Cardiopulmonary consequences of decompression stress

Area of Science:

• Cardiopulmonary physiology
• Hyperbaric medicine
• Diving physiology

Background:

• Clinically undetectable venous gas emboli (VGE) are common after hyperbaric decompression.
• The cardiopulmonary effects of these VGE during uneventful decompression are not well understood.

Purpose of the Study:

• To investigate the cardiopulmonary effects of clinically uneventful decompression in unanesthetized sheep.
• To assess the impact of venous gas emboli on gas exchange and hemodynamics.

Main Methods:

• Unanesthetized sheep were instrumented for hemodynamic and blood gas monitoring.
• Animals underwent hyperbaric exposure (6.03 ATA) or a control period (1 ATA).
• Measurements included pulmonary artery pressure, cardiac output, blood gases, and Doppler bubble detection.

Main Results:

• Venous gas emboli (VGE) were detected in all hyperbaric-exposed animals.
• Cardiac output (CO) decreased by 20% and pulmonary vascular resistance (PVR) increased by 60% post-decompression.
• These hemodynamic changes exceeded predictions, but gas exchange and ventilation/perfusion (V/Q) scans remained normal.

Conclusions:

• Clinically uneventful decompression stress significantly alters cardiac output and pulmonary vascular resistance in sheep.
• Hemodynamic changes occur without detectable impairment in gas exchange.
• These findings highlight subclinical cardiopulmonary effects of decompression.