was transient, and hypoxemia was self-limited without serious short-term sequelae [14].…”