Acoustic estimation of the impact of a single dive using a closed-type breathing apparatus on the ventilatory function of the human lungs

Diving negatively affects the human respiratory system, especially if an oxygen breathing apparatus is used. The spirometry indices generally used to estimate the ventilatory function of the lung have a poor sensitivity to the toxic effect of hyperbaric hyperoxia. The goal of this study was to estimate the possibilities of using the forced expiratory (FE) tracheal noise duration. The study was done on 48 divers who had been tested before and after a single dive.     

The effects of breathing pattern training on ventilatory function in patients with COPD

The purpose of this study was to assess the effects of a particular breathing pattern training (BPT) on forced expiratory volume during the first second (FEV₁) and forced vital capacity (FVC) in patients with chronic obstructive pulmonary disease (COPD). The subjects adjusted each breath to a target breath displayed on a video screen, by using visual feedback. This target was chosen in an individual sample recorded at rest. We used a randomized, controlled group design. Twenty patients with stable COPD, FEV₁ less than 1.5 liters, undergoing a traditional rehabilitation program were randomly assigned to the BPT group or to the control group. Each BPT subject underwent 30–35 training sessions spread out over four weeks, in addition to the traditional program. FEV₁ and FVC were performed before and after this program. ANOVAs showed that FEV₁ and FVC significantly improved in BPT subjects, with a mean percent increase of 22% and 19%, respectively. Corresponding changes in controls were not significant. This study showed short-term increases in FEV₁ and FVC in COPD patients practicing BPT in addition to respiratory rehabilitation, in comparison with controls. Further studies should incorporate outcome data to clarify the mechanisms and the duration of this effect.The authors express their gratitude to Philippe Carrias, Elizabeth Maclet, Françoise Tulane, and Bernard Cossalter for their contribution to this study, as well as to Michèle Delaire for her technical assistance.     

Effect of paced breathing on ventilatory and cardiovascular variability parameters during short-term investigations of autonomic function

Paced breathing (PB) around 0.25 Hz has been advocated as a means to avoid confounding and to standardize measurements in short-term investigations of autonomic cardiovascular regulation. Controversy remains, however, as to whether it causes any alteration in autonomic control. We addressed this issue in 40 supine, middle-aged, healthy volunteers by assessing the changes induced by PB (0.25 Hz for 8 min) on 1) ventilatory parameters, 2) the indexes of autonomic control of cardiovascular function, and 3) the spectral indexes of cardiovascular variability. Subjects were grouped into group 1 (n = 31), if spontaneous breathing was regular and within the high-frequency (HF) band (0.15-0.45 Hz), or group 2 (n = 9), if it was irregular or slow (< 0.15 Hz). In both groups, PB was accompanied by an increase in minute ventilation (both groups, P < 0.01), whereas tidal volume increased only in group 1 (P = 0.0003). End-tidal CO2 decreased by [median (lower quartile, upper quartile)] -0.2 (-0.5, -0.1)% (group 1, P < 0.0001) and -0.6 (-0.8, -0.5)% (group 2, P = 0.008). Mean R-R interval and systolic and diastolic pressure remained remarkably stable (all P > or = 0.13, both groups). No significant changes were observed in spectral indexes of R-R and pressure variability (all P > or = 0.12, measured only in group 1 to avoid confounding), except in the HF power of pressure signals, which significantly increased (all P < 0.05) in association with increased tidal volume. In conclusion, PB at 0.25 Hz causes a slight hyperventilation and does not affect traditional indexes of autonomic control or, in subjects with spontaneous breathing in the HF band, most relevant spectral indexes of cardiovascular variability. These findings support the notion that PB does not alter cardiovascular autonomic regulation compared with spontaneous breathing.     

