Respiratory Muscle Activity Research Articles

보이타 치료중재가 뇌성마비아동의 근활성화 및 발성에 미치는 효과

Purpose : The purpose of this study was to evaluate the influence of Respiratory Capacity by Vojta`s treatment in children with spastic cerebral palsy. Method : The subjects of this study, children diagnosed with spastic cerebral palsy, 12 patients were picked up, who were agreed with this research and were having hospital care for 4weeks at MH and PR medical centers. Result : In comparison of Respiratory muscle activity and Phonation capacity were significant in the group(p

A New Technique for Jaw Thrust in Unconscious Craniofacial Trauma Patients

The loss of consciousness is one of the commonly encountered emergency situations in maxillofacial trauma patients. Apart from benign syncope, there are other causes for unconsciousness. Majority of these patients have intact respiratory muscle activity, but the airway patency is compromised due to airway obstruction by tongue fall back. Traditionally head tilt-chin lift and jaw thrust techniques were employed to maintain patency of the airway. Head tilt-chin lift technique involves tilting the head backward and thus is dangerous in case of suspected cervical spine injury in trauma cases. Jaw thrust is an efficient method and can be performed in cervical spine injury cases. But it requires continuous forward pull on mandible till the time patient regains consciousness; which is physically strenuous for rescuer. The purpose of this article is to present a new technique for jaw thrust which is based on similar principle of traditional jaw thrust. The advantage is that, jaw thrust can be maintained for an extended time period in these patients.

Correlation between pulmonary function, posture, and body composition in patients with asthma

AimAsthma may result in postural disorders due to increased activity of accessory respiratory muscles and hyperinflation. Our primary objective was to assess the correlation between pulmonary function and posture in adult patients with asthma. Secondarily, we aimed to study the correlation between body composition and body posture in this group of patients. MethodThis was a cross-sectional study including 34 patients with asthma who were subjected to postural assessment (photogrammetry), pulmonary function testing (spirometry, whole-body plethysmography, diffusing capacity for carbon monoxide, and respiratory muscle strength), and body composition estimation by means of bioelectrical impedance. ResultsMost patients were female (70.6%) with a median age of 32.5 years (range: 23–42 years old). We found a significant correlation between horizontal alignment of head (anterior view) and the ratio of forced expiratory volume in 1s to forced vital capacity (FEV1/FVC; ρ=−0.37; P=0.03), total lung capacity (TLC; ρ=0.42; P=0.01), and residual volume (RV; ρ=0.45; P<0.001). Bronchial obstruction and respiratory muscle strength variables also correlated with postural assessment measures on the right and left lateral views. Both body mass index and the percentage of fat mass were correlated with horizontal alignment of head, horizontal alignment of the pelvis, and the frontal angle of the lower limbs. ConclusionAdult patients with asthma exhibit specific postural disorders that correlate with pulmonary function and body composition. The assessment of postural variables may provide a better pulmonary rehabilitation approach for these patients.

Locomotor step training with body weight support improves respiratory motor function in individuals with chronic spinal cord injury

This prospective case-controlled clinical study was undertaken to investigate to what extent the manually assisted treadmill stepping locomotor training with body weight support (LT) can change respiratory function in individuals with chronic spinal cord injury (SCI). Pulmonary function outcomes (forced vital capacity /FVC/, forced expiratory volume one second /FEV1/, maximum inspiratory pressure /PImax/, maximum expiratory pressure /PEmax/) and surface electromyographic (sEMG) measures of respiratory muscles activity during respiratory tasks were obtained from eight individuals with chronic C3–T12 SCI before and after 62±10 (mean±SD) sessions of the LT. FVC, FEV1, PImax, PEmax, amount of overall sEMG activity and rate of motor unit recruitment were significantly increased after LT (p<0.05). These results suggest that these improvements induced by the LT are likely the result of neuroplastic changes in spinal neural circuitry responsible for the activation of respiratory muscles preserved after injury.

