Prevalence of long-term mechanical insufflation-exsufflation in children with neurological conditions: a population-based study.

AIM: To determine the prevalence of long-term mechanical insufflation-exsufflation (MI-E) and concomitant mechanical ventilation in children with neurological conditions, with reported reasons behind the initiation of treatment. METHOD: This was a population-based, cross-sectional study using Norwegian national registries and a questionnaire. RESULTS: In total, 114 of 19 264 children with a neurological condition had an MI-E device. Seventy-three of 103 eligible children (31 females, 42 males), median (min-max) age of 10 years 1 month (1y 5mo-17y 10mo), reported their MI-E treatment initiation. Overall, 76% reported airway clearance as the main reason to start long-term MI-E. A prophylactic use was mainly reported by children with neuromuscular disorders (NMDs). Prevalence and age at initiation differed by diagnosis. In spinal muscular atrophy and muscular dystrophies, MI-E use was reported in 34% and 7% of children, of whom 83% and 57% respectively received ventilator support. One-third of the MI-E users were children with central nervous system (CNS) conditions, such as cerebral palsy and degenerative disorders, and ventilator support was provided in 31%. The overall use of concomitant ventilatory support among the long-term MI-E users was 56%. INTERPRETATION: The prevalence of MI-E in a neuropaediatric population was 6 per 1000, with two-thirds having NMDs and one-third having conditions of the CNS. The decision to initiate MI-E in children with neurological conditions relies on clinical judgment. WHAT THIS PAPER ADDS: The prevalence and age at initiation of mechanical insufflation/exsufflation (MI-E) differed between diagnoses. MI-E was most commonly used in spinal muscular atrophy, where it generally coincided with ventilatory support. One-third of MI-E devices were given to children with central nervous system conditions, and one-third also received ventilatory support.

Direct trocar insertion without previous pneumoperitoneum versus insertion after insufflation with Veress needle in laparoscopic gynecological surgery: a prospective cohort study.

The aim of this study was to determine whether direct trocar entry without prior pneumoperitoneum at umbilical level (DTI) can be a safe alternative to access the abdominal cavity in gynaecological laparoscopic surgery. We present a prospective observational analytical study of cohorts, comparing DTI with umbilical entry with trocar after previous insufflation with a Veress needle at umbilical level (V). The study period was performed from June 2013 to April 2016; data was collected on 600 patients who underwent gynaecological laparoscopic surgery. There were no significant differences in the risk of suffering a complication during the access manoeuvres between DTI (6.49%) and V (7.39%), OR 0.89 (95% CI: 0.42-1.81). The duration of the access manoeuvres was 69 s in DTI and 193 s in V (p < .001). The percentage of patients in whom two or more access attempts were performed was lower in DTI (7.8%) than in V (12.3%) (p > .05). We concluded that DTI is at least as safe as V, regarding the risk of suffering complications arising from access into the abdominal cavity. DTI has advantages with regard to V, such as: the shorter duration of access manoeuvres or the lesser number of unsuccessful entry or insufflation attempts. Impact statement What is already known on this subject? There are few international publications comparing DTI and V. When we conducted a search in PubMed for the terms 'Veress needle and direct trocar insertion', 51 publications were obtained. When we increased the restriction and added the terms 'laparoscopic entry and laparoscopy complications', 27 publications were obtained; thus, the uniqueness of our study. What do the results of this study add? We present a 3-year observational prospective study of cohorts that included 600 patients. The aim of this study was to determine that in laparoscopic gynaecological surgery, DTI is an access method to the abdominal cavity at least as safe as V, with respect to the risk of complications. On the other hand, DTI has some advantages such as the shorter duration of access manoeuvres or the lower number of failed entry attempts. What are the implications of these findings for clinical practice and/or further research? Given the limited number of publications that compared both techniques, our study indicates that DTI can be a safe alternative for access to abdominal cavity in gynaecological surgery, compared to the traditional V.

