Measurement of Pressure-Time Product during Spontaneous Assisted Breathing by Rapid Interrupter Technique

2008 ◽  
Vol 2008 ◽  
pp. 120-121
Author(s):  
M. Mathru
Keyword(s):  
Pressure Time ◽  
Pressure Time Product

Patient-ventilator interaction during acute hypercapnia: pressure-support vs. proportional-assist ventilation

1996 ◽  
Vol 81 (1) ◽  
pp. 426-436 ◽  
Author(s):  
V. M. Ranieri ◽  
R. Giuliani ◽  
L. Mascia ◽  
S. Grasso ◽  
V. Petruzzelli ◽  
...  
Keyword(s):  
Respiratory Rate ◽  
Dead Space ◽  
Pressure Support ◽  
Esophageal Pressure ◽  
Respiratory Drive ◽  
Resistive Load ◽  
Proportional Assist Ventilation ◽  
Pressure Time ◽  
Pressure Time Product ◽  
Stimulation Of

The objective of this study was to compare patient-ventilator interaction during pressure-support ventilation (PSV) and proportional-assist ventilation (PAV) in the course of increased ventilatory requirement obtained by adding a dead space in 12 patients on weaning from mechanical ventilation. With PSV, the level of unloading was provided by setting the inspiratory pressure at 20 and 10 cmH2O, whereas with PAV the level of unloading was at 80 and 40% of the elastic and resistive load. Hypercapnia increased (P < 0.001) tidal swing of esophageal pressure and pressure-time product per breath at both levels of PSV and PAV. During PSV, application of dead space increased ventilation (VE) during PSV (67 +/- 4 and 145 +/- 5% during 20 and 10 cmH2O PSV, respectively, P < 0.001). This was due to a relevant increase in respiratory rate (48 +/- 4 and 103 +/- 5% during 20 and 10 cmH2O PSV, respectively, P < 0.001), whereas the increase in tidal volume (VT) played a small role (13 +/- 1 and 21 +/- 2% during 20 and 10 cmH2O PSV, respectively, P < 0.001). With PAV, the increase in VE consequent to hypercapnia (27 +/- 3 and 64 +/- 4% during 80 and 40% PAV, respectively, P < 0.001) was related to the increase in VT (32 +/- 1 and 66 +/- 2% during 80 and 40% PAV, respectively, P < 0.001), respiratory rate remaining unchanged. The increase in pressure-time product per minute and per liter consequent to acute hypercapnia and the sense of breathlessness were significantly (P < 0.001) higher during PSV than during PAV. Our data show that, after hypercapnic stimulation of the respiratory drive, the capability to increase VE through changes in VT modulated by variations in inspiratory muscle effort is preserved only during PAV; the compensatory strategy used to increase VE during PSV requires greater muscle effort and causes more pronounced patient discomfort than during PAV.

O2 cost of breathing: ventilatory vs. pressure loads

1992 ◽  
Vol 73 (5) ◽  
pp. 1720-1727 ◽  
Author(s):  
S. J. Cala ◽  
J. Edyvean ◽  
M. Rynn ◽  
L. A. Engel
Keyword(s):  
Normal Subjects ◽  
Work Rate ◽  
Inspiratory Pressure ◽  
Pressure Time ◽  
Elastic Loading ◽  
Loaded Breathing ◽  
Series Of Experiments ◽  
Volume Efficiency ◽  
Percent Decrease ◽  
Pressure Time Product

