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PubMed1994

Understanding mechanical ventilation: indications for and initiation of therapy.

The growing complexity of mechanical ventilators and the proliferation of new ventilator modes may confuse and intimidate clinicians who on occasion must manage a mechanical ventilator. The fundamental indications for and types of mechanical ventilation are reviewed, and guidelines for basic ventilator settings are provided. By understanding and applying these essentials, the clinician can provide effective mechanical ventilation to most patients who require it. A subsequent article published in this journal will review the related topics of patient monitoring during mechanical ventilation, complications of mechanical ventilation, and weaning from mechanical ventilation.

Acute Disease↗
PubMedDate not supplied

Flow-synchronized ventilation of preterm infants with respiratory distress syndrome.

Asynchrony of delivered and spontaneous breaths in mechanically ventilated infants may impair gas exchange and prolong the need for assisted ventilation. We conducted a randomized, controlled trial of a patient-triggered, flow-synchronized ventilator on 30 preterm infants with respiratory distress syndrome who weighed between 1100 and 1500 gm at birth. Entry criteria included radiographic evidence of respiratory distress syndrome and the need for mechanical ventilation and surfactant replacement therapy. Patients were assigned to either conventional time-cycled, pressure-limited ventilation or patient-triggered, flow-synchronized ventilation in an assist/control mode. Otherwise clinical management was identical. Time to extubation was the primary outcome measure. Patients treated with flow-synchronized ventilation were weaned more rapidly and had a significantly shorter mean time to extubation than those treated with time-cycled, pressure-limited ventilation, 119 versus 271 hours, p = 0.0152. In addition, there was no difference in the rate of complications between the two groups. There were, however, considerable reductions in patient charges of $4344 per patient in the flow-synchronized ventilation group.

Female↗
PubMed1993

[Certain aspects of continuous ventilation].

The indication of mechanical ventilation is either a failing ventilatory function of the thorax or a failing gas exchange function of the lung. The ventilation affects every organ function in more or less degree. The starting point of long term ventilation is debated, arbitrary. Some ventilatory devices are simulating the natural intrapleural negative pressure principle, but most of them applies intermittent positive pressure into the lung. For improving oxygenation, a moderate level of positive end expiratory pressure, eventually inversed or 1:1 inspiratory:expiratory ratio can be applied. The computerized electronic ventilators offer a big selection of assisting and controlling ventilatory modes, according to the requirements of the patients. For routine use, in ventilatory failure, pressure cycled controlled ventilation, in gas exchange failure, the combination of synchronized intermittent mandatory ventilation, positive end-expiratory pressure and pressure support can be recommended. For special tasks there are existing special ventilatory or other supportive means. In most of the cases some sedation of the ventilated patients is appropriate, muscle paralysing is restricted to a few situations. It is important to humidify the inhaled air. The detailed monitoring of the patients is essential during ventilation. The weaning of the patients from the ventilator is a complex procedure, which involves ventilatory, nutritional, pharmacologic and psychologic interventions.

Blood Gas Monitoring, Transcutaneous↗
PubMed1995

[Mechanical ventilation and long-term respiratory care in the intensive care unit of a general hospital].

We studied the need for mechanical ventilation in 265 patients with respiratory failure who came to our medical ICU over the past 3 years. The time required for weaning from mechanical ventilation and the percentage of patients who needed oxygen therapy or mechanical ventilation at home after their condition was no longer acute were also studied. Of the patients treated in the medical ICU, 143 (54%) required mechanical ventilation; 104 (39%) had acute respiratory failure and the others had acute exacerbations of chronic respiratory failure. Some causes of acute respiratory failure were aspiration pneumonia, bronchial asthma, and drug use. Three-fourths of those with chronic respiratory failure had pulmonary emphysema, sequela of pulmonary tuberculosis, or idiopathic interstitial pneumonia. In patients with chronic respiratory failure, success in weaning could be predicted from the respiratory index (PaO2/FIO2), the serum albumin level, and the length of time that they were ventilated with more than 60% oxygen. Thirteen patients with chronic respiratory failure died while receiving mechanical ventilation. Of those who survived, 11 underwent tracheostomies, and 4 of those 11 were mechanically ventilated at home with portable devices. Ten other survivors received home oxygen therapy. Chest physicians bear the greatest responsibility for managing mechanical ventilation in medical emergencies. Moreover, the prognosis for patients with chronic respiratory failure can be improved with a long-term program for respiratory care that includes home mechanical ventilation and home oxygen therapy.