Laparoscopic Entry Technique Using a Veress Needle Insertion with and without Concomitant CO2 Insufflation: A Randomized Controlled Trial.

STUDY OBJECTIVE: To compare the time and number of attempts needed for successful Veress needle entry during laparoscopic surgery using concomitant versus subsequent CO2 insufflation approaches. DESIGN: Randomized controlled trial. SETTING: University teaching hospital. PATIENTS: One hundred consecutive patients scheduled for laparoscopic surgery by 2 high-volume laparoscopic surgeons were screened and randomized, and 95 of these were included in the final analysis. Ninety (45 in each group) was the precalculated priori number of patients needed to detect a 50% difference in the time (seconds) to obtain adequate insufflation with 90% power and alpha of 5%. INTERVENTIONS: Patients were randomized to either Veress needle entry with concomitant (Con) or subsequent (Sub) CO2 insufflation. MEASUREMENTS AND MAIN RESULTS: Forty-six patients were randomized to the Con group and 49 to the Sub group. Patient age, body mass index, prior surgical history, presence of adhesions, and type of procedure performed were similar between both groups. The median time required for adequate insufflation in the Con group was 103.5 seconds (Q1-Q3, 80.0-130.0) compared with 113.0 seconds (Q1-Q3, 102.0-144.0) in Sub group (p = .16). Approximately 89% (95% confidence interval, 80.1%-98.1%) of patients in Con group achieved successful entry in the first attempt compared with only 67% (95% confidence interval, 54.2%-80.0%) in Sub group (p = .01). The incidence of preperitoneal insufflation and failed entry was comparable between the 2 groups. No patient developed solid organ, visceral, or vascular injuries; gas embolism; or case conversion to laparotomy in relation to the Veress needle entry technique. CONCLUSION: Veress needle entry with concomitant CO2 insufflation was associated with a higher rate of successful entry during the first attempt of Veress needle insertion. The total time required for insufflation and rates of complications between the 2 techniques were similar.

Nasal high-flow oxygen therapy improves arterial oxygenation during one-lung ventilation in non-intubated thoracoscopic surgery.

OBJECTIVES: Intraoperative hypoxaemia during one-lung ventilation (OLV) remains a major concern in thoracic surgery. Non-intubated video-assisted thoracic surgery (VATS) involves a greater risk of consequent emergent conversion to endotracheal intubation. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) has recently been reported to be beneficial for higher oxygen reserves during difficult intubations and for enhancing postoperative recovery after thoracic surgery. However, the effects of THRIVE on oxygenation and carbon dioxide elimination before and during OLV in non-intubated VATS have not been investigated. METHODS: Between September 2016 and October 2016, 30 patients underwent non-intubated VATS for lung tumour and were maintained with THRIVE at a flow of 20 l/min. These patients were compared with a historical control group comprising 30 patients who were maintained with oxygen masks at an oxygen flow of 10 l/min using a propensity score matching algorithm between September 2015 and July 2016. RESULTS: The preoperative arterial oxygen tension was significantly higher in patients maintained with THRIVE than it was in patients maintained with oxygen masks (mean 416.0 vs 265.9 mmHg, P < 0.01). During OLV, arterial oxygen tension remained significantly higher in the THRIVE group than in the oxygen mask group (mean 207.0 vs 127.8 mmHg, P = 0.01). The arterial carbon dioxide tension was comparable before and during OLV. CONCLUSIONS: The results indicated that THRIVE effectively increases the oxygen reserve both during OLV and after anaesthesia. Furthermore, non-intubated VATS is safer if THRIVE with flow adjustment is incorporated into a minimally invasive surgical approach, although carbon dioxide elimination is not facilitated.

Laparoscopy Using Room Air Insufflation in a Rural African Jungle Hospital: The Bongolo Hospital Experience, January 2006 to December 2013.

