The Mechanisms of Compensatory Responses of the Respiratory System to Simulated Central Hypervolemia in Normal Subjects

2014 ◽  
pp. 9-17 ◽  
Author(s):  
M. O. Segizbaeva ◽  
Zh. A. Donina ◽  
V. G. Aleksandrov ◽  
N. P. Aleksandrova
Keyword(s):  
Respiratory System ◽  
Normal Subjects ◽  
Compensatory Responses ◽  
Central Hypervolemia

Positive End-expiratory Pressure Improves Respiratory Function in Obese but not in Normal Subjects during Anesthesia and Paralysis 

1999 ◽  
Vol 91 (5) ◽  
pp. 1221-1221 ◽  
Author(s):  
Paolo Pelosi ◽  
Irene Ravagnan ◽  
Gabriella Giurati ◽  
Mauro Panigada ◽  
Nicola Bottino ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Chest Wall ◽  
Body Mass ◽  
Respiratory System ◽  
Respiratory Function ◽  
Normal Subjects ◽  
Intraabdominal Pressure ◽  
Morbidly Obese ◽  
Obese Patients ◽  
Positive End Expiratory Pressure

Background Morbidly obese patients, during anesthesia and paralysis, experience more severe impairment of respiratory mechanics and gas exchange than normal subjects. The authors hypothesized that positive end-expiratory pressure (PEEP) induces different responses in normal subjects (n = 9; body mass index < 25 kg/m2) versus obese patients (n = 9; body mass index > 40 kg/m2). Methods The authors measured lung volumes (helium technique), the elastances of the respiratory system, lung, and chest wall, the pressure-volume curves (occlusion technique and esophageal balloon), and the intraabdominal pressure (intrabladder catheter) at PEEP 0 and 10 cm H2O in paralyzed, anesthetized postoperative patients in the intensive care unit or operating room after abdominal surgery. Results At PEEP 0 cm H2O, obese patients had lower lung volume (0.59 +/- 0.17 vs. 2.15 +/- 0.58 l [mean +/- SD], P < 0.01); higher elastances of the respiratory system (26.8 +/- 4.2 vs. 16.4 +/- 3.6 cm H2O/l, P < 0.01), lung (17.4 +/- 4.5 vs. 10.3 +/- 3.2 cm H2O/l, P < 0.01), and chest wall (9.4 +/- 3.0 vs. 6.1 +/- 1.4 cm H2O/l, P < 0.01); and higher intraabdominal pressure (18.8 +/-7.8 vs. 9.0 +/- 2.4 cm H2O, P < 0.01) than normal subjects. The arterial oxygen tension was significantly lower (110 +/- 30 vs. 218 +/- 47 mmHg, P < 0.01; inspired oxygen fraction = 50%), and the arterial carbon dioxide tension significantly higher (37.8 +/- 6.8 vs. 28.4 +/- 3.1, P < 0.01) in obese patients compared with normal subjects. Increasing PEEP to 10 cm H2O significantly reduced elastances of the respiratory system, lung, and chest wall in obese patients but not in normal subjects. The pressure-volume curves were shifted upward and to the left in obese patients but were unchanged in normal subjects. The oxygenation increased with PEEP in obese patients (from 110 +/-30 to 130 +/- 28 mmHg, P < 0.01) but was unchanged in normal subjects. The oxygenation changes were significantly correlated with alveolar recruitment (r = 0.81, P < 0.01). Conclusions During anesthesia and paralysis, PEEP improves respiratory function in morbidly obese patients but not in normal subjects.

Techniques for measuring respiratory mechanics: an analytic approach with a viscoelastic model

1993 ◽  
Vol 74 (5) ◽  
pp. 2373-2379 ◽  
Author(s):  
A. M. Lorino ◽  
A. Harf
Keyword(s):  
Mechanical Ventilation ◽  
Mechanical Behavior ◽  
Respiratory System ◽  
Respiratory Mechanics ◽  
Homogeneous Model ◽  
Viscoelastic Model ◽  
Normal Subjects ◽  
Inspiratory Time ◽  
Airway Occlusion ◽  
Analytic Expressions

A homogeneous model with stress relaxation that is described by a pure viscoelastic component was recently proposed to describe the mechanical behavior of the respiratory system during mechanical ventilation (Bates et al. J. Appl. Physiol. 67: 2276–2285, 1989). With the use of this model, analytic expressions of the pressure in response to typical volume inputs are developed, and the recently published studies relating to the influence of the ventilatory pattern on respiratory mechanics are reviewed and analyzed. The analytic expression of pressure responses to rapid airway occlusion following constant-flow inflation and to sinusoidal volume oscillations allows prediction of most of the reported results. The theoretical analysis suggests that in normal subjects the observed flow and volume dependencies of respiratory mechanics are, in fact, illustrations of the dependence of the viscoelastic resistance on inspiratory time and respiratory frequency. Thus the homogeneous viscoelastic model appears suitable to describe respiratory system mechanical behavior under mechanical ventilation.