Adult↗
PubMed1997

Enhancement of Xe-133 ventilation lung scan image acquired after Tc-99m perfusion scan.

In nuclear medicine, the match and mismatch between the images of lung perfusion and ventilation provide an important criterion to diagnose pulmonary embolism. Usually, for imaging clarity, the ventilation scan using 133Xe is performed before the perfusion scan using 99mTc. But the inverse order is preferred clinically, since (i) if the perfusion image is normal, there is no need to do the ventilation scan, and (ii) if the perfusion image is abnormal, the ventilation image can be obtained by focusing on the perfusion abnormalities. However, the quality of the ventilation image is reduced if the ventilation scan is performed after the perfusion scan, because the 140 keV photons emitted from 99mTc will scatter into the acquisition window of 133Xe (81 keV). The purpose of this study is to apply image processing techniques to reduce the scattering effect of 99mTc to get a better 133Xe ventilation image. First, an image sequence in the preferred inverse order is simulated using the images acquired in the normal order. Image processing techniques are used to find an optimized way to reduce the scattering background in the ventilation image. Second, a real image sequence is acquired in the inverse order. An improved ventilation image is then obtained by applying image processing techniques to this image sequence.

Humans↗
PubMed1998

Weaning from artificial ventilation.

Every intubated and mechanically-ventilated patient should be clinically evaluated, at least on a daily basis, by a skilled team in order to speed up the weaning process as much as possible. Again, it should be emphasized that the adoption of an active clinical strategy when faced with "difficult" to wean patients is of paramount importance. In one study, performed in Spain, analysing the prevalence of mechanical ventilation in intensive care units [3], reported the mean number of days that patients spent on mechanical ventilation was 27. In a more recent intervention study, in which a specific protocol was followed each day [2], the mean number of days on mechanical ventilation was only 12. These data have been confirmed by several authors [4, 40], and it has also been reported that a protocol-directed weaning strategy leads not only to a significant reduction in the duration of mechanical ventilation but also to a significant decrease in the number of complications and cost [4]. However, even following a protocol-directed weaning strategy, it is possible that weaning duration can be further reduced. In a prospective study performed in our institution [41] during 32 months, we reported that, following an episode of unplanned extubation, the only independent variables associated with the need for reintubation were the number of days of mechanical ventilation and the type of ventilatory support at the time of autoextubation. Indeed, when patients were in the weaning period only 16% (5 out of 32) needed reintubation, whereas reintubation was needed in 82% (22 out of 27) of patients who had an unplanned extubation during full mechanical ventilatory support. These data suggest that there are still some patients being on mechanical ventilation for a longer than necessary period of time. Finally, very recent advances in technological areas such as artificial intelligence, are proving to be useful in the management of the weaning process. When such systems are applied to modern microprocessor-controlled mechanical ventilators they can significantly help in the process of weaning [42] by automatically reducing the ventilatory assistance and by indicating the optimal time to withdraw the patient from the ventilator and proceed with extubation.

Humans↗
PubMed2001

Feasibility of tidal volume-guided ventilation in newborn infants: a randomized, crossover trial using the volume guarantee modality.

