Conventional Modes Of Mechanical Ventilation Research Articles

Effects of Neurally Adjusted Ventilation Assist (NAVA) and conventional modes of mechanical ventilation on diaphragm functions: A randomized controlled trial

BackgroundBetter patient-ventilator interactions, during neurally adjusted ventilator assist (NAVA), are expected to result in lower rate of diaphragm dysfunction. ObjectiveThis study was planned to compare the rate of diaphragm dysfunction between the conventional modes of mechanical ventilation and NAVA. MethodsPatients who were initiated on mechanical ventilation for acute respiratory failure were randomized to continue either conventional mode of mechanical ventilation or switched to NAVA. The rates of diaphragm dysfunction were compared between two groups. ResultsThis study included 46 participants (male 30/46) with a mean age of 58 years. Mean APACHE II and SOFA scores were 15 and 3, respectively. The mean (SD) diaphragm thickness fraction in the conventional mechanical ventilation and NAVA group were 37.12% (18.48) and 39.27% (27.65), respectively. The diaphragm dysfunction was observed in 5 (22.7%) and 8 (34.7%) patients in NAVA and conventional arm, respectively. There was no statistically significant difference between the two groups (p-value = 0.37). Diaphragm excursion was better in the NAVA group as compared with the conventional mechanical ventilation group. Diaphragm thickness and thickness fraction were comparable between two groups. ConclusionSwitching from the conventional mode of mechanical ventilation to NAVA leads to statistically non-significant reduction in the occurrence of diaphragm dysfunction. Adequately powered studies are required to assess the exact role of NAVA on diaphragm functions.

Utilization of Neurally Adjusted Ventilatory Assist (NAVA) Mode in Infants and Children Undergoing Congenital Heart Surgery: A Retrospective Review.

We assessed the feasibility and the impact of NAVA compared to conventional modes of mechanical ventilation in ventilatory and gas exchange parameters in post-operative children with congenital heart disease. Infants and children (age < 18years) that underwent congenital heart surgery were enrolled. Patients were ventilated with conventional synchronized intermittent mechanical ventilation (SIMV) and subsequently transitioned to NAVA during their cardiovascular intensive care unit (CVICU) stay. The ventilatory and gas exchange parameters for the 24h pre- and post-transition to NAVA were compared. Additional parameters assessed included pain scores and sedation requirements. Eighty-one patients met inclusion criteria with a median age of 21days (interquartile range 13days-2months). The majority of patients enrolled (75.3%) had complex congenital heart disease with high surgical severity scores. The transition to NAVA was tolerated by all patients without complications. The mean peak inspiratory pressure (PIP) was 1.8cm H2O lower (p < 0.001) and mean airway pressure (Paw) was 0.5cm H2O lower (p = 0.009) on NAVA compared to conventional modes of mechanical ventilation. There was no significant difference in patients' respiratory rate, tidal volume, arterial pH, pCO2, and lactate levels between the two modes of ventilation. There was a decreased sedation requirement during the time of NAVA ventilation. Comfort scores did not differ significantly with ventilator mode change. We concluded that NAVA is safe and well-tolerated mode of mechanical ventilation for our cohort of patients after congenital heart surgery. Compared to conventional ventilation there was a statistically significant decrease in PIP and Paw on NAVA.

