Absence of dynamic hyperinflation during exhaustive exercise in severe COPD reflects submaximal IC maneuvers rather than a nonhyperinflator phenotype.

Approximately 20% of chronic obstructive pulmonary disease (COPD) patients have been considered to have a "nonhyperinflator phenotype." However, this judgment depends on patients making a fully maximal inspiratory capacity (IC) maneuver at rest, since the IC during exercise is compared with this baseline measurement. We hypothesized that IC maneuvers at rest are sometimes submaximal and tested this hypothesis by measuring IC and associated neural respiratory drive at rest and during inhalation of CO and exercise in patients with COPD.

Coexistence of OSA may compensate for sleep related reduction in neural respiratory drive in patients with COPD.

Background: The mechanisms underlying sleep-related hypoventilation in patients with coexisting COPD and obstructive sleep apnoea (OSA), an overlap syndrome, are incompletely understood. We compared neural respiratory drive expressed as diaphragm electromyogram (EMG) and ventilation during stage 2 sleep in patients with COPD alone and patients with overlap syndrome.

Methods: EMG and airflow were recorded during full polysomnography in 14 healthy subjects, 14 patients with OSA and 39 consecutive patients with COPD.

Neural Respiratory Drive and Arousal in Patients with Obstructive Sleep Apnea Hypopnea.

Study Objectives: It has been hypothesized that arousals after apnea and hypopnea events in patients with obstructive sleep apnea are triggered when neural respiratory drive exceeds a certain level, but this hypothesis is based on esophageal pressure data, which are dependent on flow and lung volume. We aimed to determine whether a fixed threshold of respiratory drive is responsible for arousal at the termination of apnea and hypopnea using a flow independent technique (esophageal diaphragm electromyography, EMGdi) in patients with obstructive sleep apnea.

Setting: Sleep center of state Key Laboratory of Respiratory Disease.

[Assessment of neural respiratory drive in humans].

Objective: Assessment of neural respiratory drive is useful for diagnosis of dyspnea and respiratory failure with unknown causes. The purpose of the study was to compare the sensitivity of trandiaphragmatic pressure (Pdi) and diaphragm electromyogram (EMGdi) in assessment of neural respiratory drive.

Methods: A combined catheter with 10 electrodes and 2 balloons was used to record EMGdi and Pdi during CO2 rebreathing.

[Neural respiratory drive and nocturnal hypoventilation in patients with chronic obstructive pulmonary disease].

Objective: To explore the effects of neural respiratory drive on ventilation in patients with chronic obstructive pulmonary disease (COPD) during sleep.

Methods: Diaphragm electromyogram (EMG) from a multipair esophageal electrodes and airflow derived from pneumotachography were recorded during overnight polysomnography in 13 patients with stable COPD recruited from outpatient clinic of First Affiliated Hospital of Guangzhou Medical College from May 2010 to May 2011. Changes in diaphragm EMG and ventilation during wakefulness and different sleep stages were observed.

Effect of expiratory load on neural inspiratory drive.

Background: Neural respiratory drive is usually measured during inspiration, even in patients with chronic obstructive pulmonary disease (COPD) in whom the primary physiological deficit is expiratory flow limitation. The purpose of the study was to test the hypothesis that inspiratory muscle neural respiratory drive could be used to assess expiratory load.

Methods: Ten healthy young men, (26 ± 4) years old, were asked to expire through a tube immersed in water where an expiratory load was required.