[Home and Long-Term Ventilation Study Group: guidelines for equipment needed for home ventilation. Home and Long-Term Ventilation Study Group].
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Germany↗
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[New techniques of mechanical ventilation: liquid ventilation and partial liquid ventilation].
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Humans↗
Recombinant human deoxyribonuclease shortens ventilation time in young, mechanically ventilated children.
Recombinant human deoxyribonuclease I (dornase alfa) is currently used as an inhaled mucoactive agent in the treatment of cystic fibrosis. In a randomized, placebo-controlled, double-blind clinical study in 100 infants, we investigated whether the therapeutic use of dornase alfa can be extended to ventilated, fluid-restricted children to reduce reintubation rate, ventilation duration, pediatric intensive care unit (PICU) stay, and ventilation complications. While reintubation rates were similar for dornase alfa 7% vs. placebo 9% (odds ratio, 0.77; confidence interval, 0.11-4.9), the incidence of atelectasis (6 vs. 17, respectively; P-value 0.051), median ventilation time (2.2 vs. 3.4 days, respectively; P-value 0.043), median length of PICU stay (7 vs. 8 days, respectively; P-value 0.051), and mean costs (4,830 vs. 6,320, respectively) were lower in the dornase alfa group. No adverse effects were observed, even in critically ill patients. We found that dornase alfa was beneficial and safe. Our findings also indicate that dornase alfa is possibly of value from the first day of mechanical ventilation onward, particularly when longer ventilation (>3 days) is expected in fluid-restricted children after cardiac surgery.
Administration, Inhalation↗
Fungal volatiles associated with moldy grain in ventilated and non-ventilated bin-stored wheat.
The fungal odor compounds 3-methyl-1-butanol, 1-octen-3-ol and 3-octanone were monitored in nine experimental bins in Winnipeg, Manitoba containing a hard red spring wheat during the autumn, winter and summer seasons of 1984-85. Quality changes were associated with seed-borne microflora and moisture content in both ventilated and non-ventilated bins containing wheat of 15.6 and 18.2% initial moisture content. All three odor compounds occurred in considerably greater amounts in bulk wheat in non-ventilated than in ventilated bins, particularly in those with wheat having 18.2% moisture content. The presence of these compounds usually coincided with infection of the seeds by the fungi Alternaria alternata (Fr.) Keissler, Aspergillus repens DeBarry, A. versicolor (Vuill.) Tiraboschi, Penicillium crustosum Thom, P. oxalicum Currie and Thom, P. aurantiogriesum Dierckx, and P. citrinum Thom. High production of all three odor compounds in damp wheat stored in non-ventilated bins was associated with heavy fungal infection of the seeds and reduction in seed germinability. High initial moisture content of the harvested grain accelerated the production of all three fungal volatiles in non-ventilated bins.
Alternaria↗
In vitro evaluation of aerosol bronchodilator delivery during mechanical ventilation: pressure-control vs. volume control ventilation.
OBJECTIVE: To determine the effect of inspiratory time and inspiratory flow pattern on albuterol delivery by aerosol during mechanical ventilation. DESIGN: A ventilator was connected to a lung model and set to deliver a tidal volume of 0.6 l, PEEP 5 cmH(2)O, and respiratory rate of 15/min. We evaluated inspiratory times of 1 and 2 s, lung mechanics of 0.05 l/cmH(2)O compliance and 50 cmH(2)O/l/s resistance, or 0.02 l/cmH(2)O compliance and 5 cmH(2)O/l/s resistance, and three inspiratory flow patterns (constant flow volume-controlled ventilation, descending ramp flow volume-controlled ventilation, and pressure-controlled ventilation). Albuterol was delivered into the ventilator circuit by a nebulizer containing 5 mg (4 ml) albuterol or a pMDI and spacer (four actuations; 360 micro g). A filter between the Y-piece and the lung model collected the aerosol, which was analyzed for albuterol by spectrophotometry. RESULTS: For the nebulizer there were significant differences in albuterol delivered for inspiratory time, flow pattern, and lung mechanics. For the pMDI there were no significant differences for the amount of albuterol delivered for inspiratory time, flow pattern, or lung mechanics. CONCLUSIONS: Albuterol delivery by nebulizer is affected by inspiratory time and inspiratory flow pattern. When a pMDI is used, the amount of albuterol delivered is not affected by inspiratory flow pattern or inspiratory time.
