OBJECTIVE: To find out the circuit pressure and flow at the trigger point by observing the characteristics of the inspiratory trigger waveform of the ventilator, confirm the intra-alveolar pressure as the index to reflect the effort of the trigger according to the working principle of the ventilator combined with the laws of respiratory mechanics, establish the related mathematical formula, and analyze its influencing factors and logical relationship. METHODS: A test-lung was connected to the circuit in a PB840 ventilator and a SV600 ventilator set in pressure-support mode. The positive end-expiratory pressure (PEEP) was set at 5 cmH₂O (1 cmH₂O ≈ 0.098 kPa), and the wall of test-lung was pulled outwards till an inspiratory was effectively triggered separately in slow, medium, fast power, and separately in flow-trigger mode (sensitivity V_Trig 3 L/min, 5 L/min) and pressure-trigger mode (sensitivity P_Trig 2 cmH₂O, 4 cmH₂O). By adjusting the scale of the curve in the ventilator display, the loop pressure and flow corresponding to the trigger point under different triggering conditions were observed. Taking intraalveolar pressure (Pa) as the research object, the Pa (called P_a-T) needed to reach the effective trigger time (T_T) was analyzed in the method of respiratory mechanics, and the amplitude of pressure change (ΔP) and the time span (ΔT) of Pa during triggering were also analyzed. RESULTS: (1) Corresponding relationship between pressure and flow rate at TT time: in flow-trigger mode, in slow, medium and fast trigger, the inhalation flow rate was V_Trig, and the circuit pressure was separately PEEP, PEEP-Pn, and PEEP-Pn' (Pn, Pn', being the decline range, and Pn' > Pn). In pressure-trigger mode, the inhalation flow rate was 1 L/min (PB840 ventilator) or 2 L/min (SV600 ventilator), and the circuit pressure was PEEP-P_Trig. (2) Calculation of P_a-T: in flow-trigger mode, in slow trigger: P_a-T = PEEP-V_TrigR (R represented airway resistance). In medium trigger: P_a-T = PEEP-Pn-V_TrigR. In fast trigger: P_a-T = PEEP-Pn'-V_TrigR. In pressure-trigger mode: P_a-T = PEEP-P_Trig-1R. (3) Calculation of ΔP: in flow trigger mode, in flow trigger: without intrinsic PEEP (PEEPi), ΔP = V_TrigR; with PEEPi, ΔP = PEEPi-PEEP+V_TrigR. In medium trigger: without PEEPi, ΔP = Pn+V_TrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn+V_TrigR. In fast trigger: without PEEPi, ΔP = Pn'+V_TrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn'+V_TrigR. In pressure-trigger mode, without PEEPi, ΔP = P_Trig+1R; with PEEPi, ΔP = PEEPi-PEEP+P_Trig+1R. (4) Pressure time change rate of Pa (F_P): F_P = ΔP/ΔT. In the same ΔP, the shorter the ΔT, the greater the triggering ability. Similarly, in the same ΔT, the bigger the ΔP, the greater the triggering ability. The FP could better reflect the patient's triggering ability. CONCLUSIONS The patient's inspiratory effort is reflected by three indicators: the minimum intrapulmonary pressure required for triggering, the pressure span of intrapulmonary pressure, and the pressure time change rate of intrapulmonary pressure, and formula is established, which can intuitively present the logical relationship between inspiratory trigger related factors and facilitate clinical analysis.
Humans ; Respiration, Artificial/methods* ; Positive-Pressure Respiration ; Lung ; Ventilators, Mechanical ; Respiratory Mechanics