Severe Hypercapnia in Critically Ill Adult Cystic Fibrosis Patients

BackgroundCystic fibrosis (CF) is a monogenetic autosomal recessive multi-organ disease affecting approximately 50,000 patients worldwide. Overall median survival is continually increasing but pulmonary disease remains the most common cause of death. Guidelines have been published in relation to the outpatient maintenance of lung health for CF patients and treatment of acute lung exacerbations but little information exists about the management of the critically ill CF patient. Invasive mechanical ventilation in CF patients with acute respiratory failure is associated with poor outcome and high mortality.MethodsRetrospective analysis of adult patients with CF who required endotracheal intubation and invasive mechanical ventilation in the Medical Intensive Care Unit (MICU).ResultsBetween the years 2003 - 2009, 14 adult patients with CF required endotracheal intubation and invasive mechanical ventilation in the Medical Intensive Care Unit (MICU) of the Penn State Milton S. Hershey Medical Center, Hershey, Pennsylvania, USA. Eleven patients died in the MICU because of progressive respiratory failure and inability to liberate from mechanical ventilation. Seven individuals consistently manifested arterial partial pressures of carbon dioxide (PaCO2) greater than 20.00 kPa despite high levels of conventional modes of mechanical ventilation.ConclusionIntubated CF patients with respiratory failure have a high mortality rate. Based on our experience, multiple factors contribute to severe hypercapnia and the effectiveness of conventional modes of mechanical ventilation in many of these patients is limited.KeywordsCystic fibrosis; Mechanical ventilation; Critical care; Hypercapnia; Respiratory failure

Ventilator management for hypoxemic respiratory failure attributable to H1N1 novel swine origin influenza virus

Novel H1N1 swine origin influenza virus has led to a worldwide pandemic. During the pandemic, a significant number of patients became critically ill primarily because of respiratory failure. Most of these patients required intubation and mechanical ventilation and were treated with conventional modes of mechanical ventilation using a lung-protective strategy with low tidal volumes, plateau pressures <30 to 35 cm H2O, and optimal positive end-expiratory pressure. In some patients with persistent hypoxemia, alternative modes of ventilation, such as high-frequency oscillatory ventilation and airway pressure release ventilation, were used. We review the ventilatory management, recruitment maneuvers, prone positioning, and goals of ventilatory therapy for hypoxemic respiratory failure in general, as well as lessons learned in the management of H1N1-related respiratory failure.

High-frequency oscillatory ventilation for acute respiratory distress syndrome

To evaluate the effectiveness of HFOV in pediatric patients with acute respiratory distress syndrome. In this retrospective study, we reviewed all 20 pediatric patients, who were consecutively ventilated with HFOV in the pediatric intensive care unit of a tertiary medical center, from January 2006 to February 2007. A total of 20 patients were enrolled. The median age of the subjects was 70 (3-168) months; 10 were male. All patients received conventional ventilation before HFOV. After initiation of HFOV, there was an immediate and sustained increase in PaO(2)/FiO(2) ratio. The PaO(2)/FiO(2) ratio was elevated and OI was decreased significantly after 10-20 minutes and maintained for at least 48 hours (p= 0.03, both). Thirteen of the 20 patients were successfully weaned. No significant change in the mean arterial pressure and heart rate was noted after HFOV. Overall survival rate was 65%. Of 20 patients, 11 patients suffered from extrapulmonary ARDS (ARDSexp) and 9 from pulmonary ARDS (ARDSp). When HFOV was initiated, there was significant increase in PaO(2)/FiO(2) and decrease in OI in ARDSexp compared to ARDSp (p= 0.03, both). Also mortality rate was significantly lower in patients with ARDSexp (9% vs.66%), (p= 0.01). In our study, HFOV was effective in oxygenation and seems to be safe for pediatric ARDS patients. HFOV affected ARDSp and ARDSexp paediatric patients differently. However prospective, randomized controlled trials are needed to identify its benefits over conventional modes of mechanical ventilation.

Alternative Invasive Positive Pressure Ventilatory Strategies

In Brief Conventional modes of mechanical ventilation often cause patient-ventilatory asynchrony and may fail to assure adequate gas exchange while attempting to adhere to lung protective ventilatory strategies. Airway pressure release ventilation, partial liquid ventilation, and high-frequency ventilation are alternative ventilatory strategies used for acute respiratory distress syndrome that aim to protect the lung while providing adequate gas exchange. The closed-loop ventilatory strategies use computer algorithm and feedback monitoring of respiratory system mechanics to improve patient-ventilator interaction and comfort. A vast array of mechanical ventilatory modes is available at the disposal of the clinician. In this article, we discuss the basic principles and review the available clinical evidence for the common alternative invasive ventilatory modes and closed loop ventilatory systems.