BACKGROUND AND AIM: Volume guarantee (VG) is a new composite mode of pressure-limited ventilation, available on the Dräger Babylog 8000 ventilator, which allows the clinician to set a target mean tidal volume to be delivered while still maintaining control over peak airway pressures. This study aimed to investigate the feasibility and efficacy of this mode of ventilation in premature newborn infants with respiratory distress syndrome (RDS). METHODS: Two groups of infants were studied: those receiving synchronized intermittent positive pressure ventilation (SIPPV) in early phase of RDS (group 1) and those in recovery phase of RDS being weaned from artificial ventilation through synchronized intermittent mandatory ventilation (SIMV; group 2). Both groups of infants were studied over a 4-hour period. Before the start of the study, the infants were either receiving SIPPV (group 1) or SIMV (group 2). Infants in group 1 were randomized to either continue on SIPPV for the first hour of the study or to receive SIPPV plus VG for the first hour. Subsequently, the 2 modes were used alternately for the remaining three 1-hour periods. Similarly, infants in group 2 were randomized to either continue on SIMV for the first hour of the study or to receive SIMV plus VG for the first hour. Data on ventilation parameters and transcutaneous carbon dioxide and oxygen were collected continuously. RESULTS: Forty infants were studied, 20 in each group. The mean (standard error) gestational age was 27.9 (0.3) weeks; birth weight was 1064 (60) g. No adverse events were observed during the study. Fractional inspired oxygen during SIMV plus VG was 0.31 (0.3); during SIMV, 0.31 (0.3); during SIPPV plus VG, 0.41 (0.4); and during SIPPV, 0.40 (0.4). Transcutaneous carbon dioxide pressure during SIMV plus VG was 6.0 (2.2) kPa; during SIMV, 5.9 (2.2) kPa; during SIPPV plus VG, 6.4 (2.9) kPa; and during SIPPV, 6.4 (2.8) kPa. Transcutaneous partial pressure of oxygen during SIMV plus VG was 8.4 (8.7) kPa; during SIMV, 8.6 (8.8) kPa; during SIPPV plus VG, 7.6 (4.0) kPa; and during SIPPV, 7.7 (4.2) kPa. None of these differences was statistically significant. The mean (standard error) peak inspiratory pressure used during SIMV was 17.1 (3.4) cm of water; during SIMV plus VG, 15.0 (7.5) cm of water; during SIPPV plus VG, 17.1 (9.3) cm of water; and during SIPPV, 18.7 (8.3) cm of water. The mean airway pressure during SIMV plus VG was 6.5 (3.1) cm of water; during SIMV, 6.9 (2.8) cm of water; during SIPPV plus VG, 9.6 (4.5) cm of water; and during SIPPV, 9.8 (4.6) cm of water. CONCLUSION: VG seems to be a stable and feasible ventilation mode for neonatal patients and can achieve equivalent gas exchange using statistically significant lower peak airway pressures both during early and recovery stages of RDS.ventilation, airway pressure, volume guarantee, tidal volume.

Birth Weight↗
PubMed2001

Permissive hypercapnia for the prevention of morbidity and mortality in mechanically ventilated newborn infants.

BACKGROUND: Experimental animal data and uncontrolled, observational studies in human infants have suggested that hyperventilation and hypocapnia may be associated with increased pulmonary and neurodevelopmental morbidity. Protective ventilatory strategies allowing higher levels of arterial CO2 (permissive hypercapnia) are now widely used in adult critical care. The aggressive pursuit of normocapnia in ventilated newborn infants may contribute to the already present burden of lung disease. However, the safe or ideal range for PCO2 in this vulnerable population has not been established. OBJECTIVES: To assess whether, in mechanically ventilated neonates, a strategy of permissive hypercapnia improves short and long term outcomes (esp. mortality, duration of respiratory support, incidence of chronic lung disease and neurodevelopmental outcome). SEARCH STRATEGY: Standard strategies of the Cochrane Neonatal Review Group were used. Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, CINAHL, and Current Contents. Searches were also made of previous reviews including cross-referencing, abstracts, and conference and symposia proceedings published in Pediatric Research. SELECTION CRITERIA: All randomised controlled trials in which a strategy of permissive hypercapnia was compared with conventional strategies aimed at achieving normocapnia (or lower levels of hypercapnia) in newborn infants who are mechanically ventilated were eligible. DATA COLLECTION AND ANALYSIS: Standard methods of the Cochrane Neonatal Review Group were used. Trials identified by the search strategy were independently reviewed by each author and assessed for eligibility and trial quality. Data were extracted separately. Differences were compared and resolved. Additional information was requested from trial authors. Only published data were available for review. Results are expressed as relative risk and risk difference for dichotomous outcomes, and weighted mean difference for continuous variables. MAIN RESULTS: Two trials involving 269 newborn infants were included. Meta-analysis of combined data was possible for three outcomes. There was no evidence that permissive hypercapnia reduced the incidence of death or chronic lung disease at 36 weeks (RR 0.94, 95% CI 0.78, 1.15), intraventricular haemorrhage grade 3 or 4 (RR 0.84, 95% CI 0.54, 1.31) or periventricular leukomalacia (RR 1.02, 95% CI 0.49, 2.12). There were no differences in any other reported outcomes when the strategy of permissive hypercapnia/minimal ventilation was compared to routine ventilation in newborn infants. Long term neurodevelopmental outcomes were not reported. One trial reported that permissive hypercapnia reduced the incidence of chronic lung disease in the 501 to 750 gram subgroup. REVIEWER'S CONCLUSIONS: This review does not demonstrate any significant overall benefit of a permissive hypercapnia/minimal ventilation strategy compared to a routine ventilation strategy. At present, therefore, these ventilation strategies cannot be recommended to reduce mortality, or pulmonary and neurodevelopmental morbidity. Ventilatory strategies which target high levels of PCO2 (> 55 mmHg) should only be undertaken in the context of well-designed controlled clinical trials. These trials should aim to establish the safe, or ideal, range for CO2 in ventilated newborns, and examine the role of protective ventilatory techniques in achieving this target.