Aerosols↗
Retention of pediatric bag-mask ventilation efficacy skill by inexperienced medical student resuscitators using standard bag-mask ventilation masks, pocket masks, and blob masks.
OBJECTIVE: To measure the ventilation efficacy with three single-sized mask types on infant and child manikin models. METHODS: Medical students were recruited as study subjects inasmuch as they are inexperienced resuscitators. They were taught proper bag-mask ventilation (BMV) according to the American Heart Association guidelines on an infant and a child manikin. Subjects completed a BMV attempt successfully using the adult standard mask (to simulate the uncertainty of mask selection), pocket mask, and blob mask. Each attempt consisted of 5 ventilations assessed by chest rise of the manikin. Study subjects were asked which mask was easiest to use. Four to six weeks later, subjects repeated the procedure with no instructions (to simulate an emergency BMV encounter without immediate pre-encounter teaching). RESULTS: Forty-six volunteer subjects were studied. During the first attempt, subjects preferred the standard and blob masks over the pocket mask. For the second attempt, the blob mask was preferred over the standard mask, and few liked the pocket mask. Using the standard, blob, and pocket masks on the child manikin, 39, 42, and 20 subjects, respectively, were able to achieve adequate ventilation. Using the standard, blob, and pocket masks on the infant manikin, 45, 45, and 11 subjects, respectively, were able to achieve adequate ventilation. CONCLUSIONS: Both the standard and blob masks are more effective than the pocket mask at achieving adequate ventilation on infant and child manikins in this group of inexperienced medical student resuscitators, who most often preferred the blob mask.
Adult↗
Oxygen, arterial blood gases and ventilation are unchanged during dialysis in patients receiving pressure support ventilation.
This study was undertaken to observe whether dialysis-induced alveolar hypoventilation and arterial hypoxaemia occur during bicarbonate haemodialysis in patients receiving partial mechanical support with pressure support ventilation. Nineteen patients admitted to the medical intensive care unit requiring mechanical ventilation and haemodialysis were enrolled. Arterial blood gas, white blood cell (WBC) count, minute ventilation, respiratory rate, breathing pattern and blood pressure were measured according to the following time schedule: pre-dialysis (time 0), and at 15, 30, 60, 120, 180, 240 min thereafter. Results showed that, with the use of cuprammonium dialyser, the WBC count dropped immediately and reached the nadir 15 min after haemodialysis. Thereafter, it recovered and overshot the pre-dialysis values until the end of dialysis. The bicarbonate dialysate indeed resulted in rapid and significant metabolic alkalosis. However, no decrease of PaO2 occurred throughout haemodialysis. The tidal volume, minute ventilation and breathing pattern remained stable during haemodialysis. We conclude that neither dialysis-induced alveolar hypoventilation nor arterial hypoxaemia developed during bicarbonate dialysis in patients mechanically ventilated with the pressure support ventilation.
Adult↗
The influence of controlled mandatory ventilation (CMV), intermittent mandatory ventilation (IMV) and biphasic intermittent positive airway pressure (BIPAP) on duration of intubation and consumption of analgesics and sedatives. A prospective analysis in 596 patients following adult cardiac surgery.
