Background-Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique migh...Background-Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique might detect sleep-related breathing disorders. Methods and Results-In 22 patients, analog waveforms of the transthoracic impedance signal measured by the pacemaker minute ventilation sensor over the course of a night were visualized, scored for apnea/hypopnea events, and compared with simultaneous polysomnography. Analysis of transthoracic impedance signals correctly identified the presence or absence of moderate to severe sleep apnea (apnea/ hypopnea index, AHI >20 h-1) in all patients (receiver operating characteristics, ROC=10.). The ROC for AHI scores of ≥5 h-1 and 10 h-1 showed an area under the curve of 0.95, P< 0.005, and 0.97, P< 0.0001, respectively. Accuracy over time assessed by comparing events per 5-minute epochs was high (Cronbach αreliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within ±15 seconds revealed agreement in 81%(κ, 0.77; P< 0.001). Conclusions-Detection of apnea/hypopnea events by pacemaker minute ventilation sensors is feasible and accurate compared with laboratory polysomnography. This technique might be useful to screen and monitor sleep-related breathing disorders in pacemaker patients.展开更多
The mechanism of orthodeoxia (OD), or decreased partial pressure of arterial o xygen (PaO2) from supine to upright, a characteristic feature of hepatopulmonary syndrome (HPS), has never been comprehensively elucidated...The mechanism of orthodeoxia (OD), or decreased partial pressure of arterial o xygen (PaO2) from supine to upright, a characteristic feature of hepatopulmonary syndrome (HPS), has never been comprehensively elucidated. We therefore investi gated the intrapulmonary (shunt and ventilation-perfusion <<VA/Q>> mismatching) a nd extrapulmonary factors governing PaO2 in 20 patients with mild to severe HPS (14 males, 6 females; 50 ±3 years old SE) at upright and supine, in random orde r. We set out a cutoff value for OD, namely a PaO2 decrease ≥5%or ≥4mmHg (are a under the receiver operating characteristic curve, 0.96 each). Compared to sup ine, 5 patients stowed OD (PaO2 change, -11%±2%, -7 ±1 mm Hg, P < .05) wit h further VA/Q worsening (shunt +low VA/Q mode increased from 19%±7%to 21% ±7%of cardiac output <<QT>>, P < .05), as opposed to 15 patients who did not (+ 2%±2%, +1 ±1 mm Hg) with VA/Q improvement (from 20%±4%to 16%±4%of QT, P < .01). Cardiac output was significantly lower in OD patients in both positio ns. Changes in extrapulmonary factors at upright, such as increased minute venti lation and decreased QT, were of similar magnitude in both subsets of patients. In conclusion, our data suggest that gas exchange response to OD in HPS points t o a more altered pulmonary vascular tone inducing heterogeneous blood flow redis tribution to lung zones with prominent intrapulmonary vascular dilatations.展开更多
Objective: To determine the accuracy of three tests used to predict successful extubation of preterm infants. Study design: Mechanically ventilated infants with birth weight < 1250 g and considered ready for extuba...Objective: To determine the accuracy of three tests used to predict successful extubation of preterm infants. Study design: Mechanically ventilated infants with birth weight < 1250 g and considered ready for extubation were changed to endotracheal continuous positive airway pressure (ET CPAP) for three minutes. Tidal volumes,minute ventilation (VE), heart rate,and oxygen saturation were recorded before and during ET CPAP. Three tests of extubation success were evaluated: (a) expired VE during ET CPAP; (b) ratio of VE during ET CPAP to VE during mechanical ventilation (VE ratio); (c) the spontaneous breathing test (SBT)- the infant passed this test if there was no hypoxia or bradycardia during ETCPAP. The clinical team were blinded to the results, and all infants were extubated. Extubation failure was defined as reintubation within 72 hours of extubation. Results: Fifty infants were studied and extubated. Eleven (22% ) were reintubated. The SBT was the most accurate of the three tests, with a sensitivity of 97% and specificity of 73% and a positive and negative predictive value for extubation success of 93% and 89% respectively. Conclusion: The SBT used just before extubation of infants < 1250 g may reduce the number of extubation failures. Further studies are required to establish whether the SBT can be used as the primary determinant of an infant’ s readiness for extubation.展开更多
