Predictive value of automated oxygen saturation analysis for the diagnosis and treatment of obstructive sleep apnoea in a home-based setting

BACKGROUND: A portable monitor for the automated analysis of episodic nocturnal oxygen saturation or SpO(2) (the Remmers Sleep Recorder, RSR) has been proposed for the diagnosis of obstructive sleep apnoea-hypopnoea (OSAH). A study was undertaken to compare the diagnostic performance of automated analysis with the manual scoring of polygraphic data by a more comprehensive respiratory monitor (the Suzanne recorder) used simultaneously in their intended home environment. METHODS: The respiratory disturbance indexes of the two monitors were compared in 94 consecutive adult patients suspected of having OSAH and who were deemed eligible for home-based investigation. RESULTS: The RSR overestimated the number of respiratory events associated with a >or=4% fall in SpO(2) by 13% (p<0.005) but underestimated the number of apnoeas and hypopnoeas defined on the basis of respiratory variables alone or their association with a >or=4% fall in SpO(2) or autonomic arousals by 38-48% (p<0.0001). In addition to these significant biases, the limits of agreement in all instances were wide, indicating a poor concurrence between the two monitors. CONCLUSION: The automated analysis of SpO(2) with the RSR cannot be substituted for the manual scoring of polygraphic data with the more comprehensive respiratory monitor in the diagnosis of OSAH in an ambulatory home-based setting.     

Postoperative episodic oxygen desaturation in the sleep apnoea syndrome

We describe a patient with sleep apnoea syndrome who showed severe episodic hypoxaemia in the late postoperative period. The sleep apnoea syndrome should be studied further to evaluate its significance as a surgical risk factor.     

The impact of postoperative nasal packing on sleep-disordered breathing and nocturnal oxygen saturation in patients with obstructive sleep apnea syndrome

Nasal septum surgery is frequently performed to establish a functional nasal airway. In these patients obstructive sleep apnea syndrome (OSAS) is frequently present. Although patients with OSAS are at increased risk for hypoxemia, the impact of postoperative nasal packing (PNP) on sleep-disordered breathing and oxygen desaturations in patients with OSAS is unknown. We consecutively investigated 40 patients undergoing endonasal surgery receiving PNP. Fifteen of these patients had previously diagnosed OSAS (Group 2) and 25 did not (Group 1). In the control group, 12 healthy patients underwent elective ear or neck surgery without PNP. During the preoperative and postoperative nights, we continuously measured oronasal flow, thoracoabdominal movements, and oxygen saturation. We calculated the apnea-hypopnea index (AHI) and the oxygen-desaturation index (ODI). Compared with the preoperative values, after the operation, neither AHI nor ODI changed in the control group. In contrast, in Group 1, AHI (from 11 [5-19] to 37 [22-49]) and ODI (from 4 [2-8] to 13 [6-21]) significantly increased (P < 0.05), whereas in Group 2, only AHI significantly increased (from 14 [10-21] to 39 [26-50]); ODI remained similar (13 [8-27] versus 11 [4-37]). Because ODI did not increase in patients with OSAS and PNP who received postoperative oxygen overnight, postoperative intensive care monitoring might not be necessary on a routine basis for all patients with PNP and OSAS.     

Upper airways sarcoidosis presenting as obstructive sleep apnoea

Sarcoidosis may present in a number of different ways,affecting many organ systems. The case history is presented of a 32year old woman who presented with symptoms of severe obstructive sleepapnoea (OSA) due to infiltration of the upper airway by sarcoidosis. Toour knowledge this presentation of sarcoidosis has not previously been described.

     

Late postoperative nocturnal dips in oxygen saturation in patients undergoing major abdominal vascular surgery

Twenty-four patients (23 male) who presented for aortic reconstructive surgery were studied with pulse oximetry on a pre-operative night and during the first five postoperative nights. Patients with five or more dips in oxygen saturation of greater than 4% (with a prompt recovery back toward baseline of 3% or more) per hour of monitoring were classified as having a significant abnormality of respiration. Pre-operatively, four of 24 patients (17%) demonstrated such an abnormality. Postoperatively, 12 patients (50%) met these criteria on at least one of the first five postoperative nights and six of these had two or more nights with severe episodic hypoxaemia. Frequent severe episodic dips in arterial oxygen saturation (to less than 85% saturation) occurred in the late postoperative period at a time when oxygen therapy would usually have been discontinued. Pre-operative overnight pulse oximetry studies fail to predict the development of abnormal respiratory patterns in the postoperative period in the majority of patients.     

