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PubMed1991

Correction of laparoscopic insufflation hypothermia.

Because of the iatrogenic hypothermic stress of a 0.3 degrees C loss created by carbon dioxide pneumoperitoneum insufflation at laparoscopy, it is important to reduce this danger to a minimum. The risk is diminished by increasing the temperature of the delivered carbon dioxide gas to 30.0-30.5 degrees C. This was demonstrated by evaluating 20 patients undergoing laparoscopies with unheated carbon dioxide pneumoperitoneum and 20 with heated carbon dioxide pneumoperitoneum. All procedures were performed without the use of laser or cautery. The group receiving the heated gas had lower and more stable thermal losses. Warming of the carbon dioxide prior to abdominal delivery is recommended to counteract hypothermia.

Abdomen↗
PubMed2000

Usefulness of continuous oxygen insufflation into trachea for management of upper airway obstruction during anesthesia.

BACKGROUND: Severe complications associated with upper airway obstruction often occur during the perioperative period. Development of a simple and reliable technique for reversing the impaired airway patency may improve airway management. The purpose of the current study is to evaluate the usefulness of transtracheal oxygen insufflation (TTI) for management of upper airway obstruction during anesthesia and to explore the mechanisms of TTI in detail. METHODS: During propofol anesthesia in eight spontaneously breathing patients, the upper airway cross-sectional area and pressure-flow measurements during neck flexion with TTI were compared with those during triple airway maneuvers (TAM) without TTI. Blood gas analyses assessed efficacy of CO2 elimination during TTI in an additional nine patients. RESULTS: TTI achieved adequate PaCO2 and PaO2 levels equivalent to those during TAM. In addition to a significantly smaller cross-sectional area during TTI, the location and slope of the pressure-flow relation during TTI completely differed from those during TAM, indicating that upper airway resistance was much higher during TTI. Notably, minute ventilation during TTI was significantly smaller than that during TAM, suggesting reduced dead space or other mechanisms for CO2 elimination. CONCLUSIONS: TTI is capable of maintaining adequate blood gases through mechanisms different from those of conventional airway support in anesthetized subjects with upper airway obstruction.

Adult↗
PubMed1997

Tracheal gas insufflation during pressure-control ventilation: effect of using a pressure relief valve.

OBJECTIVES: Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway pressure, but a consequence of this pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with pressure-control ventilation to augment CO2 elimination. During pressure-control ventilation with continuous TGI, we observed that peak airway pressure increased above the set inspiratory pressure. Based on this observation, we investigated the ability of the pressure-control ventilator circuit to compensate for continuous TGI and the effect of insertion of a pressure relief valve to eliminate over-pressurization. SETTING: University research laboratory. DESIGN: Using an artificial lung model, we studied the effects of continuous TGI with varying catheter flows (0, 2, 6, and 10 L/ min); ventilator frequencies (10 and 20 breaths/min); inspiratory duty cycles (0.33, 0.50, and 0.67); lung compliance (0.01, 0.02, and 0.04 L/cm H2O); and airway resistance (5, 20, and 50 cm H2O/L/sec) on: a) peak airway pressure; b) total inspiratory tidal volume; c) ventilator-derived tidal volume; and d) intrapulmonary pressure at end-exhalation (auto-PEEP). Tests were performed with and without a pressure relief valve whose threshold "pop-off" pressure was adjusted to match the set inspiratory pressure (35 cm H2O) for a total of 432 experimental conditions. MEASUREMENTS AND MAIN RESULTS: Our data demonstrate that pressure-control ventilation augmented with continuous TGI can increase peak airway pressure above set inspiratory pressure due to delivery of a higher than intended tidal volume. Predisposing conditions include catheter flow rates of 6 and 10 L/min, long inspiratory time, low compliance, and low resistance. With the pressure relief valve, peak airway pressure was maintained at the set inspiratory pressure and total inspiratory tidal volume remained constant. CONCLUSION: A pressure relief valve is a necessary adjunct to maintain peak airway pressure at set inspiratory pressure and keep total inspiratory tidal volume constant when continuous TGI is administered in conjunction with pressure-control ventilation.

