Arterialised earlobe capillary blood gases in the COPD population Jane Young
Abstract
Arterialised ear lobe capillary blood (ELCB) gas sampling is a widely used clinical procedure undertaken across both primary and secondary care settings. The prevalence of this sampling method has grown among health professionals, coupled with a growing demand for domiciliary oxygen therapy in the UK, in particular for those who have chronic obstructive pulmonary disease (COPD). Research studies supporting arterialised ELCB gas sampling show inconsistencies in technique, and a survey of respiratory nurses’ current practice demonstrated wider inconsistencies. In the absence of national clinical guidelines to direct this practice, and an acknowledged and accepted under-calculation of partial pressure of oxygen, this article investigates the sampling method used to obtain arterialised ELCB gas sampling and consequently questions its reliability in practice. Key words: Arterialised earlobe capillary blood gas ■ Chronic obstructive pulmonary disease ■ COPD ■ Oxygen
Jane Young, Community Nurse Lecturer, Anglia Ruskin University, Cambridge Accepted for publication: June 2014
838
Background: ELCB gas sampling to fellow respiratory colleagues at an annual national conference. These findings will be presented and discussed, leading to a review of practice capillary blood gas protocols. Following this data collection and analysis, discussion of findings and implications for the future will be discussed.
Context: respiratory disease The burden of respiratory disease and in particular chronic obstructive pulmonary disease (COPD) is clear: it accounts for around 23 000 deaths in England (Department of Health (DH), 2011) and a financial cost amounting to £492 million per year (Britton, 2003). Improving survival in COPD can be achieved through the administration of long-term oxygen therapy which corrects hypoxaemia (Nocturnal Oxygen Therapy Trial Group, 1980; Medical Research Council Working Party, 1981). Consequently, recent years have seen an increase in oxygen provision. Figures indicate that an estimated 85 000 patients have oxygen at home at a cost of £110 million per year (National Health Service Primary Care Commissioning (NHSPCC, 2011). IMPRESS (2011) proposes that 60% of this group have COPD, but that 30% of patients receive oxygen without proven clinical benefit in contrast to approximately 20% of severe COPD patients, who would benefit from long-term oxygen therapy but do not receive it.
The physiology of ELCB gas sampling, which is deemed a suitable substitute for blood gas analysis, has been described by Higgins (2008). Capillaries are the connectors between arterioles and venules, and thereby connect the arterial and venous networks. The blood obtained by skin puncture is not purely capillary: it is a mixture of capillary, arteriole and venule. Physiologically, the arterial blood network commands a higher pressure than the venous network, which is the rationale for regarding a capillary sample as similar to an arterial one. Furthermore, the correlation of capillary and arterial blood is greater when the PaO2 is lower as a result of less arteriole/venous difference. Hughes (1996) and Higgins (2008) state that increasing the blood flow through the capillary bed achieves arterialisation of capillary blood and subsequently has the biggest effect in reducing arteriovenous (AV) differences— this provides the physiological rationale for vasodilating the puncture site. However, Higgins (2008), Hughes (2009) and Richter et al (2014) all acknowledge that there is a lack of formalised research into the effectiveness of ‘arterialising’ ear lobes for capillary blood gas sampling and support further investigation. The sampling techniques used in 15 published adult ELCB gas trials are presented in Table 1. The majority of the trials included in this table were specific to patients who had an underlying
© 2014 MA Healthcare Ltd
B
lood gas analysis has historically been achieved by means of arterial puncture (Eaton et al, 2001). Yet recent years have seen a change in blood gas sampling methods and the use of capillaries (Pitkin et al, 1994) for collecting samples is now regarded as questionable (Fajec et al, 1998; Sauty et al, 1996; Eaton et al, 2001; Stott et al, 2008; Honarmand and Safavi, 2008). This exploratory investigation seeks to examine the ear lobe capillary blood (ELCB) sampling technique adopted in the domain of respiratory medicine, specifically in the adult population. First, there will be a review of the physiology that supports Pitkin et al’s (1994) theory and an exploration of the research that underpins the technique. Second, this investigation will identify current national standards and/or guidelines, including the content of teaching programmes that deliver ELCB gas sample training to health professionals. In order to gain an understanding of the national approach to blood gas sampling, a specially designed questionnaire was distributed
The prescribing of long-term oxygen is determined after clinical assessment. Assessment criteria include arterial blood gas analysis, where the partial pressure of oxygen (PaO2) is consistently at or below 7.3 kilopascals (kPa) while breathing room air. Additionally, in the presence of pulmonary hypertension and/ or secondary polycythaemia, oxygen can be prescribed if the PaO2 is between 7.3 kPa and 8.0 kPa while breathing room air. Blood gas sampling should be undertaken when the individual has been free of chronic lung disease exacerbation for the previous 5 weeks, measured on two separate occasions not less than 3 weeks apart.