The aim of the study was the determination of the influence of ventilation modes on the consumption of analgesics and sedatives, duration of intubation and pulmonary gas exchange. Assist/controlled mandatory ventilation (S-CMV, 123 patients), synchronized intermittent mandatory ventilation (S-IMV, 431 patients) and biphasic positive airway pressure ventilation (BIPAP, 42 patients) were compared in a prospective, controlled, open clinical trial over an 18-month period. Five hundred and ninety-six adult patients with normal pulmonary function before surgery and uneventful course following coronary artery bypass graft surgery were studied. Patients ventilated with BIPAP had a significantly shorter mean duration of intubation (10.1 h, P < 0.05) than patients treated with S-IMV (14.7 h) and S-CMV (13.2 h). In the S-CMV group, 39.9% of the patients required single or multiple doses of midazolam, but only 13.5% in the S-IMV group and 9.5% in the BIPAP group. The mean total amount of midazolam administered to these patients was significantly higher in the S-CMV group (8.8 mg) than in the S-IMV group (6.6 mg, P < 0.05) and in the BIPAP group (4.3 mg, P < 0.05). The consumption of pethidine and piritramide did not differ between S-CMV and S-IMV, but was significantly lower during BIPAP (P < 0.05). After extubation the patients' PaCO2 was highest in the S-CMV group. We conclude that ventilatory support with BIPAP reduces the consumption of analgesics and sedatives, and the duration of intubation. The possibility of unrestricted spontaneous breathing in all phases of the respiratory cycle is considered to be the reason. BIPAP seems to be an alternative to S-CMV and S-IMV in short-term ventilated patient.
Analgesics↗
Small endotracheal tubes: ventilator and intratracheal pressures during controlled ventilation.
The use of small endotracheal tubes reduces the trauma of intubation. Ventilator and tracheal pressures were measured during controlled ventilation with various tube dimensions and ventilation volumes. Ventilation with large volumes using small tracheal tubes results in high ventilator pressures. However, tracheal pressures are only marginally greater than those obtained with larger tubes. Small endotracheal tubes and high ventilation volumes result in a positive tracheal pressure at the end of expiration. The measured end-expiratory pressures are within the limits which might be used therapeutically (in PEEP). The force required to reshape endotracheal tubes of varvious dimensions to an "anatomical" shape was related to the tube dimensions; the beneficial effects of performed, "anatomically shaped" endotracheal tubes can be achieved by using small tubes of standard design.
Adult↗
Comparison of high frequency jet ventilation to conventional ventilation during severe acute respiratory failure in humans.
High frequency jet ventilation (HFJV) was compared to conventional (high tidal volume, low frequency) ventilation in 9 patients with acute respiratory failure (ARF). Alveolar ventilation was comparable or lower with HFJV in all but one case. When comparisons were made at the same concentration of oxygen and level of PEEP, no consistent change in arterial oxygenation (PaO2) was found. In one case, it was possible to increase PaO2 during HFJV by additional increases in PEEP without elevation in peak airway pressure (AWP) compared to conventional ventilation (CV). At the same level of PEEP, peak AWP was lower during HFJV, except in 1 patient with bronchospasm. Cardiac output did not differ significantly between the 2 ventilation systems, except in the same patient with bronchospasm. HFJV may be useful in acute respiratory failure when peak AWP during CV limits effective use of mechanical ventilation for gas exchange. Patients with significantly elevated airway resistance may be an exception. Improvement in PaO2 will usually depend on increases in PEEP.
Acute Disease↗
The use of conventional ventilators for high frequency positive pressure ventilation.
Ten randomly selected patients were ventilated for defined periods with 2 ventilatory modes: (a) high frequency positive pressure ventilation (HFPPV) (frequency 66-70 min; tidal volume 1-3 ml/kg body weight), (b) conventional IPPV (frequency 16/min; tidal volume (VT) 10-15 ml/kg). This was done successfully using conventional ventilators, and keeping other variables (FIO2, PEEP) constant. Various ventilatory and hemodynamic variables were measured and compared during both modes of ventilation. The most prominent finding was a considerable reduction of cardiac output (CO) and stroke volume (SV) during intermittent positive pressure ventilation (IPPV) compared with HFPPV. Peak tracheal pressure was significantly lower during HFPPV. An increase in mean systemic arterial pressure and in oxygen transport was observed during HFPPV, whereas transpulmonary shunt and pulmonary vascular resistance (PVR) decreased during HFPPV. These findings are in accordance with previously reported advantages of HFPPV, and might be of importance in the treatment of patients with bronchopleural fistula, adult respiratory distress syndrome (ARDS), left ventricular failure and other conditions in which conventional positive pressure ventilation (PPV) fails.
Adult↗
Extreme hypoventilation reduces ventilator-induced lung injury during ventilation with low positive end-expiratory pressure in saline-lavaged rabbits.
