Effects Of Pressure Support Ventilation Research Articles

Volume support ventilation versus pressure support ventilation as a weaning mode of mechanically ventilated patients with chronic obstructive pulmonary disease

Abstract Background A dual controlled ventilatory mode called volume support ventilation (VSV) is anew mode, which is intended to speed up weaning and encourage spontaneous breathing. The purpose of the study was to compare the effectiveness of pressure support ventilation (PSV) and VSV in weaning patients with chronic obstructive pulmonary disease (COPD) who are mechanically ventilated. Patients and methods Fifty COPD patients admitted to the respiratory ICU were enrolled. Patients were assigned randomly to either PSV or VSV as a weaning mode. Patients were checked on at intervals of 30, 60 min, and 24 h. Results of weaning and hospital outcomes were recorded. Results Compared with PSV, VSV showed significant shorter weaning duration (12.76 ± 8.02 vs. 18.56 ± 5.97 h, P=0.04). Moreover, there was a higher successful extubation rate of 80% for VSV group compared with 76% for PSV, with the same complications and death rate between the two groups. Conclusion When compared to PSV mode, VSV mode was a safer, more dependable strategy that may be used responsibly for weaning trials in COPD patients. It also has the potential to shorten ICU stays and weaning times.

Effect of pressure support ventilation vs. spontaneous ventilation on lung atelectasis during recovery from anesthesia for laparoscopic gastric sleeve surgery

Background & Objective: Pressure support ventilation (PSV) is a target pressure mode that offers breath by breath mode of ventilation support, started by patients, and timed to respiratory effort. The fundamental idea behind PSV is to assist spontaneous breathing in response to the patient-initiated breaths. We evaluated the effects of PSV and spontaneous ventilation during awakening from anesthesia on lung atelectasis in the patients following laparoscopic gastric sleeve surgery. Methodology: Following clearance from the institutional ethical council, we enrolled 64 patients and divided them into two groups at random; pressure support group (Group PS) to receive PSV, and control group or spontaneous group (Group S) to continue with spontaneous ventilation mode during awakening from anesthesia in the patients following laparoscopic gastric sleeve surgery. Results: In the pressure support group, atelectasis was less common than in the control group at PACU (P = 0.042). Over the first 48 h following surgery, there were substantial differences between the groups in the level of oxygen saturation as determined by pulse oximetry ≤ 92%. The incidence of SpO2 ≤ 92% during 48 h postoperatively in the Group S and Group PS was 34% vs 12% respectively. No patient needed mechanical ventilatory support during the 48 h postoperatively. Conclusions: Pressure support ventilation during the recovery from general anesthesia to patients after laparoscopic gastric sleeve surgery resulted in reduced incidence of postoperative atelectasis than those who were allowed spontaneous ventilation with occasional manual support. Abbreviations: PACU: Post-Anesthesia Care Unit; PEEP: Positive End Expiratory Pressure; PSV: Pressure support ventilation; VT: Tidal Volume. Key words: Gastric sleeve surgery; Laparoscopy; Lung atelectasis; Pressure support ventilation; Spontaneous ventilation. Citation: Aboelsuod MAA, Farhat AEA, Abdalla AM, Hassnin FSB. The effect of pressure support ventilation vs. spontaneous ventilation on lung atelectasis during recovery from anesthesia for laparoscopic gastric sleeve surgery. Anaesth. pain intensive care. 2023;27(3):301−307.DOI: 10.35975/apic.v27i3.2166 Received: March 09, 2023; Reviewed: March 20, 2023; Accepted: April 16, 2023.

The effectiveness of pressure support ventilation and T-piece in differing duration among weaning patients: A systematic review and network meta-analysis.

