Impact of the prolonged slow expiratory maneuver on respiratory mechanics in wheezing infants

OBJECTIVE:

To evaluate changes in respiratory mechanics and tidal volume (V_T) in wheezing infants in spontaneous ventilation after performing the technique known as the prolonged, slow expiratory (PSE) maneuver.

METHODS:

We included infants with a history of recurrent wheezing and who had had no exacerbations in the previous 15 days. For the assessment of the pulmonary function, the infants were sedated and placed in the supine position, and a face mask was used and connected to a pneumotachograph. The variables of tidal breathing (V_T and RR) as well as those of respiratory mechanics-respiratory system compliance (Crs), respiratory system resistance (Rrs), and the respiratory system time constant (prs)-were measured before and after three consecutive PSE maneuvers.

RESULTS:

We evaluated 18 infants. The mean age was 32 ± 11 weeks. After PSE, there was a significant increase in V_T (79.3 ± 15.6 mL vs. 85.7 ± 17.2 mL; p = 0.009) and a significant decrease in RR (40.6 ± 6.9 breaths/min vs. 38.8 ± 0,9 breaths/min; p = 0.042). However, no significant differences were found in the variables of respiratory mechanics (Crs: 11.0 ± 3.1 mL/cmH₂O vs. 11.3 ± 2.7 mL/cmH₂O; Rrs: 29.9 ± 6.2 cmH₂O • mL⁻¹ • s⁻¹ vs. 30.8 ± 7.1 cmH₂O • mL⁻¹ • s⁻¹; and prs: 0.32 ± 0.11 s vs. 0.34 ±0.12 s; p > 0.05 for all).

CONCLUSIONS:

This respiratory therapy technique is able to induce significant changes in V_T and RR in infants with recurrent wheezing, even in the absence of exacerbations. The fact that the variables related to respiratory mechanics remained unchanged indicates that the technique is safe to apply in this group of patients. Studies involving symptomatic infants are needed in order to quantify the functional effects of the technique.     

Higher effective oronasal versus nasal continuous positive airway pressure in obstructive sleep apnea: Effect of mandibular stabilization

BACKGROUND:

In some individuals with obstructive sleep apnea (OSA), oronasal continuous positive airway pressure (CPAP) leads to poorer OSA correction than nasal CPAP. The authors hypothesized that this results from posterior mandibular displacement caused by the oronasal mask.

OBJECTIVE:

To test this hypothesis using a mandibular advancement device (MAD) for mandibular stabilization.

METHODS:

Subjects whose OSA was not adequately corrected by oronasal CPAP at pressures for which nasal CPAP was effective were identified. These subjects underwent polysomnography (PSG) CPAP titration with each nasal and oronasal mask consecutively, with esophageal pressure and leak monitoring, to obtain the effective pressure (Peff) of CPAP for correcting obstructive events with each mask (maximum 20 cmH₂O). PSG titration was repeated using a MAD in the neutral position. Cephalometry was performed.

RESULTS:

Six subjects with mean (± SD) nasal Peff 10.4±3.0 cmH₂O were studied. Oronasal Peff was greater than nasal Peff in all subjects, with obstructive events persisting at 20 cmH₂O by oronasal mask in four cases. This was not due to excessive leak. With the MAD, oronasal Peff was reduced in three subjects, and Peff <20 cmH₂O could be obtained in two of the four subjects with Peff >20 cmH₂O by oronasal mask alone. Subjects’ cephalometric variables were similar to published norms.

CONCLUSION:

In subjects with OSA with higher oronasal than nasal Peff, this is partially explained by posterior mandibular displacement caused by the oronasal mask. Combination treatment with oronasal mask and MAD may be useful in some individuals if a nasal mask is not tolerated.     

Acute Effects of Continuous Positive Air way Pressure on Pulse Pressure in Chronic Heart Failure

Background

Patients with heart failure (HF) have left ventricular dysfunction and reduced mean arterial pressure (MAP). Increased adrenergic drive causes vasoconstriction and vessel resistance maintaining MAP, while increasing peripheral vascular resistance and conduit vessel stiffness. Increased pulse pressure (PP) reflects a complex interaction of the heart with the arterial and venous systems. Increased PP is an important risk marker in patients with chronic HF (CHF). Non-invasive ventilation (NIV) has been used for acute decompensated HF, to improve congestion and ventilation through both respiratory and hemodynamic effects. However, none of these studies have reported the effect of NIV on PP.

