A telephone-based survey of current trends, habits and beliefs in patients receiving portable oxygen therapy in Madrid, Spain

Discussion

This study provides important information about individuals on portable oxygen therapy obtained from a large sample of patients on HOT in a geographical area of 4 051 862 inhabitants in the Community of Madrid. We have found a HOT prevalence of 481.16 per 100 000 inhabitants. Previous publications report great variability in the HOT prevalence among countries, even within the same country, the largest being in the USA (241 per 100 000) [8]. In 2007, data from the British Home Oxygen Database [9] showed us that HOT prevalence remained constant at about 11–12 per 100 000 inhabitants until the age of 45 years, beginning to increase from this age until reaching a peak of 880 per 100 000 inhabitants in those >80 years. More recently, an average prevalence of 264 per 100 000 inhabitants in Spain has been reported [10]. Our findings indicate that the prevalence in an urban and ageing population in the Community of Madrid is clearly higher than the Spanish average. Some authors have speculated on several possible explanations to justify this variability. It is considered that failure to identify patients who might be referenced for oxygen therapy and the lack of access to the therapy, namely the absence of financial resources, equipment and/or suppliers, could be reasons for less use of HOT in many countries. In Spain, there is great awareness of the indications for HOT among physicians, and a wide availability of suppliers to provide the home healthcare service and the equipment needed. Table 2 shows the prescribing criteria for home oxygen therapy in Spain. Additionally, the mechanisms for reimbursement are readily available for most patients who qualify for HOT so all patients have the possibility to receive HOT, if clinically justified, with full financial coverage.

We have found a clear predominance of POC prescription in the sample analysed (99.59%) in relation to liquid oxygen. POCs were introduced to the market a few years ago and they have become the portable oxygen devices preferred by doctors and patients [7]. These are more likely to be used outside the home, as they rely on batteries and electrical power supplies, but most of the currently available POCs release the oxygen in boluses or pulses, with pulsed-dose flows that have yet to demonstrate their efficacy compared to continuous flows [12]. To address this issue, Chen et al. [13] have recently compared pulse flow from a commercial POC with steady flow from a compressed oxygen cylinder. For the POC tested, pulsed doses delivered similar, though consistently lower, volume-averaged inspiratory oxygen fractions than steady flow rates equivalent to nominal pulse dose settings. Those authors hypothesised that this difference is primarily due to two factors: the increased effect of oxygen pooling for steady flow in the anatomical reservoir during slower, shallower breathing; and a delay in the arrival of the pulse, which leads to retention in the upper airways and exhalation of part of the oxygen bolus. As a rule, and according to Spanish Respiratory Society guidelines [11], the use of POCs should be restricted to patients who require low oxygen flows (<3 L·min⁻¹) and its efficacy should always be confirmed with an standardised exercise test. However, liquid oxygen could be useful for activities that take <4 h, while POCs are the choice for activities that take longer [14]. Finally, and no less importantly, the patient should have the last word about the choice of oxygen therapy prescribed and should commit to using oxygen properly [15].

An issue related to portable oxygen prescription is that only 54.93% of the patients reported having carried out a walking test with oxygen to know the amount of oxygen they needed, 27.24% of the patients had performed the evaluation with a portable concentrator and 27.69% receiving oxygen from the wall outlet of the hospital. No walking test was performed in 45.07% of patients. Desaturation is generally defined as the presence of mean oxygen saturation measured by pulse oximetry (S_pO2) ≤88% during a stress test such as the 6MWT, and adjustment of the oxygen flow during this test to average a S_pO2 ≥90% is recommended. However, this is rarely done [16]. Indeed, the recommendations of some European countries suggest using the same oxygen flow indicated at rest or 1 L·min⁻¹ more, without performing any test to assess the flow required for each patient. To check the efficacy of this therapy, the Spanish Ministry of Health and Consumer Affairs, in an order dated March 3, 1999 [17], required that the patient performed three 6MWTs (four if a practice walk was also performed) with and without oxygen (baseline, titrated and response evaluation) to demonstrate improved exercise tolerance. Recently, the Spanish guideline on continuous HOT [13] have stablished some recommendations for the correct adjustment of portable oxygen. According to these recommendations, we must demonstrate, in Spain, an average S_pO2 <88% during a 6MWT and an S_pO2 improvement (>90%) during the 6MWT on oxygen. It is necessary to perform repeated 6MWTs with different oxygen flows (even different devices) to achieve S_pO2 ≥90%, with a break of ≥30 min between each test. Alternatively, we can demonstrate an increased exercise capacity in terms of a longer distance walked. In our study, no test was performed in 45.07% of our patients, which is a very important finding considering that the patients who did perform some type of walking test prior to the prescription of portable oxygen left home significantly more often than those who had not performed the test.

