Hemodynamic effects of high frequency oscillatory ventilation with volume guarantee in a piglet model of respiratory distress syndrome

Abstract

Respiratory failure is a common condition faced by critically ill neonates with respiratory distress syndrome (RDS). High frequency oscillatory ventilation (HFOV) is often used for neonates with refractory respiratory failure related to RDS. Volume guarantee (VG) mode has been added to some HFOV ventilators for providing consistent tidal volume. We sought to examine the impact of adding the VG mode during HFOV on systemic and cerebral hemodynamics, which has not been studied to date. A neonatal piglet model of moderate to severe RDS was induced by saline lavage. Piglets (full term, age 1-3 days, weight 1.5-2.4 kg) were randomized to have RDS induced and receive either HFOV or HFOV+VG (n = 8/group) or sham-operation (n = 6) without RDS. Cardiac function measured by a Millar® catheter placed in the left ventricle as well as systemic and carotid hemodynamic and oxygen tissue saturation parameters were collected over 240 min of ventilation. Mean airway pressure, alveolar-arterial oxygen difference and left ventricular cardiac index of piglets on HFOV vs. HFOV+VG were not significantly different during the experimental period. Right common carotid artery flow index by in-situ ultrasonic flow measurement and cerebral tissue oxygen saturation (near-infrared spectroscopy) significantly decreased in HFOV+VG at 240 min compared to HFOV (14 vs. 31 ml/kg/min, and 30% vs. 43%, respectively; p<0.05). There were no significant differences in lung, brain and heart tissue markers of oxidative stress, ischemia and inflammation. HFOV+VG compared to HFOV was associated with similar left ventricular function, however HFOV+VG had a negative effect on cerebral blood flow and oxygenation.

Fig 1. Timeline of experimental protocol.

Baseline is at end of stabilization, and time 0 is at end of saline lung lavage with 60 min intervals afterwards ending at 240 min. Euthanasia and tissue harvesting occurred after 240 min collections. RL, Ringer’s Lactate; ABG, arterial blood gas.

Fig 2

Changes in (A) alveolar-arterial oxygen difference (AaDO₂) and (B) mean airway pressure. Comparing sham-operated, high frequency oscillatory ventilation (HFOV), and HFOV with volume guarantee (+VG) groups. Data presented as mean with standard deviation error bars. *p<0.05 vs. respective baseline; ^#p<0.05 vs. both HFOV and HFOV+VG groups.

Fig 3

Changes in (A) amplitude and (B) tidal volume. Comparison between high frequency oscillatory ventilation (HFOV) and HFOV with volume guarantee (+VG) groups. Data presented as mean with standard deviation error bars. *p<0.05 vs. HFOV group.

Fig 4

Changes in (A) right common carotid blood flow index and (B) brain oxygen saturation (near-infrared spectroscopy). Comparing sham-operated, high frequency oscillatory ventilation (HFOV), and HFOV with volume guarantee (+VG) groups. Data presented as mean with standard deviation error bars. *p<0.05 vs. respective baseline; ^#p<0.05 vs. HFOV+VG group. CrSO₂ = infrared spectroscopy of cerebral oxygen saturation.

Fig 5

Changes in (A) cardiac index, (B) stroke volume, (C) tau, and (D) dP/dt max. Comparing sham-operated, high frequency oscillatory ventilation (HFOV), and HFOV with volume guarantee (+VG) groups. Data presented as mean with standard deviation error bars. ^#p<0.05 vs. both HFOV and HFOV+VG groups.

Fig 6

Bar plot showing immediate post-mortem lung tissue analysis for (A) IL-8 and (B) TNF-α. Comparing sham-operated, high frequency oscillatory ventilation (HFOV), and HFOV with volume guarantee (+VG) groups. Data presented as mean with standard deviation error bars. ^#p<0.05 vs. both HFOV and HFOV+VG groups.