Objective

The objective of this study was to determine the acute effects of NIV with CPAP on PP in outpatients with CHF.

Methods

Following a double-blind, randomized, cross-over, and placebo-controlled protocol, twenty three patients with CHF (17 males; 60 ± 11 years; BMI 29 ± 5 kg/cm², NYHA class II, III) underwent CPAP via nasal mask for 30 min in a recumbent position. Mask pressure was 6 cmH₂O, whereas placebo was fixed at 0-1 cmH₂O. PP and other non invasive hemodynamics variables were assessed before, during and after placebo and CPAP mode.

Results

CPAP decreased resting heart rate (Pre: 72 ± 9; vs. Post 5 min: 67 ± 10 bpm; p < 0.01) and MAP (CPAP: 87 ± 11; vs. control 96 ± 11 mmHg; p < 0.05 post 5 min). CPAP decreased PP (CPAP: 47 ± 20 pre to 38 ± 19 mmHg post; vs. control: 42 ± 12 mmHg, pre to 41 ± 18 post p < 0.05 post 5 min).

Conclusion

NIV with CPAP decreased pulse pressure in patients with stable CHF. Future clinical trials should investigate whether this effect is associated with improved clinical outcome.     

Chest compression with a higher level of pressure support ventilation: effects on secretion removal,hemodynamics, and respiratory mechanics in patients on mechanical ventilation

OBJECTIVE:

To determine the efficacy of chest compression accompanied by a 10-cmH₂O increase in baseline inspiratory pressure on pressure support ventilation, in comparison with that of aspiration alone, in removing secretions, normalizing hemodynamics, and improving respiratory mechanics in patients on mechanical ventilation.

METHODS:

This was a randomized crossover clinical trial involving patients on mechanical ventilation for more than 48 h in the ICU of the Porto Alegre Hospital de Clínicas, in the city of Porto Alegre, Brazil. Patients were randomized to receive aspiration alone (control group) or compression accompanied by a 10-cmH₂O increase in baseline inspiratory pressure on pressure support ventilation (intervention group). We measured hemodynamic parameters, respiratory mechanics parameters, and the amount of secretions collected.

RESULTS:

We included 34 patients. The mean age was 64.2 ± 14.6 years. In comparison with the control group, the intervention group showed a higher median amount of secretions collected (1.9 g vs. 2.3 g; p = 0.004), a greater increase in mean expiratory tidal volume (16 ± 69 mL vs. 56 ± 69 mL; p = 0.018), and a greater increase in mean dynamic compliance (0.1 ± 4.9 cmH₂O vs. 2.8 ± 4.5 cmH₂O; p = 0.005).

CONCLUSIONS:

In this sample, chest compression accompanied by an increase in pressure support significantly increased the amount of secretions removed, the expiratory tidal volume, and dynamic compliance. (ClinicalTrials.gov Identifier:{"type":"clinical-trial","attrs":{"text":"NCT01155648","term_id":"NCT01155648"}}NCT01155648 [http://www.clinicaltrials.gov/])     

Acute lung injury induced by the intravenous administration of cigarette smoke extract

OBJECTIVE:

To investigate the acute effects of intravenous administration of cigarette smoke extract (CSE) on histological, inflammatory, and respiratory function parameters in rats, as well as to compare this potential acute lung injury (ALI) model with that with the use of oleic acid (OA).

METHODS:

We studied 72 Wistar rats, divided into four groups: control (those injected intravenously with saline); CSE (those injected intravenously with CSE and saline); OA (those injected intravenously with saline and OA); and CSE/OA (those injected intravenously with CSE and OA).

RESULTS:

Mean lung compliance was significantly lower in the OA and CSE/OA groups (2.12 ± 1.13 mL/cmH₂O and 1.82 ± 0.77 mL/cmH₂O, respectively)than in the control group (3.67 ± 1.38 mL/cmH₂O). In bronchoalveolar lavage fluid, the proportion of neutrophils was significantly higher in the OA and CSE/OA groups than in the control group, as was the activity of metalloproteinases 2 and 9. Pulmonary involvement, as assessed by morphometry, was significantly more severe in the OA and CSE/OA groups (72.9 ± 13.8% and 77.6 ± 18.0%, respectively) than in the control and CSE groups (8.7 ± 4.1% and 32.7 ± 13.1%, respectively), and that involvement was significantly more severe in the CSE group than in the control group.

