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PubMed2005

Other approaches to open-lung ventilation: airway pressure release ventilation.

OBJECTIVE: To review the use of airway pressure release ventilation (APRV) in the treatment of acute lung injury/acute respiratory distress syndrome. DATA SOURCE: Published animal studies, human studies, and review articles of APRV. DATA SUMMARY: APRV has been successfully used in neonatal, pediatric, and adult forms of respiratory failure. Experimental and clinical use of APRV has been shown to facilitate spontaneous breathing and is associated with decreased peak airway pressures and improved oxygenation/ventilation when compared with conventional ventilation. Additionally, improvements in hemodynamic parameters, splanchnic perfusion, and reduced sedation/neuromuscular blocker requirements have been reported. CONCLUSION: APRV may offer potential clinical advantages for ventilator management of acute lung injury/acute respiratory distress syndrome and may be considered as an alternative "open lung approach" to mechanical ventilation. Whether APRV reduces mortality or increases ventilator-free days compared with a conventional volume-cycled "lung protective" strategy will require future randomized, controlled trials.

Animals↗
PubMed2005

Physiologic comparison between conventional mechanical ventilation and transtracheal open ventilation in acute traumatic quadriplegic patients.

OBJECTIVE: To evaluate the efficacy of mechanical ventilation administered through a small-bore, uncuffed tracheotomy tube, so-called transtracheal open ventilation (TOV), in comparison with conventional mechanical ventilation via a cuffed tracheal tube (endotracheal invasive ventilation, EIV). DESIGN: Physiologic study. SETTING: Intensive care unit of a referral trauma center. PATIENTS: Ten acute quadriplegic patients. INTERVENTIONS: In acute quadriplegic patients receiving EIV, TOV was subsequently applied via an uncuffed, small-bore tube (internal diameter of 4 or 5 mm). MEASUREMENTS AND MAIN RESULTS: Compared with EIV, arterial blood gases were not significantly different after 1 hr of TOV (Pao2/Fio2, 222.8 +/- 60.9 vs. 218.5 +/- 60.3; Paco2, 37.8 +/- 7.1 torr [5.04 +/- 0.95 kPa] vs. 35.5 +/- 6.8 torr [4.73 +/- 0.91 kPa], for EIV and TOV, respectively). Respiratory rate (19.5 +/- 4.7 vs. 19.6 +/- 5 breaths/min) and inspiratory effort (pressure-time product of esophageal pressure during a 1-min period, 125.9 +/- 48.4 vs. 112.8 +/- 36.4 cm H2O.sec.min) were also no different between the two modes. After 24 hrs of TOV, compared with EIV and TOV after 1 hr, respiratory rate and arterial blood gases remained stable, and the pressure-time product of esophageal pressure during a 1-min period was slightly, but significantly, reduced (83.5 +/- 16.6 cm H2O.sec.min, p < .05). CONCLUSIONS: In acute quadriplegic patients receiving mechanical ventilation, TOV was as effective as EIV in providing ventilatory support.

Adult↗
PubMed1986

Ventilation and the oculocardiac reflex. Prevention of oculocardiac reflex during surgery for squints: role of controlled ventilation and anticholinergic drugs.

A randomised prospective study was carried out in children undergoing surgery for squint correction, to determine the value of controlled ventilation as a prophylaxis against the occurrence of the oculocardiac reflex. One hundred patients anaesthetised with nitrous oxide/oxygen and halothane were randomly assigned to either ventilated or spontaneously breathing groups of 50 each. Half the patients in each group received glycopyrronium 7.5 micrograms/kg intravenously at the time of induction of anaesthesia. Heart rate, rhythm, blood pressure and end tidal CO2 concentration were monitored throughout. A positive oculocardiac reflex, defined as a fall in heart rate of 20% or more and/or the occurrence of dysrhythmias, was observed in 72% of spontaneously breathing patients and in 100% of ventilated patients not receiving prophylactic intravenous glycopyrronium. The incidence of a positive reflex in patients receiving glycopyrronium was 10% (4 and 16% respectively in spontaneously breathing and ventilated patients). It is concluded that controlled ventilation is of no value as a preventive measure against the occurrence of the oculocardiac reflex in patients undergoing squint surgery and that prophylaxis is safely achieved with the use of intravenous glycopyrronium.

