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Ann Thorac Surg 1999;68:2033-2038
© 1999 The Society of Thoracic Surgeons
a Cardiovascular Institute, University of Dresden, Dresden, Germany
Address reprint requests to Dr Wagner, Cardiovascular Institute, University of Dresden, Fetscherstrasse 76, 01307 Dresden, Germany;
e-mail: hkz{at}rcs.urz.tu-dresden.de
Presented at the Thirty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 25–27, 1999.
Abstract
Background. Following lung transplantation, prompt diagnosis and therapy of acute pulmonary rejection and infection episodes relies primarily upon changes in pulmonary function and determines long-term outcome. We tested a new system that allows daily monitoring of the patient’s pulmonary status even after discharge from the hospital.
Methods. Seven lung transplant recipients from our center were equipped with a telemetric monitoring device consisting of a portable flowmeter and a special modem unit. The flowmeter measures forced vital capacity (FVC), forced expiratory volume per second (FEV1), and mid expiratory flows (MEFs), encodes information like fever, cough, and dyspnea in a binary code form, and stores all values in a 32 kB memory unit. After its use, the patient positions the flowmeter onto the modem unit which automatically connects to a central computer at our center to transfer all saved data. The whole set can be used via any regular phone jack. The patient’s file in the computer can be checked every day.
Results. All patients learned to use the unit during their postoperative stay or during later follow-up, and were able to apply the system at home. In a mean follow-up period of 10.3 ± 2.2 months, 15 episodes of significant deterioration in home pulmonary function tests (PFTs) (>10%) were registered in 6 patients, which were all confirmed by in-hospital body plethysmography. They resulted in diagnoses of 4 episodes of acute rejection, 6 cases of beginning bacterial pneumonia, and 5 cases of, most likely, viral tracheobronchitis. Only 1 patient had to be admitted to the hospital. All patients PFTs returned to previous values after treatment.
Conclusions. Telemetric monitoring of graft function in lung transplant recipients allows reliable early diagnosis and treatment of infection or rejection, which might help to prevent exacerbation of the pathology and reduce quantity of amounting graft dysfunction.
Lung transplantation is now a recognized treatment for patients with end-stage pulmonary disease. Despite significant improvement in postoperative management, infection and rejection remain the main causes for early morbidity and mortality after lung transplantation [1]. Recent data indicate that development of obliterative bronchiolitis (OB), the main long-term cause of death, might correlate with parenchymal injury during reperfusion and high incidence of acute rejection and infection [2].
Since deterioration of pulmonary function, in particular of expiratory volumes, is a reliable indicator for the onset of rejection or infection episodes, surveillance of those parameters has become the most important diagnostic tool after lung transplantation. Early diagnosis and therapy might help to reduce the amount of irreversible parenchymal injury in the graft. We tested a new system that not only allows daily monitoring of expiratory volumes after discharge of the patient, but also daily transmission of those values to the hospital via telemetry.
In the following, we report about our primary experiences in regards to reliability and practicability of such telemetrically monitored home spirometry, comparing it with corresponding values of regular body plethysmography, and analyzing its impact on patient morbidity and mortality.
Material and methods
Telemetric surveillance system
The hardware of the system consists of three parts: the patient’s home spirometer, two modems, and a personal computer (PC) located at the transplant center or any location convenient for the transplant physician.
The spirometer (AM1, Jaeger GmbH, Würzburg, Germany) uses an exchangeable sensor unit for the measurement of expiratory volumes integrated into a unit that analyzes forced expiratory volume per second (FEV1), peak flow, and mid expiratory flow (MEF) 25 to 75 values (volume 0 to 8 liter, flow 60 to 840 liter/min) and shows selectively one of those parameters on a digital display. It also has the capacity to memorize for three further parameters a value between 0 and 3, that can be deliberately defined by the transplant physician (eg, fever, cough, dyspnea). The included memory unit has a storage capacity of 300 kB, or 400 measurements, which allows storage of values for more than 3 months if used twice daily. To improve compliance, the unit holds a programmable beeper to remind the patient to use it at certain hours. The spirometer weighs only 140 g, fits into most larger coat pockets or hand bags (dimensions 8.5 x 11 x 3.5 cm) and comes with a custom-made bag allowing easy transportation.