CONCLUSIONS:

The intravenous administration of CSE, at the doses and timing employed in this study, was associated with minimal ALI. The use of CSE did not potentiate OA-induced ALI. Additional studies are needed in order to clarify the potential role of this model as a method for studying the mechanisms of smoking-induced lung injury.     

Hemodynamic Effects of Noninvasive Ventilation in Patients with Venocapillary Pulmonary Hypertension

Background

The hemodynamic effects of noninvasive ventilation with positive pressure in patients with pulmonary hypertension without left ventricular dysfunction are not clearly established.

Objectives

Analyze the impact of increasing airway pressure with continuous positive airway pressure on hemodynamic parameters and, in particular, on cardiac output in patients with variable degrees of pulmonary hypertension.

Methods

The study included 38 patients with pulmonary hypertension caused by mitral stenosis without left ventricular dysfunction or other significant valvulopathy. The hemodynamic state of these patients was analyzed in three conditions: baseline, after continuous positive pressure of 7 cmH₂O and, finally, after pressure of 14 cmH₂O.

Results

The population was composed of predominantly young and female individuals with significant elevation in pulmonary arterial pressure (mean systolic pressure of 57 mmHg). Of all variables analyzed, only the right atrial pressure changed across the analyzed moments (from the baseline condition to the pressure of 14 cmH₂O there was a change from 8 ± 4 mmHg to 11 ± 3 mmHg, respectively, p = 0.031). Even though there was no variation in mean cardiac output, increased values in pulmonary artery pressure were associated with increased cardiac output. There was no harmful effect or other clinical instability associated with use application of airway pressure.

Conclusion

In patients with venocapillary pulmonary hypertension without left ventricular dysfunction, cardiac output response was directly associated with the degree of pulmonary hypertension. The application of noninvasive ventilation did not cause complications directly related to the ventilation systems.     

A chest drainage system with a real-time pressure monitoring device

Background

Tube thoracostomy is a common procedure. A chest bottle may be used to both collect fluids and monitor the recovery of the chest condition. The presence of the “tidaling phenomenon” in the bottle can be reflective of the extent of patient’s recovery.

Objectives

However, current practice essentially depends on gross observation of the bottle. The device used here is designed for a real-time monitoring of change in pleural pressure to allow clinicians to objectively determine when the lung has recovered, which is crucially important in order to judge when to remove the chest tube.

Methods

The device is made of a pressure sensor with an operating range between −100 to +100 cmH₂O and an amplifying using the “Wheatstone bridge” concept. Recording and analysis was performed with LABview software. The data can be shown in real-time on screen and also be checked retrospectively. The device was connected to the second part of a three-bottle drain system by a three-way connector.

Results

The test animals were two 40-kg pigs. We used a thoracoscopic procedure to create an artificial lung laceration with endoscopic scissors. Active air leaks could result in vigorous tidaling phenomenon up to 20 cmH₂O. In the absence of gross tidaling phenomenon, the pressure changes were around 0.25 cmH₂O.

Conclusions

This real-time pleural pressure monitoring device can help clinicians objectively judge the extent of recovery of the chest condition. It can be used as an effective adjunct with the current chest drain system.     

Prophylactic positive end-expiratory pressure and postintubation hemodynamics: An interventional, randomized study

OBJECTIVE:

To investigate the hemodynamic and outcome effects of implementing prophylactic positive end-expiratory pressure (PEEP) versus zero end-expiratory pressure (ZEEP) in patients during the postintubation period in the emergency setting.

METHODS:

The present study was a prospective, single-centre, interventional, single-blinded randomized trial performed in a 16-bed medical intensive care unit. The study cohort consisted of consecutive patients who urgently required intubation. During the postintubation period, patients received either 5 cmH₂O PEEP or ZEEP. The primary aim was to assess the variation in mean arterial pressure (MAP) from baseline up to 90 min postintubation. The secondary aim was to determine the mean duration of intubation, level of MAP support after intubation and 28-day mortality.

