Question: Background: If you dive on SCUBA (self-contained underwater breathing apparatus; i.e. air tank an…

Background: If you dive on SCUBA (self-contained underwater
breathing apparatus; i.e. air tank and regulator) to relatively
deep depths (usually >30m) and relatively long times (usually
> 30 minutes), you need to “decompress”, i.e. remove excess N2
that has dissolved in tissue because of the high pressure in the
lungs during diving. Total gas pressure in the lung must equal the
water pressure outside the body; water pressure increases by one
atmosphere for every 10 m of depth (plus the air pressure at the
surface). High O2 gas mixtures are often used for decompression –
not for the high O2, which is toxic if breathed over several hours
or more, but because of the low N2 in the mixture, which speeds up
removal of N2. Problem: During the final decompression step, you
breath 80% O2 at 5 m depth, and just hang in the water resting
until it is safe to ascend to the surface

. i) What are inspired PO2, PN2, and PCO2 in mmHg while
decompressing at 5 m?

ii) What is your ventilation rate while decompressing relative
to resting at the surface breathing air?

iii) What is your alveolar (lung) PO2 while decompressing?

iv) What is arterial O2 content relative to the arterial O2
content resting at the surface breathing air?