The severity of sleep hypoventilation in stable chronic obstructive pulmonary disease.

PURPOSE: An increase in PaCO2 is the element that defines sleep hypoventilation (SH). We queried if patients with SH, and those with PaCO2 increases during sleep for shorter time periods than SH (shamSH) differed from the patients without SH (noSH) in other ways. METHODS: This was a retrospective re-analysis of data from 100 stable inpatients with COPD with and without chronic hypercapnic respiratory failure. COPD was defined by criteria of the Global initiative for Chronic Obstructive Lung Disease (GOLD). For this study, SH was defined by an increase in PaCO2 ≥ 1.33 kPa to a value exceeding 6.7 kPa for ≥ 10 min (≥ 20 epochs of 30 s). Patients fulfilling the increase in PaCO2 for less than 10 min (1-19 epochs) were designated shamSH. All patients had daytime arterial blood gases, lung function tests, and polysomnography (PSG) with transcutaneous CO2 (PtcCO2). RESULTS: Of 100 patients, 25 had PtcCO2 increase ≥ 1.33 kPa. One never exceeded 6.7 kPa, 15 had SH, and 9 shamSH. SH and shamSH patients had extra CO2 load (= PtcCO2*time) both during and between the SH periods compared to the noSH group, the SH group more than the shamSH group. CONCLUSION: Using CO2 load as a measure of severity of sleep hypoventilation, SH patients have worse hypoventilation than the shamSH. Both shamSH and SH groups have extra CO2 load during and between SH periods, indicating that the SH/shamSH patients may represent a separate group of true hypoventilators during sleep.

Zopiclone effects on breathing at sleep in stable chronic obstructive pulmonary disease.

PURPOSE: More than half of patients with chronic obstructive pulmonary disease (COPD) experiences sleep-related problems and about one fourth uses hypnotics regularly. We explored what the effect zopiclone, a commonly used hypnotic, had on nocturnal gas exchange and the apnea/hypopnea frequency in stable COPD. METHODS: Randomized crossover study of 31 (ten males) inpatients at a pulmonary rehabilitation hospital, median age 64 years, of which 20 had a forced expiratory volume first second <50% of predicted. Subjects investigated in randomized order of either baseline sleep or intervention with 5 mg zopiclone by polysomnography including transcutaneous measurement of carbon dioxide pressure increased (ΔPtcCO2). RESULTS: Zopiclone increased the mean ΔPtcCO2 from baseline both in rapid eye movement (REM) sleep, non-REM sleep, and even in stage N0 (awake after sleep onset) with a mean (SD) of 0.25 (0.40) kPa, 0.22 (0.32) kPa, and 0.14 (0.27) kPa, respectively. Subjects with sleep hypoventilation as defined by the American Academy of Sleep Medicine increased from 6 subjects (19%) to 13 subjects (42%) (P = 0.020). REM sleep minimum oxygen saturation (minSpO2) did not change significantly from baseline median (interquartile range [IQR]) minSpO2 81.8 (12.1) % to zopiclone sleep median (IQR) minSpO2 80.0 (12.0) % (P = 0.766). Interestingly, zopiclone reduced the number of apneas/hypopneas per hour (AHI) in subjects with overlap (AHI ≥ 15) with a median difference (IQR) of -8.5 (7.8) (N = 11, P = 0.016). CONCLUSIONS: In stable COPD, zopiclone moderately increases the mean ΔPtcCO2 without changing minSpO2 at night and reduces AHI in overlap (COPD and obstructive sleep apnea) subjects.

Alcohol at bedtime induces minor changes in sleep stages and blood gases in stable chronic obstructive pulmonary disease.

PURPOSE/BACKGROUND: The purpose of this study is to explore the effect of a moderate dose of alcohol on sleep architecture and respiration in chronic obstructive pulmonary disease (COPD). Alcohol depresses both hypercapnic and hypoxic ventilatory drives in awake, normal individuals and reduces the amount of rapid eye movement (REM) sleep and oxygen saturation (SpO2) in sleeping COPD subjects. METHODS: Prospectively designed, open-label interventional study in a pulmonary rehabilitation hospital. Twenty-six (nine males) stable inpatients, median forced expiratory volume first second (FEV1) 40.5 % of predicted, median age 65 years, investigated by polysomnography including transcutaneous measurement of carbon dioxide pressure increase (ΔPtcCO2) in randomized order of either control sleep or intervention with 0.5 g of ethanol/kilogram bodyweight, taken orally immediately before lights off. RESULTS: Alcohol induced a mean increase (95 % confidence interval, [CI]) in the mean ΔPtcCO2 of 0.10 kPa (0.002-0.206, P = 0.047) and a mean decrease (CI) in the REM-sleep percentage of total sleep time (REM % of TST) of 3.1 % (0.2-6.0), (P = 0.020). Six subjects with apnea/hypopnea index (AHI) ≥15 had fewer apneas/hypopneas during alcohol versus control sleep (mean reduction of AHI 11 (1-20), P = 0.046). Alcohol-sleep changes in SpO2, but not in ΔPtcCO2, correlated with daytime arterial pressures of carbon dioxide (PaCO2) and oxygen (PaO2). CONCLUSION: Occasional use of a moderate, bedtime dose of alcohol has only minor respiratory depressant effects on the majority of COPD subjects, and in a minority even slightly improves respiration during sleep. However, caution is appropriate as this study is small and higher doses of alcohol may result in major respiratory depressive and additional negative health effects.

