Lung pressures and gas transport during high-frequency airway and chest wall oscillation

The major goal of this study was to compare gas exchange, tidal volume (VT), and dynamic lung pressures resulting from high-frequency airway oscillation (HFAO) with the corresponding effects in high-frequency chest wall oscillation (HFCWO). Eight anesthetized paralyzed dogs were maintained eucapnic with HFAO and HFCWO at frequencies ranging from 1 to 16 Hz in the former and 0.5 to 8 Hz in the latter. Tracheal (delta Ptr) and esophageal (delta Pes) pressure swings, VT, and arterial blood gases were measured in addition to respiratory impedance and static pressure-volume curves. Mean positive pressure (25–30 cmH2O) in the chest cuff associated with HFCWO generation decreased lung volume by approximately 200 ml and increased pulmonary impedance significantly. Aside from this decrease in functional residual capacity (FRC), no change in lung volume occurred as a result of dynamic factors during the course of HFCWO application. With HFAO, a small degree of hyperinflation occurred only at 16 Hz. Arterial PO2 decreased by 5 Torr on average during HFCWO. VT decreased with increasing frequency in both cases, but VT during HFCWO was smaller over the range of frequencies compared with HFAO. delta Pes and delta Ptr between 1 and 8 Hz were lower than the corresponding pressure swings obtained with conventional mechanical ventilation (CMV) applied at 0.25 Hz. delta Pes was minimized at 1 Hz during HFCWO; however, delta Ptr decreased continuously with decreasing frequency and, below 2 Hz, became progressively smaller than the corresponding values obtained with HFAO and CMV.

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Effects of mean airway pressure on gas transport during high-frequency ventilation in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.5.1896 ◽

1986 ◽

Vol 61 (5) ◽

pp. 1896-1902 ◽

Cited By ~ 5

Author(s):

Y. Yamada ◽

J. G. Venegas ◽

D. J. Strieder ◽

C. A. Hales

Keyword(s):

Lung Volume ◽

High Frequency ◽

Airway Pressure ◽

Gas Transport ◽

Blood Gases ◽

Co2 Production ◽

High Frequency Ventilation ◽

Mean Airway Pressure ◽

Arterial Blood ◽

Frequency Ventilation

In 10 anesthetized, paralyzed, supine dogs, arterial blood gases and CO2 production (VCO2) were measured after 10-min runs of high-frequency ventilation (HFV) at three levels of mean airway pressure (Paw) (0, 5, and 10 cmH2O). HFV was delivered at frequencies (f) of 3, 6, and 9 Hz with a ventilator that generated known tidal volumes (VT) independent of respiratory system impedance. At each f, VT was adjusted at Paw of 0 cmH2O to obtain a eucapnia. As Paw was increased to 5 and 10 cmH2O, arterial PCO2 (PaCO2) increased and arterial PO2 (PaO2) decreased monotonically and significantly. The effect of Paw on PaCO2 and PaO2 was the same at 3, 6, and 9 Hz. Alveolar ventilation (VA), calculated from VCO2 and PaCO2, significantly decreased by 22.7 +/- 2.6 and 40.1 +/- 2.6% after Paw was increased to 5 and 10 cmH2O, respectively. By taking into account the changes in anatomic dead space (VD) with lung volume, VA at different levels of Paw fits the gas transport relationship for HFV derived previously: VA = 0.13 (VT/VD)1.2 VTf (J. Appl. Physiol. 60: 1025–1030, 1986). We conclude that increasing Paw and lung volume significantly decreases gas transport during HFV and that this effect is due to the concomitant increase of the volume of conducting airways.

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Effects of High-Frequency Chest Wall Oscillation on Pleural Pressure and Oscillated Flow

Biomedical Instrumentation & Technology ◽

10.2345/0899-8205-42.6.485 ◽

2008 ◽

Vol 42 (6) ◽

pp. 485-491 ◽

Cited By ~ 6

Author(s):

Tal Zucker ◽

Neil M. Skjodt ◽

Richard L. Jones

Keyword(s):

