Closed and open breathing circuit function in healthy volunteers during exercise at Mount Everest base camp (5300 m).

We present a randomised, controlled, crossover trial of the Caudwell Xtreme Everest (CXE) closed circuit breathing system vs an open circuit and ambient air control in six healthy, hypoxic volunteers at rest and exercise at Everest Base Camp, at 5300 m. Compared with control, arterial oxygen saturations were improved at rest with both circuits. There was no difference in the magnitude of this improvement as both circuits restored median (IQR [range]) saturation from 75%, (69.5-78.9 [68-80]%) to > 99.8% (p = 0.028). During exercise, the CXE closed circuit improved median (IQR [range]) saturation from a baseline of 70.8% (63.8-74.5 [57-76]%) to 98.8% (96.5-100 [95-100]%) vs the open circuit improvement to 87.5%, (84.1-88.6 [82-89]%; p = 0.028). These data demonstrate the inverse relationship between supply and demand with open circuits and suggest that ambulatory closed circuits may offer twin advantages of supplying higher inspired oxygen concentrations and/or economy of gas use for exercising hypoxic adults.

Prolongation of the corrected QT complex--a cause of sudden cardiac death in the mountain environment?

In the mountain environment sudden cardiac death (SCD) has been shown to be responsible for the deaths of up to 52% of downhill skiers and 30% of hikers. The majority of SCD's are precipitated by a ventricular arrhythmia. Although most are likely to result from structural abnormalities associated with conditions such as ischaemic heart disease, a small but significant number may be due to abnormalities in ion channel activity, commonly known as, "channelopathies". Channelopathies have the potential to lengthen the time between ventricular depolarisation and repolarisation that can result in prolongation of the corrected QT interval (QTc) and episodes of polymorphic ventricular tachycardia (PVT) and eventually, ventricular fibrillation. This review examines the factors that prolong the QTc interval in the mountain environment and outlines a practical framework for preventing the life threatening arrhythmias that are associated with this condition.

A novel ambulatory closed circuit breathing system for use during exercise.

We describe a unique ambulatory closed circuit for delivering high fractions of inspired oxygen to an exercising user who does not require isolation from their environment. We describe the major components and their function and suggest potential applications for such a circuit. This circuit may benefit patients who are chronically dependant on oxygen, are unable to exercise due to hypoxia, or require oxygen supplementation at high altitude.

Mountain mortality: a review of deaths that occur during recreational activities in the mountains.

The growing popularity of activities such as hiking, climbing, skiing and snowboarding has ensured that the number of visitors to mountain environments continues to increase. Since such areas place enormous physical demands on individuals, it is inevitable that deaths will occur. Differences in the activities, conditions and methods of calculation make meaningful mortality rates difficult to obtain. However, it is clear that the mortality rate for some mountain activities is comparable to hang gliding, parachuting, boxing and other pastimes that are traditionally viewed as dangerous. Deaths in the mountains are most commonly due to trauma, high altitude illness, cold injury, avalanche burial and sudden cardiac death. This review describes the mortality rates of those who undertake recreational activities in the mountains and examines the aetiology that lies behind them.

Digital photography.

OBJECTIVE: The emergence of a new generation of "point-and-shoot" digital cameras offers doctors a compact, portable and user-friendly solution to the recording of highly detailed digital photographs and video images. This work highlights the use of such technology, and provides information for those who wish to record, store and display their own medical images. METHODS: Over a 3-month period, a digital camera was carried by a doctor in a busy, adult emergency department and used to record a range of clinical images that were subsequently transferred to a computer database. RESULTS: In total, 493 digital images were recorded, of which 428 were photographs and 65 were video clips. These were successfully used for teaching purposes, publications and patient records. CONCLUSIONS: This study highlights the importance of informed consent, the selection of a suitable package of digital technology and the role of basic photographic technique in developing a successful digital database in a busy clinical environment.