A spontaneous breathing trial (SBT) is recommended to help patients to liberate themselves from mechanical ventilation as soon as possible in the ICU. The respiratory workload in SBT, which depends on being with or without respiratory support and a specific time, is more accurate to reflect how much support the weaning patients need compared with only considering SBT technologies. To compare and rank the effectiveness of different respiratory workloads during SBT via differing technologies (Pressure Support Ventilation and T-piece) and differing duration (30 and 120 min) in SBTs. A comprehensive literature search was performed in six English electronic databases to identify eligible randomized controlled trials (RCTs) published before September 2020. The pooled risk ratio (RR) with 95% confidence interval (CI) was calculated by Markov chain Monte Carlo methods. A Bayesian network meta-analysis was conducted using "gemtc" version 0.8.2 of R software. Each intervention's ranking possibilities were calculated using the surface under the cumulative ranking analysis (SUCRA). A total of nine RCTs including 3115 participants were eligible for this network meta-analysis involving four different commonly used SBT strategies and four outcomes. The only statistically significant difference was between Pressure Support Ventilation (PSV) 30 min and T-piece 120 min in the outcome of the rate of success in SBTs (RR=0.91; 95% CI, 0.84-0.98). The cumulative rank probability showed that the rate of success in SBT from best to worst was PSV 30 min, PSV 120 min, T-piece 30 min and T-piece 120 min. PSV 30 min and PSV 120 min are more likely to have a higher rate of extubation (SUCRA values of 82.5% for 30 min PSV, 70.7% for 120 min PSV, 36.4% for T-piece 30 min, 10.4% for T-piece 120). Meanwhile, T-piece 120 min (SUCRA, 62.9%) and PSV 120 min (SUCRA, 60.9%) may result in lower reintubation rates, followed by T-piece 30 min (SUCRA, 41.8%) and PSV 30 min (SUCRA, 34.4%). In comprehensive consideration of four outcomes, regarding SBT strategies, 30-min PSV was superior in simple-to-wean patients. Besides, 120-min T-piece and 120-min PSV are more likely to achieve a lower reintubation rate. Thus, the impact of duration is more significant among patients who have a high risk of reintubation. It is still unclear whether the SBTs affect the outcome of mortality; further studies may need to explore the underlying mechanism.

Effects of pressure support ventilation on ventilator-induced lung injury in mild acute respiratory distress syndrome depend on level of positive end-expiratory pressure: A randomised animal study.

Harmful effects of spontaneous breathing have been shown in experimental severe acute respiratory distress syndrome (ARDS). However, in the clinical setting, spontaneous respiration has been indicated only in mild ARDS. To date, no study has compared the effects of spontaneous assisted breathing with those of fully controlled mechanical ventilation at different levels of positive end-expiratory pressure (PEEP) on lung injury in ARDS. To compare the effects of assisted pressure support ventilation (PSV) with pressure-controlled ventilation (PCV) on lung function, histology and biological markers at two different PEEP levels in mild ARDS in rats. Randomised controlled experimental study. Basic science laboratory. Thirty-five Wistar rats (weight ± SD, 310 ± 19) g received Escherichia coli lipopolysaccharide (LPS) intratracheally. After 24 h, the animals were anaesthetised and randomly allocated to either PCV (n=14) or PSV (n=14) groups. Each group was further assigned to PEEP = 2 cmH2O or PEEP = 5 cmH2O. Tidal volume was kept constant (≈6 ml kg). Additional nonventilated animals (n=7) were used as a control for postmortem analysis. Ventilatory and mechanical parameters, arterial blood gases, diffuse alveolar damage score, epithelial integrity measured by E-cadherin tissue expression, and biological markers associated with inflammation (IL-6 and cytokine-induced neutrophil chemoattractant, CINC-1) and type II epithelial cell damage (surfactant protein-B) were evaluated. In both PCV and PSV, peak transpulmonary pressure was lower, whereas E-cadherin tissue expression, which is related to epithelial integrity, was higher at PEEP = 5 cmH2O than at PEEP = 2 cmH2O. In PSV, PEEP = 5 cmH2O compared with PEEP = 2 cmH2O was associated with significantly reduced diffuse alveolar damage score [median (interquartile range), 11 (8.5 to 13.5) vs. 23 (19 to 26), P = 0.005] and expressions of IL-6 and CINC-1 (P = 0.02 for both), whereas surfactant protein-B mRNA expression increased (P = 0.03). These changes suggested less type II epithelial cell damage at a PEEP of 5 cmH2O. Peak transpulmonary pressure correlated positively with IL-6 [Spearman's rho (ρ) = 0.62, P = 0.0007] and CINC-1 expressions (ρ = 0.50, P = 0.01) and negatively with E-cadherin expression (ρ = -0.67, P = 0.0002). During PSV, PEEP of 5 cmH2O, but not a PEEP of 2 cmH2O, reduced lung damage and inflammatory markers while maintaining epithelial cell integrity.

