Oops! Doctor blew my lungs out

Prepared by.........Staporn Maung-In, M.D.
CC : A preterm baby with respiratory distress
PI : A baby boy was born to 19 years old mother, G1P2 with uncertain date pregnancy. His mother did not have antenatal care and never been tested for any prenatal blood work. She refused of using street drugs and alcohol but admitted to having once induced abortion at 12 weeks gestation and again before delivery by vaginal suppository. She was in labor right after the latter induction. Neither history of fever nor membranes leakage prior to delivery was noted. Infant was born normal in labor room with Apgar score of 5 (1 minute),7 (5 minute). He was intubated for poor respiratory effort. His birth weight was 810 grams subsequently transferred to NICU.
Progression on arrival at NICU
He was immediately put on mechanical ventilator.
Vital signs: Temp 36.5, HR 153/min, RR manual bagging
Mean arterial blood pressure (MAP) 20 mmHg. Normal saline 2 doses of 10 cc/kg were given and brought up MAP to above 30 mmHg. His initial ventilator setting as following; PIP/PEEP 22/5 VR 60 /min Ti 0.33sec FiO2 0.95, CBC and Blood cultures were drawn, CXR was requested. : CBC: Hb 13 Hct 38% WBC 14,800 PMN 65% Plt 208,000
Problems:
  Preterm ELBW (Extremely low birth weight)
Respiratory distress
Brief low blood pressure and well responded to fluid
Resuscitation
Noninvasive attempted abortion
Discussion 1:
  What is the most likely diagnosis?
What are the differential diagnoses?
What are the initial treatments?
The most likely diagnosis is severe RDS according to the following supportive information;
a) 80% of incidence in preterm GA<28 weeks or BW 751-1000g. Antenatal steroids decrease both incidence and severity but this baby was not given.
b) onset of symptoms before 6 hours of age.
c) Typical roentgenographic features which are diffuse reticulogranular pattern in both lung fields(symmetrical) with superimposed air bronchogram.

However the definite diagnosis can be established by biochemical documentation which is not practical in postnatal period so the clinician should be keeping in mind with the following differential diagnosis.
Congenital peumonia: The clinical symptoms on respiratory aspect and roentgenographic findings can mimic RDS especially for GBS infection .The diagnosis can be made for the first priority if there are the evidence of refractory cardiovascular instability and abnormal CBC those of which were not found in this baby.
Pulmonary hemorrhage: can present with the same clinical symptoms and x-ray findings but can be ruled out in this baby since there was no blood ever obtained from endotracheal tube.
Pulmonary hypoplasia: result from abnormal regulation of lung growth and development. These anomalies associate with prolonged oligohydramnios. However there was no document of prolonged rupture of membranes in this baby.
Treatment of RDS
Therapy of severe RDS comprises the careful application of general supportive measures by specific means of controlling and/or assisting ventilation with surfactant supplementation is the treatment of choice and should be given within 2 hours of age. Unfortunately, there was surfactant shortening during the days of this baby was born therefore he underwent on the old fashion conservative treatment.
On the next day of progression:
  Ventilator setting : PIP/PEEP 24/5 VR 50/min Ti 0.35 Fio2 1.0
CBG : pH 7.32 PCO2 53 HCO3 23 BE - 3.5
Follow up CXR
Discussion 2
  What was happening?
What are your actions?
There was an abnormal air collection in this baby's lungs so-called " Pulmonary air leak syndromes"
Air leak syndromes encompass a wide-spectrum of diseases including
  Pneumothorax (figure 1)
Pneumomediastinum (figure 2)
Pulmonary Interstitial Emphysema (figure 3)
Pneumopericardium
Pneumoperitonium
Figure 1
Figure 2
Figure 3
The syndromes are one of the most common complications in ventilated infants. The mechanism of air leak begins with positive intra-alveolar inflation and causes alveolar rupture. The type of air leak syndromes will depend on the location where the escaping air destined.
From CXR on the next day of progression in this baby showed that he was experiencing both pneumothorax and pulmonary interstitial emphysema. Immediate needle decompression follow by chest tube insertion are considered to be the most proper action especially the baby encountering with cardiopulmonary compromise from tension pnuemothorax. These procedures will remove the air collection from pleural cavity. However, these actions are not helpful to get rid of the air leak from PIE.
Pulmonary Interstitial Emphysema (PIE)
Collection of gases outside of normal air passage which is inside the connective tissue of the peribronchovascular sheaths, interlobular septa and visceral pleura results in compressing adjacent functional lung tissue, vascular structures and impedance of oxygenation, ventilation as well as blood pressure.Roentgenography: There are two basic radiographic appearnce
1. Linear radiolucencies; coarse and nonbranching, 3-8 mm, and vary in width but rarely exceed 2 mm
2. Cystlike radiolucencies; 1-4 mm, though generally round ,they may appear oval or slightly lobulated
PIE VS RDS (Chest X-ray findings)
PIE
RDS
Coarse radiolucencies appear in the lung periphery or when the lucencies do not branch in a pattern consistent with the normal branchial tree Long smooth , branching ,linear radiolucencies decrease in caliber from the hilum and frequently disappear at the lung periphery
Discussion 3: How do you ventilate this baby?
It is crucial to decrease the positive pressure use as soon as possible .On the other hand, try to maintain the similar Mean Airway Pressure(MAP) close to the same level in preventing oxygenation jeopardy by increase mechanical ventilator rate (VR). Basically, MAP in conventional mechanical ventilator depends on PIP, PEEP, Ti, Flow and VR and the least harmful parameter to cause barotrauma is VR. Therefore, the most proper technique when using conventional ventilator in PIE is " Fast rate, low pressure" In practical, not only PIP is decreased but also PEEP because in fast rate ventilation might cause inadvertent PEEP and develop more air trapped in the lungs.
Another promising option for PIE treatment is High Frequency Ventilator (HFV).
The principles of HFV is to deliver tidal volume equal to or less than anatomical dead space with active both inspiration and expiration phrase on top the inflated lungs when the recruitment of lung volume is achieved by distending pressure (CPAP= Continuous positive airway pressure). This allows the primary goals of ventilation, oxygenation without the costs of pressure induced lung injury. (figure4: Pressure wave form during HFV)
Type of HFV
>>High Frequency Oscillatory Ventilation (HFOV)
(picture1 : Sensomedic) (Picture2 : SLE) (picture3 : Babylog)
>>High Frequency Jet Ventilation
Need special endotrachial tube, not available in Thailand
>>High Frequency Flow Interupted ventilation
- Infant Star (out of date)
Picture 1
Picture 2
Picture 3
Parameters in Conventional VS HFV
Conventional
HFV
For Oxygenation : FiO2 &MAP
MAP; PIP, PEEP, Ti, VR, Flow
For Ventilation : Minute ventilation
Minute ventilation; Tidal volume, VR
(when tidal volume = PIP-PEEP)