We compared the O2 cost of breathing (VO2resp) at high levels of ventilation (HV) with that against high inspiratory pressure loads (HP) using an external elastance when end-expiratory volume, work rate (W), and pressure-time product (P) were matched at two levels of ventilation and elastic loading. Each of five normal subjects performed three pairs of loaded runs (one HV and one HP) bracketed by two resting runs. Mean O2 consumption from the pairs of resting runs was subtracted from that of each of the loaded runs to give VO2resp during loaded breathing. Matching for W and P was within 15% in all 15 pairs of runs. During HV runs, ventilation was 398 +/- 24% of corresponding values during HP runs (P < 0.01). Although there was no difference in W (P > 0.05), the VO2resp during HV runs was 237 +/- 33% of that during HP (P < 0.01) and efficiency of HV was 51 +/- 5% of that during HP (P < 0.01). When W was normalized for the decrease in maximum inspiratory pressure with increased mean lung volume, efficiency during HV and HP runs did not differ (P > 0.05). In the second series of experiments, when both HV and HP runs were matched for W but P was allowed to vary, efficiency increased by 1.42 +/- 0.42% (P < 0.05) for each percent decrease in P during HV runs but was unchanged (P > 0.05) during HP runs despite a 193 +/- 10% increase in P.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Proportional Assist Ventilation on Inspiratory Muscle Effort in Patients with Chronic Obstructive Pulmonary Disease and Acute Respiratory Failure

1997 ◽  
Vol 86 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Marco V. Ranieri ◽  
Salvatore Grasso ◽  
Luciana Mascia ◽  
Sergio Martino ◽  
Fiore Tommasco ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Respiratory Failure ◽  
Acute Respiratory Failure ◽  
Pulmonary Disease ◽  
Minute Ventilation ◽  
Chronic Obstructive ◽  
Proportional Assist Ventilation ◽  
Obstructive Pulmonary Disease ◽  
Pressure Time ◽  
Pressure Time Product

Background Acute respiratory failure may develop in patients with chronic obstructive pulmonary disease because of intrinsic positive end-expiratory pressure (PEEPi) and increased resistive and elastic loads. Proportional assist ventilation is an experimental mode of partial ventilatory support in which the ventilator generates flow to unload the resistive burden (flow assistance: FA) and volume to unload the elastic burden (volume assistance: VA) proportionally to inspiratory muscle effort, and PEEPi can be counterbalanced by application of external PEEP. The authors assessed effects of proportional assist ventilation and optimal ventilatory settings in patients with chronic obstructive pulmonary disease and acute respiratory failure. Methods Inspiratory muscles and diaphragmatic efforts were evaluated by measurements of esophageal, gastric, and transdiaphragmatic pressures. Minute ventilation and breathing patterns were evaluated by measuring airway pressure and flow. Measurements were performed during spontaneous breathing, continuous positive airway pressure, FA, FA+PEEP, VA, VA+PEEP, FA+VA, and FA+VA+PEEP. Results FA+PEEP provided the greatest improvement in minute ventilation (89 +/- 3%) and dyspnea (62 +/- 2%). The largest reduction in pressure time product per breath of the respiratory muscles and diaphragm (44 +/- 3% and 33 +/- 2%, respectively) also was observed during FA+PEEP condition. When VA was added to this setting, a reduction in respiratory rate (50 +/- 3%), an increase in inspiratory time (102 +/- 6%), and a further reduction in pressure time product per minute (65 +/- 2% and 64% for the respiratory muscles and diaphragm, respectively) was observed. However, values of pressure time product per liter of minute ventilation during FA+VA+PEEP did not differ with those observed during FA+PEEP condition. Worsening of patient-ventilator interaction and breathing asynchrony occurred when VA was implemented. Conclusions Application of PEEP to counterbalance PEEPi and FA to unload the resistive burden provided the optimal conditions in such patients. Ventilator over-assistance and patient-ventilator asynchrony was observed when VA was added to this setting. The clinical use of proportional assist ventilation should be based on continuous measurements of respiratory mechanics.

Poor Correlation between Diaphragm Thickening Fraction and Transdiaphragmatic Pressure in Mechanically Ventilated Patients and Healthy Subjects

2021 ◽  
Author(s):  
Thomas Poulard ◽  
Damien Bachasson ◽  
Quentin Fossé ◽  
Marie-Cécile Niérat ◽  
Jean-Yves Hogrel ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Healthy Subjects ◽  
Healthy Individuals ◽  
Transdiaphragmatic Pressure ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Diaphragm Function ◽  
Pressure Time ◽  
Pressure Time Product ◽  
Ventilated Patients