INTRODUCTION: Carbon dioxide is the standard insufflation gas for laparoscopy. However, in many areas of the world, bottled carbon dioxide is not available. Laparoscopy offers advantages over open surgery and has been practiced using filtered room air insufflation since 2006 at Bongolo Hospital in Gabon, Africa. OBJECTIVE: Our primary goal was to evaluate the safety of room air insufflation related to intraoperative and postoperative complications. Our secondary aim was to review the types of cases performed laparoscopically at our institution. METHODS: This retrospective review evaluates laparoscopic cases performed at Bongolo Hospital between January 2006 and December 2013. Demographic and perioperative information for patients undergoing laparoscopic procedures was collected. Insufflation was achieved using a standard, oil-free air compressor using filtered air and a standard insufflation regulator. RESULTS: A total of 368 laparoscopic procedures were identified within the time period. The majority of cases were gynecologic (43%). There was a 2% (8/368) complication rate with one perioperative death. The 2 complications related to insufflation were episodes of hypotension responsive to standard corrective measures. No intracorporeal combustion events were observed in any cases in which the use of diathermy and room air insufflation were combined. The other complications and the death were unrelated to the use of insufflation with air. CONCLUSION: Insufflation complications with room air occurred in our study. However, the complications related to insufflation with room air in our study were no different than those described in the literature using carbon dioxide. As room air is less costly than carbon dioxide and readily available, confirming the safety of room air insufflation in prospective studies is warranted. Room air appears to be safe for establishing and maintaining pneumoperitoneum, making laparoscopic surgery more accessible to patients in low-resource settings.

A Comparison of Cough Assistance Techniques in Patients with Respiratory Muscle Weakness.

PURPOSE: To assess the ability of a mechanical in-exsufflator (MI-E), either alone or in combination with manual thrust, to augment cough in patients with neuromuscular disease (NMD) and respiratory muscle dysfunction. MATERIALS AND METHODS: For this randomized crossover single-center controlled trial, patients with noninvasive ventilator-dependent NMD were recruited. The primary outcome was peak cough flow (PCF), which was measured in each patient after a cough that was unassisted, manually assisted following a maximum insufflation capacity (MIC) maneuver, assisted by MI-E, or assisted by manual thrust plus MI-E. The cough augmentation techniques were provided in random order. PCF was measured using a new device, the Cough Aid. RESULTS: All 40 enrolled participants (37 males, three females; average age, 20.9±7.2 years) completed the study. The mean (standard deviation) PCFs in the unassisted, manually assisted following an MIC maneuver, MI-E-assisted, and manual thrust plus MI-E-assisted conditions were 95.7 (40.5), 155.9 (53.1), 177.2 (33.9), and 202.4 (46.6) L/min, respectively. All three interventions significantly improved PCF. However, manual assistance following an MIC maneuver was significantly less effective than MI-E alone. Manual thrust plus MI-E was significantly more effective than both of these interventions. CONCLUSION: In patients with NMD and respiratory muscle dysfunction, MI-E alone was more effective than manual assistance following an MIC maneuver. However, MI-E used in conjunction with manual thrust improved PCF even further.

Reacciones adversas de la ozonoterapia en pacientes con retinosis pigmentaria / Adverse reactions of ozone therapy in patients with retinitis pigmentosa