RESULTS:

Seventy-five consecutive patients with similar mean (± SD) baseline characteristics and preintubation MAP (76±18 mmHg in the ZEEP group and 78.5±23 mmHg in the PEEP group, P=Not significant [NS]) were studied. The final analysis was performed in 33 patients in the ZEEP group and 30 patients in the PEEP group. Regarding outcome measures following intubation, delta MAP (ie, the difference between the lowest MAP values from baseline) was not differentially affected in either group (P=NS); the mean durations of intubation were similar (ZEEP 9.2±8.5 days versus PEEP 9.2±8.8 days, P=NS); 28-day mortality was not discriminative (ZEEP 14 of 33, PEEP nine of 30; P=NS); and levels of MAP support after intubation were comparable between the two groups. .

CONCLUSION:

In the present trial, there was no evidence that implementing a prophylactic PEEP of 5 cmH₂O adversely affects short-term hemodynamics or outcome in medical intensive care patients during the postintubation period.     

Evaluation of manual resuscitators used in ICUs in Brazil

OBJECTIVE:

To evaluate the performance of manual resuscitators (MRs) used in Brazil in accordance with international standards.

METHODS:

Using a respiratory system simulator, four volunteer physiotherapists employed eight MRs (five produced in Brazil and three produced abroad), which were tested for inspiratory and expiratory resistance of the patient valve; functioning of the pressure-limiting valve; and tidal volume (V_T) generated when the one-handed and two-handed techniques were used. The tests were performed and analyzed in accordance with the American Society for Testing and Materials (ASTM) F920-93 criteria.

RESULTS:

Expiratory resistance was greater than 6 cmH₂O . L⁻¹ . s⁻¹ in only one MR. The pressure-limiting valve, a feature of five of the MRs, opened at low pressures (< 17 cmH₂O), and the maximal pressure was 32.0-55.9 cmH₂O. Mean V_T varied greatly among the MRs tested. The mean V_T values generated with the one-handed technique were lower than the 600 mL recommended by the ASTM. In the situations studied, mean V_T was generally lower from the Brazilian-made MRs that had a pressure-limiting valve.

CONCLUSIONS:

The resistances imposed by the patient valve met the ASTM criteria in all but one of the MRs tested. The pressure-limiting valves of the Brazilian-made MRs usually opened at low pressures, providing lower V_T values in the situations studied, especially when the one-handed technique was used, suggesting that both hands should be used and that the pressure-limiting valve should be closed whenever possible.     

Benefit of a low-fat over high-fat diet on vascular health during alternate day fasting

Background:

Alternate day fasting (ADF) with a low-fat (LF) diet improves brachial artery flow-mediated dilation (FMD). Whether these beneficial effects can be reproduced with a high-fat (HF) diet remains unclear.

Objective:

This study compared the effects of ADF-HF to ADF-LF regimens on FMD. The role that adipokines have in mediating this effect was also investigated.

Methods:

Thirty-two obese subjects were randomized to an ADF-HF (45% fat) or ADF-LF diet (25% fat), consisting of two phases: (1) a 2-week baseline weight maintenance period and (2) an 8-week ADF weight loss period. Food was provided throughout the study.

Results:

Body weight was reduced (P<0.0001) in the ADF-HF (4.4±1.0 kg) and ADF-LF group (3.7±0.7 kg). FMD decreased (P<0.05) by ADF-HF relative to baseline (7±1 to 5±2%) and increased (P<0.05) by ADF-LF (5±1 to 7±2%). Blood pressure remained unchanged in both groups. Adiponectin increased (P<0.05) in the ADF-HF (43±7%) and ADF-LF group (51±7%). Leptin and resistin decreased (P<0.05) in the ADF-HF (32±5% 23±5%) and ADF-LF group (30±3% 27±4%). Increases in adiponectin were associated with augmented FMD in the ADF-LF group only (r=0.34, P=0.03).

Conclusion:

Thus, improvements in FMD with ADF may only occur with LF diets and not with HF diets, and adipokines may not have a significant role in mediating this effect.     

Effects of yoga breathing exercises on pulmonary function in patients with Duchenne muscular dystrophy: an exploratory analysis,

OBJECTIVE:

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy in children, and children with DMD die prematurely because of respiratory failure. We sought to determine the efficacy and safety of yoga breathing exercises, as well as the effects of those exercises on respiratory function, in such children.

METHODS:

This was a prospective open-label study of patients with a confirmed diagnosis of DMD, recruited from among those followed at the neurology outpatient clinic of a university hospital in the city of São Paulo, Brazil. Participants were taught how to perform hatha yoga breathing exercises and were instructed to perform the exercises three times a day for 10 months.

