Esophageal and transdiaphragmatic pressure swings as indices of inspiratory effort

Transdiaphragmatic pressure (Pdi) is lower during maximum inspiratory effort with the diaphragm alone than when maximum inspiratory and expulsive efforts are combined. The increase in Pdi with expulsive effort has been attributed to increased neural activation of the diaphragm. Alternatively, the increase could be due to stretching of the contracted diaphragm. If this were so, Pdi measured during a combined maximum effort would overestimate the capacity of the diaphragm to generate inspiratory force. This study determined the likely contribution of stretching of the contracted diaphragm to estimates of maximum Pdi (Pdimax) obtained during combined inspiratory and expulsive effort. Three healthy trained subjects were studied standing. Diaphragmatic Mueller maneuvers were performed at functional residual capacity and sustained during subsequent abdominal compression by either abdominal muscle expulsive effort or externally applied pressure. Measurements were made of changes in abdominal (Pab) and pleural (Ppl) pressure, Pdi, rib cage and abdominal dimensions and respiratory electromyograms. Three reproducible performances of each maneuver from each subject were analyzed. When expulsive effort was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 86 +/- 12 to 148 +/- 14 (SD) cmH2O within the 1st s and was 128 +/- 14 cmH2O 2 s later. When external compression was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 87 +/- 16 to 171 +/- 19 cmH2O within the 1st s and was 152 +/- 16 cmH2O 2 s later.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Effects of fenoterol on inspiratory effort sensation and fatigue during inspiratory threshold loading

Journal of Applied Physiology ◽

10.1152/jappl.1996.80.3.727 ◽

1996 ◽

Vol 80 (3) ◽

pp. 727-733 ◽

Cited By ~ 8

Author(s):

J. Suzuki ◽

S. Suzuki ◽

T. Okubo

Keyword(s):

Low Frequency ◽

Normal Subjects ◽

Motor Command ◽

Inspiratory Effort ◽

Double Blind ◽

Endurance Time ◽

Transdiaphragmatic Pressure ◽

Mouth Pressure ◽

Residual Capacity ◽

Low Frequency Power

We studied the effects of a single dose of fenoterol on the relationship between inspiratory effort sensation (IES) and inspiratory muscle fatigue induced by inspiratory threshold loading in healthy subjects. The magnitude of the threshold was 60% of maximal static inspiratory mouth pressure (PI,mmax) at functional residual capacity, and the duty cycle was 0.5. Subjects continued the threshold loaded breathing until the target mouth pressure could no longer be maintained (endurance time). The intensity of the IES was scored with a modified Borg scale. Either fenoterol (5 mg) or a placebo was given orally 2 h before loading in a randomized double-blind crossover protocol. The endurance time with fenoterol (34.4 +/- 8.6 min) was longer than that with the placebo (22.2 +/- 7.1 min; P < 0.05). The ratio of high- to low-frequency power of the diaphragmatic electromyogram (EMGdi) decreased during loading; the decrease was less with fenoterol (P < 0.05). The EMGdi also decreased with loading; the decrease was greater on fenoterol treatment (P < 0.01). The PI,mmax and maximal transdiaphragmatic pressure (Pdi) were similarly decreased after loading on either treatment. The intensity of the IES rose with time during loading in both groups but was lower with fenoterol than with the placebo (P < 0.05). The ratio of Pdi to integrated activity of the EMGdi increased with fenoterol (P < 0.05). Fenoterol treatment increased both superimposed Pdi twitch and Pdi twitch of relaxed diaphragm and decreased the value of (1-superimposed Pdi twitch/Pdi twitch of relaxed diaphragm). Thus we conclude that in normal subjects fenoterol reduces diaphragmatic fatigue and decreases the motor command to the diaphragm, resulting in a decrease in IES during inspiratory threshold loading and a prolongation of endurance.

Download Full-text

Surface EMG-based Quantification of Inspiratory Effort: A Quantitative Comparison with Pes

10.21203/rs.3.rs-840665/v1 ◽

2021 ◽

Author(s):

Jan Graßhoff ◽

Eike Petersen ◽

Franziska Farquharson ◽

Max Kustermann ◽

Hans-Joachim Kabitz ◽

...

