Effects on Lung Gas Volume, Respiratory Mechanics and Gas Exchange of a Closed-Circuit Suctioning System during Volume- and Pressure-Controlled Ventilation in ARDS Patients.

Mechanically ventilated patients periodically require endotracheal suctioning. There are conflicting data regarding the loss of lung gas volume caused by the application of a negative pressure by closed-circuit suctioning. The aim of this study was to evaluate the effects of suctioning performed by a closed-circuit system in ARDS patients during volume- or pressure-controlled ventilation. In this prospective crossover-design study, 18 ARDS patients were ventilated under volume and pressure control applied in random order. Gas exchange, respiratory mechanics and EIT-derived end-expiratory lung volume (EELV) before the suctioning manoeuvre and after 5, 15 and 30 min were recorded. The tidal volume and respiratory rate were similar in both ventilation modes; in volume control, the EELV decreased by 31 ± 23 mL, 5 min after the suctioning, but it remained similar after 15 and 30 min; the oxygenation, PaCO2 and respiratory system elastance did not change. In the pressure control, 5 min after suctioning, EELV decreased by 35 (26-46) mL, the PaO2/FiO2 did not change, while PaCO2 increased by 5 and 30 min after suctioning (45 (40-51) vs. 48 (43-52) and 47 (42-54) mmHg, respectively). Our results suggest minimal clinical advantages when a closed system is used in volume-controlled compared to pressure-controlled ventilation.

The furosemide stress test, electrolyte response and Renal Index in critically ill patients.

BACKGROUND: Acute kidney injury (AKI) is a common syndrome in critically ill patients. The diagnostic ability of traditional markers such as serum creatinine has recently been questioned, and the use of newer tests such as the furosemide stress test or the ultrasound assessment of renal resistive index have been proposed. Aim of the present study was to compare the response to a furosemide stress test, the Renal Index in mechanically ventilated patients with and without acute kidney injury at admission, and who did or did not develop AKI at day three, among those with normal renal function at the CIU admission. METHODS: Prospective observational study in consecutive mechanically ventilated patients admitted in a general intensive care. Furosemide stress test and ultrasonographical Renal Index were performed at the admission and clinical and laboratory data were collected before and two hours after the furosemide stress text. The urine output after the first and the second hours was recorded. RESULTS: Forty patients were enrolled, 19 of whom had AKI at admission. The Renal Index was significantly higher in patients with AKI (0.77±0.07 vs. 0.72±0.08, P=0.027); patients with AKI had a significantly lower urine output after the furosemide stress test (400 [340; 1400] vs.1525 [400; 2550] mL; P=0.013). The plasma concentrations of sodium, potassium and chloride were not different before and after the furosemide stress test in patients with and without AKI, whereas in patients with AKI, the total urine output of sodium, potassium and chloride were significantly lower compared to patients without AKI. Similar results were found in patients without AKI at admission and who developed AKI at day three as compared to those who did not develop AKI. CONCLUSIONS: The response to the furosemide stress test and the Renal Index could be used as additional tools to evaluate the kidney function in critically ill patients.

Hysteresis and Lung Recruitment in Acute Respiratory Distress Syndrome Patients: A CT Scan Study.

