Wataru Kähler

Efficacy of ventilation and ventilation adjuncts during in-water-resuscitation—A randomized cross-over trial ☆

INTRODUCTION Drowning is a common cause of death in young adults. The 2010 guidelines of the European Resuscitation Council call for in-water-resuscitation (IWR). There has been controversy about IWR amongst emergency and diving physicians for decades. The aim of the present study was assessing the efficacy of IWR. METHODS In this randomized cross-over trial, nineteen lifeguards performed a rescue manoeuvre over a 100 m distance in open water. All subjects performed the procedure four times in random order: with no ventilation (NV) and transportation only, mouth-to-mouth ventilation (MMV), bag-mask-ventilation (BMV) and laryngeal tube ventilation (LTV). Tidal volumes, ventilation rate and minute-volumes were recorded using a modified Laerdal Resusci Anne manikin. Furthermore, water aspiration and number of submersions of the test mannequin were assessed, as well as the physical effort of the lifeguard rescuers.One lifeguard subject did not complete MMV due to exhaustion and was excluded from analysis. RESULTS NV was the fastest rescue manoeuvre (advantage ∼40s). MMV and LTV were evaluated as efficient and relatively easy to perform by the lifeguards. While MMV (mean 199 ml) and BMV (mean 481 ml) were associated with a large amount of aspirated water, aspiration was significantly lower in LTV (mean 118 ml). The efficacy of ventilation was consistently good in LTV (Vt=447 ml), continuously poor in BMV (Vt=197) and declined substantially during MMV (Vt=1,019 ml initially and Vt=786 ml at the end). The physical effort of the lifeguards was remarkably higher when performing IWR: 3.7 in NV, 6.7 in MMV, 6.4 in BMV and 4.8 in LTV as measured on the 0-10 visual analogue scale. CONCLUSION IWR in open water is time consuming and physically demanding. The IWR training of lifeguards should put more emphasis on a reduction of aspiration. The use of ventilation adjuncts like the laryngeal tube might ease IWR, reduce aspiration of water and increase the efficacy of ventilation during IWR.

Monitoring of CBFV and time characteristics of oxygen-induced acute CNS toxicity in humans

Background:  Hyperbaric oxygen can cause central nervous system (CNS) toxicity with seizures. We tested the hypothesis that CNS toxicity could be predictable by cerebral blood flow velocity (CBFV) monitoring.

Decompression illness with hypovolemic shock and neurological failure symptoms after two risky dives: a case report

Hypovolemia is known to be a predisposing factor of decompression illness (DCI) while diving. The typical clinically impressive neurological symptoms of DCI may distract from other symptoms such as an incipient hypovolemic shock. We report the case of a 61‐year‐old male Caucasian, who presented with an increasing central and peripheral neural failure syndrome and massive hypovolemia after two risky dives. Computed tomography (CT) scans of the chest and Magnetic resonance imaging scans of the head revealed multiple cerebral and pulmonary thromboembolisms. Transesophageal echocardiography showed a patent foramen ovale (PFO). Furthermore, the patient displayed hypotension as well as prerenal acute kidney injury with elevated levels of creatinine and reduced renal clearance, indicating a hypovolemic shock. Early hyperbaric oxygen (HBO) therapy reduced the neurological deficits. After volume expansion of 11 liters of electrolyte solution (1000 mL/h) the cardiopulmonary and renal function normalized. Hypovolemia increases the risk of DCI during diving and that of hypovolemic shock. Early HBO therapy and fluid replacement is crucial for a favorable outcome.

Benzoate hydroxylation: a measure of oxidative stress in divers.

Hyperoxia may facilitate the formation of reactive oxygen species. Recent experiments indicated signs of oxidative stress after 3.5 h hyperoxic diving. We analyzed in the urine of healthy, 100% O2-breathing male volunteers before and after 45 min seawater diving (170 kPa) or 30 min resting at 280 kPa in a pressure chamber (HBO) for sub-fractions of hydroxybenzoate (HB), monohydroxybenzoate (MHB), and of dihydroxybenzoate (DHB). Measurements were performed by HPLC and electrochemical or UV-detection. Additionally, urinary concentrations of thiobarbituric acid-reactive substances (TBARS) and of creatinine (CREA) were analyzed by standard colorimetric assays. During HBO treatment, TBARS, DHB, 2,4-DHB, and 3,4-DHB increased significantly. MHB and CREA did not change. 2,4- and 3,4-DHB-alterations correlated with changes in TBARS. Diving induced urine dilution and stimulated oxygen consumption. Urinary TBARS and HB rose significantly higher during diving at 170 kPa than during HBO at 280 kPa. A different pattern in urinary sub-fractions of DHB could be observed in divers: 2,6 > 2,3 > 2,5 > 3,4. Changes in 2,6- and 2,5-DHB correlated significantly with alterations in TBARS. 2,6-DHB probably indicated renal oxidant stress similar to previously described animal experiments. It is concluded that analyzing urinary HB may provide a sensitive measure to quantify and qualify oxidant stress in divers.

Mechanical ventilation and resuscitation under water: Exploring one of the last undiscovered environments – A pilot study

INTRODUCTION Airway management, mechanical ventilation and resuscitation can be performed almost everywhere--even in space--but not under water. The present study assessed the technical feasibility of resuscitation under water in a manikin model. METHODS Tracheal intubation was assessed in a hyperbaric chamber filled with water at 20 m of depth using the Pentax AWS S100 video laryngoscope, the Fastrach™ intubating laryngeal mask and the Clarus optical stylet with guidance by a laryngeal mask airway (LMA) and without guidance. A closed suction system was used to remove water from the airways. A test lung was ventilated to a maximum depth of 50 m with a modified Oxylator(®) EMX resuscitator with its expiratory port connected either to a demand valve or a diving regulator. Automated chest compressions were performed to a maximum depth of 50 m using the air-driven LUCAS™ 1. RESULTS The mean cumulative time span for airway management until the activation of the ventilator was 36 s for the Fastrach™, 57 s for the Pentax AWS S100, 53s for the LMA-guided stylet and 43 s for the stylet without LMA guidance. Complete suctioning of the water from the airways was not possible with the suction system used. The Oxylator(®) connected to the demand valve ventilated at 50 m depth with a mean ventilation rate of 6.5 min(-1) vs. 14.7 min(-1) and minute volume of 4.5 l min(-1) vs. 7.6 l min(-1) compared to the surface. The rate of chest compression at 50 m was 228 min(-1) vs. 106 min(-1) compared to surface. The depth of compressions decreased with increasing depth. CONCLUSION Airway management under water appears to be feasible in this manikin model. The suction system requires further modification. Mechanical ventilation at depth is possible but modifications of the Oxylator(®) are required to stabilize ventilation rate and administered minute volumes. The LUCAS™ 1 cannot be recommended at major depth.