OBJECTIVE: Robot-assisted radical prostatectomy (RARP) requires pneumoperitoneum (Pnp) and a steep head-down position that may disturb respiratory system compliance (C_rs) during surgery. Our aim was to compare the effects of different degrees of neuromuscular block (NMB) on C_rs with the same Pnp pressure during RARP. METHODS: One hundred patients who underwent RARP were enrolled and randomly allocated to a deep or moderate NMB group with 50 patients in each group. Rocuronium was administered to both groups: in the moderate NMB group to maintain 1-2 responses to train-of-four (TOF) stimulation; and in the deep NMB group to maintain no response to TOF stimulation and 1-2 responses in the post-tetanic count. Pnp pressure in both groups was 10 mmHg (1 mmHg=133.3 Pa). Peak inspiratory pressure (P_peak), mean pressure (P_mean), C_rs, and airway resistance (R_aw) were recorded after anesthesia induction and at 0, 30, 60, and 90 min of Pnp and post-Pnp. Surgical space conditions were evaluated after the procedure on a 4-point scale. RESULTS: Immediately after the Pnp, P_peak, P_mean, and R_aw significantly increased, while C_rs decreased and persisted during Pnp in both groups. The results did not significantly differ between the two groups at any of the time points. There was no difference in surgical space conditions between groups. Body movements occurred in 14 cases in the moderate NMB group and in one case in the deep NMB group, and all occurred during obturator lymphadenectomy. A significant difference between the two groups was observed. CONCLUSIONS Under the same Pnp pressure in RARP, deep and moderate NMBs resulted in similar changes in C_rs, and in other respiratory mechanics and surgical space conditions. However, deep NMB significantly reduced body movements during surgery.
Aged ; Humans ; Laparoscopy/methods* ; Lung Compliance/physiology* ; Male ; Neuromuscular Blockade ; Prostatectomy/methods* ; Respiratory Mechanics ; Robotic Surgical Procedures/methods* ; Rocuronium/pharmacology*

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

BACKGROUND: Firefighters are required to use self-contained breathing apparatus (SCBA), which impairs ventilatory mechanics. We hypothesized that firefighters have elevated arterial CO₂ when using SCBA. METHODS: Firefighters and controls performed a maximal exercise test on a cycle ergometer and two graded exercise tests (GXTs) at 25%, 50%, and 70% of their maximal aerobic power, once with a SCBA facemask and once with protective clothing and full SCBA. RESULTS: Respiratory rate increased more in controls than firefighters. Heart rate increased as a function of oxygen consumption (V.(O₂)) more in controls than firefighters. End-tidal CO₂ (ETCO₂) during the GXTs was not affected by work rate in either group for either condition but was higher in firefighters at all work rates in both GXTs. SCBA increased ETCO₂ in controls but not firefighters. CONCLUSIONS: The present study showed that when compared to controls, firefighters’ hypoventilate during a maximal test and GXT. The hypoventilation resulted in increased ETCO₂, and presumably increased arterial CO₂, during exertion. It is proposed that firefighters have altered CO₂ sensitivity due to voluntary hypoventilation during training and work. Confirmation of low CO₂ sensitivity and the consequence of this on performance and long-term health remain to be determined.
Exercise Test ; Firefighters* ; Heart Rate ; Humans ; Hypoventilation ; Mechanics ; Oxygen Consumption ; Protective Clothing ; Respiration* ; Respiratory Rate

The main stream of intraabdominal surgery has changed from laparotomy to laparoscopy, but anesthetic care for laparoscopic surgery is challenging for clinicians, because pneumoperitoneum might aggravate respiratory mechanics and arterial oxygenation. The authors reviewed the literature regarding ventilation strategies that reduce deleterious pulmonary physiologic changes during pneumoperitoneum for laparoscopic surgery under general anesthesia and make appropriate recommendations.
Anesthesia, General ; Laparoscopy* ; Laparotomy ; Oxygen ; Pneumoperitoneum ; Respiratory Mechanics ; Rivers ; Ventilation*

OBJECTIVETo compare the therapeutic effects of high-frequency oscillatory ventilation+pulmonary surfactant (HFOV+PS), conventional mechanical ventilation+pulmonary surfactant (CMV+PS), and conventional mechanical ventilation (CMV) alone for acute lung injury/acute respiratory distress syndrome (ALI/ARDS) in neonates.

METHODSA total of 136 neonates with ALI/ARDS were enrolled, among whom 73 had ALI and 63 had ARDS. They were divided into HFOV+PS group (n=45), CMV+PS group (n=53), and CMV group (n=38). The neonates in the first two groups were given PS at a dose of 70-100 mg/kg. The partial pressure of oxygen (PaO), partial pressure of carbon dioxide (PaCO), PaO/fraction of inspired oxygen (FiO), oxygenation index (OI), and respiratory index (RI) were measured at 0, 12, 24, 48, and 72 hours of mechanical ventilation.