Effect of Pressure Support Ventilation on Carboxyhemoglobin Toxicokinetic after Acute Carbon Monoxide Intoxication: a Swine Model.

In an experimental study on carbon monoxide (CO) exposure in swine, we aimed to compare the influence of oxygen therapy using a non-rebreathing mask (NRM) to continuous positive airway pressure (CPAP) and two pressure support ventilation (PSV) devices on the decrease of the terminal elimination half-life of carboxyhemoglobin (COHb t1/2). This was the primary outcome. Eight spontaneously breathing pigs were sedated by propofol and exposed to 940ppm CO several times (n = 25) to obtain COHb levels of 30%. CPAPb (high flow open system, CPAP Boussignac® [7.5 cmH2O]), PSV-Vy (open system, Vylife Boussignac®), and PSV-Leg (closed system, Legendair® [inspiratory/expiratory airway pressure 12/4 cmH2O]) devices were used in a randomized order and compared to NRM (O2 at 15lmin-1) and atmospheric air (AA). The primary outcome was COHb t1/2. Multiple comparisons were performed using Dunn's tests. Median FiO2 and minute ventilation were significantly higher in the PSV-Leg group than the NRM group (p < 0.05). Median COHb t1/2 was 251, 85, 82, 93, and 58min for AA, NRM, CPAPb, PSV-Vy, and PSV-Leg, respectively. All the interventions were superior to AA in terms of CO elimination (p < 0.001), but there was no statistically significant difference between CPAP or PSV and NRM. There was only a trend between PSV-Leg and NRM (p = 0.18). The median AUCs for ln (COHb) × time (h) were 170, 79, 83, 100, and 64 for AA, NRM, CPAPb, PSV-Vy, and PSV-Leg respectively, with a statistically significant difference only between AA and PSV-Leg (p = 0.002). In conclusion, in our study on CO intoxication in swine, the use of the closed PSV-Leg system led to the shortest COHb t1/2. These results suggest that PSV-Leg can be more efficient than NRM in eliminating CO and support the design of a clinical study to assess this hypothesis.

Effects of pressure-support ventilation with different levels of positive end-expiratory in a mild model of acute respiratory distress syndrome.

Pressure-support ventilation improves lung mechanics, blood gas exchange, hemodynamics, and work of breathing (WOB) in mild acute respiratory distress syndrome (ARDS) [1, 2]. Nevertheless, those beneficial effects could be dependent of positive end-expiratory pressure (PEEP) applied during mechanical ventilation. So far, no study has compared pressure-support ventilation (PSV) with pressure controlled ventilation (PCV) in different PEEP levels.

Comparison of the effect of pressure support ventilation and volume assured pressure support ventilation on weaning patients off mechanical ventilation after cardiac surgery

