Measurement of combined oximetry and cutaneous capnography during flexible bronchoscopy

Transcription

1 Eur Respir J 2006; 28: DOI: / CopyrightßERS Journas Ltd 2006 Measurement of combined oximetry and cutaneous capnography during fexibe bronchoscopy P.N. Chhajed, R. Rajasekaran, B. Kaegi, T.P. Chhajed, E. Pfimin, J. Leuppi and M. Tamm ABSTRACT: The aim of the present study was to assess the feasibiity of measuring combined arteria oxygen saturation measured by puse oximetry (Sp,O 2 ) and cutaneous carbon dioxide tension (Pc,CO 2 ) to monitor ventiation and quantify change in Pc,CO 2 during bronchoscopy. Combined Sp,O 2 and Pc,CO 2 were measured at the ear obe in 114 patients. In four patients, the ear-cip sipped and they were excuded. In tota, 11 patients had artefacts with Sp,O 2 recordings, thus, Sp,O 2 was anaysed in 99 patients. Spirometry data were avaiabe in 77 patients. Mutivariate anaysis of covariance and ogistic regression were used for statistica anayses. Mean baseine Pc,CO 2 was kpa (36 8 mmhg) and mean rise in the Pc,CO 2 during bronchoscopy was kpa ( mmhg), whie mean Pc,CO 2 at the end of bronchoscopy was kpa (44 9 mmhg). Baseine Pc,CO 2 and the owest Sp,O 2 were significanty associated with peak Pc,CO 2 and the change in Pc,CO 2 during bronchoscopy. Risk of significant hypoxaemia (Sp,O 2 f90%) was ower for a higher baseine Sp,O 2. Peak Pc,CO 2 was directy associated with significant hypoxaemia. There was no significant association in the baseine Pc,CO 2, peak Pc,CO 2, baseine Sp,O 2 or the owest Sp,O 2 comparing patients with and without chronic obstructive pumonary disease. In concusion, it is feasibe to measure combined puse oximetry and cutaneous carbon dioxide tension effectivey to monitor ventiation during fexibe bronchoscopy. AFFILIATIONS Pumonary Medicine, University Hospita Base, Base, Switzerand. CORRESPONDENCE P.N. Chhajed Pumonary Medicine University Hospita Base Petersgraben 4 CH-4031 Base Switzerand Fax: E-mai: PChhajed@uhbs.ch Received: Juy Accepted after revision: Apri KEYWORDS: Bronchoscopy, cutaneous carbon dioxide tension, hypercapnia, hypoxia, oximetry Fexibe bronchoscopy under oca anaesthesia and sedation is widey performed to diagnose and manage a variety of ung diseases. The purpose of sedation is to faciitate examination of the tracheobronchia tree, carry out the necessary diagnostic or interventiona procedures, and provide patient comfort [1 4]. Oximetry measures the oxygenation of bood and can detect hypoxaemia, but it cannot detect hypercarbia and hence the adequacy of ventiation [5]. When bronchoscopy is performed under conscious sedation without suppementa oxygen, oxygen desaturation wi occur rapidy giving a good indication of ventiatory status. It has recenty been shown that puse oximetry is a usefu too to assess ventiatory abnormaities, but ony in the absence of suppementa inspired oxygen [6]. However, most centres routiney offer oxygen suppementation to patients during fexibe bronchoscopy [7]. Due to the S-shaped curve of the oxygen dissociation curve, in such situations the aveoar carbon dioxide tension wi have to increase further before significant hypoxaemia is manifested [8]. The British Thoracic Society (BTS) guideines recommend that oxygen suppementation shoud be used to achieve an oxygen saturation (Sp,O 2 ) of at east 90% to reduce the risk of significant arrhythmias during the procedure and aso in the post-operative recovery period [2]. Furthermore, they suggest that care shoud be taken to be aert to signs of respiratory faiure in patients on oxygen suppementation, who may have safe oximetry readings, but who may be deveoping carbon dioxide retention [2]. Therefore, a reiabe substitute of carbon dioxide arteria tension (Pa,CO 2 ) measured noninvasivey is required as it might enhance patient safety during fexibe bronchoscopy. In intubated patients or patients under stabe conditions without ora eakage, end-tida carbon dioxide tension has a good correation with Pa,CO 2 [9, 10]. However, during endoscopy procedures under sedation, reguar breathing is often disturbed by moving, coughing or changes between nose and mouth ventiation, causing European Respiratory Journa Print ISSN Onine ISSN VOLUME 28 NUMBER 2 EUROPEAN RESPIRATORY JOURNAL