Modulation and treatment of patient–ventilator dyssynchrony

The coupling between ventilator delivered inspiratory flow and patient's demands both in terms of timing and drive is a challenging task that has become largely feasible in recent years. This review addresses the new advances to modulate and treat patient-ventilator dyssynchrony. Patient-ventilator dyssynchrony is a common phenomenon with conventional modes of mechanical ventilation which influence the duration of mechanical ventilation. Inspection of pressure, volume and flow waveforms represents a valuable tool for the physician to recognize and take the appropriate action to improve patient-ventilator synchrony. New developments have been introduced aiming to improve patient ventilator synchrony by modulating the triggering function and the variables that control the flow delivery and the cycling off. Patient-ventilator dyssynchrony may affect patients' outcome. New modes of assisted mechanical ventilation have been introduced and represent a major step forward in modulating patient-ventilator dyssynchrony.

High-Frequency Oscillatory Ventilation in Term and Near-Term Infants with Acute Respiratory Failure: Early Rescue Use

This study describes a high-frequency oscillatory ventilation (HFOV) protocol for term and near-term infants with acute respiratory failure (ARF) and reports results of its prospective application. Neonates, with gestational age >or= 34 weeks, were managed with HFOV, if required, on conventional ventilation (CV), a fraction of inspired oxygen (F IO(2)) 0.5, and a mean airway pressure > 10 cm H (2)O to maintain adequate oxygenation or a peak inspiratory pressure > 24 cm H (2)O to maintain tidal volume between 5 and 7 mL/kg of body weight. Seventy-seven infants (gestational age, 37 +/- 2,3 weeks), received HFOV after a mean duration of CV of 7.5 +/- 9.7 hours. Arterial blood gases, oxygenation index (OI), and alveolar-arterial difference in partial pressure of oxygen (P AO(2) - Pa O(2)) were recorded prospectively before and during HFOV. There were a rapid and sustained decreases in mean airway pressure (MAP), F IO(2), OI, and P AO(2) - Pa O(2) during HFOV ( P <or= 0.01). Seventy infants (91%) were weaned successfully from HFOV. Seven infants (P AO(2) - Pa O(2) prior to HFOV, 601 +/- 89 mm Hg) were classified as having experienced treatment failure and died from their underlying disease. Treatment failure was associated with lack of improvement in P AO(2) - Pa O(2) at 1 hour of HFOV ( P < 0.01). Early rescue intervention with HFOV is an effective protocol for term and near-term infants with ARF. Failure to improve P AO(2) - Pa O(2) rapidly on HFOV is associated with HFOV failure. Randomized controlled trials are needed to identify benefits of HFOV versus conventional modes of mechanical ventilation.

High-frequency oscillatory ventilation in pediatric patients with acute respiratory failure

To evaluate the effectiveness of high-frequency oscillatory ventilation (HFOV) in pediatric patients with acute respiratory failure, failing conventional ventilation. A prospective, clinical study. Tertiary care pediatric intensive care unit. Twenty pediatric patients (ages 12 days to 5 yrs) with acute respiratory failure (pneumonia, 14; sepsis with acute respiratory distress syndrome, 3; pulmonary edema as a complication of upper airway obstruction, 2; salicylate intoxication with acute respiratory distress syndrome, 1), failing conventional ventilation (median alveolar-arterial oxygen difference [P(A-a)O2] 578 [489-624] torr, median oxygenation index 26 [21-32]. HFOV was instituted after a median length of conventional ventilation of 15.5 (3.3-43.5) hrs. Ventilator settings, arterial blood gases, oxygenation index, and P(A-a)O2 were recorded before HFOV (0 hrs) and at predetermined intervals during HFOV and compared using the one-way Friedman rank-sum procedure and a two-tailed Wilcoxon matched-pairs test. Initiation of HFOV caused a significant decrease in FiO2 at 1 hr that continued to 24 hrs (p <or= .04). In all patients, target ventilation was achieved, and 19 had improved oxygenation. After 1 hr, PaCO2 significantly decreased (p = .002) and remained within the target range thereafter. There were significant decreases in P(A-a)O2 and oxygenation index at 1 and 4 hrs, respectively, that were sustained up to 12 hrs (p <or= .04). No significant complications associated with HFOV were detected. Fifteen patients (75%) survived to hospital discharge. Only one patient died from respiratory failure. In pediatric patients with acute respiratory failure, failing conventional ventilation, HFOV improves gas exchange in a rapid and sustained fashion. However, randomized controlled trials are needed to identify its benefits over conventional modes of mechanical ventilation.