Airway Resistance↗
PubMed1998

Expiratory phase and volume-adjusted tracheal gas insufflation: a lung model study.

OBJECTIVE: To evaluate in a lung model the effects of expiratory-phase tracheal gas insufflation (expiratory-phase TGI) with both volume and pressure control ventilation, and tidal volume-adjusted continuous flow TGI (volume-adjusted TGI) on system pressures and volumes. DESIGN: Single-compartment lung model. SETTING: Research laboratory in a university medical center. INTERVENTIONS: Expiratory-phase TGI was established, using a solenoid valve activated by the ventilator. Volume-adjusted TGI was applied by reducing tidal volume (VT) by the product of TGI flow and inspiratory time. Ventilation was provided with pressure control of 20 cm H2O or volume control ventilation with VT similar to that with pressure control ventilation. A rate of 15 breaths/min and positive end-expiratory pressure (PEEP) of 10 cm H2O were used throughout. Inspiratory time periods of 1.0, 1.5, 2.0, and 2.5 secs were used with TGI flows of 0, 4, 8, and 12 L/min. Lung model compliance (mL/cm H2O) and resistance (cm H2O/L/sec) combinations of 20/20, 20/5, and 50/20 were used. MEASUREMENTS AND MAIN RESULTS: In expiratory-phase TGI with pressure control ventilation, peak alveolar pressure remained constant, PEEP increased (p < .01) and VT decreased (p < .01). In expiratory-phase TGI with volume control ventilation and volume-adjusted TGI, there were significant increases in peak alveolar pressure and PEEP (p < .01). Readjustment of VT in volume-adjusted TGI was impossible with longer inspiratory time (> or = 2 secs) and higher TGI flows (> or = 8 L/min). CONCLUSIONS: The marked increases in system pressures and volumes observed with continuous-flow TGI can be avoided with expiratory-phase TGI and volume-adjusted TGI.

Insufflation↗
PubMed1998

Air insufflation technique of enteral tube insertion: a randomized, controlled trial.

OBJECTIVE: To test air insufflation as an adjunct to placement of enteral feeding tubes. DESIGN: Prospective, randomized study. SETTING: Intensive care unit in a tertiary hospital. SUBJECTS: Sixty-four consecutive patients requiring enteral nutrition, in whom a decision to insert a nasoenteral feeding tube was made. INTERVENTIONS: A 12-Fr feeding tube was inserted to the level of the fundus of the stomach. A 60-mL syringe was used to pump 500 mL of air into the stomach. The tube was then advanced. An abdominal flat plate was obtained within 2 hrs of completion of the procedure and the tube position noted. If the tube was not in the duodenum, the patient was placed on a promotility agent and a repeat radiograph was performed the next day. The technique varied from our control technique only by the instillation of air. MEASUREMENTS AND MAIN RESULTS: Using the study technique, 21 of 32 tubes were successfully placed, as seen on the initial radiograph, in our study patients compared with only 12 of 34 tubes in our control patients (p< .02). In addition, the success rate at 24 hrs was 25 of 32 vs. 16 of 34 (p< .02). Only 3 of 21 tubes placed in the antrum, body, or fundus of the stomach advanced to the duodenum the following day, compared with 5 of 12 tubes initially placed in the pylorus (p< .075). No complications were noted. CONCLUSION: Instilling air into the stomach may facilitate the ability to get the feeding tube to the level of the pylorus, at which point it is more likely to advance into the duodenum and beyond.

Critical Illness↗
PubMed2000

Auto-positive end-expiratory pressure during tracheal gas insufflation: testing a hypothetical model.