Adolescent↗
PubMed1987

Peak intratracheal pressure during controlled ventilation in infants and children. A computer study of the Servo 900C ventilator.

The mathematical relationship between peak ventilator breathing system pressure displayed on the digital meter of the Siemens SV900C ventilator, and peak intratracheal pressure measured at the distal end of the tracheal tube, was defined and incorporated into a computer program. The mean difference between peak airway pressure calculated by the computer and directly measured peak intratracheal pressure was 0.02 kPa (SD 0.10) in 18 infants and children. The mean difference between ventilator breathing system pressure and intratracheal pressure in the same group was 0.82 kPa (SD 0.91). Bench tests established that the decrease in peak pressure displayed by the ventilator (from 1.36 to 0.38 kPa) while inspiratory time was increased from 20 to 80% of the respiratory period, concealed an increase (from 0.2 to 0.38 kPa) in intratracheal pressure which occurs during this process; and that the large increase in pressure displayed by the ventilator (from 0.3 to 6 kPa) while respiratory frequency was increased from 20 to 120 breaths/minute, concealed a small increase in peak intratracheal pressure (0.2-0.3 kPa) which occurs during this process. These changes were accurately predicted by the computer program. The increase in intratracheal pressure associated with prolonged inspiratory times explains the high incidence of barotrauma which has recently been associated with this procedure in infants.

Child↗
PubMed1995

Low birthweight infants and total parenteral nutrition immediately after birth. I. Energy expenditure and respiratory quotient of ventilated and non-ventilated infants.

The aim of this study was to determine the energy expenditure and respiratory quotient (RQ) of ventilated and non-ventilated low birthweight infants during the first five days of life, in order to determine optimal feeding regimens. Eighty six infants, of birthweight less than 1750 g, were grouped according to whether they were artificially ventilated or breathing air spontaneously, and whether they were parenterally or enterally fed at the time of study. Energy expenditure and respiratory quotient were measured during days 1-5 and the relation of energy expenditure to several explanatory variables was investigated using multiple regression analysis. The energy expenditure of ventilated infants was less than that of spontaneously breathing infants; the differences were significant on days 1-3. The respiratory quotient (mean (SE)) was greater in intravenously fed infants compared with milk-fed--0.99 (0.03) v 0.92 (0.01) (P < 0.05), with 42% of studies of infants receiving total parenteral nutrition (TPN) producing an RQ of > 1.0 compared with 16.6% of milk-fed infants (P < 0.01). There was a significant correlation between glucose intake and RQ (r = 0.39, P < 0.001). The activity scores were measured during 75 studies and scores were significantly higher in spontaneously breathing milk-fed infants compared with ventilated parenterally fed infants. Factors independently related to energy expenditure were: postnatal age (P < 0.01); milk feeds (P < 0.01); and physical activity (P < 0.05). A mix of carbohydrate and fat from day 1 may not only meet energy needs but may also reduce respiratory quotient.

Calorimetry, Indirect↗
PubMed1994

Long-term effects of two different ventilatory modes on oxygenation in acute lung injury. Comparison of airway pressure release ventilation and volume-controlled inverse ratio ventilation.

A total of 18 patients with acute lung injury (ALI) were sequentially ventilated with two different modes of mechanical ventilation, each applied for a period of 24 h: (1) volume-controlled inverse ratio ventilation (VC-IRV), (2) airway pressure release ventilation (APRV). The individual sequence of both ventilatory modes was randomized. Ventilatory minute volume was adjusted for a PaCO2 of 35 to 45 mm Hg at the beginning of the study during the first ventilatory mode and then kept constant within preset limits. Hemodynamic variables were stable and similar during the 24-h periods of VC-IRV and APRV as well. Despite the lower sedation and spontaneous breathing during APRV, oxygen uptake was similar during both ventilatory modes. During the 24-h period of VC-IRV there was no relevant change of either airway pressures, alveolo-arterial O2 tension difference (AaDO2)/fraction of inspired oxygen (FIO2) or venous admixture. In contrast, peak airway pressures (Pawmax) during APRV were significantly lower (about 30%; p < 0.01), and decreased further within 24 h (p < 0.05). During APRV AaDO2/FIO2 and venous admixture improved significantly with time after more than 8 h (AaDO2/FIO2: 487 versus 414 mm Hg; p < 0.01; venous admixture: 20.6 versus 13.9%; p < 0.01; medians of onset versus end). The improvement was significantly different between both ventilatory modes (p < 0.01). We conclude that this indicates a progressive alveolar recruitment over time during ventilation with APRV.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