Failure of the tourniquet-twitch test as a diagnostic or screening test for malignant hyperthermia

We have performed the tourniquet-twitch test of Roberts and Ryan in normal and in malignant hyperthermia (MH) patients and relatives. This test measures the ratio of electrically induced thumb twitches noted after 10 min of ischemia with those noted immediately prior to the ischemia. We found no significant differences in this ratio between normal subjects and those who have had MH reactions, or relatives of such individuals. Furthermore, we have observed no significant differences in tourniquet-twitch ratios between those with normal caffeine-halothane contractures and persons with caffeine-halothane contractures tests positive for MH. These findings do not agree with those of Roberts and Ryan, who reported that tourniquet-twitch ratios were higher in MH patients than in normal patients. We have, however, determined that subjects with tourniquet-twitch ratios greater than or equal to 1.8 are substantially younger than those with tourniquet-twitch ratios less than or equal to 1.0. Therefore we do not believe that the tourniquet-twitch test is useful as a diagnostic, or even as a screening test for MH.     

Uvulopalatorrhaphy in a case of obstructive sleep apnoea.

A reversible uvulopalatorrhaphy is reported in a case of obstructive sleep apnoea. The patient had an abnormally long uvula but no skeletal abnormality.     

Effects of nocturnal oxygen therapy on sleep apnea syndrome in peritoneal dialysis patients

Sleep apnea syndrome (SAS) is common in patients with end-stage renal disease (ESRD). Although the treatment of choice is continuous positive airway pressure (CPAP) particularly for obstructive SAS, long-term compliance is not satisfactory. We investigated the effectiveness of nocturnal oxygen therapy on sleep apnea and autonomic nervous dysfunction in peritoneal dialysis (PD) patients with SAS. METHODS: 40 patients on PD in our outpatient clinic were screened for SAS by pulse oximetry. We set the indication for nocturnal oxygen therapy at 4% oxygen desaturation index (4% ODI; defined as the number of falls of oxygen saturation > or = 4% per hour) > 5 or average nocturnal saturation < 95%. For SAS patients, 2 l per minute of oxygen was given during sleep and polysomnography was performed before and 1 month after oxygen administration. The heart rate variability was analyzed to assess autonomic nervous activity. RESULTS: 23 patients fulfilled the indication for oxygen therapy and 11 patients agreed to participate in the study. After oxygen therapy, the apnea-hypopnea index (AHI) and the frequencies of hypopnea and central apnea were significantly decreased (AHI: from 31.1 +/- 8.8 to 12.7 +/- 8.5, p < 0.01; hypopnea: from 19.5 +/- 4.3 to 3.5 +/- 3.2, p < 0.01; central apnea: from 4.0 +/- 4.0 to 0.8 +/- 1.2, p < 0.05), whereas that of obstructive apnea was not changed. An analysis of heart rate variability showed that oxygen therapy did not alter autonomic activity after 1 month of oxygen therapy. CONCLUSIONS: Nocturnal oxygen therapy decreases hypopnea and central apnea in PD patients with SAS. Nocturnal oxygen therapy may be useful for the treatment of SAS in PD patients, particularly when central apnea and hypopnea are predominant.     

Usefulness of regional cerebral oxygen saturation monitoring in balloon test occlusion

PURPOSE: Recently, temporary balloon test occlusion (BTO) of the internal carotid artery (IC) has become a well accepted procedure for preoperative evaluation of patients with IC large aneurysms. However, it might be dangerous to move patients fitted with a balloon catheter to the room for single-photon emission computed tomography (SPECT). We attempted to clarify the usefulness of regional cerebral oxygen saturation (rSO2) monitoring during BTO, comparing cerebral blood flow (CBF) obtained from SPECT. MATERIALS AND METHODS: Eight patients with an IC large aneurysm underwent BTO with rSO2 monitoring. Regions of interest in the SPECT were defined in the area below the rSO2 sensor of each hemisphere. Correlations among rSO2, CBF, stump pressure and appearance of symptoms were discussed. RESULTS: The rSO2 significantly reduced during BTO (74.1 +/- 1.2 to 60.4 +/- 2.7%, p < 0.001). The individual decreases in rSO2 correlated with decreases of CBF from SPECT (r = 0.966, P < 0.001). Four patients with deltarSO2 (baseline rSO2 - rSO2 during IC occlusion) less than 12 points had no symptoms, but 4 patients with deltarSO2 more than 14 points had some symptoms. The stump pressure had no correlation with CBF and rSO2. CONCLUSIONS: The rSO2 significantly correlated with CBF from SPECT and related with appearance of symptoms. Our results revealed that rSO2 monitoring was useful in BTO, and SPECT could be skipped in some cases to determine the strategies for treatment of IC large aneurysms.     