Bronchopulmonary Dysplasia↗
PubMed2002

Tracheal gas insufflation for the prevention of morbidity and mortality in mechanically ventilated newborn infants.

BACKGROUND: Tracheal gas insufflation (TGI) is a technique where a continuous flow of gas is instilled into the lower trachea during conventional mechanical ventilation. TGI can improve carbon dioxide removal with lower ventilation pressures and smaller tidal volumes, potentially decreasing secondary lung injury and chronic lung disease (CLD). OBJECTIVES: To assess whether, in mechanically ventilated neonates, the use of tracheal gas insufflation reduces mortality, CLD and other adverse clinical outcomes without significant side effects. SEARCH STRATEGY: Searches were made of MEDLINE 1966 to December 2001, CINAHL 1982 to December 2001, the Cochrane Controlled Trials Register (Cochrane Library, Issue 4, 2001) and conference and symposia proceedings. SELECTION CRITERIA: Randomised controlled trials (RCT) that include newborn infants who are mechanically ventilated, and compare TGI during conventional mechanical ventilation (CMV) with CMV alone. Primary outcomes - mortality, CLD and neurodevelopmental outcome; secondary outcomes - air leak, intraventricular haemorrhage, periventricular leukomalacia, duration of mechanical ventilation, duration of respiratory support, duration of oxygen therapy, duration of hospital stay, retinopathy of prematurity, immediate adverse effects. DATA COLLECTION AND ANALYSIS: Each reviewer assessed eligibility, trial quality and extracted data separately. Study authors were contacted for additional information if necessary. MAIN RESULTS: Only one small study was found to be eligible. This study found no evidence of effect on mortality, CLD or age at first extubation. The total duration of ventilation was 9.3 days shorter in the TGI group (95% CI from 15.7 to 2.9 days shorter). The age at complete weaning from ventilation was 26 days shorter in the TGI group (95% CI from 46 to 6 days shorter). There was no evidence of effect on the total duration of respiratory support, oxygen therapy or hospital stay. REVIEWER'S CONCLUSIONS: There is evidence from a single RCT that TGI may reduce the duration of mechanical ventilation in preterm infants - although the data from this small study do not give sufficient evidence to support the introduction of TGI into clinical practice. The technical requirements for performing TGI (as performed in the single included study) are great. There is no statistically significant reduction in the total duration of respiratory support or hospital stay. TGI cannot be recommended for general use at this time.

Humans↗
PubMed2004

Prophylactic antibiotics to reduce morbidity and mortality in ventilated newborn infants.

