Effect of hyperinflation on inspiratory function of the diaphragm

The inspiratory efficiency of the diaphragm during unilateral and bilateral phrenic stimulation (UEPS and BEPS) with constant stimulus was studied in seven dogs from FRC to 120% TLC. Alveolar pressures (PAl) were recorded during relaxation, BEPS and UEPS at each lung volume in the closed respiratory system. From the PAl-lung volume curves, tidal volume (VT), and pressure developed by the diaphragm (Pmus) were derived. Results are summarized below. a) Hyperinflation impaired the inspiratory efficiency of the diaphragm which behaved as an expiratory muscle beyond the lung volume of 103.7% TLC (Vinef). b) The diaphragm during UEPS became expiratory at the same Vinef as during (BEPS. C) The VT-lung volume relationship was linear during BEPS, allowing simple quantitation of VT loss with hyperinflation and prediction of Vinef. d) With only one phrenic nerve stimulated, the functional loss is less pronounced in VT than in Pmus, as compared to BEPS, indicating that the respiratory system was more compliant during UEPS than BEPS. This compliance difference from UEPS to BEPS diminished with severe hyperinflation.

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Expiratory muscle contribution to tidal volume in head-up dogs

Journal of Applied Physiology ◽

10.1152/jappl.1989.67.4.1438 ◽

1989 ◽

Vol 67 (4) ◽

pp. 1438-1442 ◽

Cited By ~ 12

Author(s):

G. A. Farkas ◽

M. Estenne ◽

A. De Troyer

Keyword(s):

Tidal Volume ◽

Lung Volume ◽

Muscle Relaxation ◽

Rib Cage ◽

Expiratory Muscle ◽

Residual Capacity ◽

Anesthetized Dogs ◽

Expiratory Muscles ◽

S Period ◽

Average Contribution

A change from the supine to the head-up posture in anesthetized dogs elicits increased phasic expiratory activation of the rib cage and abdominal expiratory muscles. However, when this postural change is produced over a 4- to 5-s period, there is an initial apnea during which all the muscles are silent. In the present studies, we have taken advantage of this initial silence to determine functional residual capacity (FRC) and measure the subsequent change in end-expiratory lung volume. Eight animals were studied, and in all of them end-expiratory lung volume in the head-up posture decreased relative to FRC [329 +/- 70 (SE) ml]. Because this decrease also represents the increase in lung volume as a result of expiratory muscle relaxation at the end of the expiratory pause, it can be used to determine the expiratory muscle contribution to tidal volume (VT). The average contribution was 62 +/- 6% VT. After denervation of the rib cage expiratory muscles, the reduction in end-expiratory lung volume still amounted to 273 +/- 84 ml (49 +/- 10% VT). Thus, in head-up dogs, about two-thirds of VT result from the action of the expiratory muscles, and most of it (83%) is due to the action of the abdominal rather than the rib cage expiratory muscles.

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Effect of changes in lung volume on respiratory system compliance in newborn infants

Journal of Applied Physiology ◽

10.1152/jappl.1989.67.3.1192 ◽

1989 ◽

Vol 67 (3) ◽

pp. 1192-1197 ◽

Cited By ~ 14

Author(s):

F. Ratjen ◽

R. Zinman ◽

A. R. Stark ◽

L. E. Leszczynski ◽

M. E. Wohl

Keyword(s):

Tidal Volume ◽

Respiratory System ◽

Lung Volume ◽

Newborn Infants ◽

Face Mask ◽

Flow Volume ◽

Respiratory System Compliance ◽

Tidal Breathing ◽

Volume Changes ◽

Passive Flow

Total respiratory system compliance (Crs) at volumes above the tidal volume (VT) was studied by use of the expiratory volume clamping (EVC) technique in 10 healthy sleeping unsedated newborn infants. Flow was measured with a pneumotachograph attached to a face mask and integrated to yield volume. Volume changes were confirmed by respiratory inductance plethysmography. Crs measured by EVC was compared with Crs during tidal breathing determined by the passive flow-volume (PFV) technique. Volume increases of approximately 75% VT were achieved with three to eight inspiratory efforts during expiratory occlusions. Crs above VT was consistently greater than during tidal breathing (P less than 0.0005). This increase in Crs likely reflects recruitment of lung units that are closed or atelectatic in the VT range. Within the VT range, Crs measured by PFV was compared with that obtained by the multiple-occlusion method (MO). PFV yielded greater values of Crs than MO (P less than 0.01). This may be due to braking of expiratory airflow after the release of an occlusion or nonlinearity of Crs. Thus both volume recruitment and airflow retardation may affect the measurement of Crs in unsedated newborn infants.