Patient's experience of treatment for sleep apnoea with a mandibular advancement splint

Background and aimsObstructive sleep apnoea (OSA) is a well recognised clinical disorder in which there is narrowing and repeated collapse of the upper airway during sleep resulting in the cessation of breathing. Patients with mild to moderate sleep apnoea are often provided with mandibular advancement splint (MAS) therapy as a form of first line or definitive treatment. The aims of this audit were to evaluate patient satisfaction and success of MAS therapy.Methods93 patients diagnosed with sleep apnoea and suitable for a splint were recruited prospectively at Queen Victoria Hospital, East Grinstead between January 2009 and October 2010. A patient satisfaction questionnaire was developed by health professionals involved in the care of patients with sleep apnoea and assessed for face and content validity and reliability. Participants completed the questionnaire six weeks after the splint was fitted.Results44% who previously experienced snoring now reported no snoring and 47% reported less snoring since wearing the MAS appliance. 69% reported complete resolution of sleep apnoea symptoms. 37% experienced aching teeth and 33% experienced having a dry throat when wearing the appliance. 86% of sleeping partners felt that their quality of sleep was improved following their partners treatment.ConclusionsThe standards set for each criteria in this audit were met. MAS treatment has a key role to play in the management of obstructive sleep apnoea with high rates of patient satisfaction and the majority of patients partners reporting a significant improvement in their own and their partners sleep quality.     

Uricult trio as a screening test for bacteriuria in pregnancy.

OBJECTIVE: To establish the effectiveness in an indigent urban population of Uricult Trio as a screening test for asymptomatic bacteriuria in pregnancy and in diagnosing urinary tract infections (UTI) in symptomatic pregnant women. Likelihood ratios were established for positive and negative Uricult Trio test results. SUBJECTS: Two populations of patients from the Pretoria region were involved: (i) asymptomatic pregnant women attending the antenatal clinic for the first time or presenting in labour; and (ii) pregnant women with symptoms suggestive of UTI. METHOD: A midstream urine specimen was collected from the two populations of patients, plated onto the Uricult Trio and sent to the laboratory for culture. RESULTS: The prevalence of asymptomatic bacteriuria in this population was 23%, and for women with symptoms suggestive of UTI, 29%. The likelihood ratios for a positive test were 1.8 and 1.5 for asymptomatic and symptomatic patients respectively. The likelihood ratios for a negative test were 0.35 and 0.44 for asymptomatic and symptomatic patients respectively. Escherichia coli was the causative agent in 36% of cases. CONCLUSION: Uricult Trio is not effective as a screening test for asymptomatic bacteriuria in pregnancy or for diagnosing UTIs in women with symptoms suggestive of infection.     

Critical values of hematocrit and mixed venous oxygen saturation as parameters for a safe cardiopulmonary bypass

Objective: Mixed venous oxygen saturation (SvO₂) is high despite a low hematocrit implies that the relationship between oxygen demand and supply is in a safe state. This study was sought to determine the critical values for hematocrit and SvO₂ for safe cardiopulmonary bypass. Methods: Study 1: To evaluate the limit of hemodilution without cardiopulmonary bypass, normovolemic hemodilution with Dextran 40 (10%) was performed in 14 rabbits. SvO₂ was monitored from the right atrium, and the hemodynamic parameters were recorded continuously. Study 2: To determine the critical values for hematocrit and SvO₂ during cardiopulmonary bypass, normothermic and hypothermic cardiopulmonary bypass were performed in 13 rabbits and hemodynamic parameters were corrected. Results: Study 1: The heart rate decreased to unsafe levels abruptly, when the SvO₂ was ≦43% or the hematocrit was ≦10%. The lactate concentration increased when the SvO₂ was ≦46% or the hematocrit was ≦12%. Study 2: When the hematocrit was ≦12%, the SvO₂ decreased gradually. Even when weaning was possible, the animals with a hematocrit ≦12% collapsed hemodynamically within 40 minutes after cardiopulmonary bypass. Most of the animals could not be weaned from cardiopulmonary bypass during either normothermic or hypothermic cardiopulmonary bypass when the SvO₂ was ≦46%. Conclusions: Continuous monitoring of hematocrit and SvO₂ provides evidence-based guidelines for safe cardiopulmonary bypass. The lower limits of critical range for a safer cardiopulmonary bypass are hematocrit of 12% and SvO₂ of 46%.     

