BACKGROUND: Bronchoscopy in patients on mechanical ventilation is being performed much more frequently. However, there is little data on the changes in physiologic parameters and no established mechanical ventilation protocol during bronchoscopy. A decreasing or the removal of positive end-expiratory pressure (PEEP) during bronchoscopy may precipitate severe hypoxemia and/or derecruitment. METHODS: Our standardized mechanical ventilation protocol, without changing the PEEP level, was used during bronchoscopy. The physiological parameters were measured during the bronchoscopic procedure. RESULTS: During bronchoscopy, respiratory acidosis, elevation of peak pressure, elevation of heart rate and auto-PEEP were developed, but were reversible changes. Procedure-related gross barotraumas or other severe complications did not developed. CONCLUSION: No serious complications developed during bronchoscopy under our standardized mechanical ventilation protocol when the PEEP level remained unchanged. The procedure time should be kept to a minimum to decrease the exposure time to undesirable physiological changes.
Acidosis, Respiratory ; Anoxia ; Barotrauma ; Bronchoscopes ; Bronchoscopy* ; Heart Rate ; Humans ; Intensive Care Units ; Intubation, Intratracheal ; Positive-Pressure Respiration ; Positive-Pressure Respiration, Intrinsic ; Pulmonary Gas Exchange ; Respiration, Artificial ; Respiratory Mechanics

OBJECTIVE: To better understand the significance of the pressure-time curve and flow-time curve from the perspective of PB840 ventilator working principle. METHODS: (1) Mechanical principle: flow supply valves (air valve and oxygen valve) and exhalation valve in PB840 ventilator were controlled to achieve the ventilation target (volume or pressure) by the central processing unit according to the monitoring data from pressure sensors (P₁ at the supply side, P₂ at the exhalation side) and flow sensors (Q₁ at the air side, Q₂ at the oxygen side, Q₃ at the exhalation side). (2) The essence of curve: each point means a value of pressure or flow at a certain time measured by the sensors or calculated by the system. (3) The respiratory process could be divided into inspiratory part, expiratory part, and the connection part from expiratory to inspiratory. The air running state and the respiratory mechanics relationship at the three parts could be inferred according to the form of curves. RESULTS: (1) Inspiratory process: at volume-controlled and constant flow ventilation: there should be a relationship "Pc-Pa = XR" between alveolar pressure (Pa) and circuit pressure (Pc) according to Ohm law. So, the Pc curve (pressure-time curve) could indirectly reflect the Pa curve with the flow (X) and resistance (R) being constant. At pressure-set ventilation: it is the goal of ventilator to maintain the Pc at the target level. So, the stability of the target pressure line in pressure-time curve reflects the matching ability of the flow supply valves and the exhalation valve. (2) Expiratory process: it could be divided into pre-expiratory [without basic flow (Ba) or bias flow (Bi)] and post-expiratory (with Ba or Bi), where Ba or Bi is equal to "Q₁+Q₂". So, the mathematical function are "X(t) = Q_3t" in pre-part, and "X(t) = Q_3t-(Q_1t+Q_2t)" in post-part. The relationship between pressure and flow at peak expiratory flow point: it could be found that there is an obvious time span and area formation under the curve from 0 to peak point (Fpeak) after stretching the abscissa axis of flow-time curve. It means that some gas have been discharged from the lung when it arrives at the peak point. So, the alveolar pressure should be lower than the platform pressure at the point (Pplat). The circuit pressure is significantly higher than positive end expiratory pressure (PEEP) at the point in the stretching axis diagram. So, it means that the formula "R_E = (Pplat-PEEP)/Fpeak" to calculate the expiratory resistance (_E) is unreasonable in the angle of Ohm law. (3) The process from exhalation to inspiratory: according to the difference of the starting point of the conversion, it could be divided into two cases: one is that the inspiratory started from the ending of exhalation. Here, the inhaling starting point is lying in the abscissa axis. The other is that the inspiratory started before the ending of exhalation (with endogenous positive end expiratory pressure). Here, the starting point is lying below the abscissa axis, and the slope of the following curve is obviously larger than the slope of natural expiratory curve. According to the difference of results from the starting point to the end of the inhalation triggering effort, it could be divided into two cases: one is that it reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis until an effective air supply is triggered. The other is that it could not reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis, but then runs downward (meaning exhaling). CONCLUSIONS It is helpful to analyze the ventilation state, ventilation failure, and the causes of man-machine confrontation with understanding the ventilation principle and the air route map of the ventilator.
Exhalation ; Humans ; Positive-Pressure Respiration ; Respiration, Artificial ; Respiratory Insufficiency ; Respiratory Mechanics ; Ventilators, Mechanical

