Challenges to Normal Respiration

True or false: O2 resting consumption is not the same as base line O2 consumption

True

What is our average O2 resting consumption?

200mL/ min

What is VO2 max?

An individual's maximum rate of oxygen consumption

Give 4 factors that alter O2 oxygen consumption:

1) psychological factors

2) neural input

3) movement receptors like proprioceptors

4) small changes in blood gases e.g becoming more acidotic

How does PO2 change with altitude?

it decreases

What is our normal atmospheric pressure at sea level?

101.3 kPa

How does O2% change with altitude?

it remains constant at 21%

What is the water vapour pressure of H2O?

6.3 kPa

What is the standard PCO2 in alveoli?

5.3kPa

Give the alveolar PO2 equation:

[FiO2 x PATM-PH2O)] - (PACO2/R)

What is the average alveolar PO2 at sea level?

12.3 kPa

What is oxygen saturation on commercial airlines?

90%

What is PO2 on commercial airlines?

17 kPa

What is PO2 at 60,000 ft altitude and what effect would this have on the body?

6.3 kPa blood and eyes will boil and lungs will fill with steam

How does hyperventilation help respond to increasing altitude?

if you double your minute volume, you half arterial and alveolar PO2 leaving more space for O2

How does increasing 2,3 DPG levels help respond to increasing altitude?

it promotes the release of O2 from haemoglobin

What is the % O2 saturation in venous blood?

75%

How does polycythaemia help respond to altitude?

increasing Hb and RBCs increases oxygen carrying ability of blood

Where is bicarbonate excreted from to improve acid base balance?

kidneys and cerebrospinal fluid

Give 7 symptoms of hypoxia:

1) nausea

2) confusion

3) headache

4) blurred vision

5) raised intracranial pressure

6) pulmonary hypertension

7) pulmonary oedema

Give 6 symptoms of acute mountain sickness:

1) nausea

2) amnesia

3) breathlessness

4) headache

5) loss of appetite

6) difficulty sleeping

Give 2 symptoms of severe mountain sickness:

1) Cheyne Stokes respiration

2) pulmonary and cerebral oedemas

What is Cheyne-Stokes breathing?

periods of deep breathing that alternate with periods of apnoea

Fill in the gap: for every __m under water, pressure increases by 1 atm

10m

What is the pressure found 30m underwater?

4 atm

Give Boyle's Law:

At 50m underwater, lung volume is compressed to 1L

How does the chest change on descent under water and what is the effect of this?

it is compressed by increasing pressure allowing PO2 to be maintained or even rise

How does the chest change on ascent under water and what is the effect of this?

it expands due to decreasing pressure causing PO2 to fall and divers may become hypoxic

Why can't you snorkel below 1.6m?

the pressure under 1.6m of water is 2.6 atm and the intercostal muscles are too weak to overcome the pressure gradient

What type of air is used to remove nitrogen during deep diving?

helium oxygen

What is the PAO2 of helium oxygen air at 90m under water?

20 kPa

Why is it dangerous to inspire too much oxygen when deep diving?

nitrogen is very soluble in tissues and has high densities at high pressures, increasing the work of breathing

At what depth does nitrogen narcosis take place?

40m

How can high nitrogen levels in tissue be overcome?

put patient in decompression chamber to return nitrogen to solution and remove bubbles

Give features of the dive reflex:

vessels vasoconstrict so O2 is conserved to the heart, lung and brains upon being submerged while the vagus nerve stimulates bradycardia so O2 consumption decreases

Why does hyperoxia cause oxygen toxicity?

high O2 concentrations generate oxygen free radicals that damage tissues

What is causes retinal fibroplasia?

high PO2 from ventilators puts pressure on retinal fibres causing blindness

Why are infants acclimatised to lower PO2 when born?

maternal circulation to the foetus has lower PO2 as it has already circulated the mother's tissues

What two conditions does oxygen toxicity cause in adults:

1) pulmonary fibrosis

2) ARDS