Chest Wall ◽

Lung Volume ◽

Pulse Pressure ◽

High Frequency ◽

Esophageal Pressure ◽

Wall Pressure ◽

Pleural Pressure ◽

Significant Difference ◽

Esophageal Balloon ◽

Wall Oscillation

Abstract The effectiveness of high-frequency chest wall oscillation (HF-CWO) is directly related to the level of oscillated flow (vosc) in the airways. We used the Vest™ system to investigate the effects of HFCWO on chest wall and pleural pressures and we correlated these pressures to the resultant vosc. We also compared the latest HFCWO device with it predecessor. Different combinations of vest inflation pressure (background pressure) and oscillation frequency were randomly applied to 10 healthy volunteers. Chest wall pressure was determined using an air-filled bag under the vest and pleural pressure was estimated using an esophageal balloon. Reverse plethysmography was used to measure vosc at the mouth and a spirometer was used to measure changes in end-expired lung volume. We found a significant correlation between chest wall and pleural pressure with approximately one-third of the chest wall pressure transmitted into the pleural space. Mean esophageal pressure remained negative at all background pressure/frequency combinations. There was a significant correlation (p<0.0001) between the esophageal pulse pressure and vosc, which was highest at 15Hz regardless of the background pressure. The end-expired lung volume correlated with mean chest wall pressure. There was no significant difference between the two Vest™ systems. Since vosc dictates the effectiveness of HFCWO and since vosc is dependent on esophageal pulse pressure, which in turn is dependent on chest wall pulse pressure, it follows that the effectiveness of HFCWO is influenced by the ability to generate an effective chest wall pulse pressure.

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Increasing the Quantity of Lungs for Transplantation Using High-Frequency Chest Wall Oscillation: A Proposal

Progress in Transplantation ◽

10.1177/152692480201200406 ◽

2002 ◽

Vol 12 (4) ◽

pp. 266-274 ◽

Cited By ~ 6

Author(s):

Jane M. Braverman

Keyword(s):

Chest Wall ◽

High Frequency ◽

Critical Factor ◽

Chest Physiotherapy ◽

Arterial Blood Gas ◽

Arterial Blood ◽

Donor Lung ◽

Direct Data ◽

Wall Oscillation ◽

Better Than

The use of chest physiotherapy in donor patient management occupies an established place in most lung procurement protocols. Although its merits remain controversial and uncorroborated by direct data, some studies support the efficacy of chest physiotherapy in a variety of pulmonary patient populations. Comparative studies have shown that an airway clearance technology utilizing high-frequency chest wall oscillation clears pulmonary secretions as well as or better than chest physiotherapy, but has few of its contraindications and disadvantages. The implementation of high-frequency chest wall oscillation as part of the donor lung procurement protocol may increase rates of successful lung recovery by providing effective clearance of obstructing pulmonary secretions containing destructive by-products of inflammation and entrapped pathogens. High-frequency chest wall oscillation may also improve arterial blood gas values, a critical factor in increasing lung procurement rates. Although speculative, the benefits of high-frequency chest wall oscillation on donor lungs might improve perfusion and oxygenation of other organs for possible transplantation.

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Physiologic Evidence for High-Frequency Chest Wall Oscillation and Positive Expiratory Pressure Breathing in Hospitalized Subjects With Cystic Fibrosis

Physical Therapy ◽

10.1093/ptj/85.12.1278 ◽

2005 ◽

Vol 85 (12) ◽

pp. 1278-1289 ◽

Cited By ~ 31

Author(s):

Joan C Darbee ◽

Jamshed F Kanga ◽

Patricia J Ohtake

Keyword(s):

Cystic Fibrosis ◽

Lung Function ◽

Chest Wall ◽

High Frequency ◽

Gas Mixing ◽

Ventilation Distribution ◽

Oxyhemoglobin Saturation ◽

Arterial Blood ◽

Wall Oscillation ◽

Positive Expiratory Pressure

Abstract Background and Purpose. This investigation identified ventilation distribution, gas mixing, lung function, and arterial blood oxyhemoglobin saturation (Spo2) physiologic responses to 2 independent airway clearance treatments, high-frequency chest wall oscillation (HFCWO) and low positive expiratory pressure (PEP) breathing, for subjects who had cystic fibrosis (CF) and who were hospitalized during acute and subacute phases of a pulmonary exacerbation. Subjects. Fifteen subjects with moderate to severe CF were included in this study. Methods. Subjects performed single-breath inert gas tests and spirometry before and immediately after HFCWO and PEP breathing at admission and discharge. Arterial blood oxyhemoglobin saturation was monitored throughout each treatment. Results. At admission and discharge, PEP breathing increased Spo2 during treatment, whereas HFCWO decreased Spo2 during treatment. Ventilation distribution, gas mixing, and lung function improved after HFCWO or PEP breathing. Discussion and Conclusion. High-frequency chest wall oscillation and PEP breathing are similarly efficacious in improving ventilation distribution, gas mixing, and pulmonary function in hospitalized people with CF. Because Spo2 decreases during HFCWO, people who have moderate to severe CF and who use HFCWO should have Spo2 monitored during an acute exacerbation.

