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Effect of change in tidal volume on left to right shunt across ventricular septal defect in children - A pilot study
Pravin Pathak1, Sambhunath Das1, Saurabh Kumar Gupta2
1Department of Cardiac Anaesthesia, CNC, All India Institute of Medical Sciences, New Delhi, India.
Insights
Lowering tidal volumes (VT) in children with ventricular septal defects (VSD) reduces pulmonary blood flow and airway pressure. This approach may be beneficial for VSD management.
Area of Science:
- Pediatric Cardiology
- Respiratory Physiology
- Critical Care Medicine
Background:
- Pulmonary vascular resistance is a key factor in shunting across ventricular septal defects (VSD).
- Pulmonary vascular resistance increases at the extremes of lung volumes.
Purpose of the Study:
- To investigate the impact of varying tidal volumes (VT) on pulmonary blood flow (Qp), systemic blood flow (Qs), and shunt (Qp/Qs) in pediatric VSD patients.
- To assess hemodynamic changes in response to different VT settings.
Main Methods:
- A prospective observational study was conducted on 30 children undergoing VSD surgical closure.
- Transthoracic echocardiography was used to measure hemodynamic and shunt parameters at VT of 10, 8, and 6 ml/kg, maintaining constant minute ventilation.
Main Results:
- Decreasing VT from 10 to 6 ml/kg significantly reduced the gradient across the VSD (23.5 to 13 mmHg) and peak airway pressure (17.2 to 14.5 cmH2O).
- Pulmonary blood flow (Qp) and systemic blood flow (Qs) progressively declined with lower VT.
- The pulmonary to systemic blood flow ratio (Qp/Qs) showed a slight increasing trend with reduced VT.
Conclusions:
- Lower tidal volumes effectively decrease the VSD gradient, pulmonary blood flow, and peak airway pressure in children with VSD.
- Ventilation strategies employing lower VT and higher respiratory rates, while maintaining adequate minute ventilation, may be advantageous for VSD patients.
- Further research is warranted to validate these preliminary findings.
Background:
Pulmonary vascular resistance, an important determinant of shunting across ventricular septal defects (VSD), rises at both extremes of lung volume.
Aims:
We sought to determine the effect of changes in tidal volumes (VT) on pulmonary blood flow (Qp), systemic blood flow (Qs), and shunt (Qp/Qs) in children with VSD.
Setting:
Single-center teaching hospital.
Design:
Prospective observational study.
Methods:
Thirty children with a mean age of 11.8 ± 5 months undergoing surgical closure of VSD were studied. Hemodynamics and shunt-related parameters were assessed using transthoracic echocardiography measured at three different VT i.e. 10, 8, and 6-ml/kg keeping the minute ventilation constant.
Results:
Reduction in VT from 10 to 8 to 6 ml/kg led to a reduction in gradient across VSD measuring 23.5, 20 and 13 mmHg respectively (P < 0.001). Similarly, right ventricluar outflow tract (RVOT) diameter, RVOT velocity time integral, Qp (57.3 ± 18.1, 50.6 ± 16.9, 39.9 ± 14.7 mL; P < 0.001), Qs (24.1 ± 10.4, 20.0 ± 8.7, 15.3 ± 6.9 mL; P < 0.001) and peak airway pressure (17.2 ± 1.5, 15.8 ± 1.3, 14.5 ± 1.2 cmHg; P < 0.001) showed progressive decline with decreasing VT from 10 to 8 to 6 ml/kg, respectively. However, Qp/Qs (2.4 ± 0.4, 2.6 ± 0.4, 2.6 ± 0.4) demonstrated a minor increasing trend.
Conclusion:
Lower VT reduces the gradient across VSD, the pulmonary blood flow, and the peak airway pressure. Hence, ventilation with lower VT and higher respiratory rate maintaining adequate minute ventilation might be preferable in children with VSD. Further studies are required to confirm the findings of this pilot study.