Background The relationship between the diaphragm thickening fraction and the transdiaphragmatic pressure, the reference method to evaluate the diaphragm function, has not been clearly established. This study investigated the global and intraindividual relationship between the thickening fraction of the diaphragm and the transdiaphragmatic pressure. The authors hypothesized that the diaphragm thickening fraction would be positively and significantly correlated to the transdiaphragmatic pressure, in both healthy participants and ventilated patients. Methods Fourteen healthy individuals and 25 mechanically ventilated patients (enrolled in two previous physiologic investigations) participated in the current study. The zone of apposition of the right hemidiaphragm was imaged simultaneously to transdiaphragmatic pressure recording within different breathing conditions, i.e., external inspiratory threshold loading in healthy individuals and various pressure support settings in patients. A blinded offline breath-by-breath analysis synchronously computed the changes in transdiaphragmatic pressure, the diaphragm pressure-time product, and diaphragm thickening fraction. Global and intraindividual relationships between variables were assessed. Results In healthy subjects, both changes in transdiaphragmatic pressure and diaphragm pressure-time product were moderately correlated to diaphragm thickening fraction (repeated measures correlation = 0.40, P &lt; 0.0001; and repeated measures correlation = 0.38, P &lt; 0.0001, respectively). In mechanically ventilated patients, changes in transdiaphragmatic pressure and thickening fraction were weakly correlated (repeated measures correlation = 0.11, P = 0.008), while diaphragm pressure-time product and thickening fraction were not (repeated measures correlation = 0.04, P = 0.396). Individually, changes in transdiaphragmatic pressure and thickening fraction were significantly correlated in 8 of 14 healthy subjects (ρ = 0.30 to 0.85, all P &lt; 0.05) and in 2 of 25 mechanically ventilated patients (ρ = 0.47 to 0.64, all P &lt; 0.05). Diaphragm pressure-time product and thickening fraction correlated in 8 of 14 healthy subjects (ρ = 0.41 to 0.82, all P &lt; 0.02) and in 2 of 25 mechanically ventilated patients (ρ = 0.63 to 0.66, all P &lt; 0.01). Conclusions Overall, diaphragm function as assessed with transdiaphragmatic pressure was weakly related to diaphragm thickening fraction. The diaphragm thickening fraction should not be used in healthy subjects or ventilated patients when changes in diaphragm function are evaluated. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Pressure-time product, work rate, and endurance during resistive breathing in humans

1988 ◽  
Vol 64 (4) ◽  
pp. 1397-1404 ◽  
Author(s):  
D. S. Dodd ◽  
S. Kelly ◽  
P. W. Collett ◽  
L. A. Engel
Keyword(s):  
Blood Flow ◽  
Respiratory Muscle ◽  
Muscle Blood Flow ◽  
Normal Subjects ◽  
Work Rate ◽  
Available Energy ◽  
Pressure Time ◽  
Mouth Pressure ◽  
Resistive Breathing ◽  
Pressure Time Product

We examined the effect of increasing work rate, without a corresponding increase in the pressure-time product, on energy cost and inspiratory muscle endurance (Tlim) in five normal subjects during inspiratory resistive breathing. Tidal volume, mean inspiratory mouth pressure, duty cycle, and hence the pressure-time product were kept constant, whereas work rate was varied by changing the frequency of breathing. There was a linear decrease in Tlim of -2.1 ± 0.5 s.J-1.min-1 (r = 0.87 ± 0.06) with increasing work rate. The data satisfied a model of energy balance during fatiguing runs (Monod and Scherrer. Ergonomics 8: 329-337, 1965) and were consistent with the hypothesis that the rate of energy supply, or respiratory muscle blood flow, is fixed when the pressure-time product is constant. Our results indicate that during inspiratory resistive breathing against fatiguing loads, work rate determines endurance independently of the pressure-time product. On the basis of the model, our results lead to estimates of respiratory muscle blood flow and available energy stores under the conditions of our experiment.