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Effects of Changes in Lung Volume on Oscillatory Flow Rate During High-Frequency Chest Wall Oscillation

Canadian Respiratory Journal ◽

10.1155/2007/514573 ◽

2007 ◽

Vol 14 (3) ◽

pp. 153-158 ◽

Cited By ~ 2

Author(s):

Scott J Butcher ◽

Michal P Pasiorowski ◽

Richard L Jones

Keyword(s):

Airway Obstruction ◽

Chest Wall ◽

Flow Rate ◽

Lung Volume ◽

High Frequency ◽

Healthy Subjects ◽

Oscillatory Flow ◽

Airway Disease ◽

Wall Oscillation ◽

Oscillation Frequencies

BACKGROUND: The effectiveness of high-frequency chest wall oscillation (HFCWO) in mucolysis and mucous clearance is thought to be dependant on oscillatory flow rate (Fosc). Therefore, increasing Fosc during HFCWO may have a clinical benefit.OBJECTIVES: To examine effects of continuous positive airway pressure (CPAP) on Fosc at two oscillation frequencies in healthy subjects and patients with airway obstruction.METHODS: Five healthy subjects and six patients with airway obstruction underwent 12 randomized trials of HFCWO (CPAP levels of 0 cm H2O, 2 cm H2O, 4 cm H2O, 6 cm H2O, 8 cm H2O and 10 cm H2O at frequencies of 10 Hz and 15 Hz) within a body plethysmograph, allowing measurements of changes in lung volume. Fosc was measured by reverse plethysmography using a 20 L isothermic chamber near the mouth. At the end of each randomized trial, an inspiratory capacity manoeuvre was used to determine end-expiratory lung volume (EELV).RESULTS: EELV increased significantly (P<0.05) with each level of CPAP regardless of oscillation frequency. Fosc also significantly increased with CPAP (P<0.05) and it was correlated with EELV (r=0.7935, P<0.05) in obstructed patients but not in healthy subjects (r=0.125, P=0.343). There were no significant differences in perceived comfort across the levels of CPAP.CONCLUSIONS: Significant increases in Fosc with CPAP-induced increases in lung volume were observed, suggesting that CPAP may be useful as a therapeutic adjunct in patients who have obstructive airway disease and who require HFCWO.

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Large Lung Volumes Delay the Onset of the Physiological Breaking Point During Simulated Diving

Frontiers in Physiology ◽

10.3389/fphys.2021.731633 ◽

2021 ◽

Vol 12 ◽

Author(s):

Paul F. McCulloch ◽

B. W. Gebhart ◽

J. A. Schroer

Keyword(s):

Lung Volume ◽

Blood Gases ◽

Breaking Point ◽

Breath Holding ◽

Breath Hold ◽

Lung Volumes ◽

Arterial Blood ◽

Face Immersion ◽

Residual Capacity ◽

End Tidal

During breath holding after face immersion there develops an urge to breathe. The point that would initiate the termination of the breath hold, the “physiological breaking point,” is thought to be primarily due to changes in blood gases. However, we theorized that other factors, such as lung volume, also contributes significantly to terminating breath holds during face immersion. Accordingly, nine naïve subjects (controls) and seven underwater hockey players (divers) voluntarily initiated face immersions in room temperature water at Total Lung Capacity (TLC) and Functional Residual Capacity (FRC) after pre-breathing air, 100% O2, 15% O2 / 85% N2, or 5% CO2 / 95% O2. Heart rate (HR), arterial blood pressure (BP), end-tidal CO2 (etCO2), and breath hold durations (BHD) were monitored during all face immersions. The decrease in HR and increase in BP were not significantly different at the two lung volumes, although the increase in BP was usually greater at FRC. BHD was significantly longer at TLC (54 ± 2 s) than at FRC (30 ± 2 s). Also, with each pre-breathed gas BHD was always longer at TLC. We found no consistent etCO2 at which the breath holding terminated. BDHs were significantly longer in divers than in controls. We suggest that during breath holding with face immersion high lung volume acts directly within the brainstem to actively delay the attainment of the physiological breaking point, rather than acting indirectly as a sink to produce a slower build-up of PCO2.

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