Certified Hyperbaric Registered Nurse (CHRN): Clinical Decisions and Practice Guide Study Guide

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A learner groups all early chamber treatments as equally established. Reorganize the timeline around the transition from speculative applications to decompression treatment, followed by evidence-based investigation of oxygen-mediated effects in other illnesses.

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An experienced ward nurse joins a hyperbaric service. Build orientation around adapting familiar assessment and emergency skills to pressure changes, limited physical access, oxygen exposure, and chamber-specific equipment rather than repeating general nursing content alone.

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A sea-level chamber gauge indicates 14.7 psig. Using an ambient pressure of 14.7 psia, add the two values to obtain 29.4 psia, approximately 2 ATA, before applying Boyle's or Dalton's law.

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A training profile lists 20 metres of seawater at sea level. Approximate the hydrostatic contribution as 2 atmospheres, then add 1 atmosphere at the surface to obtain 3 ATA for subsequent gas calculations.

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A freely flexible 30 mL air pocket starts at 1 ATA and reaches 2.5 ATA at the same temperature. Calculate 30 divided by 2.5: its predicted volume is 12 mL if no gas escapes.

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Compare a sealed flexible pocket moving from 4 to 3 ATA with another moving from 2 to 1 ATA. The second undergoes the larger proportional expansion, despite both pressure decreases being one atmosphere.

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At 2.4 ATA, a patient breathing a dry mixture containing 50% oxygen has a calculated inspired oxygen partial pressure of 1.2 ATA. Another person breathing chamber air at the same pressure receives a lower oxygen partial pressure.

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Two attendants breathe air at the same chamber pressure, but one remains much longer. Henry's law predicts the same equilibrium direction; the longer exposure allows more time for tissues to approach that higher dissolved-nitrogen level.

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A patient reports warmth during compression and chill during decompression without other symptoms. Explain the expected gas-temperature changes, reassess comfort, and use only chamber-approved comfort measures while continuing observation for unrelated clinical causes.

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A flexible gas reservoir warms from 20°C to 40°C at constant pressure. Use 313.15 divided by 293.15 to predict approximately a 7% volume increase; using 40 divided by 20 would incorrectly predict doubling.

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A patient has a normal baseline saturation and asks why hyperbaric oxygen could add benefit. Explain that saturation estimates hemoglobin occupancy, whereas increased oxygen pressure also raises oxygen dissolved in plasma and changes tissue oxygen gradients.

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A patient with a poorly healing foot wound has signs of impaired arterial inflow. Explain why vascular assessment and possible restoration of blood flow remain necessary even when adjunctive hyperbaric oxygen is being considered.

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A drowsy patient receiving supplemental oxygen has a reassuring saturation but increasingly shallow breathing. Reassess airway and ventilation and escalate the change; oxygenation data alone cannot establish effective carbon dioxide elimination or adequate respiratory function.

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Two deep-exposure plans use different nitrogen and helium fractions. Explain why their narcotic effects and decompression planning cannot be treated as interchangeable, even if both mixtures provide an acceptable oxygen partial pressure for their intended use.

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A diver's symptoms lessen during recompression. Explain that pressure-related bubble reduction is only part of treatment; oxygen-supported inert-gas elimination and reassessment of remaining tissue injury still matter when judging progress and subsequent management.

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A crush-injury patient has marked swelling, and a colleague assumes any vasoconstriction must worsen hypoxia. Explain the combined effects of increased dissolved oxygen and reduced capillary filtration while preserving urgent evaluation for compartment syndrome.

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A rapidly progressive soft-tissue infection is referred for adjunctive treatment. Coordinate chamber preparation with the surgical and antimicrobial plan, recognizing that oxygen-mediated effects support treatment but do not remove necrotic tissue or establish source control.

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A wound's oxygen measurement improves during an initial exposure, but its dimensions are unchanged afterward. Explain that an acute oxygen response demonstrates immediate physiology; it does not establish completed vascular remodeling or predict an immediate change in wound size.

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A previously ischemic flap has restored inflow but remains clinically compromised. Explain why renewed circulation does not guarantee immediate recovery and why an adjunctive plan may address reperfusion-associated injury while the team continues assessing flap viability.

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An attendant completes a longer air exposure than planned at the same chamber pressure. Reassess decompression requirements using the actual exposure duration; an unchanged maximum pressure does not establish an unchanged inert-gas burden or decompression obligation.

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A learner argues that any residual tissue nitrogen after ascent means decompression sickness. Explain the difference between expected off-gassing and symptomatic illness, then assess an actual patient's exposure and clinical findings rather than diagnosing from theory alone.