The modem unit (HC1, Jaeger GmbH) is also given to the patient after he or she has been educated how to use and connect it to any regular phone jack. The unit is automatically activated when the spirometer is positioned into the appropriate slot (on the modem) to dial a preprogrammed phone number (set by the physician) that connects it with the PC at the transplant center to transfer all registered data.
The third part is an IBM-compatible PC to run the software, equipped with a modem to receive transmitted data. It requires a Pentium processor to be able to run Windows NT4.0 or higher, a minimum of 32 MB RAM and free hard disc space of at least 40 MB.
The AMOS-Hub software (Jaeger GmbH) allows the on-line receiving and storing of data coming in via modem. It also checks the whole system automatically on a regular basis and stores reports for every system check and all incoming transmissions, allowing retrospective analysis for eventual troubleshooting.
The AMOS software (version 2.0, Jaeger GmbH) requires a MS-windows surface (Version 95 or higher) and serves to store and process data from the spirometer. A personal file is assigned to every patient to store his basic data (name, sex, date of birth, weight, and height) and to identify each patient with an ID number that can be determined by the transplant physician. The home spirometer is connected to the PC for transfer of personal data to assign the device to the respective patient. Later on, it is through the ID number that incoming data via telemetric transmission will be directed to the correct patient file. The software allows the creation of reports of two different types: (1) the "standard report," to plot trends for each parameter (FVC, FEV1, MEF 25 to 75, PEF) with variable scaling of both X (time) and Y (volume) axes with the possibility of annotating remarks to highlight particular events within the graph (Fig 1); (2) the "report I" that includes a 30-days’ and a 6-months’ trend, a 60-day variability for two parameters, respectively, incidences of symptoms and events, as well as a comment section (Fig 2). In case of problems with data transferal or analysis, the company offers online service for troubleshooting at no extra charge.
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Patients
Since December 1997, 7 lung transplant recipients from our center were randomly chosen and equipped with the described telemetric monitoring device. Four of those had a heart–lung transplantation for primary (n = 3) or secondary pulmonary hypertension, 3 had a single lung transplantation for interstitial pulmonary fibrosis (n = 2) and chronic obstructive pulmonary disease (COPD) (n = 1). All patients were educated during their postoperative stay or during later follow-up on how to use their home spirometer and how to operate the modem for telemetric transfer of the obtained measurements.
Postoperative management
Immunosuppression was induced with preoperative oral cyclosporine (2 mg/kg), intraoperative methylprednisolone (500 mg), and one dose of antithymocyte globulin (ATG) (Merieux; 15 mg/kg; Institut Merieux, Leimen, Germany) 8 hours after reperfusion of the graft. Maintenance immunosuppression consisted of cyclosporine (target whole blood level 200 to 250 ng/ml), mucophenolate mofetil (target serum level 2 to 4 µg/ml) and prednisolone (tapered from 2 to 0.1 mg/kg/day at 3 months). Episodes of acute rejection were treated with intravenous pulsed steroids (methylprednisolone 500 mg/day for 3 days); if rejection recurred more than once within 3 weeks after intravenous (IV) steroids, patients were switched from cyclosporine to tacrolimus (target whole blood level 10 to 12 ng/ml).