OBJECTIVE: To compare the degrees of ventilator-induced lung injury caused by two ventilation protocols. DESIGN: Randomized trial. SETTING: University animal laboratory. SUBJECTS: Sixteen New Zealand white rabbits. INTERVENTIONS: After five sequential saline lung lavages, eight pairs of anesthetized rabbits were allocated randomly to receive either of two ventilation protocols for 4 hrs during neuromuscular blockade. Both groups received 3 cm H2O of positive end-expiratory pressure and 100% oxygen. Control group animals received an estimated tidal volume of 12 mL/kg, an inspiratory time of 0.7 sec, and a ventilatory rate adjusted for a PaCO2 of 35 to 45 torr (4.7 to 6 kPa). Study group animals were ventilated through an intratracheal catheter, with inspiratory time of 1.5 secs, ventilatory rate of 20 breaths/min, and peak inspiratory pressure of 4 to 8 cm H2O, adjusted to maintain PaCO2 at 150 to 250 torr (20 to 33 kPa). MEASUREMENTS AND MAIN RESULTS: Arterial blood gases were measured every 30 mins. After 4 hrs, a final lung lavage was performed. Physiologic parameters, cell counts and protein concentration in the final lavage, and lung histology were compared between groups. The alveolar-arterial oxygen tension gradient was higher in the study group over the first 1.5 hrs, but the time profile showed significantly (p = .001) greater improvement in the study group. After 4 hrs, the mean alveolar-arterial oxygen tension gradient was lower in the study group (94 torr [12.5 kPa] vs. 201 torr [26.8 kPa]). The increase in neutrophil count from the initial to the final lung lavage was lower in the study group (0.27 x 10(7) cells/L vs. 2.01 x 10(7) cells/L, p = .037), as was the absolute value of the neutrophil count in the final lavage (1.33 x 10(7) cells/L vs. 3.02 x 10(7) cells/L, p = .04). The median hyaline membrane score was lower in the study group (0.5 vs. 3.0) but the difference was not statistically significant. CONCLUSION: These findings suggest that a very low tidal volume reduces ventilator-induced lung injury in saline-lavaged rabbits during ventilation at low lung volume.
Animals↗
Cerebral blood flow during partial liquid ventilation in surfactant-deficient lungs under varying ventilation strategies.
OBJECTIVE: To test the hypothesis that cerebral and other regional organ blood flow would be maintained during partial liquid ventilation (PLV) in an animal model of acute lung injury during different ventilation strategies. DESIGN: A prospective, randomized study. SETTING: Animal research facility. SUBJECTS: Sixteen piglets, 2 to 4 wks of age. INTERVENTIONS: Severe lung injury was induced in infant piglets by repeated saline lavage and high tidal volume ventilation. Animals were then randomized to either conventional volume-controlled ventilation or PLV. MEASUREMENTS AND MAIN RESULTS: Organ blood flow was determined in both groups using radiolabeled microspheres under four conditions: high mean airway pressure, Paw; high Paco(2), high Paw; normal Paco(2); low Paw, high Paco(2); low Paw, normal Paco(2). There were no differences in cerebral blood flow during conventional ventilation and PLV, regardless of ventilation strategy. CONCLUSIONS: These results suggest in an acute lung injury model, PLV does not affect cerebral blood flow or other regional organ blood flow over a range of airway pressures.
Journal Article↗
Positive end-expiratory pressure and ventilation inhomogeneity in mechanically ventilated children.