Objetivo: describir las reacciones producidas por la ozonoterapia durante la aplicación de la estrategia cubana para pacientes portadores de retinosis pigmentaria. Métodos: se realizó un estudio descriptivo, longitudinal, retrospectivo en 6 414 pacientes portadores de retinosis pigmentaria, atendidos en el Centro Internacional de Retinosis Pigmentaria Camilo Cienfuegos, a quienes se les aplicó ozonoterapia como parte de la estrategia cubana multiterapéutica de control para pacientes portadores de esta enfermedad. En un grupo de pacientes se aplicaron 10 sesiones de autohemoterapia mayor y en otro grupo se administraron 10 sesiones por insuflación rectal. Para la aplicación de la ozonoterapia se utilizó un equipo Ozomed. Los datos estadísticos se analizaron y compararon usando la prueba t de Student. Se consideró p< 0,05 como significación estadística. Resultados: se observaron reacciones adversas en 28 pacientes; de ellos, 5 recibieron ozono por insuflación rectal y 23 por autohemoterapia mayor. Se observaron 4 pacientes con náuseas, 6 con sensación de estómago repleto, 5 con euforia, 1 con fatiga inusual y 1 con sabor metálico bucal. Esto representa el 0,004 por ciento de la muestra estudiada. Conclusión: la ozonoterapia demuestra ser un tratamiento médico muy seguro e inocuo en pacientes con retinosis pigmentaria(AU)

Objective: to describe adverse reactions of ozone therapy after the Cuban strategy for patients with retinitis pigmentosa. Methods: a retrospective, longitudinal and descriptive study was conducted in 6 414 patients with retinitis pigmentosa seen at Camilo Cienfuegos International Center of Retinitis Pigmentosa. They had been treated with ozone therapy as part of the Cuban multi-therapy strategy for management of these patients. A group of patients received ten applications of major autohemotherapy whereas another group was administered 10 ozone sessions through rectal insufflation. The Ozomed machine was the choice for ozone therapy. Student's test was used to analyze and to compare statistical data. Significant statistical index was p< 0,05. Results: twenty eight patients were found to have adverse reactions, 5 of them under rectal insufflation and 23 in the major autohemotherapy group. There were observed 4 patients with nauseas, 6 with stomach bloating, 5 with euphoria, one with unusual fatigue and one with strange metallic taste. This represented 0,004 percent in this sample. Conclusion: the ozone therapy has been found to be an extremely safe medical therapy in patients with retinitis pigmentosa(AU)

Survey of use of the insufflator-exsufflator in patients with spinal cord injury.

BACKGROUND/OBJECTIVE: The insufflator-exsufflator has been shown to be effective in assisting cough in individuals with spinal cord injury. However, many institutions do not use this device. The study was performed to assess use of the device and attitudes among health care providers. METHODS: We developed a questionnaire with 4 categories of questions: knowledge of the device, type of facility, clinical practice with the device, and patient and provider satisfaction. The questionnaire was mailed to members of the American Paraplegia Society. RESULTS: Eighty-six questionnaires (16%) were returned. The device was being used in 49% of the institutions. The device was most commonly used with a tracheostomy; use did not correlate with size or type of facility. Patient and provider satisfaction with the insufflator-exsufflator was high. CONCLUSIONS: The insufflator-exsufflator is used as a means of removal of secretions in approximately one half of institutions polled. Satisfaction with the device is high.

An assessment of the appropriateness of respiratory care delivered at a 450-bed acute care Veterans affairs hospital.

INTRODUCTION: Respiratory care is expensive and time-intensive, inappropriate care wastes resources, and failure to provide necessary and appropriate respiratory care may adversely affect patient outcomes. OBJECTIVE: To determine the appropriateness of basic respiratory care delivered at a 450-bed Veterans Affairs hospital during a 3-month interval. METHODS: We determined (1) the percentage of delivered respiratory care that was not indicated (based on standardized clinical practice guidelines), (2) the percentage of respiratory care that was indicated but not ordered (based on standardized clinical practice guidelines), and (3) the labor cost and potential savings of protocol-based respiratory care at our hospital. We selected 5 assessment days, occurring at 2-week intervals. All patients who received basic respiratory care underwent a complete respiratory care assessment, including medical records review, patient interview, physical assessment, and measurement of blood oxygen saturation (via pulse oximetry) and inspiratory capacity. Intensive care patients were excluded from the study. The assessment instrument provided a standardized format based on American Association for Respiratory Care clinical practice guidelines. RESULTS: We assessed 75 patients. A mean of 24.8% of the delivered respiratory therapies reviewed were not indicated. The percentages of ordered but not indicated therapies were: oxygen 17.7%; all categories of aerosolized medications (bronchodilators, mucolytics, anti-inflammatory agents) 32.4%; chest physiotherapy 37.5%; lung expansion therapy 7.7%. A mean of 11.8% of the patients assessed were not receiving respiratory care that was indicated. The percentages of indicated but not ordered therapies were: oxygen 5.3%; bronchodilator 5.3%; lung expansion therapy 36%. CONCLUSION: A mean of 24.8% of the basic respiratory care procedures delivered were not indicated and 11.8% of patients were not receiving care that was indicated. Inappropriate utilization of respiratory care services may increase costs and adversely affect morbidity, mortality, and duration of stay. We believe that implementation of respiratory care assessment protocols based on nationally accepted clinical practice guidelines can reduce unnecessary care, optimize care delivered, and may reduce costs and improve outcomes.