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An inside attendant is assigned a second air exposure after a short surface interval. Preserve the first profile and surface-interval record, then apply the service's designated repetitive-exposure procedure before deciding whether the new schedule is suitable.

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A practice profile gives a maximum depth and an exposure duration between listed entries. Before selecting a row, identify the supplied table's edition, units, time definition, and rounding instructions, then document the resulting choice and reasoning.

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Assume sea-level air dives, no earlier residual nitrogen, maximum depth 57 fsw on both dives, and compliance with the edition's travel-rate rules. First-dive bottom time is 19 minutes 30 seconds: round to 20 minutes, use 60 fsw, and select the 22-minute entry, giving group D. After exactly one hour at the surface, the 0:53–1:47 interval changes D to C. For the second dive, group C at 60 fsw supplies 19 minutes residual nitrogen. With 25 minutes actual bottom time, equivalent single dive time is 19 + 25 = 44 minutes. This remains below the 63-minute no-stop limit; the next longer group entry is 45 minutes, giving H. No mandatory decompression stop is generated by this example, but controlled ascent remains required.

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A diver's arm tingling disappears after emergency oxygen. Record the initial symptom distribution and recovery timeline, continue the arranged evaluation, and communicate the oxygen response rather than cancelling assessment because the current examination appears improved.

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A referral requests treatment for a wound without describing perfusion, cause, infection status, or prior care. Obtain those details so the team can determine whether an evidence-supported indication applies and what other treatment must continue.

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Two family members develop headache and nausea after using a generator near an enclosed space, yet display saturations of 99%. Treat the shared exposure as significant and pursue appropriate carbon monoxide assessment rather than relying on conventional oximetry.

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A patient had collapse and confusion after a combustion exposure but arrives after prolonged oxygen with a modest carboxyhemoglobin result. Communicate the earlier neurological findings and treatment timeline when arranging specialist assessment of possible hyperbaric treatment.

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A diabetes-related foot ulcer remains unhealed despite documented standard care and has an ischemic component. Present adjunctive hyperbaric assessment as a conditional option, while continuing vascular evaluation and wound care and explaining uncertainty about individual benefit.

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A crushed limb is swollen and increasingly painful. Support immediate surgical evaluation for compartment syndrome while the team considers adjunctive hyperbaric treatment; do not make completion of a chamber session a prerequisite for resolving a mechanical emergency.

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A patient with suspected clostridial myonecrosis is being prepared for surgical treatment. Coordinate any proposed chamber therapy around urgent source control and antimicrobials, maintaining communication about instability, transport requirements, and changes in the operative plan.

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A postoperative flap develops concerning perfusion changes. Notify the surgical team and clarify the cause promptly, then coordinate adjunctive hyperbaric assessment if indicated rather than assuming additional oxygen alone will correct the new circulation problem.

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A patient with exceptional blood-loss anemia is discussed for temporary hyperbaric support. Explain how increased dissolved oxygen differs from raising hemoglobin, and coordinate treatment with the plan to control bleeding and address the anemia itself.

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Compare a brief high-partial-pressure exposure with a much longer lower-partial-pressure exposure. Assess both pressure and time, then distinguish acute neurological warning signs from evolving respiratory symptoms rather than assigning risk from concentration alone.

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An oxygen-filled monoplace patient reports lip twitching and then develops generalized convulsions before applying the air mask. Activate the coordinated medical response, hold pressure, and monitor seizure activity and spontaneous breathing; do not expect the unconscious patient to apply a mask. Prepare for airway support and patient access, using available approved gas-switching capabilities. In a multiplace chamber, the inside attendant can remove the oxygen hood, clear accessible hazards, and protect the head without restraining the patient or placing objects in the mouth. After convulsions cease, reassess airway, breathing, consciousness, and glucose. Persistent absent breathing requires immediate coordinated airway and ventilation management rather than passive observation.

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After repeated oxygen exposures, a patient reports progressive dry cough and discomfort with breathing. Review cumulative exposure and arrange assessment for pulmonary toxicity and alternative cardiopulmonary causes rather than treating the complaint as an isolated neurological reaction.

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During an air break at 2.5 ATA, a patient breathes air rather than pure oxygen. Explain that chamber pressure has not fallen, but the calculated dry inspired oxygen partial pressure decreases from 2.5 ATA to approximately 0.525 ATA.

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A patient develops unilateral ear pain early in compression and cannot equalize gently. Communicate immediately, interrupt the pressure increase according to procedure, and reassess before continuing instead of urging a stronger forced maneuver through pain.

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A ventilated patient develops evidence of airway obstruction before decompression. Correct and reassess ventilation with the chamber team before proceeding; a planned pressure reduction can expand trapped gas and turn an airway problem into pulmonary overpressure injury.