Background: Weaning from mechanical ventilation in the intensive care unit is an important step in the treatment process. More patients in less than 6 hours after cardiac surgery can be separated from mechanical ventilation and extubated. However, 20-40% of patients after cardiac surgery, due to dysfunctional ventilator weaning response (DVWR), still remain under mechanical ventilation. Therefore, a new method of mechanical ventilation such as volume assured pressure support ventilation (VAPSV) is needed in order to reduce the time of weaning from mechanical ventilation. Aim: To compare the effect of pressure support ventilation (PSV) with volume assured pressure support ventilation (VAPS) on time of weaning from mechanical ventilation in patients after cardiac surgery. Methods: This clinical trial study was conducted with the participation of 76 patients undergoing cardiac surgery in Imam Reza hospital of Mashhad, in 2013. Patients were randomly divided into two groups of pressure support ventilation (control) and pressure support ventilation with reliable volume (intervention) groups and the duration of mechanical ventilation and reintubation in both groups was recorded. The data were analyzed by SPSS software version 16 using t-student test and Mann-Whitney tests. Results: The mean duration of mechanical ventilation in VAPS group (65.7±5.8) significantly decreased compared with PSV (87.1± 5.8) (P = 0.015). Conclusion: Results of our study showed that VAPS method could reduce the time of weaning from mechanical ventilation and due to fewer complications; it can be used as an alternative method for weaning off mechanical ventilation.

Effect of pressure support ventilation during weaning on ventilation and oxygenation indices in healthy horses recovering from general anesthesia

ObjectiveTo determine if pressure support ventilation (PSV) weaning from general anesthesia affects ventilation or oxygenation in horses. Study designProspective randomized clinical study. AnimalsTwenty client‐owned healthy horses aged 5 ± 2 years, weighing 456 ± 90 kg. MethodsIn the control group (CG; n = 10) weaning was performed by a gradual decrease in respiratory rate (fR) and in the PSV group (PSVG; n = 10) by a gradual decrease in fR with PSV. The effect of weaning was considered suboptimal if PaCO2 > 50 mmHg, arterial pH < 7.35 plus PaCO2 > 50 mmHg or PaO2 < 60 mmHg were observed at any time after disconnection from the ventilator until 30 minutes after the horse stood. Threshold values for each index were established and the predictive power of these values was tested. ResultsPressure support ventilation group (PSVG) had (mean ± SD) pH 7.36 ± 0.02 and PaCO2 41 ± 3 mmHg at weaning and the average lowest PaO2 69 ± 6 mmHg was observed 15 minutes post weaning. The CG had pH 7.32 ± 0.02 and PaCO2 57 ± 6 mmHg at weaning and the average lowest PaO2 48 ± 5 mmHg at 15 minutes post weaning. No accuracy in predicting weaning effect was observed for fR (p = 0.3474), minute volume (p = 0.1153), SaO2 (p = 0.1737) and PaO2/PAO2 (p = 0.1529). A high accuracy in predicting an optimal effect of weaning was observed for VT > 10 L (p = 0.0001), fR/VT ratio ≤ 0.60 breaths minute−1 L−1 (p = 0.0001), VT/bodyweight > 18.5 mL kg−1 (p = 0.0001) and PaO2/FiO2 > 298 (p = 0.0002) at weaning. A high accuracy in predicting a suboptimal effect of weaning was observed for VT < 10 L (p = 0.0001), fR/VT ratio ≥ 0.60 breaths minute−1 L−1 (p = 0.0001) and Pe′CO2 ≥ 38 mmHg (p = 0.0001) at weaning. Conclusions and clinical relevancePressure support ventilation (PSV) weaning had a better respiratory outcome. A higher VT, VT/body weight, PaO2/FiO2 ratio and a lower fR/VT ratio and Pe′CO2 were accurate in predicting the effect of weaning in healthy horses recovering from general anesthesia.

