This is due to the volume changes that take place in the pleural space, the air doubling or tripling in volume as normal atmospheric pressure is approached. If pneumothorax occurs in the multiplace chamber under pressure, it must be relieved surgically before decompression. In the monoplace chamber, a McSwain dart or other chest tube is made ready, the chamber is decompressed not taking longer than 1 min, and the chest tube inserted as the patient emerges.
The concomitant administration of doxorubicin or cisplatin as chemotherapeutic agents for cancer.
HBO and doxorubicin given together has caused death in rats (probably from cardiac toxicity), and cisplatin with HBO weakens the tensile strength of healing wounds in mice.
This blocks the production of superoxide dismutase, a protective antioxidant, and is also contraindicated in conjunction with HBO.
O2 in premature infants can cause retrolental fibroplasia, and therefore HBO is contraindicated. Full-term babies may be safely treated with HBO. Babies may require papoose restraints, and young children may need mild sedation.
*Concerns that HBO treatment of pregnant women might stimulate premature closure of the patent ductus in the fetus have been mitigated by research in the Soviet Union in which women in all stages of pregnancy, when treated with HBO, produced normal children. The chamber is used if there is an overriding need to treat a pregnant patient; eg, in carbon monoxide poisoning (where the fetus suffers much more than the mother) or gas gangrene.
History of spontaneous pneumothorax
Previous thoracic surgery
In severe emphysema with CO2 intoxication, removal of the hypoxic drive may cause respiratory arrest.
Upper respiratory infections may make it difficult for the patient to equalize pressure in the ears and sinuses; decongestants are indicated.
If the patient has a history of middle ear surgery for the treatment of otosclerosis, a wire or plastic strut might be displaced if the patient cannot equalize pressure in the ears; tympanostomy tubes may be needed.
Seizure disorders may increase susceptibility to O2 seizures, and additional premedication (eg, with diazepam) may be advisable.
Uncontrolled high fever may predispose to O2 seizures and should be reduced before placing the patient in the chamber.
Respiratory viral infections may tend to worsen with HBO. Such an infection is a reason to temporarily interrupt daily treatment of some chronic illnesses.
In congenital spherocytosis, RBCs are fragile, and high O2 partial pressures may cause severe hemolysis. It is felt by most that on the strength of a theoretical risk of hemolysis should the diver actually require HBOT spherocytosis probably does not constitute a ban to starting diving–providing the patient is not anemic.
Most anesthesiologists do not take any especial measures when anesthetising such patients. Eric Kindwall states that sperocytosis does not prevent such a patient receiving HBOT (non-diving) but should alert the operator to the possibility of haemolysis.
A history of optic neuritis, even if not active, has sometimes been associated with blindness following HBO treatment. Although rare, treatment should be halted immediately if the patient complains of a sudden change in vision.
This may occur, particularly when therapy is given at more than 2.4 atmospheres absolute (ATA). Some patients are idiosyncratically susceptible to high O2 partial pressures. Treatment is discontinuance of the O2. The incidence of seizure is low, being reported at 1.3/10,000 treatments.
Pulmonary O2 toxicity
This consists of substernal chest pain, cough, and patchy atelectasis, may occur but is not seen if treatment protocols are adhered to.
After 20 or 30 treatments in the chamber, some patients complain of numb fingers, usually in the ulnar distribution; but this sensation disappears within 4 to 6 wk after therapy.
may result from daily HBO but usually is a minor problem; treatment is with decongestants.
Lens refractive changes
It has been suggested, but not proved, that preexisting cataracts mature more rapidly with HBO.