A 21-year-old male with no past medical history and no regular medications was brought to the emergency department via ambulance after experiencing a 10 second episode of unconsciousness at home, following the smoking of a waterpipe containing tobacco. Prior to collapsing, the patient reported a sudden onset of dizziness and mild headaches. The patient denied experiencing angina pectoris, dyspnea, or palpitations. The family history was positive for coronary artery disease on the father’s side. Upon their arrival, the ambulance team documented the patient’s vital signs, including a temperature of 36.0 °C, heart rate of 125/min, respiratory rate of 18/min, blood pressure of 180/130 mmHg, and a pulse oximetry reading of 94% while breathing room air. As far as we know, the carbon monoxide (CO) levels in the patient’s home were not dangerously high, as they did not trigger the alarm of the CO detector carried by the ambulance team set to 60 ppm.

Upon evaluation, the patient was found to be conscious and fully aware, scoring 15 on the Glasgow coma scale. No physical injuries were observed as a result of the fall.

An electrocardiogram (ECG) showed sinus tachycardia with 125/min with frequent ventricular extrasystoles (VES), normal axis, normal P, PQ, ORS-segments, and also normal ST/T segments and QT time. The APACHE II Score added up to a 6 and the poison severity score on admission added up to 3.

The patient reported a history of tobacco use, consuming one pack daily over the past 3 years. Additionally, he smokes a water pipe approximately three times a week. He also disclosed the consumption of 2–3 units of alcohol on 1–2 occasions weekly. The use of recreational drugs was denied.

Furthermore, the patient’s complete blood count, serum chemistry panel, and cardiac enzyme levels were all within normal limits and showed no abnormalities. The results of the urine drug panel were also unremarkable.

The first arterial blood gas (ABG) (Fig. 1.) was obtained 2 h after arrival in the emergency department, which revealed a COHb of 30.4%, pH 7.42, pCO2 39.9 mmHg, pO2 91.4 mmHg, and a Lactate of 1.0 mmol/l. As a result, the patient was promptly started on oxygen therapy using a simple face mask and was then transported to the next hyperbaric oxygen therapy (HBO) center.

Arterial blood gas showing a CO-Hb of 30.4%

Upon admission to the hyperbaric center, the COHb was measured to be 17.2%. The HBO therapy was initiated nearly 4 h after the patient’s initial admission to the ED, by which time the patient's headaches had already subsided.

The patient underwent three hyperbaric oxygen therapy sessions, each lasting for 145 min at 2.4 atmospheres with 100% FiO2. Following the completion of the therapy, the patient was released and exhibited no symptoms or complaints. His vital signs before discharge were unremarkable.

Two and a half years after the incident, the patient participated in an interview to discuss his experience. He reported that the symptoms initially manifested as a brief episode of dizziness and headache, followed by a rapid loss of consciousness. Upon receiving oxygen, the patient experienced a slight improvement in his condition. Subsequent hyperbaric oxygen therapy (HBOT) led to a marked recovery, with the patient becoming symptom-free after completion of the treatment course. Normal pulse rate was restored after the entire therapy was concluded.

The patient continues to engage in water pipe smoking, albeit less frequently and exclusively outdoors. The incident did not result in any alterations in his behavior or that of his friends and acquaintances. Furthermore, the patient reported no noticeable long-term health complications, such as memory impairment, heart palpitations, or an increase in the frequency of illness or common cold, following the incident.