Patient-ventilator interaction during pressure support ventilation and neurally adjusted ventilatory assist*

To compare the effect of pressure support ventilation and neurally adjusted ventilatory assist on breathing pattern, patient-ventilator synchrony, diaphragm unloading, and gas exchange. Increasing the level of pressure support ventilation can increase tidal volume, reduce respiratory rate, and lead to delayed ventilator triggering and cycling. Neurally adjusted ventilatory assist uses diaphragm electrical activity to control the timing and pressure of assist delivery and is expected to enhance patient-ventilator synchrony. Prospective, comparative, crossover study. Adult critical care unit in a tertiary university hospital. Fourteen nonsedated mechanically ventilated patients (n = 12 with chronic obstructive pulmonary disease). Patients were ventilated for 10-min periods, using two pressure support ventilation levels (lowest tolerable and +7 cm H2O higher) and two neurally adjusted ventilatory assist levels (same peak pressures and external positive end-expiratory pressure as with pressure support ventilation), delivered in a randomized order. Diaphragm electrical activity, respiratory pressures, air flow, volume, neural and ventilator respiratory rates, and arterial blood gases were measured. Peak pressures were 17 +/- 6 cm H2O and 24 +/- 6 cm H2O and 19 +/- 5 cm H2O and 24 +/- 6 cm H2O with high and low pressure support ventilation and neurally adjusted ventilatory assist, respectively. The breathing pattern was comparable with pressure support ventilation and neurally adjusted ventilatory assist during low assist; during higher assist, larger tidal volumes (p = .003) and lower breathing frequencies (p = .008) were observed with pressure support ventilation. Increasing the assist increased cycling delays only with pressure support ventilation (p = .003). Compared with pressure support ventilation, neurally adjusted ventilatory assist reduced delays of ventilator triggering (p < .001 for low and high assist) and cycling (high assist: p = .004; low assist: p = .04), and abolished wasted inspiratory efforts observed with pressure support ventilation in six subjects. The diaphragm electrical activity and pressure-time product for ventilator triggering were lower with neurally adjusted ventilatory assist (p = .005 and p = .02, respectively; analysis of variance). Arterial blood gases were similar with both modes. Neurally adjusted ventilatory assist can improve patient-ventilator synchrony by reducing the triggering and cycling delays, especially at higher levels of assist, at the same time preserving breathing and maintaining blood gases.

Effect of pressure support ventilation and positive end expiratory pressure on the rapid shallow breathing index in intensive care unit patients

We compared rapid shallow breathing index (RSBI) values under various ventilatory support settings prior to extubation. Prospective study in the intensive care unit at a university hospital. Thirty six patients ready for extubation. Patients were enrolled when receiving pressure support ventilation (PSV) of 5 cmH2O, PEEP of 5 cmH2O, and FIO2 of 40% (PS). Subsequently each patient received a trial of PSV of 0 cmH2O, PEEP of 5 cmH2O, and FIO2 of 40% (CPAP), a trial of PSV of 0 cmH2O, PEEP of 5 cmH2O and FIO2 of 21% (CPAP-R/A), and a 1-minute spontaneously breathing room air trial off the ventilator (T-piece). Trials were carried out in random order. Respiratory frequency (f) and tidal volume (VT) were measured during PS, CPAP, CPAP-R/A, and T-piece in all patients. RSBI (f/VT) was determined for each patient under all experimental conditions, and the average RSBI was compared during PS, CPAP, CPAP-R/A, and T-piece. RSBI was significantly smaller during PS (46+/-8 bpm/l), CPAP (63+/-13 bpm/l) and CPAP-R/A (67+/-14 bpm/l) vs. T-piece (100+/-23 bpm/l). There was no significant difference in RSBI between CPAP and CPAP-R/A. RSBI during CPAP and CPAP-R/A were significantly smaller than RSBI during T-piece. In all patients RSBI values were less than 105 bpm/l during PS, CPAP, and CPAP-R/A. However, during T-piece the RSBI increased to greater than 105bpm/l in 13 of 36 patients. In the same patient the use of PSV and/or PEEP as low as 5 cmH2O can influence the RSBI. In contrast, changes in FIO2 may have no effect on the RSBI.

Effects of pressure support ventilation and continuous positive airway pressure on diaphragm performance.