Measurement of Pressure–Time Product during Spontaneous Assisted Breathing by Rapid Interrupter Technique

2007 ◽  
Vol 106 (3) ◽  
pp. 484-490 ◽  
Author(s):  
Giacomo Bellani ◽  
Nicolò Patroniti ◽  
Dieter Weismann ◽  
Lucia Galbiati ◽  
Francesco Curto ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Pressure Support ◽  
Work Of Breathing ◽  
Ventilatory Support ◽  
Respiratory Muscles ◽  
Esophageal Pressure ◽  
Assisted Ventilation ◽  
Reliable Estimate ◽  
Pressure Time ◽  
Pressure Time Product

Background Measuring the work of breathing of patients undergoing spontaneous assisted ventilation can be useful to monitor and titrate ventilatory support. The aim of this study was to obtain measurements of the pressure generated by the respiratory muscles (PMUSC) and the derived pressure-time product (PTP; a good indicator of the metabolic work of breathing), performing the rapid interrupter technique with a commercial ventilator. Methods A Draeger Evita 4 ventilator (Draeger Medical, Lubeck, Germany) was controlled by a personal computer to rapidly interrupt the airway flow at different times and volumes of the respiratory cycle during pressure-support ventilation. From the airway pressure tracing after the occlusion, the authors estimated the alveolar pressure and PMUSC; the integration of PMUSC values over the inspiratory time yields the measurement of PTP. Esophageal pressure measurements were used as a reference. After a bench study of the valves' performance, the authors performed 11 measurement sequences in eight patients. Results The closure times for the inspiratory and expiratory valves were 74 +/- 10 and 61 +/- 13 ms, respectively. The interrupter technique provided a reliable estimate of PMUSC (PMUSC, occl = 1.00 . PMUSC, pes + 0.19; r = 0.88; 95% confidence interval for agreement, +5.49/-5.32 cm H2O). PTPoccl tightly correlated with PTPpes (PTPoccl = 0.95 . PTPpes + 0.13; r = 0.96; 95% confidence interval, 1.94/-1.61 cm H2O . s). Conclusion The rapid interrupter technique can be performed by means of a commercial ventilator, providing reliable measurement of PMUSC and PTP.

scholarly journals Additional work of breathing from trigger errors in mechanically ventilated children

2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Robert G. T. Blokpoel ◽  
Alette A. Koopman ◽  
Jefta van Dijk ◽  
Martin C. J. Kneyber
Keyword(s):  
Intensive Care ◽  
Work Of Breathing ◽  
Paediatric Intensive Care ◽  
Pleural Pressure ◽  
Lower Amount ◽  
Mechanically Ventilated ◽  
Additional Work ◽  
Oesophageal Pressure ◽  
Pressure Time ◽  
Pressure Time Product

Abstract Background Patient–ventilator asynchrony is associated with increased morbidity and mortality. A direct causative relationship between Patient–ventilator asynchrony and adverse clinical outcome have yet to be demonstrated. It is hypothesized that during trigger errors excessive pleural pressure swings are generated, contributing to increased work-of-breathing and self-inflicted lung injury. The objective of this study was to determine the additional work-of-breathing and pleural pressure swings caused by trigger errors in mechanically ventilated children. Methods Prospective observational study in a tertiary paediatric intensive care unit in an university hospital. Patients ventilated > 24 h and < 18 years old were studied. Patients underwent a 5-min recording of the ventilator flow–time, pressure–time and oesophageal pressure–time scalar. Pressure–time–product calculations were made as a proxy for work-of-breathing. Oesophageal pressure swings, as a surrogate for pleural pressure swings, during trigger errors were determined. Results Nine-hundred-and-fifty-nine trigger errors in 28 patients were identified. The additional work-of-breathing caused by trigger errors showed great variability among patients. The more asynchronous breaths were present the higher the work-of-breathing of these breaths. A higher spontaneous breath rate led to a lower amount of trigger errors. Patient–ventilator asynchrony was not associated with prolonged duration of mechanical ventilation or paediatric intensive care stay. Conclusions The additional work-of-breathing caused by trigger errors in ventilated children can take up to 30–40% of the total work-of-breathing. Trigger errors were less common in patients breathing spontaneously and those able to generate higher pressure–time–product and pressure swings. Trial registration Not applicable.

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