State-dependent and reflex drives to the upper airway: basic physiology with clinical implications

The root cause of the most common and serious of the sleep disorders is impairment of breathing, and a number of factors predispose a particular individual to hypoventilation during sleep. In turn, obstructive hypopneas and apneas are the most common of the sleep-related respiratory problems and are caused by dysfunction of the upper airway as a conduit for airflow. The overarching principle that underpins the full spectrum of clinical sleep-related breathing disorders is that the sleeping brain modifies respiratory muscle activity and control mechanisms and diminishes the ability to respond to respiratory distress. Depression of upper airway muscle activity and reflex responses, and suppression of arousal (i.e., "waking-up") responses to respiratory disturbance, can also occur with commonly used sedating agents (e.g., hypnotics and anesthetics). Growing evidence indicates that the sometimes critical problems of sleep and sedation-induced depression of breathing and arousal responses may be working through common brain pathways acting on common cellular mechanisms. To identify these state-dependent pathways and reflex mechanisms, as they affect the upper airway, is the focus of this paper. Major emphasis is on the synthesis of established and recent findings. In particular, we specifically focus on 1) the recently defined mechanism of genioglossus muscle inhibition in rapid-eye-movement sleep; 2) convergence of diverse neurotransmitters and signaling pathways onto one root mechanism that may explain pharyngeal motor suppression in sleep and drug-induced brain sedation; 3) the lateral reticular formation as a key hub of respiratory and reflex drives to the upper airway.

Physiologic Effects of an Ambulatory Ventilation System in Chronic Obstructive Pulmonary Disease

Exercise intolerance limits the ability of patients with chronic obstructive pulmonary disease (COPD) to perform daily living activities. Noninvasive ventilation reduces dyspnea and improves exercise performance, but current systems are unsuitable for ambulatory use. In patients with COPD experiencing exercise-induced desaturation, we evaluated improvements in exercise tolerance facilitated by a wearable, 1-lb, noninvasive open ventilation (NIOV) system featuring a nasal pillow interface during constant work rate (CWR) cycle ergometer exercise and associated effects on dyspnea, respiratory muscle activation, and pulmonary gas exchange efficiency. Fifteen men with COPD (FEV₁ = 32.2 ± 12.0% predicted; FEV₁/FVC = 31.6 ± 7.1%; exercise oxygen saturation as measured by pulse oximetry [Spo₂] = 86.5 ± 2.9%) participated. After incremental testing establishing peak work rate, subjects completed three visits in which they performed CWR exercise to tolerance at 80% peak work rate: (1) unencumbered breathing room air, (2) using NIOV+compressed air, (3) using NIOV+compressed O₂, or (4) using O₂ via nasal cannula. Assessments included exercise duration, surface inspiratory muscle EMG, Spo₂, transcutaneous Pco₂, and Borg dyspnea scores. Exercise endurance was 17.6 ± 5.7 minutes using NIOV+O₂, greatly prolonged compared with unencumbered (5.6 ± 1.9 min), nasal O₂ (11.4 ± 6.8 min), and NIOV+Air (6.3 ± 4.1 min). Isotime Spo₂ was higher and intercostal, scalene, and diaphragmatic EMG activity was reduced using NIOV+O₂ compared with unencumbered, nasal O₂, and NIOV+Air, signifying respiratory muscle unloading. Isotime dyspnea reduction correlated with isotime EMG reduction (r = 0.42, P = 0.0053). There were no significant differences in isotime VD/VT or transcutaneous Pco₂ among treatments. NIOV+O₂ yielded substantial exercise endurance improvements accompanied by respiratory muscle unloading and dyspnea reductions in patients with severe hypoxemic COPD.

Evaluation of Respiratory Muscle Activation Using Respiratory Motor Control Assessment (RMCA) in Individuals with Chronic Spinal Cord Injury

During breathing, activation of respiratory muscles is coordinated by integrated input from the brain, brainstem, and spinal cord. When this coordination is disrupted by spinal cord injury (SCI), control of respiratory muscles innervated below the injury level is compromised1,2 leading to respiratory muscle dysfunction and pulmonary complications. These conditions are among the leading causes of death in patients with SCI3. Standard pulmonary function tests that assess respiratory motor function include spirometrical and maximum airway pressure outcomes: Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), Maximal Inspiratory Pressure (PImax) and Maximal Expiratory Pressure (PEmax)4,5. These values provide indirect measurements of respiratory muscle performance6. In clinical practice and research, a surface electromyography (sEMG) recorded from respiratory muscles can be used to assess respiratory motor function and help to diagnose neuromuscular pathology. However, variability in the sEMG amplitude inhibits efforts to develop objective and direct measures of respiratory motor function6. Based on a multi-muscle sEMG approach to characterize motor control of limb muscles7, known as the voluntary response index (VRI)8, we developed an analytical tool to characterize respiratory motor control directly from sEMG data recorded from multiple respiratory muscles during the voluntary respiratory tasks. We have termed this the Respiratory Motor Control Assessment (RMCA)9. This vector analysis method quantifies the amount and distribution of activity across muscles and presents it in the form of an index that relates the degree to which sEMG output within a test-subject resembles that from a group of healthy (non-injured) controls. The resulting index value has been shown to have high face validity, sensitivity and specificity9-11. We showed previously9 that the RMCA outcomes significantly correlate with levels of SCI and pulmonary function measures. We are presenting here the method to quantitatively compare post-spinal cord injury respiratory multi-muscle activation patterns to those of healthy individuals.