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Mechanical aspects of chest wall distortion

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.2.295 ◽

1985 ◽

Vol 59 (2) ◽

pp. 295-304 ◽

Cited By ~ 38

Author(s):

J. P. Mortola ◽

M. Saetta ◽

G. Fox ◽

B. Smith ◽

S. Weeks

Keyword(s):

Tidal Volume ◽

Respiratory System ◽

Volume Change ◽

Spontaneous Breathing ◽

Relaxation Curve ◽

Abdominal Pressure ◽

Human Infants ◽

Adult Rats ◽

Inspiratory Muscles ◽

Phrenic Stimulation

During passive inflation of the respiratory system, the rib cage (RC) expands because the pressure applied to it [approximately equal to abdominal pressure (Pab)] increases. Similar Pab-tidal volume (VT) relationships between passive and spontaneous inspirations would occur only if 1) Pab acts on RC equally in the two situations (no distortion) or 2) the extradiaphragmatic inspiratory muscles expand RC, compensating for distortion. In anesthetized adult rats and in sleeping human infants the passive relationships between VT and Pab or abdomen motion (AB) were constructed by occluding the airways during expiration. For a given Pab (or AB) in active breathing VT averaged 55% (rats) and 49% (infants) of the passive volume change. With phrenic stimulation in rats VT was only slightly less than during spontaneous breathing, indicating that, in the latter case, the respiratory system was essentially driven only by the diaphragm. In both species occasional breaths with large RC expansion occurred, and VT was then equal to or larger than the passive volume at iso-Pab. We conclude that 1) RC distortion decreases VT to approximately half of the passive value and 2) being on the relaxation curve reflects “compensated” distortion and not absence of it.

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Changes to respiratory mechanisms during speech as a result of different cues to increase loudness

Journal of Applied Physiology ◽

10.1152/japplphysiol.01239.2004 ◽

2005 ◽

Vol 98 (6) ◽

pp. 2177-2184 ◽

Cited By ~ 30

Author(s):

Jessica E. Huber ◽

Bharath Chandrasekaran ◽

John J. Wolstencroft

Keyword(s):

Young Adults ◽

Respiratory System ◽

Sound Pressure Level ◽

Lung Volume ◽

Neural Control ◽

Sound Pressure ◽

Speech Rate ◽

Muscle Tension ◽

Pressure Level ◽

Expiratory Muscle

The purpose of the present study was to determine whether different cues to increase loudness in speech result in different internal targets (or goals) for respiratory movement and whether the neural control of the respiratory system is sensitive to changes in the speaker's internal loudness target. This study examined respiratory mechanisms during speech in 30 young adults at comfortable level and increased loudness levels. Increased loudness was elicited using three methods: asking subjects to target a specific sound pressure level, asking subjects to speak twice as loud as comfortable, and asking subjects to speak in noise. All three loud conditions resulted in similar increases in sound pressure level . However, the respiratory mechanisms used to support the increase in loudness differed significantly depending on how the louder speech was elicited. When asked to target at a particular sound pressure level, subjects used a mechanism of increasing the lung volume at which speech was initiated to take advantage of higher recoil pressures. When asked to speak twice as loud as comfortable, subjects increased expiratory muscle tension, for the most part, to increase the pressure for speech. However, in the most natural of the elicitation methods, speaking in noise, the subjects used a combined respiratory approach, using both increased recoil pressures and increased expiratory muscle tension. In noise, an additional target, possibly improving intelligibility of speech, was reflected in the slowing of speech rate and in larger volume excursions even though the speakers were producing the same number of syllables.

