Predicting which preemies will fly.
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Aminophylline↗
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A randomized, controlled trial of aminophylline in ventilatory weaning of premature infants.
OBJECTIVES: To determine whether maximal inspiratory force predicts successful neonatal extubation, and whether aminophylline affects maximal inspiratory force or the success rate of extubation. DESIGN: Double-blind, prospective, randomized, placebo-controlled trial. SETTING: Tertiary level neonatal intensive care unit. PATIENTS: A total of 20 ventilated, preterm, newborn infants: birth weight < 2.5 kg; gestation < 35 wks. INTERVENTIONS: Intravenous aminophylline 4 mg/kg bolus followed by 2.5 mg/kg every 6 hrs x three doses, then 1.5 mg/kg every 6 hrs; or placebo. Drug administration began when infants were receiving an FIO2 of < 0.4 and were progressively weaning from assisted mechanical ventilation. A standardized weaning protocol was instituted, and patients were extubated when they were able to tolerate a mechanical ventilatory rate of < 5 cycles/min. MEASUREMENTS AND MAIN RESULTS: Occlusion pressures, including maximal inspiratory force, were measured before aminophylline and daily until endotracheal extubation. Arterial blood gases were measured every 3 hrs, and 24-hr cardiac and respiratory recordings were performed postextubation. Three of ten aminophylline-treated patients failed extubation compared with two of ten placebo infants (p = nonsignificant). Mean apnea frequency postextubation was 0.02/hr in the aminophylline group compared with 0.3/hr in the placebo group (p < .05). Aminophylline had no effect on successful extubation or on maximal inspiratory force. Maximal inspiratory force was not correlated with the success of extubation. Apnea frequency postextubation was significantly reduced by aminophylline. CONCLUSIONS: Aminophylline is an effective prophylaxis for postextubation apnea in the preterm infant but does not affect maximal inspiratory force or increase the success rate of extubation in this patient population.
Airway Resistance↗
Inspiratory flow rate: more may not be better.
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Humans↗
Beneficial effects of helium:oxygen versus air:oxygen noninvasive pressure support in patients with decompensated chronic obstructive pulmonary disease.
OBJECTIVE: To test the hypothesis that, in decompensated chronic obstructive pulmonary disease (COPD), noninvasive pressure support ventilation using 70:30 helium:oxygen instead of 70:30 air:oxygen could reduce dyspnea and improve ventilatory variables, gas exchange, and hemodynamic tolerance. DESIGN: Prospective, randomized, crossover study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Nineteen patients with severe COPD (forced 1-sec expiratory volume of 0.83+/-0.3 l) hospitalized in the intensive care unit for noninvasive pressure support ventilation after initial stabilization with noninvasive pressure support for no more than 24 hrs after intensive care unit admission. INTERVENTIONS: Noninvasive pressure support ventilation was administered in the following randomized crossover design: a) 45 min with air:oxygen or helium:oxygen; b) no ventilation for 45 min; and c) 45 min with air:oxygen or helium:oxygen. MEASUREMENTS AND MAIN RESULTS: Air:oxygen and helium:oxygen decreased respiratory rate and increased tidal volume and minute ventilation. Helium:oxygen decreased inspiratory time. Both gases increased total respiratory cycle time and decreased the inspiratory/total time ratio, the reduction in the latter being significantly greater with helium:oxygen. Peak inspiratory flow rate increased more with helium:oxygen. PaO2 increased with both gases, whereas PaCO2 decreased more with helium:oxygen (values shown are mean+/-SD) (52+/-6 torr [6.9+/-0.8 kPa] vs. 55+/-8 torr [7.3+/-1.1 kPa] and 48+/-6 torr [6.4+/-0.8 kPa] vs. 54+/-7 torr [7.2+/-0.9 kPa] for air:oxygen and helium:oxygen, respectively; p<.05). When hypercapnia was severe (PaCO2 >56 torr [7.5 kPa]), PaCO2 decreased by > or =7.5 torr (1 kPa) in six of seven patients with helium:oxygen and in four of seven patients with air:oxygen (p<.01). Dyspnea score (Borg scale) decreased more with helium:oxygen than with air:oxygen (3.7+/-1.6 vs. 4.5+/-1.4 and 2.8+/-1.6 vs. 4.6+/-1.5 for air:oxygen and helium:oxygen, respectively; p<.05). Mean arterial blood pressure decreased with air:oxygen (76+/-12 vs. 82+/-14 mm Hg; p<.05) but remained unchanged with helium:oxygen. CONCLUSION: In decompensated COPD patients, noninvasive pressure support ventilation with helium:oxygen reduced dyspnea and PaCO2 more than air:oxygen, modified respiratory cycle times, and did not modify systemic blood pressure. These effects could prove beneficial in COPD patients with severe acute respiratory failure and might reduce the need for endotracheal intubation.