OBJECTIVE: The major benefit of tracheal gas insufflation (TGI) is an increase in CO2 elimination efficiency by removal of CO2 from the anatomical deadspace. In conjunction with mechanical ventilation, TGI may also alter variables that affect CO2 elimination, such as minute ventilation and peak airway pressure (peak Paw) and cause the development of auto-positive end-expiratory pressure (auto-PEEP). We tested the hypothesis that TGI-induced auto-PEEP alters ventilatory variables. We predicted that TGI-induced auto-PEEP offsets the beneficial effects of TGI on CO2 elimination and that keeping total PEEP (ventilator PEEP + auto-PEEP) constant enhances the CO2 elimination efficiency afforded by TGI. DESIGN: Prospective study of two series of patients with acute respiratory distress syndrome receiving mechanical ventilation. SETTING: Intensive care units at a university medical center. PATIENTS: Each series consisted of eight sequential hypercapnic patients. INTERVENTIONS: In series 1, we examined the effect of continuous TGI at 0 and 10 L/min on PaCO2, without compensating for the development of auto-PEEP. In series 2, we examined this same effect of continuous TGI while reducing ventilator PEEP to keep total PEEP constant. TGI-induced auto-PEEP was calculated based on dynamic compliance measurements during zero TGI flow conditions (deltaV/deltaP) after averaging the two baseline values for peak Paw and tidal volume and assuming compliance did not change between the zero TGI and TGI flow conditions (deltaVTGI/deltaPTGI). MEASUREMENTS AND MAIN RESULTS: In series 1, total PEEP increased from 13.2 +/- 3.2 cm H2O to 17.8 +/- 3.5 cm H2O without compensation for auto-PEEP (p = .01). PaCO2 decreased (p = .03) from 56.2 +/- 10.6 mm Hg (zero TGI) to 52.9 +/- 9.3 mm Hg (TGI at 10 L/min), a 6% decrement. In series 2, total PEEP was unchanged (p = NS). PaCO2 decreased (p = .03) from 59.5 +/- 10.4 mm Hg (zero TGI) to 52.2 +/- 8.3 mm Hg (TGI at 10 L/min), a 12% decrement. There was no significant change in PaO2; there were no untoward hemodynamic effects in either series. CONCLUSIONS: These data are consistent with the hypothesis that mechanical ventilation + TGI causes an increase in auto-PEEP that can blunt CO2 elimination. In addition to the ventilator modifications necessary to keep ventilatory variables constant when TGI is used, it is also necessary to reduce ventilator PEEP to keep total PEEP constant and further enhance CO2 elimination efficiency.

Aged↗
PubMed2001

Selective tracheal gas insufflation during partial liquid ventilation improves lung function in an animal model of unilateral acute lung injury.

OBJECTIVE: During unilateral lung injury, we hypothesized that we can improve global lung function by applying selective tracheal gas insufflation (TGI) and partial liquid ventilation (PLV) to the injured lung. DESIGN: Prospective, interventional animal study. SETTING: Animal laboratory in a university hospital. SUBJECTS: Adult mixed-breed dogs. INTERVENTIONS: In six anesthetized dogs, left saline lung lavage was performed until PaO(2)/FiO(2) fell below 100 torr (13.3 kPa). The dogs were then reintubated with a Univent single-lumen endotracheal tube, which incorporates an internal catheter to provide TGI. In a consecutive manner, we studied 1) the application of 10 cm H(2)O of positive end-expiratory pressure (PEEP); 2) instillation of 10 mL/kg of perflubron (Liquivent) to the left lung at a PEEP level of 10 cm H(2)O (PLV+PEEP 10 initial); 3) application of selective TGI (PLV+TGI) while maintaining end-expiratory lung volume (EELV) constant; 4) PLV+TGI at reduced tidal volume (VT); and 5) PLV+PEEP 10 final. MEASUREMENTS AND MAIN RESULTS: Application of PLV+PEEP 10 initial did not change gas exchange, lung mechanics, or hemodynamics. PLV+TGI improved PaO(2)/FiO(2) from 189 +/- 13 torr (25.2 +/- 1.7 kPa) to 383 +/- 44 torr (51.1 +/- 5.9 kPa) (p <.01) and decreased PaCO(2) from 55 +/- 5 torr (7.3 +/- 0.7 kPa) to 30 +/- 2 torr (4.0 +/- 0.3 kPa) (p <.01). During ventilation with PLV+TGI, reducing VT from 15 mL/kg to 3.5 mL/kg while keeping EELV constant decreased PaO(2)/FiO(2) to 288 +/- 49 torr (38.4 +/- 6.5 kPa) (not significant) and normalized PaCO(2). At this stage, end-inspiratory plateau pressure decreased from 19.2 +/- 0.7 cm H(2)O to 13.6 +/- 0.7 cm H(2)O (p <.01). At PLV+PEEP 10 final, measurements returned to those observed at previous baseline stage (PLV+PEEP 10 initial). CONCLUSIONS: During unilateral lung injury, PLV with a moderate PEEP did not improve oxygenation, TGI superimposed on PLV improved gas exchange, and combination of TGI and PLV allowed a 77% reduction in VT without any adverse effect on PaCO(2).

