Sleep misperception, EEG characteristics and autonomic nervous system activity in primary insomnia: a retrospective study on polysomnographic data.

Misperception of Sleep Onset Latency, often found in Primary Insomnia, has been cited to be influenced by hyperarousal, reflected in EEG- and ECG-related indices. The aim of this retrospective study was to examine the association between Central Nervous System (i.e. EEG) and Autonomic Nervous System activity in the Sleep Onset Period and the first NREM sleep cycle in Primary Insomnia (n=17) and healthy controls (n=11). Furthermore, the study examined the influence of elevated EEG and Autonomic Nervous System activity on Stage2 sleep-protective mechanisms (K-complexes and sleep spindles). Confirming previous findings, the Primary Insomnia-group overestimated Sleep Onset Latency and this overestimation was correlated with elevated EEG activity. A higher amount of beta EEG activity during the Sleep Onset Period was correlated with the appearance of K-complexes immediately followed by a sleep spindle in the Primary Insomnia-group. This can be interpreted as an extra attempt to protect sleep continuity or as a failure of the sleep-protective role of the K-complex by fast EEG frequencies following within one second. The strong association found between K-alpha (K-complex within one second followed by 8-12 Hz EEG activity) in Stage2 sleep and a lower parasympathetic Autonomic Nervous System dominance (less high frequency HR) in Slow-wave sleep, further assumes a state of hyperarousal continuing through sleep in Primary Insomnia.

Treatment of obstructive sleep apnea using a custom-made titratable duobloc oral appliance: a prospective clinical study.

PURPOSE: This prospective clinical study investigates the efficacy of a specific custom-made titratable mandibular advancement device (MAD) for the treatment of obstructive sleep apnea (OSA). This MAD has attachments in the frontal teeth area that allow for progressive titration of the mandible. METHODS: Sixty-one adult OSA patients were included (age, 46.7 ± 9.0 years; male/female ratio, 45/16; apnea-hypopnea index (AHI), 23.2 ± 15.4 events/h sleep; body mass index, 27.9 ± 4.1 kg/m²). After an adaptation period, titration started based on a protocol of symptomatic benefit or upon reaching the physiological limits of protrusion. As a primary outcome, treatment response was defined as an objective reduction in AHI following MAD treatment of ≥50 % compared to baseline, and treatment success as a reduction in AHI with MAD to less than 5 and 10 events/h sleep. Compliance failure was defined as an inability to continue treatment. RESULTS: A statistically significant decrease was observed in AHI, from 23.4 ± 15.7 at baseline to 8.9 ± 8.6 events/h with MAD (p < 0.01). Treatment response was achieved in 42 out of 61 patients (68.8 %), whereas 42.6 % met criteria of AHI < 5 and 63.9 % achieved an AHI < 10 events/h sleep, respectively. Four patients (6.6 %) were considered as "compliance failures." CONCLUSIONS: The present study has evaluated the efficacy of a specific custom-made titratable MAD in terms of sleep apnea reduction.

Aortic root diameter and nasal intermittent positive airway pressure treatment in Marfan's syndrome.

We report on a patient with Marfan's syndrome, with coexistent obstructive sleep hypopnea (OSH) and restrictive lung disease, complicated by respiratory insufficiency, who was successfully treated with nasal intermittent positive airway pressure (NIPPV) and oxygen. NIPPV therapy turned out to be effective on arterial gas exchange and well tolerated. Moreover, progressive dilatation of the aortic root was attenuated during NIPPV, but could, however, not be reversed. We hypothetized that (at least partially) a decrease of nocturnal intrathoracic pressures could explain this.

Short-term CPAP does not influence the increased CO2 drive in idiopathic central sleep apnea.