OBJECTIVE: To obtain optimal titration of positive end-expiratory pressure (PEEP) during mechanical ventilation with functional residual capacity and ventilation homogeneity measurements. DESIGN: Experimental human and animal study. INTERVENTIONS: Functional residual capacity and five indices of uneven ventilation (alveolar mean dilution number, mean dilution number, lung clearance index, mixing ratio, and pulmonary clearance delay) were investigated in 22 children aged 0 to 14 yrs with lung disease and in seven rabbits by using a sulfur-hexafluoride wash-out technique. The children and rabbits were exposed to three different levels of PEEP (0, 5, and 10 cm H(2)O for the children and 0, 3 and 6 cm H(2)O for the rabbits). RESULTS: Functional residual capacity of the children increased from 256.9 +/- 178.6 mL (0 PEEP) to 280.0 +/- 201.1 mL (5 PEEP) and to 302.2 +/- 160.4 mL (10 PEEP, p <.001). Ventilation inhomogeneity decreased significantly in all children with increasing PEEP (p <.05). The alveolar mean dilution number decreased from 2.00 +/- 0.29 (0 PEEP) to 1.82 +/- 0.37 (5 PEEP) and to 1.66 +/- 0.34 (10 PEEP), and pulmonary clearance delay decreased from 74.9 +/- 24.2% to 66.6 +/- 38.1% and to 63.9 +/- 24.2%, respectively. The reduction in ventilation inhomogeneity was associated with an improvement in Pao(2) from 101 +/- 42 mm Hg (0 PEEP) to 122 +/- 48 mm Hg (5 PEEP) and to 126 +/- 53 mm Hg (10 PEEP). Functional residual capacity of the rabbits increased from 54.1 +/- 18.7 mL at 0 PEEP to 72.3 +/- 23.4 mL at 3 PEEP and to 93.9 +/- 27.3 mL at 10 PEEP. Alveolar mean dilution number decreased from 2.93 +/- 0.1 (0 PEEP) to 2.20 +/- 0.29 (3 PEEP) and to 1.45 +/- 0.13 (6 PEEP). CONCLUSIONS: In children with lung disease receiving ventilatory support, optimal PEEP titration can be obtained by the measurement of the functional residual capacity and ventilation distribution by using a sulfur-hexafluoride wash-in-wash-out technique.
Journal Article↗
Is there a "right" way to wean my patient from the ventilator? A critical appraisal of Randolph et al: Effect of mechanical ventilator weaning protocols on respiratory outcomes in infants and children: A randomized controlled trial (JAMA 2002; 288:2561-2568).
OBJECTIVE: To review the findings and discuss the implications of mechanical ventilator weaning protocols in children. DESIGN: A critical appraisal of Randolph et al. Effect of mechanical ventilator weaning protocols on respiratory outcomes in infants and children: A randomized controlled trial. JAMA 2002;288:2561-2568, and literature review. FINDINGS: There was no difference in ventilator weaning times between children randomized to a ventilator weaning protocol (pressure support, volume support, or no protocol). However, the study did show that increased sedative use during the first 24 hrs of weaning (the only time during which these data were collected) was an important predictor of weaning duration (p < .001) and weaning failure (p = .04). CONCLUSIONS: The majority of children are weaned from mechanical ventilation over a short period of time. Weaning protocols may not shorten this brief duration of weaning but may have other advantages such as improved collaboration between healthcare team members. Future research into the effects of sedation on weaning from mechanical ventilation is needed in children.
Journal Article↗
Comparison of proportional assist ventilation and pressure support ventilation in chronic respiratory failure due to neuromuscular and chest wall deformity.
BACKGROUND: The physiological and symptomatic effects of proportional assist ventilation (PAV) and pressure support ventilation (PSV) were compared in stable awake patients with neuromuscular and chest wall deformity (NMCWD). METHODS: Oxygen saturation (SaO(2)), transcutaneous carbon dioxide (TcCO(2)), minute ventilation (VE), tidal volume (VT), respiratory rate (RR), and diaphragm electromyography (EMGdi) were measured in 15 patients during both modes. Subjective effort of breathing and synchrony with the ventilator were assessed using visual analogue scales. RESULTS: Three of 15 patients failed to trigger the ventilator in either mode and were excluded. In the 12 remaining patients there were similar improvements in SaO(2), TcCO(2), VE, VT, and RR during both modes. The mean (SD) percentage fall in EMGdi was greater during PSV (-80.5 (10.7)%) than during PAV (-41.3 (35.2)%; p= 0.01). Effort of breathing (p=0.004) and synchrony with the ventilator (p=0.004) were enhanced more with PSV than with PAV. CONCLUSION: Both PSV and PAV produced similar improvements in physiological parameters. However, greater diaphragm unloading was observed with PSV than with PAV, associated with greater symptomatic benefit. These findings suggest that tolerance to PAV may be compromised in patients with NMCWD.