Keyword(s):

Mechanical Ventilation ◽

Surface Electromyography ◽

Conversion Factor ◽

Balloon Catheter ◽

Respiratory Muscles ◽

Inspiratory Effort ◽

Transdiaphragmatic Pressure ◽

Assisted Mechanical Ventilation ◽

Non Invasive ◽

Four Levels

Abstract Background Inspiratory patient effort under assisted mechanical ventilation is an important quantity for assessing patient-ventilator interaction and recognizing over and under assistance. An established clinical standard is respiratory muscle pressure Pmus, derived from esophageal pressure (Pes), which requires the correct placement and calibration of an esophageal balloon catheter. Surface electromyography (sEMG) of the respiratory muscles represents a promising and straightforward alternative technique, enabling non-invasive monitoring of patient activity. Methods A prospective observational study was conducted with patients under assisted mechanical ventilation, who were scheduled for elective bronchoscopy. Airway flow and pressure, esophageal/gastric pressures and sEMG of the diaphragm and intercostal muscles were recorded at four levels of pressure support ventilation. Patient efforts were quantified via the Pmus–time product (PTPmus), the transdiaphragmatic pressure–time product (PTPdi) and the EMG–time products (ETP) of the two sEMG channels. To improve the signal-to-noise ratio, a method for automatically selecting the more informative of the sEMG channels was investigated. Correlation between ETP and PTPmus was assessed by determining a neuromechanical conversion factor KEMG between the two quantities. Moreover, it was investigated whether this scalar can be reliably determined from airway pressure during occlusion maneuvers, thus allowing to quantify inspiratory effort based solely on sEMG measurements. Results In total, 62 patients with heterogeneous pulmonary diseases were enrolled in the study, 43 of wich were included in the data analysis. The ETP of the two sEMG channels was well correlated with PTPmus (r=0.79±0.25 and r=0.84±0.16 for diaphragm and intercostal recordings, respectively). The proposed automatic channel selection method improved correlation with PTPmus (r=0.87±0.09). The neuromechanical conversion factor obtained by fitting ETP to PTPmus varied widely between patients (KEMG=4.32±3.73 cmH2O/μV) and was highly correlated with the scalar determined during occlusions (r=0.95, p<.001). The occlusion-based method for deriving PTPmus from ETP showed a breath-wise deviation to PTPmus of 0.43±1.73 cmH2Os across all datasets. Conclusion These results support the use of surface electromyography as a reliable non-invasive alternative for monitoring breath-by-breath inspiratory effort of patients under assisted mechanical ventilation.

Download Full-text

Respiratory load compensation in chronic airway obstruction

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.6.1947 ◽

1985 ◽

Vol 59 (6) ◽

pp. 1947-1954 ◽

Cited By ~ 8

Author(s):

M. Lopata ◽

E. Onal ◽

G. Cromydas

Keyword(s):

Airway Obstruction ◽

Lung Volume ◽

Average Rate ◽

Minute Ventilation ◽

Force Output ◽

Transdiaphragmatic Pressure ◽

Load Compensation ◽

Group A ◽

Group B ◽

Chronic Airway

To assess respiratory neuromuscular function and load compensating ability in patients with chronic airway obstruction (CAO), we studied eight stable patients with irreversible airway obstruction during hyperoxic CO2 rebreathing with and without a 17 cmH2O X l-1 X s flow-resistive inspiratory load (IRL). Minute ventilation (VE), transdiaphragmatic pressure (Pdi), and diaphragmatic electromyogram (EMGdi) were monitored. Pdi and EMGdi were obtained via a single gastroesophageal catheter with EMGdi being quantitated as the average rate of rise of inspiratory (moving average) activity. Based on the effects of IRL on the Pdi response to CO2 [delta Pdi/delta arterial CO2 tension (PaCO2)] and the change in Pdi for a given change in EMGdi (delta Pdi/delta EMGdi) during rebreathing, two groups could be clearly identified. Four patients (group A) were able to increase delta Pdi/delta PaCO2 and delta Pdi/delta EMGdi, whereas in the other four (group B) the IRL responses decreased. All group B patients were hyperinflated having significantly greater functional residual capacity (FRC) and residual volume than group A. In addition the IRL induced percent change in delta Pdi/delta PaCO2, and delta VE/delta PaCO2 was negatively correlated with lung volume so that in the hyperinflated group B the higher the FRC the greater was the decrease in Pdi response due to IRL. In both groups the greater the FRC the greater was the decrease in the ventilatory response to loading. Patients with CAO, even with severe airways obstruction, can effect load compensation by increasing diaphragmatic force output, but the presence of increased lung volume with the associated shortened diaphragm prevents such load compensation.

Download Full-text

Human respiratory muscle blood flow measured by near-infrared spectroscopy and indocyanine green

Journal of Applied Physiology ◽

10.1152/japplphysiol.01160.2007 ◽

2008 ◽

Vol 104 (4) ◽

pp. 1202-1210 ◽

Cited By ~ 50

Author(s):

Jordan A. Guenette ◽

Ioannis Vogiatzis ◽

Spyros Zakynthinos ◽

Dimitrios Athanasopoulos ◽

Maria Koskolou ◽

...

