Abdominal muscle activity in obstructive sleep apnoeas.
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Abdominal Muscles↗
Biomedical subjects
S Sanci
Publications and source records attributed to S Sanci.
Expiratory timing in obstructive sleep apnoeas.
Diaphragmatic electromyogram was recorded during NREM sleep in 4 patients affected by obstructive sleep apnoea (OSA) syndrome in order to evaluate the behaviour of expiratory time (TE) in the course of the obstructive apnoea-ventilation cycle. The two components of TE, i.e. time of post-inspiratory inspiratory activity (TPIIA) and time of expiratory phase 2 (TE2) were separately analysed. TPIIA showed a short duration, with only minor variations, within the apnoea, while its duration was more variable and longer in the interapnoeic periods: the longest TPIIA values were associated with the highest inspiratory volumes in the same breaths. This behaviour seemed regulated according to the need of a more or less effective expiratory flow braking, probably as a result of pulmonary stretch receptors discharge. Conversely TE2 showed a continuous gradual modulation, progressively increasing in the pre-apnoeic period, decreasing during the apnoea and increasing in the post-apnoeic period: these TE2 variations seemed related to oscillations in chemical drive. These data show that TE in the obstructive apnoea-ventilation cycle results from a different modulation in its two components and suggest that both mechanical and chemical influences play a role in its overall duration.
Adult↗
Respiratory muscle oxygen consumption estimated by the diaphragm pressure-time index.
The O2 consumption of the respiratory muscles (VO2resp), work of breathing, and the time integral of the transdiaphragmatic pressure (TTdi) were measured in four normal subjects breathing against inspiratory resistance. A total of 39 runs were performed at mean tidal transdiaphragmatic pressures (Pdi) ranging from 15 to 53 cmH2O, respiratory frequencies from 3.5 to 22 breaths/min, and inspiratory time durations (TI) from 32 to 76% of the total breath duration. Each run was maintained from 8 to 17 min and the above parameters were kept constant by the subject via visual feedback of Pdi and TI with an oscilloscope. Most of the runs (36 of 39) were performed at TTdi values below those known to produce respiratory muscle fatigue. We found a strong linear correlation between the VO2resp and the TTdi (r = 0.74, P less than 0.001) and a weaker correlation between VO2resp and W (r = 0.31, P less than 0.05). These data suggest that TTdi is a good estimator of VO2resp over a wide range of respiratory patterns during inspiratory resistance breathing. The high variability seen in respiratory muscle efficiency during resistive breathing may be due to W not being a good indicator of the energy consumed by the respiratory muscles.
Adult↗
Obesity as a possible cause of respiratory failure in bilateral diaphragmatic paralysis. Case report.
An obese woman with respiratory failure and bilateral diaphragmatic paralysis, was studied in order to investigate the effects of weight loss on respiratory function during wakefulness and sleep. The patient was studied on 5 different occasions during which diurnal blood gas analysis, spirometry, CO2 rebreathing test, nitrogen wash-out test and a nocturnal polysomnographic study were performed. The follow-up period lasted 9 months, during which the patient progressively lost 19 kg. Progressive improvement in awake blood gas tensions (PaO2 + 21 mmHg, PaCO2 - 16 mmHg) as well as in nocturnal oxyhemoglobin saturation and transcutaneous PCO2 were observed; at the same time only minor changes in responsiveness to CO2 and in lung volumes were found. Conversely alveolar efficiency for CO2, obtained with the nitrogen wash-out test, in the supine posture increased from 81.7 to 90.5%, indicating an improvement in ventilation/perfusion ratio as a possible determinant of blood gas tension improvement during wakefulness and, as a consequence, also during sleep. We conclude that obesity is one possible cause of the occurrence of respiratory failure in bilateral diaphragmatic paralysis.
Adult↗
Limitations of applicability of current calibration procedures for respiratory inductive plethysmography.
Repeatability of calibration of the respiratory inductive plethysmograph and its stability with time were investigated in young healthy subjects. Eight were submitted to sequential runs of calibration-validation by simultaneous equation (SEM) and least squares methods (LSM) (30 in all): in five subjects, after an initial acceptable calibration, accuracy and precision were repeatedly checked over three hours (a total of 50 trials). Although mean errors for the whole sample seemed acceptably low (7.6%, SD 7.0 for SEM; 7.3%, SD 7.3 for LSM), a marked inconsistency of apparently comparable calibrations and a wide variability of results along but independently of the time in steady conditions (ranging up to 30%) were discovered. An analysis of factors interfering with the response of the equipment was made. The unreliability of the current calibration procedure was related to the fact that in most cases the calibration line derived by the change-in-posture technique, as currently applied, may not be adequately representative of the full range of relationships between the participant variables, as they occur in the selected posture. To overcome this difficulty, two suggestions are made: a) prolong the calibration procedure so as to use more data points, and b) investigate alternative procedures of calibration in any one position.
Adult↗
Evaluation of a test of density-dependence of the expiratory flows in the screening of peripheral airways obstruction.
A test of density-dependence of flow at 50% of vital capacity has been investigated in two groups of subjects (86 in total) in order to evaluate respectively: a) influences that on it may be exerted by altered mechanical properties of the lung in chronic airflow obstruction; b) accuracy and precision of the test in latent and clinical asthma. Lung elastic recoil pressure does not seem to be related to the intensity of density-dependence. Relationships between MEF50 on air and on He-O2, expressed as means of groups allow distinguish between each other, whereas a definite overlap between groups is patent; absolute flows, either on air or on He-O2 are quite satisfactorily reproducible, both in health and disease. Delta% MEF50 shows a good specificity but a poor sensitivity; reproducibility is unacceptable, unless when using on a qualitative scale of figure of 20% as borderline to distinguish subjects responders from non responders.
Airway Obstruction↗