No abstract available.
Respiration, Artificial* ; Respiratory Mechanics*

BACKGROUND: Pressure-controlled ventilation (PCV) is frequently used recently as the initial mode of mechanical ventilation in the patients with respiratory failure. Theoretically, because of its high initial inspiratory flow, pressure-controlled ventilation has lower peak inspiratory pressure and improved gas exchange than volume-controlled ventilation (VCV). But the data from previous studies showed controversial results about the gas exchange. Moreover, the comparison study between PCV and VCV with various inspiration:expiration time ratios (I:E ratios) is rare. So this study was performed to compare the respiratory mechanics and gas exchange between PCV and VCV with various I:E raitos. METHODS: Nine patients receiving mechanical ventilation for respiratory failure were enrolled. They were ventilated by both PCV and VCV with various I:E ratios (1:2, 1:1.3 and 1.7:1). FiO2, tidal volume, respiratory rate and external positive end-expiratory pressure (PEEP) were kept constant throughout the study. After 20 minutes of each ventilation mode, arterial blood gas, airway pressures, expired CO2 were measured. RESULTS: In both PCV and VCV, as the I:E ratio increased, the mean airway pressure was increased, and PaCO2 and physiologic dead space fraction were decreased. But P(A-a)O2 was not changed. In all three different I:E ratios, peak inspiratory pressure was lower during PCV, and mean airway pressure was higher during PCV. But PaCO2 level, physiologic dead space fraction and P(A-a)O2 were not different between PCV and VCV with three different I:E ratios. CONCLUSION: There was no difference in gas exchange between PCV and VCV under the same tidal voulme, frequency and I:E ratio.
Humans ; Positive-Pressure Respiration ; Respiration, Artificial ; Respiratory Insufficiency ; Respiratory Mechanics* ; Respiratory Rate ; Tidal Volume ; Ventilation*

To learn reading respiratory waveform and ring is a key step to good use of respirator, which will help clinicians to analyze the status of the use of respirator and real time changes in patient's lung mechanics from the changes of respiratory wave and ring, for making use of respirator reasonably, scientifically and objectively to provide advanced methods. This article only explains the physical basis of respiratory wave and ring.
Respiration ; Respiration, Artificial ; methods ; Respiratory Mechanics

In this study, we investigated the effect of time gating threshold on the delivered dose at a organ with internal motion by respiration. Generally, the internal organs have minimum motion at exhalation during normal breathing. Therefore to compare the dose distribution time gating threshold, in this paper, was determined as the moving region of target during 1 sec at the initial position of exhalation. The irradiated fields were then delivered under three conditions; 1) non-moving target 2) existence of the moving target in the region of threshold (1sec), 3) existence of the moving target region out of threshold (1.4 sec, 2 sec). And each of conditions was described by the moving phantom system. It was compared with the dose distributions of three conditions using film dosimetry. Although the treatment time increased when the dose distributions was obtained by the internal motion to consider the TGT, it could be obtained more exact dose distribution than in the treatment field that didn't consider the internal motion. And it could be reduced the unnecessary dose at the penumbra region. When we set up 1.4 sec of threshold, to reduce the treatment time, it could not be obtained less effective dose distribution than 1 sec of threshold. Namely, although the treatment time reduce, the much dose was distributed out of the treatment region. Actually when it is treated the moving organ, it would rather measure internal motion and external motion of the moving organ than mathematical method. If it could be analyzed the correlation of the internal and external motion, the treatment scores would be improved.
Exhalation ; Film Dosimetry ; Respiration*