Complications of laparoscopy: an inquiry about closed- versus open-entry technique.

OBJECTIVE: The purpose of this study was to determine the amount of complications and the incidence of open- versus closed-entry (either by Veress needle or first trocar) technique in gynecologic laparoscopy in The Netherlands. STUDY DESIGN: Questionnaire analysis of members of the Dutch Society for Gynaecological Endoscopy and Minimal Invasive Surgery was combined with a Medline literature search. Data related to complications on entry from January 1,1997, through December 31, 2001, were collected by questionnaire and were separated into group I (Veress needle or first trocar) and group II (open-entry technique). The number of laparoscopy procedures, years of experience, and indications to perform the chosen entry technique were collected. RESULTS: Response rate was 98%. The procedures were performed by 187 gynecologists in 74 hospitals (72%) in The Netherlands. Groups I and II were comparable to each other, with respect to type of clinic (teaching vs nonteaching hospital), the number of procedures, and the experience of gynecologists. One hundred six gynecologists (57%) used only the closed-entry technique. This group reported 31 complications (0.1%) in 31,532 procedures. Even in the case of patients who were at risk for entry-related complications (previous laparotomy, obesity), pneumoperitoneum was established by the closed-entry technique. However, most gynecologists used an alternative insufflation point (eg, Palmer's point). The remaining 81 gynecologists used both entry techniques. However, the open-entry technique was used on special indications and in only 2.0% of cases (range: 1-20%). These special indications were suspected adhesions or previous laparotomy (90%) and obese (7%) or very thin patients (3%). These 81 gynecologists reported 20,027 closed-entry procedures and 579 open-entry procedures and complication rates of 0.12% and 1.38%, respectively (P<.001). Significantly more visceral lesions were found (P<.001) at open-entry technique in group II. Our literature search showed a calculated average entry complication rate for the closed-entry technique for visceral and vascular lesions of 0.44 of 1000 procedures and 0.31 of 1000 procedures, respectively. CONCLUSION: Although 43% of the gynecologists in this study performed the open-entry technique in laparoscopy, Dutch gynecologists seldom use this technique. When it is performed in selected patients, the number of complications is not reduced necessarily. In contrast to published data of general surgeons' findings, the number of entry-related complications in the open technique was significantly higher than the closed-entry technique. There is no evidence to abandon the closed-entry technique in laparoscopy. However, the selection of patients for an open- or alternative-entry procedure is still recommended.

Respiratory system compliance decreases after cardiopulmonary resuscitation and stomach inflation: impact of large and small tidal volumes on calculated peak airway pressure.

