Mean airway opening pressure as an index of inspiratory muscle task intensity

The relationship between mean values of pressure (pressure-time integral including both inspiration and expiration) measured at the airway opening (Pao) and in the esophagus (Pes) is described for ventilation on a variety of external inspiratory resistances. Pao/Pes was 0.85 or greater when the external inspiratory resistance was a 4.0-mm or smaller endotracheal tube adaptor. Additionally, Pao can be easily and accurately measured by a slowly responding mechanical manometer. This device is simple in design, unpowered, inexpensive, and can be used outside the laboratory as part of an inspiratory muscle training program.

Download Full-text

Effects of surface tension and viscosity on airway reopening

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.1.74 ◽

1990 ◽

Vol 69 (1) ◽

pp. 74-85 ◽

Cited By ~ 134

Author(s):

D. P. Gaver ◽

R. W. Samsel ◽

J. Solway

Keyword(s):

Surface Tension ◽

Fluid Viscosity ◽

Opening Pressure ◽

Viscous Forces ◽

Considerable Portion ◽

Airway Opening ◽

Wall Compliance ◽

Large Opening ◽

Surface Tension Forces ◽

The Relationship

We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent “yield pressure” that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.

Download Full-text

Inspiratory Muscle Training for Obstructive Sleep Apnea: Protocol Development and Feasibility of Home Practice by Sedentary Adults

Frontiers in Physiology ◽

10.3389/fphys.2021.737493 ◽

2021 ◽

Vol 12 ◽

Author(s):

Beatrix Krause-Sorio ◽

Eunjoo An ◽

Andrea P. Aguila ◽

Fernando Martinez ◽

Ravi S. Aysola ◽

...

Keyword(s):

Obstructive Sleep Apnea ◽

Sleep Apnea ◽

Feasibility Study ◽

Daily Practice ◽

Inspiratory Muscle ◽

Inspiratory Muscle Training ◽

Muscle Training ◽

Adjunct Treatment ◽

Obstructive Sleep ◽

Inspiratory Resistance

Background: Inspiratory muscle training (IMT) may improve respiratory and cardiovascular functions in obstructive sleep apnea (OSA) and is a potential alternative or adjunct treatment to continuous positive airway pressure (CPAP). IMT protocols were originally designed for athletes, however, we found some OSA patients could not perform the exercise, so we aimed for a more OSA-friendly protocol. Our feasibility criteria included (1) participants successfully managing the technique at home; (2) participants completing daily practice sessions and recording data logs; and (3) capturing performance plateaus to determine an optimal length of the intervention.Methods: Five sedentary OSA patients participated in this feasibility study (three men, mean age = 61.6 years, SD = 10.2). Using a digital POWERbreathe K4 or K5 device, participants performed 30 daily inhalations against a resistance set at a percentage of maximum, recalculated weekly. Participants were willing to perform one but not two daily practice sessions. Intervention parameters from common IMT protocols were adapted according to ability and subjective feedback. Some were unable to perform the typically used 75% of maximum inspiratory resistance so we lowered the target to 65%. The technique required some practice; therefore, we introduced a practice week with a 50% target. After an initial 8 weeks, the intervention was open-ended and training continued until all participants demonstrated at least one plateau of inspiratory strength (2 weeks without strength gain). Weekly email and phone reminders ensured that participants completed all daily sessions and logged data in their online surveys. Weekly measures of inspiratory resistance, strength, volume, and flow were recorded.Results: Participants successfully completed the practice and subsequent 65% IMT resistance targets daily for 13 weeks. Inspiratory strength gains showed plateaus in all subjects by the end of 10 weeks of training, suggesting 12 weeks plus practice would be sufficient to achieve and capture maximum gains. Participants reported no adverse effects.Conclusion: We developed and tested a 13-week IMT protocol in a small group of sedentary, untreated OSA patients. Relative to other IMT protocols, we successfully implemented reduced performance requirements, a practice week, and an extended timeframe. This feasibility study provides the basis for a protocol for clinical trials on IMT in OSA.