Continuous positive airway pressure (CPAP) improves idiopathic central sleep apnea (ICSA), but the mechanisms are not completely understood. It has been demonstrated that some ICSA patients have an increased CO2 drive, expressed by the hypercapnic ventilatory response (HCVR). The aim of our study was to evaluate whether CPAP can decrease the HCVR in successfully treated ICSA patients. Also the central apnea mean duration (CMD) was studied. Nine patients were evaluated. Their apnea-hypopnea index at baseline was high, but decreased from 50 +/- 5 to 8 +/- 3, during 5 +/- 1 cm H2O CPAP. After one month CPAP high values were still found for HCVR (2.69 +/- 0.23 L.min-1.mmHg-1 at baseline, 2.71 +/- 0.33 L.min-1.mmHg-1 after CPAP). Sleep quality was only improved by a decrease in the arousal index (from 29 +/- 12 to 6 +/- 1 a night) (p = 0.04). Daytime arterial O2 partial pressure (PaO2) increased from 73 +/- 4 mmHg to 85 +/- 3 mmHg (p = 0.02), whereas daytime arterial CO2 partial pressure (PaCO2) remained unchanged (from 41 +/- 1 mmHg to 40 +/- 1 mmHg). CMD was 21 +/- 6 s before and 13 +/- 1 s after CPAP (p = 0.05). The presence of hypersomnolence decreased from in 89% to in 33% of the patients. It is concluded that CPAP treatment can induce a subjective and objective improvement in ICSA patients, with improved sleep-related respiratory indices, daytime PaO2, but without a change in CO2 drive. High chemical drives seem to be the cause and not the consequence of sleep disordered breathing and persist after treatment.

Intermittent positive airway pressure by nasal mask as a treatment for respiratory insufficiency in a patient with syringomyelia.

We report a case of a 73-year-old woman with chronic respiratory failure in association with syringohydromyelia and sleep apnea. She was initially intubated and mechanically ventilated. Weaning from the ventilator was only successful after nasal intermittent positive airway pressure therapy was started. A normalization of arterial blood gas exchange could be achieved.

Continuous positive airway pressure and lung inflation in sleep apnea patients.

BACKGROUND: It was shown in normals that an important decrease in upper airway resistance can be obtained with continuous positive airway pressure (CPAP). It was suggested that lung inflation in patients with sleep apnea syndrome (SAS) could also be a mechanism of action of CPAP. OBJECTIVE: In the present study we wanted to evaluate the effects of nocturnal CPAP on the daytime lung function pattern in patients with SAS. METHODS: We measured arterial blood gases and possible changes in static lung volumes in 57 SAS patients (37 with normal lung function, 10 with COPD and 10 with restrictive lung disease) after at least one month of CPAP therapy. RESULTS: A significant increase in PaO(2) (from 79 to 84 mm Hg, p = 0.01) and a decrease in AaDO(2) (from 23 +/- 1 to 16 +/- 1, p < 0.01) was only observed in SAS patients with normal lung function. This improved gas exchange was parallelled by a small but non significant change in the FRC (from 96.5 +/- 3.2 to 105.4 +/- 3.7%pred, p = 0.07) and TLC (from 101.3 +/- 1.7 to 104.1 +/- 1.4%pred, p = 0.15). Similar changes in TLC and FRC were also observed in SAS patients with obstructive and restrictive lung disease. CONCLUSIONS: Chronic nocturnal CPAP therapy can improve daytime gas exchange and may influence lung inflation during the daytime. The small changes seem to be a functional effect but of no clinical relevance.

Influence of longterm CPAP therapy on CO(2) drive in patients with obstructive sleep apnea.

According to recent publications, the values of the hypercapnic ventilatory responses (HCVR) in normocapnic obstructive sleep apnea (OSA) patients are highly variable, but they are usually within the normal range. In our study, CPAP therapy during 1 month did not seem to influence the HCVR [Verbraecken, J., De Backer, W., Willemen, M., De Cock, W., Wittesaele, W., Van de Heyning, P., 1995. Respir. Physiol. 101, 279-287]. It is, however, not well studied whether long term (1 year) CPAP therapy can influence HCVR in normocapnic patients. Therefore, we evaluated the effect of 1 year CPAP therapy on CO(2) drive in 20 OSA patients. The slope of HCVR (SHCVR) changed from 2.35+/-0.21 L min(-1) mmHg(-1) (control) to 1.66+/-0.16 L min(-1) mm Hg(-1) (P=0.04), but the mean within subject coefficient of variation in repeated measurements of SHCVR in treated and untreated OSA patients was not statistically different. Pa(O(2)) increased from 72+/-2 mm Hg to 80+/-2 (1 year) mm Hg. We conclude that CPAP therapy improves daytime gas exchange in normocapnic OSA and may possibly decrease CO(2) drive (slope) after a treatment period of 1 year.

Kinematics and ground reaction forces in horses with superficial digital flexor tendinitis.