Hemodynamic effects of external continuous negative pressure ventilation compared with those of continuous positive pressure ventilation in dogs with acute lung injury.

Patients with noncardiogenic pulmonary edema requiring ventilatory assistance are usually supported with CPPV using positive end-expiratory pressure (PEEP), but CPPV requires endotracheal intubation and may decrease cardiac output (QT). The purpose of this study was to examine thoracoabdominal continuous negative pressure ventilation (CNPV) using external negative end-expiratory pressure (NEEP). The effects on gas exchange and hemodynamics were compared with those of CPPV with PEEP, with the premise that CNPV might sustain venous return and improve QT. In 6 supine, anesthetized and paralyzed dogs with oleic-acid-induced pulmonary edema, 30 min of CNPV was alternated twice with 30 min of CPPV. Positive and negative pressure ventilation were carefully matched for fractional inspired oxygen concentration (FIO2 = 0.56), breathing frequency, and tidal volume. In addition, we matched the increase in delta FRC obtained with the constant distending pressures produced by both modes of ventilation. An average of -9 cm H2O of NEEP produced the same delta FRC as 10.8 cm H2O of PEEP. Gas exchange did not differ significantly between the 2 modes. However, QT was 15.8% higher during CNPV than during CPPV (p less than 0.02). Mixed venous oxygen saturation also improved during CNPV compared with that during CPPV (58.3 versus 54.5%, p less than 0.01). Negative pressure ventilation using NEEP may be a viable alternative to positive pressure ventilation with PEEP in the management of critically ill patients with noncardiogenic pulmonary edema. It offers comparable improvement in gas exchange with the advantages of less cardiac depression and the possible avoidance of endotracheal intubation.

Acute Disease↗
PubMed1991

Closure of the ductus arteriosus with indomethacin in ventilated neonates with respiratory distress syndrome. Effects of pulmonary compliance and ventilation.

The reported effects of indomethacin on pulmonary compliance are variable depending upon the patient population and on the degree to which indomethacin resulted in successful ductal closure. Eleven fluid-restricted, furosemide-treated premature infants being mechanically ventilated for respiratory distress syndrome (RDS) who also had a significant patent ductus arteriosus (PDA) had pulmonary function testing performed before and after successful closure of the PDA. The diagnosis of a significant PDA was made by clinical and echocardiographic criteria. Indomethacin was administered at a dosage of 0.2 mg/kg/dose every 12 to 18 h for 1 to 3 doses. To control for the 48-h time interval to achieve ductal closure, nine premature infants being ventilated for RDS but who did not have a significant PDA also had pulmonary function evaluations performed before and after the 48 h. Also, to control for the independent effect of fluid restriction and diuretic therapy on pulmonary compliance, eight such premature infants with a PDA had pulmonary function evaluations performed at a 48-h interval. Successful closure of the ductus with indomethacin was associated with an improvement in compliance and ventilation parameters in all infants in the indomethacin-treated infants. In the indomethacin-treated group, the mean percent improvements were noted in the following parameters: CLdyn, 59.2%; CLI, 78.3%; CLE, 63.3%; VT, 63.3%; VE, 54.6%. There were no significant changes in the pulmonary functions in the 48-h RDS or the 48-h PDA fluid-restricted, furosemide-treated control groups. In conclusion, successful closure of the ductus with indomethacin causes a significant improvement in compliance and ventilation parameters in infants being mechanically ventilated for RDS.

