Malaysian Family Physicians - home oxygen therapy

REVIEW ARTICLE

THE ROLE OF GENERAL PRACTITIONERS IN HOME OXYGEN THERAPY

GPs, in close proximity to patients in the community are in the best position to advise and supervise on the delivery of home oxygen therapy once prescription is given by the respiratory physician. Various stationary and ambulant sources of oxygen and different modes of oxygen delivery are tabulated in Table 3. Selection of the appropriate source and mode of delivery depends on the objective of therapy whether for symptom relief or survival improvement, total daily requirement, flow rate of oxygen, indoor and out-door activities of patients and their personal preference. Patients and carers must be educated on the precautions to be observed while maintaining home oxygen therapy (Table 3, Box 2, Box 3).¹⁵

Table 3. Oxygen delivery system¹³

Oxygen Supply
Sources	Features
A. Stationary
1. Oxygen concentrators	Electrically powered Uses molecular sieve beds to filter and concentrate oxygen molecules from ambient air, generating oxygen concentrations of 90% to 98% Maximum flow of 3-5 L/min Backup oxygen supply with a cylinder is necessary
2. Compressed gas cylinders H-sized	Large and heavy (about 150lbs) Provides oxygen for about 57 hours at flow of 2 L/min Up to 15 L/min can be attained
E-sized	Readily available and inexpensive for patients who require 2 L/min or less Weighs 13-17 lbs, requires a cart to move Lasts about 5½ hours at 2 L/min
3. Liquid oxygen reservoirs	Can be used to refill portable units Last 5-7 days at 2 L/min Relatively high cost / occasional “freezing” of the valve at flow of about 8 L/min / evaporation of the liquid oxygen when not in use.
B. Ambulant	Ambulatory oxygen sources are small and light weight and a necessity for active patients who leave their homes.
Aluminium B tank	Last only 1 hour at 2 L/min
Aluminium D tanks	Last 3½ hours at 2 L/min
Portable liquid oxygen tank	Weigh 6-10 lbs Last 6-10 hours at 2 L/min Can be refilled from stationary liquid oxygen reservoir

Oxygen Delivery Devices
Devices	Features
1. Nasal cannulas	Simple and inexpensive but inefficient delivery method Maximum delivered at 6 L/min
2. Demand flow devices	Senses the start of ventilation and delivers a pulse of oxygen during inspiration when it is more likely to be useful in gas exchange Eliminates oxygen flow during expiration that would otherwise be wasted Oxygen savings of 50-85% Different models differ in duration, frequency and pulse volume Noise produced is a disadvantage
3. Reservoir cannulas	Traps initial portion of expired gas that comes from the conducting airways and contains almost pure oxygen Two types available: Oxygen conserving nasal cannula with a reservoir situated below the nose and an oxygen-conserving pendant with a reservoir situated on the patient’s chest. Reduce oxygen use by 50-75% Patients may find their appearance objectionable
4. Transtracheal oxygen catheters	Devices deliver oxygen directly through a catheter inserted into the cervical trachea Improves patient adherence to therapy Continuous oxygen use for 24 hours a day is attainable Successful in patients who have refractory hypoxaemia to oxygen delivered by nasal cannula

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