Gaseous Exchange: Hyper- and Hypo-Baric Pressures Flashcards
Regarding breathing at high pressure (true or false):
Increasing pressure leads to increased work of breathing
True. Increasing pressure increases the density of gases. Air at 4 atm is four times as dense as at atmospheric pressure. This leads to increased ventilatory resistance and increased work of breathing.
Regarding breathing at high pressure (true or false):
Divers breathing air can suffer from nitrogen narcosis
True. Nitrogen narcosis starts to occur at about 4 atm (30 m). Divers breathe a mixture of helium and oxygen because of its reduced density and to avoid nitrogen narcosis.
Regarding breathing at high pressure (true or false):
Inspired oxygen concentration needs to vary with depth
True. In theory, lower concentrations of oxygen are needed, as PIO2 is maintained by high pressure. A concentration of 2.5% oxygen is required at 20 atm pressure to maintain a PIO2 of 50 kPa.
Regarding breathing at high pressure (true or false):
Divers can breathe 100% oxygen
False. Breathing 100% oxygen produces oxygen toxicity, convulsions, chest pain and irreversible acute lung injury.
Regarding physiological effects of altitude: (true or false)
Inspired PO2 at the summit of Everest is about half the sea level value
False. PIO2 at the summit of Everest is about a quarter of the sea level value. It is about half the sea level value at Everest base camp.
Regarding physiological effects of altitude: (true or false)
Mental impairment occurs over 15 000 ft
False. Mental impairment occurs over 20 000 ft.
Regarding physiological effects of altitude: (true or false)
Inspired PO2 would be zero at 63 000 ft
True. Also, body water would boil at this altitude.
Regarding physiological effects of altitude: (true or false)
Acclimatization to high altitude takes a few hours for most humans
False. Acclimatization occurs over days to weeks.
Regarding physiological effects of altitude: (true or false)
Respiration returns to normal within an hour of ascending to high altitude
False. The ascent causes initial hypoxia, but the hypoxic drive is short-lived.
Likely symptoms of rapid decompression include the following (true or false):
Neurological damage
True. This damage may be permanent.
Likely symptoms of rapid decompression include the following (true or false):
Arterial air embolus
True. This may rupture lung tissue, which can lead to gas bubbles being released into the arterial circulation.
Likely symptoms of rapid decompression include the following (true or false):
Barotrauma in air-filled spaces
True. Any air-filled spaces, such as the lungs or ear, can suffer barotrauma.
Likely symptoms of rapid decompression include the following (true or false):
Bubbles in cartilage
True. Bubbles can form in vessel poor tissues with avascular narcosis.
Likely symptoms of rapid decompression include the following (true or false):
Raised intraocular pressure
False. Possible, but unlikely unless there were gas bubbles in the eye, which is effectively a fluid-filled space.
Regarding relevance to anaesthesia (true or false):
Divers may become anaesthetized by nitrogen
True. This can occur when divers breath air below 30 m.
Regarding relevance to anaesthesia (true or false):
Patients with hypoxia at sea level may be more vulnerable to desaturation at altitude
True. These patients may require additional oxygen.
Regarding relevance to anaesthesia (true or false):
The boiling point of volatile anaesthetic agents reduces at altitude
True. The boiling point of all the volatiles fall, but in practice unaltered vapourizers have been used safely at altitude for many years. The commonest issue being inappropriately light anaesthesia because of inadequate vapourization of volatiles due to low temperature, which accompanies the altitude.
Regarding relevance to anaesthesia (true or false):
Hyperbaric oxygen may be administered to a patient suffering from carbon monoxide poisoning
True. The treatment of carbon monoxide poisoning and burns may involve hyperbaric oxygen.
Regarding relevance to anaesthesia (true or false):
Nitrous oxide can be used for divers who have returned to the surface
False. This might increase the volume of air bubbles in the tissues.
Physiological adaptations to altitude include (true or false):
A shift of the HB dissociation curve to the right
False. The effect is to promote loading of oxygen in the lungs at low PO2. Therefore a leftward shift.
Physiological adaptations to altitude include (true or false):
Chronic acidosis
False. Respiratory alkalosis is a response to altitude.
Physiological adaptations to altitude include (true or false):
Methaemoglobinaemia
False.
Physiological adaptations to altitude include (true or false):
Fetal haemoglobinaemia
False.
Physiological adaptations to altitude include (true or false):
Increased red cell mass
True. This is typically a rise of Hb of a gram or so per decilitre.
