Chest Compression in Newborn Infants: What anatomical structures are we compressing?
- georgschmoelzer
- 16 hours ago
- 3 min read
What is already known
Current neonatal resuscitation guidelines recommend delivering chest compressions (CC) over the lower third of the sternum, a recommendation largely derived from imaging studies in older infants and children, with very limited newborn-specific data.
What this study adds
Using transthoracic echocardiographic mapping in healthy term newborns, we found that the left ventricle (LV) is consistently located at the inter-nipple line along the 4th–5th left sternal border, rather than directly beneath the midline of the sternum.
Why this question matters
Approximately 1% of newborn infants require chest compressions at birth. The goal of CC is to restore systemic circulation and coronary perfusion during cardiac arrest. Traditionally, this is explained by two mechanisms:
Cardiac pump theory – the heart is compressed between the sternum and spine, ejecting blood forward.
Thoracic pump theory – compressions raise intrathoracic pressure, creating pressure gradients that drive blood flow.
Understanding which cardiac structures actually lie beneath the recommended compression site is fundamental to knowing how CC work in newborns—and whether current practices truly optimize blood flow.
What we did
We conducted a prospective observational study in two large maternity hospitals in Edmonton, Canada. Fifty healthy term newborns (37–41+6 weeks’ gestation) underwent detailed transthoracic echocardiography within the first 1–2 days after birth.
By carefully mapping standard echocardiographic views (parasternal long axis, parasternal short axis, apical four-chamber, and subcostal views) onto the chest wall, we precisely projected the location of the left and right ventricles relative to surface landmarks such as:
The sternum
The inter-nipple line
The xiphisternum
This approach allowed us to determine which cardiac structures lie beneath the lower third of the sternum in newborns.
What we found
Although the lower third of the sternum overlaps longitudinally with the heart, the left ventricle is rarely located directly beneath the sternal midline. Instead:
The LV was located:
At the 4th left sternal border in 44% of newborns
At the 5th left sternal border in 50%
Overall, the LV consistently projected left of the sternum, along the inter-nipple/midclavicular line.
As a result, midline chest compressions over the lower third of the sternum are most likely to compress:
The right atrium and right ventricle
The great veins
The ascending aorta
—not the left ventricle itself.
Why this is important
These findings challenge the long-held assumption that neonatal CC directly squeeze the left ventricle, as proposed by the cardiac pump theory. Instead, our data support the idea that thoracic pump mechanisms, global increases in intrathoracic pressure, may play a dominant role in generating blood flow during neonatal resuscitation.
This aligns with growing experimental and clinical evidence showing improved hemodynamics and faster return of spontaneous circulation with continuous chest compressions combined with sustained inflation (CC+SI). By increasing intrathoracic pressure and promoting passive lung aeration, CC+SI may better exploit thoracic pump physiology in newborns.
Take-home message
In newborn infants, chest compressions delivered at the currently recommended lower third of the sternum are unlikely to directly compress the left ventricle. Instead, they primarily affect right-sided cardiac structures and the great vessels.
Together with emerging physiological and clinical data, these anatomical insights suggest that both the optimal compression site and the compression-to-ventilation strategy in neonatal resuscitation deserve renewed scrutiny. Rethinking how and where we compress the newborn chest may be key to improving blood flow and outcomes during the most critical moments after birth.
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