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A new support device contains an air-filled compliant reservoir. Before admitting it, determine how pressure affects that reservoir, whether gas can safely vent, and which manufacturer-approved preparation and monitoring steps apply throughout compression and decompression.

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A patient reports gradually blurred distance vision across a prolonged course but no acute neurological symptoms. Document the pattern and arrange review, while explaining why sudden visual change during treatment would require a different immediate assessment.

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A patient with known ventricular dysfunction develops new breathlessness after a session. Obtain prompt clinical assessment and communicate the cardiac history and symptom timing rather than assuming the discomfort is an expected reaction to the confined environment.

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A critically ill patient is considered for a monoplace chamber. Determine how monitoring, ventilation, infusions, communication, and emergency access will function with the patient physically separated from staff, rather than assuming an inside attendant can intervene.

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A patient asks why an apparently harmless personal item is restricted. Explain that ordinary materials and small ignition sources can behave differently in oxygen-enriched conditions, then replace the item with an approved alternative when one is available.

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A returning patient arrives wearing the usual gown but has applied a new topical preparation beneath a dressing. Review the actual product and dressing against approved chamber requirements before treatment instead of relying on the previous session's clearance.

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A clinician proposes taking a grounded portable monitor into the chamber. Verify its approval for the intended hyperbaric environment and installation requirements before admission; attaching a grounding connection does not establish that its battery and circuitry are suitable.

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A chamber oxygen monitor trends upward while every patient's saturation remains stable. Investigate breathing-system leakage and environmental controls through the established response procedure; patient saturation does not explain or neutralize the atmospheric fire hazard.

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During preparation, an operator notices a new defect near a viewport seal. Remove the chamber from routine use pending appropriate evaluation and communicate the finding instead of treating a successful pressure test yesterday as current clearance.

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During a drill, staff discover that the planned emergency monitor cannot connect until decompression is complete. Revise equipment placement and assigned roles so the response matches actual access and compatibility rather than a theoretical bedside sequence.

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A replacement cylinder has a familiar color but a different contents label. Stop the connection process, verify the specified gas and approved supply arrangement, and resolve the discrepancy before relying on it for treatment or emergency reserve.

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A probe placed beside a plantar ulcer shows improved oxygen tension during testing. Describe the finding as an adjacent-skin response and combine it with the wound and vascular assessment rather than reporting a direct measurement of the ulcer bed.

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During normobaric testing, a stable reading suddenly rises when the fixation-ring edge lifts, without a corresponding patient change. Ambient air entering the sensor interface is a specific suspected artifact. Assess the patient, inspect the interface, recalibrate, replace the ring, restore contact liquid and reattach the sensor. Allow stabilization again. Return toward the previous value supports an interface error; a persistent abnormal result requires assessment for physiological change.

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A patient's periwound reading rises substantially during oxygen exposure while the ulcer remains infected and repeatedly traumatized. Explain that the physiological response is encouraging but does not remove the need to address infection and mechanical injury before expecting healing.

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A patient taking glucose-lowering medication arrives having missed breakfast and reports shakiness. Measure glucose and assess intake and medication timing before treatment, then manage the finding under the service's procedure rather than relying on yesterday's uneventful session.

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A patient returns after a new subclavian line placement and reports chest discomfort. Communicate the procedure and symptoms and obtain assessment for a possible thoracic complication before the next exposure rather than carrying forward the earlier clearance.

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A foot ulcer remains unchanged despite repeated sessions, and the patient continues to load the affected area. Reassess mechanical protection and the broader wound plan with the team instead of assuming additional oxygen exposure alone will overcome repeated injury.

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An anxious patient fears being unable to signal from a monoplace chamber. Demonstrate the communication system, rehearse the agreed signal, explain observation arrangements, and ask the patient to describe what to do if ear pain develops.

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Before treating a ventilated patient with continuous infusions, trace each support system through the chamber interface. Confirm compatible equipment, observation, alarm communication, access arrangements, and the response to interrupted ventilation or infusion before the chamber is pressurized.

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A young child cannot reliably describe ear pain or use the adult communication script. Develop age-appropriate preparation and observable distress cues, verify equipment fit, and establish with the team how compression will be interrupted if equalization appears unsuccessful.

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A patient referred for elective treatment reports previous bleomycin and new exertional breathlessness. Compare respiratory findings with baseline, obtain the oncology treatment record and arrange physician assessment before proceeding. Chest imaging and pulmonary-function testing may help evaluate suspected injury. Previous exposure alone does not establish a lifelong absolute contraindication: a 15-patient case series described treatment under special precautions without persistent pulmonary complications, although its size and retrospective design limit certainty. [Original case series](https://pubmed.ncbi.nlm.nih.gov/23045915/).