Expression of endothelial selectin ligands on human leukocytes following dive

The fact that impaired endothelial-dependent vasodilatation after scuba diving often occurs without visible changes in the endothelial layer implies its biochemical origin. Since Lewis x (CD15) and sialyl-Lewis x (CD15s) are granulocyte and monocyte carbohydrate antigens recognized as ligands by endothelial selectins, we assumed that they could be sensitive markers for impaired vasodilatation following diving. Using flow cytometry, we determined the CD15 and CD15s peripheral blood mononuclear cells of eight divers, 30 mins before and 50 mins after a single dive to 54 m for 20 mins bottom time. The number of gas bubbles in the right heart was monitored by ultrasound. Gas bubbles were seen in all eight divers, with the average number of bubbles/cm(2) 1.9 +/- 1.9. The proportion of CD15 + monocytes increased 2-fold after the dive as well as the subpopulation of monocytes highly expressing CD15s. The absolute number of monocytes was slightly, but not significantly, increased after the dive, whereas the absolute number of granulocytes was markedly elevated (up to 61%). There were no significant correlations between bubble formation and CD15 + monocyte expression (r = - 0.56; P = 0.17), as well as with monocytes highly expressing CD15s (r = 0.43; P = 0.29). This study suggests that biochemical changes induced by scuba diving primarily activate existing monocytes rather than increase the number of monocytes at a time of acute arterial endothelial dysfunction.     

Fetal breathing movements and lung maturation in the congenitally abnormal human fetus

Fetal breathing movements have been studied in conjunction with features of anatomical and biochemical development of the lung at birth in fetuses with congenital abnormalities affecting the respiratory system. Total absence of fetal breathing movements or abnormal fetal breathing movements were associated with lung hypoplasia and failure of normal surfactant release into saline extracts of lung fluid. Surfactant synthesis was demonstrated regardless of the presence or absence of fetal breathing movements. The study supports the hypothesis that normal fetal breathing movements are important for fetal lung development and suggests that surfactant synthesis and its release are independent. The latter process may be dependent upon fetal breathing movements while the former is not.     

The pattern of breathing and the ventilatory response to breathing through a tube and to physical exercise in sport divers

Well-trained divers can be expected to differ from healthy controls in their ventilatory response to breathing through a tube and to physical exercise. Therefore, we measured their minute ventilation (VE) at rest and during breathing through a tube combined with two levels of physical exercise (1 or 2 W.kg body weight-1). For breathing through a tube an additional dead space of 600 ml was used. All divers were trained in the breath-hold technique and in the use of the breathing apparatus. Their mean period of training as divers was 9 +/- 6 years. The approximate age of the subjects was 25 years. The pattern of breathing and the oxygen uptake were measured by spirometer, the end-tidal concentration of CO2 was measured and all experiments were carried out above sea level. The ventilation of the divers at rest was comparable to that of the controls. During physical exercise it was smaller whether during breathing through a tube or not. The inadequate increase of VE during exercise in divers was associated with hypercapnia only at a higher physical work intensity (of 2 W.kg-1). This finding is interpreted as a lower chemoregulatory response to the combined stimuli of hypercapnia, hypoxia and physical exercise. In some situations significant bradypnoea and higher tidal volumes were found in the divers.     

Effect of atenolol on ventilatory and cardiac function in asthma.

The effects on ventilatory and cardiac function of atenolol, a new cardioselective beta-adrenoceptor blocking agent, were compared with those of practolol in a double-blind trial in 12 patients with asthma. Both drugs impaired ventilatory function--atenolol insignificantly and practolol significantly. Atenolol was if anything more cardioselective than practolol. Neither drug interfered significantly with the bronchodilator response to inhaled isoprenaline. Atenolol is suitable for use in patients for whom practolol would formerly have been chosen because of its cardioselectivity.     

Relationships between eupnoeic pattern of breathing and ventilatory control in man: I. Response to airways occlusion during active lung inflation.

The apnoeic response following interruption of the air flow at different levels of the inspiratory capacity (deltaVL) was studied in conscious children and adults. Changes in mouth pressure were used to measured the duration of the apnoe. The total duration of the interrupted breath (T1) was compared to mean value of the ventilatory period of the five preceding breaths (T0). A monoexponential regression could be fitted to the relationship between T1/T0 ratio and change in lung volume (deltaVL) measured at the onset of interruption: T1/T0=k-exp (S-deltaVL), S begin the sensitivity of the response to lung inflation. When T1/T0=1, the intrathoracic lung volume was called threshold volume (VTh.L.). The parameters S and VTh.L. were used for characterization of the individual importance of the Breuer-Hering inspiratory-inhibitory reflex (B.H. reflex). The high reproducibility of the T1/T0 vs. deltaVL relationship in many subjects showed the light influence of voluntary control on apnoea's duration. In each subject, S and VTh.L. were compared with ventilatory variables measured during eupnoea. A fast pattern of breathing (i.e. small inspired volume and short inspiratory duration) was associated with high value of S and low VTh.L. Moreover VTh.L. was near the tidal volume range in subjects where the B.H. reflex was the more potent. Thus, vagal afferents relating to this reflex could modulate the eupnoeic pattern of some subjects.     

