2.1. Case 1
A 21-year-old man, a known case of a granulomatous disease involving lungs, was admitted on and off in ICU. Left lung was resected. His chest X-ray before intubation is presented in
Figure 1. Chest X ray of case 1 ,before intubation
Due to progressive dyspnea and respiratory distress, endotracheal intubation was followed by ventilator support (mode, volume controlled ventilation; tidal volume [V
t], 300 mL; respiratory rate [RR], 15/min; positive end expiratory pressure [PEEP], 5 cm H 2O; and fraction of inspired O 2 [FiO 2], 40%). With the above ventilator setting, peak airway pressure (P peak) was 32 cm H 2O and RR was 23/min.
To evaluate diaphragmatic work, Edi catheter was inserted that revealed minimum Edi of 0.1 and peak of 3.6 μv. Trigger flow brought down from 0.5 to 1 l/min and mandatory RR was reduced from 15/min to 9/min. It caused gradual increase of Edi peak up to 13 μv with peak airway pressure of 32 cm H
2O and total RR decreased to 14/min. According to these findings, NAVA level was selected as 2.2 and NAVA mode was started ( Figures 2 and 3). Finally, ideal NAVA was two with Edi peak of 9.8 μv, Vt of 250 to 290 mL, and Paw of 26 cm H 2O ( Figure 4). To compare pressure support ventilation (PSV) and synchronized intermittent mandatory ventilation (SIMV), a brief test was done (a potential benefit of NAVA preview). Neural timing mismatch and significant elevation of Edi were obvious in both modes ( Figures 5 and 6).
Figure 2. Monitoring of Volume Controlled Mode in Case 1
Figure 3. Setting of NAVA Mode in Case 1
Figure 4. Monitoring of NAVA Mode in Case 1
Figure 5. Edi Monitoring in SIMV Mode in Case 1
Figure 6. Edi Monitoring in PS/CPAP Mode in Case 1
2.2. Case 2
The second case was a 70-year-old man with history of repeated fainting followed by decreased level of consciousness since 30 days ago for which he was admitted to ICU. He had a history of pneumonia, sepsis, and repeated failure of weaning from mechanical ventilation. Tracheostomy was done about six months ago. As initial ventilator support in ICU, patient received positive pressure support (PEEP, 5 cm H
2o; PS, 5 cmH 2O; FiO 2, 40%; trigger flow, 5 l/min, and inspiratory cycle off, 30%). With this setting, RR was 29/min and V t was 370 to 400 mL. Considering notching on exhalation curve, 10% incremental raises added to inspiratory cycle off (from 30% to 60%). After cycle off adjustment, Edi catheter was inserted and appropriate placement confirmed by its waves on monitor. Then NAVA preview was selected ( Figure 7). According to above findings, NAVA level of one, trigger Edi of 0.5 μv, and inspiratory cycle off of 60% were selected. Then NAVA mode activated. Two hours later, the following characters were seen on the monitor:
Edi peak, 9.8 μv; minimum Edi, 0.6 μv; NAVA level, one; Ppeak, 16 cm H2O; RR, 36/min; and Vt 420 to 440 mL.
Few hours later, Edi peak reached 5.1 μv showing good patient's compatibility. VT was reduced by the patient to 300 mL with RR of 29/min and Ppeak decreased to 11 cm H2O. After two days T-tube trial was employed accompanied by continuous monitoring of Edi number (monitoring diaphragmatic effort when patient was not under ventilator support) (
Figure 7. NAVA mode preview in case 2
Figure 8. Proper Edi catheter positioning in case 2
2.3. Case 3
The third patient was a 65-year-old woman with history of fever, splenomegaly, visceral leishmaniasis, pancytopenia, and congestive heart failure who was on mechanical ventilation for 18 days. She was candidate for tracheostomy. Her chest X-ray is shown in
Figure 9. She was on SIMV plus pressure support ( Figure 10).
Figure 9. Chest X ray of case 3
Figure 10. Setting of SIMV mode in case 3
Edi catheter was inserted. NAVA preview showed the followings:
Edi peak, 13 μv; PEEP, 4 cm H
2O; P peak, 26 cm H2O; RR, 28/min; and Vt, 500 mL. Monitored parameters one hour later and following gradual adjustment of NAVA level up to 2.2, are shown in Figure 11.