OBJECTIVE: To measure and correlate kinematic and ground reaction force (GRF) data in horses with superficial digital flexor tendinitis. ANIMALS: 6 sound horses. PROCEDURE: Horses were evaluated before (sound evaluation) and after (lame evaluation) induction of superficial digital flexor tendinitis in 1 forelimb (randomized) by injection of collagenase. As each horse trotted, kinematic data were collected by use of an optoelectronic system, and GRF data were measured by use of a force plate. Three-dimensional kinematic and GRF data were projected onto a 2-dimensional sagittal plane. RESULTS: Lame limbs had significantly lower peak vertical GRF, less flexion of the distal interphalangeal joint, and less extension of the metacarpophalangeal joint, compared with compensating limbs. Carpal joint kinematics did not change. Compensating limbs had a more protracted orientation throughout the stance phase and higher braking longitudinal force and impulse; however, total range of rotation from ground contact to lift off did not change. Transfer of body weight from lame to compensating limbs was smooth, without elevation of the body mass into a suspension phase. Propulsive components of longitudinal GRF did not differ between limbs. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with experimentally induced superficial digital flexor tendinitis, changes in vertical GRF were reflected in angular excursions of the distal interphalangeal and metacarpophalangeal joints, whereas changes in longitudinal GRF were associated with alterations in the protraction-retraction angle of the entire limb.

Net joint moments and joint powers in horses with superficial digital flexor tendinitis.

OBJECTIVE: To determine whether analysis of net joint moments and joint powers is a suitable technique for evaluation of mechanics and energetics of lameness in horses and to measure effects of superficial digital flexor tendinitis. ANIMALS: 6 sound horses. PROCEDURE: Horses were evaluated before (sound evaluation) and after (lame evaluation) induction of superficial digital flexor tendinitis in 1 forelimb by injection of collagenase. Recordings were made with an optoelectronic system and a force plate as horses trotted. Net joint moments and joint powers in the sagittal plane at each joint in the forelimbs during the stance phase were determined. Peak values were determined, and mechanical energy absorbed and generated at each joint was calculated. Comparisons were made between contralateral limbs during sound and lame evaluations. RESULTS: Lame limbs had significant reductions in peak values for net joint moments on the palmar aspect of metacarpophalangeal (fetlock), carpal, and humeroulnar joints. Total energy absorbed was significantly lower at every joint in lame limbs, compared with compensating limbs. CONCLUSIONS AND CLINICAL RELEVANCE: Horses with superficial digital flexor tendinitis had significant differences between lame and compensating limbs for net joint moments and joint powers at all joints, indicating that the gait of horses with superficial digital flexor tendinitis is energetically inefficient. Assessment of net joint moments and joint powers is a useful tool in evaluating equine lameness.

Two months follow up of auto-CPAP treatment in patients with obstructive sleep apnoea.

BACKGROUND: Continuous positive airway pressure (CPAP) with fixed mask pressure is the current standard treatment for obstructive sleep apnoea (OSA). Auto-CPAP devices apply at any time the minimally required pressure to normalise breathing and may improve patient comfort and compliance. We present an open descriptive study of auto-CPAP treatment at home in patients previously managed with conventional CPAP. METHODS: Fifteen patients with obstructive sleep apnoea (OSA), previously treated for at least one year with standard CPAP, were followed prospectively for a two month period on auto-CPAP. Outcome measures were both subjective evaluation by the patients and objective (polysomnographic) data obtained at one and two months of follow up. RESULTS: The Epworth sleepiness score did not change significantly between baseline and follow up after one and two months and no systematic changes in CPAP related side effects were reported. Compared with the baseline polysomnographic values without treatment, a significant improvement in both respiratory and sleep parameters was observed during auto-CPAP. These results were not significantly different from those obtained with standard CPAP. A significant correlation was found between the effective CPAP pressure (Peff) and the amount of time spent below Peff during auto-CPAP treatment (r = 0.6, p = 0.01). CONCLUSION: Long term auto-CPAP treatment in these patients with severe OSA appears to provide comparable efficacy to that of standard CPAP treatment.

The effect of orthopaedic shoeing on the force exerted by the deep digital flexor tendon on the navicular bone in horses.