BACKGROUND: Reduced lung compliance and increased lung resistance are the primary lung mechanical abnomalities in acute respiratory distress syndrome (ARDS). Although there is little information regarding the mecha nisms responsible for the increases in the respiratory resistance of ARDS, bronchodilators have been frequently administered in mechanically ventilated ARDS patient. To determine the effect of a bronchodilator on the respiratory mechanics depending on the level of applied positive end-expiratory pressure (PEEP), the change in the respiratory mechanics by salbutamol ingalation was measured under the variable PEEP level in patients with ARDS. METHODS: Fifteen mechanically ventilated paralyzed ARDS patientss (14 of male, mean age 57 years) were enrolled in this study. The respiratory system compiance, and the maximum and minimun inspiratory occlusion method during constant flow inflaction using the CP-100 pulmonary monitor (Bicore, Irvine, CA, USA). The measurements were performed at randomly applied 8, 10 and 12 cm H2O PEEP before and 30 mins after administrating salbutamol using a meter-dose-inhaler (100 micro gram X 6). RESULTS: 1) The maximum inspiratory resistance of the lung was higher than the reported normol values due to an increase in the minimal inspiratory resistance and additional resistance. 2) The maximum inspiratory resistance and peak airway pressure were significantly higher at 12 cm H2O of PEEP compared with those at 10cm H2O of PEEP. 3) Salbutamol induced a significant decrease in the maximum and the minimum inspiratory resistance but no significant change in the additional resistance only was observed at 12 cm H2O of PEEP (from 15.66+/-1.99 to 13.54+/-2.41, from 10.24+/-2.98 to 8.04+/-2.34, and from 5.42+/-3.41 to 5.50+/-3.58 cm H2O/l/sec, respectively). 4) The lung compliance did not change at the applied PEEP and salbutamol inhalation levels. CONCLUSIONS: The bronchodiator response would be different depending on the level of applied PEEP despite the increased respiratory resistance in patients with ARDS.
Albuterol ; Bronchodilator Agents ; Humans ; Inhalation* ; Lung ; Lung Compliance ; Male ; Positive-Pressure Respiration ; Respiratory Distress Syndrome, Adult* ; Respiratory Mechanics* ; Respiratory System

BACKGROUND: Sevoflurane has been used to provide an inhaled induction by using a vital capacity breath, which is fast and has few side effects. We compared the clinical effects of a vital capacity inhalation induction (VCII) with sevoflurane in patients of preoxygenation or air-breathing before anesthetic induction. METHODS: After IRB approval, patients were randomly assigned to receive preoxygenation (O2 group, 70 patients) or air breathing (Air group, 70 patients) via SIBI (Single Breath Induction) connectorTM before VCII with 8% sevoflurane in 75% N2O/O2 from primed circuit. The clinical characteristics were compared between two groups in respect to prolongation of breath holding after loss of consciousness (response to verbal command) and side effects (airway, hemodynamic, motor) during VCII. RESULTS: O2 group showed lower incidence (60.0% vs. 87.1%, P < 0.05) and shorter duration (27.1 s vs. 36.4 s, P < 0.05) in prolongation of breath holding than Air group. Otherwise, there were no significant differences in clinical effects between two groups. CONCLUSIONS: We found that preoxygenation reduces the incidence and duration of prolongation of breath holding during VCII with sevoflurane compared with air-ventilation before VCII. We suggest that the prolongation of breath holding might be related to Hering-Breuer response to maximal lung inflation during VCII.
Apnea ; Breath Holding ; Ethics Committees, Research ; Hemodynamics ; Humans ; Incidence ; Inflation, Economic ; Inhalation* ; Lung ; Respiration* ; Unconsciousness ; Ventilation* ; Vital Capacity*