Figure 11. Monitoring of NAVA mode in case 3 ( NAVA level :2.2)
Again, SIMV mode selected. Few hours later, an episode of increased heart rate (HR) (135/min), RR (40/min), and blood pressure occurred with simultaneous elevation in Edi peak (35 μv). Graphic analysis and patient assessment were performed. Suctioning of endotracheal tube led to removing a large amount of thin bloody secretions, which was followed by dramatic decrease in P
peak and increase in tidal volume, expiratory flow and Edi peak (the last as an early and reliable sign to suspect compromised airway in NAVA mode).
A chest X-ray taken in afternoon, revealed collapse and infiltration of Left lung. Fiberoptic bronchoscopy by intensivist was done. Large clot and bloody secretions were removed. Such episodes repeated, each time accompanied by significant increase in Edi peak and its reduction following suctioning (
Figures 12 and 13).
Figure 12. Monitoring of Edi in SIMV mode before fiberoptic bronchoscopy in case 3
Figure 13. Monitoring of Edi in SIMV mode after fiberoptic bronchoscopy in case 3
2.4. Case 4
The forth case was a 65-year-old man with history of lung cancer, left lung pneumonectomy, chronic obstructive pulmonary disease, pneumonia, opium use, and lower limb neuropathy. Tracheostomy tube was in place. SIMV (vol. controlled) plus pressure support was applied:
t, 400 mL; RR, 10/min; PEEP, 5 cm H 2O; pressure support (PS), 5 cm H 2O; and FiO 2, 50%; with following figures on monitor: V t, 250 mL; RR, 18/min; and Ppeak, 31 cm H 2O.
Edi catheter was inserted. Activation of NAVA revealed electrocardiography leakage effect resolved by increase of trigger Edi from 0.5 to 1.7 μv. Then NAVA level was down regulated from 3 to 1.7 cm H
2O/μv with Edi peak of 7.6 μv resulting in V t of 350 mL, RR of 22/min, and Ppeak of 19 cm H 2O.
Patient was suspected of sepsis and therefore, antibiotics started. Backed to Pressure regulated volume control (PRVC), airway pressure reached 39 cm H
2O. Suctioning of endotracheal tube was needed frequently for very large amounts of watery beige secretions. Gradual unresolved desaturation continued (oxygen saturation of near 60%) (early and reliable sign on NAVA mode to suspect problems in airway patency). Arterial pressure of CO 2 increased significantly, blood pressure decreased, and HR raised. Edi peak increased. Compliance continued to decline. There was no response to all therapeutic modalities including changes in ventilator setting and unfortunately, the patient died. 2.5. Case 5
This patient was a 76-year-old man, a known case of type 2 diabetes mellitus undergone radical cystectomy and had cardiac arrest in operating theatre. He was diagnosed with hypoxic brain damage, GCS of 5/10 with tracheostomy tube and abdominal wound infection; he was on mechanical ventilation (continuous positive airway pressure with PS) for nine days (
Figure 14. Setting of PS/CPAP mode in case 5
Edi peak was low on PSV. Noise in Edi tracing, caused by secretions, resolved after suctioning. Next day, patient developed tachypnea and fever. Edi peak increased from 4.7 to 10 μv and hence, NAVA level was increased from 1.0 to 1.4 cm H
2O/μv. Findings of monitoring after 24-hour running in NAVA is shown in Figure 15.
Figure 15. Monitoring of NAVA mode in case 5
The 24-hour trend showed relatively stable parameters within acceptable range (P
peak, P plateu) and minute ventilation. NAVA level brought down to 1.0 cm H 2O/μv when Edi peak reached 1.9 μv. He tolerated tracheostomy tube trial and weaning process (facilitated discontinuation of mechanical ventilation). 2.6. Case 6
A 50-year-old man with liver failure, on waiting list for liver transplant, was admitted to ICU for decreased level of consciousness and suspicious peritonitis.
He was intubated and ventilated with volume-controlled mode (RR, 16/min;
t 550 mL; PEEP, 5 cm H 2O; and FiO2, 50%). Measured parameters were as follows: RR, 19/min; V t, 520 mL; and P peak, 37 cm H 2O. NAVA preview showed gross mismatching ( Figure 16). PRVC mode was chosen that also revealed obvious asynchrony ( Figure 17).
Figure 16. Monitoring of Edi in volume controlled mode in case 6
Figure 17. Monitoring of Edi in PRVC mode in case 6
NAVA mode was selected and NAVA level was adjusted. We observed much more synchronized and smoother breaths after several minutes (a potential benefit of a plane NAVA preview) (
Figure 18. Monitoring of NAVA mode in case 6