2 P.N. CHHAJED ET AL. MONITORING DURING BRONCHOSCOPY eakage and artefacts or misinterpretation of the data acquired with end-tida carbon dioxide measurements. These probems often restrict the use of side-stream capnography in cinica practice [10]. Measurement of cutaneous carbon dioxide tension (Pc,CO 2 ) with a digita sensor has recenty been reported [11]. The Pc,CO 2 vaues have been shown to have a good correation with arteria bood gas measurements [12, 13]. A rise in Pc,CO 2 measurement has been reported during medica thoracoscopy and coonoscopies [10, 13]. The present authors aimed to assess the feasibiity of measuring combined puse oximetry (Sp,O 2 ) and Pc,CO 2 at the ear obe to monitor ventiation and quantify the degree of change in Pc,CO 2 during fexibe bronchoscopy under oca anaesthesia and sedation. PATIENTS AND METHODS Combined oximetry and Pc,CO 2 were prospectivey measured in 114 patients undergoing fexibe bronchoscopy in an observationa fashion (monitoring system from Sentec AG, Therwi, Switzerand). The combined cutaneous digita sensor was paced on the ear obe of a patients prior to the procedure and was removed when the patient eft the bronchoscopy suite. Fexibe bronchoscopy was performed under oca anaesthesia and sedation. Combined sedation was achieved with intermittent bouses of intravenous midazoam and 5 mg of hydrocodone [1]. A patients received suppementa nasa oxygen at 2 4 L?min -1. Significant hypoxaemia (Sp,O 2 f90%) during fexibe bronchoscopy was successfuy treated with jaw support or nasopharyngea tube insertion [7]. The duration of bronchoscopy was cacuated from the administration of sedation unti the fexibe bronchoscope was removed from the tracheobronchia tree. Bronchoaveoar avage (BAL) was performed in 57 patients, endobronchia biopsy in 32, bronchia washings in 19, transbronchia neede aspiration in 18, transbronchia biopsy in 15 patients and bronchia brushings in 11 patients. Spirometry data prior to bronchoscopy was avaiabe in 77 patients. Patients with chronic obstructive pumonary disease (COPD) were defined using the American Thoracic Society/European Respiratory Society guideines [14]. Statistica anaysis Data are presented as mean SD. Mutivariate anaysis was performed using anaysis of covariance to examine peak Pc,CO 2, change in Pc,CO 2 from baseine, and change in Pc,CO 2 adjusted for baseine Pc,CO 2 during bronchoscopy as dependent factors versus patient age, dose of midazoam (mg?kg -1 ), baseine Pc,CO 2 and owest Sp,O 2 as independent factors. Scatterpots are provided for the association of peak Pc,CO 2 and change in Pc,CO 2 with duration of procedure. ANOVA was used to examine the association between the type of samping procedure during bronchoscopy with the change in Pc,CO 2. Logistic regression was used to examine independent factors associated with significant hypoxaemia (Sp,O 2 f90%) and COPD. The t-test was used to compare significance between the baseine and peak Pc,CO 2 during bronchoscopy and Pc,CO 2 at owest Sp,O 2 and the peak Pc,CO 2 during bronchoscopy. RESULTS The mean duration of the procedure was min. In four patients, the ear-cip sipped off the ear obe due to patient movement. These patients were not incuded in the anaysis as the equiibration had to be achieved again and there was oss of data recording points. Therefore data anaysis was performed in 110 patients (70 maes and 40 femaes, mean age yrs). In 11 patients, the Sp,O 2 was not incuded in the anaysis due to artefacts produced by coughing or a ow signa whist recording. Therefore, Pc,CO 2 measurements, for the purposes of data