François Bellemare

The Epworth Sleepiness Scale: self-administration versus administration by the physician, and validation of a French version.

BACKGROUND/OBJECTIVES The Epworth Sleepiness Scale (ESS) measures sleepiness and is used for, among others, patients with obstructive sleep apnea (OSA). The questionnaire is usually self-administered, but may be physician administered. The aim was to compare the two methods of administration and to validate a French version. METHODS Consecutive patients presenting to the sleep clinic at a tertiary care centre completed a self-administered questionnaire containing the ESS. During the medical interview the same day, one of three pulmonologists who specialized in sleep medicine administered the ESS. Correlations with the apnea-hypopnea index and mean sleep latencies were used to assess construct validity, while results of previous self-administered ESS questionnnaires in untreated and recently treated OSA patients were used to test reproducibility and longitudinal construct validity, respectively. RESULTS In OSA patients, the ESS weakly correlated with the apnea-hypopnea index (r=0.224; P=0.05; n=120) and negatively with mean sleep latency. For untreated patients (test-retest), the mean (+/- SD) average score was unchanged (10.3+/-6.0 to 10.8+/-6.5; P=0.35; n=56) after a median of seven months. With continuous positive airway pressure use, the mean score decreased from 12.4+/-6.8 to 7.6+/-5.0 after 40.2 months (P<0.0001; n=68). For all subjects, the ESS score obtained by the physician was less than that of the self-administered result (9.4+/-5.9 versus 8.5+/-5.8; P<0.0001 [paired t test]; n=188). CONCLUSIONS In a sleep clinic population, the French version of the ESS performed similarly to the English version. However, the systematic underscoring during physician administration may be important to consider in the research setting if questionnaire administration methods are not consistent.

Temporal relation between Acoustic and Force responses at the adductor pollicis during nondepolarizing neuromuscular block

BACKGROUND Contracting muscle emits sounds. The purpose of this study was to compare the time course of muscular paralysis at the adductor pollicis muscle (AP) with use of acoustic myography and mechanomyography. METHODS Thirteen elective surgery patients, American Society of Anesthesiologists physical status I, received rocuronium (0.6 mg/kg intravenously) as a bolus dose during general anesthesia. Force of AP was measured with use of a strain gauge, and sounds were recorded simultaneously with use of a small condenser microphone fixed on the palmar surface of the hand over the AP. Supramaximal stimulation was applied to the ulnar nerve at 0.1 Hz for 45-60 min. In seven patients, the response to train-of-four stimulation was also recorded during recovery. RESULTS Force and sounds both were equally sensitive in measuring maximum block. The relation between sound and force was curvilinear, with good agreement near 0 and 100% and acoustic response exceeding mechanical response at intermediate levels of block. The acoustic signal had a slower onset and a faster recovery than the force response. The fade response of sound to train-of-four stimulation also recovered faster than that of force. CONCLUSION Acoustic myography is an alternative method to monitor muscular paralysis that is easy to set up and applicable to most superficial muscles. However, the time course of relaxation at AP using acoustic myography differs from the time course of force relaxation. Therefore, these two methods are not equivalent when applied to AP.

Sexual dimorphism of human ribs

The volume of the rib cage is about 10% smaller in females than in males having the same height although the reason for this is presently unclear. The cranio-caudal inclination of ribs is greater in females than males but the length of ribs has not previously been compared between the sexes. In 23 males and 23 females studied at necropsy, body length, the length of the upper and lower limbs and the length of the thoracic spine were all smaller in females but the ratios of upper and lower limb lengths to body length and of thoracic spine length to body length were not different. By contrast, the lengths of the third, sixth and ninth ribs were not significantly different between males and females and the ratios of rib length to body length were all significantly greater in females. We conclude that in females the ribs grow longer in relation to the axial skeleton than in males.

Effects of abdominal distension on breathing pattern and respiratory mechanics in rabbits

The effects of acute abdominal distension (AD) on the electromechanical efficiency (Eff) of the inspiratory muscles were investigated in anesthetized rabbits by recording the electrical activity (A), pressure (P) exerted by the diaphragm (di) and parasternal intercostal muscles (ic), and lung volume changes when an abdominal balloon was inflated to various degrees. Eff,ic increased with increasing AD both in supine and upright postures. In upright rabbits Eff,di increased for intermediate but decreased at higher levels of AD, whilst it decreased at all levels of AD in supine rabbits. Tidal volume (VT) response followed that of Eff,di. Tonic Aic and Adi and inspiratory prolongation were elicited by AD. The effects of these neural mechanisms, acting to limit end-expiratory lung volume and VT changes, were however small since vagotomy prevented tonic Adi and inspiratory prolongation and reduced tonic Aic, but changed lung volume responses to AD only little. Hence, reduced respiratory system compliance and changes in inspiratory muscle electromechanical efficiency dominate lung volume responses to acute AD.

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 Spo2 (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 ⩾4% fall in Spo2 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 ⩾4% fall in Spo2 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 Spo2 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.

Time-frequency analysis of the muscle sound of the human diaphragm.