RESULTSAt 12, 24, and 48 hours of mechanical ventilation, the HFOV+PS group had higher PaOand lower PaCOthan the CMV+PS and CMV groups (P<0.05). At 12, 24, 48, and 72 hours of mechanical ventilation, the HFOV+PS group had higher PaO/FiOand lower OI and RI than the CMV+PS and CMV groups (P<0.05). The HFOV+PS group had shorter durations of mechanical ventilation and oxygen use than the CMV+PS and CMV groups (P<0.05). There were no significant differences in the incidence rates of air leakage and intracranial hemorrhage and cure rate between the three groups.

CONCLUSIONSIn neonates with ALI/ARDS, HFOV combined with PS can improve pulmonary function more effectively and shorten the durations of mechanical ventilation and oxygen use compared with CMV+PS and CMV alone. It does not increase the incidence of complications.

Acute Lung Injury ; physiopathology ; therapy ; Combined Modality Therapy ; Female ; High-Frequency Ventilation ; Humans ; Infant, Newborn ; Male ; Pulmonary Surfactants ; therapeutic use ; Respiratory Distress Syndrome, Newborn ; physiopathology ; therapy ; Respiratory Mechanics

BACKGROUNDStress index at post-recruitment maneuvers could be a method of positive end-expiratory pressure (PEEP) titration in acute respiratory distress syndrome (ARDS) patients. However, airway pressure (Paw) stress index may not reflect lung mechanics in the patients with high chest wall elastance. This study was to evaluate the Pawstress index on lung mechanics and the correlation between Pawstress index and transpulmonary pressure (PL) stress index in acute respiratory failure (ARF) patients.

METHODSTwenty-four ARF patients with mechanical ventilation (MV) were consecutively recruited from July 2011 to April 2013 in Zhongda Hospital, Nanjing, China and Ospedale S. Giovanni Battista-Molinette Hospital, Turin, Italy. All patients underwent MV with volume control (tidal volume 6 ml/kg) for 20 min. PEEP was set according to the ARDSnet study protocol. The patients were divided into two groups according to the chest wall elastance/respiratory system elastance ratio. The high elastance group (H group, n = 14) had a ratio ≥30%, and the low elastance group (L group, n = 10) had a ratio <30%. Respiratory elastance, gas-exchange, Pawstress index, and PLstress index were measured. Student's t-test, regression analysis, and Bland-Altman analysis were used for statistical analysis.

RESULTSPneumonia was the major cause of respiratory failure (71.0%). Compared with the L group, PEEP was lower in the H group (5.7 ± 1.7 cmH2O vs. 9.0 ± 2.3 cmH2O, P < 0.01). Compared with the H group, lung elastance was higher (20.0 ± 7.8 cmH2O/L vs. 11.6 ± 3.6 cmH2O/L, P < 0.01), and stress was higher in the L group (7.0 ± 1.9 vs. 4.9 ± 1.9, P = 0.02). A linear relationship was observed between the Pawstress index and the PLstress index in H group (R2 = 0.56, P < 0.01) and L group (R2 = 0.85, P < 0.01).

CONCLUSIONIn the ARF patients with MV, Pawstress index can substitute for PLto guide ventilator settings.

TRIAL REGISTRATIONClinicalTrials.gov NCT02196870 (https://clinicaltrials.gov/ct2/show/NCT02196870).

Adult ; China ; Female ; Humans ; Lung ; physiology ; Lung Compliance ; physiology ; Male ; Middle Aged ; Positive-Pressure Respiration ; Regression Analysis ; Respiratory Distress Syndrome, Adult ; therapy ; Respiratory Mechanics ; Tidal Volume ; physiology

PURPOSE: As the National Health Insurance Service (NHIS) began to cover home oxygen therapy (HOT) services from 2006, it is expected that the new services have contributed to overall positive outcome of patients with chronic obstructive pulmonary disease (COPD). We examined whether the usage of HOT has helped slow down the progression of COPD. METHODS: We examined hospital claim data (N=10,798) of COPD inpatients who were treated in 2007~2012. We performed chi2 tests to analyze the differences in the changes to respiratory impairment grades. Multiple logistic regression analysis was used to identify factors that are associated with the use of HOT. Finally, a generalized linear mixed model was used to examine association between the HOT treatment and changes to respiratory impairment grades. RESULTS: A total of 2,490 patients had grade 1 respiratory impairment, and patients with grades 2 or 3 totaled 8,308. The OR for use of HOT was lower in grade 3 patients than others (OR: 0.33, 95% CI: 0.30~0.37). The maintenance/mitigation in all grades, those who used HOT had a higher OR than non-users (OR: 1.41, 95% CI: 1.23~1.61). CONCLUSION: HOT was effective in maintaining or mitigating the respiratory impairment in COPD patients.
Home Care Services ; Humans ; Inpatients ; Logistic Models ; Lung Diseases, Obstructive* ; National Health Programs ; Oxygen Inhalation Therapy ; Oxygen* ; Pulmonary Disease, Chronic Obstructive ; Respiratory Mechanics