Download Full-text

Measurement of pleural pressure at low and high frequencies in normal rabbits

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.3.1142 ◽

1987 ◽

Vol 63 (3) ◽

pp. 1142-1146 ◽

Cited By ~ 8

Author(s):

D. A. Chartrand ◽

T. H. Ye ◽

J. M. Maarek ◽

H. K. Chang

Keyword(s):

Body Surface ◽

Pressure Transducer ◽

Esophageal Pressure ◽

Pleural Pressure ◽

Opening Pressure ◽

High Frequencies ◽

Occlusion Test ◽

Airway Opening ◽

Catheter Tip ◽

The Relationship

In eight tracheotomized adult rabbits placed in the supine position, we employed a catheter-tip piezoresistive pressure transducer to measure esophageal pressure (Pes) and assessed the validity of taking the changes in Pes to be the changes in pleural pressure (Ppl). We applied an occlusion test in which the tracheal cannula was occluded during either spontaneous inspiratory efforts or body surface oscillations ranging from 3 to 50 Hz. The relationship between Pes and airway opening pressure (Pao) was recorded. In all instances, the changes in Pes and Pao were virtually identical in both amplitude and phase. We conclude that, as evaluated by the occlusion test, a catheter-tip pressure transducer placed in the esophagus of rabbits can give adequate estimation of local pleural changes up to at least 50 Hz.

Download Full-text

Effect of CPAP on respiratory effort and dyspnea during exercise in severe COPD

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.1.179 ◽

1990 ◽

Vol 69 (1) ◽

pp. 179-188 ◽

Cited By ~ 71

Author(s):

B. J. Petrof ◽

E. Calderini ◽

S. B. Gottfried

Keyword(s):

Lung Volume ◽

Muscle Activation ◽

Minute Ventilation ◽

Inspiratory Muscle ◽

Expected Improvement ◽

Chronic Obstructive ◽

Time Integral ◽

Copd Patients ◽

Pressure Time ◽

Gastric Pressure

Recent work has demonstrated the ability of continuous positive airway pressure (CPAP) to relieve dyspnea during exercise in patients with severe chronic obstructive pulmonary disease (COPD). The present study examined the effects of CPAP (7.5-10 cmH2O) on the pattern of respiratory muscle activation and its relationship to dyspnea during constant work load submaximal bicycle exercise [20 +/- 4.8 (SE) W] in eight COPD patients (forced expiratory volume in 1 s = 25 +/- 3% predicted). Tidal volume, respiratory rate, minute ventilation, and end-expiratory lung volume increased with exercise as expected. There was no change in breathing pattern, end-expiratory lung volume, or pulmonary compliance and resistance with the addition of CPAP. CPAP reduced inspiratory muscle effort, as indicated by the pressure-time integral of transdiaphragmatic (integral of Pdi.dt) and esophageal pressure (integral of Pes.dt, P less than 0.01 and P less than 0.05, respectively). In contrast, the pressure-time integral of gastric pressure (integral of Pga.dt), used as an index of abdominal muscle recruitment during expiration, increased (P less than 0.01). Dyspnea improved with CPAP in five of the eight patients. The amelioration of dyspnea was directly related to reductions in integral of Pes.dt (P less than 0.001) but inversely related to increases in integral of Pga.dt (P less than 0.01). In conclusion, CPAP reduces inspiratory muscle effort during exercise in COPD patients. However, the expected improvement in dyspnea is not seen in all patients and may be explained by more marked increases in expiratory muscle effort in some individuals.