British Journal of Nursing, 2014, Vol 23, No 15
British Journal of Nursing. Downloaded from magonlinelibrary.com by 138.253.100.121 on November 30, 2015. For personal use only. No other uses without permission. . All rights reserved.
© 2014 MA Healthcare Ltd
CLINICAL FOCUS respiratory disease. However, a handful of trials, including Honarmand and Safavi (2008) and Stott et al (2008), were undertaken in an intensive care environment, encompassing a variety of underlying physiological conditions— but as the focus was on ELCB gas technique, they were deemed suitable for inclusion. These data show an evolutionary approach to vasodilatation. While Langlands and Wallace (1965) sought to arterialise the earlobe using heat from a light bulb, their comparative study, assessing arterial blood gas and ELCB gas analysis, reported no statistical differences between the PaO2, partial pressure of carbon dioxide (PaCO2) and the pH of the two samples. Olvia et al (1973) obtained ear lobe samples following manual massage of the ear lobe for 3 minutes, but discovered a reduction in PaO2 of the capillary sample compared with arterial as a reported consequence of tissue extracts. MacIntrye et al (1968) supported the finding that manual massage of the ear lobe alone was not an effective method to achieve adequate ‘arterialisation’ for ELCB gas sampling. However, massage with a vasoactive cream for 3 minutes was deemed appropriate in their hypotensive cohort. Godfrey et al’s (1971) study reported an achievement in arterialisation by application of a vasoactive cream (thurfyl nicotinate/Trafuril). Eleven of the 15 clinical studies presented in Table 1 specify this same approach. Interestingly, these studies indicate that there is support for the physiological rationale for vasodilation of the sample site, even in the absence of formal investigation. Importantly, however, there is firm agreement that manual massage of the ear alone is not recommended (Langlands and Wallace, 1965; MacIntrye at al, 1968; Godfrey et al, 1971; Olvia, 1973; Hughes, 1996; Higgins, 2008). Table 1 also shows that within these clinical trials the scalpel blade is the most frequently used incision tool and that sample collection time is rarely reported.
Table 1. Sampling techniques used in 15 published adult ELCB gas trials
Investigation During the last decade, the practical application of this technique has expanded into clinical care environments as a result of the publication of clinical trials, deeming arterialized ELCB gas sampling tobe simple, less invasive and a suitable alternative to traditional arterial sample collection (Pitkin et al, 1994; Fajec et al, 1998). These reported findings coincided with changes to the prescribing of domiciliary oxygen, which saw the end of FP10 prescribing and the introduction of oxygen assessment services and the Home Oxygen Order Form in 2006 (Wedzicha and Calverley, 2006). Alongside
British Journal of Nursing, 2014, Vol 23, No 15
Study
Sample size
Vasodilation
Incision tool
Sample time
Langlands and Wallace (1965)
16
Heat from a lightbulb
Scalpel and bung
Not specified
MacIntryre et al (1968)
14
Cream massaged for 3 minutes
Not specified
Not specified
Godfrey et al (1971)
8
Cream 10–15 minutes
Scalpel and bung
30 seconds
Olivia et al (1973)
Not given
Massage alone 3 minutes
Long-point lance
Not specified
Spiro et al (1976)
11
Cream 10 minutes Scalpel and bung
Not specified
Pitkin et al (1994)
40
Cream 10 minutes Scalpel
Not specified
Dar et al (1995)
55
Cream 3 minutes
Scalpel
Not specified
Dall’Ava-Santucci et al (1996)
81
Cream 5–10 minutes
Scalpel
Not specified
Sauty et al (1996)
115
Cream 5–10 minutes +/massage
Scalpel blade
Not specified
Fajec et al (1998)
70
Cream 5–10 minutes
BD lancet
Not specified
Verges et al (2005)
20
Cream 20 minutes Not specified
Not specified
Wimpress et al (2005)
252
Cream 10 minutes Scalpel blade
Not specified
Eaton et al (2001)
100
Cream 10 minutes Lancet
85%
Abstract
Arterialised ear lobe capillary blood (ELCB) gas sampling is a widely used clinical procedure undertaken across both primary and secondary care settings. The prevalence of this sampling method has grown among health professionals, coupled with a growing demand for domiciliary oxygen therapy in the UK, in particular for those who have chronic obstructive pulmonary disease (COPD). Research studies supporting arterialised ELCB gas sampling show inconsistencies in technique, and a survey of respiratory nurses’ current practice demonstrated wider inconsistencies. In the absence of national clinical guidelines to direct this practice, and an acknowledged and accepted under-calculation of partial pressure of oxygen, this article investigates the sampling method used to obtain arterialised ELCB gas sampling and consequently questions its reliability in practice. Key words: Arterialised earlobe capillary blood gas ■ Chronic obstructive pulmonary disease ■ COPD ■ Oxygen
Jane Young, Community Nurse Lecturer, Anglia Ruskin University, Cambridge Accepted for publication: June 2014
838
Background: ELCB gas sampling to fellow respiratory colleagues at an annual national conference. These findings will be presented and discussed, leading to a review of practice capillary blood gas protocols. Following this data collection and analysis, discussion of findings and implications for the future will be discussed.