Many patients who are on mechanical ventilation are on ventilator modes called pressure support ventilation (PSV) and continuous positive airway pressure (CPAP) particularly when they are being weaned. As the diaphragm is responsible for approximately 75% of breathing, it is important to promote diaphragm shortening to optimize weaning from mechanical ventilation. The purpose of our 1998 quasi-experimental study was to explore the effects of PSV and CPVP on diaphragm shortening. An animal model was utilized using four Sprague-Dawley rats from the same litter purchased from Sasco (Kansas City, USA). Also measured in this study were intrathoracic pressure (DeltaITP), positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, central venous pressure (CVP) and mean arterial pressure (MAP). Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed. These results support that higher levels CPAP may hinder diaphragmatic function thus prolong mechanical ventilation. The purpose of this pilot study was to explore the effects of PSV and CPAP on diaphragm shortening. Also measured were DeltaITP, positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, CVP and MAP. Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed.

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Pressure support ventilation in adult respiratory distress syndrome: Short-term effects of a servocontrolled mode

Purpose : To assess the short-term effects of pressure support ventilation in adult respiratory distress syndrome (ARDS), we studied 17 patients with moderate to severe ARDS using mandatory rate ventilation (MRV), a servocontrolled mode of PSV having respiratory rate as the targeted parameter. Materials and Methods : Based on the duration of ARDS, the patients were divided into two groups: Group 1, early ARDS (duration up to 1 week), 10 patients; Group 2, intermediate ARDS (duration between 1 and 2 weeks). The patients were initially ventilated with assisted mechanical ventilation then with MRV, and finally with controlled mechanical ventilation. After a 20-minute period allowed for stabilization in each mode, ventilatory variables, gas exchange, hemodynamics, and patient's inspiratory effort were evaluated. Results : During MRV blood gases, airway pressures and hemodynamic variables remained within acceptable limits in all patients. Compared with assisted mechanical ventilation, during MRV, patients of group 1 decreased their V t and V̇ (from 0.64 ± 0.04 to 0.42 ± 0.03 L/sec) and increased their T i/T t (from 0.39 ± 0.03 to 0.52 ± 0.03). f did not change. P AO 2 - Pa O 2 and Q̇ s/Q̇ t decreased (from 306 ± 16 to 269 ± 15 mm Hg, and from 20.2 ± 1.4 to 17.5 ± 1.1, respectively), while Pa CO 2 increased (from 44 ± 3 to 50 ± 3 mm Hg). On the contrary, patients of group 2 increased their V t (from 0.69 ± 0.02 to 0.92 ± 0.09 L), decreased their f (from 22.3 ± 0.5 to 19.3 ± 0.3 b/min), although they did not change their V̇ and T i/T t. P AO 2 - Pa O 2 and Q̇ s/Q̇ t remained stable. Pa CO 2 diminished (from 39 ± 3 to 34 ± 3 mm Hg). Pressure support level was higher in group 2 than in group 1 (29.4 ± 3.0 v 19.8 ± 2.9 cm H 2O). Conclusions : We conclude that (1) PSV delivered by MRV may adequately ventilate patients with moderate to severe ARDS, preserving gas exchange and hemodynamics, at least for the short period tested; (2) early and intermediate ARDS respond in a different manner to MRV in terms of breathing pattern, gas exchange, and level of pressure assistance; and (3) patients with early ARDS are those who have an improvement in intrapulmonary oxygenation probably due, at least in part, to alveolar recruitment augmented by active diaphragmatic contraction.

Effects of pressure support ventilation, bi-level positive airway pressure, and volume-proportional assist on breathing with elevated respiratory system elastance

Fully awake subjects preferred ventilatory assist modes supporting every breath, like PS or PA., to the potentially unsynchronous BIPAP. — In pure volume-proportional assist, the relatively high PAO at end-inspiration seemed to contribute to discomfort with high assist levels. So the addition of a flow-proportional component, which would tend to come into effect earlier in inspiration, might allow higher levels of PA with equal patient comfort.