RESULTS:

Of the 76 patients who entered the study, 35 dropped out and 15 were unable to perform the breathing exercises, 26 having therefore completed the study (mean age, 9.5 ± 2.3 years; body mass index, 18.2 ± 3.8 kg/m²⁾. The yoga breathing exercises resulted in a significant increase in FVC (% of predicted: 82.3 ± 18.6% at baseline vs. 90.3 ± 22.5% at 10 months later; p = 0.02) and FEV₁ (% of predicted: 83.8 ± 16.6% at baseline vs. 90.1 ± 17.4% at 10 months later; p = 0.04).

CONCLUSIONS:

Yoga breathing exercises can improve pulmonary function in patients with DMD.     

Prophylactic use of noninvasive positive pressure ventilation in post-thoracic surgery patients: A prospective randomized control study

Objective

Prospective randomized controlled study was conducted to explore the effects and safety of prophylactic use of noninvasive positive pressure ventilation (NPPV) in post-thoracic surgery (PTS) patients, especially on the lung re-expansion, lung function change and postoperative pulmonary complications (PPCs).

Methods

Fifty PTS patients met the inclusion criterion were enrolled in the study. All subjects were randomly divided into conventional treatment (control) group and NPPV group. NPPV group received intermittent NPPV therapy in first three days of PTS. BiPAP ventilator was used with S/T mode in the study. The average IPAP was (13±3.2)cmH₂O (ranged from 7 to 18 cmH₂O) and EPAP was 4cmH₂O. Total ventilation time was (13.5±4.9) hours (ranged from 6.5 to 23 hours). PPCs rate, lung re-expansion, the volume of residual cavity, lung function and tolerance to NPPV were assessed with chest roentgenography, CT scan, lung function testing and clinical evaluation before and one week after surgery.

Results

1. There was no significant difference of total PPCs rate during hospitalization between the two groups (5/23 in NPPV group vs 6/27 in control group, P= 0.967). Multiple factorial logistic regression analysis showed that COPD was a risk factor for PPCs (B=1.705, P=0.027). 2. Compared with control group, NPPV therapy reduced inadequate lung expansion rate (3/23 vs 13/27, P=0.008) and volume of residual cavity calculated with CT scan [(31.9±71.7)ml vs (63.6±78.3)ml, P=0.02]. However, there were no significant difference in the change of lung function parameters after operation between the two groups (all P>0.05). No significant adverse effects of NPPV were found in the present study.

Conclusions

In the current study of prophylactic application of NPPV in post-thoracic surgery patients, the use of NPPV resulted in improved lung re-expansion, but had no significant effects on post-operative pulmonary complications and lung functions.     

Evaluation of a novel method of teaching endobronchial ultrasound: Physician- versus respiratory therapist-proctored simulation training

BACKGROUND:

Computer endobronchial ultrasound (EBUS) simulators have been demonstrated to improve trainee procedural skills before attempting to perform EBUS procedures on patients.

OBJECTIVE:

To compare EBUS performance following training with computer simulation proctored by EBUS-trained respiratory therapists versus the same simulation training proctored by an interventional respirologist.

METHODS:

The present analysis was a prospective study of respiratory medicine trainees learning EBUS. Two cohorts of trainees were evaluated using a previously validated method using simulated cases with performance metrics measured by the simulator. Group 1 underwent EBUS training by performing 15 procedures on an EBUS simulator (n=4) proctored by an interventional respirologist. Group 2 received identical training proctored by a respiratory therapist with special training in EBUS (n=10).

RESULTS:

No significant differences between group 1 and group 2 were apparent for the primary outcome measures of total procedure time (15.15±1.34 min versus 14.78±2.88 min; P=0.816), the percentage of lymph nodes successfully identified (88.8±5.4 versus 80.91±8.9; P=0.092) or the percentage of successful biopsies (100.0±0.0 versus 98.75±3.95; P=0.549). The learning curves were similar between groups, and did not show an obvious plateau after 19 simulated procedures in either group.

DISCUSSION:

Acquisition of basic EBUS technical skills can be achieved using computer EBUS simulation proctored by specially trained respiratory therapists or by an interventional respirologist. There appeared to be no significant advantage to having an interventional respirologist proctor the computer EBUS simulation.     