Adult↗
Sonographic evaluation of the normal response of subclavian veins to respiratory maneuvers.
Sonography of the subclavian veins is a new noninvasive, simple technique to evaluate the subclavian veins. The physiologic changes of the subclavian veins consistently respond in a predictable manner to simple respiratory maneuvers. The subclavian veins of 11 normal patients (22 veins) whose ages ranged from 18 to 60 years were studied. The most significant change in subclavian vein anteroposterior diameter during respiratory maneuvers (Valsalva/expiration/inspiration) occurred with inspiration (P less than .005), particularly during a sniff, with a mean decrease in diameter of 61%. This baseline evaluation establishes normal sonographic criteria of the subclavian veins. We suggest that real-time ultrasound using a high resolution transducer offers a rapid, reproducible, objective method of evaluating the subclavian vein directly.
Adolescent↗
A prospective, randomized comparison of the Volume Diffusive Respirator vs conventional ventilation for ventilation of burned children. 2001 ABA paper.
UNLABELLED: The Volume Diffusive Respirator (VDR) is a high-frequency time cycled pressure ventilator that can ventilate, oxygenate, and promote secretion removal. The VDR provides ventilation at lower airway pressures than those required for conventional ventilation in the pressure control mode (PCV). A prospective, randomized, institutional review board-approved study was conducted comparing the VDR to PCV in burned children with respiratory failure from all causes. METHODS: Pediatric burn patients requiring ventilation were stratified by presence of inhalation injury and ventilated by VDR or PCV to achieve predefined arterial blood gases. RESULTS: Sixty-four patients were prospectively assigned ventilator type; 32 to VDR, 32 to PCV. Data are reported as mean + SEM. Patient age was 7.4 + 0.7 years, TBSA was 56 + 3%, and number of patients with inhalation injuries was 55 (86%). Maximum peak inspiratory pressure with the VDR was significantly less than with PCV (30.9 + 0.8 cm H2O vs 39.5 + 1.8 cm H2O,P < 0.05) and the best PaO2 /FIO2 ratio was significantly higher with the VDR compared with PCV (563 + 15 vs 507 + 13, P < 0.05). No patient in the VDR group had evidence of barotrauma compared with two in the PCV group. Five patients in the PCV group died compared with two in the VDR group. CONCLUSION: Patients ventilated with the VDR required significantly lower peak inspiratory pressure and achieved a significantly higher PaO2 /FIO2 ratio compared with PCV. This demonstrates the VDR is a safe and effective method of ventilation for pediatric burn patients and it offers advantages when compared with conventional ventilation.
Adolescent↗
Reduced sympathetic cardiovascular drive in young adults with low birth weight: an interesting observation of unknown significance.
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Baroreflex↗
Evidence for lower sympathetic nerve activity in young adults with low birth weight.