This study quantifies both the intended effect of orthopaedic shoeing to decrease the load on the navicular bone and the eventual undesired effects on gait performance. The compressive force exerted by the deep digital flexor tendon on the navicular bone and on the quality of the trot and redistribution of forces over the flexor tendons and the suspensory ligament were studied as a function of orthopaedic shoeing in 12 sound Dutch Warmblood horses. A modified CODA-3 gait analysis system and a force plate were used to quantify objectively the load on the lower limb. The quality of the trot was assessed using the same gait analysis system while the horses were trotting on the treadmill. The effects of shoes with heel wedges and egg-bar shoes were compared to flat shoes and unshod feet. When heel wedges were applied, the maximal force on the navicular bone was reduced by 24% (P<0.05) in comparison with flat shoes. Egg-bar shoes did not reduce the force on the navicular bone, but in unshod feet this force appeared to be 14% lower (P<0.05) compared to flat shoes. Egg-bar shoes cause the horse's trot to be slightly less animated (P<0.05), compared to flat shoes and shoes with heel wedges. It is concluded that shoes with heel wedges reduce the force on the navicular bone as a result of a decreased moment of force at the distal interphalangeal joint in combination with a decreased angle between the deep digital flexor tendon distally and proximally of the navicular bone. Therefore it can be expected that in horses suffering from navicular disease, heel wedges will have the expected beneficial effect on the pressure on the navicular bone, while the effect of egg-bar shoes remains doubtful.

In vitro transmission and attenuation of impact vibrations in the distal forelimb.

An in vitro model was developed and validated in vivo to quantify the attenuation of impact vibrations, transmitted through the lower equine forelimb and to assess the effects of horseshoeing on this attenuation. The transsected forelimbs of 13 horses were equipped with custom-made hollow bone screws in the 4 distal bones, on each of which a tri-axial accelerometer could be mounted. The limbs were then preloaded while the impact was simulated by dropping a weight on the steel plate on which the hoof was resting. At the hoof wall, the distal, middle and proximal phalanx and at the metacarpal bone, the shock waves resulting from this impact were quantified. To assess the damping effects of shoeing, measurements were performed with unshod hooves, hooves shod with a normal flat shoe and hooves shod with an equisoft pad and a silicone packing between hoof and pad. The in vitro model was validated by performing in vivo measurements using one horse, and subjecting the limb of this horse to the same in vitro measurements after death. Approximately 67% of the damping of impact vibrations took place at the interface between the hoof wall and the distal phalanx. The attenuation of impact vibrations at the distal and proximal interphalangeal joints was considerably less (both 6%), while at the metacarpophalangeal joint 9% of the amplitude of that at the hoof wall was absorbed, leaving approximately 13% of the initial amplitude at the hoof wall detectable at the metacarpus. Compared to unshod hooves the amplitude at the hoof wall is 15% higher in shod hooves. No differences could be observed between shoe types. At the level of the first phalanx and metacarpus the difference between shod and unshod vanished; it was therefore concluded that, although shoeing might influence the amplitude of impact vibrations at the hoof wall, the effect of shoeing on the amplitude at the level of the metacarpophalangeal joint is minimal.

Relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea.

Previously we showed that CO2 drive is increased in patients with obstructive sleep apnea (OSA). In the present study we would like to evaluate a possible relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea (CSA). We compared the hypercapnic ventilatory response (HCVR) between patients with OSA and CSA. HCVR was correlated with total event time and mean event duration in both groups. 17 normocapnic patients in each group and 14 controls were studied. The apnea patients were matched for apnea-hypopnea index, age, sex, and BMI. SHCVR (slope) tended to be higher in apnea patients than in controls without statistical significancy: controls 1.65 (0.16), CSA 2.17 (0.22), OSA 2.55 (0.35) (l/min per mmHg) (P = 0.13). A significant correlation was found between HCVR and event time in CSA (0.52, P = 0.04) and between HCVR and apnea mean duration in OSA (r = 0.52, P = 0.04). We conclude that while CO2 drive was not statistically increased in both apnea types, small changes can contribute to breathing instability and may increase the total event time (in CSA) but may also shorten the apnea duration (in OSA).

Net joint moments and powers in the equine forelimb during the stance phase of the trot.