Six-minute walk test and respiratory muscle strength in patients with uncontrolled severe asthma: a pilot study

OBJECTIVE:

To evaluate respiratory muscle strength and six-minute walk test (6MWT) variables in patients with uncontrolled severe asthma (UCSA).

METHODS:

This was a cross-sectional study involving UCSA patients followed at a university hospital. The patients underwent 6MWT, spirometry, and measurements of respiratory muscle strength, as well as completing the Asthma Control Test (ACT). The Mann-Whitney test was used in order to analyze 6MWT variables, whereas the Kruskal-Wallis test was used to determine whether there was an association between the use of oral corticosteroids and respiratory muscle strength.

RESULTS:

We included 25 patients. Mean FEV₁ was 58.8 ± 21.8% of predicted, and mean ACT score was 14.0 ± 3.9 points. No significant difference was found between the median six-minute walk distance recorded for the UCSA patients and that predicted for healthy Brazilians (512 m and 534 m, respectively; p = 0.14). During the 6MWT, there was no significant drop in SpO₂. Mean MIP and MEP were normal (72.9 ± 15.2% and 67.6 ± 22.2%, respectively). Comparing the patients treated with at least four courses of oral corticosteroids per year and those treated with three or fewer, we found no significant differences in MIP (p = 0.15) or MEP (p = 0.45).

CONCLUSIONS:

Our findings suggest that UCSA patients are similar to normal subjects in terms of 6MWT variables and respiratory muscle strength. The use of oral corticosteroids has no apparent impact on respiratory muscle strength.     

The application of bi-level positive airway pressure in patients with severe pneumonia and acute respiratory failure caused by influenza A (H1N1) virus

Objective

To evaluate the effect of noninvasive Bi-level Positive Airway Pressure (BiPAP) ventilation on the severe influenza A virus associated with pneumonia and acute respiratory failure (ARF).

Methods

Based on conventional therapy via face mask using BiPAP ventilator positive airway pressure ventilation in the treatment of severe pneumonia caused by influenza A (H1N1) virus with acute respiratory failure (ARF) in 18 cases, we observed and evaluated the therapeutic effects.

Results

PaO2 and SaO2 before and after treatment were (48.85 ± 12.15)mmHg, (68.56 ± 16.25) mmHg and (80 ± 6)%, (92 ± 5)%, respectively. The results were significantly different (P<0.05) before and after treatment. Endotracheal intubation rate was 25% (6/24) and case-fatality rate was 8.3% (2/24).

Conclusion

BiPAP ventilator airway pressure by face mask ventilation can reduce the rate of endotracheal intubation in the treatment of severe pneumonia caused by influenza A (H1N1) virus in acute respiratory failure. It could be an effective approach in the emergency treatment with clinical value.     

Initial synchronized intermittent mandatory ventilation versus assist/control ventilation in treatment of moderate acute respiratory distress syndrome: a prospective randomized controlled trial

Background

Assist/control (A/C) ventilation may induce delirium in patients with acute respiratory distress syndrome (ARDS). We conducted a trial to determine whether initial synchronized intermittent mandatory ventilation with pressure support (SIMV + PS) could improve clinical outcomes in these patients.

Methods

Intubated patients with moderate ARDS were enrolled and we compared SIMV + PS with A/C. Identical sedation, analgesia and ventilation strategies were performed. The co-primary outcomes were early (≤72 h) partial pressure of arterial oxygen to fraction of inspired oxygen (PaO₂/FiO₂) and incidence of delirium. The secondary outcomes were all-cause in-hospital mortality, dosages of analgesics and sedatives, incidence of patient-ventilator asynchrony, and duration of mechanical ventilation and hospital stay.

Results

We screened 2,684 patients and 40 patients were enrolled in our study. In SIMV + PS, early (≤72 h) PaO₂/FiO₂ was greater improved than that at baseline and that in A/C (P<0.05) with lower positive end-expiratory pressure (PEEP) (8.7±3.0 vs. 10.3±3.2, P<0.001) and FiO₂ (58%±18% vs. 67%±19%, P<0.001). We found more SIMV + PS success (defined as SIMV + PS successfully applied without switching to A/C) (100.0% vs. 16.7%, P<0.001), less male (46.3% vs. 85.7%, P=0.015) and pulmonary etiology of ARDS (53.8% vs. 92.9%, P=0.015), and lower PEEP (9.1±3.1 vs. 10.3±3.3, P=0.004) and FiO₂ (58%±19% vs. 71%±19%, P<0.001) in survival patients. However, there were no significant differences in incidence of delirium and mortality, dosages of analgesics and sedatives, incidence of patient-ventilator asynchrony, duration of mechanical ventilation and hospital stay (P>0.05).

