Eur Arch Otorhinolaryngol (2005) 262: 241–245 DOI 10.1007/s00405-004-0792-2

MISCELLANEOUS

Britt Oeverland Æ Harriet Akre Æ Kari J. Kvaerner Olav Skatvedt

Patient discomfort in polysomnography with esophageal pressure measurements

Received: 5 December 2003 / Accepted: 12 March 2004 / Published online: 30 April 2004 Ó Springer-Verlag 2004

Abstract The reference method for measuring respiratory effort and for differentiating between obstructive and central apneas in the diagnosis of sleep-related breathing disorders is overnight monitoring of esophageal pressure. Despite this being the reference method, it is not widely used because it is considered invasive and uncomfortable for the patients. The aim of this study was to assess patient discomfort and insertion difficulty when using an esophageal catheter during polysomnography. We have performed a prospective questionnaire-based clinical study in 799 consecutive patients where polysomnography with an esophageal catheter was routinely performed in the diagnosis of sleep-related breathing disorders. The main outcome measures were the catheter-related discomfort experienced by the patient and difficulty of catheter insertion reported by the sleep technician. Ninety-six percent of the patients accepted the insertion of the catheter, and most of the patients considered it acceptable to sleep with the catheter. Correspondingly, in most of the patients, the catheter was easily inserted, and there were difficulties in only a few patients. Specifically, no complications or side effects were reported when using the catheter. To optimize the diagnosis of sleep-related breathing disorders, an esophageal sensor catheter can be used during polysomnography, without causing major patient discomfort. Keywords Polysomnography Æ Apnea Æ Hypopnea Æ Sleep-related breathing disorders

B. Oeverland Æ H. Akre Æ K. J. Kvaerner Æ O. Skatvedt SRBD Unit of the Department of Otorhinolaryngology, Ullevaal University Hospital, Oslo, Norway B. Oeverland (&) Æ H. Akre Æ K. J. Kvaerner Æ O. Skatvedt The Sleep Clinic Omnia, Frederik Stangs gt. 11-13, 0264 Oslo, Norway E-mail: [email protected] Tel.: +47-22-125000 Fax: +47-22-124999

Introduction Sleep-related breathing disorders (SRBD) are associated with increased mortality and morbidity, such as hypertension, myocardial infarction and stroke [12, 16, 22, 23, 24]. Also, automobile accidents are over reported in patients suffering from obstructive sleep apnea [11]. Because hypertension occurs as a result of long-term sleep apnea and nocturnal hypoxemia [30], correct diagnosis and early treatment is important. The diagnosis of SRBDs is based on the registration of obstructed breathing events during sleep. These events may include obstructive hypopneas, apneas or respiratory effort-related arousals. The reference standard for measuring respiratory effort and to differentiate between obstructive and central apneas is overnight monitoring of esophageal pressure [1, 5, 9]. The diagnosis of upper airway resistance syndrome (UARS), which yields 10-15% of the patients referred for SRBD diagnosis [10], is based on these esophageal pressure measurements. In our department, polysomnography is routinely performed with an esophageal microchip sensor catheter for continuous pressure and flow measurements. The catheter contains several pressure transducers, which can also function as internal thermistors. Therefore, when using the catheter in addition to the esophageal measurements, we also obtain pressure and airflow measurements from the upper airways. The upper airway pressure measurements can be used to select patients who will benefit from surgery [24, 25, 29], while the internal thermistors previously have been shown to be reliable in diagnosing respiratory disturbances [2] and to be able to differentiate between nose and mouth breathing [3]. In the literature, the measurement of esophageal pressure is often referred to as an invasive method, uncomfortable for the patients and difficult to incorporate into routine sleep studies [4, 17, 18, 28]. This is contradictory to our experience with this method. Pressure measurements with an esophageal catheter

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have been used routinely during polysomnography in our department for the last 7 years. On average, we have performed 700 registrations each year and experienced few problems with this practice. There seems also to be a widespread concern of disturbing sleep when doing esophageal measurements. This was a problem earlier with the balloon catheter [6, 30], but when using thinner catheters such as the water-filled catheter or this microchip catheter, it has been demonstrated that sleep is not significantly disturbed [7, 27]. The purpose of the present study was to investigate the patients’ subjective experiences when a microchip sensor catheter was used in the esophagus during polysomnography and whether there are difficulties involved with insertion of the catheter.