OBJECTIVE: A dysfunction of the sympathetic nervous system may contribute to the development of hypertension and obesity in subjects with low birth weight (LBW). The present study examines resting sympathetic nerve traffic and its baroreflex modulation to the muscle vascular bed in healthy LBW subjects. DESIGN: Case-control studies of 13 healthy LBW subjects (< 2500 g at term) aged 20-30 years and 13 normal birth weight subjects (NBW; 3200-3700 g) closely matched for age, gender and body mass index. METHODS: Muscle sympathetic nerve activity (MSNA) recordings from the superficial peroneal nerve, blood pressure and heart rate were obtained at rest, during an inspiratory apnoea and a cold pressor test. Baroreflex function was evaluated by short-term infusion of nitroprusside and phenylephrine, respectively, in nine subjects of each group. RESULTS: During resting conditions burst frequency was significantly lower in LBW subjects (LBW: 24.7 +/- 2.4; NBW: 34.4 +/- 2.1 bursts/min, P < 0.05). When normalized for the different baseline values, baroreflex-mediated changes in MSNA were similar in both groups. Maximal MSNA levels in response to inspiratory apnoea and the cold pressor test did not differ between the groups. Blood pressure and heart rate were similar in LBW and NBW subjects both at rest and during sympatho-excitatory manoeuvres. CONCLUSIONS: Subjects born too small for their gestational age show a significantly lower sympathetic nerve activity under baseline conditions. Given the different baseline values, the sympathetic response to haemodynamic alteration is not affected in LBW subjects, and maximal activation during non-haemodynamic sympatho-excitatory manoeuvres is preserved.
Adult↗
Effects of ketanserin on heart rate and blood pressure variability: implications for the effect on the baroreflex mechanisms.
Ketanserin is an antihypertensive drug with affinity to both serotonin S2- and alpha 1-adrenoceptors. The specific effects of ketanserin on the baroreflex are not fully understood. We, therefore, studied baroreflex regulation based on blood pressure (BP) and heart rate (HR) responses to several maneuvers before and after the administration of 2 x 5 mg of ketanserin i.v. both in supine and in standing posture. Seven young healthy volunteers were investigated. We measured spontaneous variability in HR and BP (Finapres), and performed deep inspiration, Valsalva, and lying-to-standing tests. We also used a modified Valsalva maneuver that consist of Deep Inspiration Breath-holding with closed glottis and EXpiration: DIBEX maneuver. From the BP recordings, peripheral resistance (TPR) and stroke volume (SV) were estimated by the Modelflow method. Thirty minutes after the administration of ketanserin, there was no significant change in mean HR, BP, spectral power of HR and BP variability, baroreflex sensitivity, or Valsalva ratio. Thus ketanserin did not affect the cardiac baroreflex mechanism. However, in standing position, SV increased and TPR decreased under the influence of ketanserin, and BP overshoot after the Valsalva and DIBEX maneuver was significantly decreased as well. There was also no reflex recovery of BP during the DIBEX maneuver in three volunteers, who felt faint. These observations indicate that there is a lack of vasoconstriction. We conclude that ketanserin is not a vasodilator but seems to inhibit vasoconstriction.
Adult↗
Effect of rate and inspiratory flow on ventilator-induced lung injury.
BACKGROUND: We examined the effects of decreasing respiratory rate (RR) at variable inspiratory times (It) and reducing inspiratory flow on the development of ventilator-induced lung injury. METHODS: Forty sheep weighing 24.6+/-3.2 kg were ventilated for 6 hours with one of five strategies (FIO2 = 1.0, positive end-expiratory pressure = 5 cm H2O): (1) pressure-controlled ventilation (PCV), RR = 15 breaths/min, peak inspiratory pressure (PIP) = 25 cm H2O, n = 8; (2) PCV, RR = 15 breaths/min, PIP = 50 cm H2O, n = 8; (3) PCV, RR = 5 breaths/min, PIP = 50 cm H2O, It = 6 seconds, n = 8; (4) PCV, RR = 5 breaths/min, PIP = 50 cm H2O, It = 2 seconds, n = 8; and (5) limited inspiratory flow volume-controlled ventilation, RR = 5 breaths/min, pressure-limit = 50 cm H2O, flow = 15 L/min, n = 8. RESULTS: Decreasing RR at conventional flows did not reduce injury. However, limiting inspiratory flow rate (LIFR) maintained compliance and resulted in lower Qs/Qt (HiPIP = 38+/-18%, LIFR = 19+/-6%, p < 0.001), reduced histologic injury (HiPIP = 14+/-0.9, LIFR = 2.2+/-0.9, p < 0.05), decreased intra-alveolar neutrophils (HiPIP = 90+/-49, LIFR = 7.6+/-3.8,p = 0.001), and reduced wet-dry lung weight (HiPIP = 87.3+/-8.5%, LIFR = 40.8+/-17.4%,p < 0.001). CONCLUSIONS: High-pressure ventilation for 6 hours using conventional flow patterns produces severe lung injury, irrespective of RR or It. Reduction of inspiratory flow at similar PIP provides pulmonary protection.