Conclusions

In patients with moderate ARDS, SIMV + PS can safely and effectively improve oxygenation, but does not decrease mortality, incidence of delirium and patient-ventilator asynchrony, dosages of analgesics and sedatives, and duration of mechanical ventilation and hospital stay.     

Substrate-dependent modulation of oxidative phosphorylation in isolated mitochondria following in vitro hypoxia and reoxygenation injury

BACKGROUND/OBJECTIVES:

Previous studies using isolated mitochondria have provided new insight into the mechanisms and interventions for ischemia and reperfusion (I/R) injury. In in vitro experiments involving isolated mitochondria, hypoxia and reoxygenation (H/R) has been widely used to mimic I/R injury. However, in in vitro H/R mitochondrial experiments, the effects of various substrates on mitochondrial oxidative phosphorylation are unclear. In the present study, the effects of in vitro I/R injury on mitochondrial oxidative phosphorylation under different substrate conditions were investigated.

METHODS:

Hypoxia was achieved following complete consumption of oxygen by mitochondria isolated from rat heart tissue in an experimental chamber. The H/R protocol involved 30 min hypoxia followed by 15 min reoxygenation in a chamber opened to the atmosphere. Mitochondrial respiration and respiratory control ratio (RCR) were measured.

RESULTS:

When pyruvate/malate were used as substrates, H/R significantly decreased state 3 respiration (28.2±12 nmol O₂/min/mg protein) and RCR (2.7±0.8) compared with the control (121.4±32.5 nmol O₂/mg protein/min and 7.8±1.2, respectively). In contrast, when succinate was used without rotenone, H/R significantly increased state 3 respiration (57.0±11.2 nmol O₂/mg protein/min) and RCR (2.0±0.3) compared with the control (48.2±12.3 nmol O₂/mg protein/min and 1.3±0.2, respectively).

CONCLUSIONS:

The present study demonstrated that mitochondrial oxidative phosphorylation can be modulated by H/R in vitro depending on substrate conditions.     

Oxygen desaturation in healthy subjects undergoing the incremental shuttle walk test

OBJECTIVE:

To determine the probability of oxygen desaturation in healthy individuals undergoing the incremental shuttle walk test (ISWT).

METHODS:

We enrolled 83 healthy subjects: 55 males (including 1 smoker) and 28 females. We determined pre-ISWT FEV₁, FEV₆, HR and SpO₂, as well as post-ISWT HR and SpO₂.

RESULTS:

Mean values overall were as follows: age, 35.05 ± 12.53 years; body mass index, 24.30 ± 3.47 kg/m²; resting HR, 75.12 ± 12.48 bpm; resting SpO₂, 97.96 ± 1.02%; FEV₁, 3.75 ± 0.81 L; FEV₆, 4.45 ± 0.87 L; FEV₁/FEV₆ ratio, 0.83 ± 0.08 (no restriction or obstruction); incremental shuttle walk distance, 958.30 ± 146.32 m; post-ISWT HR, 162.41 ± 18.24 bpm; and post-ISWT SpO₂, 96.27 ± 2.21%. In 11 subjects, post-ISWT SpO₂ was higher than was pre-ISWT SpO₂. In 17 subjects, there was a 4% decrease in SpO₂ after the ISWT. There were no statistically significant differences between the groups with and without post-ISWT oxygen desaturation in terms of age, gender, FEV₁, FEV₆, FEV₁/FEV₆, pre-ISWT SpO₂, incremental shuttle walk distance, HR, or percentage of maximal HR. In the individuals with post-ISWT oxygen desaturation, the body mass index was higher (p = 0.01) and post-ISWT SpO₂ was lower (p = 0.0001).

CONCLUSIONS:

Healthy individuals can present oxygen desaturation after the ISWT. Using the ISWT to predict subtle respiratory abnormalities can be misleading. In healthy subjects, oxygen desaturation is common after the ISWT, as it is during any intense physical activity.