anaysis, were avaiabe in 110 patients and both oximetry and Pc,CO 2 measurements were avaiabe in 99 patients. Therefore, for mutivariate anaysis ony data from patients with both oximetry and Pc,CO 2 were used. Hypoxaemia during the procedure was successfuy treated with jaw support or nasopharyngea tube insertion in a patients. None of the patients deveoped severe respiratory depression resuting in administration of sedation reversa medication or in abandoning the procedure without competion. The indications for bronchoscopy were: 1) suspected ung maignancy, 42 (38%) patients; 2) radioogica infitrates, 31 (28%) patients; 3) haemoptysis, nine (8%) patients; 4) suspected interstitia ung disease, nine (8%) patients; 5) suspected sarcoidosis, five (5%) patients; 6) post-airway stent inspection, four (4%) patients; 7) cough, three (3%) patients; 8) post-ung surgery, two (2%) patients; and 9) evauation of posttracheostomy trachea stenosis, arngea papioma and mucociiary dyskinesis (a n51). The mean dose of midazoam administered was mg?kg -1. The mean baseine Pc,CO 2 was kpa (36 8 mmhg) and the mean peak Pc,CO 2 was kpa (46 9 mmhg; p,0.0001). The peak Pc,CO 2 during the procedure was recorded at a mean duration of 13 7 min. The mean rise in the Pc,CO 2 during the procedure was kpa ( mmhg). The mean Pc,CO 2 at the end of the procedure was kpa (44 9 mmhg) and at the time of remova of the sensor was kpa (44 9 mmhg). A rise in Pc,CO 2 was observed in a patients except one. The baseine Sp,O 2 was 97 2%. The owest mean Sp,O 2 was 93 4%. The owest Sp,O 2 in patients who desaturated from their baseine Sp,O 2 measurement was recorded at a mean duration of 9 6 min. The mean Pc,CO 2 measured at owest Sp,O 2 was kpa (44 14 mmhg) and the mean peak Pc,CO 2 recorded subsequenty was kpa (51 13 mmhg; p,0.0001). Factors associated with peak Pc,CO 2 and change in Pc,CO 2 during the study The peak Pc,CO 2 during the study was significanty associated with the baseine Pc,CO 2 (p,0.0001) and owest Sp,O 2 (p50.016). A higher baseine Pc,CO 2 was associated with the peak Pc,CO 2 (b50.8). However, there was an inverse reationship of the owest Sp,O 2 with the peak Pc,CO 2, thus, the manifestation of a ower Sp,O 2 was associated with the peak Pc,CO 2 (b5-0.4). Change in Pc,CO 2 (difference in baseine and peak Pc,CO 2 ) was aso significanty associated with baseine Pc,CO 2 (p50.024) and owest Sp,O 2 (p50.016). Both of these factors had an inverse reationship with the change in Pc,CO 2, thus, patients manifesting a ower Sp,O 2 (b5-0.4) and a ower baseine Pc,CO 2 (b5-0.2) woud have a higher change in Pc,CO 2. Simiary, the change in Pc,CO 2 divided by the baseine Pc,CO 2 (adjusting the change in Pc,CO 2 for baseine) was aso significanty associated with baseine Pc,CO 2 (p,0.0001) and owest SO 2 c EUROPEAN RESPIRATORY JOURNAL VOLUME 28 NUMBER 2 387

3 MONITORING DURING BRONCHOSCOPY P.N. CHHAJED ET AL. (p50.016). This anaysis highights that baseine Pc,CO 2 and the owest Sp,O 2 are inked to the peak Pc,CO 2 as we as the rise in Pc,CO 2 during bronchoscopy. There was no significant reationship of age and midazoam dosage with the peak Pc,CO 2, change in Pc,CO 2 and the change in Pc,CO 2 /baseine Pc,CO 2. There was aso no association of peak Pc,CO 2 and change in Pc,CO 2 with the procedure duration (fig. 1). This factor was not incuded in the mutivariate anaysis as there appear to be two groups of patients; one group with higher peak Pc,CO 2 and change in Pc,CO 2 with a short duration of procedure and the other group of patients who have a higher peak and change in Pc,CO 2 with a onger duration of procedure. To assess the infuence of procedure on change in Pc,CO 2 and change in Pc,CO 2 /baseine Pc,CO 2, these were categorised as foows: 1) transbronchia biopsy ony and transbronchia neede aspiration ony (n510); 2) BAL ony (n542); 3) transbronchia biopsy, transbronchia neede aspiration, and BAL in a combination of two