The objective of this study was to provide normative data describing the net joint moments and joint powers for the stance phase of the forelimb in trotting horses. Kinematic and force plate data, synchronised in time and space, were collected for the right forelimb of 6 Warmblood horses moving at a trot. The 3-D kinematic data were collapsed onto a sagittal plane, and were combined with the vertical and longitudinal ground reaction forces and with segment morphometric data to calculate net joint moments in the sagittal plane across the distal interphalangeal (coffin), metacarpophalangeal (fetlock), carpal, elbow and shoulder joints. The joint mechanical power was calculated as the product of the joint moment and the joint's angular velocity. Major peaks on the moment and power curves were identified. Each joint showed consistent and repeatable patterns in the net joint moments and joint powers. During most of stance the net joint moment was on the caudal/palmar side of all joints except the shoulder. At the coffin joint the power profile indicated an energy absorbing function that peaked at 74% stance, which coincided with the maximal longitudinal propulsive force. The fetlock joint behaved as an elastic spring; energy was absorbed in the first half of stance as the flexor tendons and SL stored elastic energy, which was released in the second half of stance as a result of elastic recoil. The carpus did not appear to play an important role in energy absorption or propulsion. Both the elbow and shoulder joints showed what appeared to be phases of elastic energy storage and release in the middle part of the stance phase, followed by a propulsive function at the shoulder in the later part of stance. The fetlock, carpus and elbow showed virtually no net generation or absorption of energy. The net energy generation at the shoulder joint was approximately equal to the energy absorption at the coffin joint. In human subjects specific gait pathologies produce characteristic alterations in the shape of the power profile as well as changes in the amount of energy absorbed and generated at the joints. In horses evaluation of net joint moments and joint powers will further our understanding of the mechanics and energetics of lameness, and may prove to be a useful diagnostic tool. An understanding of the function and dysfunction of different anatomical structures will facilitate the interpretation of clinical findings in terms of mechanical deficits.

Central sleep apnea after interrupting longterm acetazolamide therapy.

One month administration of acetazolamide (ACET) (at sea level) improves periodic breathing and decreases the number of central apneas (CA) (De Backer et al., 1995 Am. J. Respir. Crit. Care Med. 151, 87-91) in nonhypercapnic central apnea syndrome. It remains unclear whether cessation of therapy would provoke recurrence of symptoms. In the present study we evaluated the number of CA after 1 and 6 months interruption of ACET therapy. Eight patients with central sleep apnea were included [central apnea index (CAI) > 5 or apnea and hypopnea index (AHI) > 10 and obstructive apnea index (OAI) < 5]. Polysomnography was repeated once after 1 month treatment (N2), after 1 month off treatment (N3) and after 6 months off treatment. CAI (25 +/- 10 at N1) decreased during N2 (4 +/- 2) and N3 (5 +/- 3) and remained low after N4 (3 +/- 1). However an increase in the number of obstructive apneas and central hypopneas could be observed together with a shift from central apnea to hypopnea after N4. Maybe ACET induces a long lasting resetting of the CO2 threshold which is still present after interruption of the therapy.

[Nasal CPAP in sleep-related respiration disorders: patient profile, therapy compliance and influence of gas exchange and lung function pattern]. / Nasale CPAP bij slaapgebonden ademhalingsstoornissen: patientenprofiel, therapietrouw en invloed op de gasuitwisseling en het longfunctiepatroon.

A survey performed in 100 CPAP users indicated that irritation of the face, a painful nose and nasal obstruction were among the most frequently mentioned complaints in chronic CPAP users. In 132 normocapnic SAS patients a significant improvement of PaO2 was shown, with a decrease of the alveolo-arterial oxygen difference. This improved gas exchange was parallelled by a significant increase in the FRC and TLC. Maybe a modulation in force of the respiratory muscles may be involved. These data were more pronounced in obstructive sleep apnea than in central sleep apnea. In 50 chronic CPAP users we could show a lower AHI immediately after CPAP withdrawal after a previous prolonged treatment. These findings may support the insufflation theory as a mechanism of action of CPAP. Traditionally, mechanical splinting of the upper airway has been considered as the dominant mechanism of action. Other mechanisms like changes in regulation of breathing and decrease of the pharyngeal edema may be involved as well.

Assessment of respiratory effort by means of strain gauges and esophageal pressure swings: a comparative study.

We characterized apneas by a quantitative method (esophageal pressure measurements) and by a qualitative method (strain gauges) at the same time in 22 patients with sleep-related breathing disorders. Detection of respiratory effort by strain gauges significantly overestimated the total number of central apneas in each patient. Despite this overestimation, none of the patients was wrongly diagnosed as having pure central sleep apnea syndrome. Strain gauges are sufficiently reliable for the characterization of apneas in most patients. When strain gauges reveal that most apneas are central in origin, verification by esophageal pressure measurements is recommended.