Effects of water immersion on plasma catecholamines in normal humans

1983 ◽  
Vol 54 (1) ◽  
pp. 244-248 ◽  
Author(s):  
M. Epstein ◽  
G. Johnson ◽  
A. G. DeNunzio
Keyword(s):  
Nervous System ◽  
Water Immersion ◽  
Plasma Catecholamines ◽  
Normal Subjects ◽  
Plasma Catecholamine ◽  
Normal Humans ◽  
Cardiopulmonary Receptors ◽  
Control Study ◽  
Central Hypervolemia ◽  
Stimulation Of

Recent evidence indicates that stimulation of cardiopulmonary receptors in experimental animals results in a diminution of autonomic nervous system activity. Water immersion to the neck (NI) results in a preferential central hypervolemia (CV); thus it might be anticipated that NI would alter plasma catecholamine levels. Because two earlier studies have yielded divergent findings, we designed the present study utilizing more updated methodology to determine whether NI alters plasma catecholamines in normal humans. Eight normal subjects were studied on two occasions; during a seated control study (C) and during 4 h of NI. Norepinephrine (NE) and epinephrine (E) levels, determined by radioenzymatic assay, were measured hourly. Despite the induction of a marked natriuresis and diuresis indicating significant CV, NI failed to alter plasma NE or E levels compared with those of either C or the corresponding prestudy 1.5 h. Furthermore, the diuresis and natriuresis varied independently of NE. The current findings suggest that the response of the sympathetic nervous system to acute volume alteration may differ from the reported response to chronic volume expansion.

scholarly journals Effects of High Frequency Chest Compression on Respiratory System Mechanics in Normal Subjects and Cystic Fibrosis Patients

1995 ◽  
Vol 2 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Richard L Jones ◽  
Richard T Lester ◽  
Neil E Brown
Keyword(s):  
Cystic Fibrosis ◽  
Airway Obstruction ◽  
Chest Compression ◽  
Respiratory System ◽  
High Frequency ◽  
Oscillation Frequency ◽  
Normal Subjects ◽  
Lung Mechanics ◽  
Normal Lung ◽  
Respiratory System Mechanics

OBJECTIVE: To investigate the short term effects of high frequency chest compression (HFCC) on several indices of respiratory system mechanics in normal subjects and patients with cystic fibrosis (CF).DESIGN: Comparative physiological approach. Subjects were blinded to 10 randomized HFCC settings (5, 10, 15, 20 and 25 Hz) with each applied at the lowest and at the highest background vest pressure.SETTING: Pulmonary function and lung mechanics laboratory, University of Alberta.PARTICIPANTS: Ten normal male volunteers (24.2±3.8 years) and 11 clinically stable CF patients (23.4±6.7 years). Normal subjects were nonsmokers who had normal lung function. The CF patients had a wide range of airway obstruction.INTERVENTIONS: HFCC was supplied by oscillating a pneumatic vest that covered the entire torso. Balloon tipped catheters were used to measure esophageal (Pes) and external chest wall (Pew) pressures. Changes in end-expiratory lung volume (EELV) during HFCC were measured from a spirogram and were compared with baseline functional residual capacity (FRC). The HFCC induced air movement al the mouth, oscillated tidal volume (Vosc), was measured by reverse plethysmography.RESULTS: Both normals and CF patients had similar changes in Pes and EELV. At the highest background vest pressure and at the higher oscillation frequencies, EELV decreased approximately 30% from the no-HFCC baseline FRC. Vosc decreased with increasing oscillation frequency but normals had higher Vosc than CF patients at each frequency. Conversion of Vose to flow (V˙osc) revealed that the highest Vosc occurred between 10 and 15 Hz for both normals and CF patients. Also, Vosc was dependent on the overall airway function. Low forced expired volume in 1 s resulted in low Vosc, especially when Vosc was measured during spontaneous expiration.CONCLUSIONS: CF patients with moderate or severe airway obstruction may gain maximal benefit from HFCC therapy when low vest pressure is used at an oscillation frequency of 10 to 15 Hz. The low vest pressure minimizes the decrease in EELV and 10 to 15 Hz maximizes Vosc.