Download Full-text

Airway resistance measured in liquid-trapped guinea pig lungs by micropuncture

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.6.2446 ◽

1988 ◽

Vol 65 (6) ◽

pp. 2446-2452

Author(s):

Y. L. Lai ◽

S. Ganesan ◽

S. J. Lai-Fook

Keyword(s):

Guinea Pig ◽

Airway Resistance ◽

Close Association ◽

Maximum Volume ◽

Liquid Pressure ◽

Opening Pressure ◽

Airway Narrowing ◽

Airway Opening ◽

Liquid Trapping ◽

The Relationship

We studied the relationship between bronchoconstriction and the degree of trapping in saline-filled lungs isolated from guinea pigs postmortem after rapid exsanguination. Airway resistance was measured in nine lungs, and in five lungs the site of airway narrowing was located radiographically. Animals were anesthetized with pentobarbital sodium, degassed by O2 absorption, then rapidly exsanguinated when O2 absorption was almost complete. Liquid trapping was assessed from the pressure-volume behaviour measured in saline-filled lungs. During a slow deflation from maximum volume, alveolar liquid pressure (Palv) was measured by the micropipette-servonulling method, airway opening pressure (Pao) by a strain gauge, and flow rate (Q) by weighing a reservoir connected to the airway. Airway resistance (Raw) was calculated at different lung volumes from the relationship: Raw = (Palv-Pao)/Q. In untreated lungs, Raw and fluid trapping were relatively high, and severe bronchoconstriction occurred at the level of the main stem and lobar bronchi. Nifedipine infusion reduced Raw 40-fold and decreased trapping. Raw was further reduced 10-fold and fluid trapping was minimal in lungs pretreated with nifedipine before exsanguination. Results suggest a close association between bronchoconstriction and fluid trapping in guinea pig lungs.

Download Full-text

The Relationship among the Inspiratory Muscle Strength, the Perception of Dyspnea and Inhaled Beta2-Agonists in Patients with Asthma

Canadian Respiratory Journal ◽

10.1155/2002/746808 ◽

2002 ◽

Vol 9 (5) ◽

pp. 307-312 ◽

Cited By ~ 23

Author(s):

Paltiel Weiner ◽

Rasmi Magadle ◽

Marinella Beckerman ◽

Noa Berar-Yanay

Keyword(s):

Muscle Strength ◽

Inspiratory Muscle ◽

Inspiratory Muscle Training ◽

Maximal Inspiratory Pressure ◽

Muscle Training ◽

Moderate Asthma ◽

Inspiratory Muscles ◽

The Mean ◽

The Relationship ◽

Inspiratory Muscle Strength

BACKGROUND: It is well documented that the perception of dyspnea (POD), subjectively reported by patients, is related to the activity and strength of the inspiratory muscles, and influences the use of 'as needed' beta2-agonists.STUDY OBJECTIVE: To investigate the relationship among the increase in inspiratory muscle strength after specific inspiratory muscle training, beta2-agonist consumption and the POD in patients with persistent, mild to moderate asthma.METHODS: Inspiratory muscle strength, daily beta2-agonist consumption and the POD were measured in 30 patients with mild to moderate asthma. Patients were then randomly assigned to two groups: one group received specific inspiratory muscle training until an increase of more than 20 cm H2O was reached, and one group was a control group and received sham training. Inspiratory muscle strength, the POD and daily beta2-agonist consumption were assessed during and after the training period.RESULTS: There was no good correlation between the baseline maximal inspiratory pressure and the POD, or between the baseline maximal inspiratory pressure and the mean daily beta2-agonist consumption. However, there was a significant correlation between the POD and the mean daily beta2-agonist consumption. The increase in inspiratory muscle strength after the inspiratory muscle training was closely correlated with the decrease in the POD (P<0.001) and the decrease in beta2-agonist consumption (P<0.001).CONCLUSIONS: The present study shows that, in patients with mild to moderate, persistent asthma, there is a correlation between the POD and the mean daily beta2-agonist consumption. When the inspiratory muscles are strengthened, there is a significant decrease in the POD and in beta2-agonist consumption.

Download Full-text