Salome schafroth Torok, MD; Jorg D.Leuppi, MD; Florent Baty, PhD; Michael Tamm, MD, FCCP; and Prashant N. Chhajed,MD Chest 2008;133; ;Prepublished online March 13,2008; DOI /chest R1 CHAEJUNGMIN

Long-term oxygen therapy is routinely used in patients with hypoxemia due to -Severe obstructive and restrictive pulmonary diseases -Interstitial lung diseases -Pulmonary hypertension Indications -PaO2 < 55mmHg on room air -Even if 56< PaO2 < 59mmHg on room air with polycythemia, evidence of pulmonary hypertension, episodes of right heart failure that reflect the systemic effects of chronic hypoxemia Therapeutic goal- Pulse oximetric PaO2>90% during rest, sleep, exertion

Indications vary depending on the country In Switzerland- contains ABGA ABGA is invasive and painful In hypercapnic patients→respiratory drive is suppressed, PaO2 is not adequate for estimation of oxygen requirements PaCO2 is also essential Transcutaneous carbon dioxide tension(PtcCO2) is a noninvasive surrogate of PaCO2 CO2- high tissue solubility, diffuses through the skin, can be detected by a sensor at the skin surface Combined cutaneous capnography and oximetry is now possible with a single earlobe sensor.

The application of heat to the skin surface increases blood flow into the arteriovenous anastomoses and the venous plexus, and capillary blood is arterialized. Patient factors that may influence PtcCO2 values include -hypoperfusion at the site of measurement -Shock -Edema -skin thickness -vasoconstricting drugs. Combining oximetry and cutaneous capnography may potentially reduce the need of ABGA. Hence, we undertook this study to evaluate the feasibility of combined oximetry and cutaneous capnography and to compare the SpO2 and PtcCO2 with arterial blood gas values in patients who underwent assessment for home oxygen therapy.

대상 -20 patients attending the lung function laboratory of the Clinic of Pulmonary Medicine at the University Hospital Basel. 도구 -combined oximetry/capnography sensor (Sentec AG; Therwil, Switzerland) providing noninvasive and continuous estimation of Paco2 and arterial oxygen saturation (SaO2). -the sensor is warmed to a constant surface temperature of 42°C → improve local arterialization and accelerate carbon dioxide diffusion.

Baseline arterial blood gas analysis was performed at room air →Combined oximetry and cutaneous capnography was performed by placing the calibrated digital sensor on the patient’s earlobe → Oxygen flow was gradually increased incrementally by 0.5 to 1 L/min until Sao2 was 90%. At the end of oxygen titration, another arterial blood gas analysis was performed → the PtccCO2 and SpO2 measurements from the combined oximetry and capnography device at this point in time were noted. There is a difference between the two analyzers in assessing SaO2. -In analyzer A, the SaO2 is calculated -in analyzer B, it is measured. For technical reasons, in two patients we only have values from analyzer A, and in one patient we only have values from analyzer B.

The mean age : 69.7 ± 10.4 years (11 female and 9 male) 15 of 20 : COPD 8 of 15 : pulmonary hypertension Other : sarcoidosis, lung resection for infection or carcinoma, and idiopathic or secondary pulmonary hypertension. The mean FEV1 : 36.2 ± 15.8% predicted the mean FVC : 55.6 ± 19.6% predicted.

During oxygen titration -Mean Pao2 : 53.2 ± 8.1 mm Hg → 75.9 ± 13.3 mm Hg -Mean carbon dioxide : 45.9 ± 8.7 → 47.8 ± 9 mm Hg

guidelines for the assessment of home oxygen therapy vary, depending on the country. -is there a need to monitor CO2 routinely?? Significant drift of Ptcco2 values over time. -monitoring patients for several hours > in the clinical setting of oxygen titration. the lack of additional information provided by arterial blood gas analysis (eg, pH and bicarbonate levels). -arterial blood gas analysis at baseline will still be needed

combined oximetry and cutaneous capnography is feasible Combined oximetry and cutaneous capnography has the potential to reduce the number of arterial punctures needed in this clinical setting and to reduce health-care costs.