Case Report
Acute carbon monoxide poisoning treatment by non-invasive CPAP-ventilation, and by reservoir face mask: Two simultaneous cases

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Abstract

Carbon monoxide (CO) is a leading cause of morbidity and mortality. Treatment focuses on the rapid elimination of CO and management of hypoxia. Oxygen is the cornerstone of therapy, and usually applied via a reservoir face mask. Hyperbaric oxygen therapy eliminates CO faster, but requires extensive equipment and expertise. Non-invasive continuous positive airway pressure (CPAP) ventilation using a tight mask provides a higher inspired fraction of oxygen (FiO2) compared to a reservoir face mask, and increases gas exchange. As this modality is widely available, it might represent a supplemental approach to current treatment of CO poisoning.

We present two simultaneous cases of a married couple of 31- and 34-year-old patients, who concurrently suffered CO intoxication due to a faulty gas heater in their apartment. Both reported similar symptoms of headache and weakness, and carboxyhemoglobin (COHb)-levels at admission were 21% in both patients. One patient was treated by non-invasive CPAP-ventilation support with a FiO2 of 100%, whereas the other was treated by conventional oxygen inhalation. In the patient treated by CPAP, COHb-levels fell quickly to 6% within one hour, and reached 3% after 90 min, whereas it took six hours to reach the same levels in the patient with conventional treatment.

This vividly illustrates the potential of CPAP therapy as an alternative to conventional oxygen inhalation in the treatment of CO poisoning.

Introduction

Carbon monoxide (CO) results from incomplete combustion in cases of fire but also from motor vehicles or gas heaters [1]. It is regarded as a leading cause of poisoning. There are 40,000 to 50,000 reported cases in the US per year, but because of the nonspecific symptoms and difficult diagnosis a much higher number, up to 230,000 [2], of unreported cases is assumed [3,4]. Acute symptoms of CO poisoning are known to be very unspecific, ranging from headache, nausea, confusion, dizziness, loss of consciousness to organic injury like myocardial infarction or stroke, and finally death [5,6]. CO poisoning, however, not only leads to a number of acute symptoms but also to chronic complaints weeks or even months after the actual intoxication took place. Delayed neuropsychiatric syndrome (DNS), which may consist of a combination of headache, nausea, lethargy, confusion, emotional lability, amnesia, and even psychosis, has been described in up to 40% of victims one month after poisoning [7,8]. Treatment therefore focuses on the rapid elimination of CO and management of hypoxia.

Oxygen is the cornerstone of therapy, and usually applied via a reservoir face mask [6]. Hyperbaric oxygen therapy (HBO) eliminates CO faster, but requires extensive equipment and its benefits are discussed controversially [8]. Non-invasive continuous positive airway pressure (CPAP) ventilation using a tight mask provides an inspired fraction of oxygen of 1.0 compared to 0.6 using a reservoir face mask, and increases gas exchange. As this modality is widely available, it might represent a supplemental approach to current treatment of CO poisoning.

In December 2017, a 31-year-old male and his 34-year-old wife both woke up with headache and general weakness. When he tried to stand up he fell and hit his head, and EMS was called. When the ambulance-team arrived, their CO detectors (Dräger Pac 3500, Drägerwerk AG & Co. KGaA, Lübeck, Germany), which are carried at all times [9], and measure CO continuously, activated their alarms due to an ambient CO concentration in excess of 60 ppm. Both patients were rapidly evacuated and treated with oxygen via reservoir face mask. None of them was unconscious at any time.

At the time of arrival at the emergency department, both patients showed stable vital signs (blood pressure of 140/74 mm Hg, heart rate 70 bpm in the male patient, 117/63 mm Hg, 90 bpm in the female patient), and both still reported headache and general weakness. The male patient also showed a minor supraorbital laceration on the left side.

Initial venous blood gas analysis [10] revealed a carboxyhemoglobin (COHb)-level of 20.5% in the male, and 21.0% in the female patient. Oxygen therapy was initiated immediately in both patients, using a standard venturi reservoir face mask (oxygen flow 15 l/min) in the male, and a tight face mask connected to a respirator (Maquet Servo-i [MAQUET, Inc., Bridgewater, NJ] set at CPAP [continuous positive airway pressure] mode with FiO2 [inspired fraction of oxygen] 100% and PEEP [positive end expiratory pressure] 5 cm) in the female patient. Venous blood gas was repeated in both patients every 15 min for the first hour, and every 30 min for the remaining duration of therapy.

In the patient with CPAP-treatment, COHb-levels rapidly fell, and reached 6% after one hour, and below 3% after 90 min. In the patient with conventional treatment, elimination of CO was considerable slower, reaching 13% after one hour, below 6% after four hours, and 3% after only six hours. See Fig. 1 for details.

Standard clinical examination, ECG, routine blood test and chest X-ray showed normal results in both patients, as well as an additional skull X-ray in the male patient. Both could be discharged feeling well on the same day. In the mean time, fire department identified a faulty gas heater as source of CO.

Section snippets

Discussion

Rapid administration of oxygen to reduce the risk of neurologic sequelae is the main focus in the treatment of CO poisoning. Standard reservoir face masks are widely available, and provide a good quick first treatment, reducing COHb half-life from four to five hours in ambient air to about two hours [11,12]. Over the last decades, other methods to provide more oxygen in shorter periods of time have been investigated. Based on pathophysiological considerations, HBO therapy is able to provide

Declarations of interest

None.

References (15)

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