Effect of airway wall flexibility on clearance by simulated cough

Soland, Vincent; Brock, Glenn A.; King, Malcolm

doi:10.1152/jappl.1987.63.2.707

Cited by 13 publications

(4 citation statements)

References 4 publications

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“…Figure 6 shows flow, area and velocity curves in a representative trachea in the test chamber during an artificial cough. The reduction of cross-sectional area by dynamic compression during maximum flow contributed substantially to the achievement of high flow velocity [24]. The calculated velocity curve for a completely rigid trachea underscores the importance of this effect.…”

Section: Discussionmentioning

confidence: 81%

Theoretical and experimental basis for the development of a dynamic airway stent

Freitag¹,

Eicker²,

Linz³

et al. 1994

Eur Respir J

107

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Three major problems are currently associated with airway stents: mucostasis, formation of granulation tissue, and migration. We wanted to determine whether these problems could be solved by a different stent design. Based on theoretical considerations of an idealized trachea, we developed a dynamic bifurcation stent made of silicone which incorporates horseshoe-shaped steel struts. A flexible posterior membrane enables dynamic compression during cough, whilst the clasps maintain the airway lumen in the face of external compression. The design of the stent cast was based upon computed tomographic (CT)-scan studies of the central airways. Its complex shape provides a smoother distribution of pressure on the mucosa; thereby, lowering the stimulus for granulation formation. The bronchial limbs saddle on the carina, preventing displacement. The mechanical behaviours of the new stent and two commercially available stents were compared in an ex-vivo model, utilizing freshly excised tracheae and new visualization techniques. Dynamic (artificial coughs) and static loads (simulating tumour compression or pleural pressures) were applied on excised human tracheae with different stents. Our dynamic stent preserved effective compression of the posterior membrane in response to cough, and also provided lumen stability against extrinsic compression. In comparison, the two commercially available stents did not provide both functions equally well. In conclusion, our newly designed dynamic bifurcation stent shows characteristics which should prove useful in avoiding problems currently associated with airway stents.

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Section: Discussionmentioning

confidence: 81%

Theoretical and experimental basis for the development of a dynamic airway stent

Freitag¹,

Eicker²,

Linz³

et al. 1994

Eur Respir J

107

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show abstract

“…However, during cough, the trachea can contract and relax, due to tracheal wall flexibility. The effect of airway wall flexibility on the clearance of mucus-like gels has been analysed by Soi.AND et al (16) who demonstrated that the efficiency of cough clearance is directly related to airway wall flexibility, the higher the flexibility, the more efficient the clearance. In fact, the rapid successive cough manoeuvres that we carried out are somewhat different from that existing in vivo where there is a decrease in peak flow rate per cough in parallel with the fall in lung volume.…”

Section: Discussionmentioning

confidence: 99%

Role of simulated repetitive coughing in mucus clearance

Zahm

King²,

Duvivier³

et al. 1991

Eur Respir J

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The role of repetitive simulated coughing on the clearance of gel mucus simulant was investigated in vitro, by using a simulated cough machine. The repetition of cough induced a significant increase (p less than 0.01) in mucus simulant clearance (139.3 +/- 78.7 mm) in comparison to a single cough (24.9 +/- 27.5 mm). Moreover, the increase in frequency of the repetitive coughing induced a marked and significant increase in mucus simulant clearance (75.4 +/- 51.1 mm and 139.3 +/- 78.7 mm at 0.1 Hz and 1.6 Hz frequency, respectively). A significant (p less than 0.05) correlation was observed between the percentage increase of clearance and both shear-thinning index (r = 0.62) and the thixotropic index (r = 0.63). These results suggest that the shear-dependent properties of mucus, associated with a repetitive coughing, may increase the efficiency of mucus clearance by air flow mechanisms.

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“…In those studies, a flexible bottom wall was incorporated in the model trachea. 27 When air pressure outside the tracheal model wall (as in the intrathoracic airways) was more positive than inside, the wall was pushed inward during the cough maneuver. This had the effect of accelerating the airflow, enhancing clearance.…”

Section: Fig 1 Effects Of Flutterா Valve Oscillations (30 Min) and mentioning

confidence: 99%

Effects of sputum oscillations and rhDNase in vitro: A combined approach to treat cystic fibrosis lung disease

Dasgupta¹,

Brown²,

King³

1998

Pediatr. Pulmonol.

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Mucolytic treatment with rhDNase is part of the current therapy for cystic fibrosis (CF) lung disease. The Flutter® valve, a device for enhancing airway mucus clearance, has recently been approved for use in CF patients. Exhalation through the Flutter® valve leads to oscillations of expiratory airflow, improving mucus viscoelasticity and stimulating clearance. The goal of our in vitro study was to evaluate the individual and combined effects of Flutter® valve oscillations and rhDNase treatment on the viscoelastic (rheological) properties of CF sputum. Sputum specimens were collected from 19 CF patients and subjected to the following protocols: (1) baseline sample with no treatment applied; (2) application of oscillations generated by airflow through the Flutter® valve; (3) incubation at 37°C for 30 min with 10% vol/wt rhDNase (Pulmozyme®) to achieve a final concentration of 2.5 μg/mL (∼100 nM); (4) combination of Flutter® valve oscillations and 10% vol/wt normal saline (0.9% NaCl); (5) combination of Flutter® valve oscillations and 10% vol/wt rhDNase at 2.5 μg/mL final concentration. For each protocol, the mucus rigidity index (log G* at 1 rad/s) was measured at baseline and at 30 min. Values are presented as mean ±SEM. The cough clearability index (CCI) was computed from measurements of mucus viscoelasticity, based on relationships established in model studies. Flutter® valve treatment alone did not result in a significant reduction in the rigidity of CF sputum (2.24 ± 0.13 vs. 2.11 ± 0.13, P = 0.19), nor did rhDNase (2.5 μg/mL) alone, although we have previously shown (Pediatr. Pulmonol. 1995; 20:78) that both of these treatments reduce sputum spinnability, which is more sensitive to molecular weight reduction. In comparison to individual treatments, combined treatment with Flutter® valve oscillations and rhDNase significantly reduced the mucus rigidity to 1.85 ± 0.19 from 2.24 ± 0.13 (P < 0.001), consequently increasing the predicted clearability of the sputum (from 1.09 ± 0.26 to 1.83 ± 0.48, P = 0.012). These in vitro results suggest that a combination of biochemical treatment (e.g., DNase) and mechanical oscillation may have a better therapeutic potential for mucus clearance in CF lung disease. Pediatr Pulmonol. 1998; 26:250–255. © 1998 Wiley‐Liss, Inc.

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Effect of airway wall flexibility on clearance by simulated cough

Cited by 13 publications

References 4 publications

Theoretical and experimental basis for the development of a dynamic airway stent

Theoretical and experimental basis for the development of a dynamic airway stent

Role of simulated repetitive coughing in mucus clearance

Effects of sputum oscillations and rhDNase in vitro: A combined approach to treat cystic fibrosis lung disease

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