Materials and methods A prospective questionnaire-based study was performed in 799 consecutive patients. The source population included all patients referred to Ullevaal University Hospital for the diagnosis of sleep disorders during a 1-year period from 1998–1999. In all patients, polysomnography with pressure and flow measurements with an esophageal catheter was routinely performed [26]. Since this is part of the investigative procedure for diagnosing SRBD at our department, informed consent was not obtained. Sixty-three patients were excluded from the study, 33 due to insufficient questionnaire information, 22 due to catheter insertion refusal and 8 due to interruption of the esophageal catheter registrations during the night. These patients were comparable in terms of age, gender, education level and BMI with the rest of the population, using unpaired t-tests.

The esophageal catheter (Camtech, Sandvika, Norway) is a silicone tube, 1.9 mm in diameter and containing three proximally located combined flow and pressure sensors and one distally located pressure sensor. The most proximal sensor was placed in the epipharynx, the second in the oropharynx immediately caudal to the posterior border of the soft palate, and the third in the hypopharynx, while the fourth pressure transducer was positioned in the esophagus 12 cm caudal to the third combined sensor. The sensor catheter was inserted transnasally into the esophagus by the sleep technicians, who routinely are recruited among medical students. The subsequent morning, the patients received selfadministered questionnaires on the preceding PSG with the esophageal catheter, subjective nasal obstruction and catheter insertion discomfort. The sleep technicians reported catheter insertion difficulty and the use of local anesthetics (lidocain hydrochloride 10 mg/dose) during catheter insertion. Age, gender, body mass index (BMI) and education level were recorded in each patient. The distribution is presented in Table 1. We used a visual analogue scale to assess the patients’ perception of sleeping with the catheter, their subjective nasal obstruction and the technicians difficulties with insertion of the catheter. Patients’ perception of sleeping with the catheter was scaled from OK (0) to unacceptable (10), their subjective nasal obstruction from open (0) to obstructed (10) and difficulties with insertion of the catheter from easy (0) to difficult (10). We calculated the mean patient discomfort in each group and used an unpaired t-test for comparison between two groups and one-way analysis of variance for comparison among more than two groups. The analysis was performed using SPSS 10.0.

Table 1 Mean patient discomfort in the different groups. Numbers in parenthesis indicate missing data

Age (1) Gender Education level (83) Body mass index (8) Subjective nasal stenosis (9)

Difficulties with catheter insertion (11)

Oral or nasal anaesthetics (3) Previous PSG with catheter (8)

<45 45–54 >54 Male Female <12 years 12–15 years >15 years <25 25–30 >30 0–2.5 2.5–5 5–7.5 7.5–10 0–2.5 2.5–5 5–7.5 7.5–10 Yes No Yes No

n

Mean

SD

P

329 205 201 598 138 351 217 85 184 382 162 309 237 138 43 538 138 33 16 343 390 202 526

3.1 2.8 2.8 2.9 2.9 2.8 3.1 2.9 3.1 2.9 2.8 2.5 2.9 3.1 4.5 2.9 3.0 2.8 3.8 3.0 2.7 2.8 2.9

2.3 2.4 2.3 2.3 2.4 2.3 2.3 2.2 2.4 2.2 2.2 2.2 2.1 2.2 3.1 2.3 2.4 1.8 2.5 2.4 2.2 2.2 2.3

0.244 0.843 0.221 0.276 <0.001

0.407

0.185 0.661

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Results

Discussion

Of the study population, 19% were females and 81% males. Mean age was 47 years (range 17 to 82) and body mass index 28.0 (range 18 to 64). The characteristics of the study population are given in Table 1. Most of the patients accepted the insertion of the catheter (96%). Among the patients who failed to cooperate, 3% refused to try to insert the catheter and 1% removed it during the night. These patients did not differ significantly from the rest of the population in terms of age, gender, education level or BMI. Two hundred eighteen of the patients included in this study had previous experience of PSG with an esophageal catheter; only 2.8% of these patients refused catheter insertion the second time. The distribution of the marks on the visual analogue scale for the patients’ discomfort and the sleep technicians’ insertion difficulty respectively are shown in Fig. 1. When regarding the patients’ answers concerning catheter discomfort, as many as 49% marked the lowest 2 cm, and 37% from 2 to 5 cm. Only 2.4% marked the uppermost 2 cm, while 12% marked between 5 and 8 cm. Seventy percent of the sleep technicians marked the lowest 2 cm closest to the alternative easy to insert; 24% marked from 2 to 5 cm, and 5% between 5 and 6 cm. Only 1.8% marked in the uppermost part nearest to the alternative difficult to insert the catheter. We calculated the mean patient discomfort in the different groups and used t-tests for comparisons between them (Table 1). Subjective feeling of nasal stenosis was the only factor where there was a difference between the groups. The patients with severe subjective nasal stenosis before catheter insertion had a significantly higher experience of discomfort when using the catheter.