Ductus Arteriosus, Patent↗
PubMed1985

Does intermittent mandatory ventilation correct respiratory alkalosis in patients receiving assisted mechanical ventilation?

One of the claimed advantages of intermittent mandatory ventilation (IMV) over assisted mechanical ventilation (AMV) (assist-control) is the avoidance or correction of acute respiratory alkalosis, ostensibly by allowing patients to achieve normal alveolar ventilation (VA) and PaCO2 through the function of an intact ventilatory drive. However, although respiratory alkalosis in patients being hyperventilated with controlled mechanical ventilation (CMV) can be corrected by a change to IMV, CMV is seldom appropriate for patients with acute respiratory failure, and whether IMV affects respiratory alkalosis in patients triggering the ventilator in the AMV mode has not previously been tested. We studied 26 patients with acute respiratory alkalosis (pH greater than or equal to 7.48) while receiving AMV. Measurements of arterial blood gases and CO2 production (VCO2), and calculation of VA, were performed after 30 min of AMV, repeated after 30 min of IMV at a mandatory rate one half the previous AMV rate, and then repeated again 30 min after a return to the original AMV settings. Mean arterial pH decreased slightly from 7.51 during AMV to 7.48 during IMV, and returned to 7.51 on resumption of AMV (p less than 0.05 for both changes); corresponding mean values for PaCO2 were 28.6, 29.7, and 27.5 mmHg, respectively. These changes were related to an increase in VCO2 during IMV as compared with AMV (p less than 0.05), without a significant alteration in VA. When the mandatory rate was further reduced during IMV from one half to one fourth the prior, triggered AMV rate in 10 patients, no additional reduction in pH occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Pressure support ventilation decreases inspiratory work of breathing during general anesthesia and spontaneous ventilation.

Spontaneous ventilation may offer advantages over controlled mechanical ventilation (CMV), but increase in work of breathing may diminish its usefulness. During general anesthesia, respiratory depression and increased work of breathing often preclude spontaneous ventilation, and patients then receive CMV. We compared the inspiratory work of breathing of anesthetized patients who breathed with pressure support ventilation (PSV) with that associated with a demand gas flow and a standard anesthesia circle system. We studied nine consenting patients who underwent general inhaled anesthesia with or without regional supplementation. An anesthesia/ventilator system (Siemens 900D, Solna, Sweden) provided PSV (5 cm H2O) or demand gas flow during spontaneous inspiration. Gas flow during demand breathing and PSV was initiated when inspiration produced a 2-cm H2O reduction in airway pressure. An anesthesia machine (Dräger Narkomed 3, Telford, Pa.) provided a gas flow rate of 6 L/min through a standard semiclosed circle system. Airway pressure, airway gas flow rate, and esophageal pressure were continuously transduced, and data or signals were conveyed to a computer. Tidal volume and respiratory rate were computed from the flow curve. The inspiratory work of breathing was calculated as the integral of the area subserved by a plot of esophageal pressure and tidal volume during inspiration. Heart rate and mean arterial blood pressure were recorded, and arterial blood was sampled for gas tension and pH analysis. No differences were found in pHa, Paco2, Pao2, tidal volume, respiratory rate, heart rate, or mean arterial blood pressure among the three modes of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2006

Acoustic monitoring of double-lumen ventilated lungs for the detection of selective unilateral lung ventilation.

One-lung intubation (OLI) is among the most common complications of endotracheal intubation. None of the monitoring tools now available has proved effective for its early detection. In this study we investigated the efficacy of acoustic analysis for the detection of OLI. We collected lung sounds from 11 patients undergoing thoracic surgery requiring the placement of a double-lumen tube. Recordings of separate lung ventilation were performed after induction and confirmation of adequate tube positioning, before surgery. Samples of lung sounds were collected by three piezoelectric microphones, one on each side of the chest and one on the right forearm, for background noise sampling. The samples were filtered, the signals' energy envelopes were calculated, and segmentation to breath and rest periods was performed. Each respiration was classified into one of the three categories: bilateral ventilation, selective right-lung ventilation, or selective left-lung ventilation, on the basis of the ratio between the energy signals of each lung. OLI was accurately identified in 10 of the 11 patients during right OLI and in all 11 patients during left OLI. This study suggests that acoustic monitoring is effective for the detection of selective lung ventilation and may be useful for early diagnosis of OLI.