Comparative effects of pressure support ventilation and intermittent positive pressure breathing (IPPB) in non-intubated healthy subjects

We compared the efficacy of three devices delivering assisted non-invasive ventilation with different working mechanisms, during room air breathing and during CO2-induced hyperventilation. In seven healthy volunteers, breathing pattern, respiratory muscle activity and comfort were assessed: during unassisted spontaneous breathing through a mouth-piece (SB); during assisted breathing with a device delivering inspiratory pressure support (IPS); and with two devices delivering intermittent positive pressure breathing (IPPB), the Monaghan 505 (IPPB1), and the CPU 1 ventilator (IPPB2). All three devices were set at 10 cmH2O of maximal pressure. During room air breathing, the work of breathing expressed as power, was significantly greater with the two IPPB devices than with the two other modes (IPPB1 and IPPB2 7.3 +/- 5.2 and 7.2 +/- 6.2 J.min-1, respectively, versus SB and IPS 2.4 +/- 0.7 and 2.3 +/- 3.3 J.min-1, respectively). The difference did not reach the statistical significance for the pressure-time product (PTP). Discomfort was also greater during the IPPB modes. During CO2-induced hyperventilation, considerable differences in power of breathing were found between the two IPPB devices and the other two modes. The PTP was also much higher with IPPB. Transdiaphragmatic pressure was significantly smaller during IPS than during the three other modes (IPS 18 +/- 2.6 cmH2O versus SB 22 +/- 2.6, IPPB1 32 +/- 5.2, and IPPB2: 28 +/- 5.2). Maximal discomfort was observed during the IPPB modes and was correlated with the magnitude of transdiaphragmatic pressure (r = 0.60). Despite similarities in their operational principles, IPS and IPPB had very different effects on respiratory muscle activity in healthy non-intubated subjects. IPPB machines not only failed to reduce patient's effort but also induced a significant level of extra work by comparison to spontaneous ventilation at ambient pressure. Great caution is, therefore, needed in the use of patient-triggered devices for non-intubated patients with acute respiratory failure.

Comparative evaluation of diaphragmatic activity during pressure support ventilation and intermittent mandatory ventilation in animal model.

The aim of the present study is a comparative evaluation of the effects of pressure support ventilation (PSV) and intermittent mandatory ventilation (IMV) on diaphragmatic activity in rabbit model of neonate. The animals were divided into a PSV group and an IMV group. In the IMV group, spontaneous breathing and four kinds of IMV rate (5, 10, 15, and 20/min) were applied (Ventilator: Bear BP200, peak inspiratory pressure [PIP]: 12 cm H2O, inspiratory time: 0.6 s). In the PSV group, spontaneous breathing and four levels of PSV (3, 6, 9, and 12 cm H2O) were applied (Ventilator: VIP Bird, flow triggering). Airway pressure (Paw), flow (V), esophageal pressure (Pes), integrated diaphragmatic electromyogram (Edi), and arterial gas data were measured. Amplitudes of Pes and Edi were expressed as percentages (% Edi and % Pes) of the control value during spontaneous breathing to evaluate diaphragmatic activity. Lower IMV rates did not reduce diaphragmatic activity. Approximately half of diaphragmatic activity of control remained even at IMV 15/min. Diaphragmatic activity disappeared at IMV20/min. In contrast, PSV reduced Edi and Pes linearly according to support level. In conclusion, diaphragmatic activity could be reduced more gradually with PSV than IMV by altering ventilatory support level.

Effect of Pressure-Support Ventilation on Breathing Pattern during Desflurane Anesthesia

Effect of Pressure-Support Ventilation on Breathing Pattern during Desflurane Anesthesia

Differences in end-tidal carbon dioxide and breathing patterns in ventilator-dependent patients using pressure support ventilation