Ventilación de alta frecuencia

In the era of lung-protective ventilation strategies, high frequency oscillatory ventilation (HFOV) has attracted renewed interest and its use has dramatically increased in neonatal and pediatric intensive care units. HFOV is able to reduce ventilator-induced lung injury by limiting the incidence of volutrauma, atelectrauma, barotrauma and biotrauma. During HFOV, adequate oxygenation and ventilation is achieved by using low tidal volumes and small pressure swings at supraphysiologic frequencies. Unlike other high-frequency ventilation modes, HFOV has an active expiration phase. HFOV constitutes a safe and successful ventilation mode for managing pediatric patients with respiratory insufficiency refractory to optimized conventional mechanical ventilation and provides better results when initiated early. However, the elective use of HFOV requires further studies to identify its benefits over conventional modes of mechanical ventilation and to support its routine use as a first line therapy. In the present article, the Respiratory Working Group of the Spanish Society Pediatric Critical Care reviews the main issues in the pediatric application of HFOV. In addition, a general practical protocol and specific management strategies, as well as the monitoring, patient care and other special features of the use of HFOV in the pediatric setting, are discussed.

Conventional modes of mechanical ventilation.

The conventional modes of mechanical ventilation are volume-preset techniques that offer full or partial ventilatory support to the patient with respiratory insufficiency. The mode of ventilation is the aggregate of the mechanisms for initiation, limitation, and cycling of the ventilator. An understanding of the function of the ventilator during the phases of the respiratory cycle helps the clinician to choose the most appropriate mode of ventilation for the patient.

The aetiology, consequences and prevention of barotrauma: a critical review of the literature

To review critically the literature on pulmonary barotrauma in mechanically ventilated patients. Data sources included MEDLINE and citation lists of relevant articles. Articles investigating the aetiology or prevention of pulmonary barotrauma were critically evaluated according to published guidelines. Experimental animal studies and observational clinical studies consistently demonstrate that the high airway pressures and large tidal volumes associated with conventional modes of mechanical ventilation are major contributors to lung injury. Animal studies establish the correct temporal relationship and demonstrate a biological gradient. Observational clinical studies demonstrate an increased risk of barotrauma in the setting of acute lung injury. The results of three case series and two small randomised clinical trials indicate that a pressure-limited ventilation strategy aimed to reduce barotrauma may improve outcomes in patients with acute lung injury. Pulmonary barotrauma is a clinically important phenomenon that may delay the healing of injured lungs and lead to the development, or the exacerbation, of ARDS. Risk factors for barotrauma include high peak airway pressures, large tidal volumes and acute lung injury. Resolution of the role for pressure-limited ventilation in ARDS prevention and treatment requires a large-scale randomised clinical trial.

Peritoneal Ventilation: An Animal Model of Extrapulmonary Ventilation in Experimental Adult Respiratory Distress Syndrome

Adult respiratory distress syndrome (ARDS) is a critical medical problem in which severe arterial hypoxemia is often poorly responsive to conventional modes of mechanical ventilation. We studied the efficiency of mechanical ventilation of the peritoneal cavity in rabbits with experimental ARDS caused by lung lavage. The study shows that peritoneal ventilation is significantly effective in oxygenation of hypoxemic animals with ARDS and is also effective for carbon dioxide elimination. Peritoneal ventilation may be considered as an investigational method for extrapulmonary oxygenation in severe intractable hypoxemia caused by ARDS.