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Effects of mean airway pressure and tidal volume on lung and chest wall mechanics in the dog

Journal of Applied Physiology ◽

10.1152/jappl.1993.74.5.2286 ◽

1993 ◽

Vol 74 (5) ◽

pp. 2286-2293 ◽

Cited By ~ 29

Author(s):

G. M. Barnas ◽

J. Sprung

Keyword(s):

Mechanical Properties ◽

Tidal Volume ◽

Chest Wall ◽

Respiratory System ◽

Lung Volume ◽

Airway Pressure ◽

Dynamic Mechanical Properties ◽

Mean Airway Pressure ◽

Residual Capacity ◽

Normal Mean

Dependencies of the dynamic mechanical properties of the respiratory system on mean airway pressure (Paw) and the effects of tidal volume (VT) are not completely clear. We measured resistance and dynamic elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) in six healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50–300 ml; 0.4 Hz) delivered at mean Paw from -9 to +23 cmH2O. Changes in end-expiratory lung volume, estimated with inductance plethysmographic belts, showed a typical sigmoidal relationship to mean Paw. Each dog showed the same dependencies of mechanical properties on mean Paw and VT. All elastances and resistances were minimal between 5 and 10 cmH2O mean Paw. All elastances, Rrs, and RL increased greatly with decreasing Paw below 5 cmH2O. Ers and EL increased above 10 cmH2O. Ecw, Ers, Rcw, and Rrs decreased slightly with increasing VT, but RL and EL were independent of VT. We conclude that 1) respiratory system impedance is minimal at the normal mean lung volume of supine anesthetized paralyzed dogs; 2) the dependency of RL on lung volume above functional residual capacity is dependent on VT and respiratory frequency; and 3) chest wall, but not lung, mechanical behavior is nonlinear (i.e., VT dependent) at any given lung volume.

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Respiratory system reactance reflects communicating lung volume in chronic obstructive pulmonary disease

Journal of Applied Physiology ◽

10.1152/japplphysiol.00503.2018 ◽

2019 ◽

Vol 126 (5) ◽

pp. 1223-1231 ◽

Cited By ~ 10

Author(s):

Stephen Milne ◽

Kanika Jetmalani ◽

David G. Chapman ◽

Joseph M. Duncan ◽

Claude S. Farah ◽

...

Keyword(s):

Chronic Obstructive Pulmonary Disease ◽

Pulmonary Disease ◽

Respiratory System ◽

Lung Volume ◽

Forced Oscillation ◽

Chronic Obstructive ◽

Forced Oscillation Technique ◽

Obstructive Pulmonary Disease ◽

Volume Relationship ◽

Residual Capacity

Respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) is theoretically and experimentally related to lung volume. In chronic obstructive pulmonary disease (COPD), the absolute volume measured by body plethysmography includes a proportion that is inaccessible to pressure oscillations applied via the mouth, that is, a “noncommunicating” lung volume. We hypothesized that in COPD the presence of noncommunicating lung would disrupt the expected Xrs-volume relationship compared with plethysmographic functional residual capacity (FRCpleth). Instead, Xrs would relate to estimates of communicating volume, namely, expiratory reserve volume (ERV) and single-breath alveolar volume (VaSB). We examined FOT and lung function data from people with COPD ( n = 51) and from healthy volunteers ( n = 40). In healthy volunteers, we observed an expected inverse relationship between reactance at 5 Hz (X5) and FRCpleth. In contrast, there was no such relationship between X5 and FRCpleth in COPD subjects. However, there was an inverse relationship between X5 and both ERV and VaSB. Hence the theoretical Xrs-volume relationship is present in COPD but only when considering the communicating volume rather than the absolute lung volume. These findings confirm the role of reduced communicating lung volume as an important determinant of Xrs and therefore advance our understanding and interpretation of FOT measurements in COPD. NEW & NOTEWORTHY To investigate the determinants of respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) in chronic obstructive pulmonary disease (COPD), we examine the relationship between Xrs and lung volume. We show that Xrs does not relate to absolute lung volume (functional residual capacity) in COPD but instead relates only to the volume of lung in communication with the airway opening. This communicating volume may therefore be fundamental to our interpretation of FOT measurements in COPD and other pulmonary diseases.