Animals↗
PubMed1995

Intracranial hypertension and adult respiratory distress syndrome: usefulness of tracheal gas insufflation.

The management of increased intracranial pressure (ICP) in patients with an associated acute lung injury is difficult. High levels of PaCO2 as tolerated for permissive hypercapnia are deleterious for cerebral circulation. In such circumstances, tracheal gas insufflation (TGI), which was recently proposed to reduce PaCO2, may be of benefit. We report the cases of two patients with severe adult respiratory distress syndrome and head trauma complicated with elevated ICP. The introduction of TGI decreased PaCO2 by 17 and 26%, decreased ICP, and increased calculated cerebral perfusion pressure. We conclude that TGI could be added to a pressure-targeted strategy of ventilatory management when severe adult respiratory distress syndrome was associated to an intracranial hypertension.

Adult↗
PubMed2003

Glottic-modulated lung ventilation during continuous transtracheal gas insufflation: an experimental study.

We investigated a new method of pulmonary ventilation that included a minitracheostomy, a reverse thrust catheter to deliver continuous flow of gas to the carina, and a threshold valve to avoid lung overinflation. In six lightly sedated healthy sheep, at a continuous flow of 5, 10, or 15 L/min and a threshold valve of 5, 10, 15, or 20 cm H(2)O, we observed a novel respiratory pattern that was characterized either by active lung inflation followed by passive and prolonged inspiratory hold (mixed pattern) or by an absence of all active inspiratory effort and only passive inflation of the lungs (passive pattern). We correlated airway pressure changes with direct visualization of the glottic opening through a fiberoptic bronchoscope. We measured airway pressures at the level of the carina, the subglottic level, and in the pleural space, and respiratory events were monitored through inductive plethysmography. An increase in continuous flow, threshold valve, or both resulted in 1) an increase in glottic breathing; 2) a decrease in respiratory rate, with a decrease in inspiratory pleural pressure excursion; or 3) an increased inspiratory/expiratory ratio and mean airway pressure. During transtracheal gas insufflation, as in this study, a novel respiratory pattern evolved that was modulated by the glottis, accompanied by a decreased effort of breathing; coughing and swallowing remained, and vocalization remained unimpaired.

Airway Resistance↗
PubMed2006

Optimal phasic tracheal gas insufflation timing: an experimental and mathematical analysis.

