Frequency dependence of pulmonary and chest wall mechanics in young and adult cats

1994 ◽  
Vol 76 (5) ◽  
pp. 2037-2046 ◽  
Author(s):  
F. R. Shardonofsky ◽  
J. Sato ◽  
D. H. Eidelman
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Viscoelastic Model ◽  
Dynamic Compliance ◽  
Compartment Model ◽  
Volume Data ◽  
Chest Wall Mechanics ◽  
Tissue Resistance ◽  
Single Compartment Model ◽  
Adult Cats

The frequency (f) dependence of pulmonary and chest wall mechanics was assessed in nine kittens and four cats. Kittens and cats were anesthetized, paralyzed, and mechanically ventilated at various f between 0.13 and 1.6 Hz and 0.09 and 0.79 Hz, respectively. Resistance and dynamic compliance pertaining to the respiratory system (Rrs and Cdyn,rs), lungs (RL and Cdyn,L), and chest wall (RW and Cdyn,W) were estimated by fitting a single-compartment model to data obtained from regular ventilation. Static lung and chest wall compliances (Cst,L and Cst,W) were computed from quasi-static pressure-volume data. Lung tissue resistance (Rti) was estimated with alveolar capsules in open-chest animals. The f dependence of the two-compartment viscoelastic model of the respiratory system was assessed by computing the effective resistance [Rmod,rs(omega)] and compliance [Cmod,rs(omega)] from data obtained at the lowest experimental f. Both Cdyn,L and Cdyn,W decreased with increasing f in all animals. Cdyn,L/Cst,L and Cdyn,W/Cst,W were lower in kittens than in cats. RL and RW decreased markedly with f in all animals. Rti/RL showed a marked f dependence, its values being similar in both young and adult cats at their respective resting f. CstW/Cst,L ratio was higher in kittens than in cats. A better agreement was found between Cmod,rs(omega) and Cdyn,rs than between Rmod,rs(omega) and Rrs.

Low-frequency respiratory system resistance in the normal dog during mechanical ventilation

1991 ◽  
Vol 70 (4) ◽  
pp. 1536-1543 ◽  
Author(s):  
J. Sato ◽  
B. L. Davey ◽  
F. Shardonofsky ◽  
J. H. Bates
Keyword(s):  
Respiratory System ◽  
Viscoelastic Model ◽  
Complex Impedance ◽  
Low Frequency ◽  
Compartment Model ◽  
Mechanically Ventilated ◽  
The Real ◽  
Two Compartment Model ◽  
Single Compartment Model ◽  
Airways Resistance

The low-frequency resistances of the respiratory system, lung, and chest wall were investigated in four anesthetized paralyzed dogs mechanically ventilated at various frequencies between 0.08 and 0.83 Hz. The resistances were calculated by three different methods: 1) as the real part of the complex impedance obtained from regular ventilation data, 2) as the effective resistance of a two-compartment model fitted to the same data, and 3) as the resistance of a single-compartment model fitted to data obtained during sinusoidal ventilation at various frequencies. Alveolar pressures were measured by a closed-chest alveolar capsule technique and afforded a direct measure of airways resistance. All three resistance estimates were very similar and decreased markedly with frequency between 0 and 1 Hz. The real part of lung impedance at the higher frequencies investigated (around 5 Hz) closely approximated airways resistance, as predicted by the eight-parameter viscoelastic model of respiratory mechanics proposed by Bates et al. (J. Appl. Physiol. 67:2276-2285, 1989)

Effects of Thoracotomy on Respiratory System, Lung, and Chest Wall Mechanics

CHEST Journal ◽  
1993 ◽  
Vol 104 (6) ◽  
pp. 1882-1886 ◽  
Author(s):  
Ana Claudia M. Rodrigues ◽  
Lucio F. Pacheco Moreira ◽  
Cláudia L. De Souza ◽  
Paola Capparelli D. Pettersen ◽  
Paulo Hilário N. Saidiva ◽  
...  
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Chest Wall Mechanics

Total Respiratory System, Lung, and Chest Wall Mechanics in Sedated-Paralyzed Postoperative Morbidly Obese Patients

CHEST Journal ◽  
1996 ◽  
Vol 109 (1) ◽  
pp. 144-151 ◽  
Author(s):  
Paolo Pelosi ◽  
Massimo Croci ◽  
Irene Ravagnan ◽  
Pierluigi Vicardi ◽  
Luciano Gattinoni
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Morbidly Obese ◽  
Obese Patients ◽  
Chest Wall Mechanics