BACKGROUND: Bacterial colonisation of the respiratory tract is associated with intubation and may increase the risk of acquiring infection. This may prolong the need for mechanical ventilation and increase the risk of chronic lung disease. The use of prophylactic antibiotics has been advocated for all mechanically ventilated newborns in order to reduce the risk of colonisation and acquired infection. Countering this is the possibility that harm may outweigh benefit. OBJECTIVES: To assess the effects of prophylactic antibiotics in reducing mortality and morbidity in intubated and ventilated newborn infants who are not known to have infection. In separate comparisons, we reviewed two different policies regarding the prophylactic use of antibiotics in intubated, ventilated infants: 1) among babies who are being intubated for mechanical ventilation, a policy of prophylactic antibiotics for the duration of intubation versus placebo or no treatment. 2) among intubated, ventilated babies who had been started on antibiotics at the time of intubation but whose initial cultures to rule our sepsis are negative, a policy of continuing versus discontinuing prophylactic antibiotics. SEARCH STRATEGY: We searched MEDLINE (January 1966 to May 2003), CINAHL (1982 to May 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2003), the Cochrane Neonatal Group Specialised Register and reference lists of articles. SELECTION CRITERIA: Randomised controlled trials of sufficient quality in which mechanically ventilated newborn infants are randomised to receive prophylactic antibiotics versus placebo or no treatment. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality. MAIN RESULTS: One study, of insufficient quality, met the criteria for inclusion in this review. REVIEWER'S CONCLUSIONS: There is no evidence from randomised trials to support or refute the use of prophylactic antibiotics when commencing mechanical ventilation in newborn infants, or to support or refute continuing antibiotics once initial cultures rule out infection in mechanically ventilated newborn infants.

Antibiotic Prophylaxis↗
PubMed2001

Hyperpolarized 3He MR lung ventilation imaging in asthmatics: preliminary findings.

Asthma is a disease characterized by chronic inflammation and reversible obstruction of the small airways resulting in impaired pulmonary ventilation. Hyperpolarized 3He magnetic resonance (MR) lung imaging is a new technology that provides a detailed image of lung ventilation. Hyperpolarized 3He lung imaging was performed in 10 asthmatics and 10 healthy subjects. Seven asthmatics had ventilation defects distributed throughout the lungs compared with none of the normal subjects. These ventilation defects were more numerous and larger in the two symptomatic asthmatics who had abnormal spirometry. Ventilation defects studied over time demonstrated no change in appearance over 30-60 minutes. One asthmatic subject was studied twice in a three-week period and had ventilation defects which resolved and appeared in that time. This same subject was studied before and after bronchodilator therapy, and all ventilation defects resolved after therapy. Hyperpolarized 3He lung imaging can detect the small, reversible ventilation defects that characterize asthma. The ability to visualize lung ventilation offers a direct method of assessing asthmatics and their response to therapy.

Adult↗
PubMed2001

Quantitative analysis of end-tidal carbon dioxide during mechanical and spontaneous ventilation in infants and young children.

Capnography provides a substitute for monitoring of arterial carbon dioxide tension (PCO(2)). We performed a prospective study to evaluate a new application of capnography, using quantitative curve analysis in the pediatric ICU. Twenty-five infants and children admitted to the pediatric ICU after cardiovascular surgery for congenital heart diseases were included in the study. Capnographic curves were recorded during 3 phases of mechanical and spontaneous ventilation: phase 1, immediate postoperative period; phase 3, preextubation period; and phase 2, period between phases 1 and 3. Each recording included 17 sec of capnographic tracings from consecutive spontaneous and/or ventilator-driven breaths. Quantitative curve analysis was made to define parameters including peak value of exhaled PCO(2) (P), mean rate of rise of PCO(2) (R), and area under each capnographic curve (A). Qualitative inspection of the wave contour showed no obvious difference in phase 3 during spontaneous and mechanically assisted ventilator breaths. However, an obvious difference existed between spontaneous and mechanically assisted breaths in phase 2. For each parameter (P, R, and A), there was a significant difference in phases 2 and 3 from spontaneous breaths. However, there was no significant difference in phases 2 and 3 from ventilator-assisted breaths. We further calculated the ratio of parameters of spontaneous breaths (S) and ventilator-assisted breaths (V) in phase 2 and phase 3. The ratio of S/V for P, R, and A showed significant differences between phase 2 and phase 3. We conclude that quantitative analysis of exhaled end-tidal PCO(2) curves revealed significant changes of specific parameters during the transition from the ventilator-dependent state to the spontaneously breathing ventilator-independent state. This new approach provides a new way to estimate respiratory status in infants and children receiving ventilator therapy. Through quantitative capnographic curve analysis, if P, R, and A from spontaneous breaths approached those of ventilator-assisted breaths, patients have resumed reasonable pulmonary mechanics, and extubation may then be considered.