Although several investigators have assessed the effects of pressure support ventilation on tidal volume and breathing patterns, none have investigated the combination of breathing patterns and end-tidal carbon dioxide in ventilator-dependent patients. To determine the differences in end-tidal carbon dioxide and breathing patterns at varying pressure support ventilation levels in ventilator-dependent patients. Breathing patterns were measured with a plethysmograph and a ventilator. End-tidal carbon dioxide was measured by connecting the capnography sampler to the exhalation port of intubated patients. All equipment was connected to a five-channel recorder for data collection. The respiratory rate, tidal volume, minute ventilation, end-tidal carbon dioxide concentration, and chest and abdominal movement were recorded at 10-minute intervals at four pressure support ventilation levels (0, 10, 15, and 20 cm H2O). As pressure support ventilation increased, the respiratory rate, end-tidal carbon dioxide concentration, and asynchronous movement of chest and abdomen decreased. Tidal volume increased with higher pressure support ventilation levels. Pressure support ventilation prevents asynchronous chest and abdominal movement and lowers the level of end-tidal carbon dioxide. Pressure support ventilation offers clinicians a way to lower the elevated carbon dioxide level that often occurs in critically ill patients. Increasing tidal volume and reducing the work of breathing by using pressure support ventilation may reduce diaphragm fatigue in ventilator-dependent patients.

The Effectiveness of Pressure Support Ventilation for Mechanical Ventilatory Support in Children

The rapid respiratory frequency of children may lead to patient-ventilator asynchrony and increase the work of breathing during mechanical ventilation, and the use of a small endotracheal tube and a demand valve can further increase this work of breathing. Although pressure support ventilation (PSV) is well known to reduce the work of breathing in adults, there are no reports regarding clinical studies of PSV in children. Therefore, the effect of PSV on breathing patterns and the work of breathing in children was studied. Six children (3-5 yr of age) were studied in the immediate postoperative period. Three levels of PSV, 0, 5, and 10 cmH2O, were employed. Airway pressure, flow, tidal volume, minute ventilation, and respiratory frequency were measured. To assess the work of breathing, the negative deflection of esophageal pressure (delta Pes) caused by inspiratory effort was measured. The inspiratory work of breathing was also estimated directly by measuring the esophageal pressure-volume loop using the Campbell technique. Although minute ventilation did not change with PSV, tidal volume increased and respiratory frequency decreased with increasing levels of PSV. The delta Pes decreased markedly from 8.9 cmH2O with PSV of 0 cmH2O to 5.7 cmH2O with PSV of 5 cmH2O and 2.7 cmH2O with PSV of 10 cmH2O. The mechanical work of breathing also decreased from 0.743 Joules/l with PSV of 0 cmH2O to 0.463 Joules/l with PSV of 5 cmH2O and 0.196 Joules/l with PSV of 10 cmH2O. It was concluded that PSV can effectively augment spontaneous breathing and reduce the work of breathing in children.

Physiologic Evaluation of Pressure Support Ventilation by Nasal Mask in Patients with Stable COPD

We evaluated the physiologic effects of pressure support ventilation by nasal route (NPSV) in eight patients with severe stable COPD and chronic hypercapnia who were randomly submitted to 2-h sessions of NPSV both with a portable ventilator (Respironics BIPAP device) and with a standard ventilator (Bird 6400ST device) at an inspiratory airway pressure of 22 cm H2O. Two sessions with each ventilator were performed using an FIO2 of 0.21 in each patient on two consecutive days. One patient did not tolerate either form of ventilation. Comparison of spontaneous with BIPAP ventilation showed a significant improvement in pH, PaCO2, and PaO2. Ventilatory pattern assessed by a respiratory inductive plethysmograph showed a significant increase in minute ventilation (VE), VT, and Ttot. Integrated surface diaphragmatic EMG activity measured only during BIPAP device ventilation decreased from that measured during spontaneous breathing. Similar changes in blood gases and ventilatory pattern were observed during ventilation by the Bird 6400ST except for VT/Ti ratio, which significantly increased. Comparison of baseline with measurements performed 12 h after the whole cycle of treatment showed a significant increase in pH and VE and a decrease in PaCO2. We conclude that short-term NPSV may be useful in improving respiratory pattern and blood gases in stable COPD patients with chronic hypercapnia.