Context: respiratory disease The burden of respiratory disease and in particular chronic obstructive pulmonary disease (COPD) is clear: it accounts for around 23 000 deaths in England (Department of Health (DH), 2011) and a financial cost amounting to £492 million per year (Britton, 2003). Improving survival in COPD can be achieved through the administration of long-term oxygen therapy which corrects hypoxaemia (Nocturnal Oxygen Therapy Trial Group, 1980; Medical Research Council Working Party, 1981). Consequently, recent years have seen an increase in oxygen provision. Figures indicate that an estimated 85 000 patients have oxygen at home at a cost of £110 million per year (National Health Service Primary Care Commissioning (NHSPCC, 2011). IMPRESS (2011) proposes that 60% of this group have COPD, but that 30% of patients receive oxygen without proven clinical benefit in contrast to approximately 20% of severe COPD patients, who would benefit from long-term oxygen therapy but do not receive it.
The physiology of ELCB gas sampling, which is deemed a suitable substitute for blood gas analysis, has been described by Higgins (2008). Capillaries are the connectors between arterioles and venules, and thereby connect the arterial and venous networks. The blood obtained by skin puncture is not purely capillary: it is a mixture of capillary, arteriole and venule. Physiologically, the arterial blood network commands a higher pressure than the venous network, which is the rationale for regarding a capillary sample as similar to an arterial one. Furthermore, the correlation of capillary and arterial blood is greater when the PaO2 is lower as a result of less arteriole/venous difference. Hughes (1996) and Higgins (2008) state that increasing the blood flow through the capillary bed achieves arterialisation of capillary blood and subsequently has the biggest effect in reducing arteriovenous (AV) differences— this provides the physiological rationale for vasodilating the puncture site. However, Higgins (2008), Hughes (2009) and Richter et al (2014) all acknowledge that there is a lack of formalised research into the effectiveness of ‘arterialising’ ear lobes for capillary blood gas sampling and support further investigation. The sampling techniques used in 15 published adult ELCB gas trials are presented in Table 1. The majority of the trials included in this table were specific to patients who had an underlying
© 2014 MA Healthcare Ltd
B
lood gas analysis has historically been achieved by means of arterial puncture (Eaton et al, 2001). Yet recent years have seen a change in blood gas sampling methods and the use of capillaries (Pitkin et al, 1994) for collecting samples is now regarded as questionable (Fajec et al, 1998; Sauty et al, 1996; Eaton et al, 2001; Stott et al, 2008; Honarmand and Safavi, 2008). This exploratory investigation seeks to examine the ear lobe capillary blood (ELCB) sampling technique adopted in the domain of respiratory medicine, specifically in the adult population. First, there will be a review of the physiology that supports Pitkin et al’s (1994) theory and an exploration of the research that underpins the technique. Second, this investigation will identify current national standards and/or guidelines, including the content of teaching programmes that deliver ELCB gas sample training to health professionals. In order to gain an understanding of the national approach to blood gas sampling, a specially designed questionnaire was distributed
The prescribing of long-term oxygen is determined after clinical assessment. Assessment criteria include arterial blood gas analysis, where the partial pressure of oxygen (PaO2) is consistently at or below 7.3 kilopascals (kPa) while breathing room air. Additionally, in the presence of pulmonary hypertension and/ or secondary polycythaemia, oxygen can be prescribed if the PaO2 is between 7.3 kPa and 8.0 kPa while breathing room air. Blood gas sampling should be undertaken when the individual has been free of chronic lung disease exacerbation for the previous 5 weeks, measured on two separate occasions not less than 3 weeks apart.