Postoperative prophylaxis included IV broad spectrum (or according to donor bronchoalveolar lavage antibiogram) antibiotics, IV acyclovir (5 mg/kg TID) and, in case of donor/recipient cytomegalo-virus (CMV) mismatch, IV gancyclovir (5 mg/kg BID) until postop day 7. Thereafter, antiviral drugs were switched to the oral form to be continued until 3 months postop, antibiotics were only continued if clinically indicated. All patients inhaled nebulized amphotericin B (10 mg) and tobramycin (40 mg) 3x per day until discharge. Postoperative monitoring of pulmonary function consisted of routine chest roentgenogram, blood gas analysis, and clinical examination and intermittent body plethysmography until patients were discharged from the hospital. Thereafter, patients were seen in our transplant clinics on a fixed schedule (weekly until 2 months postop, every 2 weeks from 2 to 4 months postop, every 3 weeks from 4 to 6 months, thereafter 1x per month). A routine visit at our clinics included a body plethysmography, chest roentgenogram, physical examination, and blood tests. Bronchoscopy with bronchoalveolar lavage (BAL) and occasional transbronchial biopsy (TBBx) were only performed when indicated by pathological chest roentgenogram or by a drop in expiratory pulmonary function of more than 10%. Patients were instructed to use their home spirometer daily at a fixed time, for example when taking their cyclosporine, and to transfer those data telemetrically.
Received data were checked daily by the transplant physician, and the patient was called into the hospital for a thorough evaluation if a drop of more than 10% was observed in FEV1 or MEF 25 to 75.
Results
All patients learned to use the unit during their postoperative stay in our hospital and were able to apply the system at home correctly. In only 1 case, data transferal was initially not successful due to an erroneously set phone number in the modem. A single lung recipient, who went for vacation to the Spanish island of Mallorca 12 months after his transplantation, was able to transfer his daily PFTs even from that remote place after reprogramming his modem to dial the international area code.
When values measured with the patients’ home spirometer were compared to those of the body plethysmography done during routine visits in our transplant clinic, satisfactory concordance of single values and short- as well as long-term trends were observed in almost all patients (Fig 3). Absolute values of routine FEV1 tended to be generally 10% to 20% lower on most patients’ home spirometers; the respective differences to the body plethysmography measurements, however, remained constant in each case throughout the observation period up to date.
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Four of those episodes were identified as acute rejection occurring in 2 patients. Three first episodes of rejection, diagnosed by exclusion of infection at the 12th, 18th, and 21st postoperative week, respectively, were successfully treated with IV methylprednisolone resulting in full functional recovery. Three weeks later, 1 of those patients experienced another drop in FEV1 (2.6 to 1.86 l/sec) due to recurrent rejection (confirmed by TBBx) and had to be admitted to the hospital. After switch to tacrolimus therapy, rejection resolved with a 90% recovery of function (FEV1 2.31 l/sec) and did not reoccur.
In 6 cases, bronchoscopy showed significant tracheo-bronchial mucosal erythema with purulent secretions; microbiological testing of BAL samples revealed significant bacterial colonization. Tested antibiotic treatment combined with contemporaneous inhalation of ß mimetic agents resolved infection and resulted in full functional recovery. Three of those 6 episodes occurred more than 2 years after transplantation in a heart-lung recipient. She is known to suffer from mild tracheal stenosis (30% luminal narrowing) since the 6th postoperative month. Recently, the tracheal stenosis increased to 60% which might cause significant reduction of airway clearance being the probable cause for her repeated pulmonary infection. She is therefore planned to undergo tracheal balloon dilatation, stenting or laser therapy.
In 5 cases, flu-like symptoms such as fever, arthralgia, and rhinitis were diagnosed at the time of deterioration of home PFTs. Since bronchoscopy showed only mild tracheal erethyma with no significant secretions, respiratory viral infection was assumed as the likely cause. Symptomatic therapy with acetyl cistein inhalation, prophylactic oral penicillin and nonsteroidal antiinflammatory drugs again resulted in relief of symptoms and full functional recovery within 5 to 10 days.
The 1 patient, who was not found to suffer from functional deterioration during his 12 month follow-up, is a 19-year-old man who had received a heart-lung transplantation for primary pulmonary hypertension in April 1996. Apart from one early episode of rejection followed by a CMV pneumonia, his postoperative course was uneventful. He received the telemetric system in January 1998. Since then he presented several periods of noncompliance during which he did not use the home spirometer nor did he show up to the transplant clinic. Recently, his pulmonary function was found to be unchanged, data collection, however is therefore incomplete and cannot be taken as a representative sample.