BACKGROUND: Minimal invasive gynecologic surgery usually requires pneumoperitoneum and Trendelenburg positioning, which results in adverse effects on respiratory and hemodynamic parameters. The aim of this study was to investigate the effects of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) introduced sequentially in patients who underwent gynecological laparoscopy on respiratory mechanics, cardiovascular responses, and gas exchange. METHODS: Forty patients who were scheduled for gynecologic laparoscopic surgery were enrolled. Baseline ventilation of their lungs was performed with VCV with a tidal volume (TV) of 8 ml/kg ideal body weight (IBW). Forty minutes after pneumoperitoneum and Trendelenburg positioning, the ventilation mode was changed to PCV, and airway pressure was set to provide a TV of 8 ml/kg IBW without exceeding 35 cmH2O. Respiratory mechanics and hemodynamic and gas exchange parameters were recorded at 10 minutes after induction, 30 minutes after CO2 pneumoperitoneum and Trendelenburg positioning, 30 minutes after PCV, and 30 minutes after desufflation and supine position. RESULTS: After pneumoperitoneum and Trendelenburg positioning, there were significant increases in systolic blood pressure, diastolic blood pressure, central venous pressure, peak airway pressure (PAP), mean airway pressure (Pmean), whereas lung compliance and PaO2 significantly decreased. The decrease in PAP and increases of Pmean, lung compliance and PaO2 were observed during PCV compared with VCV (P < 0.05). There were no differences in hemodynamic parameters between VCV and PCV. CONCLUSIONS: Our results demonstrated that PCV may be an effective method of ventilation during gynecologic laparoscopy in terms of improved oxygenation and minimizing adverse respiratory mechanics.
Blood Pressure ; Central Venous Pressure ; Female ; Gynecologic Surgical Procedures ; Head-Down Tilt* ; Hemodynamics ; Humans ; Ideal Body Weight ; Laparoscopy* ; Lung ; Lung Compliance ; Oxygen ; Pneumoperitoneum ; Respiratory Mechanics ; Supine Position ; Tidal Volume ; Ventilation*

PURPOSE: Hypoxemia during one-lung ventilation (OLV) remains a serious problem, particularly in the supine position. We investigated the effects of alveolar recruitment (AR) and positive end-expiratory pressure (PEEP) on oxygenation during OLV in the supine position. MATERIALS AND METHODS: Ninety-nine patients were randomly allocated to one of the following three groups: a control group (ventilation with a tidal volume of 8 mL/kg), a PEEP group (the same ventilatory pattern with a PEEP of 8 cm H2O), or an AR group (an AR maneuver immediately before OLV followed by a PEEP of 8 cm H2O). The tidal volume was reduced to 6 mL/kg during OLV in all groups. Blood gas analyses, respiratory variables, and hemodynamic variables were recorded 15 min into TLV (TLVbaseline), 15 and 30 min after OLV (OLV15 and OLV30), and 10 min after re-establishing TLV (TLVend). RESULTS: Ultimately, 92 patients were analyzed. In the AR group, the arterial oxygen tension was higher at TLVend, and the physiologic dead space was lower at OLV15 and TLVend than in the control group. The mean airway pressure and dynamic lung compliance were higher in the PEEP and AR groups than in the control group at OLV15, OLV30, and TLVend. No significant differences in hemodynamic variables were found among the three groups throughout the study period. CONCLUSION: Recruitment of both lungs with subsequent PEEP before OLV improved arterial oxygenation and ventilatory efficiency during video-assisted thoracic surgery requiring OLV in the supine position.
Adult ; Aged ; Anoxia ; Female ; Humans ; Lung/physiopathology ; Lung Compliance/physiology ; Male ; Middle Aged ; One-Lung Ventilation/*methods ; Oxygen/*blood ; Positive-Pressure Respiration/*methods ; Pulmonary Alveoli/*physiology ; Pulmonary Gas Exchange ; Respiratory Mechanics/*physiology ; *Supine Position ; Thoracic Surgery, Video-Assisted ; Tidal Volume