OBJECTIVE: To investigate the modulation of CO2 clearance by changes in the duration of tracheal gas flow application during tracheal gas insufflation (TGI). DESIGN: Combination of bench studies using a commercial test lung and a commercially available intensive care ventilator and mathematical analysis using a clearance model derived from first principles. SETTING: University pulmonary research laboratory. PATIENTS: None. INTERVENTIONS: Experiments using TGI were performed on a test lung at two combinations of tidal volume and frequency. TGI was limited to part of the expiratory phase (the terminal 10-100% of expiration), and two different TGI catheter flow rates were studied. Permutations over a range of compliances, dead-space volumes, catheter flows, and TGI durations were collected. A mathematical model incorporating key ventilatory and TGI-related variables was developed to provide a first-principles theoretical foundation for interpreting the experimental results. MEASUREMENTS AND MAIN RESULTS: In the physical model, alveolar Pco2 attained a minimum value with TGI flow applied during the terminal 40-60% of the expiratory phase, a finding that was consistent over an almost eight-fold range of expiratory time constants. The mathematical model shows the same qualitative pattern as the experimental model, indicating that the observed behaviors are not an experimental artifact. CONCLUSION: The optimal duration of expiratory TGI flow application is stable over a wide range of impedance characteristics. Such stability suggests that near maximal effect of expiratory TGI could be obtained by applying TGI flow solely within the final 50% of the expiratory phase. Such uniform restriction of the application profile might both simplify technique implementation and decrease adverse consequences.

Carbon Dioxide↗
PubMed2004

A novel laparoscopic technique for removal of foreign bodies from the urinary bladder using carbon dioxide insufflation.

We describe a new technique for extraction of complex foreign bodies from the urinary bladder which cannot be removed through the conventional pediatric cystoscope, thereby avoiding an open cystotomy and the morbidity associated with it. Using cystoscopy as the optical device through the urethra, a 10-mm laparoscopic port can be introduced suprapubically under vision for extraction of complex foreign bodies while the bladder remains insufflated with carbon dioxide at a pressure of 12 mm mercury.

Adolescent↗
PubMed2005

Low-flow transtracheal rescue insufflation of oxygen after profound desaturation.

BACKGROUND: The objective of this study was to determine whether low-flow transtracheal insufflation of oxygen (TRIO) could rescue an animal from profound desaturation. This temporizing maneuver could be useful during cannot-intubate or -ventilate scenarios by resolving hypoxia without the morbidity associated with more invasive procedures. METHODS: Seven swine for a total of 12 runs were studied. Animals were pharmacologically anesthetized, paralyzed, and mechanically ventilated with room air. After disconnection from the ventilator and desaturation to an Spo2 < 50%, low-flow TRIO (2 L/min) was administered for 1 hour. RESULTS: All animals survived and Spo2 increased to greater than 90% in 23 seconds on average. Pao2 (mean, 183 mm Hg) remained elevated throughout the study. Hemodynamic stability was maintained for at least 15 minutes. CONCLUSION: Low-flow TRIO rescued animals from profound hypoxia and maintained oxygenation for at least 1 hour. Low-flow TRIO did not prevent hypercarbia with its subsequent sympathetic activation.

Animals↗
PubMed1995

Pulmonary consequences of carbon dioxide insufflation for laparoscopic cholecystectomies.

Twenty patients having laparoscopic cholecystectomies were studied for changes in thoracic and lung compliance at 5, 10 and 15 mmHg of intra-abdominal pressure. Fifteen mmHg of intra-abdominal pressure decreased the thoracic and the lung static compliance by 49 and 39% respectively. This was unaffected by the degree of head elevation. During the procedure the end-tidal carbon dioxide increased by a mean of 1.6 kPa at 1 h and 2.0 kPa at 2 h. This did not appear to be related to either the mean intra-abdominal pressure or the total volume of carbon dioxide insufflated. The physiological changes and implications for anaesthetic practice are considered.

Abdomen↗
PubMed1990

Negative effect of insufflation on cardiac output and pulmonary blood volume.