or more (n516); and 4) bronchia washings and/or endobronchia biopsy (n542). There was no significant association between the procedures performed and change in Pc,CO 2 (p50.3) and change in Pc,CO 2 /baseine Pc,CO 2 (p50.2) during bronchoscopy. Factors associated with significant hypoxaemia and COPD In tota, 15 patients had significant hypoxaemia during bronchoscopy. A ower baseine Sp,O 2 (p50.003; odds ratio a) Peak cutaneous CO 2 mmhg b) Changes in cutaneous CO 2 mmhg Duration of procedure min FIGURE 1. Scatter pot of duration of procedure in a) peak cutaneous carbon dioxide and b) change in cutaneous carbon dioxide. (OR) 0.6) and the peak Pc,CO 2 (p50.041; OR 1.1) were significanty associated with significant hypoxaemia. Therefore, with a higher baseine Sp,O 2 the risk of significant hypoxaemia is ower and the peak Pc,CO 2 is directy associated with significant hypoxaemia. Patient age, duration of procedure, midazoam dose and baseine Pc,CO 2 were not associated with significant hypoxaemia. In tota there were 25 patients with COPD. The mean forced expiratory voume in one second in patients with mid, moderate, severe and very severe COPD was 90 10% (n54), 64 8% (n513), 39 5% (n56) and 25 3% (n52), respectivey. There was no significant association in the baseine Pc,CO 2, peak Pc,CO 2, baseine Sp,O 2, or the owest Sp,O 2 comparing patients with and without COPD. DISCUSSION Recenty, Pc,CO 2 measurements obtained using the device used in this study have been shown to have a good correation with arteria carbon dioxide vaues when.100 sampes were compared (R50.95) [13]. The findings of the present study show that ventiation can be effectivey monitored during fexibe bronchoscopy using combined oximetry and Pc,CO 2 measurement. In a study of 22 patients, an increase in Pc,CO 2 has been shown to occur during fexibe bronchoscopy [5]. However, EVANS et a. [5] concuded that the technoogy they used for Pc,CO 2 monitoring was compex. Measurement of Pc,CO 2 in the current study was simpe and did not ead to a deay in the start of the procedure or any compications reated to the equipment. The potentia compication when using this device is burning of the skin as the sensor is heated to a temperature of 42uC. The recommended maximum duration for which a sensor can be paced cutaneousy at 42uC is 8 h [15]. None of the patients in the present study had an apparent burn on the skin. The BTS guideines caution physicians to monitor signs of respiratory faiure in patients undergoing fexibe bronchoscopy on oxygen suppementation that may have safe oximetry readings, but may be deveoping carbon dioxide retention. Patients with a higher baseine Pc,CO 2 are at a greater risk of deveoping a higher peak Pc,CO 2. Furthermore, the peak Pc,CO 2 was significanty associated with the owest Sp,O 2 during bronchoscopy. The resuts of the current study show that it is feasibe to measure continuous Pc,CO 2 during bronchoscopy, which has been shown to be a good surrogate of Pa,CO 2 [2, 12, 13]. Based on the findings of the present study, no specific trend was observed in the association between peak Pc,CO 2 and change in Pc,CO 2 with procedure duration, both a short and a onger procedure duration were associated with the peak Pc,CO 2 and change in Pc,CO 2. The abiity to effectivey measure Pc,CO 2 is an important step in patient monitoring as diagnostic bronchoscopies are performed using routine sedation and aso drugs, such as propofo, which are considered as genera anaesthetics are being increasingy used aso in the absence of a trained anaesthetist [16 19]. The mean duration to the manifestation of owest Sp,O 2 was earier than the mean duration to the peak Pc,CO 2. Therefore, it seems impossibe to predict the occurrence of owest Sp,O 2 based on rising Pc,CO 2 vaues. The owest Sp,O 2 manifested was significanty associated with peak Pc,CO 2. The hypothesis for this observation is that hypoventiation during fexibe bronchoscopy performed under sedation with oxygen suppementation is mutifactoria, and not ony due to centra 388 VOLUME 28 NUMBER 2 EUROPEAN RESPIRATORY JOURNAL