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LUNG VOLUME, TIDAL VOLUME, AND ALVEOLAR PRESSURE DURING JET VENTILATION

Pediatric Research ◽

10.1203/00006450-198404001-01791 ◽

1984 ◽

Vol 18 ◽

pp. 391A-391A

Author(s):

Ivan D Frantz ◽

Richard H Close

Keyword(s):

Tidal Volume ◽

Lung Volume ◽

Alveolar Pressure ◽

Jet Ventilation

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Effect of lung volume on breath holding

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.5.1962 ◽

1987 ◽

Vol 62 (5) ◽

pp. 1962-1969 ◽

Cited By ~ 22

Author(s):

W. A. Whitelaw ◽

B. McBride ◽

G. T. Ford

Keyword(s):

Lung Volume ◽

Hold Time ◽

Esophageal Pressure ◽

Breath Holding ◽

Breath Hold ◽

Pressure Waves ◽

Expiratory Muscle ◽

Inspiratory Muscles ◽

Consistent Change ◽

Rhythmic Contractions

The mechanism by which large lung volume lessens the discomfort of breath holding and prolongs breath-hold time was studied by analyzing the pressure waves made by diaphragm contractions during breath holds at various lung volumes. Subjects rebreathed a mixture of 8% CO2–92% O2 and commenced breath holding after reaching an alveolar plateau. At all volumes, regular rhythmic contractions of inspiratory muscles, followed by means of gastric and pleural pressures, increased in amplitude and frequency until the breakpoint. Expiratory muscle activity was more prominent in some subjects than others, and increased through each breath hold. Increasing lung volume caused a delay in onset and a decrease in frequency of contractions with no consistent change in duty cycle and a decline in magnitude of esophageal pressure swings that could be accounted for by force-length and geometric properties. The effect of lung volume on the timing of contractions most resembled that of a chest wall reflex and is consistent with the hypothesis that the contractions are a major source of dyspnea in breath holding.

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Recovery of diaphragm function after laparotomy and chronic sonomicrometer implantation

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.2.613 ◽

1989 ◽

Vol 66 (2) ◽

pp. 613-621 ◽

Cited By ~ 43

Author(s):

P. A. Easton ◽

J. W. Fitting ◽

R. Arnoux ◽

A. Guerraty ◽

A. E. Grassino

Keyword(s):

Tidal Volume ◽

Respiratory Rate ◽

Breathing Pattern ◽

Recovery Process ◽

Postoperative Recovery ◽

Postmortem Examination ◽

Midline Laparotomy ◽

Left Hemidiaphragm ◽

Direct Measurements ◽

Phrenic Stimulation

If sonomicrometry transducers could be implanted permanently into the diaphragm, direct measurements of costal and crural length and shortening could be made during recovery from the laparotomy and then indefinitely in an awake, non-anesthetized mammal. We report results from six canines in which we successfully implanted transducers onto the left hemidiaphragm through a midline laparotomy and measured segmental shortening and ventilation at intervals through 22 days of postoperative recovery. After laparotomy, breathing pattern, including tidal volume, respiratory rate and mean inspiratory flow, stabilized by the 4th postoperative day (POD). Tidal shortening of costal and crural segments increased from 1.82 and 1.45% of end-expiratory length (%LFRC) on the 2nd POD to 5.32 and 8.56% LFRC, respectively, after a mean of 22 POD. Segmental shortening did not stabilize until 10 POD, and the recovery process displayed a sequence of segmental motions: lengthening, biphasic inspiratory lengthening-shortening, and increasing simple shortening. Three weeks after implantation, costal and crural segments were stable and shortening 5.32 and 8.56% LFRC, respectively, and capable of shortening 49% LFRC with maximal phrenic stimulation. In a pair of recovered animals, the initial postoperative dysfunction did not recur after a subsequent, simple laparotomy. At postmortem examination, the chronically implanted sonomicrometer transducers were found to have evoked only a thin fibrotic capsule within the diaphragm.

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