Analysis of Variance↗
Influence of respiratory behavior on ventilation, respiratory work and intrinsic PEEP during noninvasive nasal pressure support ventilation in normal subjects.
BACKGROUND: In clinical practice, patients have different inspiratory behaviors during noninvasive pressure support ventilation (PSV): some breathe quietly, others actively help PSV by an additional effort, and others even resist the inspiratory pressure of PSV. OBJECTIVE: What is the influence of patient collaboration (inspiratory behavior) on the efficiency of PSV? METHODS: We ventilated 10 normal subjects with nasal PSV (inspiratory/expiratory: 10/0 and 15/5 cm H(2)O) and measured their flow and volume with a pneumotachograph and their esophageal and gastric pressures during three different respiratory voluntary behaviors: relaxed inspiration, active inspiratory work and resisted inspiration. RESULTS: When compared with relaxed inspiration with 10/0 cm H(2)O PSV: (1) an active inspiratory effort increased tidal volume (from 789 +/- 356 to 1,046 +/- 586 ml; p = 0.006), minute ventilation (from 10.40 +/- 4.45 to 15.77 +/- 7.69 liters/min; p < 0.001), transdiaphragmatic work per cycle (from 0.55 +/- 0.33 to 1.72 +/- 1.40 J/cycle; p = 0.002) and inspiratory work per cycle (from 0.14 +/- 0.20 to 1.26 +/- 1.01 J/cycle; p = 0.003); intrinsic positive end-expiratory pressure (PEEP(i)) increased from 1.23 +/- 1.02 to 3.17 +/- 2.30 cm H(2)O; p = 0.002); (2) a resisted inspiration decreased tidal volume (to 457 +/- 230 ml; p = 0.007), minute ventilation (to 6.93 +/- 3.04 liters/min; p = 0.028) along with a decrease in transdiaphragmatic work but no change in PEEP(i). Data obtained during a bilevel PSV of 15/5 cm H(2)O were similar to those obtained with the 10/0 cm H(2)O settings. CONCLUSIONS: Active inspiratory effort increases ventilation during PSV at the expense of an increased breathing work and PEEP(i). Resisted inspiration inversely decreases inspiratory work and ventilation with no air trapping. These differences between inspiratory behaviors could affect the expected beneficial effects of PSV in acutely ill patients.
Adult↗
Effect of different levels of pressure support and proportional assist ventilation on breathing pattern, work of breathing and gas exchange in mechanically ventilated hypercapnic COPD patients with acute respiratory failure.
BACKGROUND: Proportional assist ventilation (PAV) has been shown to maintain better patient-ventilator synchrony than pressure support ventilation (PSV); however, its clinical advantage regarding invasive ventilation of COPD patients has not been clarified. OBJECTIVES: To compare the effect of PAV and PSV on respiratory parameters of hypercapnic COPD patients with acute respiratory failure (ARF). METHODS: Nine intubated hypercapnic COPD patients were placed on the PAV or PSV mode in random sequence. For each mode, four levels (L1-L4) of support were applied. At each level, blood gases, flow, tidal volume (VT), airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp - fv) were measured. RESULTS: We found increases in ME with increasing levels of PSV but not with PAV. PO2 and VT increased whereas PCO2 decreased significantly with increasing levels of PSV (p < 0.05). With PAV, PCO2 decreased and VT increased significantly only at L4 whereas PO2 increased from L1 to L4. Runaways were observed at L3 and L4 of PAV. The pressure-time product (PTP) was determined for effective and missing breaths. The mean total PTP per minute (of effective plus missing breaths) was 160 +/- 57 cm H2O/s.min in PSV and 194 +/- 60 cm H2O/s.min in PAV. CONCLUSION: We conclude that in COPD patients with hypercapnic ARF, with increasing support, PSV causes the appearance of ME whereas PAV develops runaway phenomena, due to the different patient-ventilator interaction; however, these do not limit the improvement of blood gases with the application of both methods.
Acute Disease↗