Evaluation of respiratory muscle activation using respiratory motor control assessment (RMCA) in individuals with chronic spinal cord injury.

During breathing, activation of respiratory muscles is coordinated by integrated input from the brain, brainstem, and spinal cord. When this coordination is disrupted by spinal cord injury (SCI), control of respiratory muscles innervated below the injury level is compromised leading to respiratory muscle dysfunction and pulmonary complications. These conditions are among the leading causes of death in patients with SCI. Standard pulmonary function tests that assess respiratory motor function include spirometrical and maximum airway pressure outcomes: Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), Maximal Inspiratory Pressure (PImax) and Maximal Expiratory Pressure (PEmax). These values provide indirect measurements of respiratory muscle performance(6). In clinical practice and research, a surface electromyography (sEMG) recorded from respiratory muscles can be used to assess respiratory motor function and help to diagnose neuromuscular pathology. However, variability in the sEMG amplitude inhibits efforts to develop objective and direct measures of respiratory motor function. Based on a multi-muscle sEMG approach to characterize motor control of limb muscles, known as the voluntary response index (VRI), we developed an analytical tool to characterize respiratory motor control directly from sEMG data recorded from multiple respiratory muscles during the voluntary respiratory tasks. We have termed this the Respiratory Motor Control Assessment (RMCA). This vector analysis method quantifies the amount and distribution of activity across muscles and presents it in the form of an index that relates the degree to which sEMG output within a test-subject resembles that from a group of healthy (non-injured) controls. The resulting index value has been shown to have high face validity, sensitivity and specificity. We showed previously that the RMCA outcomes significantly correlate with levels of SCI and pulmonary function measures. We are presenting here the method to quantitatively compare post-spinal cord injury respiratory multi-muscle activation patterns to those of healthy individuals.

Correlação entre função pulmonar, postura e composição corporal em pacientes com asma

AimAsthma may result in postural disorders due to increased activity of accessory respiratory muscles and hyperinflation. Our primary objective was to assess the correlation between pulmonary function and posture in adult patients with asthma. Secondarily, we aimed to study the correlation between body composition and body posture in this group of patients. MethodThis was a cross-sectional study including 34 patients with asthma who were subjected to postural assessment (photogrammetry), pulmonary function testing (spirometry, whole-body plethysmography, diffusing capacity for carbon monoxide, and respiratory muscle strength), and body composition estimation by means of bioelectrical impedance. ResultsMost patients were female (70.6%) with a median age of 32.5 years (range: 23-42 years old). We found a significant correlation between horizontal alignment of head (anterior view) and the ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC; ρ=−0,37; P=.03), total lung capacity (TLC; ρ=0,42; P=.01), and residual volume (RV; ρ=0,45; P<.001). Bronchial obstruction and respiratory muscle strength variables also correlated with postural assessment measures on the right and left lateral views. Both body mass index and the percentage of fat mass correlated with horizontal alignment of head, horizontal alignment of the pelvis, and the frontal angle of the lower limbs. ConclusionAdult patients with asthma exhibit specific postural disorders that correlate with pulmonary function and body composition. The assessment of postural variables may provide a better pulmonary rehabilitation approach for these patients.