文摘Background-Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique might detect sleep-related breathing disorders. Methods and Results-In 22 patients, analog waveforms of the transthoracic impedance signal measured by the pacemaker minute ventilation sensor over the course of a night were visualized, scored for apnea/hypopnea events, and compared with simultaneous polysomnography. Analysis of transthoracic impedance signals correctly identified the presence or absence of moderate to severe sleep apnea (apnea/ hypopnea index, AHI >20 h-1) in all patients (receiver operating characteristics, ROC=10.). The ROC for AHI scores of ≥5 h-1 and 10 h-1 showed an area under the curve of 0.95, P< 0.005, and 0.97, P< 0.0001, respectively. Accuracy over time assessed by comparing events per 5-minute epochs was high (Cronbach αreliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within ±15 seconds revealed agreement in 81%(κ, 0.77; P< 0.001). Conclusions-Detection of apnea/hypopnea events by pacemaker minute ventilation sensors is feasible and accurate compared with laboratory polysomnography. This technique might be useful to screen and monitor sleep-related breathing disorders in pacemaker patients.
文摘The mechanism of orthodeoxia (OD), or decreased partial pressure of arterial o xygen (PaO2) from supine to upright, a characteristic feature of hepatopulmonary syndrome (HPS), has never been comprehensively elucidated. We therefore investi gated the intrapulmonary (shunt and ventilation-perfusion <<VA/Q>> mismatching) a nd extrapulmonary factors governing PaO2 in 20 patients with mild to severe HPS (14 males, 6 females; 50 ±3 years old SE) at upright and supine, in random orde r. We set out a cutoff value for OD, namely a PaO2 decrease ≥5%or ≥4mmHg (are a under the receiver operating characteristic curve, 0.96 each). Compared to sup ine, 5 patients stowed OD (PaO2 change, -11%±2%, -7 ±1 mm Hg, P < .05) wit h further VA/Q worsening (shunt +low VA/Q mode increased from 19%±7%to 21% ±7%of cardiac output <<QT>>, P < .05), as opposed to 15 patients who did not (+ 2%±2%, +1 ±1 mm Hg) with VA/Q improvement (from 20%±4%to 16%±4%of QT, P < .01). Cardiac output was significantly lower in OD patients in both positio ns. Changes in extrapulmonary factors at upright, such as increased minute venti lation and decreased QT, were of similar magnitude in both subsets of patients. In conclusion, our data suggest that gas exchange response to OD in HPS points t o a more altered pulmonary vascular tone inducing heterogeneous blood flow redis tribution to lung zones with prominent intrapulmonary vascular dilatations.
文摘Objective: To determine the accuracy of three tests used to predict successful extubation of preterm infants. Study design: Mechanically ventilated infants with birth weight < 1250 g and considered ready for extubation were changed to endotracheal continuous positive airway pressure (ET CPAP) for three minutes. Tidal volumes,minute ventilation (VE), heart rate,and oxygen saturation were recorded before and during ET CPAP. Three tests of extubation success were evaluated: (a) expired VE during ET CPAP; (b) ratio of VE during ET CPAP to VE during mechanical ventilation (VE ratio); (c) the spontaneous breathing test (SBT)- the infant passed this test if there was no hypoxia or bradycardia during ETCPAP. The clinical team were blinded to the results, and all infants were extubated. Extubation failure was defined as reintubation within 72 hours of extubation. Results: Fifty infants were studied and extubated. Eleven (22% ) were reintubated. The SBT was the most accurate of the three tests, with a sensitivity of 97% and specificity of 73% and a positive and negative predictive value for extubation success of 93% and 89% respectively. Conclusion: The SBT used just before extubation of infants < 1250 g may reduce the number of extubation failures. Further studies are required to establish whether the SBT can be used as the primary determinant of an infant’ s readiness for extubation.