OBJECTIVES: Hysteresis of the respiratory system pressure-volume curve is related to alveolar surface forces, lung stress relaxation, and tidal reexpansion/collapse. Hysteresis has been suggested as a means of assessing lung recruitment. The objective of this study was to determine the relationship between hysteresis, mechanical characteristics of the respiratory system, and lung recruitment assessed by a CT scan in mechanically ventilated acute respiratory distress syndrome patients. DESIGN: Prospective observational study. SETTING: General ICU of a university hospital. PATIENTS: Twenty-five consecutive sedated and paralyzed patients with acute respiratory distress syndrome (age 64 ± 15 yr, body mass index 26 ± 6 kg/m, PaO2/FIO2 147 ± 42, and positive end-expiratory pressure 9.3 ± 1.4 cm H2O) were enrolled. INTERVENTIONS: A low-flow inflation and deflation pressure-volume curve (5-45 cm H2O) and a sustained inflation recruitment maneuver (45 cm H2O for 30 s) were performed. A lung CT scan was performed during breath-holding pressure at 5 cm H2O and during the recruitment maneuver at 45 cm H2O. MEASUREMENTS AND MAIN RESULTS: Lung recruitment was computed as the difference in noninflated tissue and in gas volume measured at 5 and at 45 cm H2O. Hysteresis was calculated as the ratio of the area enclosed by the pressure-volume curve and expressed as the hysteresis ratio. Hysteresis was correlated with respiratory system compliance computed at 5 cm H2O and the lung gas volume entering the lung during inflation of the pressure-volume curve (R = 0.749, p < 0.001 and R = 0.851, p < 0.001). The hysteresis ratio was related to both lung tissue and gas recruitment (R = 0.266, p = 0.008, R = 0.357, p = 0.002, respectively). Receiver operating characteristic analysis showed that the optimal cutoff value to predict lung tissue recruitment for the hysteresis ratio was 28% (area under the receiver operating characteristic curve, 0.80; 95% CI, 0.62-0.98), with sensitivity and specificity of 0.75 and 0.77, respectively. CONCLUSIONS: Hysteresis of the respiratory system computed by low-flow pressure-volume curve is related to the anatomical lung characteristics and has an acceptable accuracy to predict lung recruitment.

Body Position Alters Mechanical Power and Respiratory Mechanics During Thoracic Surgery.

BACKGROUND: During thoracic surgery, patients are usually positioned in lateral decubitus and only the dependent lung ventilated. The ventilated lung is thus exposed to the weight of the contralateral hemithorax and restriction of the dependent chest wall. We hypothesized that mechanical power would increase during one-lung ventilation in the lateral position. METHODS: We performed a prospective, observational, single-center study from December 2016 to May 2017. Thirty consecutive patients undergoing general anesthesia with mechanical ventilation (mean age, 68 ± 11 years; body mass index, 25 ± 5 kg·m) for thoracic surgery were enrolled. Total and partitioned mechanical power, lung and chest wall elastance, and esophageal pressure were compared in supine and lateral position with double- and one-lung ventilation and with closed and open chest both before and after surgery. Mixed factorial ANOVA for repeated measurements was performed, with both step and the period before or after surgery as 2 within-subject factors, and left or right body position during surgery as a fixed, between-subject factor. Appropriate interaction terms were included. RESULTS: The mechanical power was higher in lateral one-lung ventilation compared to both supine and lateral position double-lung ventilation (11.1 ± 3.0 vs 8.2 ± 2.7 vs 8.7 ± 2.6; mean difference, 2.9 J·minute [95% CI, 1.4-4.4 J·minute] and 2.4 J·minute [95% CI, 0.9-3.9 J·minute]; P < .001 and P = .002, respectively). Lung elastance was higher during lateral position one-lung ventilation compared to both lateral and supine double-lung ventilation (24.3 ± 8.7 vs 9.5 ± 3.8 vs 10.0 ± 3.8; mean difference, 14.7 cm H2O·L [95% CI, 11.2-18.2 cm H2O·L] and 14.2 cm H2O·L [95% CI, 10.8-17.7 cm H2O·L], respectively) and was higher compared to predicted values (20.1 ± 7.5 cm H2O·L). Chest wall elastance increased in lateral position double-lung ventilation compared to supine (11.1 ± 3.8 vs 6.6 ± 3.4; mean difference, 4.5 cm H2O·L [95% CI, 2.6-6.3 cm H2O·L]) and was lower in lateral position one-lung ventilation with open chest than with a closed chest (3.5 ± 1.9 vs 7.1 ± 2.8; mean difference, 3.6 cm H2O·L [95% CI, 2.4-4.8 cm H2O·L]). The end-expiratory esophageal pressure decreased moving from supine position to lateral position one-lung ventilation while increased with the opening of the chest wall. CONCLUSIONS: Mechanical power and lung elastance are increased in the lateral position with one-lung ventilation. Esophageal pressure monitoring may be used to follow these changes.

Gas exchange, specific lung elastance and mechanical power in the early and persistent ARDS.