Temperature effect on the human dive response in relation to cold water near-drowning

To facilitate analysis of mechanisms involved in cold water near-drowning, maximum breath-hold duration (BHD) and diving bradycardia were measured in 160 humans who were submerged in water temperatures from 0 to 35 degrees C at 5 degrees C intervals. For sudden submersion BHD was dependent on water temperature (Tw) according to the equation BHD = 15.01 + 0.92Tw. In cold water (0-15 degrees C), BHD was greatly reduced, being 25-50% of the presubmersion duration. BHD after brief habituation to water temperature and mild, voluntary hyperventilation was more than double that of sudden submersion and was also dependent on water temperature according to the equation BHD = 38.90 + 1.70Tw. Minimum heart rate during both types of submersions (diving bradycardia) was independent of water temperature. The results are pertinent to accidental submersion in cold water and show that decreased breath-holding capacity caused by peripheral cold stimulation reduces the effectiveness of the dive response and facilitates drowning. These findings do not support the postulate that the dive response has an important role in the enhanced resuscitatibility associated with cold water near-drowning, thereby shifting emphasis to hypothermia as the mechanism for this phenomenon.     

Control of breathing in uremia: ventilatory response to CO2 after hemodialysis.

The mechanisms responsible for the transient respiratory alkalosis which follows clinical hemodialysis were evaluated by studying the ventilatory response to carbon dioxide in chronic uremic patients, and in unanesthetized normal and chronic uremic goats. A significant increase in sensitivity to CO2 was found in acidotic uremic patients immediately (within 30 min) following hemodialysis (P less than 0.01). Sensitivity to CO2 returned to the predialysis value within 24 h. Lung volume and maximal breathing capacity were unchanged. A similar increase in sensitivity to CO2 was seen in nonacidotic uremic goats following hemodialysis. In the goats, these changes in sensitivity could not be explained by changes in cerebrospinal fluid acid-base status. Adding sufficient urea to the dialysate to prevent a fall in plasma urea concentration, eliminated this increase in sensitivity to CO2 in both uremic patients and goats. These results suggests that the transient respiratory alkalosis following hemodialysis is due to an increase in the sensitivity of the ventilatory response to carbon dioxide and is a consequence of dialysis-induced osmotic disequilibrium.     

成年人脂肪体重、去脂体重和肺通气功能的关系

本文旨在研究分析成年人去脂体重(fat free mass,FFM)、脂肪体重(fat mass,FM)和肺通气功能的关系。随机抽取黑龙江省部分地区19~81岁健康成年人群1307人(男性372人,女性935人),测量身高、体重,采用身体成分仪和肺功能仪分别检测FFM、FM和肺通气功能,并采用Pearson相关分析、独立样本t检验和多元逐步回归等统计学方法分析FFM、FM和肺通气功能的关系。结果显示,无论性别,年龄均与脂肪体重指数(FM index,FMI)呈正相关(P0.001),去脂体重指数(FFM index,FFMI)和用力肺活量(forced vital capacity,FVC)、用力呼气一秒量(forced expiratory volume in one second,FEV1)、最高呼气流量(peak expiratory flow,PEF)、用力呼出25%肺活量时呼气流量(forced expiratory flow at25%of forcedvital capacity,FEF25%)均呈正相关(P0.01),FMI和FVC、FEV1、FEF75%呈负相关(P0.05)。男性FMI和最大呼气中段流量(maximal mid-expiratory flow,MMEF)呈负相关(P0.05)。无论性别,FFMI对于FVC作用大于FMI,而对于FEV1,男性FMI作用大于FFMI,女性则反之。无论性别,FFMI升高,PEF和FEF25%也升高,而FMI对二者无作用。无论性别,FMI升高,FEF75%降低,而FFMI对其无作用。FMI升高,男性MMEF降低,女性无明显改变。本研究结果表明,FFM和FM均是影响肺通气功能的独立因素,反映骨骼肌力的FFM与肺通气功能呈正相关,FM与肺通气功能呈负相关。FFM和FM对肺通气功能作用大小存在差别。     

Effects of health status on pressure-induced changes in phocid immune function and implications for dive ability

Journal of Comparative Physiology B - The ability of marine mammals to cope with environmental challenges is a key determining factor in strandings and successful release of rehabilitated animals....