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Infrared Spectroscopy ◽

Respiratory Muscle ◽

Near Infrared ◽

Vastus Lateralis ◽

Muscle Blood Flow ◽

Work Of Breathing ◽

Dilution Method ◽

Transdiaphragmatic Pressure

Measurement of respiratory muscle blood flow (RMBF) in humans has important implications for understanding patterns of blood flow distribution during exercise in healthy individuals and those with chronic disease. Previous studies examining RMBF in humans have required invasive methods on anesthetized subjects. To assess RMBF in awake subjects, we applied an indicator-dilution method using near-infrared spectroscopy (NIRS) and the light-absorbing tracer indocyanine green dye (ICG). NIRS optodes were placed on the left seventh intercostal space at the apposition of the costal diaphragm and on an inactive control muscle (vastus lateralis). The primary respiratory muscles within view of the NIRS optodes include the internal and external intercostals. Intravenous bolus injection of ICG allowed for cardiac output (by the conventional dye-dilution method with arterial sampling), RMBF, and vastus lateralis blood flow to be quantified simultaneously. Esophageal and gastric pressures were also measured to calculate the work of breathing and transdiaphragmatic pressure. Measurements were obtained in five conscious humans during both resting breathing and three separate 5-min bouts of constant isocapnic hyperpnea at 27.1 ± 3.2, 56.0 ± 6.1, and 75.9 ± 5.7% of maximum minute ventilation as determined on a previous maximal exercise test. RMBF progressively increased (9.9 ± 0.6, 14.8 ± 2.7, 29.9 ± 5.8, and 50.1 ± 12.5 ml·100 ml−1·min−1, respectively) with increasing levels of ventilation while blood flow to the inactive control muscle remained constant (10.4 ± 1.4, 8.7 ± 0.7, 12.9 ± 1.7, and 12.2 ± 1.8 ml·100 ml−1·min−1, respectively). As ventilation rose, RMBF was closely and significantly correlated with 1) cardiac output ( r = 0.994, P = 0.006), 2) the work of breathing ( r = 0.995, P = 0.005), and 3) transdiaphragmatic pressure ( r = 0.998, P = 0.002). These data suggest that the NIRS-ICG technique provides a feasible and sensitive index of RMBF at different levels of ventilation in humans.

Download Full-text

Diaphragmatic work of breathing in premature human infants

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.4.1410 ◽

1987 ◽

Vol 62 (4) ◽

pp. 1410-1415 ◽

Cited By ~ 39

Author(s):

B. G. Guslits ◽

S. E. Gaston ◽

M. H. Bryan ◽

S. J. England ◽

A. C. Bryan

Keyword(s):

Lung Disease ◽

Preterm Infants ◽

Work Of Breathing ◽

Mechanical Efficiency ◽

Strongly Correlated ◽

Intercostal Muscle ◽

Human Infants ◽

Transdiaphragmatic Pressure ◽

Rib Cage ◽

Inspiratory Work

Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.

Download Full-text

Detection of diaphragmatic fatigue in man by phrenic stimulation

Journal of Applied Physiology ◽

10.1152/jappl.1981.50.3.538 ◽

1981 ◽

Vol 50 (3) ◽

pp. 538-544 ◽

Cited By ~ 126

Author(s):

M. Aubier ◽

G. Farkas ◽

A. De Troyer ◽

R. Mozes ◽

C. Roussos

Keyword(s):

Phrenic Nerve ◽

Chronic Obstructive Lung Disease ◽

Chronic Obstructive ◽

Low Frequencies ◽

Transdiaphragmatic Pressure ◽

Control Value ◽

Transcutaneous Stimulation ◽

Diaphragmatic Fatigue ◽

Residual Capacity ◽

Stimulation Of

Transdiaphragmatic pressure (Pdi) was measured at functional residual capacity (FRC) in four normal seated subjects during supramaximal, supraclavicular transcutaneous stimulation of one phrenic nerve (10, 20, 50, and 100 Hz--0.1 ms duration) before and after diaphragmatic fatigue, produced by breathing through a high alinear inspiratory resistance. Constancy of chest wall configuration was achieved by placing a cast around the abdomen and the lower one-fourth of the rib cage. Pdi increased with frequency of stimulation, so that at 10, 20, and 50 Hz, the Pdi generated was 32 +/- 4 (SE), 70 +/- 3, and 98 +/- 2% of Pdi at 100 Hz, respectively. After diaphragmatic fatigue, Pdi was less than control at all frequencies of stimulation. Recovery for high stimulation frequencies was complete at 10 min, but at low stimulation frequencies recovery was slow: after 30 min of recovery, Pdi at 20 Hz was 31 +/- 7% of the control value. It is concluded that diaphragmatic fatigue can be detected in man by transcutaneous stimulation of the phrenic nerve and that diaphragmatic strength after fatigue recovers faster at high than at low frequencies of stimulation. Furthermore, it is suggested that this long-lasting element of fatigue might occur in patients with chronic obstructive lung disease, predisposing them to respiratory failure.