Capnography↗
PubMed1993

Chest wall motion before and during mechanical ventilation in children with neuromuscular disease.

Patients with neuromuscular disease can display paradoxic motion of the rib cage (RC) and abdomen (AB), which increases the work of breathing and predisposes to respiratory muscle fatigue. Long-term mechanical ventilation can reverse chronic hypercapnea and decrease the work of breathing in these patients. Changes in chest wall motion (CWM) that occur during mechanical ventilation have not been studied. We have assessed CWM using a calibrated respiratory inductive plethysmograph before and during mechanical ventilation in 5 children and young adults with neuromuscular disease and paradoxic breathing at rest. Asynchrony of CWM was quantitated by measuring the phase shift, theta, between RC and AB motion (0 degree = synchronous motion, 180 degrees = paradoxic motion). The volume contribution of the paradoxing compartment to tidal volume (PC/VT) was calculated. Before mechanical ventilation, mean +/- SEM VT was 122 +/- 17 mL, theta was 131 +/- 15 degrees C, and PC/VT was -27 +/- 6%. During mechanical ventilation, VT increased to 274 +/- 47 mL (P < 0.05), theta decreased to 41 +/- 14 degrees (P < 0.05), and PC/VT increased to +39 +/- 9% (P < 0.02). We conclude that mechanical ventilation improves RC/AB asynchrony and reverses the negative contribution to tidal volume of the paradoxing compartment in children and young adults with neuromuscular disease. This implies that mechanical ventilation assumes most or all the role of the respiratory pump in these patients, which provides a rationale for the use of chronic or nighttime ventilation in the treatment of respiratory muscle fatigue. Assessment of CWM may be useful in the determination of optimal ventilator settings in this population.

Abdomen↗
PubMed1993

The effects of bedside pulmonary mechanics testing during infant mechanical ventilation: a retrospective analysis.

We examined the effects of regular bedside testing of pulmonary mechanics (PM) on the outcome of 468 acutely ill, mechanically ventilated neonates. During the first of two 18-month study periods, 217 infants were mechanically ventilated without the assistance of PM measurements. During the second 18-month period, 251 infants were ventilated with the assistance of at least daily PM measurements. Using data obtained from the PM tests, we adjusted the infants' ventilators to maintain tidal volume, inspiratory time, and pressure-volume loops within predetermined limits. With the exception of the PM measurements, given the limitations of retrospective analyses, both groups of infants received identical medical and nursing care. The infants ventilated with the assistance of PM testing developed fewer pneumothoraces (4.0%; 10/251) vs. no PM testing, 10.1% (22/217); P < 0.05 by Chi-square analysis]. Infants weighing less than 1,500 g ventilated with the assistance of PM measurements had less intraventricular hemorrhage (IVH) overall, most notably, less grades I and II IVH (total IVH-PM testing, 39.1% vs. no PM testing, 65.7%; P < 0.01; Grades I-II IVH-PM testing, 30.4% vs. no PM testing, 54.9%; P < 0.01). IVH incidence was decreased independent of pneumothorax occurrence. Survival rates, incidences of bronchopulmonary dysplasia, and durations of mechanical ventilation and hospitalization were similar. This retrospective analysis suggests that PM testing during infant mechanical ventilation reduces common acute ventilator-associated complications.

Bronchopulmonary Dysplasia↗
PubMed1988

Neural control of ventilation in the shore crab, Carcinus maenas. II. Frequency-modulating interneurons.