Mechanism of detection of resistive loads in conscious humans

1992 ◽  
Vol 72 (6) ◽  
pp. 2267-2270 ◽  
Author(s):  
A. Puddy ◽  
G. Giesbrecht ◽  
R. Sanii ◽  
M. Younes
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Primary Source ◽  
Intrathoracic Pressure ◽  
Normal Subjects ◽  
Resistive Load ◽  
Load Detection ◽  
Elastic Load ◽  
Resistive Loads ◽  
Source Of Information

Conscious humans easily detect loads applied to the respiratory system. Resistive loads as small as 0.5 cmH2O.l-1.s can be detected. Previous work suggested that afferent information from the chest wall served as the primary source of information for load detection, but the evidence for this was not convincing, and we recently reported that the chest wall was a relatively poor detector for applied elastic loads. Using the same setup of a loading device and body cast, we sought resistive load detection thresholds under three conditions: 1) loading of the total respiratory system, 2) loading such that the chest wall was protected from the load but airway and intrathoracic pressures experienced negative pressure in proportion to inspiratory flow, and 3) loading of the chest wall alone with no alteration of airway or intrathoracic pressure. The threshold for detection for the three types of load application in seven normal subjects was 1.17 +/- 0.33, 1.68 +/- 0.45, and 6.3 +/- 1.38 (SE) cmH2O.l-1.s for total respiratory system, chest wall protected, and chest wall alone, respectively. We conclude that the active chest wall is a less potent source of information for detection of applied resistive loads than structures affected by negative airway and intrathoracic pressure, a finding similar to that previously reported for elastic load detection.

Menstrual Respiratory Changes and Symptoms

1980 ◽  
Vol 136 (5) ◽  
pp. 492-497 ◽  
Author(s):  
J. Damas-Mora ◽  
Lisa Davies ◽  
Wendy Taylor ◽  
F. A. Jenner
Keyword(s):  
Carbon Dioxide ◽  
Menstrual Cycle ◽  
Slow Wave ◽  
Respiratory System ◽  
Normal Subjects ◽  
Wave Activity ◽  
Slow Waves ◽  
Slow Wave Activity ◽  
Premenstrual Tension ◽  
Carbon Dioxide Sensitivity

SummaryThe duration of standardised overbreathing required to produce slow wave activity in the EEG during different phases of the menstrual cycle has been studied, and changes in carbon dioxide sensitivity of the respiratory system. Normal subjects developed slow waves more quickly and had more sensitive CO2 responses during the premenstrual/menstrual phases. This may be a factor contributing to premenstrual tension.

scholarly journals Compliance of the respiratory system and its components in health and obesity

1960 ◽  
Vol 15 (3) ◽  
pp. 377-382 ◽  
Author(s):  
A. Naimark ◽  
R. M. Cherniack
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Work Of Breathing ◽  
Normal Subjects ◽  
Respiratory Compliance ◽  
Elastic Resistance ◽  
Normal Individuals ◽  
Obese Subjects ◽  
The Difference ◽  
Mean Compliance

The compliance of the total respiratory system and its components was studied in 24 normal and 12 obese spontaneously breathing unanesthetized subjects. The mean compliance of the total respiratory system was .119 l/cm H2O in normal individuals, but was .052 l/cm H2O in obese subjects. The difference indicated an increased elastic resistance to distention. The compliance of the lung in obese individuals was not different from that of the normals. The compliance of the chest wall was .224 l/cm H2O in normal subjects and was .077 l/cm H2O in obese individuals. In contrast to normal subjects, total respiratory compliance was markedly reduced by recumbency in obese individuals. This was entirely due to a further increase in the resistance of the chest wall. A significant correlation was demonstrated between vital capacity and total respiratory compliance in normal and obese subjects. It has been estimated that of the increase in the mechanical work of breathing in obesity is due to elastic work done on the chest wall. Submitted on November 2, 1959

Compliance of the chest wall in chronic bronchitis and emphysema

1963 ◽  
Vol 18 (4) ◽  
pp. 707-711 ◽  
Author(s):  
R. M. Cherniack ◽  
A. Hodson
Keyword(s):  
Airway Obstruction ◽  
Chronic Bronchitis ◽  
Chest Wall ◽  
Respiratory System ◽  
Vital Capacity ◽  
Normal Subjects ◽  
Chest Wall Compliance ◽  
Paradoxical Finding ◽  
Wall Compliance ◽  
Work Done

The respiratory rate was found to be faster and the tidal volume lower than normal in patients with chronic bronchitis and emphysema. The compliance of the total respiratory system, the lungs, and the chest wall was measured in 11 normal subjects and 13 patients with chronic bronchitis, 11 of whom had also developed emphysema. The compliance of the total respiratory system was lower than in the normals in the patients with chronic bronchitis. This was entirely attributable to a reduction in the compliance of the chest wall, that of the lungs being similar to that of the normals. The vital capacity appeared to be related to the compliance of the total respiratory system and was reduced in the patients with chronic bronchitis and emphysema largely because of a diminished distensibility of the chest wall. It is suggested that the low chest wall compliance may explain the paradoxical finding of rapid shallow respirations in these patients with airway obstruction who theoretically would have been expected to breathe slowly and deeply. It is further suggested that the diminished distensibility of the chest wall in patients with chronic bronchitis and emphysema would necessitate an increase in the amount of work done in order to breathe and, therefore, likely contributes to the disability in this disease. Submitted on April 18, 1962

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