PURPOSE: Aim of this study was to evaluate the effect of acute respiratory distress syndrome (ARDS) duration on gas-exchange, respiratory mechanics, specific lung elastance and mechanical power. MATERIALS AND METHODS: In a single center prospective study 28 ARDS patients (66.4 ±â€¯10.0 years, BMI 23.6[21.3-28.8] kg/m2, PaO2/FiO2 148.9[99.6-173.5]) who still presented ARDS criteria after 7-days of mechanical ventilation were studied in early and persistent phase of the disease (day-1 and after 7-days). Each patient underwent PEEP trial at 5-15 cmH2O in both phases. RESULTS: At both PEEP levels the PaO2 was similar in both phases (early: 70.7[65.1-84.4] vs 102.0[85.5-131.8] mmHg; persistent 70.7[63.0-76.2] vs 97.4[86.5-117.1] mmHg, 5-15 cmH2O respectively), the PaCO2 was significantly higher in the persistent phase at both PEEP levels (early 50.6 ±â€¯10.2 vs 52.1 ±â€¯10.5 mmHg; persistent 57.7 ±â€¯13.4 vs 56.9 ±â€¯12.8 mmHg). Specific lung elastance was not different in the early compared to the persistent phase 12.5 ±â€¯3.1 vs 12.2 ±â€¯3.8 cmH2O. The mechanical power normalized for the functional residual capacity increased with PEEP and was similar in both phases (early 23.4[12.8-32.8] vs 34.3[25.3-47.9], persistent 16.3[10.9-24.1] vs 26.7[19.9-46.0] J/min/L, 5-15 cmH2O respectively). CONCLUSIONS: The persistent phase of ARDS for 7-days did not affect the respiratory mechanics while significantly impaired the PaCO2 exchange.

Current Concepts of ARDS: A Narrative Review.

Acute respiratory distress syndrome (ARDS) is characterized by the acute onset of pulmonary edema of non-cardiogenic origin, along with bilateral pulmonary infiltrates and reduction in respiratory system compliance. The hallmark of the syndrome is refractory hypoxemia. Despite its first description dates back in the late 1970s, a new definition has recently been proposed. However, the definition remains based on clinical characteristic. In the present review, the diagnostic workup and the pathophysiology of the syndrome will be presented. Therapeutic approaches to ARDS, including lung protective ventilation, prone positioning, neuromuscular blockade, inhaled vasodilators, corticosteroids and recruitment manoeuvres will be reviewed. We will underline how a holistic framework of respiratory and hemodynamic support should be provided to patients with ARDS, aiming to ensure adequate gas exchange by promoting lung recruitment while minimizing the risk of ventilator-induced lung injury. To do so, lung recruitability should be considered, as well as the avoidance of lung overstress by monitoring transpulmonary pressure or airway driving pressure. In the most severe cases, neuromuscular blockade, prone positioning, and extra-corporeal life support (alone or in combination) should be taken into account.

Actigraphic monitoring in critically ill patients: preliminary results toward an "observation-guided sedation".

PURPOSE: The aim of this study is to evaluate continuous wrist actigraphy (measurement of limb movements) in intensive care unit patients as a neurologic status monitoring. MATERIALS AND METHODS: This is a prospective, observational study on motor activity of adult patients using wrist actigraphs. Nurses recorded the number of sleep and agitation hours as well as assessed pain and anxiety level (verbal numeric rating) and the agitation/sedation level (Richmond Agitation-Sedation Scale). RESULTS: Thirteen mechanically ventilated patients were studied during their whole intensive care unit stay (total, 165 patients/d). The number of surveyed movements was gathered for each hour, obtaining an estimation of patient motor status. This measure was different between days and nights (33.3 [20.3-49.0] vs 8.5 [4.4-13.8]; P < .001), with a correlation with sleeping hours estimated by nurses (P = .017 during the days [D], P < .001 during the nights [N]), agitation hours (P = .002 D, P = .017 N), Richmond Agitation-Sedation Scale value (P < .001 D and N), pain (P = .012 D), and anxiety (P < .001 D) verbal numeric rating. No differences were found using epochs of 15 or 120 seconds. Compliance with patients and nurses was acceptable. CONCLUSIONS: Patients' limb movements were significantly related to all studied neurologic status indexes. Continuous actigraphy measuring may become important as a clinical tool both to guide utilization of sedative drugs and to enhance early recognition and management of agitation.