1. We have identified a class of nonspiking interneurons which can control the frequency of ventilation in a graded manner. These frequency modulating interneurons (FMis) also receive synaptic inputs in-phase with the ventilatory motor output providing a functional positive feedback loop in the ventilatory system. The class of FMis is composed of three morphologically and physiologically distinct interneurons, FMi1, FMi2 and FMi3. 2. Depolarization of FMi1 increases the rate of ventilation, while hyperpolarization decreases the rate (Fig. 1). This control is restricted to a single ventilatory central pattern generator (CPG), (Fig. 2), although FMi1 sends processes into the neuropils of both hemiganglionic CPGs (Fig. 3). 3. Hyperpolarization of FMi2 increases the rate of both ventilatory CPGs while depolarization of this cell slows and eventually arrests the rhythm (Figs. 5 and 6). FMi2 receives a synaptic input correlated with the motor output of each of the ventilatory CPGs (Fig. 4). During periods of reversed ventilation, this cell is abruptly hyperpolarized and continues to be driven in-phase with the ventilatory motor output (Fig. 7). 4. Hyperpolarization of FMi3 increases the rate of ventilation and depolarization decreases the rate of ventilation produced by both CPGs (Fig. 10). This control of the ventilatory rate by FMi3 is graded (Fig. 11). There is no apparent change in the membrane potential of FMi3 during reversed ventilation and it is morphologically distinct from FMi2. 5. FMi2 and FMi3 may be involved in the switch in ventilatory motor pattern from forward to reversed ventilation. Hyperpolarization of FMi2 and depolarization of FMi3 can elicit bouts of reversed ventilation from both CPGs (Fig. 13). 6. These results suggest that the FM interneurons act in parallel to control the frequency of ventilation and may act as integrating elements between spiking 'command' fibers in the circumesophageal connectives and the nonspiking interneurons of the ventilatory CPG.

Animals↗
PubMed1998

Clinical and epidemiological findings in mechanically-ventilated patients with methicillin-resistant Staphylococcus aureus pneumonia.

Over the 5-year period from 1990 to 1994, a prospective cohort study was conducted to define the clinical and epidemiological characteristics of ventilator-associated methicillin-resistant Staphylococcus aureus (MRSA) pneumonia acquired during a large-scale outbreak of MRSA infection. Of 2411 mechanically ventilated patients, 347 (14.4%) acquired MRSA, 220 (63.4%) had MRSA positive respiratory tract samples and 41 (18.6%) developed ventilator-associated MRSA pneumonia. The overall attack rate for ventilator-associated MRSA pneumonia was 1.56 episodes/1000 ventilator days, but annual attack rates varied according to the trend of the outbreak (range 4.9-0.2). In comparison with methicillin-sensitive Staphylococcus aureus (MSSA), which was implicated in 98 episodes of ventilator-associated pneumonia, MRSA caused exclusively late-onset ventilator-associated pneumonia, while MSSA caused both early-onset [55 of 98 (56.1%) episodes] and late-onset [43 of 98 (43.8%) episodes] ventilator-associated pneumonia. Logistic regression analysis of all patients with Staphylococcus aureus pneumonia revealed intubation for more than 3 days (odds ratio (OR),1.11; confidence interval (CI):1.03-1.18) and prior bronchoscopy (OR,5.8; CI,1.85-18.19) to be independent variables associated with MRSA pneumonia. The results indicate that MRSA ventilator-associated pneumonia is a frequent complication in intensive care patients, manifesting itself as late-onset pneumonia in patients who have been intubated for prolonged periods and/or have often undergoing previous bronchoscopy.

Adult↗
PubMed2001

Translaryngeal open ventilation to treat acute respiratory failure in acute exacerbation of chronic obstructive pulmonary disease. A preliminary report.