British Journal of Nursing, 2014, Vol 23, No 15
British Journal of Nursing. Downloaded from magonlinelibrary.com by 138.253.100.121 on November 30, 2015. For personal use only. No other uses without permission. . All rights reserved.
© 2014 MA Healthcare Ltd
CLINICAL FOCUS respiratory disease. However, a handful of trials, including Honarmand and Safavi (2008) and Stott et al (2008), were undertaken in an intensive care environment, encompassing a variety of underlying physiological conditions— but as the focus was on ELCB gas technique, they were deemed suitable for inclusion. These data show an evolutionary approach to vasodilatation. While Langlands and Wallace (1965) sought to arterialise the earlobe using heat from a light bulb, their comparative study, assessing arterial blood gas and ELCB gas analysis, reported no statistical differences between the PaO2, partial pressure of carbon dioxide (PaCO2) and the pH of the two samples. Olvia et al (1973) obtained ear lobe samples following manual massage of the ear lobe for 3 minutes, but discovered a reduction in PaO2 of the capillary sample compared with arterial as a reported consequence of tissue extracts. MacIntrye et al (1968) supported the finding that manual massage of the ear lobe alone was not an effective method to achieve adequate ‘arterialisation’ for ELCB gas sampling. However, massage with a vasoactive cream for 3 minutes was deemed appropriate in their hypotensive cohort. Godfrey et al’s (1971) study reported an achievement in arterialisation by application of a vasoactive cream (thurfyl nicotinate/Trafuril). Eleven of the 15 clinical studies presented in Table 1 specify this same approach. Interestingly, these studies indicate that there is support for the physiological rationale for vasodilation of the sample site, even in the absence of formal investigation. Importantly, however, there is firm agreement that manual massage of the ear alone is not recommended (Langlands and Wallace, 1965; MacIntrye at al, 1968; Godfrey et al, 1971; Olvia, 1973; Hughes, 1996; Higgins, 2008). Table 1 also shows that within these clinical trials the scalpel blade is the most frequently used incision tool and that sample collection time is rarely reported.
Table 1. Sampling techniques used in 15 published adult ELCB gas trials
Investigation During the last decade, the practical application of this technique has expanded into clinical care environments as a result of the publication of clinical trials, deeming arterialized ELCB gas sampling tobe simple, less invasive and a suitable alternative to traditional arterial sample collection (Pitkin et al, 1994; Fajec et al, 1998). These reported findings coincided with changes to the prescribing of domiciliary oxygen, which saw the end of FP10 prescribing and the introduction of oxygen assessment services and the Home Oxygen Order Form in 2006 (Wedzicha and Calverley, 2006). Alongside
British Journal of Nursing, 2014, Vol 23, No 15
Study
Sample size
Vasodilation
Incision tool
Sample time
Langlands and Wallace (1965)
16
Heat from a lightbulb
Scalpel and bung
Not specified
MacIntryre et al (1968)
14
Cream massaged for 3 minutes
Not specified
Not specified
Godfrey et al (1971)
8
Cream 10–15 minutes
Scalpel and bung
30 seconds
Olivia et al (1973)
Not given
Massage alone 3 minutes
Long-point lance
Not specified
Spiro et al (1976)
11
Cream 10 minutes Scalpel and bung
Not specified
Pitkin et al (1994)
40
Cream 10 minutes Scalpel
Not specified
Dar et al (1995)
55
Cream 3 minutes
Scalpel
Not specified
Dall’Ava-Santucci et al (1996)
81
Cream 5–10 minutes
Scalpel
Not specified
Sauty et al (1996)
115
Cream 5–10 minutes +/massage
Scalpel blade
Not specified
Fajec et al (1998)
70
Cream 5–10 minutes
BD lancet
Not specified
Verges et al (2005)
20
Cream 20 minutes Not specified
Not specified
Wimpress et al (2005)
252
Cream 10 minutes Scalpel blade
Not specified
Eaton et al (2001)
100
Cream 10 minutes Lancet
85%