The time—frequency characteristics of muscular sounds (phonomyogram) produced by the contraction of the human diaphragm under various contractile states is evaluated with the cone-kernel distribution. The results show that the instantaneous frequency of the phonomyogram of the diaphragm has a high cross-correlation (an average of 0.91±0.06) with the transdiaphragmatic pressure, with a delay varying between 25 and 35 ms. The instantaneous frequency response of the phonomyogram of the diaphragm shows a behaviour similar to that of the frog muscle; it rapidly rises and then fades out. However, the maximum of the instantaneous frequency of the phonomyogram of the diaphragm is not proportional to the maximum of the transdiaphragmatic pressure. This analysis also demonstrates the usefulness of the cone-kernel distribution for studying frequency-modulated signals like the muscular sound signals.

Sternum Length and Rib Cage Dimensions Compared with Bodily Proportions in Adults with Cystic Fibrosis

BACKGROUND A greater structural expansion of the rib cage in females compared with males has been described in cystic fibrosis (CF) patients; however, conflicting data exist as to whether an elongation of the bony ribs and sternum contributes to this expansion. OBJECTIVES To compare height-adjusted anthropometric measures and sternum length between a group of normal subjects and a group of CF patients of both sexes. METHODS Anthropometric measurements including body weight, height, upper and lower limb lengths, biacromial distance and pelvic width were measured in the standing position in 30 CF patients (13 males) and 28 normal subjects (14 males). Body surface measurements of anterior-posterior and lateral diameters of the rib cage at functional residual capacity, and sternum length were also obtained. RESULTS Compared with normal subjects, CF patients had lower body weight, shorter standing height and shorter height-adjusted upper and lower limb lengths. Rib cage diameters were greater in CF patients than in normal subjects of either sex, but height-adjusted sternum length was not different. CONCLUSION Significant differences in bodily proportions were found between normal subjects and CF patients, suggesting a differential growth pattern for the trunk and limbs. However, increased rib cage dimensions with lung hyperinflation and airway obstruction was not associated with an elongation of the sternum.

Influence of abdomen on respiratory mechanics in supine rabbits

Previous studies showed that abdominal evisceration has no effect on respiratory system compliance. We hypothesized that this could be related to lung distortion in eviscerated animals. Methods were developed for continuous recording of pleural pressure (Ppl) at various sites over the costal (co) and diaphragmatic lung surface (di) in acutely and chronically instrumented rabbits. We compared deltaPpl,co and deltaPpl,di recorded at mid-lung height during inflations in anesthetized, paralyzed supine rabbits before and after evisceration. Cranial and caudal deltaPpl.co were the same under all conditions. In intact animals, deltaPpl.co and deltaPpl,di were equal at all inflation volumes, whilst in eviscerated animals, deltaPpl,di were smaller than deltaPpl,co, the difference increasing with lung inflation. At any given volume, rib cage circumference (Crc) was smaller after evisceration, but the Crc deltaPpl,co relationship remained unchanged. These results are indicative of non-uniform lung expansion after evisceration and are consistent with model predictions based on cylindrical deformation and lung stress-strain relationship. This deformation should mimic the effect of a reduced lung compliance, keeping respiratory system compliance of eviscerated animals nearly normal. Similar deformation should have occurred also in intact rabbits during strong inspiratory efforts and in the erect posture, because lower Ppl,di than Ppl,co values were observed at the same lung height under these conditions.

Wireless esophageal catheter dedicated to respiratory diseases diagnostic

We present the design and test of a portable wireless catheter system combining the simultaneous assessment of the transdiaphragmatic pressure and EMG of the diaphragm. The esophageal catheter includes two micro fabricated pressure sensors and five platinum ring electrodes. The low noise analog front-end features an electrode DC mismatch correction circuitry, a selectable gain (58 dB-97 dB) as well as a high CMRR (80.3 dB). Pressure signals are sampled at 1 kHz while EMG at 4 kHz. The data is transmitted over a wireless Bluetoothreg connection towards a computing host to display the received signals in real time. Testing of the device demonstrates its reliability to process pressure and EMG signals and to be used as a stand-alone respiratory parameters assessment device

Effects of lung volume and fatigue on evoked diaphragmatic phonomyogram in normal subjects.

BACKGROUND: A diaphragmatic phonomyogram (PMG) evoked by maximal phrenic nerve stimulation at end expiratory lung volume (FRC) has been previously described as a good index of changes in diaphragmatic contractility with fatigue. A study was undertaken to assess whether this conclusion could be extended to different lung volumes. METHODS: Diaphragmatic compound motor action potentials (CMAPs) were recorded on each side of the chest by the means of surface electrodes placed over the eight intercostal spaces in five healthy subjects. Diaphragmatic PMGs from both sides were recorded with condenser microphones fixed to the skin close to the CMAP recording electrodes. Oesophageal and gastric balloon tipped catheters were employed to measure transdiaphragmatic pressure twitches (TwPDI) which served as the standard measure of changes in diaphragmatic contractility. PMG and TwPDI responses were compared at different lung volumes over inspiratory capacity both before and after fatiguing inspiratory resistive loading. RESULTS: No consistent relationship was found in different subjects or on different days in the same subject between PMG and lung volume or between PMG and TwPDI. However, the PMG:CMAP ratio from both sides at any given lung volume decreased after fatigue in roughly the same proportion as the TwPDI. CONCLUSIONS: These results show that, although PMG can detect changes in diaphragmatic contractility caused by fatigue in normal subjects, lung volume changes need to be controlled and each subject should serve as his or her own control.