Abstract
BackgroundA congenital diaphragmatic hernia (DH) can result in severe lung hypoplasia that increases the risk of morbidity and mortality after birth; however, little is known about the cardiorespiratory transition at birth.MethodsUsing phase-contrast X-ray imaging and angiography, we examined the cardiorespiratory transition at birth in rabbit kittens with DHs. Surgery was performed on pregnant New Zealand white rabbits (n=18) at 25 days’ gestation to induce a left-sided DH. Kittens were delivered at 30 days’ gestation, intubated, and ventilated to achieve a tidal volume (Vt) of 8 ml/kg in control and 4 ml/kg in DH kittens while they were imaged.ResultsFunctional residual capacity (FRC) recruitment and Vt in the hypoplastic left lung were markedly reduced, resulting in a disproportionate distribution of FRC into the right lung. Following lung aeration, relative pulmonary blood flow (PBF) increased equally in both lungs, and the increase in pulmonary venous return was similar in both control and DH kittens.ConclusionThese findings indicate that nonuniform lung hypoplasia caused by DH alters the distribution of ventilation away from hypoplastic and into normally grown lung regions. During transition, the increase in PBF and pulmonary venous return, which is vital for maintaining cardiac output, is not affected by lung hypoplasia.
Highlights
A congenital diaphragmatic hernia (DH) can result in severe lung hypoplasia that increases the risk of morbidity and mortality after birth; little is known about the cardiorespiratory transition at birth
Whole-lung volumes were significantly reduced in DH kittens (51 ± 3 μl/g) compared with those in controls (67 ± 2 μl per g body weight, Po0.05)
Computed tomography analysis revealed that reduced lung development in DH kittens was mostly limited to the left lower lobe, the left upper lobe was affected to a lesser degree (Figure 2)
Summary
A congenital diaphragmatic hernia (DH) can result in severe lung hypoplasia that increases the risk of morbidity and mortality after birth; little is known about the cardiorespiratory transition at birth. METHODS: Using phase-contrast X-ray imaging and angiography, we examined the cardiorespiratory transition at birth in rabbit kittens with DHs. Surgery was performed on pregnant New Zealand white rabbits (n = 18) at 25 days’ gestation to induce a left-sided DH. Kittens were delivered at 30 days’ gestation, intubated, and ventilated to achieve a tidal volume (Vt) of 8 ml/kg in control and 4 ml/kg in DH kittens while they were imaged. Relative pulmonary blood flow (PBF) increased in both lungs, and the increase in pulmonary venous return was similar in both control and DH kittens. CONCLUSION: These findings indicate that nonuniform lung hypoplasia caused by DH alters the distribution of ventilation away from hypoplastic and into normally grown lung regions. The increase in PBF and pulmonary venous return, which is vital for maintaining cardiac output, is not affected by lung hypoplasia
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