In 14 anaesthetized young pigs the changes in pulmonary blood flow and pulmonary blood volume (Qp) during mechanical ventilation were quantified. Ventilation was performed at 10 cycles per min and tidal volume (VT) was adjusted to an arterial PCO2 of about 40 mmHg (5.3 kPa). In 4 animals, 7 ventilatory cycles with an inspiratory pause (IP) of 7.2 s but different tidal volumes were inserted at intervals of 5 min to determine the decrease in Qp (delta Qp) from the differences between right ventricular (Qs,rv) and left ventricular (Qs,lv) stroke volume, and to relate delta Qp to VT. We measured pressure in the aorta (Pao), central veins (Pcv), right and left ventricles (Prv, Plv) pericardium (Pit), and trachea (PT). Blood flow was measured electromagnetically (EM) in the pulmonary artery (Q'pa) and aorta (Q'ao). Stroke volumes were derived from the EM-flow curves. In the other 10 experiments, Qs,lv was derived from the aortic pulse contour. Beat-to-beat analyses of Qs,rv and Qs,lv and blood pressures during the normal ventilatory cycles and those with an IP revealed the following: 1) The end-expiratory RV output and LV output were constant and were defined as baseline values. 2) The accumulated decrease in Qs,rv during insufflation caused a mean deficit in cardiac output of 10.3 +/- 3.2% (s.d.), n = 135; the same was found for Qs,lv, indicating the pulse contour as a useful method to estimate the variations in cardiac output during a ventilatory cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of catheter flow direction on CO2 removal during tracheal gas insufflation in dogs.

Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination by replacing CO2 in the anatomic dead space proximal to the catheter tip with fresh gas during expiration. Turbulence generated by gas exiting the catheter tip may also contribute to alveolar ventilation. To separate distal (turbulence-related) and proximal (washout of dead space) effects of TGI, we compared the efficacy of a straight and an inverted catheter during continuous and expiratory TGI in six mechanically ventilated dogs. We reasoned that the inverted catheter cannot improve CO2 elimination from more distal conducting airways. During continuous TGI with the straight catheter, arterial PCO2 (PaCO2) decreased significantly from baseline (without TGI) of 56 +/- 10 Torr to 38 +/- 8, 36 +/- 8, and 35 +/- 8 Torr at catheter flow rates (Vcath) of 5, 10, and 15 l/min, respectively. For the same conditions, PaCO2 was always higher (P < 0.001) with the inverted catheter (42 +/- 10, 41 +/- 10, and 41 +/- 10 Torr). PaCO2 was lower with the straight (40 +/- 9 Torr) than with the inverted catheter (44 +/- 10 Torr, P < 0.001) during TGI delivered only during expiration at a Vcath of 10 l/min. End-expiratory lung volume relative to baseline increased during continuous, but not during expiratory, TGI and was significantly greater with the straight than with the inverted catheter (P < 0.0001). Our data confirm that the primary mechanism of TGI is expiratory washout of the proximal anatomic dead space but also suggest a minor contribution of turbulence beyond the tip of the straight catheter.

Animals↗
PubMed2003

Continuous tracheal gas insufflation during partial liquid ventilation in juvenile rabbits with acute lung injury.

To examine the hypothesis that combined treatment with tracheal gas insufflation (TGI) and partial liquid ventilation (PLV) may improve pulmonary outcome relative to either treatment alone in acute lung injury (ALI), saline lavage lung injury was induced in 24 anesthetized, ventilated juvenile rabbits that were then randomly assigned to receive (n = 6/group) 1) conventional mechanical ventilation (CMV) alone, 2) continuous TGI at 0.5 l/min, 3) PLV with perfluorochemical liquid, and 4) combined TGI and PLV (TGI + PLV), and subsequently ventilated with minimized pressures and tidal volume (Vt) to keep arterial Po(2) (Pa(O(2))) >100 Torr and arterial Pco(2) (Pa(CO(2))) at 45-60 Torr for 4 h. Gas exchange, lung mechanics, myeloperoxidase, IL-8, and histomorphometry [including expansion index (EI)] were assessed. The CMV group showed no improvement in lung mechanics and gas exchange; all treated groups had significant increases in compliance, Pa(O(2)), ventilation efficacy index (VEI), and EI, and decreases in PaCO(2), oxygenation index, physiological dead space-to-Vt ratio (Vd/Vt), myeloperoxidase, and IL-8, relative to the CMV group. TGI resulted in lower peak inspiratory pressure, Vt, Vd/Vt, and greater VEI vs. PLV group; PLV resulted in greater compliance, Pa(O(2)), and EI vs. TGI. TGI + PLV resulted in decreased peak inspiratory pressure, Vt, Vd/Vt, and increased VEI compared with TGI, improved compliance and EI compared with PLV, and a further increase in Pa(O(2)) and oxygenation index and a decrease in PaCO(2) vs. either treatment alone. These results indicate that combined treatment of TGI and PLV results in improved pulmonary outcome than either treatment alone in this animal model of ALI.