Effects of longitudinal laparotomy on respiratory system, lung, and chest wall mechanics

1992 ◽  
Vol 72 (5) ◽  
pp. 1985-1990 ◽  
Author(s):  
R. L. Santos ◽  
M. A. Santos ◽  
R. S. Sakae ◽  
P. H. Saldiva ◽  
W. A. Zin
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Guinea Pigs ◽  
Inspiratory Flow ◽  
Total Resistance ◽  
Abdominal Incision ◽  
Mechanically Ventilated ◽  
Flow Method ◽  
Chest Wall Mechanics ◽  
Before And After

In six sedated, anesthetized, paralyzed, and mechanically ventilated guinea pigs, total respiratory system (RT,rs), lung, and chest wall resistances and respiratory system (Est,rs), lung, and chest wall (Est,w) elastances were determined before and after longitudinal laparotomy. Furthermore the resistances were also split into their initial and difference components, with the former reflecting the Newtonian resistances and the latter representing the viscoelastic/inhomogeneous pressure dissipations in the system. For such purpose the end-inflation occlusion during constant inspiratory flow method was used. During laparotomy, a statistically significant increase in respiratory system difference resistance (from 0.086 to 0.101 cmH2O.ml-1.s) significantly augmented RT,rs (from 0.157 to 0.167 cmH2O.ml-1.s). The former was entirely secondary to a significant increase in chest wall difference resistance (0.019 to 0.034 cmH2O.ml-1.s), which naturally raised chest wall total resistance (from 0.030 to 0.047 cmH2O.ml-1.s). Est,rs and Est,w also increased (14.7 and 13.1%, respectively) after abdominal incision. It can be concluded that the midline xiphipubic laparotomy accompanied by the bilateral ventrodorsal infracostal incision increases RT,rs as a consequence of augmented chest wall difference resistance and Est,rs as a result of higher Est,w.

Influence of nonlinearities on estimates of respiratory mechanics using multilinear regression analysis

1994 ◽  
Vol 77 (3) ◽  
pp. 1185-1197 ◽  
Author(s):  
S. Kano ◽  
C. J. Lanteri ◽  
A. W. Duncan ◽  
P. D. Sly
Keyword(s):  
Respiratory System ◽  
Respiratory Mechanics ◽  
Compartment Model ◽  
Multilinear Regression ◽  
Multilinear Regression Analysis ◽  
Single Compartment ◽  
Dependent Component ◽  
Single Compartment Model ◽  
Volume Controlled ◽  
Pressure Controlled

To investigate the influence of nonlinearities on estimates of respiratory mechanics, differing patterns of mechanical ventilation patterns were analyzed from 8 puppies and 14 children. Respiratory mechanics were calculated using multiple linear regression to fit a linear single-compartment model, a volume-dependent single-compartment model (VDSCM), and a flow-dependent single-compartment model. The ratio of the compliance of the last 20% of the dynamic volume-pressure (V-P) curve to the total compliance (C20/C) and the contribution of a volume-dependent elastance to total elastance [%E2 = E2 (VT)/[(E1 + E2)VT], where E1 + E2 is total elastance, E2 is the volume-dependent component, and VT is tidal volume] were used as the indexes of over-distension. By positioning the dynamic loops on the static V-P curves, ventilation patterns were classified as overdistended or nonoverdistended. In the overdistended group, the C20/C was significantly lower (0.71 +/- 0.10 vs. 0.92 +/- 0.16; P < 0.0001) and %E2 was significantly higher (43.4 +/- 15.0 vs. 0.51 +/- 18.02%, P < 0.0001) than in the nonoverdistended group. The mode of ventilation (pressure controlled vs. volume controlled) and the resistive pressures that resulted in widening of the dynamic V-P loop were found to alter C20/C but not %E2. When the respiratory system was overdistended, i.e., ventilated up to the flattened portion of the V-P curve, the VDSCM gave more accurate estimates of respiratory mechanisms. Furthermore, %E2 calculated from VDSCM is a useful parameter for estimating respiratory system overdistension that is not affected by resistive pressures.

Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation

2001 ◽  
Vol 27 (8) ◽  
pp. 1328-1339 ◽  
Author(s):  
Sigurbergur Kárason ◽  
Søren Søndergaard ◽  
Stefan Lundin ◽  
Ola Stenqvist
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Chest Wall Mechanics ◽  
On Line

Changes in respiratory mechanics with age

1993 ◽  
Vol 74 (1) ◽  
pp. 369-378 ◽  
Author(s):  
C. J. Lanteri ◽  
P. D. Sly
Keyword(s):  
Respiratory System ◽  
Airway Resistance ◽  
Respiratory Mechanics ◽  
Compartment Model ◽  
Pressure Curve ◽  
Multilinear Regression ◽  
Cross Sectional Survey ◽  
Mechanically Ventilated ◽  
Single Compartment ◽  
Single Compartment Model

A cross-sectional survey involving 51 children, ranging in age from 3 wk to 15 yr, was performed to examine the changes in respiratory mechanics with age in mechanically ventilated children, using both a single-compartment model of the respiratory system and a more sophisticated two-compartment model. Children were studied while under anesthesia for urological surgery and were considered to have normal lungs. They were paralyzed and mechanically ventilated throughout measurements. Respiratory mechanics were measured during ventilation by applying a single-compartment model and by using multilinear regression to calculate dynamic compliance and respiratory system resistance (Rrs). We then used the interrupter technique, which allowed us to partition Rrs into airway resistance and a tissue viscoelastic component known as Pdif. A static volume-pressure curve was constructed from multiple occlusions made at different lung volumes throughout expiration, and static compliance was determined. Rrs and airway resistance decreased as height increased. There was a progressive increase in respiratory system compliance with height. Pdif fell in the first 2 yr of life and then subsequently increased after the age of approximately 5 yr.

The Effects of CO2on Respiratory Mechanics in Anesthetized Paralyzed Humans

2001 ◽  
Vol 94 (4) ◽  
pp. 604-610 ◽  
Author(s):  
Edgardo D’Angelo ◽  
Ida Salvo Calderini ◽  
Mario Tavola
Keyword(s):  
Carbon Dioxide ◽  
Chest Wall ◽  
Distress Syndrome ◽  
Respiratory Mechanics ◽  
Muscle Tone ◽  
Severe Brain Injury ◽  
Chest Wall Mechanics ◽  
Isoflurane Anesthesia ◽  
Tissue Resistance ◽  
Partial Pressures

Background There is little information concerning the carbon dioxide-related effects on respiratory mechanics in anesthetized, paralyzed subjects; however, hypocapnia or hypercapnia is often permitted in patients with severe brain injury or acute respiratory distress syndrome. Therefore, the carbon dioxide dependence of respiratory mechanics in healthy anesthetized, paralyzed subjects was investigated. Methods Interrupter resistance (Rint), additional tissue viscoelastic resistance (deltaR), and quasi-static elastance (Est) of lung (L) and chest wall were assessed by means of the rapid end-inspiratory occlusion method in two groups of seven healthy paralyzed subjects anesthetized with diazepam or isoflurane. They underwent ventilation with a fixed pattern and hyperoxic gas mixtures with different fractions of inspired carbon dioxide (FICO2) to produce a partial pressures of arterial carbon dioxide (PaCO2) of 24.4 +/- 3.4, 39.6 +/- 3.2, and 62 +/- 4.1 (SD) mmHg. Results Chest wall mechanics and Est,L were unaffected by PaCO2 changes. With diazepam anesthesia, Rint,L decreased linearly, with increasing PaCO2, from 2.3 to 1.4 cm H2O.s.l(-1), whereas deltaR,L decreased from 2 to 1.7 cm H2O.s.l(-1), though not significantly. With isoflurane anesthesia, the decrease of Rint,L (0.2 +/- 0.5 cm H2O.s.l(-1)) was not significant, and deltaRL remained unchanged. With diazepam, Rint,L was 45 (hypercapnia) to 110% (hypocapnia) greater than with isoflurane. Conclusions Changes of PaCO2 from 20-65 mmHg cause increasing bronchodilation in anesthetized, paralyzed subjects, this effect being attenuated or abolished by drugs (e.g., halogenated anesthetics) that depress smooth muscle tone substantially. The carbon dioxide bronchodilating effects are probably direct for peripheral structures and are paralleled by a tendency of lung tissue resistance to decrease. Because local PaCO2-related changes in bronchomotor tone promote VA/Q matching, this mechanism should be impaired by anesthetics that cause bronchodilation.

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