Oxygen Concentration Rise During a Multiplace Treatment
During a multiplace chamber treatment at 2.4 ATA with six patients, the chamber oxygen concentration rises to 23.8% shortly after a patient removes his oxygen mask to vomit. One patient has a chest tube with a Heimlich valve, another has an external fixator, and a third is receiving an antibiotic infusion via a pressure-rated IV pump. The chamber operator notices the oxygen reading and asks the attending physician whether to continue compression. The treatment is for a necrotizing soft tissue infection in the first patient, who is hemodynamically stable but febrile. The chamber has a built-in purge system.
1. What are your immediate actions regarding the oxygen reading and fire risk?
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Treat 23.8% as an incipient fire hazard. Stop compression, have the patient replace the mask or use the built-in breathing system properly, and purge or ventilate the chamber with air to bring oxygen below 23.5%, ideally below 23%. Reduce any free-flow oxygen, check for leaks, and verify the analyzer calibration. Do not ignore a transient rise because a mask slipped-vomiting, mask removal, and poor fit are common causes. Announce the problem to the occupants, keep them calm, and document the event. The judgment is that the fire triad of oxygen, fuel, and ignition is dynamic; a single high reading mandates action before continuing.
2. Should the treatment be aborted, and how would you decide?
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Abort if oxygen cannot be promptly reduced below 23.5%, if there is any ignition source or smoke, or if the patient's condition-vomiting, airway compromise-makes continued pressurization unsafe. If the purge quickly restores a safe reading and the patient is stable, you may continue with heightened monitoring, but the threshold for aborting should be low in a multiplace chamber with six patients. Decompression must follow the treatment table's abort procedure to avoid decompression sickness in attendants and patients. The decision balances infection control against fire risk; fire risk wins. Notify the medical director and complete an incident report.
3. How should the chest tube with a Heimlich valve and the external fixator be managed during pressure changes?
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A Heimlich valve is a one-way valve and can work in a chamber, but trapped air and pressure changes can cause tension pneumothorax if the valve malfunctions or the tube kinks. Confirm the tube is patent, the valve is oriented correctly, and the patient has no worsening dyspnea; monitor during ascent and descent. The external fixator may contain sealed air spaces or batteries; check manufacturer guidance and avoid trapping gas. If the chest tube is connected to suction, it must be converted to a valve or water seal for the chamber. The judgment is to identify every gas-filled space and device before compression, not just the obvious oxygen mask.