The purpose of the present study was to evaluate respiratory system compliance after cardiopulmonary resuscitation (CPR) and subsequent stomach inflation. Further, we calculated peak airway pressure according to the different tidal volume recommendations of the European Resuscitation Council (7.5 ml/kg) and the American Heart Association (15 ml/kg) for ventilation of an unintubated cardiac arrest victim. After 4 min of ventricular fibrillation, and 6 min of CPR, return of spontaneous circulation (ROSC) after defibrillation occurred in seven pigs. Respiratory system compliance was measured at prearrest, after ROSC, and after 2 and 4 l of stomach inflation in the postresuscitation phase; peak airway pressure was subsequently calculated. Before cardiac arrest the mean (+/- S.D.) respiratory system compliance was 30 +/- 3 ml/cm H2O, and decreased significantly (P < 0.05) after ROSC to 24 +/- 5 ml/cm H2O, and further declined significantly to 18 +/- 4 ml/cm H2O after 2 l, and to 13 +/- 3 ml/cm H2O after 4 l of stomach inflation. At prearrest, the mean +/- S.D. calculated peak airway pressure according to European versus American guidelines was 9 +/- 1 versus 18 +/- 3 cm H2O, after ROSC 12 +/- 2 versus 23 +/- 4 cm H2O, and 15 +/- 2 versus 30 +/- 5 cm H2O after 2 l, and 22 +/- 6 versus 44 +/- 12 cm H2O after 4 l of stomach inflation. In conclusion, respiratory system compliance decreased significantly after CPR and subsequent induction of stomach inflation in an animal model with a wide open airway. This may have a significant impact on peak airway pressure and distribution of gas during ventilation of an unintubated patient with cardiac arrest.

The effect of CO2 insufflation rate on the postlaparoscopic shoulder pain.

Shoulder pain (SP) is frequently mentioned in recent literature following laparoscopic operations. In the literature, many causes have been declared to explain shoulder pain after CO2 insufflation, such as direct peritoneal irritation of the CO2 gas, excessive traction of the triangular ligament, and overstretching of the diaphragmatic muscle fibers due to the high rate of insufflation. This study was planned as multicentric, and 76 patients, aged between 35 to 45, were entered into the study. They were all selected by a randomized sampling method, with equal numbers of men and women, to achieve true evaluation. The low flow-rate (LFR) group was insufflated with 2.5 L/min and the high flow-rate (HFR) group with 7.5 L/min. All cases were evaluated by subjective pain classification on postoperative day 3. According to the subjective pain scale method, shoulder pain average was 23.9+/-3.1 in the LFR group and 55.4+/-6.5 in the HFR group. The difference between these groups was significant (p > 0.01). There is no significant difference for the operation time (LFR%: 64+/-15 minutes, HFR: 61+/-20 minutes, p > 0.05). Our results suggest that there is a significant statistical relation between the postoperative shoulder pain levels and increased insufflation rates. For this reason, low insufflation rate significantly reduces the shoulder pain but does not increase the operation time. Therefore, a low insufflation rate should be applied in all cases for patients' comfort and safety.

Helium versus oxygen for tracheal gas insufflation during mechanical ventilation.

OBJECTIVE: To evaluate and compare the effect of tracheal gas insufflation using two gases with different physical properties, helium and oxygen, as an adjunct to conventional mechanical ventilation in patients with respiratory failure. DESIGN: Prospective, intervention study. SETTING: General intensive care unit in a tertiary university medical center. PATIENTS: Seven sedated and paralyzed patients with respiratory failure of various etiologies. All patients were ventilated in the volume-control mode (tidal volume 5 to 7 mL/kg). Inclusion criteria were PaCO2 of > or =50 torr (> or =6.7 kPa), together with peak inspiratory pressure of > or =35 cm H2O and respiratory rate of > or =14 breaths/min. INTERVENTIONS: All patients were intubated with an endotracheal tube that had an additional lumen opening at its distal end, through which tracheal gas insufflation was administered. The tracheal gas insufflation was applied continuously throughout the respiratory cycle at three flow rates (2, 4, and 6 L/min) with two gases, oxygen and helium, while the ventilatory settings were maintained constant. MEASUREMENTS AND MAIN RESULTS: In addition to airway pressures and arterial blood gases, the relative efficacy of tracheal gas insufflation with each gas was estimated using a "coefficient of efficiency" (which we defined as the change in PaCO2/peak inspiratory pressure) compared with baseline measurements. Tracheal gas insufflation with both gases decreased PaCO2 significantly (p < .05) at all flow rates. This effect was accompanied by an increase in airway pressure with both gases (oxygen and helium). However, at flow rates of 6 L/min, tracheal gas insufflation with helium resulted in lower peak inspiratory pressure than with oxygen. Tracheal gas insufflation with helium was more effective (as estimated by the coefficient of efficiency) than with oxygen at all flow rates (p < .05). CONCLUSION: In volume-controlled, mechanically ventilated patients with respiratory failure, tracheal gas insufflation with helium might be suggested as an alternative to oxygen.