For Oxygenation : FiO2 and MAP
MAP; CPAP( or PEEP)
For ventilation : Amplitude and frequency
Indications for HFV
1. Neonatal Respiratory Distress Syndrome
2. Persistent Pulmonary Hypertension
3. Neonatal Meconium Aspiration Syndrome
4. Congenital Diaphragmatic Hernia
5. Neonatal lung hypoplasia
6. Neonatal Air leak Syndrome with PIE
7. Pediatric ARDS
Contraindication
1. Obstructive Airway Disease -asthma, RDS, emphysema, bronchiolitis
2. Cardiovascular system Dysfunction
3. Shock
HFV : Start
a) For diffuse homogenous lung diseases
Goal; lung expansion less barotruama
- begin with MAP 2 to 5 mbar above of conventional ventilation
- then increase MAP until PaO2 rises by 20 to 30 mmHg
- after 30 min: X-ray : 8-9 rib level
- HFV amplitude 100% (watch thorax vibration)
- HFV frequency 10Hz
b) For inhomogeneous lung diseases
Goal; improved oxygenation and ventilation at minimum MAP
Risk; partial over expansion
- begin with MAP like or below that of conventional ventilation
- HFV frequency low e.g. 7 Hz
- HFV amplitude 100% (watch thorax vibration)
- Increase MAP until PaO2 slightly rises if fails to improve return to conventional ventilation
c) For air leaks
Goal; improved oxygenation and ventilation at minimum MAP
Accept lower PaO2 and higher PaCO2
- Begin with MAP like or below that of conventional ventilation
- HFV frequency low, for example 7Hz
- HFV amplitude 100% (watch thorax vibration)
- Reduce pressure prior to Fio2
- Continue HFV for 24 to 48 hrs after improvement
HFV : Weaning
1. Reduce FiO2 to 0.3-0.5
2. Reduce MAP by 1 to 2 mbar per hour until (8) to 9 mbar then increase IMV rate
3. Reduce amplitude
4. Continue ventilation with IMV/SIMV and weaning
5. Extubation from HFV is also possible if respiratory activity is sufficient
Clinical progression (Wrap up!)
HFV was initiated in this baby one day after he developed Pneumothorax and PIE. There was an improvement on ventilation (PaCO2 could be maintained at below 55 mmHg) but oxygenation. He required FiO2 at a maximum of 100% even though MAP had been increased to the satisfactory level (chest X-ray at rib 9). (CXR 3) Dexamethasone was given as a heroic purpose on his significant lung problem however he did not make any bit of respond moreover he was witnessed of seizure with the head ultrasound on the next day showed IVH grade 3 bilaterally. Given all these input, he was considered to be in grave prognosis and the non-aggressive treatment was brought up. He was finally hypotensive and clinically septic on the eight day of life followed by cardiac arrest without CPR attempted.
CXR 3 shows bilateral pneumothorax and PIE with ICD
Discussion 4: Is HFV safe for preterm infants?
From the Cochrane Database of Systematic Review in rescue high frequency oscillatory VS conventional ventilation in preterm infants with pulmonary dysfunction, they found that for every 6 infants treated with rescue HFOV rather than CV 1 case of pulmonary air leak of any type would be prevented and 1 case of IVH of any grade would be caused however there was stronger but non-significant trend towards an increase in grade 3 or 4 IVH.
Suggested readings:
1. Bhuta T, Clark RH, Henderson-Smart DJ. Rescue high frequency oscillatory ventilation VS conventional ventilation for preterm infants with pulmonary dysfunction.(Cochrane Review). In : The Cochrane Library, Issue 4 2002.Oxford
2. Stachow R, Dragerwerk AG. High frequency ventilation ; Basics and Practical application; Dragger, Germany (pdf.file)

Final Diagnosis :Preterm baby with pulmonary interstitial emphysema

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