Animals↗
Quantitative evaluation of the upper airway during nasopharyngoscopy with the Müller maneuver.
OBJECTIVE: To quantitatively examine changes in the upper airway caliber of normal subjects at graded negative inspiratory pressures generated during nasopharyngoscopy with a Müller maneuver. STUDY DESIGN: Eighteen normal subjects prospectively underwent nasopharyngoscopy with Müller maneuvers. Subjects performed graded and maximal effort Müller maneuvers while sitting upright, and maximal-effort Müller maneuvers in the supine position. Two regions of the upper airway--the retropalatal and retroglossal--were examined. METHODS: Images from the endoscopic examination were objectively analyzed by adjusting manually traced airway contours using full-width, half-maximum edge detection algorithm software. The adjusted tracings' area and dimensions through the airway centroid were measured. RESULTS: Müller maneuvers performed at -40 cm H2O resulted in a 64%+/-17% (P = .0001) reduction in upper airway area that consisted of a 51%+/-20% (P = .0001) reduction in the lateral dimension and a 21%+/-24% (P = .0026) reduction in antero-posterior dimension. Müller maneuvers in the retroglossal region did not significantly reduce airway area (P = .575), but demonstrated an altered airway conformation that consisted of lateral narrowing and an increase in antero-posterior dimension. Changes in body position did not result in significant differences in either airway caliber or airway dimension. CONCLUSIONS: Airway caliber during forced inspiration is mediated primarily through changes in the lateral pharyngeal walls. This study has also shown that antero-posterior and lateral airway structures are largely independent in their response to Müller maneuvers. Similarly, the retropalatal and retroglossal regions of the upper airway respond differently to forced negative intraluminal pressure.
Adult↗
Forced inspiration: a laryngoscopy-based maneuver to assess the size of Reinke's edema.
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Airway Obstruction↗
Reanimation of the paralyzed human larynx with an implantable electrical stimulation device.
OBJECTIVES/HYPOTHESIS: Electrical stimulation of the posterior cricoarytenoid muscle, when paced with inspiration, offers a physiological approach to restore ventilation in bilateral laryngeal paralysis without any of the disadvantages associated with conventional treatment. STUDY DESIGN: A prospective study of six patients. METHODS: The patients were successfully implanted with an Itrel II stimulator (Medtronic, Inc). In postoperative sessions, stimulated vocal fold abduction, patient ventilation, and voice were assessed and compared with preoperative values. RESULTS: The optimum stimulus paradigm was a 1- to 2-second train of 1-millisecond pulses delivered at a frequency of 30 to 40 Hz and amplitude of 2 to 7 V. Posterior cricoarytenoid stimulation produced a large dynamic abduction (3.5-7 mm) in three patients and moderate abduction (3 mm) in a fourth patient. The fifth patient showed a large but delayed response of 4 mm to stimulation with some lateralization of the vocal fold. In the sixth patient, stimulated abduction was noted on device implantation but was lost postoperatively. All five patients with stimulated abduction postoperatively met the ventilatory criteria for decannulation, and three patients subsequently had decannulation. Long-term stimulation of the posterior cricoarytenoid muscle had no appreciable effect on voice quality. CONCLUSIONS: Electrical stimulation of the posterior cricoarytenoid muscle shows potential as an improved therapy for bilateral vocal fold paralysis.