Mechanical insufflation-exsufflation. Comparison of peak expiratory flows with manually assisted and unassisted coughing techniques.

Pulmonary complications are major causes of morbidity and mortality for patients with severe expiratory muscle weakness. The purpose of this study was to compare peak cough expiratory flows (PCEFs) during unassisted and assisted coughing and review the long-term use of mechanical insufflation-exsufflation (MI-E) for 46 neuromuscular ventilator users. These individuals used noninvasive methods of ventilatory support for a mean of 21.1 h/d for 17.3 +/- 15.5 years. They relied on manually assisted coughing and/or MI-E during periods of productive airway secretion. They reported a mean of 0.7 +/- 1.2 cases of pneumonia and other serious pulmonary complications and 2.8 +/- 5.6 hospitalizations during the 16.4-year period and no complications of MI-E. A sample of 21 of these patients with a mean forced vital capacity of 490 +/- 370 ml had a mean maximum insufflation capacity (MIC) achieved by a combination of air stacking of ventilator insufflations and glossopharyngeal breathing of 1,670 +/- 540 ml. The PCEFs for this sample were: following an unassisted inspiration, 1.81 +/- 1.03 L/s; following a MIC maneuver, 3.37 +/- 1.07 L/s; with manual assistance by abdominal compression following a MIC maneuver, 4.27 +/- 1.29 L/s; and with MI-E, 7.47 +/- 1.02 L/s. Each PCEF was significantly greater than the preceding, respectively (p < 0.01). We conclude that manually assisted coughing and MI-E are effective and safe methods for facilitating airway secretion clearance for neuromuscular ventilator users who would otherwise be managed by endotracheal suctioning. Severely decreased MIC, but not necessarily vital capacity, is an indication for tracheostomy.

Modes of tracheal gas insufflation. Comparison of continuous and phase-specific gas injection in normal dogs.

Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination accomplished by conventional mechanical ventilation, primarily by reducing the anatomic (series) dead space volume. Dead space proximal to the catheter tip can be reduced by two methods. Fresh gas introduced at the carinal level during inspiration may effectively "bypass" the upper airway. Alternatively, proximal dead space can be "washed out" with fresh gas during expiration to reduce CO2 rebreathing. We examined these two modes of TGI-aided dead space reduction in nine paralyzed normal dogs receiving conventional mechanical ventilation and compared these results to those obtained with a catheter that delivered fresh gas continuously at the same flow rate, thereby accomplishing both bypass and washout. Total inspired tidal volume and cycling frequency were held constant. Differences in CO2 elimination efficiency among the TGI modes were flow dependent. Continuous catheter flow at 5 or 10 L/min reduced PaCO2 and physiologic dead space fraction (VD/VT) more than either proximal bypass or end-expiratory washout (p < 0.001). At the same catheter flow settings expiratory washout tended to improve VD/VT more than did inspiratory bypass. Under the conditions tested, constant tracheal insufflation of fresh gas improves alveolar ventilation by mechanisms that include, but are not limited to, a functional reduction in the dead space proximal to the catheter tip.