Comment
Acute rejection and infection episodes remain the most important cause of morbidity and mortality after lung transplantation [1]. Accurate differential diagnosis and specific treatment for any acute graft dysfunction are therefore a key feature in the posttransplant care. Apart from thorough examinations during scheduled visits at the transplant clinics, recognition of impending illness depends primarily on the patient’s subjective feelings, such as experiencing shortness of breath, fatigue, or pyrexia. In most cases, those symptoms appear only at a progressed stage of disease which often requires in-hospital treatment. Spirometry is obviously a much more sensitive parameter for the recognition of developing pulmonary pathology. Decreases in FEV1, vital capacity, and diffusion capacity were all found to have a sensitivity of over 80% to detect acute rejection or infection episodes especially early after transplantation [3]. Specificity of those values, however, is low since their deterioration does not allow recognition of the etiology of pulmonary dysfunction [4, 5]. Although other tests, such as chest roentgenogram or perfusion scanning, have also been found highly sensitive to detect pulmonary pathologies [6, 7], an inherent advantage of the FEV1 test is the ability to perform it at home using portable flowmeters like the AM1 of the tested telemetric system. Telemetric daily monitoring holds the further advantage that detection of any developing pulmonary dysfunction does not depend on random diagnosis during scheduled visits, but should allow earlier diagnosis.
The tested system in this study indeed proved to be very useful. All patients found it easy to use and some managed to transfer data even from remote places. Despite a systematic error of up to 20% that seemed to prevail in lower range measurements, its accuracy was still found to be satisfactory. In those cases where body plethysmography and home spirometry showed different values, the overall trends of both curves, ie, the sensitivity to detect significant changes of PFTs, were still identical in both methods. In all cases, the deterioration of home PFTs was related to significant pulmonary pathology as confirmed by thorough examination and bronchoscopy. Since rehospitalization was necessary in only 1 case of recurrent rejection, and full recovery of function could be achieved in all other cases on an outpatient basis, one might postulate that diagnoses occurred indeed at an early stage. Even though only a small number of patients was included for a relatively short average follow-up of less than 12 months, a significant number of beginning graft dysfunction were diagnosed which would have been missed or at least diagnosed at a later stage. This indicates the usefulness of the telemetric monitoring, in particular in those patients late after transplantation with large intervals between routine visits in the transplant clinic.
Recently, data are accumulating that increased numbers of acute rejection episodes and pulmonary CMV infection correlate with the development of obliterative bronchiolitis the main cause of morbidity and mortality in long-term survivors after lung transplantation [1]. This is most likely due to the fact that the pulmonary graft, being denervated, without reestablished bronchial circulation and disturbed lymphatic drainage, easily suffers irreversible parenchymal damage when exposed to infection or rejection [8]. The positive experience with the telemetric system therefore stimulates the hope that earlier diagnosis and prompt treatment might reduce the quantity of amounting chronic graft dysfunction. Although this remains pure speculation, graphic plotting of expiratory volumes as executed by the AMOS software clearly holds the advantage that even a slow, but continuous decrease that often occurs with developing OB, will become readily visible and help to diagnose functional loss at an earlier stage. So far, reports about treatment of OB indicate that only if diagnosed early, stopping or reversing of the process seems possible [9].
In summary, telemetric monitoring of pulmonary function in lung transplant recipients proved to be a reliable and useful tool for the early diagnosis and treatment of acute graft dysfunction regardless of its etiology. It is clearly complementary to the routine visits at the transplant clinic and might therefore provide additional safety for the lung transplant recipient. Any further impact on the long-term outcome after lung transplantation requires further studies with a longer follow-up.
References
This article has been cited by other articles:
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  B. MORLION, C. KNOOP, M. PAIVA, and M. ESTENNE Internet-based Home Monitoring of Pulmonary Function after Lung Transplantation Am. J. Respir. Crit. Care Med., March 1, 2002; 165(5): 694 - 697. [Abstract] [Full Text] [PDF]
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