Adult↗
Feasibility and effects of a home-care rehabilitation program in patients with chronic obstructive pulmonary disease.
PURPOSE: Pulmonary rehabilitation programs often show beneficial effects in patients with chronic obstructive pulmonary disease (COPD). These programs are usually hospital-based. This study assesses the feasibility and application of a 12-week Home-Care Rehabilitation Program (HCRP), carried out by general practitioners, physiotherapists, and home-care nurses. METHODS: Effects of the HCRP are assessed in 15 COPD patients with moderate to severe airflow limitation (inspiratory vital capacity [IVC]: mean, 75.4 [SD, 13.7] percent predicted, mean FEV1: 45.5 [6.9] percent predicted) and are compared with a stratified and randomized control group (n = 15). RESULTS: All participating disciplines judged the program to be useful and feasible. Patient compliance with the rehabilitation exercises was high. No major problems concerning the rehabilitation program were reported. After the HCRP, 4-minute walking distance improved significantly from 274 m [61] to 301 m [72] and maximal work load (W max), as measured during an incremental cycle test, increased from 75.3 W [24] to 85.3 W [28]. At equal work levels (W submax) during the cycle test both Borg dyspnea and leg effort scores decreased significantly after the HCRP (6.7 [1.3] versus 4.9 [1.7] and 4.2 [2.0] versus 1.7 [2.5], respectively). Changes in walking distance, dyspnea, and leg effort scores at W submax were significantly different between the two groups. IVC and FEV1 did not change significantly. In the control group, no significant changes in any parameter were observed. CONCLUSION: It was possible to design and perform successfully a home-care rehabilitation program, providing both objective and subjective improvements in a group of patients with COPD. A home-care rehabilitation program appears to be a valuable component in the management of COPD patients with a moderate to severe airflow limitation.
Aged↗
High-intensity inspiratory muscle training in patients with chronic obstructive pulmonary disease and severely reduced function.
PURPOSE: This study examined the effects of inspiratory muscle training (IMT) with high-intensity inspiratory pressure loads on respiratory muscle performance and exertional dyspnea. METHODS: This was a randomized single-blind clinical trial. Twenty-seven patients with chronic obstructive pulmonary disease (18 men, 9 women) with severe to very severe airflow obstruction and severely limited functional performance were assigned randomly to an IMT group (n = 12) or an educational control group (n = 15). The IMT group trained with a threshold loaded device for 30 minutes a day for 16 weeks using interval training techniques. Training was initiated with inspiratory pressure loads equal to 30% of maximal inspiratory pressure (Plmax) and increased as tolerated to 60% of Plmax. Dependent variables were measured before and after 4 months of IMT: inspiratory muscle strength (Plmax), respiratory muscle endurance (discontinuous incremental threshold loading test [DC-ITL]), dyspnea (Chronic Respiratory Disease Questionnaire [CRQ]), and the Borg Category-Ratio Scale ratings of perceived breathing difficulty (RPBD) at equal loads during the DC-ITL. RESULTS: In the IMT group, Plmax increased from 64 +/- 15 to 75 +/- 17 cm H2O (P < .05), performance on the DC-ITL test increased from a maximal load of 37 +/- 12 to 53 +/- 13 cm H2O (P < .05), RPBD decreased from 5.5 +/- 2.5 to 3.8 +/- 2.6 for equal loads on the DC-ITL (P < .05) and the CRQ Dyspnea Scale improved from 18.1 +/- 5.1 to 22.4 +/- 5.2 (P < .05). CONCLUSIONS: Inspiratory muscle training at high-intensity loads significantly improved inspiratory muscle strength, respiratory muscle endurance, and respiratory symptoms during daily activities and respiratory exertion.
Aged↗
Descending polyneuropathy in an intravenous drug user.