Sleep hypoventilation and daytime hypercapnia in stable chronic obstructive pulmonary disease.

PURPOSE: To explore the associations between sleep hypoventilation (SH) and daytime arterial pressures of carbon dioxide (PaCO2), sleep stages, and sleep apneas/hypopneas (AHI) in subjects with chronic obstructive pulmonary disease (COPD). SH has previously been found in COPD-subjects with chronic hypercapnic respiratory failure (CHRF) using supplementary oxygen (LTOT), and has been proposed as a possible predictor for CHRF. PATIENTS AND METHODS: A prospectively designed observational study in a pulmonary rehabilitation hospital of 100 (39 male) stable COPD inpatients with a mean forced expiratory volume in 1 second (FEV1) of 1.1 L (42% of predicted) and a mean age of 64 years, using polysomnography with transcutaneous measurement of carbon dioxide pressure increase (ΔPtcCO2). RESULTS: SH as defined by the American Academy of Sleep Medicine (AASM) was found in 15 of the subjects, seven of whom used LTOT. However, six had SH despite being normocapnic during the daytime (only one on LTOT). Subjects with SH had a greater ΔPtcCO2 increase from nonrapid eye movement (NREM) to rapid eye movement (REM) sleep stages compared to non-SH subjects (mean [standard deviation] between-groups difference =0.23(0.20) kPa, P<0.0005). Subjects with apnea/hypopnea index ≥15 (overlap, N=27) did not differ from those with COPD alone (AHI <5, N=25) in sleep ΔPtcCO2 or daytime PaCO2. A regression model with the variables FEV1, LTOT, and sleep maximum ΔPtcCO2 explained 56% of the variance in daytime PaCO2 (F(3, 94) =40.37, P<0.001). CONCLUSION: In stable COPD, SH as defined by the AASM was found both in normocapnic, non-LTOT subjects and in hypercapnic, LTOT-using subjects. Between-sleep-stage increase in ΔPtcCO2 was higher in subjects with SH. Overlap subjects did not differ from simple COPD subjects in sleep ΔPtcCO2 or daytime PaCO2.

Does excessive dynamic airway collapse have any impact on dynamic pulmonary function tests?

BACKGROUND: Excessive dynamic airway collapse (EDAC) represents pathologic obstruction, but the flow resistance it creates and the possible impact on pulmonary function tests is unclear. Our aims were to explore the flow resistance in a model, and in patients to relate observed EDAC to pulmonary function tests. METHODS: Model study: A garden hose was compressed from 1 side to simulate the posterior tracheal wall bulging into the lumen for 2 lengths, 3 and 12 cm, in 8 steps. Resistance was measured at each step for airflows 1 L/s through 9 L/s. Digital photos of the luminal area at each obstruction step were analyzed by a computer to estimate the cross-sectional area reduction and the corresponding shortest distance between the bulging (posterior) and the opposite (anterior) wall (AP-distance). Patient study: A total of 104 stable chronic obstructive pulmonary disease patients studied by pulmonary function tests and bronchoscopy. The tracheal obstruction was observed during forced expiration and cough, and the cross-sectional area reduction was estimated from the observed AP-distance using the results from the model study. RESULTS: Model study: The flow resistance increases significantly when the cross-sectional area is reduced to >70% for an obstruction length of 3 cm. Patient study: EDAC was found in 18 patients during cough, none during forced expiration. There was no correlation between the obstructions found and the results from pulmonary function tests. CONCLUSIONS: EDAC during peak pressure has negligible impact on pulmonary function tests and breathing symptoms. The importance of the severity, length, and duration of the EDAC is discussed.

Reference values for within-breath pulmonary impedance parameters in asymptomatic elderly.