BACKGROUND: Pressure support(PS) is becomimg a widely accepted method of mechanical ventilation either for total unloading or for partial unloading of respiratory muscle. The aim of the study was to find out if PS exert different effects on respiratory mechanics in synchronized intermittent mandatory ventilation(SIMV) and continuous positive airway pressure (CPAP) modes. METHODS: 5, 10 and 15 cm H2O of PS were sequentially applied in 14 patients(69+/-12 yrs, M:F=9:5) and respiratory rate (RR), tidal volume(VT), work of breathing(WOB), pressure time product(PTP), P(0.1), and T(1)/T(TOT) were measured using the CP-100 pulmonary monitor(Bicore, USA) in SIMV and CPAP modes respectively. RESULTS: 1) Common effects of PS on respiratory mechanics in both CPAP and SIMV modes As the level of PS was increased(0, 5, 10, 15 cm H2O), VT was increased in CPAP mode(0.28+/-0.09, 0.29+/-0.09, 0.31+/-0.11, 0.34+/-0.12 L, respectively, p=0.001), and also in SIMV mode(0.31+/-0.15, 0.32+/-0.09, 0.34+/-0.16, 0.36+/-0.15 L, respectively, p=0.0215). WOB was decreased in CPAP mode(1.40+/-1.02, 1.01+/-0.80, 0.80+/-0.85, 0.68+/-0.76 joule/L, respectively, p=0.0001), and in SIMV mode(0.97+/-0.77, 0.76+/-0.64, 0.57+/-0.55, 0.49+/-0.49 joule/L, respectively, p=0.0001). PTP was also decreased in CPAP mode(300+/-216, 217+/-165, 179+/-187, 122+/-114cm H2O * sec/min, respectively, p=0.0001), and in SIMV mode(218+/-181, 178+/-157, 130+/-147, 108+/-129cm H2O.sec/min, respectively, p=0.0017). 2) Different effects of PS on respiratory mechanics in CPAP and SIMV modes By application of PS (0, 5, 10, 15 cm H2O), RR was not changed in CPAP mode(27.9+/-6.7, 30.0+/-6.6, 26.1+/-9.1, 27.5+/-5.7/min, respectively, p=0.505), but it was decreased in SIMV mode (27.4+/-5.1, 27.8+/-6.5, 27.6+/-6.2, 25.1+/-5.4/min, respectively, p=0.0001). P(0.1) was reduced in CPAP mode(6.2+/-3.5, 4.8+/-2.8, 4.8+/-3.8, 3.9+/-2.5 cm H2O, respectively, p=0.0061), but not in SIMV mode(4.3+/-2.1, 4.0+/-1.8, 3.5+/-1.6, 3.5+/-1.9 cm H2O, respectively, p=0.054). T(1)/T(TOT) was decreased in CPAP mode(0.40+/-0.05, 0.39+/-0.04, 0.37+/-0.04, 0.35+/-0.04, respectively, p=0.0004), but not in SIMV mode(0.40+/-0.08, 0.35+/-0.07, 0.38+/-0.10, 0.37+/-0.10, respectively, p=0.287). 3) Comparison of respiratory mechanics between CPAP+PS and SIMV alone at same tidal volume. The tidal volume in CPAP+PS 10 cm H2O was comparable to that of SIMV alone. Under this condition, the RR(26.1+/-9.1, 27.4+/-5.1/min, respectively, p=0.516), WOB(0.80+/-0.85, 0.97+0.77 joule/L, respectively, p=0.485), P0.1(3.9+/-2.5, 4.3+/-2.1 cm H2O, respectively, p=0.481) were not different between the two methods, but PTP(179+/-187, 218+/-181 cmH2O.sec/min, respectively, p=0.042) and T(1)/T(TOT)(0.37+/-0.04, 0.40+/-0.08, respectively, p=0.026) were significantly lower in CPAP+PS than in SIMV alone. CONCLUSION: PS up to 15 cm H2O increased tidal volume, decreased work of breathing and pressure time product in both SIMV and CPAP modes. PS decreased respiration rate in SIMV mode but not in CPAP mode, while it reduced central respiratory drive(P(0.1)) and shortened duty cycle (T(1)/T(TOT)) in CPAP mode but not in SIMV mode. By 10 cm H2O of PS in CPAP mode, same tidal volume was obtained as in SIMV mode, and both methods were comparable in respect to RR, WOB, P(0.1), but CPAP+PS was superior in respect to the efficiency of the respiratory muscle work (PTP) and duty cycle(T(1)/T(TOT)).
Continuous Positive Airway Pressure ; Respiration, Artificial ; Respiratory Mechanics* ; Respiratory Muscles ; Respiratory Rate ; Tidal Volume ; Work of Breathing

BACKGROUND: ASV is a closed-loop ventilation system that guarantees a user-set minimum per-minute volume in intubated patients, whether paralyzed or with spontaneous breathing. Here, we tested the effects of ASV onrespiratory mechanics and compared them with volume-controlled ventilation (VCV). METHODS: Thirteen patients meeting the criteria for acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) were enrolled. All patients were paralyzed to eliminate spontaneous breathing. We started with VCV (VCV1), then used ASV followed by VCV modes (VCV2), maintaining minute volume as much as that of VCV1. RESULTS: During ASV, compared with VCV1, the inspiratory and expiratory tidal volumes and expiratory resistance increased. Conversely, the total respiratory rate and maximum pressure decreased. No changes in the arterial blood gases, heart rate, or mean systemic pressure were noted during the trial. CONCLUSIONS: In ALI/ARDS patients, although no differences were observed in the arterial blood gas analysis between the two modes, ASV provided better respiratory mechanics in terms of peak airway pressure and tidal volume than VCV.
Acute Lung Injury ; Blood Gas Analysis ; Gases ; Heart Rate ; Humans ; Lung ; Mechanics ; Respiration ; Respiratory Mechanics ; Respiratory Rate ; Tidal Volume ; Ventilation