Consecutive transcranial magnetic stimulation twitches reduce flow limitation during sleep in apnoeic patients

What is the central question of this study? A transcranial magnetic stimulation (TMS)-induced twitch applied on isolated single breaths over the motor cortex somatotopic representation of the tongue briefly recruits submental muscles and improves airflow dynamics of flow-limited respiratory cycles without arousing sleep apnoea patients. However, the mechanical impact of the TMS-induced twitch applied during consecutive breathing cycles on airflow dynamics remains unknown. What is the main finding and what is its importance? Our results show that application of TMS with the stimulator output set at the sleep submental motor threshold intensity on consecutive respiratory cycles increases inspiratory flow and reduces the turbulent airflow component. These results indicate an improvement of airflow pattern after two single consecutive TMS-induced twitches without arousing sleep apnoea patients. Transcranial magnetic stimulation (TMS)-induced twitches applied on isolated breaths briefly recruit upper airway dilator muscles and improve airflow and inspiratory volume without arousing apnoeic patients from sleep, but the effects of applying such twitches consecutively on airflow dynamics is unknown. The objective of this study was to quantify the effects of five consecutive TMS-induced twitches applied on sleep-induced obstructive hypopnoeic breaths in 10 obstructive sleep apnoea patients. Submental muscle motor threshold (SUBMT) and motor-evoked potential were measured during wakefulness and sleep. The TMS-induced twitches were applied during stable non-rapid eye movement (NREM) sleep, at the beginning of inspiration of consecutive flow-limited respiratory cycles, with the stimulator output set at sleep SUBMT. Maximal inspiratory flow, inspiratory volume, inspiratory time, shifts of electroencephalogram frequency and pulse rate variability were assessed. During sleep, SUBMT increased (wakefulness, 25.3 ± 4.9%; NREM sleep, 27.0 ± 6.2%; P = 0.02). During each series of stimulations there was a rise in maximal inspiratory flow (from 306.7 ± 123.2 to 359.8 ± 154.1 ml s(-1); P = 0.0002) and in inspiratory volume (from 346.1 ± 128.1 to 414.9 ± 171.2 ml; P = 0.02) without differences in thoraco-abdominal efforts and inspiratory time. These responses were observed in the absence of arousals and ceased immediately after TMS interruption. Transcranial magnetic stimulation-induced cortical and/or autonomic arousal was observed in 30.2% of all series of stimulation. Consecutive twitch TMS of submental muscles may lead to arousals in a minority of patients but can be applied on consecutive respiratory cycles during sleep and can significantly improve maximal inspiratory flow and inspiratory volume of flow-limited cycles.

The origin of air breathing in vertebrates: turn (on) your head and cough

Air breathing in tetrapods involves a centrally generated rhythmic activation of respiratory muscles to ventilate a lung, and modulation of this rhythm by central CO2‐sensitive chemoreceptors that match ventilation to metabolic demands. The tetrapod lung arose in primitive air‐breathing fish. The origins of the central rhythm generator and chemoreceptor(s) are unknown. We propose that these critical elements were present in basal vertebrates and were exapted for air breathing with the evolution of the lung. Lamprey represent the basal vertebrate form and as larvae (ammocoetes) are aquatic burrow dwelling filter feeders. We propose that a behavior characterized as “cough” in lamprey is the basis for subsequent evolution of air breathing, and test the hypothesis that the centrally generated cough is stimulated by CO2. Ammocetes in vivo and isolated brainstems in vitro were exposed to hypercapnia. Ammocetes responded with a dose dependant increase in the frequency of spontaneous cough. Brainstems in vitro also produced the cough motor pattern, illustrating that cough results from a centrally CO2‐sensitive rhythm generator. We conclude that a central CO2‐sensitive chemoreceptor and central rhythm generator were present in basal vertebrates. We propose that, with the evolution of the lung, CO2‐sensitive cough is exapted to form the basis for air breathing common to air‐breathing tetrapods. Supported by NSFIOS‐1022442

A window into diaphragm kinetics: feasibility, precision, and physiological meaning of ultrasound measurements of diaphragm thickness

Inadequate respiratory muscle activity has been linked to ventilator-induced diaphragm dysfunction. Current techniques for monitoring respiratory muscle activity during mechanical ventilation are specialized and relatively invasive. Visualizing diaphragm thickening during inspiration by ultrasound may permit non-invasive monitoring. We explored the feasibility, reliability and physiological significance of diaphragm thickening on ultrasound.