INTRODUCTION: A new application for the forced oscillation technique (FOT) has been described by Dellaca et al. using sinusoidal pressure variations at 5 Hz to detect expiratory flow limitation by measuring the within-breath reactance [termed difference between inspiratory and expiratory X5 (DX5)]. Few studies have been performed on respiratory phase differences in the elderly. OBJECTIVE: Our aim was to present reference values for within-breath impedance measurements and to examine how the earlier mentioned method performs in a study population of asymptomatic elderly. METHODS: An age- and sex-stratified random sample was drawn from the elderly population of Bergen, Norway. Among the healthy non-smoking responders from a postal questionnaire study, 148 were selected to perform FOT measurements using an impulse oscillometry system (IOS). Seventy five of these participants had a normal spirometry and were able to perform at least two valid FOT measurements. Predictive equations for men and women were created for FOT parameters by linear multiple regression analysis. DX5 was calculated from the within-breath variation of reactance at 5 Hz. RESULTS/CONCLUSION: This study presents reference values for whole-breath and within-breath impedance parameters in asymptomatic elderly aged >70 years using the IOS method. We found higher resistance measurements than what is reported in previous studies and significantly larger frequency dependence.

3-D endobronchial ultrasonography--a post mortem study.

Endobronchial ultrasonography (EBUS) using balloon-embedded probes may cause airway obstruction and requires a rapid scanning procedure. Three-dimensional (3-D) postprocessing of sequential 2-D images may allow detailed studies on a rapidly acquired image volume. We applied a 3-D reconstruction program on EBUS recordings acquired with a radial-scanning probe during a controlled pullback procedure in water-filled airways in five corpses. The aim was to acquire EBUS images under optimized conditions and to test a 3-D software program for postprocessing. Under post mortem conditions, 3-D images were obtained, allowing any-plane imaging and measurements, application of different rendering and visualization algorithms and merging of overlapping volumes.

Reference values for arterial blood gases in the elderly.

OBJECTIVES: We present reference values for arterial blood gas measurements for persons > 70 years old. At the same time, we wish to examine how different criteria for exclusion from the reference sample with regard to previous smoking and various comorbidities might influence reference values. METHODS: After first screening a random sample of the general elderly population by postal questionnaire, we selected 146 men and women without respiratory disease, significant dyspnea, symptomatic heart disease or hypertension, or current smoker status. Arterial blood samples were drawn from subjects while in the supine position. RESULTS: The mean (SD; lower limit of normal) PaO(2) and arterial oxygen saturation (SaO(2)) for men was 77.0 mm Hg (9.1; 62.0) and 95.3% (1.4; 93.0), respectively, and for women was 73.5 mm Hg (8.4; 59.6) and 94.8% (1.7; 92.0). Mean (SD; upper limit of normal) PaCO(2) was 39.4 mm Hg (3.3; 44.8) for both sexes. None of the blood gas variables were associated with age, smoking history, or presence of various comorbidities. CONCLUSIONS: The reference values for PaO(2) and SaO(2) in elderly persons are sex specific but age independent. Ex-smokers and persons with nonpulmonary comorbidities who do not have significant respiratory symptoms need not be excluded from the reference sample for arterial blood gases.

Effect of body position on arterial oxygen tension in the elderly.

BACKGROUND: It is well known that body position can have an effect on gas exchange though the magnitude of this effect has not been studied thoroughly in the elderly. OBJECTIVES: This study analyzes the effect body position change has on arterial oxygen tension (PaO(2)) and arterial carbon dioxide tension (PaCO(2)) in healthy elderly. METHODS: We tested 46 "lung-healthy" elderly, including 30 women and 16 men, 67-88 years of age. Blood was drawn from the radial artery first in the sitting position and subsequently in the supine position. Spirometry was performed. RESULTS: Mean (SD) sitting PaO(2) was 10.53 kPa (1.22), whereas mean supine PaO(2) was 9.85 kPa (1.33). The difference between sitting and supine PaO(2) was 0.68 kPa (0.86) and was statistically significant. Sitting PaCO(2) was 5.06 kPa (0.47) and supine PaCO(2) was 5.05 kPa (0.54). The difference between sitting and supine PaO(2) correlated positively with FEV(1)/FVC %, negatively with the corresponding difference between sitting and supine PaCO(2), and negatively with BMI. CONCLUSIONS: We conclude that the significant difference in PaO(2) in sitting and supine positions clearly shows that the position needs to be considered both when attempting to establish reference values and when evaluating gas exchange in elderly persons. The positional changes in oxygenation are related to the corresponding change in PaCO(2), and to FEV(1)/FVC % and BMI.