Although the use of POCs is restricted to patients requiring <3 L·min⁻¹ oxygen flow rates, our results showed that almost all patients were using POCs. Does this mean that almost all patients only required low oxygen flow, or was there inappropriate use of POCs despite the guidelines? This is a very important point to be addressed. POCs have become a very popular portable oxygen therapy in our country. Physicians prescribe POCs readily without performing any kind of test to determine their effectiveness (demonstrated by 45.07% of our patients). The database from which data was derived for our study contained no data related to oxygen titration during the exercise test. We only have data about the oxygen flow prescribed by physicians and what we have seen is that in only 317 patients, the exact prescription of oxygen flow was been expressed in litres per minute (with 59 patients needing >3 L·min⁻¹). In the remaining 659 patients, the registries in our database only showed the POC settings (and a position >3 was prescribed in all patients). We do not have any data on oxygen desaturation improvement. Our interpretation is that portable oxygen prescription by physicians does not concord with guidelines. In contrast, our results have shown that patients use portable oxygen properly. So, we must work on the awareness and knowledge of health professionals regarding portable oxygen therapy prescription, and promote among them the dissemination of the guidelines in order to encouraging the increase of portable oxygen titration.

Several patients complained of the excessive weight of, difficulties in handling, noise from and embarrassment of being seen with portable oxygen devices. The duration of the battery also seemed insufficient to most patients. Similarly, Arnold et al. [18] published an interesting study of the reasons for COPD patients not using their portable systems as prescribed and the results are very similar to those reported in this study. In their study, participants reported that they did not receive written instruction on how to use portable oxygen, were uncertain of the benefits, were afraid the system would run out of oxygen while they were using it (due to lack of confidence in the cylinder gauge), were embarrassed at being seen with the system in public and were unable to carry the system because of the cylinder weight. All these issues should be addressed to improve adherence to portable oxygen prescription and enhance the benefits related to greater mobility in these patients.

Our results show that 30% of patients use portable oxygen daily despite leaving their homes five or fewer times a week. This is a curious finding given that the Spanish regulations consider performing activities outside the home to be an essential requirement for the prescription of portable oxygen. We do not know if there is a subgroup of patients in whom oxygen therapy provides benefits even if they do not leave home (e.g. those who live in large houses or houses with several floors).

The homecare provider Oximesa Nippon Gases has a training programme aiming to provide patient education on home oxygen therapy. After the prescription of oxygen to patients by the physicians, specialised nurses explain to the patients the reason they have to use oxygen; discuss all their concerns about the disease, seeking better understanding from patients and families; and explain to them what they can expect from oxygen therapy and its limits. Safety procedures are also included. Finally, trained nurses make several visits and telephone calls until the patient has understood everything. After training, patients do not have to take an examination or test to check the knowledge acquired. We can only assume that patients have carried out a training programme in portable oxygen therapy. Nonetheless, this could be one reason that would justify the good adherence found in our study, with 85% of patients leaving the home one or more times a day using oxygen.

In our study, portable oxygen was used in patients diagnosed with ILD (10%). Limited data available in the literature [19–21] suggest that many patients with ILD benefit from using oxygen: in laboratory-based tests, oxygen is associated with decreased dyspnoea or increased distance covered during a timed walk test [22, 23]. However, it has several drawbacks that threaten adherence to oxygen treatment [24]: patients are physically constrained by oxygen delivery equipment, POCs do not generate high enough flows for many patients, air travel is impossible for patients who are unable to use POCs and patients feel stigmatised when seen wearing their oxygen cannula in public [25]. Ramadurai et al. [26] have recently published a prospective study of 30 clinically stable ILD patients that performed two 6MWTs, one of them wearing a backpack and in the other, no backpack was worn. What the authors found in their study is that among ILD patients, carrying portable oxygen versus receiving oxygen via a stationary concentrator results in significantly greater dyspnoea and shorter distances covered in timed testing. Patients with the greatest impairment may be affected most. Considering these facts, the physician should alert patients to this effect when prescribed oxygen, and should help patients to decide on the best oxygen delivery mode to meet their personal and clinical needs.

The most important limitation of this study is that the results we reported by patients in a subjective manner and there are already studies in the literature that have shown that the patient tends to overestimate adherence compared with objective measurement monitoring in the device. The lack of information on data related to oxygen titration during the exercise test is also an important limitation.

In summary, the data obtained in our study from a large sample of patients show us that they know why they are receiving HOT and have a relatively good adherence to treatment. Portable concentrators are mainly prescribed to patients, probably due to their simplicity and greater autonomy to depend on batteries and power supply. A significant number of patients reported that they had not performed a walking test before oxygen prescription or performed any kind of oxygen titration with exercise. Our interpretation is that the portable oxygen prescriptions by physicians are not concordant with the existing guidelines. The prescription protocol and the role of the homecare provider training programme are probably two essentials factors in the results we have found. Our study has generated several hypotheses regarding long-term oxygen therapy. For example, if the patients perform a 6MWT with oxygen prior to portable oxygen therapy prescription, they are significantly more active than those who are not given a walking test. It is also an interesting finding that individuals with portable oxygen who leave home infrequently will be significantly more active at home compared to those who do not have portable oxygen. Consequently, this study may help to promote the design of future analytical studies. Additionally, more studies are needed to analyse the impact of portable oxygen therapy in COPD patients with chronic respiratory failure.