PC-FACS

PC-FACS

Bronchoscopy During Non-Invasive Mechanical Ventilation: A Review of Techniques and Procedures

Non-invasive mechanical ventilation (NIMV) is used to treat acute respiratory failure by improving gas exchange abnormalities and reducing the signs of respiratory effort, dyspnea and the activity of accessory respiratory muscles. Bronchoscopy is a key technique in the study of respiratory diseases that is necessary to perform in acute and critical patients, most of the times only after orotracheal intubation (OTI) due to possible complications of the technique. In this review, we evaluate the evidence of NIMV use during bronchoscopy, concluding that its use should be considered in severe patients as an alternative that is capable of preventing the complications related with OTI and mechanical ventilation, especially in patients with chronic obstructive pulmonary disease and with a tendency toward developing hypercapnia.

Immediate effects of Taping of Upper Back on Peak Expiratory Flow Rate (Pefr) in Stable Chronic Obstructive Pulmonary Disease (Copd) Subjects

Background: The activation of respiratory muscles is influenced by a change in gravitational force and length-tension variations. Many studies have shown the influence of posture on respiratory muscles in normal adults. The proprioceptive facilitation of musculoskeletal system has shown improvement in pulmonary functions of normal adults. The lack of evidence on the effect of posture in COPD subjects suggested a need to see the immediate effects of proprioceptive facilitation of upper back on peak expiratory flow rate (PEFR) through taping on stable COPD subjects. Objectives of the study: To determine the PEFR values pre and post-taping in experimental group, to determine the PEFR values pre and post-taping in control group, to compare the PEFR values pre and post-taping within the groups and to compare the PEFR values pre and post-taping between the groups. Methodology: 34 stable COPD subjects were recruited through convenience sampling. All the subjects were randomly allocated to experimental group (17) and control group (17). The PEFR was measured by peak flow meter as baseline data for both the groups. The experimental group was given proprioceptive facilitation through taping of upper back by instructing the subjects to erect their spine and retract their shoulders whereas control group was given sham taping. The PEFR for both the groups was measured pre and post taping. Results: Paired t test was done to compare the PEFR values within the groups and independent t test was used for comparison between the groups. Interpretation: On analyzing the test, significant results were seen in the experimental and control group. The experimental group showed significant improvement in PEFR value(p Conclusion: The results suggest that proprioceptive facilitation of upper back through taping in COPD subjects improves pulmonary function.

The Effects of Combination of Inspiratory Diaphragm Exercise and Exspiratory Pursed-lip Breathing Exercise on Pulmonary Functions of Stroke Patients

[Purpose] The purpose of this study was to examine the effects of a combination of inspiratory diaphragm exercise and expiratory pursed-lip breathing exercise on pulmonary functions and respiratory muscle activation of stroke patients. [Methods] Thirty stroke patients were randomly and equally allocated to an experimental group and a control group, and the intervention was conducted five times per week for four weeks. In each session, both groups received rehabilitative exercise treatment for 30 minutes, and a feedback breathing device exercise for 15 minutes. In addition, the experimental group performed a combination of inspiratory diaphragm breathing exercise and the expiratory pursed-lip breathing exercise for 15 minutes. Prior to and after the intervention, patients’ pulmonary functions were measured using a spirometer. The pulmonary functions assessed were tests included FVC, FEV1, FVC/FEV1, PEF, VC, TV, IC, ERV, IRV. [Results] With respect to changes in the pulmonary functions of both groups after the intervention, the experimental group showed significant differences in FVC/FEV1, TV, and IC, but not in FVC, FEV1, PEF, VC, ERV, and IRV. The control group showed no significant differences. There were significant differences in FEV1, TV, and IC between the two groups, but no significant differences in FVC, PEF, FVC/FEV1, VC, ERV, and IRV after the experiment. [Conclusions] The experimental group, which conducted a combination of breathing machine exercise and the respiratory muscle strengthening exercise, saw their respiratory ability increase more significantly than the control group. The combination breathing exercise was found to improve pulmonary functions of stroke patients.