Acoustics↗
PubMed1993

The effects of ventilator working pressure during pressure support ventilation.

The purpose of this study was to examine the consequences of altering ventilator working pressure on airway pressure and flow characteristics during pressure support ventilation (PSV). A ventilator (Siemens Servo 900C) and single lung simulator were used, and graphic read outs, in triplicate, were taken at a variety of combinations of PSV, working pressure, lung compliance, and airway resistance. The graphic read outs were then analyzed for a number of "dependent variables," and multiple regression analyses were performed using working pressure, PSV level, compliance, and resistance as "independent variables." The results show that the relative impact of working pressure on airway pressure and flow will vary with other lung and airway characteristics; also, excessive working pressure results in significantly greater flow rates at 40 ms after onset of inspiratory flow and at maximum flow, greater ringing or overshoot in the circuit, reduced tidal volume and inspiratory time, and reduced area under the airway pressure curve. In conclusion, adjusting ventilator working pressure will significantly affect lung-ventilator interaction in a quantifiable fashion. Further, these findings support clinical evidence that working pressure and/or initial flow rate need to be individualized to ensure optimal airway flow and pressure characteristics.

Airway Resistance↗
PubMed2006

Influence of two different interfaces for noninvasive ventilation compared to invasive ventilation on the mechanical properties and performance of a respiratory system: a lung model study.

BACKGROUND: Noninvasive ventilation (NIV) is increasingly used in intensive care medicine, but only little information is available how different NIV interfaces affect the performance of a ventilatory system. Therefore, we compared delay times, pressure time products (PTPs), and wasted efforts during inspiration among patients receiving invasive ventilation and NIV with a helmet (NIV-h) or a face mask (NIV-fm). METHODS: Using an in vitro lung model capable of simulating spontaneous breathing, gas flow and airway pressure were measured with varying positive end-expiratory pressure and pressure support (PS) levels. Wasted efforts were determined while lung compliance, respiratory rate (RR), continuous positive airway pressure (CPAP), and PS levels were changed. RESULTS: Delay times were more than twice as long with a helmet compared to NIV-fm or invasive ventilation (p < 0.001), but decreased during NIV-h with increasing CPAP (p < 0.001) and PS levels (p < 0.001). During the initial inspiratory phase, PTP was smaller with NIV-h compared to NIV-fm or invasive ventilation, but not so when a complete inspiration with PS was evaluated. Wasted efforts occurred earlier during NIV-h and were aggravated with rising PS, RR, and compliance. CONCLUSIONS: Although delay times are prolonged during NIV-h, PTP is initially smaller compared to NIV-fm and invasive ventilation, indicating less work of breathing due to the high volume the patient can access. Increasing the CPAP or PS level decreases delay times in NIV-h and should therefore be considered whenever possible. Wasted inspiratory efforts occurred at higher RRs and should carefully be monitored during NIV.

Head Protective Devices↗
PubMed1985

Cardiopulmonary response to inspiratory pressure support during spontaneous ventilation vs conventional ventilation.

Twenty-six patients undergoing coronary bypass graft surgery were randomized in two groups. In group 1, 14 patients were subjected to inspiratory pressure support during spontaneous ventilation (IPSSV) and 12 patients in group 2 were treated with conventional ventilation (CV). The outcome of IPSSV was a definite advantage over the conventional ventilation. The patients in IPSSV group needed +/- 3 h of pressure support before tracheal extubation. The other patients in CV group 2 needed +/- 6 h of mechanical ventilation before being weaned off the ventilator.

Adult↗
PubMed1995

Haemodynamic effects of pressure-controlled ventilation versus volume-controlled ventilation in patients submitted to cardiac surgery.