4 P.N. CHHAJED ET AL. MONITORING DURING BRONCHOSCOPY respiratory depression, in which case a rise in Pc,CO 2 woud precede significant hypoxaemia due to the nature of the oxygen dissociation curve. Hypoventiation during fexibe bronchoscopy is therefore due to a combination of upper airway obstruction, aveoar hypoventiation caused by sedative medication and the procedure itsef [7]. The effective treatment of hypoxaemia with jaw support or nasopharyngea tube insertion supports the roe of upper airway obstruction eading to acute hypoxaemia during fexibe bronchoscopy [7]. The rise in Pc,CO 2 manifested thereafter refects aveoar hypoventiation, which is ikey to be due to the combined effect of sedatives (centra respiratory depression), as we as the procedure itsef potentiay eading to ventiation perfusion mismatch. The findings of the current study show that after effective treatment of upper airway obstruction, there continues to be a rise in Pc,CO 2 refecting hypoventiation. Therefore, Sp,O 2 aone is not sufficient to monitor the compete ventiation status of the patient during bronchoscopy, thus highighting the vaue of combined oximetry and cutaneous capnography during bronchoscopy. The permissibe eve of Pc,CO 2 rise during bronchoscopy is not known. The BTS guideines state that the use of sedation in patients with severe COPD has increased risks reating to potentia carbon dioxide retention [2]. The findings of the present study show that patients with COPD who are not in hypercapnic respiratory faiure are at an equa risk of hypercapnia as we as hypoxaemia compared with patients without COPD. Based on the findings of the current study (mean rise in Pc,CO 2 of kpa), the present authors specuate that a rise of 2.0 kpa in Pc,CO 2 from baseine may be an indication to imit further administration of sedatives and needs to be confirmed in future studies. In concusion, the current study demonstrates the feasibiity of measuring combined oximetry and cutaneous capnography effectivey to monitor ventiation during fexibe bronchoscopy. Patients with COPD who are not in hypercapnic respiratory faiure have a simiar risk of hypoxaemia and hypercapnia compared with those without COPD during bronchoscopy. The peak Pc,CO 2 is higher in patients with a higher baseine Pc,CO 2 and is associated with owest Sp,O 2 during bronchoscopy. Significant hypoxaemia is associated with the peak Pc,CO 2 and baseine Sp,O 2. With the current study resuts, it is not possibe to predict and accuratey seect a group of patients who shoud undergo capnography during bronchoscopy. Patients with eevated baseine Pa,CO 2 or a ow baseine Sp,O 2 wi have the benefit of better monitoring of ventiation using such a device. Specificay, patients with a onger duration of procedure did not show a different rise in Pc,CO 2 compared with the others. Furthermore, the current authors expected an association of the sedative dose with rise in cutaneous carbon dioxide tension, but that was aso not the case. Therefore, future studies need to anayse the different patient groups with regards to the baseine cutaneous carbon dioxide tension to potentiay imit the appication of cutaneous capnography to ony a specific group of patients. ACKNOWLEDGEMENTS The authors woud ike to thank F. Baty and A. Schötzau for their assistance with performing the statistica anaysis. The authors woud aso ike to thank Sentec AG (Therwi, Switzerand) for providing the combined cutaneous carbon dioxide and oximetry monitoring system. REFERENCES 1 Stoz D, Chhajed PN, Leuppi JD, Brutsche M, Pfimin E, Tamm M. Cough suppression during fexibe bronchoscopy using combined sedation with midazoam and hydrocodone: a randomised, doube bind, pacebo controed tria. 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