Volume Rather Than Flow Incentive Spirometry Is Effective in Improving Chest Wall Expansion and Abdominal Displacement Using Optoelectronic Plethysmography

Incentive spirometers are widely used in clinical practice and classified as flow-oriented (FIS) and volume-oriented (VIS). Until recently the respiratory inductive plethysmography used to evaluate the effects of incentive spirometry on chest wall mechanics presented limitations, which may explain why the impact of VIS and FIS remains poorly known. To compare the effects of VIS and FIS on thoracoabdominal mechanics and respiratory muscle activity in healthy volunteers. This cross-sectional trial assessed 20 subjects (12 female, ages 20-40 years, body mass index 20-30 kg/m(2)). All subjects performed 8 quiet breaths and 8 deep breaths with FIS and VIS, in a randomized order. We measured thoracoabdominal chest wall, upper and lower rib-cage, and abdominal volumes with optoelectronic plethysmography, and the muscle activity of the sternocleidomastoid and superior and inferior intercostal muscles with electromyography. VIS increased chest wall volume more than did FIS (P = .007) and induced a larger increase in the upper and lower rib-cages and abdomen (156%, 91%, and 151%, respectively, P < .001). By contrast, FIS induced more activity in the accessory muscles of respiration than did VIS (P < .001). VIS promotes a greater increase in chest wall volume, with a larger abdominal contribution and lower respiratory muscle activity, than does FIS in healthy adults.

Effects of hyperventilation on repeated isokinetic torque production and EMG of lower limbs

Introduction: Previously, effects of metabolic alkalosis through sodium bicarbonate ingestion on exercise performance has been extensively studied with varying results. However, when the exercise task is repeated and requires near maximum effort, the ergogenic effect is more likely to appear. Hyperventilation can produce similar effect on blood pH, however its influence on maximum repeated exercise remains to be investigated. Increased activity of respiratory muscles may also act as a diverting activity, which may prevent the reduction of central motor commands through the “Setchenov Phenomenon”.

Effects of Fastac 50 EC on bumble bee Bombus terrestris L. respiration: DGE disappearance does not lead to increasing water loss

Sublethal effects of pesticides in insects can be observed through physiological changes, which are commonly estimated by metabolic rate and respiratory patterns, more precisely by the patterns of discontinuous gas-exchange (DGE) cycles. The aim of the present research was to study the effect of some low concentrations of Fastac 50 EC on the cycles of CO2 release and respiratory water loss rates (WLR) in bumble bee Bombus terrestris L. foragers. Bumble bees were dipped into 0.004% and 0.002% Fastac 50 EC solution. Flow-through respirometry was used to record the respiration and WLR 3h before and after the treatment. The respirometry was combined with infrared actography to enable simultaneous recording of abdominal movements. Our results show that Fastac 50 EC has an after-effect on bumble bee respiratory rhythms and muscle activity but does not affect WLR. Treatment with 0.004% Fastac 50 EC solution resulted in disappearance of the respiration cycles; also the lifespan of treated bumble bees was significantly shorter. Treatment with 0.002% Fastac 50 EC solution had no significant effect on respiration patterns or longevity. We found no evidence for the DGE cycles functioning as a water saving mechanism.

State-Dependent Modulation of Breathing in Urethane-Anesthetized Rats

Respiratory activity is most fragile during sleep, in particular during paradoxical [or rapid eye movement (REM)] sleep and sleep state transitions. Rats are commonly used to study respiratory neuromodulation, but rodent sleep is characterized by a highly fragmented sleep pattern, thus making it very challenging to examine different sleep states and potential pharmacological manipulations within them. Sleep-like brain-state alternations occur in rats under urethane anesthesia and may be an effective and efficient model for sleep itself. The present study assessed state-dependent changes in breathing and respiratory muscle modulation under urethane anesthesia to determine their similarity to those occurring during natural sleep. Rats were anesthetized with urethane and respiratory airflow, as well as electromyographic activity in respiratory muscles were recorded in combination with local field potentials in neocortex and hippocampus to determine how breathing pattern and muscle activity are modulated with brain state. Measurements were made in normoxic, hypoxic, and hypercapnic conditions. Results were compared with recordings made from rats during natural sleep. Brain-state alternations under urethane anesthesia were closely correlated with changes in breathing rate and variability and with modulation of respiratory muscle tone. These changes closely mimicked those observed in natural sleep. Of great interest was that, during both REM and REM-like states, genioglossus muscle activity was strongly depressed and abdominal muscle activity showed potent expiratory modulation. We demonstrate that, in urethane-anesthetized rats, respiratory airflow and muscle activity are closely correlated with brain-state transitions and parallel those shown in natural sleep, providing a useful model to systematically study sleep-related changes in respiratory control.