Oxygen therapy in interstitial lung disease

A very important discussion to have with patients who suffer from various forms of interstitial lung diseases is around supplementary oxygen.

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Main points to consider:

1. We should request an ambulatory oxygen assessment in all patients with a DLCO value of less than 50% predicted

A low DLCO value is a great indicator that your patient has an oxygen requirement. Normally when the value is below 50% predicted, extra ambulatory O2 may be required (i.e. extra O2 on exertion). This would only be delivered on an as-needed basis, when the patient knows they will perform a more intense physical task (such as walking long distances, lifting heavy weights, physical work etc.). Depending on how advanced the ILD may be, this may be required more or less often.

The ambulatory O2 assessment involves performing a walking test or equivalent to determine if blood oxygen levels decrease on exertion. The thresholds for prescribing ambulatory oxygen will vary from country to country, but normally an SpO2 level which drops to below 88-89% on exertion and which is corrected by supplying a set flow of O2 (i.e. 2L/min) is required. In most cases, arterial or capillary blood gas measurements are required. Please check your own local/country’s criteria and guidelines for the correct levels required for prescription.

As a note, I am perfectly aware that in some countries ambulatory oxygen may not be readily available. There may simply be no availability at all, regulations against carrying portable oxygen cylinders, no ambulatory devices available, no reimbursement for ambulatory oxygen etc. These are very significant problems and perhaps more awareness of the need for supplementary O2 is required. Some patients may be willing to purchase their own portable oxygen concentrators and this patient preference should be discussed.

2. O2 therapy should only be prescribed to patients who have a formal assessment

I personally would advise against providing supplementary oxygen unless a formal assessment including arterial/capillary blood gas measurements has been performed. Oxygen is a form of treatment and has indications and contraindications. There are risks associated with supplementary O2, not limited to fire hazards in inappropriate settings and risk of worsening hypercapnia if blood pCO2 levels are not assessed before prescription.

Long term O2 therapy should therefore be prescribed, including all the necessary details surrounding flow rate, circumstances of use and mode of delivery (i.e. nasal cannula/mask type etc.)

I would encourage you to refer to available guidelines on the topic, such as the BTS guidelines for Home Oxygen, or your local equivalent guideline.

3. Emphasize the fact that supplementary oxygen therapy is a form of treatment

One of the best ways I personally found to communicate the need for extra O2 to my patients is to describe it as a form of treatment for ILD. Most patients are aware that ILD does not have many effective treatment options. In conditions such as idiopathic pulmonary fibrosis (IPF) we are in a situation where we are simply delaying inevitable progression.

In these circumstances, most patients would be willing to try anything to obtain some extra benefit from current treatments available. Most will ask if there is anything else they can do in addition to taking their pharmacological treatments.

This is a great opportunity to discuss O2 therapy. If there is a clear indication (see above) for long term oxygen, this should be approached as a form of treatment.

It’s very important to not present O2 therapy a treatment for breathlessness (it is not!). Supplementary oxygen will correct low blood O2 levels and will ensure optimal functioning of the body’s systems. Supplementary O2 may delay or reduce pulmonary hypertension, allowing the cardiovascular system to work optimally. Even though in these cases there may be some symptomatic benefit, it is extremely important to emphasize that the extra O2 is there to correct an imbalance in the body, just as certain medications optimize certain metabolic or cellular pathways. This will prevent long term deterioration by compounding comorbidities related to anaerobic functioning of the various organ systems.

Resolving the issue of breathlessness should not be limited to oxygen use. The flow rates required to correct pO2 levels with oxygen delivery devices are nowhere near enough the flow rates required to counteract breathlessness. Patients who are breathless require very high air flow rates directed towards their face and airways. These can sometimes be achieved by employing simpler methods such as fan therapy or simply advising patients to face an open window while using their supplementary oxygen.

4. Have empathy regarding the psychological barriers to O2 use

Even if O2 is regarded as a form of treatment and is important, many patients will feel as if going on long term or ambulatory oxygen is a terminal event. Psychologically it is extremely difficult for someone to accept that they now require various devices, tubes, cannulas and masks to help them breathe.

Those who provide care for ILD patients (not limited to doctors and nurses) should have unlimited empathy for how difficult this situation is. It is a terrible thing to not be able to catch your breath.

One of the most difficult situations is when symptoms are still not very significant, but the blood pO2 levels are still low. These are the circumstances in which supplementary O2 is actually most effective as a form of treatment, because it has the highest likelihood of providing long term benefits (before other comorbidities set in). As discussed above, this is the moment when O2 therapy should be presented as a form of treatment, not as a form of breathlessness relief. The long-term benefits should be clearly defined during patient consultations and the least “invasive” forms of oxygen delivery should be offered. Patients should have input into what delivery device is given to them (portable concentrators, small cylinders, larger concentrators with longer tubing, smaller cannulas etc.). They should be encouraged that if oxygen is indeed indicated based on blood pO2 levels, using these devices would be beneficial despite the lifestyle burden.

Don’t forget to be empathetic to the fact that going on supplementary oxygen is a big admission that a severe condition is present, and that person’s lifestyle will forever be changed.

Covering the above topics in ILD consultations is so important! I personally feel that oxygen therapy is significantly underused, even though it is one of the interventions that has been actually proven to improve survival in a host of chronic respiratory diseases!