Cardio-respiratory interactions in acute asthma

Abstract

Asthma encompasses of respiratory symptoms that occur intermittently and with varying intensity accompanied by reversible expiratory airflow limitation. In acute exacerbations, it can be life-threatening due to its impact on ventilatory mechanics. Moreover, asthma has significant effects on the cardiovascular system, primarily through heart-lung interaction-based mechanisms. Dynamic hyperinflation and increased work of breathing caused by a sharp drop in pleural pressure, can affect cardiac function and cardiac output through different mechanisms. These mechanisms include an abrupt increase in venous return, elevated right ventricular afterload and interdependence between the left and right ventricle. Additionally, Pulsus paradoxus, which reflects the maximum consequences of this heart lung interaction when intrathoracic pressure swings are exaggerated, may serve as a convenient bedside tool to assess the severity of acute asthma acute exacerbation and its response to therapy.

Keywords: asthma; heart-lung interaction; hyperinflation dynamics; pleural pressure; spontaneous ventilation.

FIGURE 1

The increase in pulmonary vascular resistances (PVR) from Zone west 3 to zone West 1. in the upper zones (zones 1 of West), the alveolar pressure (Palv) is higher than the intravascular pressure (PAP and PVP) and occludes the intra-alveolar vessels, in the lower zones (zones 3 of West) the intravascular pressure is higher than the alveolar pressure and the vascular resistances are weak. The regimen is intermediate in the middle zones (zones 2 of West).

FIGURE 2

Reproduced with permission of the ^© ERS 2023: European Respiratory Journal December 2013, 42 (6) 1,696–1,705; DOI: 10.1183/09031936.00138912). Relationships between pulmonary vascular resistances and lung volume (see text for detailed explanations). FRC, functional residual capacity; TLC, total lung capacity; RV, residual volume.

FIGURE 3

Reproduced with permission of the ^© ERS 2023: European Respiratory Journal December 2013, 42 (6) 1,696–1,705; DOI: 10.1183/09031936.00138912. Recording of arterial pressure measured using an arterial catheter in a patient with acute exacerbation of airway obstruction. Pulsus paradoxus is present as the decrease in systolic arterial pressure is >10 mmHg (about 17 mmHg). Note that the arterial pulse pressure also decreases at inspiration suggesting that LV stroke volume decreases at inspiration. The grey areas indicate the inspiratory phases (Insp).