A 27-year-old male intravenous drug user presented to the Emergency Department of St James's Hospital with a 1-week history of progressive dysphasia, dysphagia and difficulty 'holding his head up' and 'keeping his eyes open'. He also complained of increasing weakness in his upper limbs, as a result of which he kept dropping things. He was on a methadone program but was using both intravenous heroin and cocaine at the time of presentation. Examination of his motor function revealed generalized hypotonia, hyporeflexia and reduced power in both upper limbs. No sensory loss was observed. Co-ordination was intact. The clinical picture of a proximal symmetrical descending weakness and an absence of sensory loss was suggestive of botulism. Clostridium botulinum is a spore-forming, obligate anaerobe. The three forms of human botulism are food-borne, wound and intestinal. A fourth man-made form is produced from aerosolized botulinum toxin and results in inhalational botulism. A little as 1 g of aerosolized botulinum toxin has the potential to kill 1.5 million people. Toxin is detected in serum or stool specimens in only approximately 46% of clinically diagnosed cases. Treatment involves supportive care and early passive immunization with equine antitoxin. Patients should be regularly assessed for loss of gag and cough reflex, control of oropharyngeal secretions, oxygen saturation, vital capacity and inspiratory force. When respiratory function begins to deteriorate, anticipatory intubation is indicated. Early symptom recognition and early treatment with antitoxin are essential in order to prevent mortality, and to prevent additional cases, it is important to ascertain the presence of similar symptoms in contacts of the patient and local public health officials must be notified as one case may herald an outbreak. Given the continued threat of bioterrorism, the Centre for Disease Control Surveillance System in the United States must also be notified of any cases of botulism.
Adult↗
Patient-ventilator asynchrony.
The basic mechanism of patient-ventilator asynchrony is the mismatching between neural inspiratory and mechanical inspiratory time. Alterations in respiratory drive, timing, respiratory muscle pressure, and respiratory system mechanics influence the interaction between the patient and the ventilator. None of the currently available partial ventilatory support modes are exempt from problems with patient-ventilator asynchrony. Ventilator triggering design in the trigger phase and the set variables in the post-trigger phase contribute to patient-ventilator interaction. The set inspiratory flow rate in the post-trigger phase for assist-control volume cycled ventilation affects patient-ventilator asynchrony. Likewise, the initial pressure rise time, the pressure support level, and the flow-threshold for cycling off inspiration for pressure support ventilation are important factors affecting patient-ventilator asynchrony. Current investigations have advanced our understanding in this area; however, its prevalence and the extent to which patient-ventilator asynchrony affect the duration of mechanical ventilation remain unclear.
Humans↗
Optimal end-tidal concentration of sevoflurane to test an ankle clonus in children.
STUDY DESIGN: A prospective randomized study on the end-tidal concentrations of sevoflurane at which ankle clonus existed. SUMMARY OF BACKGROUND DATA: The ankle clonus reflex is a transient neurologic abnormality, which normally occurs in patients during emergence from general anesthesia. OBJECTIVE: To determine the optimal end-tidal concentration of sevoflurane to test an ankle clonus in children during emergence from general anesthesia. METHODS: We studied 30 children (aged 5-15 years). General anesthesia was induced with thiopental sodium. Anesthesia was maintained with sevoflurane, oxygen, and air. At completion of surgery, 3% volume of the end-tidal sevoflurane concentration was maintained for at least 10 minutes. Ankle clonus was checked at 1.0% to 0.1% volume of the end-tidal sevoflurane concentration with an interval of 0.05% volume. RESULTS: Of children, 80% had bilateral ankle clonus, which was found most frequently when patients responded poorly to verbal commands. The median of the end-tidal sevoflurane concentration for a reactive ankle clonus was 0.45% volume (interquartile range 0.5% to 0.4% volume). CONCLUSIONS: The ankle clonus should be tested at 0.45% volume of end-tidal sevoflurane concentration in children undergoing scoliosis surgery during emergence from the general anesthesia.
Adolescent↗