OBJECTIVE: To compare the haemodynamic effects of pressure-controlled ventilation (PCV) with volume-controlled ventilation (VCV) in patients after cardiac surgery. DESIGN: Prospective clinical study. SETTING: Post-operative cardiac surgical ICU. SUBJECTS: Twenty sequential elective adult patients with no previous chronic lung disease and aged less than 70 years old. INTERVENTIONS: One hour after ICU admission and receiving mechanical ventilation utilising sinusoidal flow, patients were divided into two groups according to cardiac index (CI): group I: CI > 2.5 l/min/M2 and group II: CI < 2.5 l/min/M2. They were submitted randomly to 15 minutes' PC or VC mode, a 30-minute wash-out period of mechanical ventilation with a sinusoidal flow pattern, and then alternate PC or VC mode for 15 more minutes. Data were statistically compared using analysis of variance (ANOVA) with a significance level of 5%. Sedatives and muscle relaxants were given as necessary. ENDPOINTS: Data were obtained at the end of 15 minutes under each ventilatory mode, observing a 30-minute interval between each. MEASUREMENTS: Standard cardiorespiratory parameters were measured or calculated using conventional monitoring (including cardiac output), Qs/Qt, A-aDO2 alveolar-arterial oxygen difference, peak inspiratory pressure, mean airway pressure and dynamic compliance (C). RESULTS: No significant differences between PCV and VCV modes, or between groups, were seen in MPAP, MAP, PCWP, RAP, heart rate, O2ER, VO2I, Paw, C, A-aDO2 and Qs/Qt. However, DO2I (p = 0.0063), LVSWI, (p = 0.0001) and RVSWI (p = 0.0053) showed a statistically significant difference between groups I and II. No influence of VCV or PCV on these parameters was seen. There was a slight significant difference between groups for PVR (p = 0.0205). In contrast, CI (p = 0.0001) and SVR (p = 0.0062) showed significant differences among groups, but also a significantly favourable effect of PCV over VCV (p = 0.0239 and p = 0.0318 respectively). Finally, a significant reduction (p = 0.0001) in peak inspiratory pressure with PCV was observed. CONCLUSION: PC and VC ventilatory modes had comparable effects on patients with preserved or depressed cardiac output. Patients ventilated with PCV showed significantly higher values for cardiac index, a decreased SVR, as well as significantly lower values for inspiratory pressure when compared with VCV patients.

Aged↗
PubMed2000

[Proportional assist ventilation: methodology therapeutics on COPD patients compared with pressure support ventilation].

OBJECTIVE: To establish the method for clinical use of proportional assist ventilation (PAV) and evaluate the effect on COPD patients. The main similarities and differences of PAV and pressure support ventilation (PSV) were described. METHODS: 10 ventilated patients of COPD were studied. The elastance and resistance were determined before PAV by both inspiratory-hold technique during a brief period of volume control ventilation and "runaway technique". Either different assist levels of PAV (% assist 80%, 60%, 40%, respectively) or PSV was selected randomly. Values of hemodynamics, blood gas and pulmonary mechanics were monitored. Patients' response was described also. RESULTS: Runaway technique was convenient and reliable. Among different assist percentage no significant difference was found on hemodynamics in stabilized COPD patients. PaO2 was in a good level. Either tidal volume or respiratory rate did not change in a consistent way as the level of assist was decreased. But peak inspiratory pressure was increasing significantly r = 0.928 (P < 0.01) and patients' work of breath had the tendency to decrease (P < 0.05). A significant difference of Borg Category Scale was observed between PAV and PSV [0.50(1.50)] vs [0.75(2.00)], (P < 0.05). No significant difference of hemodynamics was found between the two modes. PaCO2 was significantly higher on PAV than on PSV, 54(24) and 48(23) mm Hg, respectively (P < 0.05). Peak inspiratory pressure on PAV (16 +/- 4) cm H2O was significantly lower than on PSV (21 +/- 3) cm H2O (P < 0.05). CONCLUSIONS: PAV is a feasible method of supporting ventilator-dependent patients that is well tolerated. It can improve breathing pattern and reduce inspiratory effort by decreasing work of breath. PAV can be implemented at much lower peak inspiratory pressure than PSV at the same condition of work of breath by patients. It can also apply proportional pressure support according to patients' ventilatory demand. System that operates according to the theory of PAV is not easy to implement. How to measure elastance and resistance is still a question during the development of PAV.

