home_oxygen

home oxygen

continuous oxygen (ideally > 19hrs/day):
- is indicated to improve longevity & quality of life if either:
  - stable daytime PaO2 is < 55 mmHg at rest
  - stable daytime PaO2 is 55-59 mmHg and there is evidence of hypoxic organ damage (incl. RVF, pulm. HT or polycythaemia)
- flow rate should be set to maintain PaO2 > 60mmHg (SaO2 > 90%) during waking rest. This will usually need to be increased by 1L/min during sleep, exertion or air travel.
intermittent oxygen therapy:
- is indicated for:
  - nocturnally to relieve demonstrated sleep desaturation to an SaO2 < 88% (PaO2 <55mmHg)
    - oxygen concentrator may be most economic method for this
  - a small cylinder of oxygen for emergency use by pt with severe asthma who is prone to sudden life-threatening episodes
  - for relief of symptoms in terminally ill pts who will usually have a life expectancy of < 3months
    - oxygen use may become continuous as symptoms progress
  - provision to extend exercise capacity but this has not been shown to prolong life except in pts awaiting lung transplants, etc where physical fitness levels in a rehab. program may be beneficial, thus this indication has the lowest priority when considering demands for home oxygen provision.

lung dysfunction where main complaint is SOB, but who maintain PaO2>60mmHg & show no secondary effects of chronic hypoxia
smokers who continue to smoke - fire risk
pts who have not received adequate medical Rx
inadequate motivation to undertake the discipline required in oxygen Rx

serious hypercapnia may occasionally develop esp. if:
- acute exacerbations of disease
- sedatives, alcohol, narcotics
fire risk if smokers

molecular filter removes nitrogen allowing 90-95% oxygen at outlet but only at 2L/min usually
cheap, safe, convenient, not portable, needs electricity, noisy & vibrates, risk of mechanical failure
can be wheeled but weigh 21-26kg
cannot be used for nebulisation as pressure too low (35-63kPa cf 140kPa for neb. pumps)
cheaper than compressed if use is equivalent to 3 E size cylinders/mth but depends on electricity supply costs
if use for > 2 years, cheaper to buy than rent, although rental cost not affected by amount of usage & includes maintenance costs (~$180/yr 1997)
requires regular maintenance - changing & cleaning of filters, checking alarm systems

conserve space by storing at -183deg.C (30L then equiv. to 25800L of gaseous oxygen)
2 tanks needed - a large storage tank of 30L (equiv. to 7 E size compressed cylinders) & a portable unit filled from the larger tank for portable use
oxygen delivered through coils, where it vaporises
light weight, high capacity, reliable, simple maintenance, high cost, small risk of frost bite