In our prospective clinical study, we found that both catheter discomfort and insertion difficulty is uncommon in pressure and flow measurements in the upper airways during polysomnography. Further, there was no significant difference between the different groups, except for the group with severe subjective nasal stenosis. This group has a higher experience of discomfort with the catheter. Specifically, no complications or side effects were reported when using the catheter. Local anesthetics were used in almost half of the patients. This is probably due to different practice and experience among the sleep technicians, and not due to discomfort among the patients. Although pressure measurements in the esophagus is the reference method to differentiate between the different types of apneas and hypopneas [1] and to diagnose upper airway resistance [1, 4, 5, 9], the method is considered by many as an unpleasant, invasive procedure that is difficult to incorporate into routine sleep studies [4, 17, 18, 28]. In the present study, however, no complications or side effects were reported, and very few patients found the procedure uncomfortable. On the contrary, patient compliance was high, there were few complaints from patients and sleep technicians and the sensor was easily inserted without discomfort. Accordingly, the placement of the internal thermistors is usually an uncomplicated procedure. These results are in accordance with our experience at Ullevaal University Hospital where we have been using the catheter for 7 years. During these years, few problems have been reported, and there have been few complaints from the patients. Our findings are contrary to the findings of Hessel et al. [13] when they were investigating patients’ acceptance of a flextube for the diagnosis of sleep apnea. Only 47% of their patients completed a whole night of registration with the flextube, in comparison to a success rate of 96% in our patients. This may be due to the size and material with which the two tubes are made. The catheter

Fig. 1 Frequency distribution of patient reported microchip sensor catheter discomfort graded from 0 (OK) to 10 (unacceptable) and of technician reported microchip sensor catheter insertion difficulty graded from 0 (easy) to 10 (difficult)

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we use is only 1.9 mm in diameter, which is less than half the size of the flextube. It is also made of a fairly soft silicon type, and the shape of the tube is slightly curved in order to make it more comfortable to use. These findings are also in accordance with how these patients often are diagnosed at other hospitals and sleep units in Norway. The esophageal catheter is an integral part of two different portable respiratory recording devices that are in regular use at several hospitals and sleep units. These recording devices are often used for home monitoring, and there are few associated problems, even when the patient leaves the hospital with the catheter in place. When using the esophageal catheter, one acquires valuable additional information on esophageal measurements. The pressure measurements in the pharynx allow identification of the obstruction level in sleep apnea patients, and thus helps selecting patients who will benefit from surgery [24, 25, 29]. CPAP is still the most efficient treatment for sleep apnea, but has low compliance in some patients. Because of the associated mortality and morbidity, it is of great importance to treat patients even if they do not tolerate CPAP. For some, surgery to the upper airways is an attractive option if the obstruction level can be identified. Oronasal airflow recording by external thermistors is widely used, although technical sensor displacements and flow tracing difficulties have caused its specificity for differentiating between normal and reduced airflow to be questioned [20]. In particular, the scoring of hypopnea reports low reproducibility [20, 25]. The internal flow thermistors are almost as reliable as the pneumotachograph for diagnosing hypopneas [2], which is particularly valuable for increasing accuracy in the diagnosis of sleep-related breathing disorders [8]. Even without the esophageal catheter, quite a few patients are uncomfortable undergoing polysomnography. In the diagnosis of sleep disorders requiring followups with polysomnography, dropouts commonly occur. The reported lack of follow-up varies from 10 to 50% [15, 19, 21]. Subsequently, if patients hesitate to undergo another polysomnography, it is important that an accurate diagnosis is established at once using high specificity diagnostic equipment. The present prospective clinical study allows a valid estimation of patient discomfort and insertion difficulty, but there may be some limitations. Patient discomfort may have been underestimated. Due to months of waiting prior to investigation, the patients may have been more disposed to accept discomfort and complain less. Even though the patients are strongly recommended to use the catheter, they are allowed to carry out the polysomnography without the catheter. Further, the analyses are not controlled for the experience of the sleep technicians’ different practices. The varying practice among the medical students participating as sleep technicians may introduce a non-differential bias that most likely does not significantly influence the results.

In conclusion, no complications or side effects were reported. Patient discomfort and insertion difficulties were uncommon. Further, the only factor that has a significant influence on patient discomfort is subjective nasal stenosis. We recommend routine polysomnography with internal pressure and flow measurement to establish an accurate diagnosis. Acknowledgements The authors wish to thank I.W.S. Mair for assistance with the final version of the manuscript.

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