PURPOSE: To describe a minimally invasive alternative to conventional mechanical ventilation, using a small size uncuffed nasotracheal tube (translaryngeal open ventilation) paired with pressure control ventilation, in acute respiratory failure complicating chronic obstructive pulmonary disease (COPD). CLINICAL FEATURES: Two cooperative COPD patients, who failed noninvasive mechanical ventilation, were intubated nasotracheally. Mechanical ventilation was initiated in pressure control mode via an uncuffed 6 mm tube. RESULTS: Respiratory rate improved after 1 hour (from 44 to 28 breaths*min(-1) in case 1 and from 32 to 25 breaths*min(-1) in case 2); PaC0(2) decreased (from 120 to 62 mmHg in case 1 and from 69 to 51 mmHg in case 2); with pressure control mode levels of 45 cm H(2)O and 55 cm H(2)O respectively. PaO(2) increased from 40 mmHg (with FIO(2) 0.3) to 55 mmHg (with FIO(2) 0.3) in the first patient and from 55 mmHg (with FIO(2) 0.4) to 60 mmHg (with FIO(2) 0.4 ) in the second patient; pH improved from 7.18 to 7.31 in case 1 and from 7.22 to 7.39 in case 2. Patients were able to trigger the ventilator, speak, swallow and to clear secretions spontaneously. Both patients were ventilated for three days in this manner without any adverse effects. Both survived and were discharged home after 20 and 18 days in hospital respectively. CONCLUSION: This very preliminary report suggests that, in carefully selected patients who fail mask ventilation, mechanical support with translaryngeal open ventilation can improve gas exchange, breathing pattern and tachypnea, without hindering glottic function.

Acute Disease↗
PubMed2003

Prevention and treatment of gastrointestinal complications in patients on mechanical ventilation.

There exists a complex, dynamic interaction between mechanical ventilation and the splanchnic vasculature that contributes to a myriad of gastrointestinal tract complications that arise during critical illness. Positive pressure-induced splanchnic hypoperfusion appears to play a pivotal role in the pathogenesis of these complications, the most prevalent of which are stress-related mucosal damage, gastrointestinal hypomotility and diarrhea. Furthermore, characteristics of the splanchnic vasculature make the gastrointestinal tract vulnerable to adverse effects related to positive pressure ventilation. While most of these complications seen in mechanically ventilated patients are reflections of altered gastrointestinal physiology, some may be attributed to medical interventions instituted to treat critical illness. Since maintenance of normal hemodynamics cannot always be achieved, pharmacologic prophylactic therapy has become a mainstay in the prevention of gastrointestinal complications in the intensive care unit. Improved understanding of the systemic effects of mechanical ventilation and greater application of lung-protective ventilatory strategies may potentially minimize positive pressure-induced reductions in splanchnic perfusion, systemic cytokine release and, consequently, reduce the incidence of gastrointestinal complications associated with mechanical ventilation. Herein, we discuss the pathophysiology of gastrointestinal complications associated with mechanical ventilation, summarize the most prevalent complications and focus on preventive strategies and available treatment options for these complications. The most common causes of gastrointestinal hemorrhage in mechanically ventilated patients are bleeding from stress-related mucosal damage and erosive esophagitis. In general, histamine H(2) receptor antagonists and proton pump inhibitors prevent stress-related mucosal disease by raising the gastric fluid pH. Proton pump inhibitors tend to provide more consistent pH control than histamine H(2) receptor antagonists. There is no consensus on the drug of choice for stress ulcer prophylaxis with several meta-analyses providing conflicting results on the superiority of any medication. Prevention of erosive esophagitis include careful use of nasogastric tubes and institution of strategies that improve gastric emptying. Many mechanically ventilated patients have gastrointestinal hypomotility and diarrhea. Treatment options for gastrointestinal motility are limited, thus, preventive measures such as correction of electrolyte abnormalities and avoidance of medications that impair gastrointestinal motility are crucial. Treatment of diarrhea depends on the underlying cause. When associated with Clostridium difficile infection antibacterial therapy should be discontinued, if possible, and treatment with oral metronidazole should be initiated.More studies are warranted to better understand the systemic effects of mechanical ventilation on the gastrointestinal tract and to investigate the impact of lung protective ventilatory strategies on gastrointestinal complications.

Gastrointestinal Diseases↗