Analysis of Variance↗
PubMed1995

Efficacy of expiratory tracheal gas insufflation in a canine model of lung injury.

Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination by reducing the CO2-laden dead space of the airways. The effect of TGI on PaCO2 diminishes in the setting of acute lung injury (ALI) because an increased alveolar component dominates the total physiologic dead space. Nevertheless, adopting a strategy of permissive hypercapnia should partially offset the decreased efficacy of TGI by increasing CO2 concentration in the proximal airways. To examine these issues we studied the CO2 removal efficacy of expiratory TGI as an adjunct to conventional mechanical ventilation (CMV) before and after oleic acid-induced lung injury (OAI). We first examined the effect of TGI before and after OAI, keeping tidal volume (VT) and frequency constant, and allowing PaCO2 to increase after OAI. We then tested TGI efficiency after matching PaCO2 after OAI to its pre-OAI level by increasing VT (post-OA/VT stage). PaCO2 was 53 +/- 3, 79 +/- 21, and 52 +/- 4 mm Hg in the pre-OAI, post-OAI, and post-OA/VT stages of CMV, respectively. The corresponding decrements in PaCO2 produced by TGI at a flow rate of 10 L/min were 16 +/- 3, 24 +/- 10, and 10 +/- 2 mm Hg, respectively. TGI decreased total physiologic dead space per breath (VD) by 56, 31, and 28 ml during the pre-OAI, post-OAI, and post-OA/VT stages, respectively. Despite a smaller reduction in VD during the post-OAI stage, the effect of TGI on PaCO2 was preserved because of the relatively high PaCO2 prior to its initiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗
PubMed1996

Tracheal gas insufflation-pressure control versus volume control ventilation. A lung model study.

Tracheal gas insufflation (TGI) has been recommended as an adjunct to mechanical ventilation in the presence of elevated Pa CO2. Based on our initial clinical experience with continuous flow TGI and pressure control ventilation (PCV), we were concerned about elevation in peak airway pressure as TGI was applied. In a lung model, we evaluated the effects of continuous flow TGI during both PCV and volume control ventilation (VCV). A single compartment lung model was configured with an artificial trachea into which an 8-mm endotracheal tube was positioned. TGI was established with a 16-G catheter positioned 2 cm beyond the tip of the endotracheal tube. Ventilation was provided by a Puritan-Bennett 7200ae ventilator with PCV 20 cm H2O or VCV with a tidal volume (VTt) similar to that with PCV. A rate of 15 breaths/min and PEEP of 10 cm H2O were used throughout. Inspiratory times (TI) of 1.0, 1.5, 2.0, and 2.5 s were used with TGI of 0, 4, 8, and 12 L/min. Lung model compliance (ml/cm H2O) and resistance (cm H2O/L/s) combinations of 20/20, 20/5, and 50/20 were used. Auto-PEEP, VT, and peak alveolar and airway opening pressures increased as TGI and Ti increased, regardless of lung mechanics settings (p<0.01). All increases were greater with VCV than PCV (p<0.05). Continuous flow TGI with both PCV and VT-uncorrected VCV may result in marked increases in Vt and system pressures, especially at long TI.

Airway Resistance↗