SAFA Skysailor Magazine

26 SKY SAILOR September | October 2019 U nfortunately, a pilot died while attempting to launch, and Antoine Girard was prompted to write on Facebook about the lack of preparedness of some pilots to fly at these altitudes. The events of that day prompted authorities in Chamonix and Saint-Gervais to ban top-landing within 600m of the summit [xcmag.com/news/ top-landing-mont-blanc-banned-after-record-day]. One factor that needs to be considered when flying at altitude is the condition of hypoxia. CASA defines hypoxia as, “A medical condition where the human body is deprived of an adequate supply of oxygen, leading to symptoms of light- headedness, fatigue, difficulty processing visual information, impaired reasoning and judgement, hyperventilation, muscular weakness and eventu- ally loss of consciousness and death of brain cells.” (CASA CAAP 20.4-01 v1.0, January 2018). Currently, according to our Operations Manual, we are not permitted tofly above a ceilingof 10000ft amsl unless we have an Oxygen Endorsement and are carrying a certified oxygen system (amongst other requirements). However, this is not to say that all pilots will experience hypoxia onset at that altitude; as with other physiological condi- tions, hypoxia onset is subject to many variables within each individual. Hypoxia is usually classified into four types: ➲ ➲ Hypoxic – results when there is a reduction of a partial pressure of oxygen in the breathed air, or due to some physiological reasons. ➲ ➲ Anaemic – caused by reduced haemoglobin content. It’s commonly attributed to poor nutri- tional state, but carbon monoxide, nitrates and sulfa drugs can also hog haemoglobin, reducing the oxygen carrying capacity of your blood. ➲ ➲ Stagnant or Hypokinetic – this form is due to a malfunction in the circulatory system; the blood is good, but it can’t be circulated adequately. ➲ ➲ Histotoxic – occurs when the supply of oxygen is normal, but the utilisation by the bodies cells is interfered with by substances such as alcohol, narcotics, or poisons such as cyanide. While all types may occur while we’re flying, the one we are primarily interested in is Hypoxic Hypoxia, which occurs when breathing air at reduced pressure. The reduced air pressure at altitude results in a lowered oxygen partial pres- sure compared to sea level, and not having a sup- plemental oxygen supply can lead to hypoxia. While hypoxia is generally regarded to occur at altitudes above 10000ft, there are factors at the individual level that can lead to onset at lower altitudes: ➲ ➲ Pilots vary physiologically, and therefore it is difficult to quantify onset at the individual level. ➲ ➲ Physical activity at altitude means an increased requirement for oxygen and can lead to more severe symptoms. ➲ ➲ A pilot’s level of fitness has an effect – fitter people are more tolerant of hypoxia. ➲ ➲ Diseases affecting the heart, lungs or blood will affect the ability to oxygenate and transport blood. ➲ ➲ A person’s emotional state, whether anxious or apprehensive, can make them more susceptible. ➲ ➲ The rate of ascent and duration at altitude will contribute to the speed of onset and severity of the symptoms. It is important to note that the effects of hypoxia are cumulative – the longer you are there, the more severe the symptoms that will develop. Acclimatising yourself to higher altitudes will contribute to tolerance. Probably the biggest contributing factor though is smoking. Smokers incur a 5000ft penalty straight away: If you’re flying at 8000ft, the effect is equivalent to being at 13000ft. The onset of hypoxia is insidious; people suffering do not realise they are affected. So how do we recognise it? The symptoms in increasing significance include: ➲ ➲ Breathlessness, ➲ ➲ Excessive yawning, ➲ ➲ Tiredness and fatigue, ➲ ➲ Euphoria, ➲ ➲ Impairment of performing learned and mental tasks, ➲ ➲ Change in sense perception and, eventually, ➲ ➲ Unconsciousness. To get an idea of the sorts of behaviours hypoxia induces, have a look at these videos: [youtube.com/watch?v=n_MI9UiYwJA ] [youtube.com/watch?v=kUfF2MTnqAw ] [youtube.com/watch?v=XnOAnVTyC-E] How can we measure oxygen saturation in the blood? In hospitals, you will see staff slipping a device attached via a cable to a monitoring and read-out device, onto the fingers of patients. This device emits infrared and glow from two light sources of different wavelengths on the upper side, through the fingernail. These are received on the lower side of the of the device. From the signals received, the characteristics of the Reductive Haemoglobin and Oxyhaemoglobin are determined, using the Lambert Beer Law (nothing to do with beer). The monitor provides an oxygen saturation value as a percentage. What devices are available to buy to do the same thing? There is actually a heap of them out there and they are pretty cheap. They also come in a couple of distinct shapes and modes of operation. I’ve purchased three of them and given them a go. First up, what is there that operates as per the hospital model? The go-to item seems to be the Contec CMS-50D. There are several versions of this unit which will have either no download capability or download to software via USB cable or Bluetooth. I went basic with this one: Figure 1: Contec CMS-50D It’s really easy to use, just slip it on your finger, press the white button and wait 5 to 10 seconds. Keep pressing the white button to change how the data is displayed. The display is clear and easy to read. To turn off, just remove your finger. It’s powered by two AAA batteries. The downside is that for our purposes, it is not feasible to use in the air. Taking a glove off and operating this device in flight is impractical and potentially unsafe. Finger- less gloves will improve things, but only slightly. Hypoxia On 26 June this year, while the X-Alps 2019 edition was running, we saw a day of exceptional flying conditions allow a bevy of paraglider pilots top-land on the 4810m summit of Mont Blanc. 1 An estimated number of over 200 pilots were present. by Iain Clarke – SAFA Safety Management Officer