Model for investigating snorers with suspected sleep apnoea.

BACKGROUND: Overnight polysomnography is expensive and time consuming. An approach based on a logistic regression model and overnight pulse oximetry has been developed to determine which of the snorers referred to our sleep laboratory need polysomnography. METHODS: The variables entered in the regression model were derived from questionnaires completed by 95 habitual snorers and 89 patients with obstructive sleep apnoea. The resulting regression equation included weight, height, sex, witnessed episodes of apnoea, and reports of falling asleep when reading. This prediction equation was applied to a sample of 116 consecutive patients referred for investigation of heavy snoring. Pulse oximetry data on the 116 test subjects were obtained during polysomnography and analysed separately. Pulse oximetry was judged to indicate obstructive sleep apnoea when it showed cyclic oscillations of oxyhaemoglobin saturation or heart rate, or both, for more than 30 minutes during the study night. RESULTS: A cut off probability of 0.31 gave the prediction model a sensitivity of 94% to predict an apnoea-hypopnoea index above 10, with a specificity of 45%. When this cutoff point was used to predict an apnoea-hypopnoea index of over 20 sensitivity was 95% and specificity 41%. Combined with oximetry our regression model had a sensitivity of 100% for predicting an apnoea-hypopnoea index of more than 10. On the other hand, all patients with negative results from oximetry and a probability value below 0.31 had an apnoea-hypopnoea index lower than 10 according to polysomnography. CONCLUSIONS: It is concluded that snorers with negative results from oximetry classified as not having obstructive sleep apnoea according to this model do not need polysomnography.     

Use of home sleep studies for diagnosis of the sleep apnoea/hypopnoea syndrome

BACKGROUND: A study was undertaken to test the hypothesis that unsupervised domiciliary limited sleep studies do not impair the accuracy of diagnosis when used to investigate the sleep apnoea/hypopnoea syndrome (SAHS) and can be cheaper than laboratory polysomnography. METHODS: For validation, 23 subjects with suspected SAHS underwent laboratory polysomnography and a home study (EdenTec 3711) on successive nights. All subjects with > 15 apnoeas + hypopnoeas (A + H)/hour on polysomnography showed > 30 A + H/hour on their home study. Thereafter, in a prospective trial 150 subjects had a home study as the initial investigation and studies showing > 30 events/hour were regarded as diagnostic of SAHS. Those showing fewer events were investigated with polysomnography if necessary. Time to treatment, outcome, and costs of this protocol were compared with those of 75 patients investigated initially with polysomnography. RESULTS: Of the prospective trial subjects, 29% had > 30 A + H/hour and proceeded directly from home study to treatment; 15% without daytime sleepiness were not investigated further. Polysomnography was undertaken to establish a diagnosis in 56% of cases, including 18% whose home studies were unsuccessful. Compared with the 75 control patients, this protocol gave a diagnosis faster (median 18 (range 0-221) versus 47 (0-227) days, p < 0.001) and more cheaply (mean (SD) 164 pounds (104) versus 210 pounds (0), p < 0.001). The proportions offered CPAP (61% versus 67%) and subsequent objective CPAP usage (mean 4.7 (2.4) versus 5.0 (2.4) hours/night) were not different. CONCLUSIONS: Use of home sleep studies has benefits in time and cost. For diagnostic reliability a further sleep study was required in 56% of cases.


     

Preoperative nocturnal desaturations as a risk factor for late postoperative nocturnal desaturations

Severe postoperative hypoxaemia during sleep may increase the risk of postoperative cardiovascular complications. We hypothesized that the severity of hypoxic episodes after surgery are related to the presence of preoperative sleep-disordered breathing (SDB). We tested this hypothesis in a multicentre study designed to elucidate the major risk factors for development of postoperative nocturnal desaturations. We performed overnight oximetry before operation and for one night between the second and fourth day after operation in 80 patients undergoing major surgery. We calculated oximetry variables such as oxygen desaturation index (ODI), defined as the number of oxygen desaturations exceeding 4% below baseline, percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value. After operation, although the change in ODI was not significant (P = 0.34), deterioration in CT90 and lowest SpO2 values were significant (P = 0.036 and P = 0.007, respectively). Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative hypoxaemia and apnoea witnessed by others were highly correlated with postoperative hypoxaemia.