Download Full-text

Inspiratory Effort Sensation to Added Resistive Loading in Patients With Obstructive Sleep Apnea

CHEST Journal ◽

10.1378/chest.118.5.1332 ◽

2000 ◽

Vol 118 (5) ◽

pp. 1332-1338 ◽

Cited By ~ 19

Author(s):

Ye Tun ◽

Wataru Hida ◽

Shinichi Okabe ◽

Yoshihiro Kikuchi ◽

Hajime Kurosawa ◽

...

Keyword(s):

Obstructive Sleep Apnea ◽

Sleep Apnea ◽

Inspiratory Effort ◽

Obstructive Sleep ◽

Resistive Loading

Download Full-text

Relationships among pressure, tension, and shape of the diaphragm

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.6.1899 ◽

1983 ◽

Vol 55 (6) ◽

pp. 1899-1905 ◽

Cited By ~ 15

Author(s):

W. A. Whitelaw ◽

L. E. Hajdo ◽

J. A. Wallace

Keyword(s):

Cross Section ◽

Radius Of Curvature ◽

Transdiaphragmatic Pressure ◽

Rib Cage ◽

Residual Capacity ◽

Best Fitting ◽

Pressure Generator ◽

Free Membrane ◽

Relationship Of ◽

Shape Changes

The shape of the diaphragm dome was calculated from transdiaphragmatic pressure and tension in the diaphragm. It was assumed that the muscle acts as a free membrane, attached at its edges to the inside of a vertical rib cage circular in cross section, that the attachments are inferior to the point at which the dome makes contract with the rib cage, and that the abdomen is filled with fluid with a hydrostatic gradient in pressure. The shape is different from a section of a sphere, with a radius of curvature substantially greater at the apex of the dome than at the sides. Observed shapes of human hemidiaphragm domes at functional residual capacity are not spherical but closely match the calculated shapes. Best-fitting shapes correspond to transdiaphragmatic pressures of about 3 cmH2O transdiaphragmatic pressure, suggesting that such a pressure and corresponding tension are present in the human diaphragm when it is at rest in an erect subject. In this model; as lung volume increases and the diaphragm shortens, its shape changes in such a way that the ratio between transdiaphragmatic pressure and tension in the diaphragm remains nearly constant, rather than increasing with volume. Such a model can explain the observation that the length-tension relationship of the muscle is much more important than curvature in determining the effectiveness of the diaphragm as a pressure generator.

Download Full-text

Pleural pressure increases during inspiration in the zone of apposition of diaphragm to rib cage

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.5.2207 ◽

1988 ◽

Vol 65 (5) ◽

pp. 2207-2212 ◽

Cited By ~ 27

Author(s):

W. F. Urmey ◽

A. De Troyer ◽

K. B. Kelly ◽

S. H. Loring

Keyword(s):

Esophageal Pressure ◽

Pleural Pressure ◽

Abdominal Pressure ◽

Transdiaphragmatic Pressure ◽

Rib Cage ◽

Direct Measurements ◽

Anesthetized Dogs ◽

Theoretical Mechanism ◽

Phrenic Stimulation ◽

Anatomic Region

The zone of apposition of diaphragm to rib cage provides a theoretical mechanism that may, in part, contribute to rib cage expansion during inspiration. Increases in intra-abdominal pressure (Pab) that are generated by diaphragmatic contraction are indirectly applied to the inner rib cage wall in the zone of apposition. We explored this mechanism, with the expectation that pleural pressure in this zone (Pap) would increase during inspiration and that local transdiaphragmatic pressure in this zone (Pdiap) must be different from conventionally determined transdiaphragmatic pressure (Pdi) during inspiration. Direct measurements of Pap, as well as measurements of pleural pressure (Ppl) cephalad to the zone of apposition, were made during tidal inspiration, during phrenic stimulation, and during inspiratory efforts in anesthetized dogs. Pab and esophageal pressure (Pes) were measured simultaneously. By measuring Ppl's with cannulas placed through ribs, we found that Pap consistently increased during both maneuvers, whereas Ppl and Pes decreased. Whereas changes in Pdi of up to -19 cmH2O were measured, Pdiap never departed from zero by greater than -4.5 cmH2O. We conclude that there can be marked regional differences in Ppl and Pdi between the zone of apposition and regions cephalad to the zone. Our results support the concept of the zone of apposition as an anatomic region where Pab is transmitted to the interior surface of the lower rib cage.

Download Full-text