Aged↗
PubMed2004

Albuterol delivery from a metered-dose inhaler with spacer is reduced following short-duration manual ventilation in a neonatal ventilator-lung model.

INTRODUCTION: Albuterol aerosol is commonly administered to mechanically ventilated neonates via metered-dose inhaler (MDI) with spacer. The spacer increases the dead space in the ventilation circuit, and some institutions limit the amount of time the spacer remains in line, to minimize carbon dioxide retention and the risk of hypercarbia. However, minimizing the amount of time the spacer remains in line might also limit albuterol delivery to the patient. OBJECTIVE: To determine whether limiting the amount of time the spacer is left in line after MDI actuation significantly reduces albuterol delivery. METHODS: We conducted a bench study with a neonatal ventilator-lung model that included a Bird VIP ventilator, in a time-cycled, pressure-limited, continuous-flow mode, with settings to simulate a 1-kg infant with moderate lung disease: peak inspiratory pressure 25 cm H2O, positive end-expiratory pressure 4 cm H2O, respiratory rate 30 breaths/min, inspiratory time 0.35 s, tidal volume approximately 7 mL. The circuit was attached to a 3.0-mm inner-diameter endotracheal tube and a neonatal test lung. We tested 5 methods of MDI albuterol administration. The first 3 methods used a spacer attached to the ETT and either 5, 15, or 30 manual breaths (flow 6 L/min, respiratory rate 30 breaths/min, peak inspiratory pressure 25 cm H2O) were delivered after each MDI actuation (2 actuations). The final 2 methods used an in-line spacer (placed between the circuit Y-piece and the endotracheal tube) with the spacer kept in line for 30 or 60 s after each actuation (2 actuations). A breathing filter was placed between the ETT and test lung to trap the aerosolized albuterol. RESULTS: Mean +/- SD albuterol delivery was 2.3 +/- 0.5%, 3.6 +/- 1.8%, and 5.1 +/- 1.3% after 5, 15, and 30 manual breaths, respectively (p < or = 0.05 for 30 breaths vs 5 and 15 breaths). Albuterol delivery was 3.7 +/- 1.3% when the spacer was left in line for 30 s, versus 3.7 +/- 0.6% when it was left in line for 60 s. CONCLUSIONS: Limiting the time that the spacer was left in line after each MDI actuation significantly reduced albuterol delivery in our neonatal ventilator-lung model.

Administration, Inhalation↗
PubMed2005

Effects of expiratory rib-cage compression on oxygenation, ventilation, and airway-secretion removal in patients receiving mechanical ventilation.

BACKGROUND: Expiratory rib-cage compression, a chest physiotherapy technique, is well known as the "squeezing" technique in Japan. OBJECTIVE: To determine the effects of rib-cage compression on airway-secretion removal, oxygenation, and ventilation in patients receiving mechanical ventilation. SETTING: An intensive care unit of an emergency and critical care center at a tertiary-care teaching hospital in Tokyo, Japan. METHODS: Thirty-one intubated, mechanically ventilated patients in an intensive care unit were studied in a randomized, crossover trial. The patients received endotracheal suctioning with or without rib-cage compression, with a minimum 3-hour interval between the 2 interventions. Rib-cage compression was performed for 5 min before endotracheal suctioning. Arterial blood gas and respiratory mechanics were measured 5 min before endotracheal suctioning (baseline) and 25 min after suctioning. The 2 measurement periods were carried out on the same day. RESULTS: There were no significant differences in the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen, P(aCO2), or dynamic compliance of the respiratory system between the 2 periods (before and after endotracheal suctioning). Moreover, there were no significant differences in airway-secretion removal between the 2 periods. CONCLUSIONS: This study suggests that rib-cage compression prior to endotracheal suctioning does not improve airway-secretion removal, oxygenation, or ventilation after endotracheal suctioning in this unselected population of mechanically ventilated patients.

Combined Modality Therapy↗